United States
                     Environmental Protection
                     Agency
Washington, D.C. 20460
September 1982
   Rsgicn II! Library
Environmental Protection
1

I
                      Chesapeake Bay  Program
                      Technical Studies: A Synthesis
        ^ !>-.;. jr:.<-'.til Pichriion Agency
       - "on h- Si-'C-r-sation Resource
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       f.Uv.-pi^PA  IS107

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FOREWORD

   In recent years the well-being of Chesapeake
Bay and its tributaries has .been stressed by
activities of the region's growing population.
Concern for this national resource prompted
Congress in 1976 to direct the U.S. Environ-
mental Protection Agency (EPA) to conduct an
intensive five-year study of the Bay's resources
and water quality, and develop related management
strategies.  To address concerns of Congress, this
study, known as the Chesapeake Bay Program (CBP),
focused research on three principal problems in
the Bay—the presence of toxic substances, nutrient
enrichment, and the disappearance of valuable
submerged aquatic vegetation.  In addition to
evaluating the severity of these problems and what
they may indicate about the Bay's water quality,
the CBP was directed to review current mechanisms
of pollution control and suggest management
strategies.

   This document is the second of the Program's
four final reports.  It is intended to share the
results and significance of the Chesapeake Bay
Program's technical studies with managers,
decision-makers, and citizens.  The report
integrates, or synthesizes, results of the
many technical studies that have addressed
Congress' concerns.  This integration by key
scientists in the three problem areas centered
around a set of specific questions relevant to
managers and decision-makers of the Bay region,
and were developed by Program staff, and
State and Federal environmental managers.  In
attempting to answer these questions with the
best scientific information, the authors of
the papers were not confined only to infor-
mation derived from the projects.  They drew
on the research literature, personal communi-
cations, and their own rich knowledge of the
Bay's ecology, as well as their extensive
interaction with peer scientists.  The
conclusions of each paper, although based
primarily on results from CBP research
projects, reflect a mixture of scientific
results and the best judgment of scientists
responding to management questions.

   The authors and contributors hope that
this report will further knowledge of changes
taking place in the Bay, so that together, we
can manage Chesapeake Bay effectively.
Tudor T. Davies
Director
Chesapeake Bay Prog
   e
Thomas B. DeMoss
Deputy Director
Chesapeake Bay Progfcn

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                                                       U "• E'V.jir.i'."'^! Protection
                                                       K >r, IL in'C'.:. uiion Resource
                                                       O: '•:•; (1. "'•"')
                                                       8ซi  r\-c .-'• * t' -/-'.t
                                                       til' :",$., .ui c. .itai
                                    SUMMARY             Philadelphia, PA  19107  '
.
    As part of the five year study plan  for  the EPA Chesapeake  Bay Program
(CBP) , EPA staff, officials from Maryland  and Virginia,  and  citizens
identified 10 areas as foremost water quality problems of  the Bay,  and
agreed upon three as most critical for intensive  investigation:   Nutrient
Enrichment, Toxic Substances, and the Decline of  Submerged Aquatic
Vegetation.  The EPA then initiated research to study  intensively these
three problem areas.  The following summary  describes  the  findings from
research projects funded by the Chesapeake Bay Program in  those  three
technical areas.  Two other CBP reports, "Characterization of Chesapeake
Bay" and "Management Strategies for Chesapeake Bay" assess Bay-wide
conditions and suggest management strategies.
NUTRIENT ENRICHMENT


    Nutrients, both phosphorous  (P) and nitrogen  (N),  are  crucial  to  Bay
life.  Nutrient enrichment occurs when excessive  additions of  nitrogen and
phosphorous compounds enter the  water.  Enrichment  can lead to undesirable
consequences such as phytoplankton blooms,  depletion of oxygen,  and changes

in kinds of fish present.  When  an estuary,  such  as Chesapeake Bay, becomes
nutrient-enriched, algae can thrive and accumulate  in  the  water  column.
Their presence decreases light transparency, and, when they degrade,  they
use up dissolved oxygen that other plants and animals  need.
    Nutrient enrichment in Chesapeake Bay is evaluated by  measuring a
number of related factors including nutrient concentration and oxygen

levels in the water, amounts of  chlorophyll ji,  (a green pigment  found in
most algae), and transparency of the water  (Secchi  depth).   Historical
records of these measurements were gathered  and analyzed during  the Bay
Program to look at trends in nutrients over  the past 20 years.   During this
time, nutrient concentrations have increased, causing  enrichment in some
areas.  Figure 1 shows areas of  the Bay that are  enriched.   These  include:
most of the western tributaries  such as the  Patuxent,  Potomac,  and James;
the northern and central main Bay; and some  Eastern shore  tributaries
including the Chester and Choptank.  These  areas  show  high levels  of
nutrients and chlorophyll ฃ, and reduced light  transparency.   The  lower
Bay, however, has remained relatively unaffected.   An  analysis that relates
these trends to the health of fisheries in  the  Bay  will be presented  in  the
CBP report entitled "Characterization of Chesapeake Bay."


Sources of Nutrients


Phosphorus (P) and nitrogen (N)  enter the Bay from  several  major sources or
pathways:   atmosphere, rivers, point sources, and sediments.   The  estimated
percentage that each of the sources contributes to  the Bay during  a year is
shown in Table 1.

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         Chesapeake - Bay
                Region
                                                     Moderately Enriched  I

                                                     Heavily Enriched
Figure  1.   Map showing portions of Chesapeake Bay that are moderately
           or heavily enriched according to the  criteria of Heinle et al.  (1980)
                                    11
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TABLE 1.  PERCENTAGE OF ANNUAL NUTRIENT LOADINGS FROM VARIOUS SOURCES(D
Constituent
Atmospheric
  Sources
  Riverine
  Sources
      Point
     Sources
         Sediment
          Sources
Total nitrogen
Total phosphorus
    13
     5
     56
     35
        22
        35
              9
             25
(l^Definition of Terms
    Atmosphere:  aerial input that directly lands on fluvial or tidal  waters.
    Riverine: mass loadings of nutrients to Bay from above the head of  tide.
    Point sources: nutient loads from industry and municipalites  below  the
     head of tide.
    Sediment sources:   nutrient releases or loads from the bottom sediment
     of Chesapeake Bay.

Riverine Sources—
    Riverine sources are a major contributor of N and P to the Bay;
approximately 56 percent of the total nitrogen loading comes from these
sources.  This loading ranges from 39 percent in summer to 64 percent in
spring when river flows are highest.  Riverine source loads for P are about
35 percent of the total annual input and range from 12 percent in summer to
57 percent in spring.
    Of all the river sources, the Susquehanna River is the major
contributor of P and N, as shown in Table 2.  The Susquehanna River has by
far the largest drainage area and annual flow discharge among the river
sources.  This at least partly accounts for the relatively higher
contribution of N and P from the Susquehanna.  This river carries about 70
percent of the total nitrogen and 56 percent of the total phosphorus
delivered to the Bay each year from riverine sources.  Most of these  loads
enter during the winter and spring.
    The Susquehanna produces only about 40 percent of annual sediment load,
because the particulate matter is trapped in reservoirs located on the
lower 60 miles of the main stem of the river.  Only a large flow, above
400,000 cubic feet per second (cfs), will transport sediment through  the
reservoir and deliver them to the Bay.  Such flows occur only one percent
of the t ime .

TABLE 2.  ESTIMATED PERCENTAGE OF TOTAL ANNUAL RIVERINE NUTRIENT
          AND SEDIMENT LOADS FROM CHESAPEAKE BAY TRIBUTARIES
Constituent
  Susquehanna
Potomac
James
Other Tributaries
Total nitrogen
Total phosphorus
Sediment
70
56
40
19
22
33
6
16
16
5
6
11
                                111

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    Major land uses in the Chesapeake Bay basin and their estimated
contribution to riverine nutrient loads are shown in Table 3.

TABLE 3.  MAJOR LAND-USES ABOVE THE FALL LINE AND THEIR ESTIMATED
          CONTRIBUTION TO RIVERINE NUTRIENT LOADS
    Land Use
Percent In Basin    Percent of Riverine Nutrient Loads

Cropland
Pasture
Forest
Urban

15-20
8-12
60-65
3- 5
TN
45-70
4-13
9-30
2-12
TP
60-85
3- 8
4- 8
4-12

Riverine loadings can vary considerably among land uses.  The highest
riverine loading rates come from cropland, and lowest from forest sites.
Agricultural land appears to produce the largest fraction of the riverine
loads by at least a factor of three for both nitrogen and phosphorus, due
to the high unit-area loadings and large percentages of land used for
agriculture in this area.  The CBP's Bay-wide watershed model has estimated
the relative contributions of nutrients from all nonpoint sources.  These
results will be presented in the CBP report "Management Strategies for
Chesapeake Bay."

Point Sources--
    Most of the remaining nutrients in the Bay are contributed from point
sources, such as sewage treatment plants and industries lying below the
head of tide (see Table 1).  These point sources account for about 22
percent of total nitrogen load and some 35 percent of total  phosphorus
input.  The percentage of nutrient load from point sources ranges from 15
in spring to 29 in fall,  while phosphorus percentages range  from 59 percent
in fall to 21 percent in summer.
    Other sources include the atmosphere and bottom sediments.   Atmospheric
contribution constitutes  about 13 percent of the total nitrogen and five
percent of the annual phosphorus input, while bottom sediments make up
about 10 percent of the annual nitrogen and 25 percent of the annual
phosphorous load.

Seasonal Nature of Nutrient Loads

    The largest portion of the annual nitrogen load enters the Bay during
the winter and spring, while the highest portion of the annual phosphorus
load enters during the spring and summer.  These nutrient inputs support
increases in algal standing crop.  Since the relative abundance of nitrogen
and phosphorus changes from spring to summer, so the potential limiting
nutrient for the algal standing crop may change.
    The limiting nutrient changes during the year in Chesapeake Bay as a
result of three prominent events.  The first is the substantial nitrate
input with a spring runoff from the Susquehanna River.   The  second event
                                iv
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occurs during mid-summer when very low oxygen concentrations in deeper Bay
water permit release of phosphate from Bay sediments and accumulation of
both phosphate and ammonium in the deep water.  The third event is the fall
nitrite maximum observed in both mid-Bay and in the lower Potomac River
estuary.  Thus, peak nitrogen availability occurs in spring, while peak
phosphorus availability occurs in summer.
    Consequently, phosphorus concentration is generally higher in deep
water during summer.  Addition of phosphorus during the other seasons could
cause the standing crop of phytoplankton to increase, if nitrogen is
available.  Thus, phosphorous appears to be the biomass limiting, or
regulating, nutrient for spring, fall, and winter.  Nitrogen, however, is
at  its lowest levels and could be limiting in summer; additions at this
time may cause phytoplankton to grow if phosphorous is available from the
deep water due to recycling processes.  An awareness of the response of
phytoplankton to available nutrients is important when considering effects
on  Bay resources and how to control input.  Because phytoplankton form the
base of the Bay's food web, increases in their populations will create more
food for other Bay inhabitants, to a point.  Beyond this point (we feel
that Figure 1 indicates what areas of the Bay are at this point) growth of
phytoplankton can be detrimental to the Bay's water quality and its
resources.

Management Implications

    Management strategies to address the problem areas must take into
account the seasonal patterns of nitrogen and phosphorous we have described
and the degree to which each contributing source may be controlled, its
relative costs to achieve this control, and trade-offs between point and
nonpoint sources.  The possible management strategies will be shown in the
CBP report "Management Strategies for Chesapeake Bay".
TOXIC SUBSTANCES

    Toxic substances constitute the second of three critical areas studied
under the CBP.  The research focused on determining the status of both
metals and organic compounds in Chesapeake Bay, including their
concentration in the water column, bed sediments, suspended sediments, and
in some bivalves.  Sources of metals and organic compounds were also
investigated.  A limited amount of research was performed on assessing the
toxicity of point source effluents and Bay sediments.

    Toxic substances are usually defined as chemicals or chemical compounds
that can harm living plants and animals, including humans, or impair
physical or chemical processes.  The two general classes of toxic
substances studied were inorganic and organic compounds.  Inorganic
materials are metals such as arsenic (As), cadmium (Cd), chromium (Cr),
copper (Cu) , and zinc (Zn).  Many of the organic compounds are products  of
human activities and include pesticides, phthalate esters, polynuclear
aromatic hydrocarbons (PNA's),  and other chlorinated hydrocarbon compounds
(PCBs, etc.).
                                v

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                                                                                    I
                                                                                    I
Current Status

    The highest concentrations of metals in Bay sediment occur in Baltimore         I
Harbor and the Elizabeth River.  In the main Bay, the highest metals
concentrations in sediment occur in the northern Bay and particularly near          „
the western shore where cadmium, cobalt, copper, manganese, nickel, lead,           •
and zinc are enriched (elevated relative to natural levels) two to eight            ™
times above natural levels from the Susquehanna Flats to Baltimore Harbor
region.  At least half of the metal loads for chromium,  cadmium,  copper,            M
and lead orginate from human sources.                                                |
    Metals tend to partition with fine particulate matter such as detritus
and silt.  Consequently, highest concentrations of metals in suspended              _
material (ug of metal per gram suspended material) occur in near-surface            •
water in the central Bay where organic matter tends to be high.  Cadmium,           ^
lead, copper, and zinc display the highest concentrations.  Because this
enriched zone is an area of high organic activity where organisms respire,          •
reproduce, and grow, metals are available for uptake by phytoplankton and           ฃ
marine organisms.  Once in the plankton, the metals can be passed through
the food chain.                                                                     ป
    Like metals, organic compounds tend to cling to fine material that is           •
suspended in the water.  When this material settles, organic compounds will         •
accumulate on the Bay floor.  Concentrations of organic compounds in bottom
sediments are highest in the northern  Bay. They exhibit similar trends to           •
metal enrichment, with highest concentrations occurring in the vicinity of          •
Baltimore Harbor.  Concentrations tend to increase up the Bay from the
Potomac River mouth toward the Patapsco River.   North of the Patapsco               •
River, elevated concentrations are found to exist to the Susquehanna River          •
mouth.  It appears that many of these  organic compounds may have  entered
from the Susquahanna River.  In the southern Bay, the highest
concentrations of organic compounds are found where the river estuaries             •
enter the main Bay.                                                                 •
    The sediments of the Patapsco River estuary show the highest
concentrations of organic compounds.  Highest levels occur near source              •
locations.  These sediments appear to  be largely trapped within Baltimore           |
Harbor.
    Oysters collected from around the  Bay and oyster-tissue extracts were           •
examined for organic compound concentrations.  These bivalves did                   •
accumulate some toxic compounds.  There were 42 compounds detected whose
individual concentrations exceeded 50  parts per billion.  The mouth of the
James River had 29 percent, and Baltimore Harbor 24 percent of these 42             B
compounds.                                                                          •

Sources
                                                                                    I
    Riverine sources above the fall line, point sources below fall line,
and atmospheric sources, contribute most of the metals to Chesapeake Bay  as
 hown in Table 4.  Of the three major rivers in which metal concentrations           •
were measured (Susquahanna, Potomac, and James), the Susquahanna                     B
contributes the greatest amount of metals.  These river loads include
municipal, nonpoint, and industrial sources above the fall lines.  The
annual loadings of various metals of the three rivers are compared in Table
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5.  The concentration levels of metals in the three rivers are similar,
however, the Susquehanna has greater loadings because of its higher flow.
The Susquehanna River is also very significant to quality of water in the
Bay proper, because the loads it delivers enter the Bay directly and are
not trapped in the sub-estuaries like those from the James and Potomac.
    Industrial and municipal input below the fall line are a major
contributor of metals to the Bay (Table 4).  For example, industrial loads
account for 66 percent of total cadmium load.  Municipal POTWs account for
19 percent of total chromium load.  The distribution of these loadings for
POTWs and industries below the fall line (Pennsylvania counties, thus, not
included) by counties is shown in Table 6.  The inputs of Cd, Cr, Cu, Fe,
and Zn in Baltimore County and Baltimore City far exceed those from other
counties.  Substantial inputs from POTWs are also noted for Cr, Fe, and Zn
in Richmond City; for Cr, Fe, and Zn from Norfolk City, and for Cr, Fe, and
Zn at Hopewell City.  The industrial load exceeds POTW loadings by two
times.  Loadings from urban runoff and atmospheric sources are also
significant for several metals as shown in Table 4.
    Results from the CBP show that sources of organic compounds to the Bay
are human-related.  In particular, organic compounds in northern-Bay
sediments are probably from the Susquehanna River, and possibly some from
the Patapsco.  Concentrations of organic compounds in the Bay should be
highest in areas of sedimentation near industrial regions and high
population areas.  The CBP is further investigating sources of toxic
substances and will present the results in CBP report "Management
Strategies for Chesapeake Bay".

TABLE 4.  LOADINGS OF METALS FROM THE MAJOR SOURCES AND PATHWAYS TO
          CHESAPEAKE BAY (VALUES IN METRIC TONS/YEAR)

Source
Industry
Municipal
Wastewater
Atmospheric
Urban Runoff
Rivers
Shore Erosion
Cr
1
200 (19)
200 (19)
	
10 ( 1)
551 (53)
83 ( 8)
Cd
178
6
3
7
75
1
(66)
( 2)
( 1)
( 2)
(28)
( 1)
Pb
155
68
34
111
307
28
(22)
(10)
( 5)
(16)
(43)
( 4)
Cu
190
99
28
9
517
29
(22)
(12)
( 3)
( 1)
(59)
( 3)
Zn
167
284
825
63
1444
96
( 6)
(10)
(29)
( 2)
(50)
( 3)
Fe
2,006
625
87
977
199,682
57,200

( 1)
( 1)
( 1)
( 1)
(77)
(22)

^-Values in parenthesis represent percent of total loading
                               vii

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     In  certain  areas,  present levels of toxic substances could threaten the
 health  of  organisms.   Bioassay tests on bottom sediments from the Bay show
 that  sediments  from  the Patapsco and Elizabeth Rivers and northern Bay are
 potentially more  toxic than elsewhere.  This toxicity is probably produced
 by a  combination  of high metal content and large loads of organic
 compounds.  These tests on bottom sediments found concentrations that cause
 mortality.  The highest mortalities occurred on samples from the upper
 reach of the Patapsco  and Elizabeth Rivers, and the northern Bay.  Tests
 performed  on effluent  from industrial plants around the Bay area revealed
 that up to half of effluents sampled killed test fish and invertebrates.
 The significance of these results and their relationship to Bay resources
 will be discussed in CBP report "Characterization of Chesapeake Bay".


 TABLE 5.   ESTIMATED AVERAGE ANNUAL LOADINGS FOR VARIOUS METALS FROM THE
           MAJOR TRIBUTARIES OF THE CHESAPEAKE BAY FOR 1979-1980 PERIOD*
           (VALUES IN METRIC TONS/YEAR) (FROM LANG AND GRASON 1980)

Parameter Susquehanna
@ Conowingo Dam
%
Al-T
As-T
Cd-T
Co-T
Cr-T
Cu-T
Fe-D
Fe-S
Mn-T
Ni-T
Pb-T
Zn-T
161,618
82
65
59
383
390
1,844
192,422
14,469
229
174
837
69
71
87
40
70
75
57
65
77
57
57
58
Po tomac
@ Chain Bridge
%
37,626
13
4
39
105
86
839
76,227
1,933
109
102
322
16
12
5
27
19
17
26
26
10
27
33
22
James
@ Cartersville , Va.
%
33,884
20
6
48
63
41
567
27,783
2,327
64
31
285
15
17
8
33
11
8
17
9
13
16
10
20
Totals
233,128
115
75
146
551
517
3,250
296,432
18,729
402
307
1,444

*Values listed represent the mean of 1979 and 1980 calender year loadings,
(Note:  Percentages above-are approximate numbers)


D - Dissolved
S - Suspended
T - Total
Management Implications


    Managing toxic substances requires a priority, or ranking,  framework
that evaluates toxic material for its greatest potential to affect human
and environmental health.  As with nutrients,  areas where environmental
quality is severely degraded should be established, based on all available
environmental quality data (sediment, biota, and water) and should be top
                                viii
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                                                                                    I
 priority  for  cleanup.  The  priority areas will be examined in the CBP               •
 report  "Characterization of Chesapeake Bay".
SUBMERGED AQUATIC VEGETATION

Pattern of Decline
                                                                                    I

                                                                                    I
     Submerged aquatic vegetation (SAV) has, in the past, been very abundant
 throughout Chesapeake Bay.  Our current evidence indicates a pattern of SAV         H
 decline  that includes all species in all sections of the Bay.  A marked             |
 decline  has occurred throughout the estuary since the mid-1960's. Present
 abundance of Bay  grasses is at its lowest level in recorded history.                K
     Historical analysis of sediments on Bay-grass seeds and pollen                  •
 indicates a continuous presence of Bay grasses from the 17th century.  In
 the  last 50 years, there have been several distinct periods and patterns
 where Bay grasses have undergone major changes.  An outbreak of eelgrass            B
 wasting  disease occurred in 1930 's and reduced SAV populations, as did a            B
 watermilfoil outbreak in the late 1950 's and early 1960 's.  However, a far
 more dramatic and Bay-wide decrease in SAV populations occurred in the              ซ
 1960's and 1970's where, unlike the eelgrass and milfoil events, all                I
 species  in almost all areas of the Bay were affected.  The change is not
 attributable to disease.
     Because there has not been a significant change in SAV distribution             •
 along the east coast of the United States comparable to the Chesapeake Bay          ™
 decline, it is most likely that water quality problems affecting the
 distribution of grasses in Bay are regional and specific to the Bay, its            m
 tributaries, and their drainage basin.  Recent international studies have           •
 found that SAV declines in other countries are highly correlated with
 changing water-quality conditions, such as decreasing water clarity
 resulting from increased eutrophication, as sewage, agricultural runoff,            I
 and  suspended sediment inputs increase.  CBP work suggests that sediment            ™
 composition and light availability are the most important factors
 controlling the distribution of SAV within regions of the Bay.   In                  •
 addition, SAV decline parallels historical increases in nutrients and               g
 chlorophyll a_ concentrations in the upper Bay and major tributaries that
 occurred first in freshwater parts and have now moved "down-river".                 _

 Value                                                                               •

    The  severity of the decline is heightened by the importance of SAV to           •
 the vitality of the Bay.  The Bay grasses are vitally important to the Bay          ^
 because  of their value as large primary producers,  food sources for
waterfowl, habitat and nursery areas for many commercially important fish,          ^
 controls for shoreline erosion, and mechanisms to buffer negative effects           •
 of excessive nutrients.                                                             ™
    Numerous studies have shown that the primary productivity of SAV
 communities is among the highest  recorded for any aquatic systems.                  •
 However, trends in SAV biomass production follows those of its  distribution         B
 and abundance.   The average biomass estimates for SAV in the Bay are low
 relative to other communities.   For example,  we have estimated  that some 40         M
percent  of primary production in  Bay was attributable to SAV in 1963 while          •
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only six percent is attributable to SAV in 1975.  These tre ids along with
other results are indicative of stressed plants, particularly in the upper
Bay.
    SAV provides food and habitat for many species of birds and animals.
The most definitive linkage is between SAV and waterfowl.   ^ome types of
SAV are excellent food for waterfowl.  In recent years, the most important
waterfowl wintering areas have also been the most abundant!/ vegetated
areas.  Waterfowl have adapted to the SAV decline primarily by wintering
elsewhere in the Atlantic Flyway.
    SAV beds in Chesapeake Bay support larger populations of most animals
than nearby unvegetated bottoms, and provide significant protection from
predators.  Fish abundance in SAV communities in the upper  Say are among
the highest ever recorded, indicating that SAV are sources  of food either
directly, or indirectly, to important Bay species.  Few
commercially-important finfish use SAV beds as significant  aursery
habitats.  However, lower Bay beds do serve as a primary blue crab nursery,
supporting a very large number of juvenile blue crabs throughout the year.
    Work in the upper Chesapeake Bay has shown that SAV is  important in
stablizing suspended sediments.  As turbid water enters SAV beds on rising
tides, sediments are effectively removed, and light transparency
increases.  Sediment resuspension is reduced in proportion  to SAV biomass.
    SAV also reduces nutrient levels in the water.  Our studies show that,
at moderate loading rates, nutrient concentrations are consistently lower
in SAV communities than in unvegetated sites.   Ammonium concentrations
were one to 10 times lower, nitrate two to 10 times lower,  and
orthophosphate generally two to four times lower in the SAV community than
in deeper, offshore waters.  When loading rates and nutrient concentrations
reached high levels, SAV was no longer effective in reducing nutrient
levels.

Cause of the Decline

    During the Bay program, investigators looked at light reduction as a
major cause of SAV decline.  Overall,  factors governing lig it energy
availability to submerged aquatic vegetation are the principal control for
growth and survival.  Bay grasses are currently living in a marginal light
environment, and water quality problems,  such as increases  Ln nutrients and
chlorophyll a_ concentrations in major tributaries and the miin stem of the
Chesapeake Bay over the past several decades, are seriously affecting the
distribution and abundance of grasses in the Bay region.  Epiphyte
communities, those organisms that directly attach to submerged aquatic
plant blades,  can also limit light availability.
    Another important factor contributing to the stress of SAV in the Bay
is the input of herbicides to the ecosystem.  Our laboratory and field
experiments indicate that herbicides are not generally available to SAV in
toxic levels,  and their presence alone probably did not cause the SAV
decline.   However,  herbicide-induced impacts could, in concert with the
other major stresses (such as those from light limitation), create
intolerable conditions for SAV existence.
    In summary, the SAV decline parallels a general increase in nutrients,
chlorophyll a_ concentrations, and turbidity in the upper Bay and major
tributaries.  This decline first ocurred in freshwater portions, and has
                               XI

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moved down-river.  The upper-Bay, western-shore, and lower-Bay communities           •
have been the most severely impacted.  Light, restricted by organic and
inorganic suspended particles from runoff and nutrient loads,  and by                 •
changes in physical-chemical regimes (salinity and temperature),  is the              •
principal factor controlling Bay-grass growth and survival.  Bay  grasses
are now living in a marginal light environment and will be adversely
stressed if water quality in the Bay declines further.  Management programs          •
that minimize .sediment and nutrient loads will have to be improved and               V
expanded if SA" is to flourish again throughout the Bay.
    The "Characterization" report will address relationships between SAV,             •
other natural resources,  and water quality trends;  the "Management                   J|
Strategies" report will suggest ways to protect and/or enhance these
resources.                                                                           ^
                               xii
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                               CONTENTS

Parts                                                              Page

   I.     How We Studied the Bay	    1
              Introduction   	    2
              Studying the Bay	    4
              Management Questions and Answers 	    6

  IT.     Nutrient Enrichment  	   36
              Introduction   	   37
              Chapter 1.  Nutrient Enrichment of Chesapeake Bay:   An
                 Historical Perspective  	   45
              Chapter 2.  Nutrient Processes in Chesapeake Bay .  .  103
              Chapter 3.  Nutrient and Sediment Loads to the
                 Tidal Chesapeake Bay System	150
              Appendix   	252
              Summary and Conclusions  	  262

 III.     Toxic Substances in Chesapeake Bay	266
              Section 1,  Introduction 	  275
              Section 2.  Findings from Studies on Metals  ....  280
              Section 3.  Findings from Studies on Organic
                             Compounds	313
              Section 4.  Patterns of Toxic Metal Enrichment .  .  .  324
              Section 5.  Findings on Sediments and Biota  ....  331
              Section 6.  Toxic Substances and Biota 	  341
              Section 7.  Conclusions and Interpretations  ....  345
              Section 8.  Research Needs 	  349
              Appendices   	362

  TV.     Submerged Aquatic Vegetation 	  378
              Introduction 	  379
              Chapter 1.  Distribution and Abundance of Submerged
                 Aquatic Vegetation in Chesapeake Bay  	  383
              Chapter 2.  Ecological Role and Value of
                 Submerged Macrophyte Communities  	  431
              Chapter 3.  Herbicides in Chesapeake Bay and their
                 Effects on Submerged Aquatic Vegetation 	  502
              Chapter 4.  Light arid Submerged Macrophyte Communities
                 in Chesapeake Bay	567
              Appendix	630
              Summary and Conclusions 	  632
Credits
   Editors
   Production
   Artwork
   Cover
Elizabeth Giles Macalaster
Debra Allender Barker
Mary Kasper
Dorothy Szepesi
Janet L. Malarkey
Laurie Harmon
Virginia Institute of Marine Science
Bill Allen
Gail Mackiernan
                               xiii

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PART I
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•                 HOW WE STUDIED THE BAY:  ASKING AND ANSWERING THE QUESTIONS
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                                            1
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                                   PART I                                       *


         HOW WE STUDIED THE BAY:   ASKING AND ANSWERING THE  QUESTIONS             I


INTRODUCTION                                                                    |

    At a singular gathering in October 1977, EPA staff,  officials  from          —
Maryland and Virginia,  and citizens developed a five-year study  plan  for         •
the Chesapeake Bay Program (CBP).   As part of the plan,  they identified  the      ™
ten foremost water quality problems of the Bay, and methods needed to
research those areas.   These ten  problems  were:                                 B

    o    wetlands alteration
    o    shoreline erosion                                                      •
    o    water quality effects of boating  and shipping                          I
    o    hydrologic modification
    o    fisheries modification
    o    shellfish bed closures                                                 B
    o    accumulation of toxic substances                                        •
    o    dredging and dredged material disposal
    o    nutrient enrichment                                                    •
    o    submerged aquatic vegetation                                           |

    By early the following winter, three critical areas were chosen from        ^
the ten for intensive investigation —  Nutrient Enrichment, Toxic              B
Substances, and the decline of Submerged Aquatic Vegetation (SAV).              *

    In all three areas, we wanted to improve our understanding of  major          B
changes taking place in the Bay.   Increasing development within  the Bay          B
area has enriched major tributaries and parts of the main Bay with
nutrients, resulting in loss of dissolved oxygen and large  algae blooms.         •
In the nutrients area, CBP has assessed the relationship between nutrients       Jj
and water quality, and the potential for future enrichment.  Until
inception of the Program, much of the basic information needed to  assess         .
the presence of toxic material in the Bay and its effects on Bay                 B
communities was not available, or poorly known.  To build an information        ~
base upon which future measures and effects can be compared, the CBP
estimated the distribution and abundance of toxic substances throughout  the       B
Bay.  The past ten years have also revealed sharp declines  in the  diversity       B
and density of SAV.  The CBP looked at the role and value of SAV in the  Bay
ecosystem and at some of the most probable causes of its decline.

    With the completion of most of the technical studies in the  summer of
1981, the CBP began to analyze and integrate results.  Early in  the program
the staff, State managers, citizens, and researchers posed  a series of
questions pertinent to managing the Bay.  These questions  appear at the  end
of this part of the report.  Using the Management Questions as a guideline,
scientists in each of the three problem areas jointly wrote research papers
that  integrate results across the specific problem areas.   To best answer
the questions for managers, decision-makers, and citizens,  the authors

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integrated into their papers not only data from specific projects,  but
information from other research and world literature.  The papers were
drafted prior to September 1981 and include data up to that point,  except
where noted.  (Some later data have been incorporated into the GBP's
characterization process as they were available.)  Drafts of the synthesis
papers were carefully reviewed by scientists outside of the Bay area as
well as by GBP staff and State participants in the Program.  The major
State agencies involved in contributing to, and reviewing the synthesis
papers include:  The Virginia State Water Control Board; the Maryland
Department of Health and Mental Hygiene; the Maryland Department of Natural
Resources; and the Pennsylvania Department of Environmental Resources.

    These papers not only respond to many of the Management Questions, but
also support the rest of the phases of GBP's program - water quality and
resources characterization, environmental quality classification, and
management strategies.  The papers, for example, provide a sound technical
foundation for the GBP's characterization process, presented in the third
final report.  In this analysis, many important parameters used to assess
water quality in parts of the Bay were identified from information in the
synthesis papers.  Furthermore, the last final report on management
strategies builds on the management questions and answers in the synthesis
papers to present the best options for managing Chesapeake Bay.

    In overview, this report represents the most technically comprehensive
product of the Program.  A list of all of the products and their
relationship to the synthesis papers includes:

    o    40 final reports on individual research projects, with summaries
         of each report.

    o    Description of the Program's computer model of the Chesapeake Bay
         system.

    o    Chesapeake Bay:  Introduction to an Ecosystem—explains important
         ecological relationships and serves as a reference for the
         synthesis report, the characterization report, and the CBP
         management alternatives.

    o    Chesapeake Bay Program Technical Studies:  A Synthesis—summarizes
         and explains the technical knowledge gained from the research
         projects funded by this program in the areas of nutrient
         enrichment, toxic substances, and submerged aquatic vegetation.
         It provides an understanding of the processes which affect the
         quality of Chesapeake Bay.

    o    Characterization of Chesapeake Bay — Assesses trends in water
         quality and living resources over time, and examines relationships
         between the two.

    o    Chesapeake Bay Program Management Study — Identifies control
         alternatives for agriculture, sewage treatment plants, industry,
         urban runoff, and construction; estimates costs and effectiveness
         of different approaches to remedy "hot spots."

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                                                                                    I
STUDYING THE BAY                                                                    •

    The integrity of Chesapeake Bay begins  far from the  actual  estuary.
The Bay itself lies within the Atlantic  Coastal Plain but  draws water  from           •
a drainage basin of 64,000 square miles  that includes five states  and  parts          9
of the Piedmont and Allegheny Plateaus,   The diverse rock  types found  in
the plateaus affect the chemical make-up of the many tributaries running to          ft
the Bay.  At the estuary,  this chemically-varied riverine  water meets  and           ฃ
mixes with oceanic water to form a variety  of physical and chemical
environments.  Since organisms living in water are suited  to  different              ^
ranges of temperature and chemical mixtures, how the mixture  changes                 •
naturally, or unnaturally, influences the ability of the Bay  to maintain a           ^
wide variety of life.

    More than 2000 species of plants and animals inhabit the  Bay.  These            0
plants and animals live in communities,  such as in marshes or on the
bottom, and depend on each other for food and shelter.  Communities respond          •
naturally to changes in the environment  through changes  in diversity and            •
abundance.  Some variations result from  seasonal changes,  others from
long-term fluctuations; still others are caused by human influences.
Assigning the cause of this biological variation to natural or  human                 •
influences is one of the most difficult  problems encountered  in ecology.            9

    To better understand the major processes governing the Bay  and its              •
inhabitants, and how they may be affected by continued input  of pollutants,          J|
GBP devised Bay-wide research plans focusing on three study areas—nutrient
enrichment, toxic chemicals, and submerged  aquatic vegetation.  State  and           ^
GBP staff, together with EPA personnel,  wrote plans of action and  asked  any          •
interested scientists to respond with suggestions and proposals for doing           ™
research.  These proposals were reviewed and modified, with selected ones
chosen for funding during the spring and summer of 1978.  The program  spent          •
nearly $17 million on 40 research projects, grants, cooperative agreements,          |
and contracts.  This approach to funding the Program's studies  allowed a
broad research community to take part in the investigations.                         •

    Scientists and institutes often cooperated in collecting  and analyzing
their data.  They shared research vessels,  used commmon  sampling sites,  and          —
similar time periods.  One of the largest cooperative efforts occurred              •
during a Bay-wide, water quality survey. During this series  of cruises              •
aboard several research vessels, scientists from a dozen private research
institutions, and State and Federal agencies collected information on
nutrients, other important water quality factors, and hydrodynamics of the
Bay and its tributaries.

    To ensure that the diverse data collected and analyzed during  the  five           •
years of investigation were credible, properly maintained, and  analyzed
accurately, CBP undertook a quality assurance program. In  this  program a
computer and research staff made sure the data from research  projects  and           •
historical sources were reliable.  The staff also prepared the  data  for              •
computer storage and analysis by devising a set of standardized names  for
variables and units.  Statistical analyses  were documented in directories
and reviewed by CBP technical staff.  In addition, inferences derived  from
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the analyses were reviewed by both technical and computer staff to assure
statistical validity and technical accuracy.


    The synthesis papers are divided into three parts.   The  first  presents
a synthesis of information on nutrient  enrichment — what the  enrichment
problem is, what chemical, physical, and biological  processes  interact  to
sustain the problem, and what the major sources of nutrients to the Bay
are.  The second part covers the CBP toxic substances program.   This
section discusses our knowledge of toxic chemicals,  sources, distribution,
and concentration of metals and organic compounds in the water and
sediment, and how geochemical and biological processes  of the  Bay  can
affect the character and distribution of toxic substances.   The third part
explains the results of GBP's SAV investigations in  light of what  factors
caused its decline.   The sections in this part discuss  the distribution and
abundance of SAV now and in the past,  the value of SAV  to the  Bay
ecosystem, the possibility of herbicides as a major  factor in  its  decline,
and light as the link between SAV and its decline.

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           MANAGEMENT QUESTIONS AND ANSWERS - NUTRIENT ENRICHMENT


1.  The Nutrient Enrichment Problem


    1.1. Where and how severe are nutrient enrichment problems in the Bay?


    The upper Bay, upper Potomac,  and upper James are nutrient enriched and
are the sites of current and potential problems.   The mid-Bay, other

Western Shore tributaries and Susquehanna are less enriched, but could
become nutrient enrichment problems.


    1.2. What are the consequences of nutrient enrichment?


    The consequences of nutrient enrichment are enhanced plant production
and higher levels of organic matter in the water column.  This organic
matter may accumulate in deep water,  where its degradation results in
oxygen depletion.  Mobile estuarine organisms leave the low oxygen water;
stationary organisms succumb.  However, it is possible that planktivorous
organisms, like menhaden, could benefit from increased production of
plankton.


    Nutrient enrichment may also alter the species composition of
phytoplankton, potentially causing changes in fisheries.


              1.2.a.    What factors  are required by phytoplankton for
                        growth?


    Phytoplankton require light, nutrients, appropriate temperature,
appropriate salinity, and innumberable other factors.  Of the criteria
listed above, only the nutrients,  specifically nitrogen and phosphorus, are
controllable by people.  Any element  can be limiting:  phytoplankton cannot
grow in inadequate light or in areas  having inappropriate salinity.


    1.3. what are the advantages and  disadvantages of the commonly used
         criteria for evaluating a water quality problem related to
         nutrient enrichment?


    Chlorophyll a levels are useful because they give a direct indication
of phytoplankton density, which is one of the important consequences of
nutrient enrichment.  There is also a fairly good historical record for
chlorophyll ฃ.  However, laboratory techniques have changed over the years,
particularly in the mid-19701s, and there may be a problem in comparing
current data with historical data. Another disadvantage is that it is
possible to have high chlorophyll a_ levels in non-enriched situations,
because of circulation and behavioral responses of phytoplankton.  For this
reason, chlorophyll a_ measurements should be repeated over time to
corroborate their validity.


    Secchi depth is a commonly used criterion because its determination is
inexpensive, and it is reliably measured from person to person.  It also
has a long historical record.  On the other hand, it is not sensitive to
small changes in photic zone, which can reflect large changes in

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turbidity.  It cannot distinguish between inorganic and organic  sources of      •
turbidity.                                                                      •

    Measurement of inorganic nutrient concentrations is fairly simple,  and
methods have been reasonably uniform historically.   However,  while high         •
inorganic nutrient levels indicate a problem,  low levels give no indication     9
of enrichment because nutrients can be tied up in organic forms.
Measurement of total nutrient levels would make it  possible to assess the       •
total enrichment of the system, but is difficult to carry out and does not      •
have good historical record.

    Dissolved oxygen levels are tremendously useful to managers  because         •
oxygen depletion is the major consequence of enrichment.  However,              ™
dissolved oxygen should be expressed as oxygen deficit (a term related to
saturation level) and should account for season. The disadvantage is that      •
short-term events, like wind, can affect dissolved  oxygen levels.                |

    Algal species shifts are a good indicator of nutrient enrichment  in         M
fresh waters, where blue-green algal blooms are known to occur under             •
enriched conditions.  However, in estuarine systems the "normal" algal
flora is not well defined, so changes due to nutrient enrichment cannot at
present be documented.                                                          •

    1.4. What techniques can be used to evaluate or predict nutrient
         enrichment problems?                                                   •

    Nutrient enrichment indices are desirable to managers because they give
an assessment of enrichment stated in very simple terms.  Their                 _
disadvantages are that they may not provide an adequate reflection of           •
complex ecological conditions; they are not generally applicable from           ™
system to system, and they are subjective.

    Computer-based mathematical models can quantify multiple combinations       H
of processes and conditions that are beyond the capacity of human
comprehension.  They are valuable planning tools because they can project       im
the response of an estuarine system to specific conditions.  On the other       •
hand, they are not generally applicable because specific pollutants and
systems require specific models.  Calibration and verification may be
difficult because of gaps in data.  Finally, people are inclined to expect      •
models to provide final answers, perhaps not scruitinizing the modelling        •
process or results sufficiently.
    1.5.  What are the historical trends in nutrient enrichment?

    In some areas of the Chesapeake Bay system, chlorophyll ฃ
I
concentrations have increased from a pre-settlement level of less than 30        •
ug/liter to over 60 ug/1 during the summer.  These areas include the upper
Bay, upper Potomac, and upper James and, for this reason such areas are
considered to be heavily enriched.  This question will be evaluated further      •
by the Chesapeake Bay Program Characterization Report.                           •
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    1.6  What are the greatest needs for further research?


    The primary need in Chesapeake Bay research is long-term coordination.

Many gaps need to be filled in basic research, and this can only be
accomplished if areas needing further research are identified and a
concerted, coordinated, long-term effort made to fill the gaps.


    Nutrients research would be furthered by the development of  better

models for the estuarine system.


    Finally, better understanding of processes like hydrodynamics,  species
composition, algal productivity, assimilative capacity, and effects on
fisheries is needed.


2.  Nutrient Processes


    2.1  What nutrients are available, at what times, in the Chesapeake Bay
         system?


    The availability of nutrients in Chesapeake Bay follows an annual cycle
which has three prominent events.  First, the spring freshet brings a
substantial amount of nitrate into the Bay.  Second, deoxygenation of deep
water in summer results in phosphate release from the sediments  and
accumulation of both phosphate and ammonium in the deoxygenated  region.
Third, reoxygenation of deep waters in fall corresponds with the loss of
phosphate from the water column and the oxidation of ammonium to nitrite
and nitrate.


    2.2  What is nutrient limitation?  How does it regulate algal
         production?


    Healthy algae require carbon, nitrogen and phosphorus in certain
ratios.  Algal production is regulated by the nutrient in least  abundance
relative to the algal requirement (assuming that other factors like light
and salinity are adequate).  The nutrient regulating algal production is
referred to as the limiting nutrient; addition of the limiting nutrient
stimulates algal production.  (Taft pp 12-29)


    2.3  When and where are phosphorus and nitrogen limiting?


    The potential for phosphorus limitation in the tidal fresh regions of
the Bay exists throughout the year.  This is because blue-green  algae,
major constituents of fresh-water systems, are not limited by nitrogen due
to their ability to fix this nutrient from the atmosphere.  (P limitation
is expressed as a potential because light may actually limit growth.)
Phosphorus is limiting in the Bay stem during spring, because this is the
major period of nitrogen influx from the tributaries, while phosphorus is
still largely bound to the sediments because of oxygenated conditions.  (In
the maximum turbidity zone light may in fact be limiting, so the potential
for phosphorus limitation may not be expressed.)

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whether the nutrient is limiting, whether luxuriant uptake occurs,  and              •
    Nitrogen is limiting over most of the main Bay in summer (with the              •
exception of the maximum turbidity zone,  where the potential for nitrogen           I
limitation exists but growth may actually be limited by light).   During the
summer phosphorus is provided from the sediments because of  anoxic                  _
conditions, while there is no major influx of nitrogen.                             •


    2.4  How does light regulate phytoplankton production?   When and where           B
         is light limiting?                                                         |

    Light may limit algal production when turbidity is high  due  to sediment         ซ
accumulation in the water column.  This happens particularly in  spring in           •
the upper Bay when sediment influx is extensive.  It may happen  in maximum
turbidity zones year-round.

    Chesapeake Bay Program research indicates that physical  processes may           •
lift phytoplankton from dark subsurface layers into the surface  waters,
overcoming the potential for light limitation for these algae.   Light               •
limitation will also not be important where adequate mixing  brings                  •
phytoplankton to the surface regularly.

    2.5  How does nutrient enrichment affect algal production?                       B

    Whether nutrient enrichment increases algal production depends on
   ther the nutrient is limiting, whether luxuri;
whether the nutrient is in its "preferred" form.

    Where a nutrient is limiting, its addition will increase algal                  B
production.  Addition of a non-limiting nutrient may also ultimately                I
increase biomass because of luxuriant uptake, in which phytoplankton take
up a nutrient but do not immediately utilize it.  Internal stores of the
nutrient are created, which can be drawn from later if there is  a shift in           •
the limiting nutrient.                                                              I

    Addition of nitrate or nitrite will not stimulate phytoplankton growth           •
in the presence of a threshold level of ammonium.  Phytoplankton                    ||
preferentially take up ammonium and will not utilize added nitrate in the
presence of ammonium.  The phenomenon was confirmed as a result  of Bay              _
Program research, and is particularly significant in the spring  when the            •
large inputs of nitrate appear to pass through into the lower areas of the           ™
Bay, unutilized because of the presence of ammonium.

    2.6  How does nutrient enrichment affect species composition, diversity         |
         and trophic relationships of phytoplankton?

    Shifts to blue-green algal dominance in the tidal fresh regions have            •
been a well-documented response to nutrient enrichment.  Such compositional
shifts have not been shown in the higher salinity areas of the estuary.
Where blooms clearly do occur in response to nutrient enrichment, they              •
result in a decline in diversity and stability of the phytoplankton                 •
community.  Thus rapid growth can be followed by rapid declines, leading to
unaesthetic conditions, de-oxygenation, and other consequences.                      •
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    Nutrient enrichment probably affects trophic relationships,  because
blue-green algae are inedible for most plankton feeders.   When blue-green
algal blooms occur and little other phytoplankton is available in the
rivers, plankton feeders must find some other food source (switch-feeding)
or decline.

    2.7  How might higher trophic levels be affected by the changes
         described in 2.6?

    When species shifts occur, the dominant organism may not provide
complete nutrition to grazers, which may shift the grazing population.
Planktivorous species may be favored by increased phytoplankton production
and species shifts; trends in menhaden populations may show this.

    2.8  What are the major water column nutrient cycling processes?

    Important processes contributing to water column nutrient dynamics  are
hydrodynamics, grazing, decomposition, and bacterial transformations of
inorganic nutrients.

    Grazing by predators (plankton feeders, etc.) and decomposition by
bacteria and fungi are the regeneration mechanisms.  Nutrient regeneration
is important because phytoplankton can use primarily inorganic nutrients.
Regeneration can be a major source of nutrients to phytoplankton during
certain periods.

    Grazing of phytoplankton by predators yields production of feces by the
grazers, as well as release of materials from the phytoplankton cells.
This facilitates bacterial degradation of phytoplankton organic material.

    Bacteria and fungi decompose dead organic matter, converting complex
organic molecules into simple inorganic molecules like nitrate,  ammonia,
phosphate, nitrite.  They also transform inorganic nutrients in
nitrification and denitrification.  New data from GBP research indicates
that nitrification is important in the fall, resulting in a nitrite maximum
then.  Nitrogen fixation may be important in the tidal fresh portions but
is insignificant in the rest of the Bay.

    Hydrodynamic processes like circulation, wind, and tides transport  and
dilute nutrients.  Increased stratification in summer results in nutrients
being held below the pycnocline.  Important vertical exchange processes are
dilution and tidal or wind mixing.  These processes, combined with chemical
and biological events, tend to retain nutrients in two-layered estuaries
like the Bay.

    2.9  What are the major sediment nutrient cycling processes,  and how do
         these contribute to nutrient enrichment?

    The important sediment nutrient processes are flux from the sediments
into the water column and vice versa, nutrient cycling, and binding of
phosphorus by iron and manganese oxides.
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                                                                                   I
    Phosphorus flux rates depend on oxidation state:  under anaerobic               B
conditions phosphorus is released from the sediments.  This is an important         B
process in deeper Bay waters in mid-summer, which may then be anoxic.
During the rest of the year waters are oxic, and iron and manganese                 mm
compounds retain phosphorus in the sediments.                                       B

    Ammonia flux rates vary with interstitial water concentration.  In
mid-summer, ammonia is not readily oxidized and accumulates in bottom               B
waters.                                                                             B

    CBP research indicates that water column nutrient recycling yields 5 to         •
10 times as much available nutrient as sediment processes.                          B

    2.10 What factors affect levels of dissolved oxygen in Bay waters and           —
         sediments?                                                                 B

    Oxygen is produced by photosynthesis.  It is also added by re-aeration,
resulting from diffusion of oxygen from air into upper waters.  Its rate            B
depends on wind, temperature, and the oxygen gradient in the water.                 B

    Oxygen is utilized by respiration, especially in summer.  Respiration           •
is carried out by phytoplankton, microbes, and animals.  Oxygen is also             B
utilized by microbes as they oxidize reduced chemical species like
ammonia.  These processes result in BOD (biochemical oxygen demand) and SOD
(sediment oxygen demand).                                                           B

    In summer, respiration rates are high because of elevated temperatures
and high production.  Respiration of detritus in bottom waters depletes             •
oxygen there, and stratification prevents re-aeration.  In some areas of            B
the Bay this summer anoxia is probably natural, but it is aggravated by
nutrient enrichment.                                                                _

    2.11 Which processes dominate seasonally?                                       *

    In spring, the major event  is the nitrate influx and the effect of              B
freshwater on stratification.                                                       B

    In summer, bottom waters are depleted of oxygen by respiration;                 •
replenishment is prevented by stratification.  Phosphorus is released by            B
the sediments, and ammonia accumulates.

    In fall, stratification is  reduced, and the water is reaerated.                 B
Nutrients are biologically and  chemically transformed as a result of the            B
newly available oxygen.

    In winter, the water is well oxygenated.  Low temperatures and light            |
levels reduce system productivity; nutrients may be present in measurable
quantities.                                                                         ซ
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•         3.  Nutrient and Sediment Loads1

               3.1  What is the atmospheric contribution to nutrient input?
I               The atmospheric nutrient contribution that directly enters tidal waters
           is at least 40 million pounds of nitrogen and 1.6 million pounds  of
           phosphorous each year [Table VIII.1(a)].   This load constitutes about 13
I           percent of the annual nitrogen, and five  percent of the annual phosphorous
           input budgets [Table VIII.l(b)].  Seasonally, atmospheric sources may make
           up as much as 20 percent of the seasonal  total nitrogen (winter)  input and
I           five percent of the seasonal total  phosphorous (summer) input and as little
           as seven percent of the total nitrogen load and three percent of  the total
           phosphorous load in the winter and  spring [Tables VIII.2(b)  to VIII.5(b)].

•             3.2. What percentage of the nutrients is from point sources?


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    On an annual basis, about 20 to 25 percent of the total nitrogen load
entering tidal waters comes from point sources basin-wide [Table
VIII.l(b)].  This percentage range would hold even if all of the point
sources load discharged above the fall line were transported directly to
the tidal system (a very conservative assumption since losses undoubtedly
occur in transport, especially during the summer).  The proportions are
relatively invariant throughout the year, reaching the lower end of the
range in the spring and the upper end in the summer and fall.
    To make a reasonable estimate of the percentage of the phosphorous load
deriving from point sources, some manipulations of the riverine loading
models developed in Chapter III were performed.  Low flow values were
chosen for each of the major tributaries2,  and the total phosphorous load
expected to occur at these flows was computed.  This total flow (sum of all
three tributaries) was about 9660 cubic feet per second.  Note from Table
IV.12(a) that the total point source flow entering above the fall line is
about 688 cfs.  The total phosphorus load computed to be carried to the
tidal system at a stream discharge of 9660  cfsd is about 1950 Ibs./day or
about 0.7 million pounds per year.  If the  extremely conservative
assumption is made that all of this load derives from point source
discharges and is summed with the 10.8 million pounds of point source
phosphorous discharged per year below the fall line, the total point source
contribution of phosphorous is computed to  be about 40 percent of the total
annual phosphorous input budget of around 11 million pounds per day.
Seasonally, the point source contribution of phosphorous makes up as much
as 65 percent of the fall total phosphorus  input budget and as little as 25
percent of the summer total phosphorous input budget.
•"•Answers to all questions in the following section are based on Chapter 3
 of Part II in "Chesapeake Bay Program Technical Studies:  A Synthesis."
^The "daily discharge that is greater than or equal to the flows that occur
 10 percent of the time" was computed for each major tributary.  They are:
 Susquehanna, 6640 cfsd; Potomac, 1690 cfsd; James, 1330 cfsd.
                                       13

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    3.3. What percentage of nutrients is from nonpoint sources and how do
         they vary over time?

    To discuss nonpoint sources within the structure of this paper,  we
define three categories of diffuse sources.  They are:
    i)   Atmospheric contributions
    ii)  Land runoff/base flow contributions
    iii) Bottom contributions
    Categories i) and ii) are  covered separately elsewhere in this section
of the Management Questions.  To answer this Management Question,  we define
nonpoint sources as the sum of land runoff and base flow (groundwater
discharge) carried by fluvial  processes to the tidal Bay system.
Contributions from the coastal plain are not considered.

    On an annual basis, the mean total nonpoint source nitrogen loading is
about 50 to 55 percent of the  total input budget, or about 160 to  177
million pounds of nitrogen per year [Tables VIII.l(a) and VIII.Kb)],
making this the single largest external source of nitrogen loading to the
Bay.  Seasonally, the variation in the nonpoint source nitrogen loading is
quite dramatic, ranging from about 23-25 million pounds in the summer (36 -
39 percent of the total source load) to around 69 - 71 million pounds in
the spring (63 - 66 percent of the total spring nitrogen load). The
dominant species of nonpoint source nitrogen at the fall line is  always
nitrite-nitrate, making up consistently between 62 and 64 percent  of the
total nitrogen from this source.

    On an average annual basis, the nonpoint source loading of phosphorous
is about 30 to 34 percent of the total phosphorous input budget,  ranging
from around 9 to 10 million pounds per year.  As much as 65 to 70  percent
of this load on an annual basis is in the suspended phase, meaning most of
the phosphorous being carried  to the Bay is associated with particulate
matter and therefore, not immediately available for phytoplankton
utilization.  Seasonally, the  nonpoint phosphorous contribution probably
varies from about 1.2 to 1.4 million pounds (only about 10-11 percent of
the summer total phosphorous budget) in the summer to about 4 million
pounds in the spring or 55 percent of the total spring input budget of
phosphorous from all sources.   The very low percentage of the load coming
from fluvial sources in the summer is due mainly to the dominant effect of
bottom sources of phosphorous  released in that season.

    3.4. What are the pollutant runoff rates for particular land uses?

    The information upon which this answer is based may be found in the EPA
Chesapeake Bay Program Information Series Nutrient Summary 3:  "Assessment
of Nonpoint Source Discharge to Chesapeake Bay" (unpublished).  The data
presented in that report are the results of a preliminary analysis of the
data from the Chesapeake Bay Program Intensive Watershed Studies (IWS).

    The analysis performed on the data used the volume-weighted mean
concentrations of storm event runoff, computed for the CBP studies
(Hartigan, 1981) along with some typical expected average annual runoff
volumes for various land use/soil texture combinations, to generate
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generalized annual pollutant loadings for various classes of land use.
These data are presented in Table VIII.6.  Although the analysis, in its
preliminary state, necessarily produced overlapping ranges of runoff
loading rates among land uses,  the data in Table VIII.6 allow us to assign
order of magnitude rankings for the land uses studied by areal loading
rate.  The generalized rankings are shown in Table VIII.7.
    In all cases, the highest unit area loading rates were generally
exhibited by cropland sites and the lowest by forest sites.
(N.B. The rankings shown in Table VIII.7 are a very broad generalizationl)
TABLE VIII.7  CONCENTRATION, MG/L (TOP LINE), AND LOADING RATES,  LBS/AC/YR
              (BOTTOM LINE), FOR TOTAL SUSPENDED SOLIDS,  TOTAL PHOSPHORUS,
              ORTHOPHOSPHATE, TOTAL NITROGEN, AND NITRITE-NITRATE FROM
              VARIOUS USES OF LAND(D(2)

Land Use
Cropland(3)
Pasture
Forest
Residential
SED
46.5-3202.8
10.54-2460.83
145.20-669.70
16.45-303.50
9.40-71.5
0.53-48.60
38.00-634.4
47.40-2395.1

TP
0.21-12.49
0.05-9.78
0.38-1.12
0.04-0.51
0.06-0.23
0.00-0.16
0.10-1.66
0.13-5.22

OP
0.01-2.77
0.01-2.20
0.06-0.14
0.01-0.06
0.00-0.04
0.00-0.03
0.02-0.17
0.03-0.54

TN
1.3-22.2
0.75-17.59
2.20-6.20
1.25-2.81
0.40-1.10
0.02-1.00
0.70-2.8
0.87-8.82

N023
0.02-16.20
0.02-12.90
0.30-1.71
0.03-0.78
0.01-0.48
0.00-0.33
0.26-0.90
0.32-2.84


^'Volume-weighted concentration data from preliminary analysis by NVPDC,
   concentration in milligrams per liter.  Personal Communication:
   "Volume-Weighted Mean Concentrations of Storm Event Runoff from EPA/CBP
   Test Watersheds," J.P. Hartigan, Regional Resources Division, Norther
   Virginia Planning District Commission, Falls Church, VA,  October 13,  1981.

'2/Loading rate computed by GBP staff, in Ibs./ac./year.

^'Cropland includes primarily conventional and minimum till with some no-
   till land practices.


TABLE VIII.8  GENERALIZED RANKING OF LAND USES BY UNIT AREA RUNOFF LOADING
              RATE (1 = HIGHEST RATE, 4 = LOWEST RATE)

Land Use
Cropland
Residential
Pasture
Forest
TN
1
2
3
4
N023
1
2
3
4
TP
1
2
3
4
OP
1
2
3
4
SED
1
2
3
4

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    For instance, one of the cropland sites in the southern portion of the
western shore produced less nitrite-nitrate per acre than one of the forest
sites on the upper Eastern Shore.  Although this example may be anomalous,
it illustrates that there is overlap in the data and that the rankings
shown are general in nature and by no means apply to all sites on all soil
types.  They are intended to give indications of which land uses, in
general, have the highest loading rates and which uses have the lowest
rates, relative to one another.

    Within the class of developed land use types such as residential and
commercial uses, it has been shown (Smullen, Hartigan, and Grizzard, 1978;
Smullen 1979, NVPDC 1979) that there is a direct relationship between
intensity of land use, often measured as the imperviousness of a site, and
the unit area loading rate yield of nutrients.  A ranking of the urban uses
by loading rate is shown in Table VIII.8.

TABLE VIII.9  RANKING OF URBAN LAND USES BY UNIT AREA LOADING RATfil FOR
              NUTRIENTS (HIGHEST LOADING RATE = 1, LOWEST LOADING RATE = 7)


Land Use	Ranking	

Central Business District                                    1
Shopping Center                                              2
High-Rise Residential                                        3
Multiple Family Housing                                      4
High Density Single Family Housing                           5
Medium Density Single Family Housing                         6
Low Density Single Family Housing                            7


    In general, urban uses exhibit higher unit area loading rates of nutrients
than forest or pasture uses and  lower rates than cropland uses.  Exceptions to
this "rule of thumb" are that pasture typically will yield slightly higher
rates than the very low-density  residential uses and that well-managed,
low-tillage cropland uses on pervious soils can yield lower rates than some of
the more intensive urban uses.

    3.5. What percentages of nonpoint source nutrient loadings can be
         attributed to particular land uses?

    To  answer this question with any level of precision, we first must accept
two basic assumptions to facilitate the  estimate, and they are:  (1) that  the
land uses are homogeneously distributed  above the fall  line; and (2) that
baseflow loadings  (groundwater contributions) of nutrients may be considered a
constant background load, and  the nonpoint  load is measured as surface runoff
   (Smullen,  Hartigan,  and Grizzard  1977)
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and interflow! nutrient loadings.  The homogeniety of land use assumption is
considered reasonable because most of the urban population resides on the
coastal plain (below the fall line) and, with the exception of the mountainous
areas, the agricultural and forest lands in the basin are fairly evenly
distributed.  This assumption is necessary because the closer a source is to
the Bay, the more effect its loading will have on the water quality of the
system.  Thus, it is important that no large mass of a particular land use
type above the fall line be closer than any other type or there would be a
skew of the loadings at the fall line reflecting that skew in the land use
distribution.  The second assumption is necessary because we do not
intuitively understand the functional relationship between land use and the
quality of groundwater discharge on basins the size of the Potomac, James, and
Susquehanna.2  We do know isolated facts — such as, the more fertilizer
applied, the greater the opportunity for increasing groundwater nitrate levels
and the resulting baseflow nitrate loadings in the stream.  For the purpose of
this analysis, it is enough to accept that for land uses that do not involve a
lot of impervious cover, the baseflow loadings will move reasonably well with
the runoff loadings.  That is to say, that land uses exhibiting higher
nutrient runoff loadings will produce groundwater discharge loadings equal to
or greater than those from uses exhibiting lower runoff nutrient loadings.


    The land uses above the fall line of the Chesapeake basin are about:
60-65 percent forested, 15-20 percent cropland, 8-12 percent pasture, 3-5
percent urban/suburban, and 2-14 percent other.  These are rough estimates
made from existing land use maps and will adequately serve the purpose of this
"order-of-magnitude" analysis.  Land use/nutrient loading rate relationships
developed locally within the Chesapeake basin (Smullen, Hartigan, and Grizzard
1978, Smullen 1979, NVPDC 1979) used for this analysis are shown below:
                                               Estimated
Land Use        Percent in Basin        Loading Rate (Ibs./ac./yr.)

Cropland
Pasture
Forest
Urban/Suburban

15-20
8-12
60-65
3-5
TN
8-18
2-6
.5-2
4-10
TP
1.5-5
.3-. 5
.05-.!
1-2

•"•Interflow is the lateral movement of water through soils to streams at
 shallow soil depths during and directly after storm events.  It is of short
 duration and, for our purposes, can be considered to be part of the runoff
 hydrograph.

2This is a good example of why assessments such as this are best made with
 mathematic models.  They facilitate the orderly sorting out of base flow,
 runoff, and interflow and allow the analyst to handle groundwater

 contributions by inspection of observed flow data.
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    The unit area loading rates shown above were weighted by
the fractions of the land areas in each use and the following ranges of
loading fractions were obtained;1
Land Use
Cropland
Pasture
Forest
Urban
Percent of Nonpoint Source Load
     TN              TP
    45-70
     4-13
     9-30
     2-12
  60-85
   3-8
   4-8
   4-12
    In summary, agricultural cropland appears to produce the largest
fraction of the nonpoint source load from above the fall lines by at least
a factor of two for both nitrogen and phosphorous.  This is partly due to a
high unit area loading rate for cropland and mostly due to the large
percentage of the land area in this use.  Forest loadings of nitrogen are
the next highest percentage and this is entirely due to the large fraction
of the watershed still being in forest land.  Urban/suburban and pasture
lands above the fall line produce approximately equal loads.

    By inspection, the percentages shown above would change very little if
the Coastal Plain areas were included.  Although the three major
metropolitan areas (Washington, B.C., Richmond, Virginia, and Baltimore,
Maryland) would increase the total amount of urban land area, this increase
would probably be offset by the large rural land areas of the eastern and
western shore portion of the Coastal Plain.  At any rate, even if the
proportion of urban area doubled, cropland would still be the largest
nonpoint source nutrient load by an approximate factor of three.

    3.6. What are the nutrient loadings from the fall line?

    The nutrient loadings from the fall line are shown in Tables III.10 and
again in Tables VIII.2 through VIII.5 in Chapter 3 of Part II in this
report.  The values for total nitrogen and total phosphorus are shown again
below in millions of pounds.
                  Annual
      Winter
Spring
Summer
Fall
178.1
10.3
51.4
2.97
72.2
4.29
25.1
1.42
27.9
0.47
       TN
       TP
The percentage of  the annual above fall line  load produced in each  season are
shown below:
 l-Some best and worst case assumptions were used along with some common sense
 judgment.  For example, the  lower range of cropland loading was produced by
 assuming the lowest loading  rate/percent land use combination for cropland
 and the middle value of the  ranges for all other uses.
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            	Winter	Spring	Summer	Fall	

       TN         28.9        40.5        14.1       15.7
       TP         28.8        41.7        13.8        4.6

    From the data presented, it can be seen that the largest fraction of the
fluvial nutrient load (40 percent of both nitrogen and phosphorus) is
discharged to the tidal system during the spring.  Observation of the data in
Table III.10 shows that a large fraction of these spring loads are in forms of
nutrients that are readily available for aquatic plant uptakel, with 68
percent of the nitrogen as ammonia or nitrite-nitrate and 34 percent of the
phosphorus as orthophosphorous.  This is important since the spring is the
critical start-up period for the phytoplankton growing season, the aquatic
plant growth that will dominate, in part, the dissolved oxygen and chlorophyll
conditions in the Bay through the summer and into the early fall.  As noted
elsewhere in this chapter, the predominant upstream source of the riverine
transported spring nutrient load is probably runoff and groundwater discharge
from agricultural lands.  The next most important source of nitrogen (but
probably lower by almost an order of magnitude) in spring river discharge from
above the fall line is probably runoff and groundwater discharge from the
melting of the snow-pack in the physiographic provinces upstream of the
Piedmont (see Figure III.2).

    The summer is the period during which the plankton growth in the Bay
reaches the annual maximum (see Chapter 2 of this part).  The fluvial
transported nutrients play a lesser role during this period providing only
about 39 percent of the readily available nitrogen forms of plant nutrients
and only about 5 percent of the readily available phosphorus.  Plankton
communities flourish during this period primarily by recycling nutrients
already in the water column (put there in part by the spring fluvial process)
as noted in Chapter VII (Table VII.5); and secondarily by the supply of
nitrogen from atmospheric, point and bottom sources and by the supply of
phosphorus from point and bottom sources.

    3.7. What do the bottom sediments contribute to nutrient inputs?

    On an annual basis, bottom sediments contribute 32 million pounds of
nitrogen and seven million pounds of phosphorus [Table VTII.l(a)].  This makes
up about 10 and 25 percent of the annual nitrogen and phosphorous budgets,
respectively [Table VIII.Kb)].  However, the nitrogen contributed from the
bottom source is predominately ammonia and makes up about 45 percent of the
total annual Bay-wide contribution of this nitrogen species, which is most
preferred by aquatic plants.  More than 50 percent of the externally supplied
water column ammonia produced during the spring and summer comes from the
benthos.

    The sediments have their most dramatic effect on the nutrient input budget
as a source of phosphorous in the summer.  As discussed in Section V, most of
phosphorous migrating up through the sediments via the pore waters probably is
fixed chemically by iron in the overlying oxygen-rich waters and held in a
fluff layer as a small particle, or floe.  This process occurs during most of
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the year (late fall, winter, spring).  However, when the oxygen in the lower
layers of the Bay waters is depleted for periods during the summer, most of
the phosphorus incorporated or stored during the rest of the year probably is
released over a very short period of time.  The result is that as much as 62
percent of the phosphorous input to the Bay in the summer could come from this
source.  Other than recycling, the bottom source is probably the single
largest factor in the supply of phosphorous for summer primary productivity.

    3.8. What are the flux rates of nutrients from the bottom sediments and
         how do they vary seasonally?

    The bottom flux rates for nitrogen range from as low as 0.5 pounds of N
per square foot per day in portions of the upper Bay in the spring to as high
as 5 pounds of N per square foot per day in portions of the upper Bay in the
spring and summer.  The annual seasonal Bay-wide average flux rates for
nitrogen are shown below:

            Nitrogen Senthic Flux of Nitrogen
                (Thousands of Pounds      Percent of
                  per day)	Annual Average
Winter
Spring
Summer
Fall
Annual Average
88.1
75.3
98.4
91.2
• 88.3
100
85
111
103

    As can be seen above, the summer period exhibits the highest flux rate of
nitrogen from the sediments, and the spring the lowest.  The nitrogen is
moving out of the sediments fastest when the standing crop of phytoplankton is
largest, and being produced in a form readily available for plant uptake.

    As discussed previously, the seasonal variation of phosphorous flux from
the sediment to the water column is severe, with about 85 percent of the total
annual input being released rapidly sometime from late May to mid-June, with
most of the other 15 percent released from that time through late summer.

    The maximum Bay-wide phosphorous release rate might be as high as one-half
million pounds a day during the period of the rapid onset of bottom-water
anoxia.  This rate probably levels off to about 16,000 pounds per day by late
summer and down to near zero by sometime in late fall.

    3.9. Given the estimated loadings of nutrients for each of the sources,
         which will be the most important in terms of their effects on the Bay
         system?

    This is a difficult question to answer, because there are so many
potential effects on the Bay system that could result from variations in
nutrient loadings.  Some effects are understood well; some not so well, and
some are unknown.  However, to provide an answer to this question, we will
consider the potential effects on Bay-wide primary production which might
result from variations in the amounts of nutrients entering from various
sources.
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    On an annual basis (Table VII.2), probably only about 20 to 30 percent of
primary production in the Bay proper is supported by nitrogen and phosphorous
entering the water column from external sources.   We will assume that nutrient
recycling rates by phytoplankton would vary only moderately in response to
changes in external nutrient supply.  Given this assumption, it can be seen
from the data in Table VII.2 that even as much as a 50 percent reduction in
both point and nonpoint source annual nutrient loadings may result in only a
10 percent reduction in Bay-wide primary production.  Seasonally, this effect
could decrease to a 5 percent reduction in summer production in response to a
50 percent reduction of summer point/nonpoint nutrient loading.  If these
loading reductions were sustained, production would probably decrease futher
as the nutrient reservoir in the sediments depleted over time.  These
estimated decreases of primary production  in the short-term approach the
detection limit of our ability to assess such reductions.

    The important point in this discussion is that changes in lower Bay water
quality (essentially meaning the great majority of the Bay that lies below the
mouth of the Patuxent) in response to changes in nutrient inputs would
probably take place slowly over decades.  However, the upper portions of the
Bay and the tidal tributaries would be much more responsive to change in
nutrient loads than the main Bay.  The nutrient loads that the main Bay
receives must travel through these smaller, heavily impacted areas of the
system.

    The nutrient inputs are diluted as they move towards the lower Bay as a
function of ever increasing volume.  In addition, the surface area available
for contributing nutrients from the sediments is much greater in the main Bay
than in the upper portions of the system, resulting in much larger bottom
releases of nutrients.  These factors and others create a situation in the
main Bay that tends to buffer or dampen water quality response to changes in
anthropogenic nutrient loadings.  It is, therefore, reasonable to expect the
water quality of the upper areas (tidal fresh areas) of the system to respond
more quickly to load reductions than the areas of the lower main Bay.

    The apparent improvement in the water quality of the upper Potomac in
response to decreased nutrient loadings over the last decade would seem to
support this concept.  Even though some unknown amount of that improvement
probably results from differing climatic conditions over the last ten years,
some degree of the improvement is most likely due to the decreases in the
external nutrient supply from POTW's.  We would not expect to see immediate
changes in lower Bay water quality due to that reduction of loading and, in
fact, have not.  Such a change could only be seen over a much longer period of
time and to a lesser (diluted) extent.  This situation would seem to support
the concept that if we manage the local ("near field") problems, the main Bay
("far field") will, in time, respond in kind.  An aggressive policy of water
quality improvement in currently adversely impacted areas should insure the
maintenance of a nondegradation condition in the main Bay.
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              MANAGEMENT QUESTIONS AND ANSWERS - TOXIC SUBSTANCES
1.  Is there a toxic chemical problem in the Chesapeake Bay?

    There are trends of general concern and specific problem  areas.                 B

    There is concern that grass, shad,  and bass have declined in the last
three decades and that oyster reproduction has diminished.  In the James            B
River, chlorine is strongly suspected of causing massive fish kills  and Kepone      B
has resulted in closure of the estuary  to fishing for years.   At the same
time, there is an increase in the number of potentially toxic chemicals            m
synthesized, produced, and used in the  region.  Analysis of a sediment core        B
from the northern Bay, for example, reveals an upward increase in metal
content of Cu and Zn with time.  Enrichment factors range from 3 to  20.

    Although it is recognized that toxicants accumulate in certain biota  many      3
thousandfold more than ambient concentrations, the link between cause and
effect still eludes scientists.  Toxic  chemicals, however,  are strongly            •
suspected of being partly responsible for the decline of essential biotic          fl
components.  The fact that many compounds are carcinogenic to mammals is  cause
for concern.

    Major problem areas are Baltimore Harbor - Patapsco River - and  Norfolk        ™
Harbor - Elizabeth River - which are sources of industrial/municipal discharge
and shipping activity.  Because of their limited circulation, these  areas are      •
natural "sinks" for toxics adsorbed on  fine sediment.  Concentrations of            |
metals, for example, are 2 to 50 times  greater than in mid-Chesapeake Bay.
Zones of metals enrichment in Baltimore Harbor are associated with disrupted       _
bottom communities.  Bioassays of fish, invertebrates and bacteria indicate        I
effluents have moderate to high toxicity.  The greatest number of organic          ™
compounds detected per oyster and the highest concentrations  were recorded off
the James River and Baltimore Harbor.                                              •

    1.1  What toxic chemicals are present and what is the concentration of
         them in the estuary?                                                      •

    Two classes of chemicals pose a threat to the Bay; 1) inorganic  compounds,
mainly trace metals like As, Cd, Cr, Cu, Hg, Sn and Zn; 2) organic compounds        _
including pesticides, phthalate esters, polynuclear aromatic  hydrocarbons           B
(PAHs), polychlorinated hiphenyls (PCBs) and many other chlorinated                  ™
hydrocarbon compounds.  Many of these chemicals are produced  naturally or
synthetically.  Approximately 300 organic compounds were found in the Bay's         •
sediment, the majority of these compounds were PAHs.                                B

    The trace metals are found in several phases; 1) dissolved, and  2) solids,       •
either sorbed to suspended sediment or bed sediment.  Although concentrations       B
may reach high values in biota, the bed sediments contain the greater mass and
thus constitute the main toxic reservoir.  Because sediments  have a  longer
residence time in the Bay than water, bottom filter feeders like oysters  are        I
more exposed to contaminated sediment than water.                                   B
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            SUMMARY OF MEAN METAL CONCENTRATIONS IN BOTTOM SEDIMENT,
               SUSPENDED MATTER, AND DISSOLVED PHASES IN THE BAY

Metal
As
Cd
Co
Cr
Cu
Fe
Hg
Mn
Mo
Ni
Pb
Sc
Sn
Th
U
Zn
Bottom 1
Sediment
ug/g
3.9
0.4
12.8
28.9
21.6
24,250.0
0.1
848.0
	
26.1
29.4
	
0.7
	
	
157.0
Suspended *
Sediment
ug/g
13.0
14.16
—
	
127.96
3.11%
3.89
2.88
	
95.80
160.30
	
17.97
	
	
0.75
Dissolved3
Water Column
ug/1

0.05
0.07
0.17
0.66
3.12
	
13.88
3.26
1.21
0.11
	
0.86
	
0.93
1.19

1 - Means from combined Nichols and Helz (1981)  data.
2 - prom Nichols (1981)
3 - From Kingston (1981)

    Summary of mean concentrations of various PAH organic  compounds  in Bay
sediments listed on EPA's priority pollutant list.

                 Compound                  Mean  Concentration (ppm)

             Phenanthrene                           575
             Pyrene                                 758
             Floranthene                            962
             Benz (a) anthracene                    310
             Chrysene                               448
             Benzo (a) pyrene                       440
             Benzo (ghi) perylene                   271

    1.2  What are toxic chemicals associated with?

    Most toxic materials tend to partition with  sediment.   Organic
compounds and metals tend to partition to suspended material  and  then  are
deposited on the bottom as the suspended sediment is deposited.   Because of
polarity, some organics may be dissolved in the  water  column  and  exist
below the detection limit of present day instrumentation.
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                                                                                   I
    1.3  Do toxic substances entering the system accumulate?
    Most toxic chemicals of all classes entering the system accumulate in
the sediment; others degrade, and some accumulate in the biota or are
flushed out of the system.  The degradation process occurs under changing          I
physical/chemical conditions.  Suspended sediment is particularly important        I
in the accumulation of toxic materials, because metals are adsorbed,  found
and precipitated on suspended material.  In this form they can be picked up        •
by filter-feeding organisms or metabolized by plankton and reach high              I
concentrations.

    Fluid mud, dense suspensions of sediment, lies in fluid masses near the        I
bottom of the Bay.  It serves both as a reservoir for potentially toxic            •
metals and as a medium for chemical transfer between the mud and overlying
water.                                                                             •

    Analysis of selected sediment cores demonstrate that Cu, Zn, Pb and Co
increase dramatically near the sediment-water interface indicating that            _
sediments are an important reservoir of metals and that the origin of these        •
metals is man's activity.                                                          ™

    1.4  Is the Bay regionally contaminated with trace metals?                     M

    Metal content of bed sediments from the main northern Bay is enriched 4
to 6 times in Mn, Pb and Zn compared to average shale.  Sediment cores show        •
an upward increase of more than two times.  The distribution of enrichment         I
factors in the main Bay is controlled by sediment type and deposition
processes rather than nearness to sources of contamination.

    Enrichment of suspended material in near-surface water of the central          I
Bay in Cd, Cu, Ni, Pb, and Zn is related to high organic content.
Enrichment exceeds natural concentrations of metals in oceanic plankton 9           •
to 19 times.                                                                       |

    1.5  Is the Bay regionally contaminated with organic compounds?                 _

    Although concentrations are variable, some areas of the Bay have                 •
extremely high concentrations of toxic organic compounds.  Approximate
maximum concentrations of various organic compounds measured in Bay                 I
sediments are:                                                                      •

                 Compound                  Max. Concentration (ppm)
             Phenanthrene                              100
             Pyrene                                    150
             Benz (a) anthracene                        70
             Chrysene                                   90
             Benzo (a) pyrene                           90
             Benzo (ghi) perylene                       70
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             Floranthene                               200                          fl
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    With the magnitude of these concentrations, regional contamination is
very obvious and at alarming levels in some areas.


    1.6  Do levels of toxic chemicals found in the environment present a
         risk to the ecosystem?


    Certain compounds including PAH's, PCB's, phthalate esters, DDT,  As,
Cd, Cr, Pb, Hg, Zn, may represent a risk to the ecosystem.  However,  to
evaluate the risk associated with these chemicals is a complex problem.
Each specific compound has a different effect on various species.
Likewise, each species has a different reaction to specific compounds.  To
make the problem more complex, the synergistic effects and the stress which
toxic material places on organisms are nearly impossible to quantify.  For
the most part, the observed dissolved metals concentrations do not exceed
risk levels.  For organic compounds, we have very little information on
concentrations in the water column from which to make an evaluation.


    Bioassays performed on specific sediment samples can indicate relative
toxicity of the sediment.  These tests indicate that the sediments in the
Bay and several tributaries are generally more toxic than a west coast
estuary.  Also, an assessment of biological indices of the bottom biota in
the Baltimore Harbor indicate that there are stressed and impacted
conditions existing there.


    2.0  What is the distribution of toxic chemicals in the Bay?


    In suspended material, metal content per gram of As, Cd, Cu, Pb,  Hg,
Ni, Sn and Zn are maximal in near-surface water of the central Bay.   These
concentrations most likely are bioaccumulated by plankton.  On the other
hand, per liter of water, metal concentrations are highest in the northern
Bay where suspended sediment concentrations are high - a zone called  the
turbidity maximum.


    In bed sediment, metal content of Cr, Mn, Fe, Co, and Ni is highest in
fine sediment of the northern Bay.  Concentrations of most metals are
maximal in the zone from the Susquehanna mouth to the Patapsco mouth  where
fine sediment is entrapped.  Concentrations of Cr, Pb, and Zn are maximal
in Baltimore Harbor and concentrations are not elevated in the main Bay off
Baltimore.  Concentrations of metals are relatively low throughout the
southern Bay.  Organic compounds are highest in fine, bed sediment from the
Bay between the Susquehanna River and the Patapsco River.  They generally
decrease further seaward to the Potomac River; but in the southern Bay,
locally high concentrations are found in sediment from estuary entrances.


    The distribution of both metal and organic compounds is associated with
the distribution of fine sediment and moderate to fast sedimentation.


    2.1  What parts of the Bay are most susceptible to contamination?


    The greatest enrichment may be expected in zones where: 1) the source
supply is high and entrapment is good; 2) fine sediment accumulates;  and 3)
where rates of sedimentation are moderate to fast.  Contamination of  near
                                       25

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                                                                                   I
 source areas is common to tributaries near treatment plants and industrial         •
 facilities.  Contamination that follows the fine sediment and fast rates of        •
 sedimentation is common to the main Bay, the zone of deep water in the
 central Bay.  Sediment water content and fluid mud thicknesses are greatest        M
 in this region.  This zone holds atmospheric contaminates as well as               I
 water-borne contaminates settled from overlying water or dispersed a great
 distance from their source.

    Identifying locations of accumulation shows the distribution of fine           •
 grain sediments to which toxic chemical attach.  Locations in the Bay
 accumulate sediments at variable rates from negative values because of             •
 erosion, to several m/century.  In the upper Bay, fine grain sediment              •
 accumulates N to S generally down the Bay,  especially between Baltimore and
 mouth of the Chester River.  These accumulations are small, amounting to .5        ^
 to 3 m/century.                                                                    •

    In the lower Bay, accumulation is again N to S in three main regions.
 The average rate is 0.5 m/century.  The first region is in the deep channel        •
 down the stem of the Bay and where the channel flairs, just above the              |
 Rappahannock River.  As much as 1.5 to 2 m/century accumulates at this
 location and sediment here is mostly silt/clay.  The second region is just         im
north of the York River; locally rates are  as great as 2.5 m/century on the        V
 eastern flank of the Cape Charles deep opposite Old Plantation Flats.
 Sediment here is very fine sand.  That same latitude, 37ฐ20:  shows
similar accumulation on the western side of the channel.                           •

    2.2  What role do the biota play in the transport of toxic substances
         from the sediment to the water column?                                    •

    Generally,  benthic animals living in or on bottom sediments can
reintroduce chemicals from the sediments to the water column.   In addition,        _
fish migrating  to other parts of the Bay or Atlantic Ocean can transport           •
chemicals with  them.  The main activities of benthic animals  that  can
 transport chemicals are:

    o    mixing - causing newly arrived surface material to be quickly             !•
         buried or resurfacing older material.

    o    ventilation - increasing the exchange between interstitial water          |
         and the water column.

    o    increasing sediment stability - decreasing the probability that           I
         buried material will be resurfaced.                                       ™

    o    decreasing sediment stability - increasing the probability that
         buried material will be resurfaced.

    o    causing rapid sedimentation - through pellitization of fine               ••
         suspended particles.                                                      I
    o    causing erosion - by making sediment more easily transported.
         bioaccumulation
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    2.3  What other processes (physical or chemical) exist which can cause
         remobilization of toxic chemicals into the water column?


    Materials in the bottom sediment may be reintroduced to the surface
environment and water column by two groups of processes.


    Physical disturbance of the sediment can reintroduce toxic substances
by storms, biologic activity (bioturbation),  dredging and other engineering
projects, propeller wash, harvesting of bottom organisms by dredging (e.g.,
clams, oysters).


    Important chemical processes leading to remobilization might include
diffusion driven by concentration differences, and life processes of
benthic organisms such as irrigation of burrows and benthic feeding.


    Physical disturbances are episodic occurrences whereas diffusion is a
continuously operating process.  Exhumation and resuspension of sediment by
physical processes can re-expose material that had previously been buried
and out of direct contact with the surface environment.  Interstitial
water, the water trapped in the voids between sediment particles as the
sediment accumulates in the subaqueuous environment, is the vehicle through
which chemical constituents in the sediment are continuously remobilized
and transported within the sediment and across the sediment-water interface.


3.  What are the sources and loadings of the pollutants of concern?


    3.1  What is the direct contribution of toxic material from point
         sources?


                                    Metric tons per year
                            Cr       Cd      Pb      Cu      Zn


Municipal Wastewater        200       6      68      99     284
Industrial Discharge        199     178     155     190     167


    3,2  What is the direct contribution from nonpoint sources?


                                    Metric tons per year
                            Cr       Cd      Pb      Cu      Zn


Shore Erosion               83        1      28      29      96
Atmosphere                 189       99     582      95       ?


    3.3  What are the loadings from the major tributaries?


                                    Metric tons per year
                            Cr       Cd      Pb      Cu      Zn
Urban Runoff                 1
Rivers                     100        4     180     220     1500
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    3.5  Are there other sources of toxic substances?

    The massive reservoir of materials contained in the bottom sediments of        ™
estuaries have largely been ignored as a potential source of nutrients and
trace elements until recent years.   On the basis of interstitial water             •
chemistry investigations, it is apparent that there is a very substantial          |
contribution of these substances from the sediment to the water column.   By
far, the largest source of Pb is the atmosphere, and the largest source  of         _
Cd is industrial effluents.                                                        •
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       MANAGEMENT QUESTIONS AND ANSWERS - SUBMERGED AQUATIC VEGETATION

1.  Is there a problem in Chesapeake Bay related to SAV?

    Yes, because SAV is declining, and because it has an important
ecological role and economic value.

    1.1. Are the current distribution and abundance of SAV unusually low ?

    Yes, probably lower than every recorded in the Bay's history.

         1.1.1.    What is the current distribution and abundance of SAV in
                   Chesapeake Bay?

    About 16,000 hectares, or 5 percent of the portion of the Bay less than
two meters deep is vegetated by SAV.  (Sediment type and exposure to winds
and currents make much of this shallow area unsuitable for SAV.)  Most SAV
is concentrated in four regions of the Bay:  (1) the middle stretch of
Maryland's Eastern Shore, including the Chester River, Eastern Bay, and the
Choptank River, (2) the shoals between Smith and Tangier Islands, (3)
behind sand bars along Virginia's Eastern Shore, (4) around the mouth of
the York River from Mobjack Bay to Back River.

         1.1.2.    Have the distribution and abundance of SAV recently
                   declined?

    Yes, dramatic declines have occurred since the 1960's.  In limited
sampling between 1967 and 1969 along Maryland's Eastern shore from near the
head of the Bay to Pocomoke Sound, most areas had 70 to 100 percent of
their sampling stations vegetated by SAV.  Only one area had less than a
third of its stations vegetated.  An annual summer survey by the U.S. Fish
and Wildlife Service and Maryland's Department of Natural Resources shows
that only 28.5 percent of their sampling stations in Maryland was vegetated
in 1971, and only 10.5 percent was vegetated in 1973.  Smaller fluctuations
have occurred since 1973, and the percentage of vegetated stations now
stands at an all-time low of eight.  Archival aerial photography of six
locations in the lower Bay reveals that five of them experienced declines
since 1960s ranging from 45 to more than 99 percent.

         1.1.3.    Have all areas and species experienced declines at the
                   same time and to the same degree?  Have the declines
                   been gradual, or sudden events occurring between periods
                   of relative stability?

    All areas and species have been affected, but not to the same degree,
nor at precisely the same time.  The areas mentioned in 1.1 as currently
having most of the SAV have been the least affected.  The head of the Bay,
Maryland's lower Eastern Shore from Taylors Island to Pocomoke Sound, and
the major Western Shore Rivers have been the most affected.  Overall,
during the last 15 years, declines have been a combination of sudden drops
superimposed on an uneven but continuing downward trend.  The Potomac and
Patuxent Rivers experienced large declines between 1965 and 1970.  In 1907,
                                       29

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                   as severe as the one of the last decade ever occurred
                   before, or that cyclic changes have occurred?
         1.2. Does SAV have a significant ecological role and economic
              value?
    Yes.
                                       30
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the Potomac had dense beds of SAV along both shores, but by 1970, only             ^
scattered pockets of vegetation remained.  Large declines along Maryland's         •
Eastern Shore occurred between 1969 and 1971.  Further big declines                ™
occurred in the upper Bay in 1972, the year of tropical storm Agnes.  In
the Susquehanna Flats during the early 1960's, European milfoil displaced          B
native species to a great extent.  When milfoil declined in the mid-19601s,        •
the native species recovered about two-thirds of their former abundance
before decreasing slightly in the late 1960's.  In 1972, there was a               m
dramatic decrease in SAV abundance.  Virginia's Eastern Shore had major            I
declines between 1972 and 1974.

         1.1.4.    Have deeper areas been affected more than shallower             M
                   areas, thus implicating turbidity as a cause of decline?        W

    There is not enough evidence to say conclusively that deeper areas have        •
been affected more than shallower areas, but limited evidence from archival        •
photography suggests that this may be the case, at least in some areas.
1.1.5.    Does the biostratigraphic record indicate that a decline        •
          A .Q ซp\7PTta as t~Vip nn<3 n f t~h
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foods, while redheads and wigeon have found other wintering areas.  SAV
also contributes to the detritus-based food web.

         1.2.2.    Does SAV provide habitat, especially for economically
                   important species?

    SAV beds currently support two to five times  more finfish and
invertebrates than nearby bare areas.  SAV beds in Virginia are important
nurseries for blue crabs.  In Chesapeake Bay, in contrast to other regions,
there is insufficient evidence to support the idea that SAV beds are
nurseries for commercially important finfish; however, there is good
evidence that numerous fish of ecological, but not economic importance
occur in SAV beds.

         1.2.3.    Does SAV play an important role in nutrient dynamics?

    SAV may act as a nutrient buffer, potentially taking up large
quantities of nutrients during the spring growth  period.  In comparison to
algae, SAV releases nutrients more slowly, and exerts a lower oxygen demand
during decomposition after autumn die-back.  GBP  research has demonstrated
the ability of SAV to rapidly take up nutrients from the water column, as
well as from sediments.

         1.2.4.    Does SAV play an important role in sediment dynamics?

    SAV roots and rhizomes can stabilize sediments, and SAV shoots can slow
water currents and dissipate waves, thus allowing suspended material to
settle to the bottom.  CBP research at sites in Eastern Bay and the
Choptank River has documented that suspended sediments are removed from
water moving into SAV beds.

2.  If there is a problem regarding SAV, what caused it?

    Different combinations of factors were probably important in different
localities.

    2.1. Have herbicides been a factor in the decline of SAV?

    They have probably not been the major Bay-wide factor.  Extensive
research on atrazine and linuron indicate that these pesticides may have
been a contributing cause of decline of SAV already stressed by other
factors, but this would be true only for SAV beds near sites of herbicide
application, and in years when precipitation occurred soon after
application.

    2.1.1.    What effects do herbicides have on  SAV, and at what
              concentrations are these effects produced?
    Atrazine and linuron concentrations of 50-100 ppb consistently cause
significant reductions in photosynthesis in several species of SAV.  Five
to 10 ppb sometimes produce harmful effects.  One ppm can kill SAV.
Sublethal effects can last several days after exposure times of one to a
few hours.  Generally, full recovery occurs after exposures of less than
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                                                                                  I
100-500 ppb.  Experiments have not been done on toxicity of degradation
products to SAV, but for agricultural weeds, degradat
atrazine are far less toxic than the parent compound.

         2.1.2.    How do herbicides enter SAV?
products to SAV, but for agricultural weeds,  degradation products of               •
                                                                                   I
    They are taken up from the water column through the leaves.   Root
uptake can also occur, but is probably much less important because                 M
herbicide availability in the sediment is low.                                     •

         2.1.3.    To what amounts of herbicides is SAV exposed,  and for
                   how long?                                                       •

    Observed high concentrations of atrazine were 4 ppb in the mainstem of
the Bay, 7 ppb in the primary tributaries, 20 ppb in secondary bays and            •
coves, and 100 ppb in drainage creeks adjacent to agricultural fields.              I
Exposure concentrations declined from these highs to about 20 ppb in a few
hours in drainage creeks, to about 7 ppb in a few days in secondary bays
and coves, to about 4 ppb in a few weeks in the primary tributaries, and to        •
near zero ppb in a few weeks in the mainstem of the Bay.                           •

         2.1.4.    What physical and chemical processes are involved in the        A
                   transfer of herbicides from agricultural fields to SAV?         jj
                   What degradation rates and sorption constants do
                   herbicides have?                                                ^

    Atrazine applied to agricultural fields can adsorb to sediment                 ^
particles and colloidal material, or dissolve in water.  Sorption
coefficients for colloids are about 10 times higher than those for                 •
sediments, and sorption to sediments is about 10 times greater than                •
solubility in water.  However, over 90 percent of the atrazine in estuaries
is in the unfilterable component of the water column.  Herbicides are              *
transported to the estuary mainly by runoff, although transport  by                 •
subsurface drainage is also possible.  Half lives of atrazine due to
degradation are a few days to a few weeks in estuarine water, a  month or
more in estuarine sediments, and up to a year in agricultural soils.               •

    2.2. Has the decline of SAV been caused by inadequate light  reaching
         SAV leaves?                                                               •

    Inadequate light may be the most important proximate cause of SAV
decline.                                                                           ซ

         2.2.1.    How does SAV respond to different amounts of                     *
                   photosynthetically active radiation (PAR)?

    As the amount of PAR increases, net photosynthesis increases to a              |
maximum.  At this point net photosynthesis is light saturated.  Above this
point, SAV may become inhibited by too much lihgt.  Below the saturation           M
point, there is a compensation point at which gross photosynthesis equals          •
respiration, and net photosynthesis is zero.  Community compensation points
are on the order of 200-300 microeinsteins per square meter per second.
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These rates can vary considerably depending on periphyton density and other
factors.  Compensation points for individual species are on the order of 30
to 50 microeinsteins per square meter per second.  Maximum rates of net
daytime photosynthesis are on the order of 1.1 to 1.3 mg C g~lhr~^.
Upper Bay species are generally not light saturated (i.e., they are light
limited), and that their photosynthetic efficiency does not change
seasonally.  In the lower Bay, Zostera marina is light limited during both
its spring and fall growing seasons, and appears to undergo acclimitization.

         2.2.2.    How do light and herbicides act together to affect SAV
                   photosynthesis?

    Although other research indicates that herbicides have a diminished
relative effect at lower light levels, CBP research does not convincingly
support such a conclusion.

         2.2.3.    What is the quantity and spectral distribution of light
                   at different depths in SAV beds, bare areas, and areas
                   that recently have lost their vegetation, and how do
                   they vary seasonally?

    Light penetration is greatest in the green and least in the blue region
of the spectrum.  Studies in a limited region of the lower Bay indicated no
significant difference between spectral distributions in bare and vegetated
areas.  The attenuation coeffiecient for PAR ranged from 0.5 m~l to 1.6
m~l, and increased significantly from April to July at most sites.  No
clear pattern of difference occurred between vegetated and nearby bare
areas in the lower Bay.  In the upper Bay, attenuation was usually less in
SAV beds than in bare areas.

         2.2.4.    What are the sources of turbidity, and what is their
                   relative importance?

    Suspended sediments and phytoplankton are the major contributors to
turbidity.  Their relative importance varies seasonally and between
localities.

    2.3. Has the decline in SAV been caused by changes in nutrient levels
         in the Bay?

    Nutrient enrichment, through its stimulation of phytoplankton and
periphyton, is a factor controlling SAV, and may have contributed to its
decline.

         2.3.1.    To what levels of nitrogen is SAV exposed, and how do
                   they vary seasonally?

    Nitrate concentrations in the water column range from near zero to 100
micromolar.  Nitrite concentrations range from near zero to 2 micromolar.
Ammonium concentrations range from near zero to 20 micromolar.   Nitrate
concentrations are highest in spring and decline to a low in summer.   In
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the upper Bay, interstitial concentrations of ammonium ion in the  rooting           JM
zone (down to 15 to 20 cm) are about 80 micromolar.                                 H

         2.3.2.     How do nitrogen levels indirectly  affect SAV?

    Nutrient enrichment can stimulate the growth of  phytoplankton, which           V
can contribute to attenuation of light in the water  column.  Phytoplankton
can also stimulate the growth of filter feeding animals that live  attached         •
to SAV leaves.  These filter feeders can form a crust that blocks  light  and         ^
depresses photosynthesis.  Nutrient enrichment can also stimulate  epiphytic
algae, which can block light.  Epiphytic algae may also be controlled  by           —
animals that graze on the surface of SAV leaves.  One such grazer  that is           •
found in Virginia, the snail Diastoma, has been shown under experimental           ™
conditions to dramatically decrease the density of periphyton on Zostera.
The western shore population of Diastoma may have been virtually eliminated         ft
by the low salinities resulting from flooding at the  time of tropical  storm         ||
Agnes in 1972.  The loss of Diastoma may be an important cause of  SAV
decline in certain localities along Virginia's western shore.                      -M

    2.4. In summary, what are the most likely principal causes of  SAV
         decline during the last 20 years?

    SAV can be stressed by many factors whose relative importance  can  vary         V
spatially, seasonally, and yearly.  Some of these stresses include light
attenuation in the water column caused by suspended  sediment and                    4|
phytoplankton, light attenuation by periphyton, herbicides, unusually  high         •
salinities, physical damage by storms, eating by whistling swans,  uprooting
by cownose rays, and biotic interactions that are not fully understood.             ^
Underlying factors may control one or more of these  stresses.  For                 H
instance, nutrient enrichment can stimulate both phytoplankton and                 ™
periphyton.  These multiple stresses, and the complex time-space patterns
they can exhibit, must be considered against the background of the history         ฃ
of SAV distribution and abundance in the Bay.  Historically, Chesapeake  Bay         •
probably had much more SAV than now.  In 1907, extensive beds of SAV
occurred along the length of the Potomac River estuary.  It is reasonable           ซ
to expect that the same was true of other parts of the Bay.  Precipitous           •
declines have occurred throughout most of the Bay since 1969, but  not  all
species or areas have been equally affected.  Disease cannot, by  itself,
explain the declines because it probably would not affect all species               •
equally.  The pattern of decline does not support the idea that point               H
sources of pollution are the single cause of decline.  The biostratigraphic
record does not support the concept of entrained cycles in SAV populations,         •
and tropical storm Agnes, although probably an important factor,  is not the         |
single cause of decline, again because the pattern of decline is not
consistent with such an hypothesis.  Interestingly,  there is a positive            _
correlation between SAV decline and potential diffuse loading (the ratio of         V
the drainage area of a river to the river's volume).   These facts  suggest           •
that a Bay-wide decline can be demonstrated.  In particular, herbicides,
although potential stresses, are not the sole cause  of decline. Nutrient           A
enrichment, and its effects of light attenuation, may be the most  important         ^
contributing causes.
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                2.5.  What  are  the minimum requirements  for SAV growth?


                Because  factors may  interact  in  a  complex way, the minimum requirement
M          for one factor depends on current levels of other factors.  The following
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            levels  represent very  rough approximations that cannot be well
            substantiated by current  information.  Light:  above 200-300 uE m~28~
            measured  in  the water  column of SAV beds.  Herbicides:  below 5 ppb
            measured  in  water column.
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                                               PART II

                                        NUTRIENT ENRICHMENT
                                        Christopher F. D'Elia
                                               Jay Taft
                                           James T. Sraullen
ซ                                          Joseph Macknis
                                        Technical Coordinator


                                            Willa Nehlsen
                                              36

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                                                                                   I
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                                TNTRODUCTION

    The nutrients portion of this  synthesis report presents the integrated         V
findings of the Nutrients Program of the Chesapeake Bay Program (CBP).
More than 10 individual research projects (listed in Appendix A),  funded            f*
under the CBP, contributed to the  three chapters of this part.   Additional         p
literature, other data bases, and  many individuals also contributed
valuable information for completing the synthesis of our knowledge of
nutrient enrichment in Chesapeake  Bay.                                             I
    The CBP studied nutrients, because the natural process of nutrient              w
enrichment, or eutrophication, is  being hastened by anthropogenic  (or
human-related) contributions of primarily nitrogen and phosphorus                   •
compounds.  Though needed by Bay organisms to grow, excesses of these              J
nutrients can deteriorate the water quality.
    Inorganic nitrogen and phosphorus compounds, such as nitrite,  nitrate,         ^
ammonia, and phosphate, are referred to as "nutrients" because they  are            •
required by plants for growth.  In an estuary like the Chesapeake  Bay,              *
nutrients support the growth of phytoplankton, submerged aquatic
vegetation, and emergent marsh grasses.  This plant material, in turn,              A
supports the rest of the many organisms in the Bay.                                9
    When nutrients are introduced into an estuary in excessive amounts
(nutrient enrichment) detrimental effects may result.  Growth of                   •m
phytoplankton may be stimulated, causing dense and unesthetic blooms.  Or,         •
a few species may dominate, resulting in declines of other types and loss
of species diversity.  Although phytoplankton blooms produce photosynthetic        ^
oxygen as they develop, as they die, respiration may exceed                        I
photosynthesis.  Oxygen will be depleted from the water as a result.  In           "•
addition, grazers and decomposers deplete oxygen by respiration as they
process the phytoplankton.  Consequently, oxygen depletion from the  water          M
is a common corollary to nutrient enrichment.  The severity of these               |ง
effects depends on season, rainfall, circulation, and the availability  of
phytoplankton seed stock.                                                          .
    The relationship between nutrient enrichment, phytoplankton growth, and        •
oxygen depletion is fairly direct and well-documented.  Less accepted are          *
indirect relationships between nutrient enrichment and higher trophic
levels, particularly commercial fisheries.  Yet, in Chesapeake Bay,                 B
declines of important fisheries like striped bass, American shad,  blue  crab        V
and oyster have been observed; it would be of great interest to know
whether these declines have resulted from anthropogenic nutrient inputs.            •
Although satisfying conceptual models can be developed in which nutrient           m
enrichment, algal species composition, and competitive/predative fisheries
interactions are related, data for calibration and verification are                 _
scarce.  There appears to be a relationship between nutrient enrichment and        V
another resource, submerged aquatic grasses.  The value of Bay grasses  and         ™
the relationship between their decline and nutrient enrichment will  be
discussed in Part IV on Submerged Aquatic Vegetation.                              ft
    The Chesapeake Bay Program has assessed the nutrients problem in the           ^
Bay from three perspectives:  analysis of historical trends, assessment of
sources, and understanding of processes.  With three separate but  related          M
approaches, the Program can determine the extent and nature of the                 •
nutrients problem and what should be done to alleviate it.
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    Analysis of historical trends in nutrient enrichment is presented in
the first chapter of this part.   Such an evaluation can help assess  whether
a problem exists because it can  establish an historical baseline  against
which to compare present levels.  Ideally, it is desirable to have a
"pristine" baseline, nutrient levels existing before human settlement.
However, it is obviously not possible to obtain such data.  One must settle
for the earliest period for which good data exists, and anecdotal data  for
earlier periods.
    For Chesapeake Bay, the earliest large data base is that developed  by
CBI in 1949-51.  This provides us a baseline for analysis of trends  in  the
past 30 years.  Within the Chesapeake Bay Program,  these trends have been
analyzed by Heinle et al. and will be discussed in  the first chapter.
    In assessing historical trends for a large system like Chesapeake Bay,
it is important that a regional  approach be taken.   For example,  trends in
the Potomac River are quite different from those of the upper Bay.  It  is
also important that nutrient levels be assessed on  a seasonal basis,
because nutrient processes are highly dependent on  season (discussed more
fully in the Processes section).  Finally, fresh-water inflow must be
accounted for, as this can greatly affect runoff rates and dilution  (to be
discussed under Sources).
    Besides establishing a baseline, developing historical trends in
nutrient enrichment provides a source of comparison with trends in
resources like fisheries, submerged aquatic vegetation, etc.  If  declines
in resources can be correlated with increases in nutrients, it is possible
to begin investigating the causal relationships, if such exist, behind  the
correlations.  Comparisons of historical trends are being investigated  in
the Bay Program's Characterization process.
    The movements and transformations of nutrients  in an estuary, called
nutrient processes, are directly related to their potential negative
effects.  Understanding these processes is critical to developing
appropriate nutrient controls.  Nutrient processes  vary in space  and time
(specific examples are discussed in the Processes section), and control
strategies must account for regional and seasonal factors.  Major nutrient
processes include phytoplankton  nutrient uptake, nutrient cycling, and
circulation and are discussed in the second chapter of this part.
    The primary negative effect  of nutrient enrichment is overgrowth of
phytoplankton.  Whether phytoplankton growth occurs as a result of nutrient
addition, and the extent of this growth, depend on  whether the
phytoplankton take up the nutrient and are able to  grow.  A number of
factors affect phytoplankton uptake and growth.  For example, all other
growth requirements of the phytoplankton must be satisfied, such  as
temperature and light.  In general, addition of a nutrient will stimulate
growth only if. that nutrient is  limiting.  Furthermore, some nutrients  are
"preferred" by phytoplankton over others and will be taken up first.
    Uptake of nutrients by phytoplankton does not always result in growth.
Under some conditions "luxury uptake" occurs, in which nutrient is taken up
and stored within the cell.  As  a result, nutrient  depletion from the water
column may be observed without concomitant increase in phytoplankton
biomass.
    Finally, ambient nutrient levels do not always  correlate with high
phytoplankton biomass (as determined by chlorophyll a levels). Nutrients
may be taken up by the cells so  rapidly that they never accumulate in the
                                  38

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water column.   For this reason,  measurement of ambient  nutrient  levels  may         •
not provide a good indication of eutrophication.
    Nutrient cycling is the general term for the  many biological,
geological, and chemical processes by which nutrients change form.   In  the         •
Chesapeake Bay, the most important of these are grazing and decomposition,          w
nitrification and denitrification, and phosphate  binding in the  sediments.
    Grazing of phytoplankton by predators is important  because it  prevents         tf|
accumulation of phytoplankton biomass and may increase  productivity  of              ||
higher trophic levels.   Thus, it can prevent the  negative effects  of
nutrient enrichment.  Because of grazing, high nutrient levels may not  lead         H
to high levels of chlorophyll ฃ.  Whether grazing occurs depends in  part  on         I
the availability of grazers and on the palatability of  the phytoplankton            ™
(e.g., blue-green algae are generally inedible).   Decomposition  of dead
phytoplankton, animals and other organic matter by bacteria and  fungi              •
converts nutrients from their organic to inorganic forms, making them again         4v
available for phytoplankton and other plant uptake.  It is an important
part of the eutrophication process, because the respiration required               ^
depletes oxygen from the water column.                                             •
    Nitrification and denitrification are bacterial transformations  of
inorganic nitrogen forms.  Nitrification is the conversion of ammonia to
nitrite and thence to nitrate.  These conversions require the presence  of          •
oxygen; thus, under conditions of oxygen depletion, ammonia and/or nitrite         IB
may accumulate.  Denitrification, the conversion of nitrate to nitrite  and
thence to nitrogen gas, occurs under anerobic conditions and may be  an              fl|
important mechanism for ridding the system of excess nitrogen.                     •
    The availability of phosphate in the water column depends in part on
processes in the sediments.  Under aerobic conditions,  phosphate complexes         ^,
with iron and manganese and precipitates to the sediments.  Under  anerobic         I
conditions, however, phosphate is released from the sediments into the              '
water column.  Clearly, the cycling of nitrogen and phosphorus compounds  is
dependent on oxygenation, particularly of bottom waters and sediments.  As         •
a result, nutrient activities will be very different in the winter,  when            ^
water is well oxygenated, than in the summer when oxygen depletion of
bottom waters occurs.                                                              ^
    Circulation is a critical component of nutrient processes.  It                 •
determines the spatial distribution of nutrients, as well as that  of the
phytoplankton that would utilize them.  It also affects the availability  of
oxygen to the bottom waters, through the processes of stratification,              fl
mixing, and turnover.  Circulation is discussed in Processes.                      9
    In addition to understanding processes, assessing nutrient sources  is
critical to developing effective controls.  Sources of  nutrients to                 •
Chesapeake Bay include municipal sewage effluents and industrial nutrient          •
effluents (point sources), as well as agricultural, urban and other  land
runoff (nonpoint sources), and atmospheric sources (precipitation).   The            _
third chapter of this part addresses these sources.                                V
    Assessment of nutrient sources is generally accomplished by a                  ™
combination of monitoring and modeling.  Point sources  are routinely
monitored; modeling is used when projections,of future  point source  loads
are made, or when the number of point source effluents  is too great  for
frequent routine monitoring, and expected loads must be calcuated.
    Nonpoint source nutrient loads are much more difficult to quantify.  An
estimate can be made by monitoring nutrient levels in the major tributaries
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entering the Bay (e.g., Susquehanna, Potomac, James Rivers).  However, this
gives no indication of nutrient loads from specific land uses within the
watershed.  That must be determined by monitoring nutrient levels in small
tributaries draining single land use types, and extrapolating to the entire
Bay watershed.  Such nonpoint source modeling is an important technique in
understanding which land uses are the greatest sources of nutrients, and
where controls would be most effective.
    The following chapters were prepared by CBP project investigators and
staff to describe findings of the Nutrients Program and their
implications.  Nutrient Problems (author:  Christopher D'Elia) discusses
historical trends in nutrient enrichment and its effects.  In Nutrient
Processes, Jay Taft discusses the major nutrient processes and how these
events affect the outcome and management of nutrient enrichment.  Finally,
James Smullen and Joe Macknis discuss the relative importance of nutrient
sources.  A final chapter relates these findings to implications for
managing nutrient contributions to the Bay.
    The chapters are organized around a set of management questions:
    1.   Is there a problem with nutrient levels in Chesapeake Bay?
    2.   What are the important processes interacting to create the problem?
    3.   What are thฐ sources, loadings, and losses of the pollutants of
         concern?
A more detailed list of the questions can be found at the end of the
Nutrients part.
                                 40

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aerobic:



albedo:




allocthonous:


anaerobic:

autocthonous:



autotrophic:




bioassay:




biomass:
            Technical  Glossary



Environmental condition characterized by presence of
oxygen.


Relation between amount of light sent back from a dark or
unpolished surface and the amount falling on it, measuring
its power of reflection.


Material coming from outside; not produced internally.


Environmental condition lacking oxygen.


Originating in location where found, e.g., Bay
phytoplankton vs. river plankton washed into the Bay.


(Of plant) building up its food from simple chemical
substances, not using or not dependent on ready-made plant
substances, living or dead.


The measuring of power of substances by their effects on
organisms, e.g., toxic power of a heavy metal or organic
pesticide.


The total mass or amount of living organisms in a
particular area or volume.
biostratigraphy:  Method used by geologists to analyze layers and fossil
                 remains.
brackish:



chironomids:



coprophagy:
Somewhat salty, as the waters of some marshes near the sea
or waters near the head of the Bay.


Midges, a class of mosquito-like insects; typically refers
to their larvae found in fresh to brackish Bay sediments.


The act of taking excrement as food.
electronic planimeter:  Instrument for measuring the areas of plane curved
                 forms.


epiphytes:       Plant fixed to another plant but not dependent on it for
                 food, using the host plant primarily as a substrate.


etiolation:      Condition of a plant which is feeble and without normal
                 green color through not getting enough light.


euphotic zone:   The upper zone of a sea or lake into which sufficient light
                 can penetrate for active photosynthesis to take place.
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eutrophication:
Natural or artificial addition of nutrients to bodies of
water that results in increased plant biomass and
typically low levels of dissolved oxygen during advanced
stages.
Fickian diffusion:   Diffusion of a substance through a unit  area  at  a  rate
                 dependent upon concentration differences  over  a  defined
                 distance.


Gelbstoff:       "Yellow substance" found dissolved in seawater,  believed
                 derived from decomposition products of plants, especially
                 carbohydrates, in the presence of amino acids  to form
                 humic materials.


ground truth surveys:  Technique to verify photographic interpretations.
Hill reaction:
isopod:






littoral zone:





meristic:



oligochaetes:






phytoplankton:





plastoquinone:



polychaetes:
Part of photosynthesis involving light reactions within
the chloroplast; fundamentally, splitting of a water
molecule resulting in the evolution of oxygen through
action of light on plant chloroplast.  First stage in
photosynthesis named after discoverer.


Crustacean without a hard cover, having a body commonly
flat and made up of six or more divisions with legs used
for walking, and eyes with fixed or no stems.  Typically
small in length (5 - 20 mm), living on and in sediments.


That part of the edge of the sea between high- and low-
water mark or a little further out, as the living place of
certain sorts of animals and plants.


Involving variation in number or geometrical relation of
body parts, e.g., a variation in flower petals.


Animal without a clearly marked head and with only a small
number of chaetae on every body division, hermaphrodite,
and living in earth or inland water, for example, the
earthworm.


Plants, most of which are very small, living in the water
of seas, rivers, etc., chiefly near the top, and moving
freely with it but having little or no power of swimming.


Lipoidal compound localized in subcellular organelles and
functioning as coenzymes in electron transport.


Animals having a great number of stiff hairs, a
well-marked head with special outgrowths.  Sea animals in
which the sexes are seaparate and the uniting of sex cells
takes place outside the body.
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post-veliger larvae:   Characteristic ciliated larvae whose free-                   •
                 swimming existence has changed to one of settlement to the
                 bottom and attachment to a firm surface.                          _

regression analysis:   Mathematical method of fitting an equation to data,           ™
                 usually expressed as the change in a y - variable
                 (dependent) relative to unit change in an x - variable            fl[
                 (independent).                                                     |i

spectral attenuation coefficient:   A number multiplier that expresses the           •*
                 diminuation of  part of the light spectrum as the light            •
                 energy passes through water.

spectrophotometer:   An instrument  used for measuring the intensities of            B
                 light of different wave-lengths in a spectrum.                    9

substrate:       That substance  on which an enzyme has the power of acting.        m

topographic quadrangles:  A section of a topographic map seven and  a half
                 by seven and a  half minutes, at a 1:24,000 scale.
2-4D:            2,4, dichlorophenoxyacetic acid:   synthetic compound used
                 as a weed killer in agriculture.
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BOD
C
CFSD
chl ฃ
COD
d
DIP
DN
DP
h
Ks
L
m
ug
ug atom
MGD
ug/L
urn
N
NH3 4
N02*
N03
N02 3
POTWs
ppm
ppt
OP
Q
RQ
sec
SED
TKN
TN
TP
Vmax
TECHNICAL SYMBOLS
— biological oxygen demand
— carbon
— cubic feet per second daily
— chlorophyll ฃ
— carbon oxygen demand
— day
— dissolved inorganic phosphate
— dissolved nitrate
— dissolved phosphorus
— hour
— half saturation value
— liter
— meter
— microgram
— microgram atom
— million gallons per day
— micrograms per liter
— micrometer
— nitrogen
— ammonium
— total ammonia nitrogen
— nitrite
— nitrate
— total nitrite plus total nitrate nitrogen
— oxygen
— phosphorus
— phosphate
— publicly owned treatment works
— parts per million
— parts per thousand
— orthophosphorous
— mean daily discharge
— respiratory quotient
— second
— suspended sediment
— total Kjeldahl nitrogen
— total nitrogen
— total phosphorus
— maximum uptake velocity
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              CHAPTER 1
NUTRIENT ENRICHMENT OF CHESAPEAKE BAY:
      AN HISTORICAL PERSPECTIVE
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                      by                                            |
            Christopher F. D'Elia                                   ฃ
            University of Maryland
Center for Environmental and Estuarine Studies
       Chesapeake Biological Laboratory                              •
           Solomons,  Maryland 20688                                  ป
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                                  CONTENTS

Figures ...............................     47
Tables  ...............................     49
Sections

    1.  Introduction  ........................     50
          Overview of Nutrient Enrichment  ..............     50
          Sources of Nutrients  ...................     51
    2.  Consequences of Nutrient Enrichment  .............     52
          Fate of Added Nutrients ..................     52
          Responses to Increased Loadings  .....  .........     55
          Nutrient Enrichment and Algal  Growth  ...........     58
    3.  Evaluating Nutrient Encrichment  Problems
         Indicators of Nutrient Enrichment   .............     60
              Primary Indicators ...................     60
                   Nutrient Concentrations   .............     60
                   Oxygen Concentrations ...............     60
                   Secchi Depths ...................     60
                   Chlorophyll ฃ Concentrations  ...........     61
                   Algal Species Shifts  ...............     61
         Techniques for Evaluating Nutrient  Enrichment ........     61
              Water Quality Indices .................     62
              Water Quality Models  .................     62
              Other Techniques  ...................     65
    4.  Historical Trends in Nutrient Enrichment   ..........     66
          Trend Evaluation (by W. Boicourt)  .............     66
          Trends by Region  ..............  .  ......     67
              Upper Bay and Western Shore Tributaries  ........     67
              Middle Chesapeake Bay .................     gy
              Lower Bay .......................     90
              Eastern Shore Tributaries  ...............     90
    5.  Summary and Conclusions ...................     94
Literature Cited
                                     46

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  1 Scheme of possible effects of enrichment in a stratified
     water column	.53

  2 Simple one compartment box model of an estuary	.54
*15 Concentrations of chlorophyll ฃ (by month) in the lower James
     River, Virginia  	    86
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                                   FIGURES
Number                                                                Page

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  3 Binary dendogram showing possible responses of the water
     column to increased nutrient loadings  	 56         •

  4 Regions of Chesapeake Bay	68

* 5 Ranges of concentrations of orthophosphate-P observed during                   •
     studies of the upper Chesapeake Bay	70

* 6 Ranges of concentrations of nitrate plus nitrite-N observed                    •
     during studies of the upper Chesapeake Bay 	 71

* 7 Concentrations of orthophosphate-P in surface waters of the                    •
     Patuxent River upstream and downstream of Benedict Bridge versus               J|
     time of year	72

* 8 Concentrations of nitrate in surface waters of the Patuxent                    •
     River upstream and downstream of Benedict Bridge versus time
     of year	75

* 9 Secchi depth during July in the Patuxent estuary versus salinity  •  • 77         •

*10 Weekly maximum and minimum concentrations of dissolved oxygen                   •
     at Benedict Bridge in the Patuxent estuary during 1964 and                    ฃ
     1977	    79

 11 Bottom dissolved oxygen concentration in the lower Patuxent                    •
    River during July and August 1978 to 1980 versus a stratifi-
    cation parameter (AS — surface to bottom salinity difference)  .  . 80

*12 Concentrations of dissolved oxygen in bottom waters of the                     V
     Patuxent River estuary during July, 1936 to 1940 and July,
     1977 to 1979	   82         tt

*13 Concentrations of orthophosphate-P (by month) in the lower
     James River, Virginia	    84         M

*14 Concentrations of nitrate-N (by month) in the lower James River,                ™
     Virginia	    85
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FIGURES (Continued)
Number

*16 Monthly mean concentrations of orthophosphate-P ("soluble
reactive phosphorus") in the surface 10m at mid-Chesapeake

*17 Concentrations of chlorophyll a at 0 to 10m and 0 to 30m depth


*18 Daytime concentrations of dissolved oxygen (D.O.) in surface


19 Nitrogen: Phosphorus ratios (dissolved inorganic nutrients
only) in surface and bottom waters of the Choptank River,
1980 	

*20 Map showing portions of Chesapeake Bay that are moderately
or heavily enriched according to the criteria of Heinle et
al. (1980) 	

*21 Map showing portions of Chesapeake Bay where natural
regimes of dissolved oxygen appear to have changed ......

Figures marked with an asterisk (*) are originals presented in the
by Heinle et al. (1980).








48



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91





. . . 95


. . . 96

report











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TABLES
Number Page
1 Classification Scheme for Nutrient Enrichment in
Estuaries by Neilson (1981) ........ 	 63
2 Neilson's (1981) Chart Showing Impacts of Nutrient Enrichment
3 Examples of Natural Cycles Affecting Chesapeake Bay's
•ซr
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                                  SECTION 1

                                 INTRODUCTION
    The following paper deals with historical changes in the nutrient
enrichment of Chesapeake Bay and its tributaries.   In the present  context,
"historical changes" refer to those changes that have occurred primarily in
the last several decades during which we have data.   "Nutrient enrichment"
refers to the addition of nitrogen and phosphorus  compounds to bodies of
water, and in excess can lead to phytoplankton blooms,  loss of oxygen,  and
changes in fisheries species composition.  Each section of the report
contains an important topic relative to nutrient enrichment and discussions
of the following Chesapeake Bay Program (CBP) management questions:

    o    Where and how severe are nutrient enrichment problems in  the Bay?
    o    What are the consequences of nutrient enrichment?
    o    What are the commonly used criteria for evaluating a water  quality
         problem related to nutrient enrichment, and what are their
         advantages and disadvantages?
    o    What techniques can be used to evaluate or predict nutrient
         enrichment problems?
    o    What are the historical trends in nutrient enrichment?
    o    What addditional research needs to be done?
    This paper draws heavily on a previous report  to the EPA/CBP by  Heinle,
D'Elia, Taft, Wilson, Cole-Jones, Caplins, and Cronin (1980).  That  report,
entitled "Historical Review of Water Quality and Climatic Data from
Chesapeake Bay with Emphasis on Effects of Enrichment," should be  consulted
by readers interested in greater detail about historical changes in  water
quality as they relate to anthropogenic and natural causes.
OVERVIEW OF NUTRIENT ENRICHMENT IN CHESAPEAKE BAY

    There is little doubt that there are nutrient enrichment problems in
Chesapeake Bay and its tributaries; however, there is doubt as to how
extensive the problems are, and how rapidly environmental degradation is
occurring.  Human population growth in the Chesapeake Bay area has resulted
in increased nutrient loadings from point (sewage) and non-point (runoff)
sources.  These increased loadings have had their greatest effects in the
tributaries nearest the centers of demographic development, such as the
tidal freshwater portions of the Potomac River near Washington,  DC, where
point source loadings from municipal sewage treatment plants had noticeable
effects early in this century (Gumming 1916, Gumming et al. 1916).
Although earliest concerns focused on problems of human health and
sanitation, it was nonetheless recognized that the input of untreated
sewage to the Potomac caused oxygen depletion in receiving waters.
Blue-green algal blooms were observed in the upper Potomac estuary as early
as 1916 (Gumming et al. 1916).  By the mid-1960's sewage inputs  in the
tidal freshwater portion of the Potomac sufficiently enriched the water
with nutrients, and blue-green algae became a serious problem (Jaworski et
al. 1971b).
                                   50

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    Other tributaries of the Chesapeake also show signs of nutrient
enrichment.  The upper Bay near Baltimore, MD, and the upper James near
Richmond, VA, are quite enriched.  Also enriched,  but to a lesser extent,
are the York, Rappahannock, Patuxent,  and Susquehanna Rivers.   Of these
moderately enriched tributaries,  the greatest data base exists  for the
Patuxent River and estuary.  This excellent data base extends back to the
mid-1930's and is one of the older and more complete data bases for any
estuary in the world.  For that reason, and because the estuary seems to be
undergoing continuing change (dissolved inorganic  nutrient levels are
rising, and transparency and deep water dissolved  oxygen concentrations are
decreasing), much of the following data analysis and discussion deals with
the Patuxent River.  Furthermore, changes occurring in the Patuxent River
could also occur in the main Bay and other tributaries if enrichment in
these areas increases.  The Patuxent River can be seen as an analog of  the
main Bay and of other western shore tributaries (Klein, unpublished).
    Background information on nutrient enrichment  and its relationship  to
algal growth is provided below to help underscore why the problem of
nutrient enrichment is complex and difficult to assess in light of data
gaps in the historical record.  This report avoids the use of the term
"eutrophication" because its meaning can be ambiguous and unclear.
SOURCES OF NUTRIENTS

    Nutrient inputs to estuaries come from "point" sources,  such as sewage
treatment plant effluents, and "nonpoint" or "diffuse" sources such as
runoff from the land.  Increases in loadings from both point and non-point
sources have occurred in the Chesapeake Bay region.   As population
increased and urbanization occurred, particularly in the last two decades,
sewage treatment plants were constructed.  Nutrients that would otherwise
have been applied over the land or contained in home septic  systems were
combined and discharged at points along the rivers.   Sewage  treatment plant
construction was accelerated after the grant program established in the
1972 Federal Water Pollution Control Act (PL92-500)  was adopted.  As a
result of the move toward centralized treatment, large increases in total
amounts of nitrogen (N) and phosphorus (P) from human wastes discharged to
the Chesapeake Bay system have occurred.  Brush (1974) summarized the
sewage discharges to the Bay in 1973, and EPA/CBP recently completed a
revised inventory.  Details of the CBP inventory of  sewage discharges are
found in the last chapter of this part.
    In contrast to point sources that are solely attributable to human
activities, diffuse sources may be natural, or result from human
activities.  Native, undisturbed ecosystems, such as forests, are natural
nonpoint sources.  Agricultural or urban runoff accounts for much of the
anthropogenic diffuse loadings.  The importance of nonpoint  sources depends
on season.  For example, in the spring, loadings from nonpoint sources are
by far the dominant source of nitrogen to the Bay system (Smullen et al.
1982).  The CBP Modeling Study (Hartigan, unpublished) relates land use to
nonpoint source loads.  Sources of nutrients and historical  changes in
loadings are discussed in depth by Heinle et al. (1980) and  in the last
chapter of this part.
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                                  SECTION 2
                     CONSEQUENCES OF NUTRIENT ENRICHMENT

    The task of enumerating the most important consequences  of  enrichment
in estuarine systems is yet incomplete,  because the consequences  of
nutrient enrichment of freshwater environments are  much better  understood
than for brackish or saline ones.  The theme of a recent  symposium (Neilson
and Cronin 1981) was the enrichment of estuaries with nutrients.   Many  of
the papers in the symposium deal directly with Chesapeake Bay.  For
example, Webb (1981) formulated a conceptual model  of an  estuary's response
to nutrient enrichment in his review paper.   His conclusions state that
small additions of nutrients increase overall production, with  increased
biomass showing up at any trophic level.  Large increases produce changes
in species composition at all trophic levels.  Interested readers should
consult Webb's review for further details.
    The consequences of enrichment in estuaries are more  difficult to
assess than those in fresh waters, because estuaries are  generally subject
to more complex hydrodynamic processes.   Also, the  effects of salt on
biological and chemical processes have no analogues in fresh waters.
However, there appear tc be certain consequences that ui.u at least
qualitatively similar for all water bodies that are nutrient enriched.
Figure 1 presents a scheme of probable consequences.  As  shown, one
consequence is that plant productivity is enhanced  by higher concentrations
of nutrients in the water.  Levels of organic matter contained  in the water
column in turn often increase, although enhancement in the rates  of  other
processes may counterbalance the increase to some extent. Organic matter
produced in the water column may accumulate in deep water where its
degradation results in an oxygen deficit that is not balanced by
atmospheric input.  The Chesapeake Bay is characteristically two-layered;
there is a natural, seasonal isolation of deep water from potential
atmospheric oxygen inputs.  Oxygen consumed during  the oxidation  of  extra
organic matter produced by enrichment may not be replaced in the  lower,
isolated layer, resulting in an oxygen imbalance uncharacteristic to the
natural system.  Most estuarine organisms of direct interest to
humans—fish and shellfish, for example, require oxygen;  they will either
swim away from uncharacteristically low oxygen water or will perish.
FATE OF ADDED NUTRIENTS

    An aquatic system can respond to nutrient enrichment in a variety of
ways.  If one views such a system as a compartment or a series of
compartments, as mathematical modelers often do,  one can more easily
conceive of the ways in which responses might occur.  Figure 2 shows a
simple compartmental representation of an estuarine system:   a single
compartment with a series of exchanges or fluxes  across the compartment
boundaries.  The simplest approach to understanding the nutrient  mass
balance of such a system, is to measure the amount of a given nutrient
within the compartment and estimate the fluxes and exchanges of that
nutrient between the compartment and the outside.  The amount of  nutrient
contained in the box after a given time interval  is a function of the
amount, or "standing stock," of nutrient in the box at the beginning of the
interval, less the amount lost over the interval, plus the amount gained
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                                                                   I
                        INCREASED                                  I
                     NUTRIENT INPUTS
                        INCREASED                                   m
                        NUTRIENTS                                   I
                     IN WATER COLUMN
                            ^^                                       ^^^

                        INCREASED                                   I
                      ALGAL GROWTH
                     IN WATER COLUMN                                |
                  DECREASED CLARITY AND
                                                       I
 INCREASED PARTICULATE  ORGANIC                        ff
   LEVELS IN WATER  COLUMN                             •
               \                                       I
SETTLING OF PARTICULATE ORGANIC
     MATERIAL TO DEEP WATER                           |
              DECAY OF PARTICULATE ORGANIC                          •
                MATERIAL AND DECREASE  IN                            m
                      OXYGEN LEVELS                                 •
                      IN DEEP WATER                                 -
Figure 1.   Scheme of possible effects of enrichment  in a stratified
water column.
                          53
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SYSTEM RESPONSES TO INCREASED LOADS
                                 55
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over the interval.  Clearly this "black box" approach to understanding an          |
estuary has a number of deficiencies.   For example,  it tells us  nothing
about the internal partitioning of specific nutrients of interest,  or about         _
the biological response in the estuary to a change in a nutrient input or          •
loss.  We know only whether the total  amount of nutrient in the  compartment         *
changes.
    Understanding internal nutrient partitioning is  essential if we are to         •
increase the complexity of our model to account for  internal responses of          0
an estuarine system to changes in loadings or losses.  Only in the  last few
years was any attempt made to assess sediment-nutrient exchanges in the            M
Chesapeake.  It is now known that they are of appreciable importance.  For         •
example, during the summer, the sediments are the greatest source of
phosphorus in most of the Bay system (Smullen et al. 1982).  Until
recently, very little emphasis was placed on collecting any information            •
other than on internal compartmental nutrient concentrations.  The  focus on         9
point-in-time measurements leaves the historical record grossly  deficient
in process-oriented measurements of fluxes, exchanges, and trans-                  M
formations.  Although it is possible to infer from differences among               •
point-in-time measurements that changes occurred in the compartment, it is
difficult to attribute those changes to a specific cause, unless exchanges
that were not measured are assumed to remain constant during the interval          •
between measurements.                                                              9
    Chesapeake Bay bears little resemblance to the simple one- compartment
system represented in Figure 2.  An estuary by definition is a place where         •
sea water and fresh water mix to produce a range of intermediate                   M
salinities.  Provisions must be made in a model to account for this
characteristic, and to understand how Chesapeake Bay might respond  to
continued increases in nutrient loadings.  Model complexity increases              •
greatly when one attempts to include provisions for time-varying phenomena         9
such as intra- and interannual changes in loadings,  losses, and
hydrodynamics.  Modelers dealing with the Bay and other estuarine systems          •
have been struggling to determine what level of complexity is necessary to         •
include in their models (e.g., Harleman 1977; O'Connor 1981).
                                                                                   I
    What are the possible responses of the Chesapeake Bay system to                 A
increased nutrient loads?  Figure 3 presents a chart showing the possible           ||
response of the water column to increased levels of nutrients.  For
simplicity, we can assume that the single compartment conceptual model              ^
given in Figure 2 represents the water column to which additional loadings          •
are applied.  Figure 3a expands the single compartment into                         ~
subcompartments, reflecting partitioning at four levels.  The partitioning
scheme is given to show the major pools into which added nutrients must go,         •
or pass through.  Increased loading would manifest itself at level "i" as           0
higher levels of nutrients in the water column, as enhanced rates of
nutrient loss from the system, or as a combination of both.  It is possible         A
for the internal nutrient content of any compartment to remain constant             •
over a period of years in the face of increased nutrient loadings, if
increases in net losses from the compartments keep pace with increases in
net inputs.  There is no assurance that increased loadings will necessarily         V
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be manifested in increases of the contents of any particular compartment.           ™
Although the scheme developed in Figure 3 is constructed as  a binary
dendrogram, an "either....or" situation is not necessarily implied,  as              B
added nutrients may result in either of the binary choices or in  some               •
intermediate of the two.
    The historical record  for Chesapeake Bay lacks information on a  number          A
of the pools shown in Figure 3,  and on the specific transformation                 •
processes and rates affecting them.  However, quite good catch records  have
been kept by local authorities on harvestable fish species,  providing  some
information on partitioning of fisheries between commercially desirable and         II
undesirable species (level iv).   From these records, Heinle et al. (1980)           ||
present evidence that the  partitioning to commercially less desirable  and
undesirable species has increased in recent years.  Unfortunately, little           g|
is known, even now, about  food chains leading to the production of                 •
desirable species.  Factors such as climate can play an important role
regulating the abundance of estuarine fish stocks.
    To explain the changes in fisheries partitioning between desirable  and          •
undesirable species, it is necessary to examine the previous hierarchical           ™
level (level iii), the partitioning of added nutrients between biotic  (here
signifying "living") and abiotic particulate material.  The historical              A
record is poor on both the absolute quantities and the partitioning  ratios          •
of nutrients in particulate material.  Fortunately, however, the  historical
record does include a considerable amount of information on transparency of
the water as determined by Secchi disk.  Transparency is affected by the           •
amount of particulate matter in the water.  This particulate matter  is              9
composed of inorganic material (clays, silts, etc.), non-living organic
detrital material, and living material.  There is convincing evidence  that          A
in certain places on the Bay, such as near the mouth of the Patuxent River,         ฃ
transparency as measured by Secchi disk has declined in the last  40  years.
This suggests that the amount of organic material and, by inference,               —
organically bound N and P in the water column, have increased.  Turbidity           •
derived from inorganic material may have increased also.                           ™
    Increased biotic particulate material results from increased nutrient
levels in the water column partitioned between the dissolved and                    •
particulate forms.  Because there is no way to measure how much N and  P are         jf
contained in living material relative to detrital material,  it is of
interest to examine the partitioning of nitrogen and phosphorus compounds            ^
(level ii).  The total phosphorus in the water column is composed of                •
dissolved inorganic phosphorus, dissolved organic phosphorus, and                  ™
particulate phosphorus.  Of these, the historical record contains
substantial information on dissolved inorganic phosphorus only.  Total               B
nitrogen is composed of dissolved inorganic nitrogen (nitrate plus nitrite           V
plus ammonium), dissolved organic nitrogen, and particulate nitrogen.
Analytical techniques for the identification of all forms of nitrogen                tm
existed in the 1930's but were unreliable, especially for ammonium.  Heinle          •
et al. (1980) found no data on levels of particulate or dissolved organic
nitrogen anywhere  in the Bay prior to the 1950"s.  This represents an
enormous gap in the data record for these forms of nitrogen.  For this               •
reason we have very little understanding of what the historical                     ™
partitioning of dissolved versus particulate nutrients in the Bay was,  and
how this may have  changed in response to increased loads.                           •
    Increased loading will manifest itself as higher levels of nutrients in          •
the water column,  as enhanced rates of nutrient loss from the system,  or as
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3 Combination of both.   Increased nutrient loadings to the water column of
the Bay, not accompanied by increased nutrient losses to the atmosphere and
sediments, will result in increased nutrient levels in the water column.
It appears that, on an annual basis,  sediments do not absorb more nutrients
than they release (Smullen et al. 1982).   We can assume that additional
loadings will not result in equivalent additional losses,  and that
nutrients entering the water column will  remain there and  be manifested as
a corresponding increase in dissolved nutrients, particulate nutrients, or
some other compartment shown in Figure 3.
    Although quantity and partitioning data can yield information about
historical changes in the distributions and standing stocks of nutrients in
the system, they yield little knowledge about the internal dynamics of the
system that cause the changes.  The next section addresses the internal
dynamics briefly; for more information refer to the following chapter by
Taft.
NUTRIENT ENRICHMENT AND ALGAL GROWTH

    The addition of nutrients to an aquatic system frequently enhances
algal "specific growth rates" (increase in biomass per unit biomass).
"Nutrient sufficiency" occurs when algal specific growth rate is not
stimulated by further nutrient addition; "nutrient limitation" occurs  when
algal specific growth rate is restricted by the availability of nutrients.
"Algal productivity," that is, the rate at which new organic material  is
being produced per m^ by plants, is a function of both specific growth
rate and biomass.  Systems can exhibit very high specific growth rates,  and
the algae can be nutrient-sufficient, although the productivity per unit
area is low (systems can exhibit very high rates of productivity without
producing nuisance levels of algal biomass).  Implicit in this is that the
biomass or standing stock of algae, although growing at a very fast rate,
is low, resulting in a low level of production.  In other words, what
material is present is growing fast, but there is not very much of it
present to grow.  The converse is also true.  A rather high level of
production (that is, increase in algal biomass) occurs when large
quantities of slow-growing algae are present.  The situation is reminiscent
of a bank account earning interest.  The interest rate is analgous to  the
growth rate, and the principal is the biomass.  The increase in principal
per time is the analogue of productivity—the highest rate of increase in
principal will occur when the interest rate and the principal are both high.
    An important distinction to make is that between "net" and "gross"
productivity.  Gross primary productivity is the total rate of organic
production by photosynthesis, irrespective of accompanying consumption of
organic material by respiration.  Net primary productivity is the rate of
accumulation of organic material in excess of its consumption by
respiration.  In the bank account analogy, the principal in the account
will only grow at its fastest rate when no withdrawals are made, and there
are no bank charges.  When the withdrawal rate or bank charges equal the
interest rate, principal does not grow.  Unlike bank accounts in which we
want the highest possible increase in principal with time, in aquatic
systems there comes a point at which the accumulation of organic matter
becomes dangerously high.  Nuisance levels of organic matter build
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up only when the rate of production of organic matter exceeds  its rate of          I
consumption.  Standing stocks of algae can be held at continuously low
levels and still exhibit high productivity if what is produced is consumed
as quickly as it is produced.                                                      •
    Systems where nutrient enrichment problems are greatest are usually            •
those in which the levels of production are greatest and out of balance
with consumption.  Implicit in this is that high levels of biomass                 •
accumulate, and what is produced is not removed quickly.  Large                    •
accumulations of biomass—organic matter representing high biochemical
oxygen demand (BOD)—are often responsible for oxygen depletion from the           _
water column and other negative effects we associate with over-                    •
enrichment by nutrients.                                                           ™
    Systems that exhibit high rates of productivity, but in which little
organic material or biomass accumulate, also exhibit high rates of nutrient        •
recycling or throughput.  In such systems, N and P atoms resident in the           ฃ
systems may "turn over," or pass through organisms in a matter of hours.
There are very few "new" atoms of N and P entering the system from                 A
outside.  On the other hand, systems that quickly accumulate organic               •
material or biomass, exhibit low rates of turnover and generally high rates
of nutrient addition, without correspondingly high rates of removal.  In
its pristine state, Chesapeake Bay probably fell more into the category of         flt
a high productivity system in which standing stocks of organic material or         W
biomass did not accumulate as much as they do now.  Decreases  in
transparency as represented by Secchi depth probably signify the                   m
accumulation of organic matter, and it is this organic matter  that can             •
decay and use up oxygen to create a problem.
    The important point to note from the above discussion is that increased
loadings may result in greater rates of algal production or nutrient uptake        •
without increasing standing stock of either; that is, the algae or                 ™
additional nutrients are removed from the system as fast as they are
produced or added.  A truly adequate historical assessment of  nutrient             •
enrichment effects should assess both standing stocks and process-oriented,        ฃ
flux rate measurements.  Unfortunately, in the present case, the historical
record is heavily weighted toward measurements of individual parameters of         M
standing stock, and it will not be possible to adequately consider the             I
changing dynamics of the system.  Therefore, enrichment- related changes in
the system not observably affecting standing stocks will not be discernible.

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                                  SECTION 3

                   EVALUATING NUTRIENT ENRICHMENT PROBLEMS
INDICATORS OF NUTRIENT ENRICHMENT

    The traditional approach to assessing enrichment in an estuary relies
on both primary and secondary indicators of nutrient enrichment.  "Primary
indicators" of nutrient enrichment are typically the first indicators used
in assessing enrichment.  They are not necessarily the best indicators, but
are the ones for which this historical record is most complete.  "Secondary
indicators" are those that have potential value in assessing enrichment,
but are secondarily used.  Some of the major primary indictors are nutrient
concentration, 02 concentration, Secchi depth, chlorophyll a, and algal
species shift.  Secondary indicators include Measurements of dynamic
processes such as primary productivity and nutrient flux rates, and other
nutrient concentrations, pH, bacteria, BOD, and COD.  These indicators will
not be discussed in this section.

Primary Indicators

Nutrient Concentrations—
    Virtually any water quality assessment program will include
determination of nutrient concentrations in the system of interest.  The
most commonly measured nutrient forms are nitrate, nitrite, ammonium, and
phosphate.  They are of analytical interest, because they are the
"fertilizer" nutrients most often responsible for the growth of aquatic
plants.  They also indicate the amount of N and P in the water column
readily available to support algal growth.

Oxygen Concentrations—
    Most water quality assessment programs also provide for dissolved
oxygen determinations.  Oxygen is probably the most crucial water quality
parameter.  Low oxygen tensions occur as the result of the oxidation of
organic material without adequate physical means of oxygen resupply (that
is, reaeration).  Because commercially important species require oxygen, we
are concerned with the effect of the accumulation of organic matter
released from sewage outfalls, or produced by algae in response to nutrient
enrichment on oxygen concentration.  Fortunately, for analysis of trends,
the historical record for oxygen concentrations in Chesapeake and its
tributaries is good, particularly for the Patuxent River.

Secchi Depth—
    The Secchi disk has been used for decades to measure the transparency
of water bodies and to make inferences about levels of organic material and
algae present in the water.  Secchi depth (the depth to which the disk can
be lowered and still be visible) is greatest in water of the greatest
transparency.  Secchi depth tends to be reliably determined from operator
to operator, and the historical data record is quite good, although Secchi
depth does not differentiate between turbidity from algae and other
materials present such as suspended sediments, detritus,  and other
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particulates.  Also, Secchi measurements are rather imprecise in extremely         (ง
turbid systems.

Chlorophyll a_ Concentrations—                                                     •
    Chlorophyll a is a reliable indicator of algal biomass and can give a
general indication of the standing stock of phytoplankton present in the
water column.  The measurement of chlorophyll did not come into wide               •
practice until the early 1960's,  and since then,  methods for measurement           V
have evolved considerably.  Measurement of chlorophyll levels over the next
several decades will probably be  more widely used in documenting changes           •
than it has been over the last several decades.                                    M

Algal Species Sh'ifts—
    Many water quality studies have also involved collecting phytoplankton         B
samples for identification.  In fresh waters, under highly enriched                V
conditions, the species composition often changes toward a dominance by
blue-green algae.  Such shifts have been observed in the upper Potomac             M
River near Washington, DC, but are not generally observed in the saline            •
waters of the Bay.  It is not widely appreciated that marine and estuarine
nutrient enrichment does not involve a shift in species composition toward
blue-greens.  Therefore, blue-green algae are not considered good indictors        •
of nutrient pollution in saline systems.                                           *•
    A great difficulty encountered when attempting to examine the
historical data record for shifts in phytoplankton-species composition, is         •
the evolution of sampling and counting methods for phytoplankton.  In the          ฃ
1950's oceanographers began to appreciate that 35 to 50 urn mesh (or
greater) nets traditionally used  to sample for phytoplankton in the ocean,         ^
were not catching the smaller-diameter algae responsible for the bulk of           •
photosynthesis.  Phytoplankton sampling on Chesapeake has been no                  ~
exception.  Early workers used nets and, therefore, their results do not
include counts on important, smaller species.  McCarthy et al. (1974)              B
verified that the smaller phytoplankton on Chesapeake do indeed account for        m
most of the primary productivity.  Thus, comparison of phytoplanktonic-
species composition with time must be done carefully.                              m


TECHNIQUES FOR EVALUATING ENRICHMENT OF ESTUARIES

    Evidence in Chesapeake Bay historical data base indicates that changes         ™
have occurred in nutrient concentrations, oxygen levels, and Secchi depths
in parts of the Bay.  These changes seem to have resulted from increased            •
nutrient loadings in the last twenty years.  One must understand that               f
"historical" here refers to relatively recent history, that is, the last
several decades for which we have data.  Anthropogenic changes in the               ^
system may have occurred prior to collecting and recording of detailed              •
data.  Other kinds of ecological evidence, particularly on rates of                 *
production, consumption of organic matter, nutrient exchanges, and other
factors, would also be useful in assessing enrichment effects.  Such data,          •
however, are obtained by relatively modern techniques and are difficult to          w
compare because of inconsistent methodologies.  This section contains a
discussion of  techniques developed previously for evaluating enrichment in          M
fresh waters;  these techniques evaluate the state of enrichment and predict         •
changes in water quality in response to nutrient loadings.
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Water Quality Indices

    Managers, when faced with the responsibility of evaluating and
improving the "water quality" of an estuary,  often turn to water quality
indices to assess the current water quality.   What is an index?  Thomas
(1972) describes an index as a "composite value for an environmental
component for which we have more than one indicator."  Ott (1978) defines
an index as any "mathematical approach which  aggregates data on two or more
water quality variables to produce a single number."  Pikul et al. (1972)
consider an index "a mathematical combination of two or more parameters
which has utility in an interpretive sense."   McErlean and Reed (1981) have
reviewed the use and application of indices to estuaries,  and have
concluded that lack of success of transferring counterpart freshwater
indices to estuaries is attributable to three reasons:  (a) the lack of an
exact and widely accepted definition of estuarine "eutrophication"; (b) a
basic lack of knowledge of nutrient limitation and cycling in estuaries;
and (c) possible fundamental differences between estuaries and other water
bodies which invalidate transfer attempts. Other scientists have been
critical of indices because they oversimplify complex ecological
properties; they are biased in their formulation; and they do not clearly
associate cause and effect between nutrient enrichment and response of
plants and ecosystem level changes.
    Two projects supported by the EPA/GBP were conducted to review the
applicability of existing indices and to develop new water quality indices
for the Bay.  McErlean and Reed (1979) proposed the use of five indices in
estuaries.  Four were selected from the available literature, and one was
developed by the authors.  The four previously developed indices were the
National Sanitation Foundation Index (NSFI) by Brown et al. (1970), the
Minimum Operator (MO) or Water Pollution Index (Ott 1978), the Principal
Nutrient Index (PNl) by Olinger et al. (1975), and the Beta Function Index
(BFI) developed by the State of Illinois.  McErlean and Reed's index is
entitled "Estuarine Index of Enrichment" or EIE.  The second project was
that of Neilson (1981), who developed a use-oriented rather than a general
index of enrichment.  Table 1, as an example, presents the simple indicator
criteria that constitute Neilson1s index.  Table 2 shows the use-related
interpretations of indicator values that he has employed.
    The use of indices in summarizing data from monitoring programs may
serve to identify areas that are changing, or are in need  of closer study.
Indices may be of great value in the indentification of danger zones where
close scrutiny by scientists and managers is  required.

Water Quality Models

    Another approach to dealing with environmental problems associated with
excessive nutrient enrichment is to formulate and develop  models that are
mathematical constructs attempting to represent numerically some key
features (for example, chlorophyll, oxygen concentration,  nutrient
concentration) of ecological systems affected by nutrient  enrichment.
EPA/CBP is making extensive use of such models.
                                 62

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                                                                                   I
TABLE 1.  CLASSIFICATION SCHEME FOR NUTRIENT ENRICHMENT  IN ESTUARIES
          (FROM NEILSON 1981)

Level of Nutrient
Enrichment
0
1
2
3
4
5
6
7
8
9
10
Total Nitrogen
mg/1
0.003
0.010
0.032
0.100
0.320
1.000
3.200
10.000
32.000
100.000
320.000
Total Phosphorus
mg/1
0.0004
0.001
0.004
0.014
0.044
0.140
0.440
0.400
4.400
13.800
44.000

                                                                                   I
                                                                                   I
                                                                                   I
                                                                                   I
                                                                                   I
    Numerical water quality models have proved to be successful in                  ™
representing the operation of some sewage treatment plants and in
representing rivers, streams, and lakes in which hydrodynamic factors are           •
relatively simple and easy to simulate mathematically.   Such models have            9
typically been "steady-state," that is, those in which  boundary conditions
and inputs remain constant through a given model run,  in contrast to                M
time-varying or "real-time" models where such parameters are not held               •
constant.  In estuarine systems, the complexities of the non-steady-state
hydrodynamics greatly complicate nutrient cycles and distributions, oxygen
exchanges, and the growth and distribution of organisms (Harleman 1977,              •
D'Elia et al. 1981).  Mathematical modeling of estuaries is considerably            •
more challenging.  Below, some of the strengths and weaknesses of water
quality models as tools of the scientist and manager are briefly reviewed.          M
    Since estuaries are complex time-varying systems in the hydrodynamic            •
sense, models may be constructed for different pollutants yet contain
similar hydrodynamic representation.  However, factors  not related to               _
hydrodynamics but that affect pollutant chemical specification and                  •
transformation, will probably be pollutant-specific and, thus, require              ™
different modeling formulation.  Virtually any water-quality, numerical
model must be designed with the system and pollutants of interest in mind.          B
    As in the case of water quality indices, data gaps  can be problematical         0
with numerical water quality models.  Standard procedure in developing such
models involves calibration and verification.  Once a numerical model is            •
formulated it is "fine tuned" with a set of environmental data, so that  an          •
appropriate  set of inputs will reproduce a set of data actually collected
in the environment.  At that point, it is calibrated.  The model is next
verified by  seeing if it can reproduce another set of "real" data collected         •
under different conditions.  Data collected must be appropriate to provide          V
for rigorous calibration and verification.  Time and space intervals used
in obtaining data for these processes must reflect the scales that the
model is designed to resolve, and the model,  in turn, should be designed to
                                     63
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                                                                                   I
reflect time and space scales of importance in nature.                              •
    Mathematical models often intimidate non-mathematicians  who,  therefore,
often find it difficult to evaluate the utility of models as management             A
tools*  However, models'  ability to predict or project  water quality               m
conditions is not their only role in aiding managers.   Clearly,
mathematical models are of special benefit in developing conceptual                 _
formulations of nutrient enrichment responses and in identifying  where              •
additional research and data collection are needed (cf. O'Connor  et  al.             ™
1981).

Other Techniques                                                                   0

    Other methods for evaluating the current state of nutrient enrichment          •
that have been less intensively utilized in the CBP.  Two are presently             •
being incorporated in ongoing and incomplete studies of the  Bay.
    Considerable effort has been paid, in particular,  to developing  an
assessment methodology for determining available forms of phosphorus in             •
fresh waters.  Relatively simple, statistical models have been developed to         B
relate phosphorus loading, hydraulic residence times,  and algal biomass  in
a number of lakes.  Leaders in this area of endeavor have included                 M
Vollenweider (1976), Schindler (1977), and Lee et al.  (1978).  Such  an              |
approach would be difficult to accomplish for Chesapeake Bay, because both
phosphorus and nitrogen seem to play roles as limiting nutrients  at
different seasons and in different places, and because loading levels are          •
not adequately quantified.  However, Lee and Jones (1981) have developed a         ™
preliminary statistical model applicable to Chesapeake Bay.
    Bay area scientists have also devoted some attention to  the use  of              •
salinity-dilution diagrams for nutrients.  This method may help identify           ฃ
localities of abundance and depletion of nutrients (Boynton  and Kemp,
unpublished; Taft, unpublished; D'Elia, unpublished; Webb, unpublished).           _
The idea behind this approach is simple:  when nutrients are supplied              •
primarily in freshwater inputs and diluted down-estuary by saline waters           ™
low in nutrients, the concentration of a given nutrient in the water column
will be in proportion to the salinity, unless there are sinks or sources of         B
nutrients along the way.  The statistical modeling of nutrient-loading              9
responses, and the diagraming of salinity-dilution relationships will
probably receive much greater attention in future evaluation of nutrient
enrichment of Chesapeake and its tributaries.
                                  65
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                                  SECTION 4

                  HISTORICAL TRENDS IN NUTRIENT ENRICHMENT
    The review of historical trends in nutrient enrichment of Chesapeake
Bay (Heinle et al. 1980) concluded that nutrient enrichment problems were
greatest in the low salinity areas (less than 8 to 12 ppt), where summer
chlorophyll ฃ concentrations often reach or exceed 60 ug L~^.  Such areas
are those where the tributaries pass through the more populous areas; prior
to population growth, chlorophyll levels in those areas may have rarely
exceeded 20 ug chlorophyll ฃ L"1.  Climatic and other natural factors
strongly affect ecological expression of nutrient enrichment.  This is now
of concern, particularly in the main stem of the Bay where relatively
unenriched seawater dilutes the nutrient content of the enriched river
water.

TREND EVALUATION

    Separating human-induced changes from natural cycles is often the crux
in both scientific assessment of the state of the Bay and management
decisions in preserving (or improving) Bay environmental quality.  The
obvious importance and weight of these determinations lead scientists and
managers to examine the ability to determine accurately a trend or change
in the presence of noise or large variation.  Without resorting to the
formation of signal theory the problem is:  can we be assured that a trend
or change we observe over time is not simply part of a natural cycle of
change, whose period is considerably longer than our viewing time?  One
solution to this uncertainty is to observe the Bay over a time much longer
than the longest period of expected variablility.  The difficulty here,
however, is that natural cycles of climate and runoff can vary over periods
greater than 10 years (Table 3).  If time-series analysts were strict and
required many cycles for accurate determination, then they would demand
records of observations that were longer than all but a few available from
the Chesapeake Bay system.  Table 3 lists some of the cycles that are
expected to affect the Bay's ecosystem.  The shorter-period cycles (with
variation on the order of one year or less) can serve as guides for the
design of observational programs that ensure that the record length will
encompass the variability.  The longer-period cycles offer a test of a
record's ability to separate trend from cycle.
    One rule of thumb for time-series analysis is that a record should
comprise on the order of 10 cycles for proper resolution.  If, for
instance, the Bay ecosystem responded to the six-year cycle in rainfall,
then a 60-year time series would be desirable.  Few natural systems have
been observed with even simple measures for such a long time.
    The situation is not hopeless, however, for scientists and managers who
are forced to assess trends or changes on the basis of time-series with
much shorter lengths.  This assessment can often be made with acceptable
certainty if additional information, such as cause and effect, is
considered.  For comparatively simple relationships, such as the effect of
runoff on estuarine salinity, the separation between trend and cycle can be
achieved despite shorter record length.  A numerical model predicting
                                     66

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                                               •
TABLE 3.  EXAMPLES OF NATURAL CYCLES AFFECTING CHESAPEAKE
          BAY'S ECOSYSTEM


Cycle Period                Type of Cycle


12 to 42 hours        Semidiurnal tide                                              f
24 hours              Diurnal light cycle,  sea breeze,  etc.
4 to 8 days           Passage of low-pressure systems                               _
14 days               Spring-neap tidal range progression                           •
1 month               Monthly tidal variation                                       *
1 year                Seasonal climatic cycle
6 years               Climatic (rainfall, runoff)                                   •
11 to 12 years        Climatic (rainfall, runoff)                                   •,
20 years              Climatic (sunspot activity cycle,
                        rainfall, runoff)                                           _


salinities from runoff data would provide the necessary additional
information here.  For relationships that are derivative and not direct,  or         B
that depend on multiple causes having cycles of differing periods,                  9
separations between trends and cycles are difficult,  even if long records
are available.  Time-series analysis techniques can help refine the                 M
statements on variability, but they cannot provide information that is not          •
on the record itself.  In spite of these warnings and difficulties, the
history of an indicator of Bay environmetal quality is the necessary
starting place for an assessment of change.                                         •

TRENDS BY REGION

    For purposes of contrast and comparison in the ensuing discussion, the          •
Bay is divided into four geographical regions (Figure 4).  These regions
are:  (1) the upper Bay and western shore tributaries,  characterized by the
highest fluvial inputs; (2) the middle Chesapeake Bay;  (3) the eastern              •
shore tributaries, characterized by low fluvial and sewage but high                 W
agricultural nonpoint source inputs; and (4) the southern Chesapeake Bay.
The geographical regions reflect, in a general sense, the segmentation              •
approach to the Bay adopted by the EPA/CBP.  For example, the main Bay and          B,
western shore tributaries can be considered to be analagous (Klein,
unpublished).  However, the EPA/CBP segmentation scheme is more detailed,           _
allowing for close examination of individual portions of the Bay and for             •
modeling purposes.  The EPA/CBP segmentation approach, therefore, provides          ™
for more resolution than is necessary for purposes of this paper.  Readers
who wish to learn in greater detail about historical changes in specific             •
localities should consult Heinle et al. (1980).                                     B

Upper Bay and Western Shore Tributaries                                             .

    This region has been most severely affected by anthropogenic, nutrient
enrichment.  The enrichment problem is greatest in the summer when
water-residence times, light availability, and temperatures are also                •
o/
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Chesapeake Bay
    Region
    Figure 4.  Regions of Chesapeake Bay.
                 68

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                                                                                   I
greatest.  Historical evidence for enrichment-related effects  is  most                ™
substantial in this region,  with long-term trends clearly distinguishable
from short-term variations.   The seasonality of the nutrient cycle is  very          A
evident and quite complex.   Nutrient inputs through the  tributaries are              B
greatest during the high-flow period of the year, typically in March
through May.  These inputs  are characterized by high N:P ratios;  that  is, N         ฃ
is in excess of P relative  to the ratio normally required by phytoplankton          •
(about 16 atoms of N per atom of P).  The amount of N from fluvial sources,
during this period, is high relative to the amount of N  coming into the
system from point sources—sewage treatment plants.  High flow, nonpoint            •
source fluvial inputs are also highly oxidized.  In other words,  nitrate is         m
the primary form in which the N is found.  There is some evidence,
especially for the nitrate  input at high flow from the Susquehanna, the              •
largest volume tributary to the Bay, that much of this nitrate passes                •
through the Bay unassimilated, because of short residence times of this
nitrate relative to the seasonally slow uptake rates of  the plankton for
nitrate (Taft 1982).  A similar condition may exist in other tributaries,           •
and it is important to scale the importance of this N in annual input                H
budgets that have, as their goal, the development of input ratios for
steady-state mathematical models.                                                   •
    In the summer, when river flows decrease, point-source inputs to the            •
tributaries become the predominant input-source of new N and P to the
system.  The N:P ratio of point-source inputs is much lower; however,
regeneration of N and P under oxic conditions from the stored  reserves in           •
the sediments (in effect, a nonpoint source to the water column)  may                •
counterbalance this to some extent.  Chlorophyll levels  in the water column
increase in response to greater hydraulic detention times and  higher algal          •
growth rates.  Oxygen concentrations in the water column are high in the            •
daytime when algal photosynthesis is high and are low at night when
planktonic respiration is not counterbalanced by photosynthetic oxygen              —
production that cannot occur without light.  Fortunately, dissolved oxygen          I
levels in upstream waters rarely get critically low, because the  water              "
column is typically shallow and unstratified and can easily mix and
reaerate.                                                                           •

Upper Bay—
    Early data from the upper Bay exhibited a pattern of maximum  dissolved          •
inorganic phosphate (DIP) concentrations in the spring and fall with                •
minimal concentrations in the winter, and especially in  the summer; more
recent data suggest that relatively uniform concentrations exist  all year
(Figure 5).  For example, in 1949-1951 and 1964-1966, values in June,  July,         I
and August did not exceed 0.645 ug atoms L~l.  In contrast, values in                V
1969-1971 for those months exceeded 1 ug atom L~l.  The  upper  Bay differs
from the western shore tributaries that apparently can reach much higher            •
levels of DIP.  Nonetheless, the upper Bay appears to show some increase in         I
annual DIP abundance.
    The concentration of nitrate plus nitrite-N, the only parameter for             _
which we have reliable data back to the early 1950's, does not appear  to            •
have changed in the upper Bay (Figure 6).  For example,  in March, the                9
period of greatest influx, values in 1964 to 1966 ranged from 20  to over
100 ug atoms L"1.  From 1969 to 1971, March values ranged from 28 to 83
ug atoms L~l.  The seasonal pattern is typical for most  of the Bay, with
                                     69
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the nitrate maximum occurring during the high-flow period,  and the nitrate
minimum during the low-flow period.  The upper Bay is so dominated by the          M
flow of the Chesapeake1s most important tributary, the Susquehanna River,          •
that it is not surprising that nitrate availability in the  water column
strongly reflects nitrate input to the upper Bay by that river.   Additional
information about the dominance of the Susquehanna is presented  by Smullen        B
et al. (1982).                                                                    •
    The effect of enrichment on chlorophyll levels in the upper  Bay is
unclear.  Evidence for increased concentrations of chlorophyll in the upper        m
Bay is inconclusive based on the Heinle et al. (1980) historical data base,        I
whereas the data presented by Salas and Thomann (1978) appear to indicate
conclusively that an increase in chlorophyll occurred.  Although
concentrations of chlorophyll in the early CBI data never exceeded 10 ug          •
L~l, no measurements of chlorophyll ฃ were made during August and                 •
September, the months in which annual chlorophyll maxima are often
achieved.  Productivity may have increased in response to nutrient                •
enrichment without an accompanying increase in plant biomass, providing           I
that the turnover of plant material increased accordingly.
    As in the Patuxent River where the issue of what nutrient, if any,
limits productivity is complex, the issue of what limits phytoplankton            •
production in the upper Bay is also complex.  Salas and Thomann (1978) and        V
Jaworski (1981) concluded that P limitation predominates, but Clark et al.
1973 concluded that N limits phytoplankton growth.  Without a complete            •
understanding of dissolved inorganic nitrogen inputs (other N forms such as        •
ammonium must be taken into account also) and without knowing the seasonal
breakdown on N:P input ratios, the question of whether N or P limits              —
productivity is very difficult to assess (Taft 1982).                             •

Patuxent River—
    The Patuxent River has an excellent historical record,  and it appears
that it provides an analog of the main Bay and western shore tributaries.
(However, correlations evaluating the relationship are being made in the
CBP's characterization analysis).  The Patuxent has been increasingly             _
enriched in recent years; detrimental effects of this enrichment could be         •
expected to occur in analogous segments of the Bay system if they were            *
equally enriched.
The Patuxent River shows a somewhat different pattern in DIP abundance than       I
does the upper Bay.  Figure 7 shows the rather striking historical changes        |
that have occurred in DIP concentrations in surface waters  there, probably
in response to increased point source loadings.  Maximum concentrations of        •
DIP have clearly increased upstream of the Benedict Bridge, where                 •
salinities are typically less than nine ppt.  Downstream of the bridge,
where salinities range from about eight to 18 ppt, surface  DIP
concentrations are significantly lower than those observed  upstream (note         •
scale change between panels in Figure 7), presumably as a result of the           m
dilution of phosphate-rich fresh water by less enriched saline water.
There appears  to have been an increase in DIP levels since  the 1930"s in          •
this region of the river also.  This increase is most pronounced in the           •
summer.  Such  a summer phosphate maximum is characteristic  of Chesapeake
Bay and other  estuaries (Taft and Taylor 1967a,  1967b); it  may result from
surfacing of water rich in phosphate, produced by enhanced rates of benthic       •
regeneration at higher summer temperatures, and  by increased phosphate            •
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solubility at lower oxygen concentrations below the halocline.  Because we
do not know the effect of enrichment on total phosphorus levels,  we cannot
rule out a change in partitioning of water-column-total P resulting in
higher DIP levels.
    On the basis of the 1968-to-present data set, phosphorus limitation
seems unlikely anywhere on the Patuxent River throughout most of the season
when severe oxygen deficits occur (late spring through fall).  Light
limitation seems more probable (O'Connor et al. 1981).  Phosphorus
limitation may have been present prior to the late 1960's, when P loadings
from sewage treatment plants were considerably lower, but this is not
unquestionable.
    The concentrations of nitrate plus nitrite-N in the Patuxent exhibit
the same seasonal cycle of abundance that has been reported for the upper
Bay; moreover, there appears to have been an increase in nitrate content of
the water since the late 1930's (Figure 8).  Most of the increase appears
to have occurred later than 1965, coinciding with the beginning of
extensive development of the Patuxent River basin.  The source of this
nitrate is probably nonpoint; most sewage treatment plants are not
discharging fully oxidized effluents—most inorganic N is usually in the
ammonium, not nitrate form.  As for DIP, less nitrate is found in the water
south of Benedict Bridge, reflecting the dilution of nutrient-rich fresh
water by less enriched saline water.
    The historical record does not include adequate data on ammonium.  This
is unfortunate, because ammonium is taken up preferentially by
phytoplankton relative to most other N forms.  We know from previous work
(Boynton et al. 1980) and work in progress at CBL, that the regeneration of
ammonium by the Patuxent riverbed occurs at some of the highest rates ever
recorded anywhere.  This regenerated ammonium can drive internal recycling
processes in the absence of added nutrients (Nixon 1981).  We know also
that this ammonium accumulates below the halocline and diffuses across that
boundary often at rates lower than those at which it is removed from the
water column above.  Boynton (personal communication) does not consider the
sediment nitrogen reserves to be adequate for more than a few weeks' supply
of regenerated ammonium, and there appears to be rapid settlement and
mineralization of nitrogen on the benthos.  Rapid recycling of nitrogen
occurs between the water column and the riverbed.  A productive system
could be maintained for some time in the absence of added nutrients; the
effects of nutrient controls might not be immediately apparent.
    Although the analytical procedure for determination of nitrite has
remained essentially the same over the last 50 years, relatively little
attention has been paid to its measurement.  This is because it rarely
achieves significant concentrations in the water column.  A number of
investigators have observed periodic accumulations of nitrite in Chesapeake
Bay waters (McCarthy et al. 1977; Webb and D'Elia 1980; Academy of Natural
Sciences of Philadelphia, unpublished).  This nitrite accumulation occurs
in the late summer and early fall and is probably a consequence of ammonium
oxidation (nitrification, step one).  In a synoptic sampling program
conducted in the fall of 1981, Taft et al. (unpublished) observed elevated
nitrite concentrations throughout the Bay.  In the Patuxent River, levels
exceeded 15 uM nitrite-N.  It is unknown whether this phenomenon occurred
historically, but Webb (1981) suggests that the magnitude of the nitrite
accumulation is a function of the degree of nutrient enrichment of the Bay
                                  74

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during the summer, and he recommends continued monitoring of the nitrite
maximum.
    There is strong evidence that nutrient enrichment stimulated increased
phytoplankton production and an accumulation of plant biomass in the lower
Patuxent River.  This conclusion is based mainly on Secchi-depth data
rather than chlorophyll-concentration data, because the historical data
base for chlorophyll on the Patuxent is less complete (but suggests the
same trends).  Figure 9 shows Secchi data from July, 1937 to July, 1978,
normalized against surface salinity (to account for variations in river
flow).  The inability of the Secchi disk to resolve differences in
transparency when transparency is low, means that little can be said about
historical changes at surface salinities below about eight ppt.  Such low
salinity regimes are also subject to high levels of because of turbidity
because of inorganic sediment.  However, at the greater transparencies
found at higher salinities, the resolving power of the Secchi disk is good,
and inorganic sediment loads, particularly at lower flow times of the year
such as July, are less appreciable.
    Transparencies of the water in the lower estuary during 1963 were
similar to those observed during 1936 to 1940 (Figure 9).  Heinle et al.
(1980) felt that the decreased Secchi depths in the lower estuary during
the summer in recent years reflect increased standing stocks of algae and
probably also of organic detritus; an alternate explanation is that small
particle sediment levels have increased.  Increases in algal standing
stocks imply that algal production has increased to a rate greater than
that of its consumption, and that a concomitant increase in BOD has also
occurred.  This is of concern because, in the lower Patuxent estuary, which
is often stratified in the summer, oxygen concentrations are quite low in
the earliest data, and they may be driven lower by the settling of organic
matter with high BOD produced in surface waters.  Still unresolved is how
great a role is played by nutrient rich-oxygen poor deep water advected
into the river from the Bay.  Clearly, inputs from the Bay are important;
likewise, nutrient inputs to the lower river from upstream sources may
stimulate organic production in the lower river and increase BOD.  This
increased BOD may further depress deep-water oxygen concentrations.  Oxygen
concentration and factors that affect it in the lower Patuxent are
discussed in greater detail below.
    One of the more common effects of excessive enrichment is increased
variation in diurnal and nocturnal dissolved oxygen concentration in the
water column, in response to greater levels of community metabolism.  This
represents a particularly serious problem when nighttime consumption of
oxygen by respiration becomes great enough to lower oxygen tension to a
point where it jeopardizes the viability of aerobic organisms in the
community.  Under such conditions, we observe the nuisance conditions most
often associated with excessive nutrient enrichment or as many refer to it
"eutrophication."  There is evidence that day/night deflections in oxygen
concentration in the upper Patuxent are increasing, although the problem,
at least at Benedict where the measurements have been made, has yet to
reach crisis.proportions.  Cory (1974) and Cory and Nauman (1970) noted
evidence for such changes in the Patuxent at Benedict during the period
from 1963 through 1969.  They observed greater extremes in concentration of
dissolved oxygen and a reduced ratio of production in respiration during
that period, suggesting that increased levels of heterotrophy are
                                     76

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occurring.  In a later unpublished study from which Cory made his data
available to Heinle et al. (1980), it appears that continued changes have
occurred between 1969 and 1977.  Figure 10 shows weekly maximum and minimum
concentrations of dissolved oxygen during May through August near the
surface at Benedict Bridge.  Minimum concentrations observed (about 2 mg
02 L~l) are fortunately, transient, but are nonetheless approaching
dangerously low values.  The increased range of values in 1977 over that of
1964 is clearly evident in Figure 10.
    The greatest ecological concern in the Patuxent River does not rest  in
oxygen concentrations nor in aesthetic deterioration by enhanced turbidity
in upstream waters but, instead, in the oxygen concentration in the deep
waters of the lower estuary.  In a stratified body of water such as the
Patuxent estuary, increased productivity in the surface waters can cause
decreased oxygen concentrations in deeper waters as organic matter settles
in the water column and decomposes.  Sustained oxygen depletion (perhaps by
this mechanism) is known to occur naturally in the central part of the Bay
(Newcombe and Home 1938, Taft et al. 1980).  On the basis of present
information, the extent of this low-oxygen water is increasing with time.
    Nash (1947) observed that the differences between surface and bottom
concentrations of dissolved oxygen were greater at times of greater
stratification, and he postulated that the degree of stratification was  an
important determinant of bottom-dissolved-oxygen concentration.  D'Elia  and
Farrell (unpublished manuscript) have plotted bottom-dissolved-oxygen
content of lower Patuxent waters, versus an index of stratification,
surface to bottom salinity difference, over a period of three summers
(Figure 11).  They have verified Nash's observations that stratification
strength is a critical consideration.  Bottom-oxygen levels decrease with
increasing stratification, because mixing with aerated upper waters is
prevented.  Similar results have been observed for the mainstem of
Chesapeake Bay (Taft et al. 1980) and for the lower York River (Webb and
D'Elia 1980).  This greatly complicates the interpretation of nutrient
enrichment effects, and it is not surprising that bottom-dissolved-oxygen
content in the historical data base shows a wide variation within a given
year (Figure 12).
    The long-term decrease in mean oxygen content of deep waters in the
lower Patuxent is one of the more striking examples of an enrichment-
related phenomenon in the mesohaline regions of Chesapeake Bay.  Figure  12
shows that recent, bottom-dissolved-oxygen content in the lower Patuxent is
considerably lower on the average than it was in earlier years.  The
highest concentrations observed in the deep water south of Benedict do not
exceed about six mg L~l in the recent data, whereas in the 1936 to 1940
data, deep water oxygen concentration maxima were twice that, reaching
supersaturation at 12 mg L~l.  Heinle et al. (1980) noted that the
Winkler oxygen method has remained essentially the same for decades and,
after checking and verifying the accuracy of the notes and calculations  of
the original analyst, concluded that the early data were reliable.
    Concentrations of dissolved oxygen in bottom waters between Benedict
and Broomes Island appear to be affected by in situ respiration and
decomposition of organic matter produced within the Patuxent estuary and by
intrusion of Bay waters naturally low in dissolved oxygen.  The relative
roles of these two causes of oxygen depletion are not certain.  Low
concentrations of dissolved oxygen are often observed downstream of Broomes
                                    78

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                                                                                    I
Island.  On occasions when concentrations are low upstream of  Broomes                B
Island, they are not so low downstream near the mouth  of  St. Leonard's
Creek (Figure 12).   This suggests that the Bay is not  the sole source of             •
the very low dissolved oxygen water.                                                 I

Potomac River—                                                                     _
    The Potomac River has been studied with varying  degrees of intensity             B
since 1913, yet the early data set for the Potomac is  not so extensive  as            ™
it is for the Patuxent, where CBL scientists were conducting some  of  the
first intensive basic research on the nutrient distribution and dynamics of          H
an estuary.  Wolman (1971) reviewed the history of the effects of  a growing          |
population on continuing efforts toward improvement  of water quality  in the
Potomac.  Jaworski et al. (1972) also discuss the changes that have                  _
occurred there.  The USGS is presently conducting comprehensive studies on          I
the water column and sediments of the river, expecting to produce  detailed          ™
reports on their studies in the next  year.  There is an excellent
environmental atlas of the Potomac River (Lippson et al.  1979) that should          B
also be consulted for further details.                                              |
    Because the most serious problems in the Potomac occur near the head of
tide near Washington, DC, most scientific and monitoring  efforts have dealt          _
with that region of the river.  Yet even now, with concern growing about             B
the higher salinity regions farther south in the river, most debate and             ™
study of water quality still center on upriver regions.  Gumming et al.
(1916) apparently measured nutrient and dissolved oxygen  concentrations in          B
the lower estuary during 1913, but Heinle et al. (1980) could  not  locate             B
the data.  Although CBI did conduct some sampling in 1949 to  1951  (Hires et
al. 1963, Stroup and Wood 1966), the  first intensive studies of water                M
quality that encompassed the length of the estuary were those  of CBI  during          I
1965 to 1966 (Carpenter et al. 1969).  What data do exist for  the  Potomac
estuary suggest that slightly higher  concentrations of phosphorus  and
considerably higher concentrations of chlorophyll ฃ occur during the  summer          B
in the lower Potomac.  By the time of the CBI studies, quite elevated                B
chlorophyll a_ concentrations of 80 to 100 ug L~l were  common in the
portion of the estuary up to 20 miles or more downstream  from  Washington,            •
DC.  Dissolved oxygen levels frequently reached low concentrations and               ^
there were substantial blooms of blue-green algae (Jaworski et al. I971b,
1972).  Since that time, plans were made to limit both the N and P levels            _
in the effluent from the largest single point source to the Bay, the  Blue            B
Plains Sewage Treatment Plant.  However, N controls were  never instituted.          ™
A battle still rages over the effectiveness of the single nutrient advanced
wastewater treatment strategy in force; there have been hearings held in             •
front of administrative law judges in the past year.                                |
    The floating mats of blue-green algae that were prominent  during  the
1960"s were not observed in the more recent studies, and  this  has  prompted          _
EPA officials to regard the present Blue Plains effluent  limitations  as             B
effective.  Proponents of the opposite point of view argue, instead,  that            •
flow regimes and hydraulic detention times, characteristic during  the
periods of the worst problems with blue-greens, have not  occurred  in  recent          •
years.  Irrespective of the outcome of the controversy, it is  apparent  that          B
some nutrient control strategy will be necessary to prevent future problems.
    An interesting contrast occurs between the Potomac, where  extensive             _
blue-green algal blooms are seen, and other tributaries to the Bay, where            B
                                     81
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they are not.  Blue-greens are rarely dominant in the water columns of
saline environments of any tributary, including the Potomac; in the
freshwater parts of the Potomac, N:P input ratios and characteristic                I
hydraulic features probably account for the blue-green blooms.                       m

James River—                                                                       •
    Heinle et al. (1980) were unable to locate substantial early data for           •
the James River.  The first useful data on the James River were obtained by
CBI in 1950, followed by a more complete study by Brehmer and Haltiwanger           _
(1966), who sampled farther upstream than previous workers.  By the time            •
they began their study, the upper James appeared to have already been               •
affected by enrichment.  Summer chlorophyll concentrations of 50 to 80 ug
L~~l were common at their upriver stations in the tidal-freshwater portion           •
of the estuary, and 20 to 50 ug L~l were observed at their midriver                 •
stations.  Prior to enrichment, annual chlorophyll maxima in the low
salinity regions of all of the western tributaries probably rarely exceeded
30 to 40 ug chlorophyll a IT*-.                                                      I
    DIP concentrations upriver show no seasonal or longitudinal patterns in         ^
the data of Brehmer and Haltiwanger (1966); typical values are  less than
1.0 ug-atom L~l.  Downriver, a slight summer-concentration maximum is               •
apparent as is characteristic for the Chesapeake estuary (Taft  and Taylor           |
1976a, 1976b) (Figure 13).  Data collected in the 1970's (Adams et al.
1975) show markedly higher concentrations of DIP through most of the year           _
than in the earlier data (Figure 13).  There have also been significant             I
increases in nitrate and nitrite in the lower James estuary (Figure 14).            *
Earlier data evidenced the spring seasonal maximum characteristic in Bay
tributaries; in the latter study nitrate levels were high year-round.               •
    In spite of the high ambient levels of both N and P in the  lower James,         |
concentrations of chlorophyll ji have apparently not increased (Figure 15).
The explanation for this apparent lack of response to enrichment is                 _
uncertain, but may simply relate to an increased turnover rate, but not to          I
standing stock of plant material or to inadequate data availability.                —

York and Rappahannock Rivers—                                                      I
    In recent years, the York and Rappahannock have also exhibited                  |
increased levels of chlorophyll and nutrients; changes are comparable to
those observed in other tributaries, so they will not be reviewed in detail         •
here.  There are some interesting hydrographic aspects of the York, James,          •
and Rappahannock Rivers that have bearing on the water quality of those
estuaries.  Haas (1977) noticed that there was a striking correlation on
those rivers between the occurrence of high spring tides and                        •
destratification of the water column.  Since then, in more detailed studies         •
of this predictable occurrence, it has been learned that the water quality
characteristics are affected greatly by this cycle (Webb and D'Elia 1980;           •
D'Elia et al. 1981).  As for the Patuxent River, the bottom-dissolved-              |
oxygen concentration of the York (and presumably the James and
Rappahannock) River is generally highest under conditions of
destratification.  Thus, the water quality of the river, as reflected in            •
oxygen content of the bottom water, can alternate rapidly between                   •
acceptable  and low values.  Nutrients are also affected.  Short-term
phenomena like this greatly complicate the evaluation of enrichment in an           •
estuary and  cause considerable  range in the values of water quality                 |
                                     83
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Concentrations of nitrate-N by month in the lower James River, Virginia.
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parameters measured.  Such phenomena also seem to indicate that the                 I
steady-state assumption often used in water quality models may be a risky,
one, if realistic model results are to be obtained.

Middle Chesapeake Bay                                                               •

    The mid-Bay is showing evidence of nutrient enrichment, but it is not           •
as severely affected as are the western shore tributaries and the upper             |
Bay, probably because of the sheer volume of this region and because of the
ameliorating affects of dilution by low-nutrient sea water.  A fair amount          _
of early work at CBL was conducted in the mid-Bay off the mouth of the              •
Patuxent River (Newcombe 1940, Newcombe and Brust 1940, Newcombe and Lang           •
1939); there is a reasonably extensive set of older data for this area.
    DIP was comparable at all depths from 1936 to 1951, with values ranging         •
from undetectable to 1.3 ug atom L~l (Figure 16).  By 1964 to 1966,                 |
maximum values increased to two ug atom L~l and, by the mid 1970's,
values of 2.5 ug atoms L~l were observed (Figure 16).  Chlorophyll ฃ data           •
show some increases in the mid-Bay between 1951 and 1964 to 1966.  Peak             •
values in the euphotic zone (upper 10 m) are less than 25 ug L~l (Figure
17).  The highest values were observed in the deep water, usually in winter
or spring.                                                                          •
    The data for nitrogen are less complete than for phosphorus.  As in the         |
tributaries, nitrate tends to be the dominant inorganic form in the winter
and spring and is associated with high runoff.  Salinity-dilution diagrams          •
of the main stem of the Bay prepared by Taft (1982) indicate that this              I
nitrate is conservatively diluted by seawater.  This suggests that most of
this nitrogen is passing through the mid-Bay unassimilated.  Ammonium is
more abundant in the summer and fall, but the lack of old historical data           I
for ammonium leaves no basis for comparison.  As in the tributaries, there          •
is a late-summer, early-fall nitrite maximum in the mid-Bay (McCarthy et
al. 1977, Taft et al., unpublished); this nitrite is probably derived from          •
the oxidation of ammonium by nitrifying organisms (McCarthy, unpublished).          •
    Phosphorus probably limits biomass in the spring when inorganic
nitrogen is abundant (Taft et al. 1975; Taft and Taylor 1976a, 1976b).
However, there are too few data to establish clearly a limiting nutrient in         •
other seasons.  Flemer and Biggs (1971) have noted that "the suspended              •
particulate organic material in [that region] is suffering a relative loss
of nitrogen with respect to carbon," and it may be that there is temporal           •
variation in the limiting nutrient.                                                 |
    The range of dissolved oxygen values for surface waters is comparable
in the earliest and latest data sets available (Figure 18).  Oxygen                 _
concentrations in the deep water, however, seem to be depressed for longer          •
periods in the summer and over wider regions of the mid-Bay.  There is some         *
concern that low-oxygen, high-nutrient water masses advected from the deep
mid-Bay into the lower tributaries such as the Patuxent exacerbate present          •
enrichment problems there.                                                          •
                                     87
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Lower Bay

    Data for the lower Bay are available from CBI cruises of 1949 to 1951,
1961, and 1969 to 1971.  Other data Heinle et al. (1980) used in comparison
came from Smith et al. (1977), from Patten et al. (1963), and from
Fleischer et al. (1977).  Sufficient data exist to show that the lower Bay
has remained relatively unaffected by nutrient enrichment upestuary.
Because little change is evident, the data will not be reproduced here but
instead will highlight the major features characteristic of the nutrient
regime in the lower Bay.
    DIP concentrations, throughout the lower Bay, were low historically and
continue to be so.  The summer maximum of phosphate reaches or exceeds
slightly 1.0 ug atom L~l, but is generally half that or less in other
seasons.  Nitrogen is not well represented in the historical data base so
historical changes cannot be assessed.  Recent data showed that nitrate
availability in the lower Bay is similar to its availability in the central
Bay—high-flow nitrate maxima are observed, and most of this nitrate
probably passes out the Bay mouth unassimilated.  Maxima in the spring may
approach, or even rarely exceed, 25 ug atom L~l.  McCarthy et al. (1977)
provide a detailed summary, by season, of nitrogen dynamics and the
plankton of the lower Bay.  Spring maxima in chlorophyll levels occur that
exceed 20 ug L~l; however, for the rest of the year, concentrations are
generally below 13 ug L~l, and are characteristic of a relatively
unenriched system.

Eastern Shore Tributaries

    The flows associated with eastern shore tributaries are trivial with
respect to those of the western shore.  Historical data suggest that
moderate effects of enrichment can be observed in eastern shore
tributaries.  The earliest data were again obtained by CBI in the late
1940"s.  Early data show chlorophyll levels of less than six ug L~l in
the Chester, Choptank, and Miles Rivers, and low DIP levels as well (<0.6
ug atom L~l).  More recent observations show chlorophyll levels exceeding
25 ug atom L~l.
    Recent studies on SAV conducted for the EPA show that nitrogen is
likely to be severely limiting on the Choptank River during the summer.
Figure 19 presents results reported by Twilley et al. (1981) on dissolved
inorganic nitrogen:dissolved inorganic phosphorus (DIN:DIP) ratios in the
water column from April through September of 1980.  There is a progression,
from a condition in which DIN is far more abundant than DIP in April, to a
condition in which the opposite is true in September.  When N:P is less
than 15, nitrogen limitation may occur; Figure 19 shows nitrogen becoming
potentially limiting in July.  DIN:DIP ratios shown for September are below
2.0 and are among the lowest values reported for the Chesapeake.
    Most of the nutrients responsible for the observed enrichment of
eastern shore tributaries undoubtedly derive from nonpoint source inputs
associated with agricultural runoff.  With the cost of fertilizers going
up, more judicious and parsimonious application may occur, reducing
loadings.  Increased awareness of minimum tillage practices and wiser land
use may also reduce nonpoint source inputs somewhat.  Future nutrient
enrichment problems will result more from population increases and
associated point source loadings than from increases in diffuse sources.
                                     90

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                     8       12

                   SALINITY,  %0
                                                             16
Figure  19.   Nitrogen:Phosphorus ratios  (dissolved inorganic nutrients  only)
             in surface and  bottom waters  of the Choptank  River, 1980.
                                           92

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                                                                                   I
    The hypothesis has been advanced that the disappearance of  submerged           •
aquatic vegetation (SAV), once abundant in the shallow waters of the
Eastern Shore and its tributaries,  is because of turbidity related reduced         _
light levels to a point below which SAV can survive.   The historical data          •
base on chlorophyll levels for eastern shore tributaries is consistent with        ™
this hypothesis.  Since nutrient loadings to this area of the Bay are
primarily from nonpoint sources, the prospect of controlling enrichment and        •
associated plant biomass induced turbidities seems poor.                           |
                                     93
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                                  SECTION 5

                           SUMMARY AND CONCLUSIONS
    Chesapeake Bay and its tributaries have undergone increased nutrient
input over the last several decades.  The most severe effects of this input
that can be discerned with reasonable assurance have occurred in the
tributaries.  Particularly affected are the low-salinity regions near large
urban centers and sewage treatment facility effluents.  Figure 20, taken
from the Heinle et al. (1980) report, gives approximate locations of the
moderately and heavily enriched areas in the Bay and its tributaries.  The
criteria used in developing this figure are as follows:  In the low
salinity areas (less than 8 to 12 ppt), pre-enrichment concentrations of
chlorophyll ฃ were believed, by those authors, to be less than 30 ug L~l;
hence values between 30 and 60 ug L~l during the summer months were taken
to indicate moderate enrichment.  Concentrations over 60 ug L~l were
taken to indicate high enrichment.  In the high salinity areas (greater
than 8 to 12 ppt), where historical data suggest that concentrations of
chlorophyll rarely exceeded 20 ug L~l during the summer, concentrations
of 20 to 40 ug L~l were considered to represent moderate enrichment;
values exceeding that, great enrichment.  Although Heinle et al. (1980)
recognized that chlorophyll levels per se were not necessarily bad, the
relatively great change in chlorophyll concentrations, over apparent
pristine levels, was considered a harbinger of enrichment problems.  This
is especially true when the chlorophyll levels, now encountered, represent
the presence of an amount of organic material that when oxidized could
account for depletion of oxygen from the water column in summer months.
Heinle et al. (1980) emphasize that it is excessive oxygen depletion that
most laymen and professionals regard to be the most severe result of
over-enrichment of natural waters.  Oxygen depletion problems in the Bay
are discussed further below, but first some of the important regional
concerns represented in Figure 20 will be summarized.
    A good and well-known example of a severely affected location is the
Potomac River near Washington, DC.  Although other localities on the Bay
and its tributaries are not yet considered to exhibit such serious symptoms
of over-enrichment, effects of increased nutrient loadings have been
noticed.  For example, the upper Patuxent River in Maryland, for which an
excellent historical data record exists, has shown signs of decreased
transparency and increased nutrient concentrations and standing stocks of
algae.  The upper James River in Virginia can be considered similarly
enriched.
    There is concern in the lower Patuxent River that increased production
of organic matter, as a result of increased nutrient loadings, may
ultimately lead to lower dissolved oxygen concentrations, particularly in
deep water, through the decay of organic matter.  But because the nutrient
dynamics and trophic structure of this estuary are not adequately
understood it is difficult to predict or project through modeling exactly
how the estuary will respond to increased loadings.  The CBP's
characterization analysis will discuss these responses further.
    The other lightly shaded areas shown in Figure 20, like the lower
Patuxent, are the middle salinity zones that are considered areas of prime
concern.  Figure 21 shows portions of Chesapeake Bay where Heinle et al.
                                     94

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       .Chesapeake   Bay
               Region
          0  5 "i^?
           STATUTE MILES
Figure 20. Map showing portions of Chesapeake Bay that are moderately
          or heavily enriched according to the criteria of Heinle et al. (1980),
                                  95
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    Chesapeake - Bay
                                         Changes in Dissolved
                                         Oxygen
Figure 21.  Map  showing portions of Chesapeake Bay where natural regimes
           of dissolved oxygen appear to have changed.
                           96

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                                                                                    I
felt that worrisome alterations in oxygen regime of the deep water in               •
particular have apparently occurred in response to enrichment.   Yet to be           *
learned is whether the most important causes of oxygen depletion in these
areas are enhanced productivities in local surface waters,  periods of high          B
freshwater flow and resultant poor vertical mixing and reaeration, or               |
import and decay of organic material produced upstream.   The interaction of
these factors is not completely understood, and the historical  data base is         M
not comprehensive enough to allow us to analyze it adequately.   However,             •
apparent changes in oxygen regime in the mid-Bay must  be viewed as
tentative, but probable.
    Because too little is presently known to manage the trophic structure           I
of the Bay to result in increased fisheries yields from additional nutrient         •
input, sensible efforts to control inputs should continue.   The indication
that nitrogen is often limiting in the lower and middle reaches of the Bay          tm
suggests that affordable advanced technologies for N enrichment control             •
should be sought and given due consideration for implementation.  However,
other considerations are important; for instance, it will make  little sense
to implement nutrient-removal processes that will ultimately prove too              •
costly to operate or too complex to manage properly.  Workable  management           •
programs for the future will certainly involve better land use  practices
and control of nonpoint-source N inputs, particularly in the summer months          •
when hydraulic residence times are longest.  Unconventional or  unpopular            •
sewage treatment processes such as land application may prove important in
controlling enrichment.                                                             _
    Continued scientific evaluation of the trophic structure and of the             •
nutrient dynamics of the Bay will prove important if we are to  assess               •
adequately future changes and the efficiency of control strategies.
Routine monitoring programs should be adopted and supplemented  by more              •
basic research into effects of enrichment on algal productivity, species            |
composition, and the natural assimilative capacity of the environment for
nutrients.  An inventory of point source inputs should be established and           •
kept up-to-date.  These and other data are useful to environmental                  •
scientists.  The partitioning of the carbon, fixed by algal photosynthesis
among species at higher trophic levels, remains a poorly understood but
critical area for research.  Dose-response studies, such as those sponsored         I
by the EPA in Narragansett Bay, Rhode Island, may prove extremely helpful           R
in this regard.  Scientists, modelers, and managers should work closely to
develop models of hydrodynamics and of dose responses to nutrient                   •
addition.  This information will help identify gaps in understanding the            I
Bay's ecology and in locating problem areas.
                                  97
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                              LITERATURE CITED
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Boynton, W. R.,  and W. M.  Kemp.  1982.  Ecological  Role  and Value  of
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Boynton, W. R.,  W. M. Kemp, and C.  G.  Osborne.  1980. Nutrient Fluxes
    Across the Sediment-Water Interface in the Turbid Zone of a Coastal
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Brehmer, M. L.,  and S. 0.  Haltiwanger.  1966.  A Biological and Chemical
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Brown, R. M.,  N.  I.  McClelland, R.  A.  Deininger, and R.  G. Tozer.   1970. A
    Water Quality Index—Do We Dare?  Water and  Sewage Works,   pp.  339-343.


Brush, L. M.,  Jr.  1974.  Inventory of Sewage Treatment  Plants  for
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Carpenter, J.  H., D. W. Pritchard,  and R.  C. Whaley.  1969.  Observations of
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Clark, L. J.,  D. K.  Donnelley, and  0.  Villa.  1973.  Summary and
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Cory, R. L.  1974.  Changes in Oxygen and Primary Production of the
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Cory, R. L., and J.  W. Nauman.  1970.   Temperature  and Water Quality
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    through December 1977.  Ches. Sci.  11:199-209.


Gumming, H. S.  1916.  Investigation of the Pollution of Tidal  Waters  of
    Maryland and Virginia.  U.S.  Treasury Dept., Public  Health  Service,
    Bull. No.  75.  199 pp.
                                 98

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    W. G. White.  1976.  Correlation of Chlorophyll,  Suspended Matter, and
    Related Parameters of Waters in the Lower Chesapeake Bay Area to
    LANDSAT-1 Imagery.  Inst. of Oceanography, Old Dominion University
    Tech. Rep. 28, Norfolk, VA.  125 pp.
                                  99
                                                                                  I
Gumming, H. S., W. C. Purdy, and H. P.  Ritter.   1916.   Investigation of           •
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D'Elia, C. F.,  K. L. Webb, and R. L. Wetzel.  1981.   Time-Varying
    Hydrodynamics and Water Quality in  an Estuary.   In:   Estuaries and            a
    Nutrients.   B.J. Neilson and L.E. Cronin, eds.   Human Press.   Clifton,         •
    NJ.  pp. 597-606.                                                             •

Flemer, D. A.,  and R. B. Biggs.  1971.   Particulate  Carbon:  Nitrogen             •
    Relations in Northern Chesapeake Bay.  J. Fish.  Res. Bd.  Canada.              p
    28:911-918.

Fleischer, P.,  T. A. Gosink, W. S. Hanna, J. C. Ludwick, D. E.  Bowker, and         •
I
Haas, L. W.  1977.  The Effect of the Spring-Neap Tidal Cycle on the               _
    Vertical Salinity Structure of the James, York and Rappahannock Rivers,         •
    Virginia, U.S.A.  Estuarine Coastal Mar. Sci.  5:485-496.                      ™

Harleman, D. R. F.  1977.  Real-Time Models for Salinity and Water Quality         •
    Analysis in Estuaries.  In:  Estuaries, Geophysics, and the                    |
    Environment, National Academy of Science, Washington, DC.  pp. 84-93.

Heinle, D. R., C. F. D'Elia, J. L. Taft, J. S. Wilson, M. Cole-Jones, A. B.         I
    Caplins, and L. E. Cronin.  1980.  Historical Review of Water Quality
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    #R806189010.  Chesapeake Research Consortium, Inc.  Publication No.             •
    84.  Annapolis, MD.

Hires, R. I., E. D. Stroup, and R. C. Seitz.  1963.   Atlas of the                  I
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    Summary Rep. No. 3.  411 pp.                                                   I

Jaworski, N. A.  1981.  Sources of Nutrients and the Scale of Eutrophication
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 I
Jaworski, N. A., L. J. Clark, and K. P. Feigner.  1971a.  A Water Resource-         •
    Water Supply Study of the Potomac Estuary.  U.S. Environmental                  *
    Protection Agency, Annapolis Field Office, Region III, Tech. Rep. 35.

Jaworski, N. A., D. W. Lear, Jr., and 0. Villa, Jr.  1971b.  Nutrient               Jj
    Management in the Potomac Estuary.  U.S. Environmental Protection
    Agency, Middle Atlantic Region, Annapolis Field Office, Tech. Rep. 45.          M
    64 pp.
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Jaworski, N. A., D. W. Lear,  Jr., and 0.  Villa,  Jr.   1972.   Nutrient
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Lee, G.F., W. Rast, and R. A. Jones.   1978.   Euthrophication of Water
    Bodies:  Insights For an Age-Old  Problem.  Env.  Sci.  Technol.
    12:900-908.


Lippson, A. J., M. S. Haire,  A. F. Holland,  F.  Jacobs, J. Jensen,  R. L.
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McCarthy, J. J., W. R. Taylor, and M. E. Loftus.  1974.  Significance of
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McCarthy, J. J., W. R. Taylor, and J. L. Taft.   1977.  Nitrogenous
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McErlean, A. J., and G. J. Reed.  1981.   Indicators and Indices of
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                                  100

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                                                                                   I
Newcombe, C.  L.,  and A.  G.  Lang.   1939.   The Distribution  of  Phosphates  in
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Newcombe, C. L. ,  and W. A. Home.  1938.   Oxygen Poor Waters  of  the                 •
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                                                                                   I

Nixon, S. W.  1981.  Remineralization and Nutrient Cycling in Coastal               •
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    Environmental Indices:  Outdoor Recreational Resources and Land  Use
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Salas, H. J., and R. V. Thomann.  1978.  A Steady-State Phytoplankton Model
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    Lower Chesapeake Bay.  In:  The Effects of Tropical Storm Agnes  on the          •
    Chesapeake Bay Estuarine System.  The Chesapeake Research Consortium,          |
    Inc.  Pub. No. 54, The Johns Hopkins Univ. Press, Baltimore, MD.   pp.
    299-310.                                                                       •

Smullen, J., J.  L. Taft, and J. Macknis.   1982.   Nutrient and Sediment
    Loads to the Tidal Chesapeake Bay System.  This Volume.

Stroup, E. D., and J. H. Wood.  1966.  Atlas of  the Distribution of                 B
    Turbidity Phosphate, and Chlorophyll in Chesapeake Bay,  1949-1951.
    Chesapeake Bay Inst., The Johns Hopkins Univ.,  Graphical Summary Report
    No. 4.  193 pp.
                                  101
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Taft, J. L.  1982.   Nutrient Processes.   This Volume.


Taft, J. L., and W. R. Taylor.  1976.  Phosphorus Dynamics in Some Coastal
    Plain Estuaries.  In:  Estuarine Processes.   M.  Wiley, ed.   Academic
    Press, NY.  pp. 79-89.


Taft, J. L., W. R.  Taylor, and J. J. McCarthy.  1975.   Uptake and Release
    of Phosphorus by Phytoplankton in the Chesapeake Bay Estuary.  Mar.
    Biol. 33:21-32.


Taft, J. L. W. R. Taylor, E. D. Hartwig, and R.  Loftus.  1980.   Seasonal
     Oxygen Depletion in Chesapeake Bay  Estuaries.  3:242-247.


Thomas, W. A.  1972.  Indicators of Environmental Quality:  An  Overview,
    In:  Indicators of Environmental Quality. W. A. Thomas, ed.  Plenum,
    NY.  pp. 1-5.


Twilley, R., M. Meteyer, N. Kaumeyer, J. Means,  W. Boynton,  W.  Kemp,  K.
    Kaumeyer, K. Staver, and A. Hermann.  1981.   Nutrients,  Sediments and
    Herbicides in Agricultural Runoff and the Distribution of These Water
    Quality Variables in Middle and Upper Regions of Chesapeake Bay.   In:
    University of Maryland Center for Environmental and Estuarine Sciences,
    Final Submerged Aquatic Vegetation Report to EPA Chesapeake Bay Program.


Vollenweider, R. A.  1976.  Advances in Defining Critical Loading Levels
    for Phosphorus  in Eutrophication.  Mem.  1st. Ital.   Idrobiol.  33:53-83.


Webb, K. L.  1981.   Conceptual Models and Processes of  Nutrient Cycling  in
    Estuaries.  In:  Estuaries and Nutrients. B.J.  Neilson  and L.E.
    Cronin, eds.  Humana Press.  Clifton, NJ. pp. 25-46.


Webb, K. L., and C. F. D'Elia.  1980.  Nutrient  and Oxygen Redistribution
    During a Spring-Neap Tidal Cycle in a Temperate Estuary.  Science.
    207:983-985.


Wetzel, R., and R.  Van Tine.  Light and  Submerged Macrophyte Communities in
    Chesapeake Bay.  This volume.


Wolman, M. G.  1971.  The Nation's Rivers.  Science.  174:905-918.
                                  102

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      Chesapeake Bay Institute
          4800 Atwell Road
     Shady Side,  Maryland  20867
                                                                  I
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             CHAPTER 2
Nutrient Processes in Chesapeake Bay                              I

                                                                  I
              Jay Taft
    The Johns Hopkins University                                  I
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                                  CONTENTS
Figures ...............................   105
Tables ...............................   106
Sections


    1.   Introduction ........................
    2.   Nutrient Availability and Phytoplankton Physiology .....
             Patterns of Availability ................

                 Bay ........................   112
                 Tributaries ....................   ••,,-
             Factors Affecting Phytoplankton Growth and Productivity
                 Background:  The Requirements of Phytoplankton.  .  .   -,24
                 Response of Phytoplankton to Nutrients .......   ,2_
                 Response of Phytoplankton to Physical Processes  .  .   .j^a
                 Kinetic Measurements of Nutrient Uptake ......   ,_g
                 Summary of These Factors ..............   ,~-
    3.   Nutrient Cycling ......................   ,.,,
             Introduction ......................   -104
             Water Column Processes ...........     ....
                 Respiration ....................   TOE
                 Grazing ......................
                 Bacterial Activity .................
             Sediment Processes ...................
                 Nutrient Flux ...................
                 Sorption-Desorption ................
                 Geochemical Reactions ...............   -,,-,
                 Marshes and Bay Grasses ..............   -, /ซ
    3.   Dissolved Oxygen in the Estuary ..............   -.,.,
             Oxygen Sources .....................   . ,~
             Oxygen Utilization ...................   , , ,
    4.   Summary and Conclusions .............  .....   -.,,-


Literature Cited ..........................   2.47
                                    104

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                                   FIGURES

Number
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  1  Map of Chesapeake Bay showing sampled stations  	   108           •
  2  Binary dendogram showing possible response of the water column                 ™
     to increased nutrient loadings  	   109
  3  (a) Schematic diagram of the basic nutrient cycle in aquatic                   •
     systems, (b) inorganic nitrogen cycle transformations mediated                 f
     primarily by bacteria, and (c) interaction of orthophosphate
     with iron oxyhydroxides	110
  4  Conservative dilution of nutrient from the Susquehanna River                   •
     with low nitrate seawater	113           ™
  5  Nutrient distributions in the main portion of Chesapeake Bay.  .   114
  6  Distribution of ammonium along a transect at (a)  38ฐ34'N,                       B
     (b) 38023'N, and (c) 38ฐ18'N	116           •
  7  Salinity in the Potomac River 	   119
  8  Dissolved oxygen in the Potomac River 	   120           •
  9  Chlorophyll ฃ in the Potomac River	121           B
 10  Nutrients in surface water of the Potomac River	122
 11  Suspended sediment in the Potomac River 	   123
 12  Nitrogen and phosphorus content in Chesapeake Bay 	   127           M
 13  Flux of particulate organic carbon through Chesapeake Bay .  .  .   130           •
 14  Phosphate uptake kinetics for a natural phytoplankton
     population	131           m

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TABLES
Number
1 Half-Saturation Values and Maximum Uptake Velocities for
2 August Respiration and Regeneration Rates for Total Plankton,
Plankton Passing through Mesh, and Plankton Passing through
Filters 	
3 February Respiration and Regeneration Rates for Total
4 Phytoplankton Grazers and Percent Daily Phytoplankton
5 Ammonium and Phosphate Flux from Chesapeake Bay Sediments . . .
106
Page
132
136
1 Qฃ
1 17
U/
140

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                                  SECTION 1

                                INTRODUCTION
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    A principal characteristic of Chesapeake Bay (Figure 1)  is that,  like
other partially mixed estuaries,  its two-layer circulation pattern enhances
the retention of nutrients.   Although the flushing time for water in                M
Chesapeake Bay is about one  year  (based on the basin volume and annual             •
river flow), nutrients are not flushed out to sea in direct proportion.
Instead, soluble nitrogen and phosphorus are incorporated into particles,          _
such as phytoplankton, which sink from the seaward-flowing,  surface water          I
into the landward-flowing, deep water.  In this way, nutrients entering            •
from the tributaries are carried  part way down the estuary,  sink toward the
bottom, and are carried back upstream.  This accumulation phenomenon  is the        •
mechanism for desirable, high production on the one hand, and undesirable,          |
over-enrichment on the other.
    This chapter deals with  the shaded portion of the binary diagram  in            •
Figure 2.  In this portion,  dissolved nutrients become particulate (biotic          •
component).  (Abiotic particulate nutrients, such as phosphate flocculants,
are not discussed in this chapter.)  The dissolved, and biotic particulate
nutrient compartments are expanded in Figure 3a to show the different              M
categories of dissolved and  particulate constituents that will be discussed        •
in the following sections.  The soluble forms of inorganic nitrogen and
urea are illustrated in Figure 3b.  The transformations among these                m
constituents are generally mediated by bacteria, but all four forms may be          I
taken up and utilized by phytoplankton in Chesapeake Bay (McCarthy et al.
1977).  Inorganic phosphorus, on the other hand (Figure 3c), is present
primarily as orthophosphate, which may interact with adsorbing minerals            •
such as iron oxyhydroxides under certain chemical conditions (Taft and             ™
Taylor 1976a).
    This chapter has three purposes.  First, it is intended to acquaint the        •
non-scientist with fundamental concepts of the major estuarine processes           |
related to water quality.  Second, it illustrates the concepts with data
from Chesapeake Bay or its tributaries.  Finally, it relates the processes          ซ
to management concerns with the hope that decision-makers will gain insight        I
into the relations between water quality, the controlling estuarine
dynamics, and potential management options.
    The uptake of nitrogen and phosphorus by phytoplankton is a major              •
pathway in the nutrient retention scheme in Chesapeake Bay.  For this              •
reason, Section 2 will discuss pertinent details of phytoplankton
physiology, including patterns of nutrients available to phytoplankton and         •
factors affecting their growth and productivity.                                   |
    Another major pathway, also discussed in Section 2, is phytoplankton
consumption by zooplankton.   Zooplankton recycle some of the nutrients in          _
the phytoplankton back into the water, assimilate some into body tissue,           W
and release the remainder as particulate material which sinks to the
bottom.  This material, comprising detritus, is colonized and further
degraded by bacteria, forming a third pathway that returns nutrients to            •
deep water flowing back upstream.  Nutrient recycling from the organic             |
forms  to the soluble  inorganic forms requires oxygen utilization.  Section
3 discusses oxygen sources and plankton respiration rates in relation to
nutrient retention and recycling.
                                    107
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Figure 1.   Map of Chesapeake Bay showing western shore tributaries
           and stations routinely sampled for biological and chemical

           data.

                                    108

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    Since the readership of this paper may vary from citizen to scientist.,         •
the format will try to accommodate a range of technical expertise.   The            |
indented sections explain, in less technical terms, important concepts the
reader should understand.  The concepts are illustrated as much as  possible        ^
with data from the Chesapeake Bay estuarine system.                                •
                                     111
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                                  SECTION 2

              NUTRIENT  AVAILABILITY AND PHYTOPLANKTON PHYSIOLOGY
PATTERNS OF NUTRIENT AVAILABILITY

Open Bay

    The annual nutrient cycle in Chesapeake Bay is marked by three
prominent events.  The first is the substantial nitrate input with winter
and spring runoff from the Susquehanna River (Carpenter et al. 1969).  The
source of nitrate in the runoff is partly ground water and partly
atmospheric.  Rain and snow contain nitrate concentrations of up to
one-third to one-half those in the runoff (Smullen 1982).  Dilution in the
upper Bay (Figure 4 and Figure 5) followed by phytoplankton uptake in the
mid- and lower Bay depletes this nitrate from about 40 to 100 ug atom L~l
to less than one ug atom L~l by midsummer.  Figure 4 shows how nitrate is
depleted toward the Bay mouth; Figure 5 shows its seasonal presence.   The
bottom diagram shows nitiatr present in May, but undetect iMe in August
(not shown in Figure).  In contrast to the heavy input of nitrate,
orthoposphate is undetectable throughout spring (top diagrams).
    The second important event occurs during midsummer when very low oxygen
concentrations in deeper Bay water permit release of phosphate and
accumulation of both phosphate and ammonium there (Taft and Taylor 1976a,
1976b).  Some of these nutrients are transported by diffusion and advection
to the upper layers where they are incorporated into phytoplankton.  The
annual maximum for total phosphorus in the surface layer of the Bay usually
occurs in summer, because phosphorus availability is greatest then.
However, not all of the deep water phosphorus reaches the upper layer.  New
information suggests that some phosphorus may be precipitated by iron-rich
minerals at the boundary between the upper and lower water layers (Figure
3c).  This natural control of phosphorus at the boundary may, at times,
prevent all of the nutrient from being available to the many non-motile
phytoplankton.  Strong swimmers such as the dinoflagellates, however, may
migrate down to the nutrient-rich layer at night and up into the sunlight
during the day.  As a result, their growth is not limited by phosphorus
availability.
    The third event is the fall nitrite maximum observed in both mid-Bay
(McCarthy et al. 1977) and in the lower Potomac River estuary (Taft,
unpublished data).  At present, ammonium oxidation appears to be the most
probable mechanism to explain these observations (Figure 3b).  An
experiment was conducted as part of the Chesapeake Bay Program to measure
the rates of this important process; results are discussed in Section 3.
    Although several studies have examined the longitudinal (vertical)
nutrient distributions in the Bay, none have explored the lateral
distributions.  Since lateral integration of parameters is a common feature
in one and two dimensional models, it is necessary to show that lateral
changes are small compared to longitudinal, or vertical changes.  When such
lateral measurements were made during April, 1977 they revealed an
interesting picture.  A layer of ammonium was observed at mid-depth (Figure
                                     112

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                                                                                   I
6), extending over much of the northern half of the Bay.   This  feature was          B
not observed during subsequent summer and winter cruises.   At present, the          B
best explanation is that ammonium-enriched deep water is  displaced westward
and upward by sea water, flowing in along the bottom on the eastern shore.          •
This view is particularly well supported by Figure 6a in  which  the maximum          B
value of nine ug atom NH^-N L~l is found on the bottom along the
eastern shore sill (station #834A), but is at mid-depth in the  eastern             ^
channel (station 834C) where it has been displaced upward.  Thus,  this             B
action pushes nutrient-rich water upward to the photic zone where  it is            ™
available to phytoplankton.
Tributaries                                                                        jtt
    The Potomac River was selected as a representative tributary because of         B
the extensive data on nutrient processes available.  The  analogue  between
the Potomac and Bay is further described in the forthcoming                        ซ
"Characterization of Chesapeake Bay" report.  The patterns of nutrient             B
availability in the Potomac River have been studied extensively for the
last 20 years.  This interest was stimulated by the necessity to discharge
sewerage from Washington, DC into the river near the head of tide.                 B
Carpenter et al. (1969), Jaworski et al. (1972), McElroy  et al. (1978), and         B
others have examined nutrient dynamics and budgets.  Najarian and  Harleman
(1977) and Najarian and Taft (1981) have modeled nitrogen dynamics using           M>
data from the Potomac.  Much of the following discussion is true not only          B
for the Potomac, but for the main Bay.
    The Potomac River is somewhat similar to the main Bay with  respect to
the availability of nutrients.  The lower Potomac displays the  same summer          B
release of phosphorus and the fall nitrite maximum (Taft,  unpublished data)         B
as described for the main Bay.  There is not the same extensive spring
nitrate influx, however.  The sewage effluent from the Blue Plains                 m
Treatment Plant is a major source of nutrients to the Potomac;  its effect          B
on the availability of nutrients in the Potomac is discussed in the
following paragraph.
    Data are presented here for June 1977 to orient the reader; this is not         B
intended as a comprehensive treatment.  Figure 7, Figure  8, and Figure 9           B
show longitudinal distributions of salinity, dissolved oxygen,  and
chlorophyll ฃ in the Potomac River.  Figure 10 depicts surface  nutrient            M
concentrations.  Ammonium entering the river from the Blue Plains  Sewage           B
Treatment Plant is diluted as it moves downstream but is also oxidized to
nitrite and then to nitrate.  The nitrite peaks at mile 80, and the nitrate         —
peaks slightly farther downstream from there.  Thus, nitrogen from Blue            V
Plains is detectable in one form or another for 30 miles  from the
discharge.  Phosphate, likewise, was detectable from mile 90 down to mile
60.  However, unlike the nitrogen forms, phosphate increased again in the          M
turbidity maximum region of the river, possibly because of release from the         B
sediments (Boynton et al. 1980).  The location of the turbidity maximum, a
region where sediment and associated phosphate is continually resuspended,
is shown in Figure 11, between river miles 55 and 65.
                                       115
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                                 122

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FACTORS AFFECTING PHYTOPLANKTON GROWTH AND PRODUCTIVITY

Background:  The Requirements of Phytoplankton

    Phytoplankton photosynthesis, or primary productivity, requires
adequate light and nutrients.  These nutrients stimulate phytoplankton
growth which, in turn,  supports the remarkable productivity characteristics
of Chesapeake Bay.  Phytoplankton growth occurs as a result of
photosynthesis, the process by which phytoplankton use light to produce
energy-rich molecules that are used, in light or dark, to convert carbon
dioxide to carbohydrates and oxygen.

    Concept:  Nutrient Limitation
        The nutrition of higher trophic-level organisms in Chesapeake Bay
    ultimately depends on the phytoplankton and, to a lesser extent,  on the
    macrophytes.  The availability of nutrients, in turn, regulates plant
    standing crop, or biomass.  The notion that standing crop could be
    regulated by a single factor was expressed in 1840 by Justis Liebig,
    who stated that "growth of a plant is dependent on the amount of
    foodstuff which is presented to it in minimum quanity" (quote from Odum
    1971).
        In other words, a plant needs a certain amount of nitrogen and a
    certain amount of phosphorus to grow at the maximum rate.  If nitrogen
    is scarce, but phosphorus is abundant, growth is nitrogen-limited.  If
    the reverse is true, the plant is phosphorus-limited.  For maximum
    growth, both elements in their correct proportions are needed.
    Nutrient regulation of phytoplankton standing crop in Chesapeake  Bay is
    established by the natural annual cycles in nutrient inputs from the
    rivers, direct land runoff, and the sediments.  Minimum phosphorus
    availability occurs during spring and fall in the main portion of the
    estuary.  Thus, natural cycles cause the limiting nutrient to change
    over the year.

    Although photosynthesis requires nutrients, it appears that the
specific rate of primary productivity of the biomass is not directly
influenced by nutrient concentrations, because high productivity often
coincides with low inorganic phosphorus and nitrogen concentrations in the
euphotic zone.  The rate may be influenced more by intracellular nutrient
pool size and nutrient supply rates from external sources (tributaries,
sediments, recycling) than by extracellular concentration.
    Although biomass is nutrient-regulated in the sense of Liebig's
statement, the specific rate of primary productivity of the biomass is not
controlled by the nutrient concentrations found in the water.  Instead,
primary productivity is directly regulated by intracellular nutrient  pools,
and, of course, light.  The rate of internal nutrient replacement is
controlled primarily by the rate of nutrient supply to the environment, the
recycling rate.  Even under conditions of nutrient limitation of
phytoplankton biomass, recycling supports a healthy, productive ecosystem.
    Nutrients recycled in the water column may be considered as
"regenerated."  Those recycled in the sediments and those entering from the
land may be considered as "new," since they are being added to the water
column.  Comparison of nutrient flux estimates with productivity indicates
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that "new" nutrients could significantly support phytoplankton productivity          •
north of 39ฐN latitude (Chesapeake Bay Bridge) because of their greater              M
relative availability.  "New" nutrients are less available and, thus,  have
diminished importance to the south, where recycling seems to be the
dominant process providing nutrients for phytoplankton primary                       •
productivity.  "New" nutrients provided primarily by benthic biological and          W
chemical activity may have the dominant role in supporting phytoplankton
biomass increases in Chesapeake Bay as a whole.                                      •
    In summary,  the potential for phosphorus limitation in the tidal fresh           •
regions of Bay tributaries exists throughout the year.  This is because
blue-green algae, common in fresh water, can utilize nitrogen gas,  so  that
nitrogen cannot  become the limiting nutrient.  The term "potential" is               V
used, because light may also limit biomass in high turbidity regions.                 9
Phosphorus is limiting to biomass in the main portion of the Bay during
spring and fall.  Nitrogen is limiting in summer.  In winter, light or               •
phosphorus may be the limiting factor depending on inflow and cloud cover.           •

    Concept:  Regulation of photosynthesis by light
        In the presence of adequate nutrients, photosynthesis is controlled          •
    by both light quantity and quality.  The net rate of photosynthesis is           ^
    not constant, even during daylight hours.  Different organisms  seem to
    maximize photosynthetic efficiency during different times of the day.             •
    This means that results of experiments designed to determine the                 •
    photosynthetic rate are influenced by light quantity, by light  quality
    as effected by scattering and absorption in the water, and by time of
    day.                                                                             •

How Phytoplankton Respond to Nutrients

    Occasionally, the production of phytoplankton biomass sufficiently               j|
exceeds its loss through sinking, grazing, and flushing to permit algal
biomass accumulation in the main portion of the estuary (Loftus et  al.               ^
1972).  But most of the year, phytoplankton standing crop falls in  the               •
range of five to 30 ug chl a_ L"1, with the higher numbers in the upper
layer during cold weather.  Phytoplankton nutrition, as indicated by
particulate C:N:P atom ratios, reflects seasonal changes in nutrient                 tt
dynamics.                                                                            B

    Concept:  Particulate Nutrient Ratios                                            M
        Well nourished phytoplankton contain optimum amounts of the                  I
    nutrient elements, carbon, nitrogen, and phosphorus.  Field and
    laboratory experiments indicate that the ratio of atoms of these
    elements under optimum conditions, is approximately 106 atoms carbon to          •
    16 atoms nitrogen to one atom phosphorus.  This specific configuration           m
    is called the Redfield ratio after the oceanographer who first
    suggested it as a characteristic of well-nourished phytoplankton cells           fl|
    (Redfield et al. 1963).  Departures from the Redfield ratio provide              •
    information about depleted intracellular nutrient stores.

    Particulate samples collected on 12 Chesapeake Bay Institute (CBI)               V
cruises in  the main Bay during 1972 to 1976 give particulate N:P atom                •
ratios in spring usually between 30:1 and 45:1, suggesting phosphorus
                                        125
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deficiency with respect to phytoplankton nitrogen.   Some of these data are
depicted in Figure 12.  The rate of organic phosphorus utilization by
phytoplankton, a response to inorganic phosphorus deficiency, also peaks in
spring, supporting this interpretation (Taft et al. 1977).  In summer most
N:P ratios drop below 30, and organic phosphorus degradation is reduced.
The atom ratio of ammonium nitrogen to phosphate-phosphorus in the deep
water is about four to one (Taft and Taylor 1976b), and the soluble
nitrogenous nutrients in the euphotic zone are insufficient to allow the
biomass of the phytoplankton present to double (McCarthy et al. 1975).
This evidence suggests that the biomass of phytoplankton is controlled by
nitrogen in summer — a shift from the spring situation of biomass control
by phosphorus.
    In a nutrient-limited system, phytoplankton biomass is controlled by
the concentration of nutrients (assuming grazing, flushing, and sinking do
not occur).  PhytoplankLon productivity, however, appears to be fairly
independent of nutrient concentration.  Thus, although the rate at which an
individual phytoplankter is productive is relatively independent of
nutrient concentration, increase in population biomass does depend
primarily on nutrient concentration.
    A relationship between phytoplankton productivity and nutrient
concentration in the Bay is fairly difficult to demonstrate for several
reasons.  First, the highest production rates coincide with very low
extracellular concentrations of one or more nutrients.  In contrast to
Fournier's (1966) results for the lower York River, adding nutrients
singly, or in combination usually failed to stimulate primary productivity
in experimental incubations with natural Chesapeake Bay phytoplankton
assemblages (Taylor and McCarthy 1972).  Second, phytoplankton exhibit
preferences for certain forms of nutrients over others.

    Concept:  Nutrient Preferences
        It is energetically advantageous for a cell to take up reduced
    nitrogen in the ammonium form, because it can be incorporated into
    amino acids and proteins directly.  At ammonium concentrations below a
    threshold value, usually 1.0 to 1.5 ug-at L~l,  oxidized nitrogen as
    nitrite and nitrate are taken up as well (McCarthy et al. 1975, 1977).
    The cell must expend more energy to reduce these ions to ammonium, but
    the expenditure is justified.  Similarly, phytoplankton incorporate
    orthophosphate alone until concentrations fall  below threshold.  Then
    cells degrade simple organic phosphates to supplement cellular
    phosphorus nutrition.  Convincing evidence indicates that, because of
    phytoplankton preferences, much of the nitrate  entering in spring from
    the Susquehanna River passes through the upper  Bay, because ammonium
    concentrations are above threshold, to be utilized in the lower Bay
    where ammonium concentrations are below threshold.  The abundance of
    nitrogen allows orthophosphate concentrations to drop below threshold,
    and degradation of simple organic phosphates to be stimulated.

    Ammonium is selected preferentially over nitrate.  Although the
orthophosphate ion is generally the phosphorus source preferred by
phytoplankton, some species will grow equally well  in culture with an
organic mono-ester as the phosphorus source (Kuenzler 1965; Taft,
unpublished data).  However, like orthophosphate, mono-ester concentrations
                                        126

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usually approach detectability limits; no transition concentration (as
exists for preferred nitrogen species) is obvious for preferred phosphorus
species.
    Third, if nutrient concentrations do exert a regulating influence on
carbon fixation, it most likely occurs intracellularly near the enzyme
systems affecting final nutrient utilization.  As one nutrient molecule is
removed by enzyme activity from the substrate pool,  it could be replaced
from the dilute extracellular medium to retain necessary high
concentrations near the enzyme.  This hypothesized sequence leads to the
notion that coupling between carbon incorporation rates and nutrient
incorporation rates should be very close; this does occur under conditions
of high productivity (growth rate) and low nutrient concentrations in
chemostats.
    When growth rates are low, carbon fixation and nutrient uptake may
become uncoupled.  Eppley and Renger (1974) observed (for the diatom
Thalassiosira pseudonana) increased maximum uptake velocities for nitrate
and ammonium as growth rate decreased.  Orthophosphate uptake by P
deficient phytoplankton is frequently much more rapid than short-term
growth in culture (Ketchum 1939) or photosynthetic rate in Chesapeake Bay
(Taft et al. 1975).  The potential for one phytoplankter to incorporate
nutrients rapidly at low external concentration leads to the conclusion
that nutrient uptake should never be concentration-limited (Kuenzler and
Ketchum 1962).  Inability to demonstrate continuous, close-coupling between
carbon fixation and nutrient uptake, an.d elimination of the phosphate and
ammonium uptake steps as productivity regulating factors, also complicates
direct demonstration of nutrient regulation of phytoplankton primary
productivity.
    These observations lead us to conclude that neither ambient nutrient
concentrations, nor increased uptake potential resulting solely from
elevated nutrient concentrations, have Bay-wide significance in regulating
open water phytoplankton productivity.  Therefore, static measurements of
nutrient concentrations and other water quality parameters do not convey
enough information about the dynamic events taking place.  Optimal water
quality management requires information about processes and their rates.

How Phytoplankton Respond to Physical Processes

    Concept:  Phytoplankton are Distributed Unevenly in Space and Time
        The term "phytoplankton" implies a plant cell that has limited
    mobility; it is transported more by water movement than by swimming.
    The most advantageous use of swimming by phytoplankton is exhibited by
    the dinoflagellates that can travel vertically.   In the two-layered
    estuary, they have the capability to move from the seaward-flowing
    surface layer to the landward flowing deep layer and, thus, stay in the
    estuary.  They can also migrate from nutrient-poor, surface water to
    nutrient sources in the deep water or sediments.  Weaker swimming
    organisms and those, such as diatoms, which don't swim at all, depend
    on buoyancy and water movement to keep them in a suitable environment.
        The interaction of phytoplankton buoyancy or swimming with water
    motion produces a spatially patchy distribution of organisms.  The
    upward motion of cells against downward-flowing water can result in the
    accumulation of organisms near the surface of a so-called frontal
                                        128

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    region.  Growth of surface organisms can be stimulated by the upward            V
    motion of nutrient-rich deep water to the surface,  so that biomass              m
    increases in one area relative to nearby regions where such motion does
    not exist.                                                                      M
        Spatial distribution is also influenced by salinity of the water.            •
    Some species can adapt to a wide range of salinities and may be found
    throughout the estuary.  But many riverine and marine forms have very
    narrow salt tolerances so their occurrence is limited.                          •
        The temporal distribution of phytoplankton species depends                  V
    primarily on water temperature; some are considered summer species, and
    others are winter species.  If both temperature and salinity regimes            •
    are acceptable, the organisms survive long enough to be transported by          I
    circulation.

    The use of phytoplankton distributions as indicators of water movement          ft
has been demonstrated as a useful technique in Chesapeake Bay.  Moreover,            •
the significance of coupling between phytoplankton ecology and physical
processes in the estuary has been clearly established for one                       •
dinoflagellate species (Tyler and Seliger 1978).  This  research                     •
reemphasizes the necessity of examining estuarine processes in detail to
understand the system.  Further, research indicates that the tributaries
are very important sources of phytoplankton that may achieve local                  •
numerical dominance, and in some cases, biomass dominance in the main               9
portion of Chesapeake Bay.  Thus, the ecology of these  organisms is closely
coupled to physical processes in the estuarine system.                               •
    Movement of phytoplankton through the estuary can be roughly estimated          M
using a box model with particulate organic carbon (POC) representing the
phytoplankton.  Figure 13 shows the flux estimates for  (a) February, (b)
May and (c) August 1975, and (d) February 1976.  Units  are 10^ Ug atom C            •
sec~l.  Net POC flux was greater during the two winter  periods.  Vertical            9
transport of phytoplankton was dominated by upward movement over much of
the Bay.  This upward movement was due to minimum stabilization of the              ft
water column, which created high potential for mixing both salt ions and            ฃ
particles upward from the deep layer.  The source and sink terms, shown in
small boxes, represent nonconservative gains and losses of POC such as              _
growth, grazing, sinking, and disruption.  The net values of these                  •
processes were also higher over most of the Bay during winter than during            ™
spring or summer.  This information can help locate areas and times of high
activity that would, subsequently, increase phytoplankton biomass.                  •

Kinetic Measurements of Nutrient Uptake by Phytoplankton

    Environmental biologists began making kinetic measurements of nutrient          •
uptake by phytoplankton to obtain physiological information and predict
changes in species composition from changes in nutrient concentrations.
Nutrient uptake by phytoplankton proceeds at rates that are concentration-          B
dependent.  Uptake rate increases with increasing concentration up to some          Jp
maximum rate, beyond which it is constant regardless of concentration
(Figure 14).  The relation between substrate concentration and uptake rate          ซ
is usually expressed mathematically as a rectangular hyperbola.  Two                M
characteristic parameters of  this  form are the half saturation value (Ks)
and the maximum uptake velocity  (Vmax).  Ks is the substrate

                                                                                    V
                                        129
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            population containing primarily one dinoflagellate species.
                                      131
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concentration at which uptake velocity reaches one-half the maximum rate.
In this way, nutrient uptake is treated as an analog of enzyme kinetics,
reflecting the participation of enzymes and carrier molecules in the uptake
process.
    Concept:  Kinetic Parameters are not Constant
        The kinetic parameters Ks and Vmax are coefficients used in
    mathematical models.  However, they should not be considered
    "constants" because they are subject to variation, even within species,
    depending on environmental conditions, the organisms'  recent history,
    and the types of organisms present in a natural population.   Kinetic
    parameters determined with pure cultures can be employed in models of
    natural systems if the modeler recognizes that a factor of ten range in
    the values is not unusual.  Table 1 shows the range of Ks and Vmax
    values observed in Chesapeake Bay and Potomac River.  These ranges
    indicate differences in phytoplankton physiology.  As  the table shows,
    nitrogen values can vary by a factor of two or more.

TABLE 1.  HALF-SATURATION VALUES (Ks) AND MAXIMUM UPTAKE VELOCITIES
          (Vmax) FOR NUTRIENTS IN THE CHESAPEAKE BAY ESTUARINE SYSTEM
Nutrient                   Ks                             Vmax
                         ug atora-L                ug atom chl a  h"1
         Chesapeake Bay

Phosphate             0.09 to .172                0.004 to 0.160
Ammonium                 1 to 2                         	
Nitrate                  2 to 4                         	

         Potomac River

Phosphate               0.2 to 0.4                0.0005 to 0.0015
Ammonium                1.5 to 1.7                0.003  to 0.017
Nitrate                     1.2                   0.005  to 0.039
    Ks and Vmax are often considered constants for a particular
phytoplankton species for mathematical modeling purposes and for comparing
one species with another.  Ks is an indicator of the affinity between the
nutrient and the cell's uptake system; the smaller Ks, the greater the
affinity.  It has been a popular concept that a species with a lower Ks
can dominate when nutrient concentrations are low because of greater
affinity for the nutrient; a species with higher Ks can dominate only
when nutrients are high.  As a generality, this concept is acceptable.
However, Ks is not a true constant.  Modifications in the uptake system
or the membrane to which it is bound on the cell alter Kg.  Such
modifications may be related to the relative amounts of saturated and
unsaturated lipids in the cell membrane, to the cell's immediate history,
and to the intracellular nutrient supply.  Similarly, Vmax is not a true
constant.  It may be changed by membrane alterations or changes in the
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number of uptake sites per cell.  Since these kinetic parameters are not
constant, predictions of species shifts with changes in nutrient
concentrations have had limited success.  At best, shifts between green and
blue-green algae in fresh waters can be described based on nutrient loading          M
ranges.  Resolution beyond this remains to be developed.                             •
    It is possible, however, to describe a hypothetical relationship
between nutrients and commercial species based upon results from culture
experiments with a variety of organisms.  From these experiments, it is              •
known that not all phytoplankton species have equal nutritional value for            V
the planktivores that graze them.  High diversity of phytoplankton species,
in a natural population favors a balanced diet for the grazers.                      •
Modifications of the nutrient regime, which cause species shifts and reduce          •
population diversity, may increase the potential for deficiencies in the
grazer diet.  Thus, the yield of filter-feeding commercial species, such as
oysters and menhaden, could be influenced indirectly by nutrient inputs to           •
the system.                                                                          H

Summary                                                                              A

    In summary, the best Bay management requires an understanding of the
major processes affecting growth and reproduction of phytoplankton because
the ecology of phytoplankton is closely coupled to physical processes of             ft
the estuary.  These influences include the effect of light, nutrients, and           9
physical and chemical processes on phytoplankton, and how quickly
phytoplankton assimilates nutrients.                                                 •
    In the presence of adequate nutrients, photosynthesis is regulated by            •
light.  Specifically, the quality and quantity of light affect the rate of
photosynthesis in phytoplankton.  However, in a nutrient-limited system,
such as the Bay, the presence of P or N in the smallest amount regulates             •
phytoplankton standing crop.  Phosphorus is limiting in the main Bay in              9
spring and fall, with N limiting during summer.  In winter, light or P can
be the limiting factor.  The availability of these nutrients is controlled           •
by the recycling rate, or the rate of nutrient supply to the environment.            •
"New" nutrients, or those recycled in the sediments and entering by land,
provide the major source to phytoplankton and probably are the causes of
increases in biomass of Chesapeake Bay as a whole.                                   I
    The uneven distribution of phytoplankton in the Bay results from their           •
responses to physical and chemical processes.  Mobility of some
phytoplankton species enables them to overcome circulation patterns.  They           •
can move vertically between layers of the Bay and migrate to nutrient-rich           •
areas.  Circulation of the Bay brings, to certain areas, upward-moving,
rich waters; in these areas, growth of surface phytoplankton is                      _
stimulated.  Salinity limits the distribution of some phytoplankton, but             •
others dependent on water temperature will only persist at certain times of          ™
the year.
    Measuring the rate of nutrient uptake by phytoplankton can indicate              A
species shifts in phytoplankton and consequences on organisms higher in the          ฃ
food chain.  A certain species of phytoplankton with a slow uptake rate
will produce less biomass in a given time than a phytoplankton with a                _
faster uptake rate.  The latter species would dominate, perhaps causing a            •
bloom.  Diversity  in phytoplankton favors a balanced diet for grazers,               *
which may ultimately influence  the yield of filter-feeding Bay resources
such as oysters and menhaden.                                                        •
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                                  SECTION 3

                              NUTRIENT CYCLING
INTRODUCTION

    The flow rate of nutrient molecules through remineralizing processes to
the inorganic forms may be an important factor regulating productivity.
These recycling processes include (1) grazing of the phytoplankton standing
crop by macro- and micro-zooplankton, followed by nutrient release through
excretion or heterotrophic bacterial activity; (2) activity of free-living
aquatic bacterial heterotrophs; (3) nutrient release from the sediments  by
both biological and chemical processes; and (4) nutrient transport by
physical processes into contact with phytoplankton able to assimilate the
nutrient.
    The basic elements in a living system are carbon,  oxygen, hydrogen,
nitrogen, and phosphorus.  Carbon, oxygen,  and hydrogen are readily
available to plants in the biologically usable compounds,  oxygen gas,
carbon dioxide, bicarbonate ion, and water.  Nitrogen and phosphorus,
however, are not so abundant in a useable form.  The cycling of these
nutrients in surface waters from the dissolved inorganic form to the living
form and back to the dissolved inorganic form, is the mechanism by which
the photosynthetic conversion of the more abundant elements into
metabolically useful compounds is maximized in the aquatic environment.
    About 90 percent of the primary productivity in Chesapeake Bay is
accomplished by planktonic algae that pass through a 35 urn mesh (McCarthy
et al. 1974).  These organisms are the principal food of zooplankton in  the
Bay, which become food for higher organisms.  Studies of the larger
zooplankton in Chesapeake Bay reveal that 50 to 70 percent of the animals
caught on 103 um mesh are copepods of the genus Acartia (Rupp 1969).
Acartia tonsa is also abundant in the Patuxent River estuary (Heinle
1966) .  Copepods of the genus Eurytemora are seasonally abundant and are of
the same size as Acartia.
    Previous studies reveal that grazing macro-zooplankton (adult copepods)
consumed only about 10 percent of the daily phytoplankton productivity in
Chesapeake Bay (Storms 1974).  Therefore, the role of micro-zooplankton  in
grazing phytoplankton and in returning nutrients to the water was
examined.  It now appears that the most significant role of the
micro-zooplankton is to respond, through rapid growth, to graze blooms of
phytoplankton that occur periodically in the Bay (Heinbokel, unpublished
data).  Data are now becoming available on protozoa and metazoa, that are
smaller than the common copepods.  As a group, the zooplankton inhabiting
the estuary south of the Bay Bridge play a major role in regenerating
nitrogen and phosphorus to meet the requirements of the phytoplankton on
which they feed.

    Concept:  Nutrient Cycling
        Nitrogen and phosphorus are converted from the inorganic, to
    living, organic forms and back again on varying time scales in the
    Chesapeake Bay estuary.  For simplicity of illustration, here,  the time
    scales are divided into short-term (minutes to weeks)  and long-term
    (months to years).  It is also convenient to conceptualize that short-
                                        134

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    term cycling occurs primarily in the water and the surface sediments             •
    and long-term cycling takes place primarily in the deep sediments (more          •
    than two cm below the surface).
WATER COLUMN PROCESSES

Respiration
                                        135
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    Respiration rate is measured as the rate of oxygen consumption of a
water sample incubated in a darkened container.  It is possible, by                  ^
measuring the plankton respiration rate accurately and precisely, to                 •
estimate C, N, and P regeneration in the water column, using a suitable              •
respiratory quotient and particulate C:N:P ratio.
    Results presented here are from two experiments at natural plankton              •
densities performed by Dr. Eric Hartwig with a sensitive photoelectric               H
oxygen titrator.  A suitable respiratory quotient (RQ) must be used to
convert oxygen consumption to the amount of organic carbon degraded.  The            .
respiratory quotient is the ratio of carbon dioxide produced to oxygen               •
consumed by an organism.  Commonly determined RQ values range from 0.27 in           ™
an intertidal sand flat to 1.6 for Chlorella using nitrate as the nitrogen
source (Teal and Kanwisher 1961, Pamatmat 1968).  For the purposes of this           •
report, an RQ of 0.85 will be assumed, with the realization that deviation           ฃ
in RQ of ^0.20 encompasses most RQ measurements found in the literature and
yields a +25 percent variability, which is within acceptable limits.  The            _
incorporation of C:N:P atom ratios, into the calculation, yields estimates           I
of inorganic nitrogen phosphorus regeneration rates.  The atomic ratio of            ™
Redfield et al. (1963) (106 C to 16 N to 1 P) will be used.
    The winter respiration rates given in Table 2 and Table 3 were 63                •
percent of the summer rates (August).  The water temperature difference              f
between February and August was approximately 25OC (77ฐF).  If the
respiration rate of the organisms present doubled for each 10ฐC (50ฐF)               •
temperature change (Q10 = 2), the February rates would only be 20 percent            •
of the August rates, other factors being equal.  This implies that the
thermal regime of Chesapeake Bay exerts a selection pressure on microbial
communities so that bacterial species change during the year as the                  •
temperature changes.  Temperature changes of the magnitude existing in               V
Chesapeake Bay were found by Sieburth (1967) to cause shifts in the thermal
types of microbes present in Narragansett Bay, Rhode Island.  Thermal                fl|
selection of bacterial species, adapted to either warm or cold                       •
temperatures, may be a factor permitting maximum utilization of organic
substrates throughout the year.
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TABLE 2.  AUGUST RESPIRATION AND REGENERATION RATES FOR TOTAL PLANKTON (TP),
          PLANKTON PASSING THROUGH 35 urn MESH (<35 urn) AND PLANKTON PASSING
          THROUGH 3 urn FILTERS ซ3 urn)


Station
904N

853F


834G
818P
744


7070

Potomac
Estuary

Respiration rate
ug atom Qฃ
Sample L~l h-1
Surface TP 4.9
7m TP 5.2
Surface TP 3.4
< 3um 2 . 7
6m TP 7.1
Surface TP 4.6
Surface TP 3.6
Surface TP 4.6
<35 urn 4.1
< 3 urn 2.3
Surface TP 2.4
10 m TP 2.1
Surface TP 2.5
< 3 urn 1.2
Estimated
N regeneration
ug atom N
L-lh-lxlO-1
6.3
6.7
4.4
3.5
9.1
5.9
4.6
5.9
5.3
3.0
3.1
2.7
3.2
1.5
Estimated
rate P regeneration rate
ug atom P L~l
h-lxlO-2
3.9
4.2
2.7
2.2
5.7
3.7
2.9
3.7
3.3
1.8
1.9
1.7
2.0
0.96

TABLE 3.

FEBRUARY RESPIRATION AND REGENERATION RATES
SAMPLES

FOR TOTAL PLANKTON


Estimated Estimated
Station
904N


834G

804C

744

7070

Calvert
Cliffs
Nuclear
Respiration rate
ug atom Qฃ
Depth L-lh-lxlO~3
2m 2.1
2m 2.5
lira 0.85
2m 3.3
9m 1.3
4m 2.3
20m 1.4
2m 1.7
10m 1.3
1m 3.5
10m 2.8
Intake 1.3

Discharge 2.2
N regeneration
ug atom N
L-*h- 1x10-1
2.7
3.2
1.1
4.2
1.7
3.0
1.8
2.2
1.7
4.5
3.6
1.7

2.8
rate P regeneration rate
ug atom P L~l
h-lxlO-2
1.7
2.0
0.68
2.7
1.0
1.9
1.1
1.4
1.0
2.8
2.3
1.0

1.8
Power Plant

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TABLE 4.  THE MAJOR PHYTOPLANKTON GRAZERS AND PERCENTAGE OF DAILY
          PHYTOPLANKTON PRODUCTION USED
     Animal                      percent daily phytoplankton production used
  larval stages of small biota
  planktivorous fish
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    An important aspect of the water-column-nutrient-regeneration rate              •
concerns its coupling with the nutrient supply required for primary                 9
productivity.  Estimates of upper Bay productivity values for August [4 ug
atom C(L'h)-1] and February [0.6 ug atom C(L-h)"1] (Taylor,                         •
personal communication), with a C:N:P assimilation ratio of 106:16:1,  yield         •
a requirement for 0.6 ug atom N (L-h)-l and 0.04 ug atom P (L-h)~l
in August and a requirement for 0.09 ug atom N (L-h)~l and 0.005 ug                 —
atom P (L-h)-l in February.  Table 2 and Table 3 show estimates of                  •
regenerated N and P, based on respiration measurements (Taft et al. 1980).          ™
These data indicate that respiration could regenerate most of the nutrient
requirement for the upper Bay (stations 904N, 853G, 818P, 804C) in August,          •
and an excess of nutrients in February.  As a result, addition of further           ฃ
nutrients in August would increase biomass, but addition of nutrients  in
February would result in nutrient accumulation in the water column.                 ^

Grazing                                                                             •

    Grazing is the process by which herbivores, such as copepods, consume           •
primary producers (phytoplankton).  The grazers in Chesapeake Bay span the          |
range from small ciliates, to rotifers and copepods, all the way up to
crustacean and fish larvae, and adult planktivorous fish such as menhaden.          ^
The ecological role of these grazers is to transfer the organic material            •
and energy fixed by the phytoplankton through the food web.  The grazers            ™
themselves are consumed by higher predators such as the carnivorous fishes,
waterfowl, and humans.  Grazing keeps estuaries in balance by restricting           •
phytoplankton populations.                                                          |
    However, not all of the primary production is assimilated into
animals.  Some nutrients are released back into the water, directly by              .
excretion, or indirectly, by bacterial degradation of dead cells or animal          •
fecal material.  In this way, the grazers help keep the estuary productive          *
by grazing the phytoplankton standing crop and supplying nutrients for
continued phytoplankton growth (Table 4).  Thus, nutrients entering the             0
estuary are distributed throughout the food web and may be cycled through           0
the planktonic ecosystem several times each year.  One of the major goals
of biological studies in Chesapeake Bay is to quantify recycling rates,             •
including the contributions from grazers.                                           I
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Copepods                                       up to 15
Microzooplankton                                     15                              _
Other                                                70                              •
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Copepods—
    Copepods are small crustaceans inhabiting the estuary.  Common species
are Acartia, Eurytemora, Temora, and Centropages.  Copepods have a somewhat
complex life cycle.  Like most crustaceans, they exhibit several life
stages from nauplius to copepodite to adult.  All of these stages graze
phytoplankton.  The grazing may be accomplished by encounter feeding,
active hunting of single cells, and filter feeding.  The adults have
specialized feeding appendages that sweep through the water, directing the
phytoplankton cells to the mouth.  Some copepods seem to graze selectively
upon particular size cells, especially if one size range contains a large
fraction of the standing crop.
    The copepods found in Chesapeake Bay, particularly the adults, have
been fairly well studied.  The adults usually number from one to ten per
liter in the main portion of the estuary.  They graze one to 15 percent of
the daily phytoplankton production.  Less is known about grazing by early
life stages but, by analogy to studies of oceanic copepods, it is accepted
that naupliar stages may graze three to five times the adult rate per unit
of body weight.
    Nutrient cycling rates by copepods can be estimated by assuming 30
percent assimilation efficiency, 60 percent incorporation into fecal
material, and 10 percent direct excretion.  If copepods grazed 10 percent
of the daily phytoplankton production, three percent of the daily
production would be assimilated into copepod tissue (30 percent of 10
percent), six percent would be released as particulate fecal material, and
one percent would be directly excreted.  Nutrients would be similarly
distributed, with about one percent of the phytoplankton nitrogen and
phosphorus returned directly to the water, and about one-half of the six
percent fecal nutrients returned by bacterial activity.
    It is clear, by comparing phytoplankton growth with copepod recycling
of nutrients, that copepods are a small component of the nutrient cycling
system.  The phytoplankton grow and divide about once every one or two days
in spring, summer, and fall, but the phytoplankton standing crop does not
double each day, indicating that the loss due to grazing approximately
equals the phytoplankton growth rate.  Since copepods are only eating one
percent to 15 percent of the daily production, other organisms must consume
the remaining 85 to 99 percent.

Micro-Zooplankton—
    The micro-zooplankton are those grazers whose size approaches that of
the phytoplankton cells.  The ciliates and small rotifers may be included
in this group.  In addition to size similarity, the ciliates have growth
rates and generation times similar to phytoplankton, whereas rotifers and
copepods have long generation times compared to the phytoplankton.
    Less is known about micro-zooplankton abundance distribution in
Chesapeake Bay.  Recent studies at CBI reveal that ciliates consume about
15 percent of the daily production Bay-wide.  Therefore, their contribution
to grazing pressure and the recycling of nutrients is probably only
slightly greater than that of the copepods.  Experiments conducted as part
of the Chesapeake Bay Program (CBP) indicate that nitrogen is recycled by
micro-zooplankton at the rate of about 0.05 ug atom NH4~N L-^h-1.
This represents about 10 percent of the phytoplankton requirement for
nitrogen.
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Bacterial Activity                                                                  •

    Bacteria are heterotrophic organisms that are probably numerically-
dominant in the estuary.  Bacterial abundance is thought to be one to ten           •
million cells per milliliter of water.  A major role of these organisms is          •
to metabolize organic material during which some inorganic carbon,
nitrogen, and phosphorus are recycled.  These metabolic processes consume           •
oxygen and, at times, may be the dominant oxygen-consuming process.                 •
    Important groups of bacteria involved in nutrient cycling are
Nitrosomonas and Nitrobacter.  The genus Nitrosomonas oxidizes ammonium to
nitrite.  Nltrobacter then further oxidizes nitrite to nitrate.  These              •
reactions probably occur in oxygenated sediments year round, but are most           m
conspicuous during the late summer and fall in Chesapeake Bay when ammonium-
rich deep water is re-oxygenated.  The ammonium is rapidly oxidized to              m
nitrite that reaches relatively high concentrations throughout the Bay.             •
The second oxidation step to nitrate has been observed less frequently than
the first.
    An experiment was conducted under the CBP to specifically examine this          •
                                                                                    •
phenomenon.  Ammonium was oxidized at the rate of 0.05 ug atom
L~l h~l by planktonic bacteria.  During the process, about one percent
of the NH4-N was converted to gaseous N20.                                          •
    A considerable amount of research has been done on a few kinds of               •
bacteria in Chesapeake Bay, such as the shellfish pathogens, but little has
been done quantitating the role of bacteria in nutrient recycling during
the winter, fall, and spring.  The bacterial contribution to recycling has          •
usually been estimated from oxygen consumption, or obtained by difference           B
calculation rather than measured directly.  At best, there are
fractionation studies wherein water samples are passed through various size         •
filters, and the oxygen consumption of each fraction is measured.  The              I
results of three such experiments are shown in Table 2 for samples passing
through a 3 urn filter (labeled <3 urn).  Based on the respiration of the
fraction containing the bacteria, these organisms have the potential to             •
recycle 10 to 100 times more nitrogen and phosphorus than the copepods or           ™
the micro-zooplankton.  However, under conditions favorable to bacterial
growth, bacteria may incorporate nutrients rather than recycle them to the          •
                                                                                    |
water.
SEDIMENT PROCESSES
                                        139
                                                                                    •
    The sediments are an integral component of the nutrient cycling system
in Chesapeake Bay.  Nutrients accumulate in estuaries, because they are             tt
incorporated into particles that sink to the bottom.  These organic                 m
particles may remain on the surface or be mixed down into the sediment by
benthic animals.  Benthic animals and bacteria degrade the organic                  ^
particles,  incorporating some of the material into their own structure and          •
regenerating some as inorganic carbon (CC^) , nitrogen (NH4+), and
phosphorus  (P0zj3).  if regeneration occurs  on the sediment surface,
the nutrients will be returned directly to  the water.  However, if                  •
regeneration occurs deeper in the sediments, the nutrients may be dissolved         B
in the  sediment  interstitial waters.  This  results in interstitial waters
having  relatively high concentrations, several hundred micromolar, of
ammonium and phosphate.
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Nutrient Flux

    The flux of nutrients out of the sediments is largely dependent on two
processes.  One is degradation directly on the sediment surface.   The other
is diffusion of nutrients out of the sediments,  based upon the
concentration gradient in the interstitial water.  Direct release to the
water can be estimated from the sediment-oxygen demand, as is done for
water-column- regeneration estimates.
    Diffusion of nutrients out of the sediment can be calculated  from the
concentration gradient and the physical characteristics of the sediment.
These calculated values are minimum values for nutrient flux out  of the
sediments.  Several other factors, difficult to quantify, have roles in
moving nutrients out of the sediment.  One of these factors is stirring of
the sediments by benthic animals.  Another is the lateral diffusion of
nutrients into animal burrows, followed by turbulent diffusion or advection
up the burrow to the sediment-water interface.  A third possible  factor is
hydrostatic pumping of water as a surface wave passes.  Theoretically,
large hydrostatic pressure under a wave crest could pump water out of the
sediment under an adjacent wave trough, where hydrostatic pressure is less.
    Another way to determine nutrient flux from sediments is by placing a
chamber on the bottom to isolate a portion of the sediment-water
interface.  Flux rate is then determined from nutrient concentration
changes in the water contained by the chamber.  Since this method may also
introduce some artifacts, we consider flux rates obtained in this way to be
maximum potential values.
    During the course of the CBP, nutrient flux from the sediments was
studied by both the diffusion and chamber method.  Table 5 summarizes the
results.  For ammonium, the diffusion value is usually about one-fourth to
one-half of the measured chamber value.  This is because processes at the
sediment surface (bioturbation and other biological processes) increase the
flux of nutrients over that permitted by diffusion alone.  The actual
ammonium flux from undisturbed sediments lies between these two values and
is probably closer to the higher one.  At present, this is the best
estimate that can be made from this data.

TABLE 5. AMMONIUM AND PHOSPHATE FLUX FROM CHESAPEAKE BAY SEDIMENTS
         EXPRESSED AS ug atom m~2 IT1.  POSITIVE IS OUT OF THE SEDIMENT
Location
      Ammonium
Diffusion   Chamber
        Phosphate
*Diffusion       Chamber**
Worton Creek
Hart-Miller Island
Sharp's Island
Kenwood Beach
Todds Cove
Gwynn ' s I s 1 and
Pocomoke Sound
50
52
171
184
37
68
93
177
102
455
670
410
262
430
1.1
0.9
16.3
15.3
3.8
5.1
9.6
-4.2
2.3
0
40
16
10
-3.2

 * TOP
** DIP (Boynton)
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Sorption - Desorption Reactions
    Phosphate participates  in geochemical processes  in the  sediments.  A
                                        141
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    In contrast, the phosphate flux values from diffusion calculations and           •
chamber measurements are more similar than the ammonium values, but
negative values are sometimes observed.  This reflects the uptake of
phosphate by sediments, a process which partly results from sorption by              •
sediment particles.                                                                  •
    The magnitude of the sediment flux of ammonium and phosphate can be
illustrated by comparing the amount of nutrient being added with the total           •
amount already in the water.  Consider, for ammonium in the water column 1           I
m~2 ซh~l, the ammonium concentration in the water would increase by

         100 ug atom-h-1        ,n     „      _o   ,  •,                               |
         	  = 10 ug atom • m J • h~l                               •
              10 m3                                                                  "

or 0.01 ug atom L~l h~l each day.  The water would gain                              B
0.24 ug atom L~l • d~l.  If the total nitrogen concentration is 25 ug                •
atom L~l, the benthic flux increases the nitrogen content of the water by
about one percent per day.  (Sedimentation removes nitrogen from the water           •
so a cycle is maintained.)  This calculation can be used to evaluate the             •
nitrogen concentration, in water from the flux measurements in Table 5.
I
    Whereas ammonium leaves the sediments continually during the annual
cycle, phosphate release takes place primarily in the summer.  This results          •
from the interaction of phosphate with iron at the sediment-water                    •
interface.  In the presence of oxygen, iron is present on the sediment
surface as solid iron oxyhydroxides.  The phosphate diffusing upward in the          —
interstitial water is apparently adsorbed onto these solids that block               •
phosphate flux into the overlying water.                                             ™
    When the overlying water becomes anoxic in the deeper parts of the
estuary during summer, a two-step release process occurs.  First, the iron           •
oxyhydroxides are reduced and dissolved, releasing both iron and phosphate           |
into the water in a pronounced pulse.  Second, with the block removed,
phosphate in the interstitial water diffuses freely into the overlying               ซ
water, but more slowly than the initial release.  When the deep water is             •
reoxygenated in late summer, the phosphate concentration declines rapidly.           ™
We hypothesize that sorption reactions involving newly-formed iron
oxyhydroxides are responsible for a significant fraction of this phosphorus          •
removal.                                                                             f
    The residence time of nitrogen and phosphate in the sediments cannot be
measured directly.  From the relatively high interestitial water                     ป
concentrations, we estimate a rather long residence time for some fraction           I
of the nutrients.  As much as one-third of the nitrogen could be
permanently buried in the sediments.  For the remaining 70 percent of the
nitrogen and for much of the phosphorus, the residence time may be rather            •
short, on the order of months to a few years.  Additional research is                •
required to further test ideas about processes influencing the residence
time, and about the size (depth) of the considered sediment reservoir.               •

Geochemical Reactions
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detailed evaluation is beyond the scope of this discussion.  The reader is
referred to Bricker and Troup (1975) and Bray et al. (1973) for information
on the equilibrium chemistry of phosphate minerals in sediments.


Marshes and Bay Grasses


    The marshes and Bay grasses along the shorelines of the Bay and its
tributaries serve as both sources and sinks for nutrients.  At present,
there is not complete agreement as to whether marshes are net sources or
net sinks of nutrients.  During the growing season, marsh plants assimilate
nutrients from the water.  Nitrogen fixation by some species may be
significant when the water is nitrogen deficient.  In winter, organic
material may be periodically flushed out of the marshes to the adjacent
open waters.  Similarly, submerged aquatic vegetation (SAV) absorb
nutrients during the growing season and contribute organic material to the
system during the winter.
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                                  SECTION  4


                       DISSOLVED  OXYGEN  IN THE  ESTUARY
                                                                                     I



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OXYGEN SOURCES

    Dissolved oxygen is of primary interest to water quality managers,               •
because it directly affects the well-being of aquatic life.  Sources of
oxygen include diffusion from the surface, photosynthesis, and reduction of          —
oxidized chemical species.  Oxygen is lost from the water through                    •
respiration and oxidation of reduced chemical species.                               ••
    Oxygen gas enters the water by two major mechanisms; diffusion and
bubble entrainment at the air-water interface transfer oxygen to the                 •
water.  The rate of transfer depends on temperature, sea state, wind                 I
velocity, and oxygen concentration in the water.  Surface turbulence and
low temperature enhance both the exchange and the solubility of oxygen in            .
estuarine water.  Salinity also exerts an influence, but it is small                 I
compared to the other parameters.                                                    *
    Photosynthesis is the second mechanism by which gaseous oxygen enters
the system.  Oxygen is a product of photosynthesis and is evolved during             •
daylight by the phytoplankton.  This is an important mechanism for aeration          J|
during summer when warm temperatures and calm weather minimize oxygen
solubility and transfer from the atmosphere.  However, the same organisms            _
that produce oxygen during the day consume it at night.  This results in a           •
daily fluctuation in oxygen concentration, with the minimum value just               ™
before sunrise.  Therefore, in regions of the estuary where oxygen
concentrations are critical, measurements should be made at sunrise for              H
comparison with the desired level of oxygen concentration.                           W
    A third oxygen input is the oxygen combined in sulfate and nitrate.
Major groups of heterotrophic bacteria fulfill their oxygen requirements by          M
reducing sulfate to sulfide.  If gaseous oxygen is not mixed with the                •
sulfide to permit its reoxidation to sulfate, the sulfide accumulates.
Sediment interstitial water is characteristically sulfide rich as is the
Bay deep water during the summer.  Some bacteria reduce nitrate to ammonium          •
and utilize the oxygen liberated.  Although nitrate reduction preceeds               B
sulfate reduction, it is not so significant as sulfate reduction because of
the large sulfate concentration in sea water.  However, this process does            •
result in the sediments consuming nitrate from the overlying water, when             •
nitrate concentrations are moderate to high.
OXYGEN UTILIZATION
                                         143
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    Oxygen added to the water by processes just described is consumed by             •
both biological and chemical reactions.  The sites for these reactions may           f
be susupended in the water, or contained in or on the sediments.
Respiration as a means of regenerating nutrients was discussed in Section            _
3.  Now consider respiration as process by itself.                                   •
    Respiration is the biological reaction coupling oxygen to reduced                ~
substances, usually carbon, to release energy for other intracellular
processes.  Respiration removes oxygen from the water.  The amount of                B
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respiration occurring in a body of water is usually not critical to water
quality if the oxygen is replaced from the atmosphere as quickly as it  is
consumed.  However, at times,  oxygen replenishment lags utilization,  so
that undesirable conditions of low-oxygen concentration are reached.   Since
reaeration depends on climate and meterology (factors out of man's
control) , people have tried to control the addition of oxygen-consuming
organic material and stimulants (nutrients) for the formation of organic
material to natural waters.  Attaining desirable oxygen levels year-round
has been a major criterion for wastewater treatment in the United States.
    Respiration occurs both in the water and in the sediments.  In the  main
portion of Chesapeake Bay, water-column respiration in the spring removes
oxygen faster than it is replenished,  so that oxygen concentration declines
to zero by May or June.  Although oxygen depletion can be accounted for
entirely by water-column respiration,  the sediment demand is substantial.
Its importance is probably expressed more in shallow areas where the amount
of oxygen contained in the overlying water column is less, because the
amount of water is less.  In well mixed shallows, high sediment respiration
can be sustained without undesirable oxygen depletion because reaeration
keeps pace with utilization.


IMPLICATIONS


    The net result of these interacting processes is dissolved oxygen

depletion during summer in Bay waters  deeper than about 10 m.  Taft et  al.
(1980) suggest that a major proportion of organic matter driving oxygen
depletion comes from primary production of the previous year.  The
remainder could be delivered with the  spring freshet of the Susquehanna
River.  Since the oxygen decline has started as early as February when
temperatures are still low, it seems unlikely that winter/spring production
in the Bay itself contributes a significant organic load to the oxygen
d emand.
                                     144

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                                  SECTION 5

                           SUMMARY AND CONCLUSIONS
                                   145
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    Either nitrogen or phosphorus flux into phytoplankton cells can be
limiting, according to season and to position in the estuary.  The absolute
values for nutrient concentrations in the water and for phytoplankton               M
biomass, are the results of several processes tending to add or subtract            •
from the standing crop.  High concentrations of nutrients or cells do not
necessarily indicate high turnover rates.  If anything, the reverse tends
to be true.                                                                         H
    Nutrients in Chesapeake Bay participate in complex cycles,  involving            U
both biological and chemical interactions.  Nitrogen and phosphorus have
different annual cycles in the open Bay, resulting in nitrogen limiting             M
biomass in summer, and phosphorus limiting it for most of the remainder of          •
the year.  The peak in nitrogen availability occurs in spring,  because of
large nitrate inputs from the tributaries in addition to ambient recycling
in water and sediments.  The peak in phosphorus availability occurs in              •
summer and is linked with oxygen depletion in water deeper than ten                 9
meters.  Oxidized iron compounds may play a key role in removing some
phosphorus from the water, thus acting as a natural control mechanism where         •
iron is abundant.                                                                   •
    Phytoplankton, the major nutrient consumers in the system,  have
preferences for ammonium nitrogen and phosphate phosphorus.  From modeling
and from experiments in the Bay, it appears that much of the nitrate                I
entering the upper Bay in spring passes through to the lower Bay, because           ™
the phytoplankton are consuming ammonium in preference to the nitrate.
Analogs may exist in tributary estuaries.                                           •
    The high productivity of Chesapeake Bay is sustained by rapid recycling         ||
of nutrients in the water column and in the sediments.  It appears that the
total plankton biomass in the system may be limited by nitrogen or                  ซ
phosphorus at different times, but that the rate of phytoplankton growth is         •
not nutrient-limited because of rapid recycling.
    The sediments are critical in nutrient processes,  as both a source and
sink for different compounds.  Progress is being made in quantifying the            I
rates of nutrient flux into and out of the sediments,  but this  area                 |
requires additional research.
    Environmental decision-makers should grasp the important                        M
characteristics of the estuary discussed herein.  In evaluating                     •
alternatives for controlling inputs to the system, managers should consider
the amount of nutrient to be added to the system compared to what is
already there.  They should also consider its form.  For example, nitrogen          •
added in spring to the upper Bay as nitrate will probably not adversely             •
affect the upper Bay.  Phosphate added to the system at any time could
increase phytoplankton standing crop, if the controlling influence of iron          im
compounds is exceeded.                                                              •
    Since this estuary, by nature, accumulates nutrients, most  nutrients
and organic carbon added to the system will remain in it.  Thus, once
degraded, the lower Bay whole would probably take a fairly long time to             I
recover.  However, non-degradation is realistic and achievable.                     •
Nevertheless, since the estuary tends to trap nutrients, common sense
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suggests that increases in the total amount of nutrients should be kept to
a minimum.  If scientists can provide accurate information on process rates
and outputs from the system, it may be possible for managers to regulate
inputs to the level of the outputs.  The key is quantifying the outputs to
the ocean, sediments, and commercial catches, something which so far has
proven to be difficult.  Chapter 3 of this part of the CBP Synthesis
Resport discusses those outputs further.  Understanding processes may help
humans overcome the estuary's tendency to accumulate nutrients, by finding
positive ways to utilize them within the coastal system.
    Management agencies supporting research should consider studying
processes along with the traditional monitoring of nutrient
concentrations.  Both kinds of information are important in assessing the
progress of chosen management strategies.
                                      146

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Fournier, Robert 0.  1966.  Some Implications of Nutrient Enrichment on
    Different Temporal Stages of a Phytoplankton Community.  Ches. Sci. 7:
    11-19.
    Patuxent River Estuary.  Ches. Sci.  7:  59-74.
Loftus,  et  al.  1972.
     Bay.   In:   Marine  Chemistry  in  the Coastal  Environment.  T.M. Church,
     ed.   ACS  Symposium Series, No.  18, American Chemical Society,   pp.
     664-681.
                                       147
                                                                                     I
                              LITERATURE CITED                                       I

Bray, J.T., O.P. Bricker, and B.N. Troup.   1973.  Phosphate in
    Intersititial Waters of Anoxic Sediments:  0:
    Sampling Procedure.  Science. 180:1362-1364.

Boynton.  1980.
    Intersititial Waters of Anoxic  Sediments:   Oxidation Effects  During              •
Bricker, O.P., and B.N. Troup.  1975.  Sediment-Water Exchange in
    Chesapeake Bay.  In:  Estuarine Research L.E. Croin, ed, Academic                _
    Press, New York pp. 3-27.                                                        •

Carpenter, J.H., D.W. Pritchard, and R.C. Whaley.  1969.  Observation of
    Eutrophication and Nutrient Cycles in Some Coastal Plain Estuaries.              •
    Acad. Sci., Washington, DC.                                                      I

Eppley, R.W., and E.H. Ranger.  1974.  Nitrogen Assimilation of an Oceanic           _
    Diatom in Nitrogen-Limited Continuous Culture.  J. Phycology. 10: 15-23.         I
                                                                                     I
Heinle, D.R.  1966.  Production of a Calanoid Copepod,  Acrtia Tonsa, in the
                                                                                     ซ
                                                                                     •
Jaworski, N.A. , D.W. Lear, and 0. Villa.  1972.  Nutrient Management in the
    Potomac Estuary.  In:  Nutrients and Eutrophication:  The Limiting                H
    Nutrient Controversy.  G.E. Likins, ed.  Special Symposium, Volume 1.             V
    pp. 246-273.

Ketchum, B.H.   1939.  The Development and Restoration of Deficiencies in              •
    the Phosphorus and Nitrogen Composition of Unicellular Plants.  J.
    Comp. Cell  Physiol.  13:373-381.

Kuenzler, E.J.  1965.  Glucose-6-Phosphate Utilization by Marine Alga.  J.            9
    Phycology.  1: 156-164.

Kuenzler, E.J., and B.H. Ketchum 1962.  Rate of Phosphorus Uptake by                  •
    Paeodactylum Tricornutum.  Biol. Bull. 123: 134-145.
                                                                                     I
McCarthy, J.J., W.R. Taylor, and M.E. Loftus.   1974.  Significance of
    Nanoplankton  in  the Chesapeake  Bay Estuary  and Problems Associated with           •
    the  Measurement  of Nanoplankton Productivity.  Mar. Biol. 24: 7-16.               Jj

McCarthy, J.J., W.R. Taylor, and J.L. Taft.   1975.  The Dynamics of                   _
    Nitrogen and  Phosphorus Cycling in the Open Water of  the Chesapeake               •
                                                                                      I

                                                                                      I

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McCarthy, J.J., W.R. Taylor, and J.L.  Taft.   1977.   Nitrogenous Nutrition
    of the Plankton in the Chesapeake  Bay.   I.   Nutrient Availability and
    Phytoplankton Preferences.  Limnol.  Oceaogr. 22: 996-1011.


McElroy, M.B., J.W. Elkins, S.C. Wofsy,  E.E. Kolb,  A.P.  Duran,  and W.A.

    Kaplan.  1978.  Production and Release  of ^0 from the Potomac
    Estuary.  Limnol. Oceanogr. 23: 1168-1182.


Najarian, T.O., and D.R.F. Harleman.   1977.   Real Time Simulation of
    Nitrogen Cycle in an Estuary.  J.  Env.  Eng.  Div. ASCE.  103:  523-538.


Odum, E.P.  1971.  Fundamentals of Ecology.  3rd  Edition, Saunders,
    Philadelphia.  574 pp.


Pamatmat, M.M.  1968.  Ecology and Metabolism of a Benthal Community  on  an
    Intertidial Sandflat.  Int. Rev. Gesamten.   Hydrobiol. 53:  211-298.


Redfield, A.C., B.H. Ketchum, and F.A. Richards.  1963.   The Influence of
    Organisms on the Composition of Sea-Water.   In:   The Sea.   M.N. Hill,
    ed.  Vol. 2, Interscience, NY.  pp.  26-77.


Rupp, N.M.  1969.  Seasonal and Spatial Distribution of Acartia Tonsa and
    A. Clausi in Chesapeake Bay.  Master's  Essay, Johns Hopkins
    University.  45 pp.


Siebarth.  1967.


Storms, S.E.  1974.  Selective Feeding,  Ingestion and Assimilation Rates,
    and Distribution of The Copepod Arcartia in  Chesapeake Bay. Ph.D.
    Thesis.  Johns Hopkins University   162  pp.


Taft et al.  1975.


Taft, J.L., M.E. Loftus, and W.R. Taylor.   1977.  Phosphate Uptake from

    Phosphomonoesters by Phytoplankton in  the Chesapeake Bay.   Limnol.
    Oceanogr. 22: 1012-1021.


Taft, J.L., and W.R. Taylor.  1976a.   Phosphorus Distribution in the
    Chesapeake Bay.  Ches. Sci. 17: 67-73.


Taft, J.L., and W.R. Taylor.  1976b.   Phosphorus Dynamics in Some Coastal
    Plain Estuaries.  In:  Estuarine Processes.  M.  Wiley ed., Academic
    Press, NY.  pp. 79-89.


Taylor, W.R., and J.J. McCarthy.  1972.  Studies of Nutrient Requirements
    of Chesapeake Bay Phytoplankton Using Enrichment Techniques.   Progress
    Report to U.S. AEC.  Document No.  COO-3279-03.
                                      148

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                                                                                    I
Teal, J.M., and J. Kanwisher.  1961.  Gas Exchanges in a Georgia Salt               M
    Marsh.  Limnol. Oceanogr. 6:  388-399.                                           •
Tyler, M.A., and H.H. Seliger.  1978.  Annual Subsurface Transport of a Red
    Tide Dinoflagellate to its Bloom Area:  Water Circulation Patterns and          •
    Organism Distributions in the Chesapeake Bay.   Limnol.  Oceanogr.  23:
    227-246.
                                      149
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                                                   CHAPTER 3





                                           NUTRIENT AND SEDIMENT LOADS


                                       TO THE TIDAL CHESAPEAKE BAY SYSTEM
                                                       by


                                               James T.  Smullen^


                                                  Jay L.  Taft2


I                                              Joseph Macknis^
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m                J  GEOMET Technologies,  Inc., Annapolis, Maryland

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                   1 Chesapeake Bay Program, U.S. EPA,  Annapolis,  Maryland

                   2 Chesapeake Bay Institute,  the Johns Hopkins University,  Shady  Side,
                      Maryland
                   3
                                                     150

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                                   CONTENTS
                                                                         152

                                                                         153


                                                                         157
                                                                         161
                                                                         167
                                                                         185
                                                                         212
                                                                         218
                                                                         223
                                                                         232

References	249


Sections
I.
TI.
III.
IV.
V.
VI.
VIT.
VIII




Riverine-Transported Sources of Nutrients and Sediments . . .
Bottom Fluxes of Nutrients. 	


Summary and Conclusions: The Management Questions Answered .
                                   151
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                                   FIGURES


Number                                                                  Page


I.I      Box model of nutrient and sediment  input  sources  to  the

         Chesapeake Bay system 	    158


1.2      Binary dendogram showing possible responses  of  the water  column to

         increased nutrient loadings 	    159


II.1     Rainfall sampling study area locations	    163


III.l    Physiographic provinces of Chesapeake  Bay showing area drained  by

         the three fall line gauges	    168


IV.1     River systems discharging to Chesapeake Bay  with  USGS  fall

         line	    186


V.I      Conceptual diagram of estuarine sediment  column 	    213


VI. 1     Net flows at the mouth of Chesapeake Bav  in  July  1980  as

         viewed from the ocean looking into the Bav	    219


VII.1    Map of Chesapeake Bay showing regions  in  which  primary
         productivity measurements have been averaged	    224


VIII.1   Annual (a) nitrogen and (b) phosphorus budgets  for

         Chesapeake Bay	    238
                                   152

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                                     TABLES

                                                                           Page

          Seasonal and Annual Volume-Weighted Mean Nutrient Concentrations
          Observed in Bay Area Rainfall	164
                                   153
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II. 2      Bay-Wide Mean Monthly and Seasonal Precipitation,  in Inches,
          Computed from Monthly Averages at NOAA Stations .........  165          _

II. 3      Seasonal and Annual Nutrient Loads from Precipitation to the
          Tidal Chesapeake Bay System ...................  165

III.l     Annual and Seasonal Mean Daily Discharges and Drainage Areas  of                 |
          the Maior Basins Monitored:   Susquehanna, Potomac,  and .lames
          Rivers  .............................  173          _

III. 2     Regression Model Results for the Susquehanna River at                          ™
          Conowingo, MD ..........................  172

III. 3     Regression Model Results for the Potomac River at  Chain                        •
          Bridge, Washington, DC  .....................  173

III. 4     Regression Model Results for the James River,  at                               I
          Cartersville, VA  ........................  174

Ill.S(a)  Estimated Annual Mean Daily Nutrient and Sediment  Loads                        •
          to the Chesapeake Bay System from Sources Transported by                       H
          Rivers  .............................  17 fi

III.5(b)  Estimated Percentage of Annua 1 Nutrient and Sediment                           •
          Loads from Chesapeake Bay Tributaries ..............  176
•
™
III.6(a)  Estimated Winter Mean Dailv Nutrient and Sediment Loads to
          the Chesapeake Bay System from Sources Transported by
          Rivers  .............................  ^ 77

III.6(b)  Estimated Percentage of Wjj-ij-er Nutrient and Sediment                           |
          Loads from Chesapeake Bay Tributaries ..............  177

III.7(a)  Estimated Spring Mean Daily Nutrient and Sediment Loads to                    I
          the Chesapeake Bay System from Sources Transported by                         ™
          Rivers  .............................  173

III.7(b)  Estimated Percentage of Spring Nutrient arid Sediment                           |
          Loads from Chesapeake Bay Tributaries ... ........  ...  1 7o

III.8(a)  Estimated Summe r Mean Daily Nutrient and Sediment Loads to                    •
          the Chesapeake Bay System from Sources Transported by
          Rivers  .............................   179
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III.8(b)  Estimated Percentage of Summer Nutrient  and  Sediment

          Loads from Chesapeake Bay Tributaries  .............. 179


III.9(a)  Estimated Fall Mean Daily Nutrient and Sediment  Loads  to  the

          Chesapeake Bay System from Sources Transported by  Rivers   .  .  .  . 13f-


III.9(b)  Estimated Percentage of Fall Nutrient and Sediment

          Loads from Chesapeake Bay Tributaries   .............  "! ^
III. 10    Seasonal and Annual Nutrient and Sediment  Loads  Transported

          by Rivers to the Tidal Chesapeake Bay System  .......... 133


IV. 1      Water Quality Variables and Variable Code  ............ -1 8?


IV. 2      USGS hydrologic Units Below the Functionally Defined Fall Line of

          the Chesapeake Bay Drainage Basin ................ 1" '


IV. 3      Range of POTW Constituent Concentrations Based on Level  of
          Treatment .................... .  ....... 191


IV. 4      Estimate of Distribution of POTW Nitrogen  and Phosphorus into

          Various Fractions According to Selected Treatment Process  .... 19f


IV. 5      Estimates of Nutrient Loads from Municipal Point Sources  .... 151


IV. 6      Estimates of Nutrient Loads from Municipal Point Sources  .... 192


IV. 7      SIC code and Economic Activity  ................. 195


IV.8(a)   SIC Code and Assigned Concentration  of Water Quality Constituents 196


IV.8(b)   SIC Code and Source of Constituent Concentration  ........ 197


IV. 9      SIC Code, Assigned Flow, and Source  of Value  .......... 109


IV. 10     Assigned Industrial Facilities,  Nutrient Loadings from Observed
          Data
                                                                            200
IV.ll(a)  Estimates of Nutrient Loads from Industrial  Point  Sources  from
          Above the Functionally Defined Fall Line	201


IV.ll(b)  Estimates of Nutrient Loads from Industrial  Point  Sources
          from Below the Functionally Defined Fall  Line	202


IV.ll(c)  Estimates of Nutrient Loads from Industrial  Point  Sources
          from Above and Below the Functionally  Defined  Fall Line  	  ^^3


IV.12(a)  Estimates of Nutrient Loads from Municipal and Industrial
          Point Sources from Above the Functionally Defined  Fall Line  .  .  ,  20^
                                   154

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Number

IV.12(b)

IV.12(c)



IV. 13



V.I


V.2


V.3
V.4

VI. 1
VI. 2

VII. 1


VII. 2


VII. 3

VII. 4

VII. 5

VII. 6


VII. 7


VIII. l(a)


VIII. Kb)





Page

Estimates of Nutrient Loads from Municipal and Industrial
Point Sources from Below the Functionally Defined Fall Line . . . 207
Estimates of Nutrient Loads from Municipal and Industrial
Point Sources Totaled Above and Below the Functionally


Total Estimated Average Seasonal and Annual Nutrient Loadings
from Point Sources to the Tidal Portions of the Chesapeake Bay
System 	 211

Potential Nitrogen and Phosphorus Unit Area Diffusion from


Potential Nitrogen and Phosphorus Mass Diffusion from Sediment


Nutrient Release from the Sediments Measured Under Domes .... 217
Nutrient Release in Each Segment Calculated from Dome Studies . . 217

Nutrient Fluxes Across the Mouth of Chesapeake Bay in July 1980 . 221
Fluxes of ^articulate Material at the Bay Moiith Calculated with a
Box Model 	 221
Primary Productivity Measurements and Factors Used to Calculate


Relation Between Annual Plankton Productivity and Annual Nutrient




Relation Between Winter Phy toplankton Productivity and Nutrient
Inouts 	 228
Relation Between Spring Phytoplankton Productivity and Nutrient
inputs 	 229
Relation Between Summer Phytoplankton Productivity and Nutrient


Relation Between Fall Phytoplankton Productivity and Nutrient
Inputs 	 231

Average Annual Nutrient and Fluvial Sediment Input to the Water


Percentages of Annual Nutrient Loadings from Various Sources . . 233


155

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Table                                                                      P_a_g_e


VIII.2(a) Average Winter Nutrient and Fluvial Sediment Input to the Water
          Column of the Tidal Chesapeake Bay System 	  233


VIII.2(b) Percentages of Winter Nutrient Loadings from Various Sources  .  .  233


VIII.3(a) Average Spring Nutrient and Fluvial Sediment Input to the Water
          Column of the Tidal Chesapeake Bay System	23 i


VIII. 3(b) Percentages of Spring Nutrient Loadings from Various Sources  .  .  23'i


VIII.4(a) Average Summer Nutrient and Fluvial Sediment Input to the
          Water Column of the Tidal Chesapeake Bay System	234


VIII.4(b) Percentages of Summer Nutrient Loadings from Various Sources  .  .  235


VIII.5(a) Average Fall Nutrient and Fluvial Sediment Input to the Water

          Column of the Tidal Chesapeake Bay System 	  235


VIII.5(b) Percentages of Fall Nutrient Loadings from Various Sources  . .  .  235


VIII.6    Seasonal Distribution of Nutrient Loadings	236


VIII.7    Concentration and Loading Rates for Total Suspended Solids,  Total
          Phosphorus, Orthophosphate, Total Nitrogen,  and Nitrite-Nitrate from
          Various uses of Land	242


VIII.8    Generalized Ranking of Land Uses	24?


VIII.9    Ranking of Urban Land Uses	243


A-l Water Quality Variables Included in Regression Analysis 	  254


A-2 Regression Models Chosen for the Susquehanna River at
          Conowingo, MD	256


A-3 Regression Models Chosen for the Potomac River at  Chain
          Bridge, Washington, DC  	  258


A-4 Regression Models Chosen for the James River at
          Cartersville, VA	260
                                   156

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                                   SECTION 1

                                  INTRODUCTION
    losses.
                                 157
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    An important area of concentration of the Management  Questions  within the         , •
CBP Nutrients Program is the excessive fertilization (over-enrichment)  of the          I
Bay system.  Nutrient over-enrichment can cause excessive algal  blooms  and
oxygen depletion.  Although this fertilization process, called eutrophication,         _
occurs naturally (i.e.,  runoff from the land and atmospheric  deposition               I
processes have always carried plant nutrients to receiving waters),  the               ™
cultural activities of man accelerate it.  When coupled with  the complicating
problem of increased sedimentation rates due to cultural  activities,  the               •
result can be the shortening of the life of the estuary and a decrease  in the          |
value of the system and its resources.  This two-pronged  problem of nutrient
over-enrichment and increased sediment yield has come to  be known as  "cultural         _
eutrophication."  The aquatic plant nutrients considered  in this paper  are the         •
various forms (species)  of nitrogen and phosphorous.                                   ™
    To understand and manage potential cultural eutrophication problems in the
Bay system, we need to answer a number of questions concerning sources  of             H
nitrogen, phosphorus, and sediment to the Bay and its tidal                           |
tributaries.  This paper seeks to synthesize available research  findings  on
these sources by answering the following Management Questions:                         •

1.  What is the atmospheric contribution to nutrient  input?
2.  What percentage of the nutrients is from point  sources?
3.  What percentage of the nutrients is from nonpoint sources?   How do  they           I
    vary over time?                                                                   |
4.  What are the pollutant runoff rates for particular land uses?
5   What percentage of nonpoint sources can be attributed to  particular land           n
    uses?                                                                             •
6.  What are the nutrient loadings from the Fall Line?
7.  What do the bottom sediments contribute to nutrient inputs?
8.  What are the flux rates of nutrients from the bottom  sediments,  and how do         •
    they vary seasonally?                                                             •
9.  Given the estimated loadings of nutrients for each of the sources,  which
    will be the most important in terms of their effects  on the  Bay system.            •

    To answer the management questions, we synthesized available information
to understand the components of a nutrient budget.   In this paper,  the                 _
approach taken for determining the nutrient budget  centers on a  simplified            •
consideration of the Bay as a container, or box, into which flow
nutrient-laden waters from various sources (see Figure I.I).  This  box  model
approach allows the reader to visualize nutrient sources  simultaneously as a           B
simple schematic diagram or picture.  We considered five  external sources             I
expressed both as annual and seasonal loadings.  These sources are  shown  in
Figure 1.2 and include:                                                                •
    - Atmospheric Sources, defined for the purposes of this paper as  nitrogen          I
    and phosphorus falling onto tidal Chesapeake Bay system waters  in
    precipitation and nitrogen lost to the atmosphere as  nitrous oxide  and
    gained through nitrogen fixation.  No estimate  is made of denitrification          •
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    - Riverine-Transported Sources,  defined  as  nitrogen,  phosphorous,  and
    sediment,  which derive from above  the  head  of  tide  or the  Fall  Linel.
    This source includes  loadings  from surface  land  runoff,  atmospheric
    loadings falling upon upland waters, groundwater contributing as baseflow,
    municipal  sewage treatment  plant discharges from above the Fall Line and
    industrial waste discharges from above the  Fall  Line  as measured at  the
    Fall Line  water quality monitoring stations.   No estimate  is made  of land
    runoff or  groundwater loadings deriving  from below  the Fall Line.
    - Point Sources to Tidal Waters, defined as nutrient  loadings from
    publicly owned sewage treatment  works  discharges and  industrial waste
    discharges that enter the tidal  waters of the  Bay system directly.   For
    the purposes of this  paper  (see  definition  of  "functional" fall line in
    Section IV) all such  discharges  are defined to be those that enter
    downstream of the head of tide of  the  Susquehanna,  Potomac and  James
    rivers;
    - Bottom Sources, defined as fluxes of nitrogen  and phosphorous between
    the bottom sediments  of the Bay  and the  water  column.  Because  of  the  lack
    of  wide spread tributary benthic  flux data, fluxes are computed only  for
    the Bay proper;
    - Ocean Sources, defined as the  net flux of nutrients between the  Bay  and
    the Atlantic Ocean.
    In addition to these  five sources, the internal  or  re-cycled nutrients as
a source will  also be discussed.  The  only sediment  source considered  is
riverine, included as described above  under  Riverine Transported Sources.  No
estimates were made of potential sediment  loads entering  the system from the
ocean or shore erosion, nor of the contribution because of phytoplankton
production of  skeletal material.  The  net  sedimentation of nutrients was
determined by difference.  A schematic diagram  of  the box model is  shown in
Figure I.I, and the nutrient budgets appear  in  Section  VIII.  Nonpoint source
nutrient contributions below the fall  line have not  been  included in this
paper because  the data were not available  at the time of  writing.   Estimates
from below the fall line  are being currently made  through a computerized model
and will be available in  the near  future.   The  eventual inclusion of these
data in the nutrient budget will tend  to reduce the  percentages of  nutrient
loads shown here.
    In summary, the authors of  this  paper  have  assembled  available  information
concerning the most important nutrient sources  and attempted to answer the
pertinent management questions.  Each  of the sources is discussed in separate
sections, with a comparison of  these sources made  in Section VIII.
Conclusions and answers to the  management  questions  are also found  in  the  last
section.
        (1968)  describes a broad area  trending  from Southeast  to
 Northeast which defines the  head of tide  (and  the  head  of  navigation)
 as the contact between the hard crystalline  basement  rocks and the
 unconsolidated sediments of  the Coastal Plain.   This  demarcation he  calls
 the Fall Line  or Fall Zone.
                                  160

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                                 SECTION II

                      ATMOSPHERIC SOURCES OF NUTRIENTS
NUTRIENT CONCENTRATIONS IN PRECIPITATION
 1981.
                                  161
                                                                                     I
                                                                                     I
    Precipitation and dust/dirt dryfall are the major mechanisms  that                 •
return to the earth's surface gaseous and particulate materials  that are              |
injected into the atmosphere from natural and man-induced  sources.  To
determine the relative importance of the atmospheric  source  to the  overall            ป
nutrient input budget, we estimated the mass of nitrogen and phosphorous              I
carried into the Bay by rainfall.  No estimate of  the dryfall portion of              ™
the atmospheric source has been made because of the paucity  of available
data and the uncertainty of existing dryfall sampling techniques^.
    Although about 10 percent of annual areal precipitation  is made up  of
forms other than rainfall (i.e., snow or ice), data on concentrations of
nutrients in these forms are lacking.  Therefore,  for the  purpose of this
paper, the concentrations computed for rainfall will  be assigned  to the
total precipitation budget.
                                                                                     I
                                                                                     I
    Rainfall quality data were chosen from studies conducted within the
Chesapeake Bay drainage basin.  We chose this method to ensure that the              ป
data reflect the natural and man-induced surface sources peculiar to the             M
region.  The size of the available data base made the regional restriction
feasible.  The data included interim reports, draft final reports,
completion reports or personal communications of six major regional                  H
nonpoint pollution and rainfall quality studies (Northern Virginia Planning          I
District Commission [NVPDC]  and Virginia Polytechnic Institute and State
University [VPI&SU] 1977, Bostater2 1981, Wade & Wong 1981, Correll et               •
al. 1978, Ward and Eckhardt 1979, Lietman3 1981, VPI & SU 1981,  Weand4               |
1981).  The general locations of these study areas are shown in Figure II. 1.
    The assembled data base consists of bulk precipitation samples from as           _
many as 125 storm events collected at up to 18 sampling locations for all            •
seasons from 1976 through 1981.  In most cases, a raingage within,  or near           *
the sample collection areas, recorded precipitation volumes.  For most
storm events, composited samples were analyzed for ammonia nitrogen,                 H
nitrite + nitrate nitrogen,  total Kjeldahl nitrogen, orthophosphorus and             |
*-The authors note that although some dryfall deposition data collected               •
 within Chesapeake Bay sub-basins are available  (Correll et al.  1978,               •
 Virginia Polytechnic Institute & State University 1978), too little was
 available to make reliable Bay-wide estimates.
^Personal Communication:  "Patuxent River Park Rainfall Quality Data," C.            •
 Bostater, Department of Natural Resources, State of Maryland, 1981.
•^Personal Communication:  "Pequea Creek Watershed Rainfall Quality Data,"            _
 P. Lietman, Harrisburg Sub-district, U.S. Geological Survey, Harrisburg,            •
 PA, October, 1981.                                                                  •
^Personal Communication:  "Occoquan Watershed Rainfall Quality Data," B.
 Weand, Occoquan Watershed Monitoring Laboratory, Manassas, VA, November,            •
                                                                                     I

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total phosphorus were assembled (total  nitrogen was  computed  as  the  sum  of
total Kjeldahl nitrogen plus nitrite +  nitrate nitrogen).   Concentrations
were recorded as milligrams per liter (mg/L)  or converted  to  mg/L from data
expressed as molar concentration.   All  concentrations  are  expressed  as
elemental nitrogen (N) or phosphorous (P).
     Many investigators have shown that constituent  concentrations in
rainfall are strongly related to precipitation amounts (Stensland 1980).
For example, given similar antecedent rainfall conditions,  a  smaller
rainfall event would probably have higher nutrient concentrations than a
larger rainfall event occurring in the  same geographical area.   This is  due
primarily to the tendency for rainfall  pollutant loadings  to  exhibit
"first-washout" or "first-flush" effects (NVPDC and  VPI &  SU  1978; Gambell
and Fisher;  Uttormark, Chapin,  and Green 1974).  The first-flush effect  is
characterized by concentrations of rainfall constituents reaching a  maximum
value early in a storm event and declining  rapidly thereafter.   To
compensate for this effect it is common to  report rainfall  constituents  as
volume-weighted average concentrations'- rather than  as arithmetic average
concentrations (Stensland 1980).  For this  reason, all concentrations
reported in this chapter have been computed as volume-weighted averages.
     For this analysis, we used the volume  weighted  mean of the  nutrient
concentrations for data collected  in each geographic area  (shown in  Figure
II.1), for each season.  An equal-weight average of  the means of data
collected at each of the geographic locations by season was computed.  We
took this approach to reduce the potential  for those studies  with the most
data to skew the means in favor of one  particular geographic  area.   The
results of these computations are  reported  in Table  II.1.
     Lang and Grason (1980) reported mean monthly precipitation  totals
(based upon NOAA records, 1941-1970) at three sites  within  the Chesapeake
Bay Basin, including Richmond,  VA, College  Park,  MD,  and Harrisburg,  PA.
An average of the mean monthly totals over  the three stations was computed
to represent a Bay-wide average mean monthly  precipitation  and is reported
in Table II.2.  Also shown in this Table are  the computed  seasonal totals
and the annual average of 39.6  inches of precipitation.  It can  be seen
from the data in Table II.2 that,  on the average, the  Bay  receives 21.6,
25.3, 24.8,  and 23.3 percent of its annual  precipitation in winter,  spring,
summer and fall respectively.  These percentages were  used  as the weighting
factors to compute volume-weighted annual nutrient concentrations (from  the
seasonal concentrations), shown on the  last row of Table II.1.
1
                   ci = concentration
                      = volume
                               162

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                                                       PEQUEA CREEK
                             APPALACHIAN PLATEAU
                     /APPALACHIAN
                           ) VALLEY.
OCCOQUAN
RESERVOIR
                                                              RHODE
                                                              RIVER
                                                            KILMARNOCK

                                                            MAPLE VIEW
                                                            (Near  Exmore)

                                                            GLOUCESTER PT.
                                                            NORFOLK
Figure II.1.  Locations of rainfall sampling.
                                  163
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TABLE II. 1.  SEASONAL AND ANNUAL VOLUME-WEIGHTED MEAN NUTRIENT
             CONCENTRATIONS OBSERVED IN BAY AREA RAINFALL  (REPORTED AS
             mg/L OF ELEMENTAL MATERIAL)

NH3-N N02+N03-N

WINTER

A
SPRING


(1)
X
SD
,B
X
SD
A,B
SUMMER

A,
FALL

A,
X
SD
B
X
SD
B
mg/L
0.376
0.169
4, 39
0.537
0.204
3, 98
0.250
0.141
3, 22
0.256
0.232
3, 22
mg/L
0.540
0.271
6, 50
0.731
0.304
5, 125
0.621
0.525
5, 40
0.360
0.193
4, 33
TKN
mg/L
0.586
0.545
5, 33
1.783
0.852
4, 96
0.988
0.426
4, 35
0.642
0.662
4, 33
TN Ortho P Total P
(N02+N03+TKN)
mg/L
1.126
	
___
2.514
	
^
1.609
	
•~ • -*~*
1.002
	
™
mg/L
0.016
0.013
4, 37
0.015
0.009
3, 91
0.014
0.015
5, 21
0.021
0.013
3, 16
mg/L
0.038
0.030
6, 51
0.080
0.092
5, 122
0.079
0.098
5, 41
0.050
0.036
4, 31
ANNUAL
0.351
0.571
1.022
1.593
0.016
0.064
1 Legend - X = Equal Weight Mean (mg/L)
           SD = Standard Deviation
            A = # studies from which data were taken for computation
            B - # station storms sampled (n)


Nutrient Loads in Precipitation


    Seasonal and annual nutrient loadings were estimated based on
precipitation falling upon the water areas of Chesapeake Bay and its tidal
tributaries.  Nutrient loadings, from precipitation falling upon the water
and land surfaces of the Bay watershed above the head of tide of the
Susquehanna, Potomac, and James Rivers, are accounted for in the fluvial
loadings computed in Chapter III of this paper.  The mean annual and
seasonal precipitation values shown in Table II.2 were used to compute
expected annual and seasonal volumes of precipitation input to the  4412.1
square mile Chesapeake Bay tidal system.  These volumes were applied to  the
concentrations in Table II.1 to produce the seasonal and annual nutrient
loading estimates that are shown in Table II.3.
                                   164

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TABLE II.2.  BAY-WIDE MEAN MONTHLY AND SEASONAL PRECIPITATION,  IN INCHES,
             COMPUTED FROM MONTHLY AVERAGES OF NOAA STATIONS^-

Month
December
January
February
March
April
May
June
July
August
September
October
November

Mean Mean
Monthly Seasonal
Total (in.) Season Total (in.)
3.18
2.72
2.65
3.14
2.95
3.69
3.79
3.61
4.42
3.21
2.79
3.21

ป_-__
	
Winter 8.55
	
	
Spring 10.04
	
	
Summer 11.82
	
	
Fall 9.21
Average Annual Total = 39.62 in.
Seasonal %
of Annual
Total


21.6


25.3


29.8


23.3


^•Monthly totals shown are the average ot the mean monthly totals at each of
 three NOAA stations (Richmond, VA, College Park, MD, Harrisburg, PA) based on
 precipitation records 1941-1970 as reported by Lang and Grason, 1980.


TABLE II.3.  SEASONAL AND ANNUAL NUTRIENT LOADS FROM PRECIPITATION TO THE

             TIDAL CHESAPEAKE BAY SYSTEM (MILLIONS OF POUNDS)

Precipi-
tation
Volume

Winter
Spring
Summer
Fall
Annual
(inches)
8.55
10.04
11.82
9.21
39.62
Ammonia-
N

2.06
3.45
1.89
1.51
8.91
Nitrite +
Nitrate-N

2.95
4.70
4.70
2.12
14.47
Total
Total Nitrogen-N
Kjeldahl
N
3.21
11.46
7.47
3.78
25.92

6.16
16.15
12.17
5.91
40.39
Total
Ortho- Phosphorus
Phosphorus P
P
0.088
0.096
0.106
0.124
0.399

0.208
0.514
0.598
0.295
1.64

     The compilations  in  tl.e Tables  indicate thai lioth concentrations and
 areal  loading  rates  in  rainfall are  significant  in comparison to other sources

 (Section VIII).  Nitrogen and  phosphorus concentrations shown are similar  to
 those  found  in other studies conducted  in  the northeastern United States
                                   165
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(Ward and Eckhart 1977,  Stensland 1980).   The seasonal and annual rainfall
concentrations of total  nitrogen exceeded the volume-weighted mean
concentrations observed  in runoff from forested sites studied under the
Chesapeake Bay Programs's Intensive Watershed Studies Project^.   (See Table
VIII.6 for these concentrations.)  Orthophosphorus concentrations in
precipitation are of the same order of magnitude,  but generally  less than
those observed in forested land runoff.  Concentrations of most  constituents
are typically much less  than those in runoff from  other land uses.
     Comparisons between atmospheric and  other sources are made  in Section
VIII.  For example,  it can be seen in Tables VIII.3(b) and VIII.4(b) that
precipitation is a major contributor of TKN in spring and summer.  This could
be particularly important in summer, when nitrogen limits phytoplankton
biomass in much of the Bay (Chapter 2 of  this part).


OTHER ATMOSPHERIC NUTRIENT INTERACTIONS


     Other nutrient processes involving gains of nitrogen from the atmosphere
and losses of nitrogen to the atmosphere  were considered.  The nitrogen input
to the Bay by nitrogen fixation is not well known, but it should be small
compared to other inputs since nitrogen fixation rates in the water are
vanishingly small.  We estimate 25,000 pounds per  year net input from
marshes.  The nitrogen loss to the atmosphere as ^0  and NH3 gas is also
probably small.  Few measurements have been made from which we estimate an
annual loss of 40,000 pounds per year from the estuary.  We hope, future
research will refine these estimates.  Losses due  to  denitrification were not
estimated, but were considered to be small relative to the sources (i.e.,
precipitation, riverine, etc.).
^Personal Communication:   "Volume-Weighted Mean Concentrations  of  Storm
 Event Runoff from EPA/CBP Test Watersheds," John P.  Hartigan,  Northern
 Virginia Planning District Commission,  Falls Church,  VA,  October  13  1981,
                                 166

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                                  SECTION III

             RIVERINE-TRANSPORTED SOURCES OF NUTRIENTS AND SEDIMENT
I
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     A major objective of the EPA Chesapeake Bay Program was  to assess the               M
loadings of nutrients, sediment and other water quality constituents  from the
watersheds of the Bay to the tidal system.  The approach taken included
developing an intensive data base of the nutrient and sediment loadings                  •
entering the Bay from fluvial sources over a period of several years,  and then           ™
developing a methodology to extrapolate that data to produce  reliable
estimates of the expected long-term loadings from the upstream sources.  In              •
this chapter, we estimate seasonal and annual total mass flux of nutrients to            j|
the tidal waters of the Bay system from above the head of tide, or the fall
line.  The section is subdivided into three sub-sections.  The first  describes           _
a fairly rigorous development of loadings from the three major tributaries               I
(Susquehanna, Potomac, and James Rivers) based on data collected as part of              W
the EPA Chesapeake Bay Program.  The second section contains  estimates of
minor tributary (Patuxent, Rappahannock, Mattaponi, Pamunkey, and Chickahominy           •
Rivers) loadings based, in part, upon a field study performed by Guide and               ^
Villa in 1969 through 1970.  In the third section, the total  annual and
seasonal fluvial-loading estimates are presented.                                        ^

NUTRItiNT INPUTS FROM THE MAJOR TRIBUTARIES                                               "

     To determine the nucrient contributions from the major watersheds of the            •
Chesapeake Bay drainage area, the Bay Program established a fall line                    •
monitoring project.  This project, performed by the U.S. Geological Survey,
monitored water quality of three major tributaries of the Bay.  The sites                ซ•
monitored were:  Susquehanna River at Conowingo, MD; Potomac  River at Chain              •
Bridge, Washington, DC; James River at Cartersville, VA.  Together, the three
rivers drain about 70 percent of the approximately 64,000 square mile
Chesapeake Bay drainage basin and account for about 80-85 percent of the long-           I
term average discharge Bay-wide (Wolman 1968) (see Figure III.l).  Previous              •
work by Guide and Villa (1972) indicated that these three tributaries were the
primary riverine sources of nutrient loads to the tidal Chesapeake Bay                   ffc
system.  They found that these tributaries contributed as much as 94 percent             j^
of the total phosphorus load and 95 percent of the total nitrogen load
emanating from the eight major Bay tributaries.^                                         _
     The USGS began the sampling program  in January of 1979 and continued                •
through April of 1981, a period of 28 months.^  Base flow water quality was              ^
monitored every two weeks at the Conowingo station on the Susquehanna, and
once a month on the Potomac and James.  Samples were also taken at high  flows            •
on all stations to better understand the mechanisms affecting water quality              ||
during these critical periods of high-mass transport.  Samples were analyzed
for major ions, suspended sediment, selected nutrient species, and trace                 ^
metals.                                                                                  •


•"•These are Susquehanna, Patuxent, Potomac, Rappahannock, Pamunkey,                       •
 Mattaponi,  James, and Chickahominy Rivers.
                                   167
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Figure
Physiographic provinces of Chesapeake Bay basin
Shaded areas drain into the fall line areas in the
Susquehanna, Potomac, and James Rivers.
                                  168

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                                                                                     I
     An interim basic data report by Lang and Grason (1980) describes the
first year of this project, and a draft final report (Lang 1982)  will soon be        V
completed.                                                                           |

Description of the Major Tributary Drainage Areas                                    ^

     Susquehanna:  The Susquehanna River Basin has a drainage area of about
27,510 square miles of which 27,100 are above the fall line monitoring
station.  The basin is about 250 miles long and about 170 miles wide.  The           I
drainage lies within four physiographic provinces:  the Appalachian,  the Ridge       V
and Valley, the Piedmont, and the Blue Ridge.              .    The land-use is
predominately forest and agriculture with no major urban areas.                      ซ
     Potomac:  The Potomac River Basin has a drainage area of about 14,670           I
square miles of which 11,560 lie above the monitoring station.  The basin is
made up of eight major sub-basins with the main stem approximately 280 miles
in length.  The drainage lies within five physiographic provinces:  the              •
Applachian, the Ridge and Valley, the Piedmont, the Blue Ridge, and the Coastal       •
Plain (Figure III.2).  The Coastal Plain portion of the basin does not lie
within the monitored area.  The land use is predominately agriculture and            A
forest with the Washington, DC area draining below the monitoring gage site.         •
     James:  The James River Basin has a drainage area of about 10,000 square
miles of which 6,257 drain to the sampling station.  The basin is about 400
miles in length and drains four physiographic provinces:  the Ridge,  and             •
Valley, the Piedmont, the Blue Ridge, and the Coastal Plain (Figure III.2).          •
None of the Coastal Plain portion of the watershed lies within the monitored
drainage.  The basin is mostly agricultural and forested with the Richmond           •
metropolitan area draining below the monitoring point.                               •
     The mean annual and seasonal discharges for each basin are presented in
Table III.l.  These data were computed based upon records retrieved from the         _
USGS stream discharge stored on the EPA STORET system.  Water year 1981 data         •
were retrieved as provisional data, subject to revisions.                            ™
                                                                                     1

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                                                                                     I

                                                                                     I
 ^•Although  the monitoring period reported by Lang (1982) covers only 28                •
 months, other collection efforts at the three sites resulted in data                 *
 being available for this analysis, beginning in October 1978 and running
 through as late as November of 1981.  Some of these data were collected as
 part of the ongoing EPA/USGS National Stream-Quality Accounting Network
 (NASQUAN).
I
                                  169
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TABLE III.l. ANNUAL AND SEASONAL^-) MEAN DAILY DISCHARGES AND DRAINAGE
              AREAS OF THE MAJOR BASINS MONITORED:  SUSQUEHANNA, POTOMAC,
              AND JAMES RIVERS
BASIN
 DRAINAGE AREA
(Square miles)
 MEAN DAILY DISCHARGED)       PERIOD OF

(Cubic Feet Per Second-Per Day)   RECORD
         (CFSD)             Beginning year-
                            Ending year
                            (Number of
                            years/number of
                            days)
Susquehanna River
@Conowingo, MD 27,100
(01578310)



Potomac River 11,560
near Washington, DC
(01646500)



James River
@Cartersville, VA 6,257
(02035000)




Annua 1
Winter
Spring
Summer
Fall

Annual
Winter
Spring
Summer
Fall

Annual
Winter
Spring
Summer
Fall

43,286.8
50,109.6
68,011.5
25,193.3
29,317.5

10,953.9
13,286.9
18,466.8
6,147.2
5,883.3

6,879.1
8,811.7
10,209.3
4,248.2
4,271.7
Oct. 1967-Sept.l981
(14 yrs/5072 days)
(1,264 days)
(1,288 days)
(1,277 days)
(1,243 days)
March 1930-Sept . 1981
(51 yrs./18,842 days)
(4,603 days)
(4,784 days)
(4,784 days)
(4,671 days)
Oct. 1924-Sept. 1981
(57 yrs./20,505 days)
(5,060 days)
(5,156 days)
(5,155 days)
(5,134 days)

(1)  Winter - December, January, February
     Spring = March,  April,  May
     Summer = June, July, August
     Fall   = September, October, November
  Statistical comparisons between the Conowingo Station data and Harrisburg
  Station data indicate that the 1967 through 1981 periods are
  representative of the long term stream flow characteristics.


(2)  Discharges shown were computed from records retrieved through the
  USEPA-STORET data bank as transferred from the USGS-WATSTORE system.
  Water Year 1981 records used are provisional and subject to revision.   No
  adjustments (i.e.,  for diversions) have been made to the discharges.
  Computations were made using the Statistical Analysis System Procedure
  MEANS (SAS Institute 1979).
                                   170

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                                                                                  I
Computation of Riverine-Transported Nutrient and Sediment Loads

    To predict the statistically significant, expected value of the daily         IB
nutrient loading from each of the major tributaries,  we extrapolated the          ||
nutrient data collected during the fall line monitoring project through a
series of linear and log-linear regression models.  These models relate           ^
nutrient concentration, or nutrient loading rate,  with mean daily discharge       •
for each of the monitored tributaries.  In all cases, models were developed       ^
using bivariate least squares regression techniques.
    The independent, or predictor variable (X, in equation III-2) ,  is the         •
mean daily discharge of the flow-monitoring station adjacent to the water         9
quality monitoring site.  We eliminated from consideration other potential
independent variables such as instantaneous flow,  specific conductance, or        •
sediment concentration (Lang and Grason 1980, Lang 1982) in either                •
univariate or multivariate models, because there is no available long-term
record of occurrences of these water qualilty constituents.
    The models tested in this analysis were either linear, or linearized          •
through transformations of the variables.  This infers a direct                   •
relationship between the frequency-duration distribution of the independent
variable (mean daily discharge) and that of the response variable (e.g.,          •
daily nutrient loads) .  It is implied that the response variable has the          |
identical (but perhaps transformed) frequency-duration distribution of the
predictor variable.  Only a parameter with a long-term period of record            _
sufficient to develop a reliable frequency-duration relationship should be         •
utilized as a predictor variable.  This limitation restricted the model            ™
formulation process to use of mean daily discharge (Q) as the independent
variable in all models.                                                            •
    The period of record and the number of years of daily discharge data           |
available at each site are shown in Table III.l.  For further detail on the
model development methodology, see Appendix A.  This appendix contains the         ^
equations used to normalize storm events.  Development of concentration and        •
loading rate models using regression analysis is also explained.                  *
Regression Analysis Results
                                                                                   W
    As mentioned above, the development of the regression equation and the
model selection methodology can be found in Appendix A.  The models chosen,         •
along with the appropriate regression statistics, are shown in Table III. 2,         f
II 1. 3, and II 1. 4 for the Susquehanna, Potomac, and James stations
respectively.  For example, the variance-stabilizing transformations were          _
selected for the Susquehanna River for the variables TN, DN, N023, TKN, and        •
DP (Table III. 2).  These models either had r2 values below 0.65 for NH34,          *
TP,OP, and SED (Table III. 3), or the examination of scatter plots did not
support the use of a variance stabilizing transformation and, therefore,           B
loading rate models were selected for these variables.                             V
                                  171
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TABLE III.2.
REGRESSION MODELS CHOSEN FOR THE SUSQUEHANNA RIVER AT
CONOWINGO, MD (1578310)

Water Regressed
Model Quality Intercept
Chosen Constituent (BQ)

ln(C/Q) vs ln(l/Q
ln(C/Q) vs ln(l/Q
ln(C/Q) vs ln(l/Q
ln(LR) vs ln(Q)
ln(C/Q) vs ln(l/Q
ln(LR) vs ln(Q)
ln(C/Q) vs ln(l/Q
ln(LR) vs ln(Q)
ln(LR) vs ln(Q)

) TN
) DN
) N023
NH34
) TKN
TP
) DP
OP
SED

-0.318
0.0762
-0.600
-2.48
-1.732
-5.74
-4.42
-3.40
-1.19
Regressed
Slope
(BI)

0.937
0.982
0.948
1.15
0.921
1.42
0.972
1.11
1.56
Pr (1) Coefficient Degrees of
value of Freedom
t Determination
(slope) l
0.0001
0.0001
0.0001
0.0001(2)
0.0001
0.000l(2)
0.0001
0.000l(2)
0.000l(2)
(r2)
0.92
0.93
0.87
0.71
0.81
0.89
0.78
0.73
0.66

86
66
86
86
87
87
85
66
93

   Students "t" test for Ho: slope = 0.   The probability value shown
   answers the question "If the parameter is really equal to zero,  what is
   the probability of getting a larger value of it?"  A very small  value for
   this probability indicates that the slope is not likely to equal zero
   and, therefore, that flow (or the indicated transformed flow)  contributes
   significantly to the model (SAS 1979,  Procedure:  General Linear Models).
   jซJ:  The relationship implied by this model may be biased and,
        therefore,  may limit the usefulness of the student's "t" test (see
        text).
                                  172

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TABLE III.3.
REGRESSION MODELS CHOSEN FOR THE POTOMAC RIVER AT CHAIN BRIDGE,
WASHINGTON, DC (1646580)

Water Regressed
Model Quality Intercept
Chosen Constituent (B0)
Regressed
Slope
(Bi)
Pr (1) Coefficient Degrees of
value of Freedom
t Determination
(slooe) (r2>
ln(C/Q)vs.ln(l/Q)
ln(C/Q)vs.ln(l/Q)
ln(C/Q)vsln(l/Q)
ln(LR)vs.ln(Q)
ln(C/Q)vs.ln(l/Q)
ln(LR)vs.ln(Q)
ln(C/Q)vs.ln(l/Q)
ln(LR)vs.ln(Q)
ln(LR)vs.ln(Q)
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
-0.942
-1.49
-1.22
-3.53
-2.53
-3.87
-4.67
-2.58
-4.76
0.857
0.827
0.881
1.23
0.807
1.33
0.885
1.08
2.06
0.0001
0.0001
0.0001
0.000l(2)
0.0001
0.000l(2)
0.0001
0.000l(2)
0.000l(2)
0.86
0.84
0.80
0.71
0.72
0.85
0.72
0.70
0.88
64
63
64
61
80
79
77
47
60

(^Students "t" test for Ho: slope = 0.  The probability value shown
   answers the question "If the parameter is really equal to zero, what is
   the probability of getting a larger value of it?"  A very small value
   for this probability indicates that the slope is not likely to equal
   zero and, therefore, that flow (or the indicated transformed flow)
   contributes significantly to the model (SAS 1979, Procedure:  General
   Linear Models).

   j?^:  Tne relationship implied by this model may be biased and,
        therefore, may limit the usefulness of the student's "t" test (see
        text) .
                                  173


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TABLE III.4.
REGRESSION MODELS CHOSEN FOR THE JAMES RIVER AT CARTERSVILLE,
VA (2035000)

Model
Chosen
Water Regressed
Quality Intercept
Constituent (BQ)
Regressed
Slope
Pr ^-1' Coefficient Degrees of
value of Freedom
t Determination
(slope) i
ln(C/Q)
ln(C/Q)
ln(C/Q)
ln(C/Q)
ln(LR)
ln(C/Q)
ln(C/Q)
ln(C/Q)
ln(LR)
vs.ln(l/Q)
vs.lnd/Q)
vs.ln(l/Q)
vs.ln(l/Q)
vs.ln(Q)
vs.ln(l/Q)
vs.ln(l/Q)
vs.ln(l/Q)
vs.ln(Q)
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
-2
*. "I
-2
-4
.- 1
-.^
1
0.
-5
.11
.09
.20
.09
.72
.18
.07
0494
.06
0
0
0
0
1
0
1
1
2
.802
.957
.902
.909
.28
.885
.45
.35
.12
0
0
0
0
0
0
0
0
0
.0001
.0001
.0001
.0001
.0001(2)
.0001
.0001
.0001
.0001(2)
(r2)
0
0
0
0
0
0
0
0
0
.82
.89
.76
.65
.86
.67
.91
.82
.90
54
38
56
49
55
56
56
46
71

(I' Students "t" test for HQ;  slope = 0.  The probability value shown
    answers the question "If the parameter is really equal to zero, what is
    the probability of getting a larger value of it?"  A very small value for
    this probability indicates that the slope is not likely to equal zero
    and, therefore, that flow (or the indicated transformed flow) contributes
    significantly to the model (SAS 1979, Procedure:  General Linear Models).
(2)
   NB_:  The relationship implied by this model may be biased and,
        therefore, may limit the usefulness of the student's "t" test (see
        text).
Computation of Nutrient and Sediment Loads from the Major Tributaries


    Each of the regression equations shown in Tables III.2, III.3, and III.4

were encoded in a Statistical Analysis System (SAS Institute 1979) program.
This program computed a daily load for each day in the period of record of the
flow data (Table 1II.1), multiplied the individual daily load by the relative
frequency of the day's flow (relative frequency = I/ number of days in period
of record), and summed the product over the period of record.  In this way,
the program computed the area under the loading-frequency curve of one-day
duration, which is equivalent to the expected value of daily loading.  This
technique ensured proper computation of expected values whether the model
being used was linear or non-linear.  Computations were performed for annual
and seasonal discharge-frequency distributions of the three major tributaries

for the parameters shown in Table A-l.  The results of these computations for
annual, winter, spring, summer,  arid fall seasons are presented in Tables
III.5(a), III.6(a),  III.7(a), III.8(a), and III.9(a) respectively.  Percentage

breakdowns for each source are listed for annual, winter, spring,  summer, and
fall seasons in Tables III.5(b) ,  III.6(b), III.7(b), III.8(b), and III.9(b)
respectively.
                                  174

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    Not computed here are flow/load ratios which would show that  although the
Susquehanna River has the largest flows,  the ratios of material  to flow,  and
material to drainage area,  are no greater than in the other tributaries.   In
fact, these ratios are less than those in several of the other Bay tributaries.
                                   175
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TABLE III.5(a).  ESTIMATED ANNUAL MEAN DAILY NUTRIENT AND SEDIMENT LOADS TO THE
                 CHESAPEAKE BAY SYSTEM FROM SOURCES TRANSPORTED BY RIVERS
                (ALL VALUES x 10^ LBS/DAY UNLESS OTHERWISE INDICATED)



Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Discharge


Susquehanna
342.84
307.81
228.70
19.41
99.70
15.65
3.84
4.93
7,263.44
43,286.8cfsd


Potomac
95.27
74.38
56.75
3.18
32.14
6.26
1.73
1.83
5,986.22
10,953.9cfsd


James
29.11
18.65
10.31
1.46
17.49
4.54
1.80
1.58
2,979.81
6,879-lcfsd


Other Tribs.
20.39(1)
14.49(2)
9.15
0.74
11.24
1.69
0.57(3)
0.54(4)
1,925.5(5)
3,525cfsd(6)
Total Fluvial
Load to the
Bay System
468.61
415.33
304.91
24.79
160.57
28.14
7.94
8.88
18,155.00
64,644.8cfsd

(DComputed as the sum of N02J3 + TKN

(^'Estimated by computing the mean of DN:TN ratios for the Potomac and James
   and applying to the estimated TN loading rate for the 'Other Tribs.1  The
   Susquehanna was excluded from this calculation because it is a regulated
   (i.e. reservoirs) system; mean DN:TN = 0.711, sd. ป 0.10

(S^Same method as in footnote 2 above; mean DP:TP = 0.336, sd.  - 0.08.

(4)same method as in footnote 2 above; mean OP:TP - 0.320, sd.  = 0.004.

(5)computed by applying the mean unit area sediment load from the Potomac and
   James (497.0 Ibs/mi^/day) to the total drainage area of the  minor
   tributaries (3874 mi^), as measured at the USGS gauges used  by Guide and
   Villa (1972).  The standard deviation of mean areal loading  rate = 29.4.

   Approximate annual mean daily flow for the Rappahannack, Mattaponi,
   Paumunkey, Patuxent, and Chickahominy Rivers from various USGS Water
   Resources Data Publications.  The drainage area above the collected gauges
   is about 3874 square miles.
TABLE III.5(b) .
ESTIMATED PERCENTAGE OF TOTAL ANNUAL NUTRIENT AND SEDIMENT
LOADS FROM CHESAPEAKE BAY TRIBUTARIES

Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Discharge
Susquehanna
73.2
74.1
75.0
78.3
62.1
55.6
48.4
55.5
40.0
67.0
Potomac
20.3
17.9
18.6
12.8
20.0
22.2
21.8
20.6
33.0
16.9
James
6.2
4.5
3.4
5.9
10.9
16.1
22.7
17.8
16.4
10.6
Other Tribs.
4.4
3.5
3.0
3.0
7.0
6.0
7.2
6.1
10.6
5.5

                                  176

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TABLE III.6(a).
ESTIMATED WINTER MEAN DAILY NUTRIENT AND SEDIMENT  LOADS TO  THE
CHESAPEAKE BAY SYSTEM FROM SOURCES TRANSPORTED BY  RIVERS
(ALL VALUES x 103 LBS/DAY UNLESS OTHERWISE  INDICATED)



Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Discharge


Susquehanna
397.20
356.44
264.94
22.47
115.51
17.83
4.44
5.72
8,121.18
50,109.6cfsd


Potomac
95.27
90.58
69.09
3.87
39.14
7.59
2.11
2.23
6,295.99
13,286.9cfsd


James
29.11
24.00
13.34
1.89
22.93
5.89
2.13
1.91
3,616.87
8,811. 7cfsd


Other Tribs.
20.09(D
14.18(2)
10.74
0.87
9.35
1.65
0.53(3)
0.51(4)
2,174.65(5)

Total Fluvial
Load to the
Bay System
571.29
485.2
358.11
29.10
186.93
32.96
9.21
10.37
20,208.69


(1)
   Computed as the sum of N02 3 + TKN.
(2'Estimated using methodology shown in TABLE  III.9(a),  footnote  (2).   Winter
   mean DN:TN = 0.706,  SD = 0.11.

^3'Estimated a;? in TABLE III.9(a),  footnote (3).   Potomac  and James  Winter
   mean DP:TP = 0.320,  SD = .02.

(4)Estimated as in TABLE III.9(a),  footnote (4).   Potomac  and James  Winter
   mean OP:TP = 0.304,  SD = .02.

(^Estimated as in TABLE III.9(a),  tootnote (5).   Potomac  and James  Winter
   mean areal sediment  loading rate = 561.34 Ibs/mi2/day),  SD = 23.6.


TABLE III.6(b).  ESTIMATED PERCENTAGE OF WINTER NUTRIENT AND SEDIMENT  LOADS
                 LOADS  FROM CHESAPEAKE BAY TRIBUTARIES

Const ituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Susquehanna
69.5
73.5
74.0
77.2
61.8
54.1
48.2
55.2
40.2
Potomac
20.3
18.7
19.3
13.3
20.9
23.0
22.9
21.5
31.2
James
6.6
4.9
3.7
6.5
12.3
17.9
23.1
18.4
17.9
Other Tribs.
3.5
2.9
3.0
3.0
5.0
5.0
5.7
4.9
10.8
                                   177
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      TII.7(a).  ESTIMATED SPRING MEAN DAILY NUTRIENT AND  SEDIMENT  LOADS  TO  THE
                 CHESAPEAKE BAY SYSTEM FROM SOURCES  TRANSPORTED  BY  RIVERS
                 (ALL VALUES x 10^ LBS/DAY UNLESS OTHERWISE  INDICATED)

Total Fluvial

Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Discharge

Susquehanna
546.10
485.60
363.46
31.42
159.32
26.08
6.07
7.93
12,110.89
68,011.5cfsd

Potomac
166.84
131.18
98.80
5.69
56.94
11.39
3.01
3.16
11,556.71
18,466.8cfsd

James
44.50
27.89
15.55
2.20
26.94
6.87
2.36
2.15
4,232.68
10,209.3cfsd

Other Tribs.
27.58(0
19.50(2)
14.78
1.22
12.8
2.33
0.71(3)
0.69(4)
3,247.76(5)

Load to the
Bay System
785.02
664.17
492.59
40.53
256.00
46.67
12.15
13.93
31,148.04


(^Computed as the sum of N02>3 + TKN.

(^Estimated using methodology shown in TABLE III.9(a) ,  footnote  (2).   Spring
   mean DN:TN = 0.707, SD = 0.11.

(^Estimated as in TABLE III.9(a), footnote (3).   Potomac  and  James  Spring
   mean DP:TP = 0.304, SD = .06.

(^Estimated as in TABLE III.9(a) , footnote (4).   Potomac  and  James  Spring
   mean OP:TP = 0.295, SD = .03.

   Estimated as in TABLE III.9(a), footnote (5).   Potomac  and  James  Spring
   mean areal sediment loading rate = 838.09 Ibs/mi2/day),  SD  = 228.6.
TABLE III.7(b).
ESTIMATED PERCENTAGE OF SPRING NUTRIENT AND SEDIMENT
LOADS FROM CHESAPEAKE BAY TRIBUTARIES

Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Susquehanna
69.6
73.1
73.8
77.5
62.2
55.9
50.0
56.9
38.9
Potomac
21.3
19.8
20.1
14.0
22.2
24.4
24.8
22.7
37.1
James
5.7
4.2
3.2
5.4
10.5
14.7
19.4
15.4
13.6
Other Tribs.
3.5
2.9
3.0
3.0
5.0
5.0
5.8
4.9
10.4

                                   178

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TABLE III.8(a).
ESTIMATED SUMMER MEAN DAILY NUTRIENT AND SEDIMENT LOADS TO THE
CHESAPEAKE BAY SYSTEM FROM SOURCES TRANSPORTED BY RIVERS

(ALL VALUES x 103 LBS/DAY UNLESS OTHERWISE INDICATED)



Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Discharge


Susquehanna
195.66
178.06
130.92
10.87
56.66
8.92
2.21
2.78
4,398.53
25,193. 3cfsd


Potomac
49.07
37.66
29.64
1.56
16.10
2.92
0.91
0.98
2,531.19
6,147.2cfsd


James
16.83
11.32
6.14
0.87
9.94
2.69
1.38
1.16
2,318.98
4,248.2cfsd


Other Tribs.
11.38(D
8.19^2)
5.16
0.41
6.22
0.93
0.38(3)
0.36(4)
1,142.02(5)

Total Fluvial
Load to the
Bay System
272.94
235.23
171.86
13.71
88.92
15.46
4.88
5.28
10,390.72


'^Computed as the sum of N02)3 + TKN.

(2'Estimated using methodology shown in TABLE  III.9(a),  footnote  (2).  Summer
   mean DN:TN = 0.720, SD = 0.07.

^'Estimated as in TABLE III.9(a), footnote (3).   Potomac  and  James  Summer
   mean DP:TP = 0.412, SD = 0.142.

(^Estimated as in TABLE III.9(a), footnote (4).   Potomac  and  James  Summer
   mean OP:TP = 0.383, SD = 0.07.

^'Estimated as in TABLE III.9(a), footnote (5).   Potomac  and  James  Summer
   mean areal sediment loading rate = 294.79 Ibs/mi^/day),  SD  = 107.24
TABLE III.8(b).
ESTIMATED PERCENTAGE OF SUMMER NUTRIENT AND SEDIMENT
LOADS FROM CHESAPEAKE BAY TRIBUTARIES

Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Susquehanna
71.7
75.7
76.2
79.3
63.7
57.7
45.3
52.7
42.3
Potomac
18.0
16.0
17.3
11.4
18.1
18.9
18.6
18.6
24.4
James
6.2
4.81
3.6
6.4
11.2
17.4
28.3
22.0
22.3
Other Tribs.
4.2
3.5
3.0
3.0
7.0
6.0
7.9
6.8
11.0

                                    179
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TABLE III.9(a).
ESTIMATED FALL MEAN DAILY NUTRIENT AND SEDIMENT LOADS TO THE
CHESAPEAKE BAY SYSTEM FROM SOURCES TRANSPORTED BY RIVERS
(ALL VALUES x 103 LBS/DAY UNLESS OTHERWISE INDICATED)



Constituent
TN
ON
N023
NH34
TKN
TP
DP
OP
SED
Discharge


Susquehanna
228.17
207.42
152.66
12.62
66.06
9.56
2.58
3.42
4,311.54
29,317. 5cfsd


Potomac
48.85
37.86
29.29
1.60
16.29
3.11
0.89
0.96
3,514.34
5,883cfsd


James
17.23
11.44
6.23
0.88
10.22
2.74
1.34
1.13
1,757.22
4,271.7cfsd


Other Tribs.
12.79^1)
9.02(2)
5.82
0.47
6.97
0.98
0.38(3)
0.36(4)
1,132.85

Total Fluvial
Load to the
Bay System
307.04
265.92
194.00
15.57
99.54
16.39
5.19
5.87
10,715.95


 (^Computed as the sum of N0ฃ 3 + TKN.

 (2)Estimated using methodology shown in TABLE III.9(a),  footnote (2).   Fall
   mean DN:TN = 0.719, SD = 0.08.

 (3)Estimated as in TABLE III.9(a), footnote (3).  Potomac and  James  Fall
   mean DP:TP = 0.388, SD = 0.14.

 (^Estimated as in TABLE III.9(a), footnote (4).  Potomac and  James  Fall
   mean OP:TP = 0.361, SD = 0.07.

 (^Estimated as in TABLE III.9(a), footnote (5).  Potomac and  James  Fall
   mean areal sediment bed = 292.43 Ibs/mi2/day),  SD = 16.38


 TABLE III.9(b).  ESTIMATED PERCENTAGE OF FALL NUTRIENT AND SEDIMENT
                 LOADS FROM CHESAPEAKE BAY TRIBUTARIES

Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Susquehanna
74.3
78.0
78.7
81.1
66.4
58.3
49.7
58.3
40.2
Potomac
15.9
14.2
15.1
10.3
16.4
19.0
17.2
16.4
32.8
James
5.6
4.3
3.2
5.7
10.3
16.7
25.8
19.3
16.4
Other Tribs.
4.2
3.5
3.0
3.0
7.0
6.0
7.3
6.1
10.6

                                   180

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NUTRIENT INPUTS FROM SELECTED MINOR TRIBUTARIES
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    Guide and Villa (1972) reported seasonal and annual  nutrient  loadings             .
from five of the next largest tributaries (after the Susquehanna,  Potomac,            •
and James) of the western shore of Chesapeake Bay.   These  basins  are  the              ™
Patuxent, Rappahannock. Mattaponi, Paumunkey, and Chickahominy Rivers,  that
together, drain parts of the Blue Ridge,  Piedmont,  and Coastal                       B
physiographic provinces (Figure III.2).  Loading estimates by Guide and              0
Villa were made for the areas of the tributaries that  drain above  USGS
discharge monitoring stations.  The land-area contributing to these                   mt
estimates totaled 3,874 square miles,  or  about 6.1  percent of the  total Bay           •
drainage basin, with an accummulated mean daily discharge  of  about 3,535
cfsd.
    Guide and Villa observed, for the period June,  1969,  through  August,              •
1970, that these five basins generally contributed  about five percent or              0
less of the nutrient loading of various nitrogen and phosphorus species.
They found that for the entire period of  observation those minor                      M
tributaries contributed six percent, seven percent, three  percent, and               •
three percent of TP, TKN, N02j3, and ^3^4 loads respectively [see
Table III.5(b)].  Similarly, they found that for the winter and spring
months, these basins contributed five percent, five percent,  three percent,           •
and three percent of TP, TKN, N02>3, and  NH3)4 loads respectively. All              W
loading estimates in that study were performed using log-linear models of
loading rate versus mean daily discharge  developed  with  bivariate least              fl|
squares techniques.  These methods were very similar to  those used in the             •
previous section of this chapter and described in Appendix A.
    Estimates of nutrient loadings were developed from the minor  western
shore tributaries by utilizing the percentages reported  by Guide  and  Villa            •
(1972) in conjunction with the estimate made in the previous  section  of the           ™
loadings from the three major tributaries.  For example, the  annual mean
daily TP load from the three major tributaries is estimated in Table                  •
III.5(a) to be 2.64 x 10^ pounds.  If it  is assumed, after Guide  and                  |[
Villa (1972), that 6 percent of the total phosphorus load  comes from  the
minor tributaries, then the 2.64 x 10^ pounds of phosphorus should be                ^
about 94 percent of the total load.  The  total TP load,  therefore, should             •
be about 2.81 x 10^ pounds per day, and by difference, the load from  the              *
minor tributaries about 1.69 x 10-^ pounds per day.
    The annual and seasonal expected daily nutrient loadings  from the minor           H
tributaries have been computed in the manner described above  and  are                  B
presented in the fifth column of Tables III.5(a), III.6(a),  II1.7(a),
III.8(a) , and III.9(a) .  The estimates shown in these tables  for  the  minor-           ^
basin DN, DP, and OP loadings were made,  based upon the  mean of the DN:TN,            •
DP:TP, and OP:TP ratios of the Potomac and James*.   The  estimates  for the
minor tributaries' sediment loads were made by computing the  mean areal
(per unit area) sediment loads on the Potomac and James  ^  and applying               •

'•The Susquehanna loading ratios and areal sediment  yield rates were  not
 used because that river system is regulated by the reservoirs in the                •
 downstream main stem.  Lang (1982) notes that the  Susquehanna reservoirs             ||
 cause sediment deposition and transformation among nutrient  species.
 These transformations would not normally occur in free  flowing streams              _
 like the minor tributaries under consideration.                                     •
                                   181
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them to the 3874 square mile drainage area of the five small  tributaries.   The
calculations used for both these methods are shown in the footnotes  of each
table.
COMPUTATION OF TOTAL NUTRIENT AND SEDIMENT LOADS FROM RIVERINE  TRANSPORTED
SOURCES

    The loading rates for each of the major tributaries and the estimates  of
those from the minor tributaries are included in the 'a1  parts  of  Tables  III.5
through III.9.  These sources are summed to form the sixth column  of those
tables for the annual and for each of the four seasonal loading rates.  The
percentage that each of these sources contributes to the total  load has been
computed and is included as the 'b1  parts of Tables III.5 through  III.9.
    Inspection of the loading percentages shown in Table III.5(b)  reveals  that
the Susquehanna probably carries about 70 percent of the total  nitrogen and 56
percent of the total phosphorus delivered to the Bay each year  from
riverine-borne sources.  Most of these loadings are carried during the  winter
and spring seasons [Table III.6(a) and III.7(a)].  The predominent form of
fluvial-transported nitrogen entering the system is nitrate + nitrite,  with
this effect most pronounced in the spring [Table III.7(a)].  Phosphorus enters
the system from riverine-transported sources primarily in the suspended phase.
    The Susquehanna produces a much smaller fraction of the total
riverine-borne phosphorus load than that of nitrogen, contributing about  50
percent in the winter and 58 percent of the total load in the summer.   The
same trend occurs when considering the sediment loads to the Bay,  with  the
Susquehanna producing only about 40 percent in any season — usually less  than
that transported by the Potomac and James taken together.  The  small fraction
of both the phosphorus and sediment loads produced by the Susquehanna  relative
to its drainage area and flow, no doubt, is due to the trapping of particulate
matter in the reservoirs located on the lower sixty miles of the main  stem of
the river.  For example, in an average spring season, the Potomac  and  James
taken together contribute daily about 840 pounds of suspended sediment  per
square mile of drainage while the Susquehanna would produce only about  447
pounds per square mile, or roughly about half as much.1.
    The data included in Tables III.5(a) through III.9(a) were  used to
generate total expected seasonal and annual riverine-borne mass loadings  of
nutrients and sediments to the Bay system.  The results of these computations
are found in Table III.10.
    Fluvial transported loadings are compared with other nutrient  sources  in
Chapter VIII.  For example, in Table VIII.3(b) shows that riverine transported
sources provide the largest proportion of all nutrients entering the Bay
system in spring, with the exception of orthophosphate.
    In summary, stream-transported loading estimates have been  computed for
the Chesapeake Bay system.  These estimates are well within order  of magnitude
accuracy and are suitable for comparison with the estimated loads  from  other
sources discussed in this paper.
•"•Lang (1982) notes that the Susquehanna system probably begins  to  scour
 (deliver to the Bay)  the sediment stored in the reservoirs  at  flows  above
 400,000 cfs.  Flows that large occur only less than one percent of the  time,
 however.  Most of the time the reservoirs act as an efficient  sediment
 trap.
                                  182

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TABLE III.10.
SEASONAL AND ANNUAL NUTRIENT AND SEDIMENT LOADS TRANSPORTED BY
RIVERS TO THE TIDAL CHESAPEAKE BAY SYSTEM,        ซA^™KihU BY

(MILLIONS OF POUNDS UNLESS OTHERWISE NOTED)
Constituent
TN
DN
N023
NH34
TKN
TP
DP
OP
SED
Winter
51.4
43.7
32.2
2.62
16.8
2.97
0.829
0.933
1.83x109
Spring
72.2
61.1
45.3
3.73
23.6
4.29
1.12
1.28
2.87x109
Summer
25.1
21.6
15.8
1.26
8.18
1.42
0.449
0.486
1.07xl09
Fall
27.9
24.2
17.7
1.42
9.06
1.49
0.472
0.534
9.75xl08

178.1
151.7
111.47
9.06
58.6
10.3
2.907
3.24
6.63xl09

                                 183


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The Tables (A-2, A-3, and A-4), presented in Appendix A,  show that poor
fits (r^^Q.SO) were found in almost all cases,  for the  concentration-
versus-discharge models*  In most cases visual inspection of scatter
diagrams allows a case to be made for heterosodasticity and, for this
reason, the variance-stabilizing transformation was favored in selecting
appropriate models.1  Only when correlation coefficients  were
significantly below 0.65, or 't* tests (Ho:Bi = 0)  indicated that B]_,
the slope, was not significantly different from zero at the 95 percent
confidence level, was a loading rate model chosen.
^•During the course of examination of the concentrations,  predicted by each of
the models over the range of flow observed in the period  of record,  it was
determined that the arithmetic form of the variance-stabilizing transformation
(C/Q versus 1/Q) yielded unrealistically high values for  discharges,  in excess
of those observed during the period of the monitoring program.   The log-log
transformation of this model [ln(C/Q) versus ln(l/Q)] proved to be much better
behaved in predicting concentrations for these higher flows. The curves pro-
duced with this transformation 'flatten out1 very quickly,  as flows  approach
those at the upper limit of the discharge data, observed  during the field pro-
gram.  Therefore, only the log transformed versions of the  variance-stabilizing
transformation were considered for cases exhibiting heterosodasticity.
                                   184

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                                 SECTION  IV

                      POINT SOURCE LOADINGS OF NUTRIENTS
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    Water quality managers and researchers typically divide sources of                  •
water pollution into two broad categories:  point and nonpoint.   Although               •
the distinction between them is not always clear, point sources  are
generally described as those discharging to a water body from a  discrete                —
pipe or ditch.  Examples of point sources are municipal sewage treatment                •
plant discharges, industrial discharges, and combined sewer overflows.                  ••
Nonpoint sources arise from multiple causes and can be dramatically
affected by rainfall and storms.  Examples of nonpoint sources are runoff               •
from urban and suburban storm sewers, agricultural activities, forestry                 |
activities, and atmospheric deposition.
    The objective of this Section is to estimate the load of nutrients                  ซ
discharged to the Bay system from point sources.  Table IV.1 lists the                  I
nutrients analyzed for estimating loads.  Municipal and industrial point                ™
source loadings are estimated separately.  Estimations are made  above and
below the head of tide, or fall line, for the river systems (major/minor)               •
discharging to Chesapeake Bay.  Loadings below the fall line represent                  |
point source  loads to the tidal Bay system in excess of what was computed
in riverine loads of Section 3.                                                         ^
    The river basins that make up the Bay's 64,000 square mile drainage                 •
area are delineated by EPA in its STORET data system and are illustrated in
Figure IV.1.  (STORET is a computerized data base maintained by EPA for the
storage and retrieval of parametric data, relating to the quality of the                B
waterways of  the United States.)  The  "fall line"1 is delineated by USGS               •
hydrologic units (USGS, office of Water Data Coordination in consultation
with the U.S. Water Resource Council)  and is also illustrated in Figure                •
IV.1.  Section III discussed point sources of nutrients discharging above               I
the fall line, reflected in the fluvial loads computed at the fall line
monitoring stations of the Bay's three major tributaries.  Therefore, for
this section, it was important to know which point sources discharge above              •
the line and which discharge below, so that a double counting could be                  •
avoided.  For this analysis, loads generated above the fall line are
included in the  fall line monitoring data, but those generated below the                •
fall line are
 1-The "fall line" defined for the purpose of this Section is not the true                 •
 geologic Fall Line as defined in Section I.  The functional definition of                •
 the fall line used in this paper is the line of demarcation below the
 drainage of the three major tributaries' monitoring stations (Susquehanna
 at Conowingo, MD; Potomac at Chain Bridge, DC; James at Cartersville, VA)                •
 described in Chapter III.  All point sources discharging downstream'of this              B
 line are considered not to have been accounted for in the loads computed in
 the previous Chapter.  This definition assumes that all the point source                 •
 loadings from the Rappahannock and York Rivers (Pamunkey and Mattaponi) are              •
 discharged below the monitoring stations employed by Guide and Villa
 (1972), or that they have begun discharging since 1971 and were not
 incorporated in the loads monitored during that study.  In any event, the                •
 potential for a double counting error is small as can be seen from the data              9
 in Tables IV.12(a) and IV.12(b).
                                    185
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                                  SUSQUEHANNA
                                 RIVER BASIN
         LEGEND

         BASIN BOUNDARY

         FALL LINE
                                             UPPER
                                           CHESAPEAKE
                                           BAYBDELMARVA
                                            RIVER BASIN
                             POTOMA
                           RIVER BASIN
                              RAPPAHANNOCK^
                                 RK RIVER
                      /  JAMES RIVER
                           BAS}N
Figure IV.1.
River systems discharging to Chesapeake Bay.
line indicates the USGS fall line.
                                1R6
Dashed

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TABLE IV.1.  WATER QUALITY VARIABLES
                                   187
                                                                                  I
considered to discharge directly to the tidal waters  of  the  Bay.   Table            •
IV.1 identifies the USGS hydrologic units included below the fall  line of
each major drainage basin.   Hydrologic units, defined by the U.S.
Geological Survey,  in cooperation with the U.S.  Water Resources Council,           •
delineate the hydrographic  boundaries of major river  basins  in the United          •
States.  They provide a standard geographical framework  for  detailed,
water-related planning and  serve as an aid to organizing and disseminating         •
data.  Once point source loadings above and below the fall line for each           |
drainage basin are calculated,  they can be compared to nonpoint source
loadings, and the relative  contribution of each determined.                        _
                                                                                  I
Water Quality Variable	Variable Code

Total Nitrogen (as N)                                   TN                         •
Total Kjeldahl Nitrogen (as N)                          TKN                        *
Total Nitrite plus Total Nitrate                     N02 + N03
  Nitrogen (as N)                                     or N023                      •
Total Ammonia Nitrogen (as N)                           NH34                        •
Organic Nitrogen                                        ORGN
Total Phosphorus (as P)                                 TP
Total Orthophosphorous (as P)                           OP
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TABLE IV.2.  USGS HYDROLOGIC UNITS BELOW THE FUNCTIONALLY-DEFINED  FALL LINE
             OF THE CHESAPEAKE BAY DRAINAGE BASIN


Drainage Basin         USGS hydrologic units included
                       below fall line                                             B


Susquehanna                                                                        •
    0212                                                                           ฃ

Upper Chesapeake             02 -06-00-02
Bay & Delmarva               02-06-00-03                                     B
    0213                     02-06-00-04                                     •
                             02 - 06 - 00 - 05
                             02-06-00-06                                     •
                             02-06-00-07                                     I
                             02 - 06 - 00 - 08
                             02-06-00-09                                     _
                             02-08-01-09                                     •


                                 (continued)                                       B
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TABLE IV.2. (continued)

Potomac                      02 - 07 - 00 - 10
    0214                     02 - 07 - 00 - 11

Rappahannock/York            02 - 08 - 01 - 02
    0215                     02 - 08 - 01 - 03
                             02 - 08 - 01 - 04
                             02 - 08 - 01 - 05
                             02 - 08 - 01 - 06
                             02 - 08 - 01 - 07

James                        02 - 08 - 02 - 05
    0216                     02 - 08 - 02 - 06
                             02 - 08 - 02 - 07
                             02 - 08 - 02 - 08
                             02 - 08 - 01 - 08
Estimation of Nutrient Loads from Municipal Point Sources
    The basic strategy for estimating nutrient loads from municipal  point
sources or publicly owned treatment works (POTWs),  called for merging
computerized data bases and accessing state and facility effluent
monitoring data.  The data bases merged included the EPA 1980 Needs  Survey
(Needs) and the Industrial Facilities Dischargers (IFD)  file.  The  1980
Needs Survey is performed in compliance with the provisions  of Sections  205
(a) and 516 (b)(2) of the Clean Water Act Amendments of  1977, PL 95-217.
The Survey collects technical and administrative data on new and existing
POTWs, which then serve as a basis for Congressional allotment of
construction grant funds among the states.  The Needs data base provided an
inventory of existing and projected flows, and of levels of  treatment  for
POTWs.  The IFD file is a comprehensive data base on municipal and
industrial dischargers assembled by the Monitoring  and Data  Support
Division of EPA.  It was used to verify the Needs file and furnished
valuable locational information.
    Although the merging of these data bases generated an inventory  of
POTWs and provided a substantial amount of information concerning their
flow, level of treatment, and location, it did not  provide information
concerning the concentration of nutrients in effluents.   To  obtain  this
information, we began a systematic analysis of the  CBP-generated data
base.  This analysis determined the percentage of total  flow contributed by
POTWs in different flow (size) categories.  It indicated that there  are  580
POTWs located within the Chesapeake Bay drainage basin having a combined
flow of 1350 million gallons/day (MGD).  Further analysis revealed that  96
percent of this flow is contributed by the 197 POTWs larger  than 0.5 MGD,
and 78 percent of the flow by the 47 POTWs larger than 5.0 MGD.  Based on
this analysis and existing data needs,  we requested necessary information
from the Maryland Department of Health and Mental Hygiene, Office of
Environmental Programs (OEP),  the Virginia State Water
Control Board (VSWCB), and the Pennsylvania Department of Environmental
Resources (DER).
                                  188

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                                                                                  I
    Each State staff was requested to provide 1980 data on operational             •
flow, total nitrogen (TN), total phosphorus (TP),  five-day biological              •
oxygen demand (BOD5), and total suspended solids (SED)  concentration for
the POTWs larger than 5.0 MGD within their political  boundaries.   In               •
addition, the tasks were intended to determine the status of certain               0
dischargers that were in question.  State expertise in  these areas  was
invaluable.  In the meantime, estimates of the concentration of  these              •
pollutants in wastewater after different levels of treatment were made             •
(Barth 1981)1 and included in the CBP data base.  They  are presented in
Table IV.3.  This table shows that for BOD, a lot  of  difference  exists
between primary and secondary treatment.  However, to obtain decreases in N        •
and P, tertiary treatment must probably be used.  Later,  program                   m
requirements dictated that the TN and TP estimates be broken down  into
various species.  This information (Barth 1981)1 is presented in Table             •
IV.4.  Again, not until AWT is used, will any significant decreases in N           •
and P occur.
    The response from States staffs was very good, and  we updated  the CBP
data base with the provided information.  In addition,  we contacted several        •
POTW operators and requested actual data or estimates of nutrient                   •
concentrations in their effluent.  This information was also added  to the
CBP data base and is presented in Table IV.5.                                      •
    Using the updated CBP data base and our functional  definition  of the           |
fall line, we calculated nutrient loads from POTWs above and below the fall
line.  This information is presented in Table IV.6 and  is currently                ซ
undergoing final review by the states' staffs.  This table shows that the          •
largest loadings above the fall line are discharged within the Susquehanna
drainage basin and, with the exception of TN (Potomac 57,489 Ibs/day vs.
James 43,770 Ibs/day), the largest loadings below the fall line  are                •
discharged within the James drainage basin.  The smallest loadings  above           •
the fall line are discharged within the Upper Chesapeake Bay - Delmarva
drainage basin and below the fall line within the Rappahanock - York               •
drainage basin.  The large loadings from the Susquehanna indicate  that its         |[
basin is largely located above the fall line, but the small loadings from
the Upper Chesapeake Bay - Delmarva indicate it is mostly located  below the        ^
fall line.  The small load from the Rappahannock/York is due to lack of            •
development.  It is interesting to note that although the Potomac  drainage
basin receives the greatest total volume of treated wastewater (589 MGD),
its total TP load (9,583 loads/day) is less than that from the Susquehanna         I
(16,052 Ibs/day) and James (11,920 Ibs/day).  This results from the large          •
volume of wastewater undergoing phosphorus removal at the Blue Plains POTW.
1 Personal Communication:   "Fractions  of  Nitrogen  and  Phosphorous  in
 Effluents," and others,  E.F.  Barth, Biological  Treatment  Section,
 Municipal Environmental  Research Laboratory,  U.S.  Environmental
 Protection Agency,  Cincinnati,  OH,  1981.
                                                                                   I

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                                   189
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TABLE IV.3.  RANGE OF POTW CONSTITUENTS CONCENTRATIONS BASED ON LEVEL OF
             TREATMENT  (MG/L) (SOURCE:  BARTH 1981)

Treatment Level
None (Raw Discharge)
Primary 1
Advanced Primary^
Secondary-^
Advanced Secondary
(Nitrification)
Tertiary
(Nitrogen removal
and P removal)

210
130
60
20

10


5
BOD5
- 300
- 140
- 65
- 30

- 20


- 10
SED
230
100
40
20

10


5
- 300
- 130
- 52
- 30

- 20


- 10
15
13.5
12
12

10


3
TN
- 30
- 28
- 25
- 25

- 20


- 10

9
9
8
7

1


0.
TP
- 11.5
- 10
— Q
- 9

- 2


1-2

^•Preliminary treatment (bar screen and grit removal) and primary
 sedimentation.
9  •
^Primary treatment with post aeration.

•^Activated sludge, rotating biological contactors, or low-rate trickling
 filters.
TABLE IV.4,   ESTIMATE OF DISTRIBUTION OF POTW NITROGEN AND PHOSPHORUS INTO

             VARIOUS FRACTIONS ACCORDING TO SELECTED TREATMENT PROCESS
             (MG/L) (SOURCE:   BARTH 1981)  THE TN AND TP VALUES IN THIS TABLE
             REPRESENT THE AVERAGE OF THE RANGE OF TN AND TP CONCENTRATIONS

             FROM TABLE IV.3

Nitrogen
Treatment Org-N

None
(Raw
Pr imary
Advanc e
Pr imary

9
discharge)
7.0

6.5
Secondary 3.0
AST
AWT
2.0
1.5
TKN

22.5

20.75

18.5
16.5
3.0
2.5
NH34

13.5

13.75

12
13.5
1.0
1.0
Fractions
N023

0

0

0
2.0
12
4.0
TN

22.5

20.75

18.5
18.5
15
6.5
Phosphorus Fractions
Insol +
Poly
6.75

5.25

4.25
1.2
0.5
™
OP

3.5

4.25

4.25
6.8
1.0
1.05
TP

10.25

9.5

8.5
8.0
1.5
1.05

                                  190

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TABLE IV.6,  ESTIMATES OF NUTRIENT LOADS FROM MUNICIPAL POINT SOURCES
            ABOVE AND BELOW THE FUNCTIONALLY-DEFINED FALL LINE
            (ALL VALUES IN LBS/DAY EXCEPT FLOW IN MGD)

Drainage
Basin


Susquehanna

(0212)





Upper
Chesapeake
Bay and
De Imarva

(0213)




Potomac

(0214)






Rappahannock/
York

(0215)



Water Quality
Parameter
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW

Above
105899
16018
11504
48098
33502
14596
24353
9149
329
64
7
4
41
16
25
8
7
.3
29972
2883
2555
13089
8616
3760
6049
3014
87
355
55
42
310
112
198
69
43
2.4

Below
134
34
29
85
71
14
58
13
.6
54824
8224
5781
26406
12916
9482
10404
4303
164
50277
6700
5251
57489
26764
30298
23445
9263
502
2675
576
458
1542
1196
346
922
274
10.4

Total
106033
16052
11533
48183
33573
14610
24411
9162
330
54888
8231
5785
26447
12932
9507
10412
4310
164.3
80249
9583
7806
70578
35380
34058
29494
12277
589
3030
631
500
1852
1308
544
991
317
12.8
                                  (continued)
                                  192

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TABLE IV.6. (continued)


James

(0216)




BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
7349
1574
1218
3730
3280
450
2567
713
24
74688
10346
7237
43770
39303
7216
32991
6277
231
82037
11920
8455
47500
42583
7666
35558
6990
255

Estimation of Nutrient Loads from Industrial Point Sources

    Types of industrial activity with the potential to discharge the
nutrients TP, TN, TKN, and NH3j4 were identified through discussion with
State and EPA officials.  The Standard Industrial Classification (SIC)
system, which classifies industries by their economic activity,  was used to
assign codes to these discharges.  For example,  industries engaged in the
preparation of fresh or frozen packaged fish and seafoods were assigned SIC
code 2092, the code corresponding to that particular economic activity.
For industries engaged in petroleum refining, the SIC code assigned was
2911, the code denoting petroleum refinering as  the primary economic
activity.  Table IV.7 lists the industrial economic activities considered
to be nutrient generators and their corresponding SIC codes.  The advantage
of SIC codes is the speedy identification of all dischargers engaged in a
particular economic activity.
    The EPA/CBP computerized data base was accessed to retrieve the
industries within the selected SIC - defined categories and located within
the Chesapeake Bay drainage basin.  This EPA data base includes:  the
Management Information Control System (MICS) - EPA Region Ill's
(Philadelphia) computerized system containing basic information on all
NPDES permitees; the Virginia NPDES permit file  - the Virginia computerized
system containing NPDES permit conditions, facility information, and
discharge monitoring report (DMR) data; the National Enforcement
Investigations Center (NEIC) system - an EPA data base generated by EPA's
effort to define Major/Minor dischargers on a uniform national basis; and
the already discussed IFD file.
    Concentrations of nutrients expected to be found in the effluent from
dischargers within a selected SIC category were  obtained from EPA's
Effluent Guideline Division (EGD) and the literature.  Maryland 1979 NPDES
permit compliance monitoring data and Virginia DMR's were also reviewed for
observed  nutrient data.  Table IV.8(a) presents the nutrient
concentrations estimated for the various SIC categories when observed data
were absent.  Table IV.8(b) identifies the source of the estimated
concentrations.
    Most flow data from the dischargers of interest were based on state
DMR's or from NPDES permits.  In some cases, flow data were not available
from the sources and so were estimated from a particular industrial
                                   193
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activity.  Loads generated in this manner, however, constitute only a small
percentage of the total loading from industrial sources and are identified
as 'estimated' load (17 percent of TP and seven percent of TN).  Table IV.9
presents assigned flows and the information source.  Table IV.9 also
identifies the data base providing observed/permitted flows.
    Anomalies in the nutrient loadings computed with this approach were
corrected by review of assigned 'concentrations and flows.  In many cases,
this resulted in close examination of an individual discharger and the
assignment of more accurate nutrient loadings based on observed data.
Table IV.10 lists these dischargers and their assigned nutrient loads.  In
addition, State officials familiar with dischargers within their
jurisdiction have reviewed the loadings assigned to specific dischargers
for reasonableness and completeness.  The industrial point source loadings
calculated in this manner for each drainage basin above and below the fall
line are presented in Tables IV.ll(a), (b), and (c).  These tables reveal
several trends.  Table IV.ll(b) indicates that the largest TP and TN
contributions from industrial point sources occur within the James drainage
basin.  Most of the TP load is contributed by several large meat rendering,
poultry processing, and food processing plants.  The large TN load is
attributable to these same dischargers, and to the presence of petroleum
refineries and a fertilizer manufacturer in the basin.  For comparative
purposes, the largest industrial load of TP (1906 Ibs/day in the James)
constitutes only 15.5 percent of the total industrial and municipal TP load
below the fall line in the James.  From this we can conclude that
industrial point sources are relatively minor contributors of nutrients.
                                   194

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TABLE IV.7.  SIC CODE AND ECONOMIC ACTIVITY
SIC Code                    Economic Activity

2011          Meat Packing & Rendering
2016          Poultry Processing
2023          Condensed and Evaporated Milk
2024          Ice Cream and Frozen Desserts
2026          Fluid Milk
2033          Canned Fruits, Preserves and Jams
2035          Pickled Fruits and Vegetables
2037          Frozen Foods
2038          Frozen Specialties
2077          Animal and Marine Fats and Oils
2091          Canned and Cured Fish and Seafoods
2092          Fresh or Frozen Packaged Fish and Seafoods
2812          Industrial Inorganic Chemicals - Alkalines and Chlorine
2813          Industrial Inorganic Chemicals - Industrial Gases
2816          Industrial Inorganic Chemicals - Inorganic Pigments
2819          Industrial Inorganic Chemicals - Not Elsewhere Classified
2821          Plastics Materials, Synthetic Resins, & Elastomers
2822          Synthetic Rubber
2823          Synthetic Organic Fibers
2824          Industrial Organic Chemicals - Cyclic Crude & Pigments
2833          Medicinal Chemicals & Botanical Products
2869          Industrial Organic Chemicals - Not Elsewhere Classified
2873          Manuf. of Nitrogenic Fertilizers
2874          Manuf. of Phosphatic Fertilizers
2879          Pesticides & Agricultural products
2891          Adhesives & Sealants
2892          Explosives Manufacture
2893          Printing Ink
2911          Petroleum Refineries
3111          Leather Tanning and Finishing
3312          Blast Furnaces, Steel Works
3321          Gray Iron Foundries
3322          Malleable Iron Foundries
3411          Metal Can Manufacture
3471          Electroplating
3612          Power Distribution & Specialty Transformers
3621          Electrical Industry Apparatus
3644          Electric Lighting & Equipment
3674          Semiconductors & Related Devices
3679          Electronic Components
3662          Radio Detection Equipment & Apparatus
3731          Ship Building & Repair
3861          Photographic Equipment & Supplies
6515          Mobile Home Site Operators
7011          Hotels, Motels, and. Tourist Courts
7215          Coin-Operated Laundries and Dry Cleaning
8211          Elementary and Secondary Schools
8221          Colleges and Universities
                                   195
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TABLE

SIC
Code
2011
2016
2023
2024
2026
2033
2037
2038
2077
2091
2092
2812
2813
2816
2819
2821
2822
2823
2824
2865
2869
2873
2874
2879
2891
2892
2893
2911
3111
3312
3321
3322
3411
3471
3612
3621
3644
3674
3679
3662
3731
3861
6515
7011
7215
8211
8221




IV.8(a).

SED
67
90.36
157
157
157
302
302
302

520
520
18.5
18.5
18.5
18.5
30.1
30.1
30.1
30.1
30.1
30.1

31
18.5


30.1
27.16
27.16
27.16
27.16
25
25
25
25
25
25
25
25
25
25
40
40
43
40
40





SIC CODE AND ESTIMATED
CONSTITUENTS (mg/L)

BODS
68
130.9
338
338
338
503
503
503
18.8
942.6
942.6



22.7
22.7
22.7
22.7
22.7
22.7





22.7
27.5
27.5
27.5
27.5
7.25
7.25
7.25
7.25
7.25
7.25
7.25
7.25
7.25
7.25
40
40
43
40
40




TP TN
20
7.67 43.
10.8
10.8
10.8
190.8
190.8
1.90.8
7.1
12.02
12.02
.183
.183
.183
.183






19.2







.35
.35
.35
.35
.35
.35
.35
.35
.35
.35
9 20
9 20
9
9 20
9 20

196


CONCENTRATIONS OF WATER QUALITY

NH3 TKN
8.6
61 21.2 42.9
61.2
61.2
61.2
18
18
18
8.5
6.8 94.1
6.8 94 . 1
3.61
3.61
3.61
3.61
11.3
11.3
11.3
11.3
11.3
11.3
15
15
.85
3.63
15
15
11.3
8.33
8.3
8.3
8.3
1.15
1.15
1.15
1.15
1.15
1.15
1.15
1.15
1.15
1.15








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TABLE IV.8(b).  SIC CODE AND SOURCE OF ESTIMATED CONSTITUENT CONCENTRATIONS
SIC                          Source of value
Code
                                 (continued)
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2011    RFF Pollution Matrix Lookup Routine
2016    Average of data collected in 1979 MD.  Compliance monitoring (3            •
        plants)                                                                    •
2023    RFF Pollution Matrix Lookup Routine
2024    RFF Pollution Matrix Lookup Routine                                        •
2026    RFF Pollution Matrix Lookup Routine                                        •
2033    RFF Pollution Matrix Lookup Routine
2037    RFF Pollution Matrix Lookup Routine
2038    RFF Pollution Matrix Lookup Routine                                        •
2077    RFF Pollution Matrix Lookup Routine                                        •
2091    "Waste Treatment & Disposal From Seafood Processing Plants"
        EPA-600/2-77-157, August 1977                                              •
2092    "Waste Treatment & Disposal From Seafood Processing Plants"                |
        EPA-600/2-77-157, August 1977
2812    RFF Pollution Matrix Lookup Routine                                        _
2813    RFF Pollution Matrix Lookup Routine                                        I
2816    RFF Pollution Matrix Lookup Routine
2819    RFF Pollution Matrix Lookup Routine
2821    RFF Pollution Matrix Lookup Routine                                        I
2822    RFF Pollution Matrix Lookup Routine                                        I
2823    RFF Pollution Matrix Lookup Routine
2824    RFF Pollution Matrix Lookup Routine                                        •
2865    RFF Pollution Matrix Lookup Routine                                        |
2869    RFF Pollution Matrix Lookup Routine
2873    EPA Effluent Guidline Division                                             _
2874    EPA Effluent Guidline Division                                             •
2879    RFF Pollution Matrix Lookup Routine                                        ™
2891    RFF Pollution Matrix Lookup Routine
2893    RFF Pollution Matrix Lookup Routine                                        •
2911    RFF Pollution Matrix Lookup Routine                                        I
3111    RFF & Maryland NDPES permit compliance data
3312    RFF & Maryland NDPES permit compliance data                                •
3321    RFF & Maryland NDPES permit compliance data                                J
3322    RFF & Maryland NDPES permit compliance data
3411    RFF Pollution Matrix Lookup Routine
3471    RFF Pollution Matrix Lookup Routine                                        •
3612    RFF Pollution Matrix Lookup Routine                                        •
3621    RFF Pollution Matrix Lookup Routine
3644    RFF Pollution Matrix Lookup Routine                                        •
3674    RFF Pollution Matrix Lookup Routine                                        |
3679    RFF Pollution Matrix Lookup Routine
3662    RFF Pollution Matrix Lookup Routine                                        _
3731    RFF Pollution Matrix Lookup Routine                                        •
                                   197
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TABLE IV.8(b).   (continued)


3861    RFF Pollution Matrix Lookup Routine
6515    Earth - EPA,  MERL,  Cincinnati
7011    Barth - EPA,  MERL,  Cincinnati
7215    RFF Pollution Matrix Lookup Routine
8211    Barth - EPA,  MERL,  Cincinnati
8221    Barth - EPA,  MERL,  Cincinnati
                                   198

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TABLE IV.9.  SIC CODE,  ASSIGNED FLOW,  AND SOURCE OF VALUE (MGD)
SIC Code
2011
2016

2023
2024
2026
2033
2035
2037
2038
2077
2091
2092
2812
2813
2816
2819
2821
2822
2823
2824
2865
2869
2873
2874
2879
2891
2892
2893
2911
3111
3312
3321
3322
3411
3471
3612
3621
3644
3674
3679
3662
3731
3861
6515
7011
7215
8211
8221
Assigned
  Flow

 .09
 .34

 .001
 .001
 .001
 .001
 .05
 .001
 .001
 .001
 .001
 .001
            Source
 .05
 .05
  .05
  .01
  .1
  .015
  .039
Average of Maryland NPDES "fact sheet data"
Average of Mayland 1979 NPDES compliance
monitoring data
Author's Best judgement
Author's Best judgement
Author's Best judgement
Author's Best judgement
Author's Best judgement
Author's Best judgement
Author's Best judgement
Author's Best judgement
State official recommendation
State official recommendation
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
Author's Best judgement
Author's Best judgement
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
IFD NEIC data bases
Author's Best judgement
Author's Best judgement
Author's Best judgement
Average of MD "fact  sheet" data
Average cr: MD "fact  sheet" data
                                  199
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TABLE IV.10.  ASSIGNED INDUSTRIAL FACILITIES NUTRIENT LOADINGS FROM OBSERVED
             DATA* (LBS./DAY) IN THE ABSENCE OF THESE KINDS OF DATA, LOADS
             WERE CALCULATED FROM CONCENTRATIONS SHOWN IN TABLE IV.8(a)

Basin




0214
0214
0214


0214
0214
0214

0216
0214
0214

0213

0213
0216

0213
0214
0214
0214
0215
State NPDES Facility Name
(permit #)
VA
VA
VA

VA
VA
VA

VA
VA
VA
VA
VA
VA
VA
VA
VA
MD

MD
VA

MD
VA
VA
VA
VA
1856
248
1651

1899
1902
1961

4782
2160
2178
2313
27871
3387
4031
2402
29416
1201

299
5291

311
2208
2267
4669
3115
Thiokol Fibers Div
Radford Army Ammunition plant
Burlington Ind. Inc.
Clarksville
Crompton-Shenandoan Company
Rocco Farms Foods Edinburg
Rockingham Poultry Market
Co. Inc.
TP
1


36




.76


.4




Wright Chemical Corp. Waverly
Dupont Waynesboro
Merck Co. Inc. Stonewall PI.
Wampler Food Hinton

Virginia Chemicals Inc.
Holly Farms Glen Allen
General Electric Waynesboro


710

1
244
57
5
0
Bethlehem Steel 1660
Sparrows Point
FMC Corp. Organic Chem Div
Allied Chem. Corp
Hopewell
WR Grace Davidson Chem. Div.
Avtex Fibers Inc.
Virginia Oak Tannery
Dupont Spruance
Chesapeake Corporation

400






403

.0

.2
.0
.0
.4
.26
.0

.0






.0
NH34 TKN
6
129

10
0
36

12
0
92
1744
3


90



1488


1637
2203

15


.4 7.92
.8

.10 157.6
.10
.0

.0 25.0
.66
.4 347.0
.0
.6


.0



.0 3365.0


.0
.0
472.0
.0
94.0
631.0
SIC
2297
2892

2269
2016
2016

2016
2891
2821
2835
2016

2819
2016
3471


3312
2869

2869
2819
282
3111
2821
2621

  305b reports, DMRs,  and facility representatives
                                  200

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TABLE IV.ll(a),  ESTIMATES OF NUTRIENT LOADS FROM INDUSTRIAL POINT
                SOURCES FROM ABOVE THE FUNCTIONALLY-DEFINED FALL LINE
                (mg/L)

Drainage
Basin


Susquehanna
(0212)


Upper
Chesapeake
Water Quality
Parameter
BODS
TP
TN
NH34
TKN
BOD5
TP
TN
Above the fall
Estimated
799
183
386

2



linel

Measured Total
5718
214
2334
540
2318
0
0

6517
397
2720
540
2320
0
0









Bay and Delmarva NH34
(0213)


Potomac
(0214)


Rappahannock/
York
(0215)


James

(0216)

TKN
BOD5
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN

132
24
42

.5





36
1



0
2589
95
5194
1917
3870
•
•
•

•
34
2
7.
•
7.
0
2721
119
5236
1917
3871
29 .29
01 .01
05 .05

05 .05
71
3
4 7.4
01
4 7.4

















(^ 'Estimated'
dischargers
unmeasured
judgement .
or assessed
by expected
These loads
and 'measured'
refer to how
or types of dischargers were
flow values for individual
determined.
Estimated flows
flows and are based on averages of similar dischargers or
Measured flows
data bases. Es
concentrations
, in turn, were
are recorded
flows from NPDES 'fact sheet1
timated and measured flows
of nutrients
designated as
in wastewater
are
best
files
were then multiplied
to calculate loads.
estimated or measured.
                                   201
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TABLE IV.ll(b).  ESTIMATES OF NUTRIENT LOADS FROM INDUSTRIAL POINT
                SOURCES FROM BELOW THE FUNCTIONALLY-DEFINED FALL LINE
                (mg/L)

Drainage Water Quality
Basin


Susquehanna
(0212)


Upper
Chesapeake
Bay and Delmarva
(0213)


Potomac
(0214)


Rappahannock/
York
(0215)


James

0216)

Parameter
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
Below the fall line
Estimated
609
133
294

5
1192
301
296
7
45
477
68
153
1
16
1115
71
248
90
245
91
16
10
0
10
Measured





9760
488
6561
3815
6557
507
747
1513
203
1993
1422
24
575
255
445
17880
1890
3755
2295
4159
Total
609
133
294

5
9271
789
6857
3822
6602
984
815
1666
204
2009
2537
95
823
345
690
17971
1906
3765
2295
4169

                                   202

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TABLE IV.ll(c). , ESTIMATES OF NUTRIENT LOADS FROM INDUSTRIAL POINT SOURCES
                FROM ABOVE AND BELOW THE FUNCTIONALLY-DEFINED FALL LINE
                (LBS/DAY)

Drainage Water Quality
Basin


Susquehanna
(0212)


Upper
Chesapeake
Bay and Delmarva
(0213)


Potomac
(0214)


Rappahannock/
York
(0215)


James

0216)

Parameter
BODS
TP
TN
NH34
TKN
BOD5
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
BODS
TP
TN
NH34
TKN
Above and
Estimated
1409
316
680

7
1192
301
296
7
45
609
92
195
1
17
1115
71
248
90
245
126
17
10
0
10
Below the fall
Measured
5718
214
2334
540
2318
9760
448
6561
3815
6557
3096
842
6707
2120
5863
1422
24
575
255
445
17914
1892
3762
2295
4166
line
Total
7127
530
3014
540
2325
11952
749
6857
3822
6602
3705
934
6902
2121
5880
2537
95
823
345
690
18040
1909
3772
2295
4176

                                    203
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Estimated Total Point Source Nutrient Loading

    The total estimated municipal point source loading data (Table IV.6)  and
the total estimated industrial point source loading data [Tables  IV.ll(a),
(b), and (c)] have been summed to generate a table of estimated total nutrient
loadings from all point sources to the Bay system [Tables IV.12(a),  (b),  and
(c)].   The data presented in Table IV.12 are broken out to delineate loadings
from above and below the functional fall line.
    Tables IV.12(a), (b), and (c) indicate the relative magnitude of pollutant
loadings from municipal and industrial point sources.  By changing these  loads
to percentages, it can be seen from Table IV.12 that, above the fall line,  the
industrial contribution of total TP ranges from two percent in the James  to
four percent in the Potomac.  For total TN, the industrial contribution ranges
from two percent in the James to 28.5 percent in the Potomac.   Calculations on
data in Table IV.12(b) indicate that the industrial contribution of TP below
the fall line ranges from 8.7 percent in the Upper Chesapeake  Bay Delmarva
drainage basin to 79.6 percent in the Susquehanna.  However,  it should be
pointed out that very little of the Susquehanna is below the fall line.  More
representative of industrial point source nutrient contributions  below the
fall line is the Potomac with industrial point sources contributing 10.8
percent of the total TP to its drainage basin and 14 percent  to the
Rappahannock/York drainage basin.  Without the Susquehanna, the industrial
contribution to the TN load, below the fall line, ranges from  2.8 percent in
the Potomac to 34.7 percent in the Rappahannock/York.  In the  James River,
industrial point sources contribute 12.7 percent and, in the upper Bay,
Delmarva 20.6 percent.
    Table IV.12(c) presents the industrial and municipal contribution to  the
total drainage basin load.  The industrial contribution to the total TP load
ranges from 3.2 percent in the Susquehanna to 13.8 percent in  the James.  The
TN industrial load ranges from 5.8 percent in the Susquehanna  to  30.7 percent
in the Rappahannock/York.  From this information, it can be concluded that
although industrial point sources of nutrients may be significant in local
areas, overall their relative contribution to the Bay is minor in comparison
to the loadings from municipal point sources.
    The loadings indicated as being below the fall line are intended to
represent the point source load to the tidal Bay system in excess of that
already included in the computations of Section III.   These data  were employed
to compute the total estimated seasonal and annual mass loading of nitrogen
and phosphorus species to the tidal Chesapeake Bay system.  They  are shown  in
Table IV.13.  This table shows that nitrogen and nitrogen species constitute
the largest proportion of nutrients reaching the tidal Bay from point
sources.  Because each season contains approximately equal numbers of days,
seasonal loads (based on daily flows) do not reveal large differences.
Climatelogical and other influences (e.g., infiltration/inflow) were not
considered in breaking out seasonal loads in this analysis.
                                  204

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TABLE IV.12(a).  ESTIMATES OF NUTRIENT LOADS FROM MUNICIPAL AND INDUSTRIAL POINT
                SOURCES FROM ABOVE THE FUNCTIONALLY-DEFINED FALL LINE
                (LBS/DAY EXCEPT FLOW IN MGD)

Drainage
Basin


Susquehanna

(0212)





Upper
Chesapeake
Bay and
Delmarva

(0213)




Potomac

(0214)






Rappahannock/
York

(0215)



Water Quality
Parameter
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
Above the fall line
Municipal
105899
16018
11504
48098
33502
14596
24353
9149
329
64
7
4
41
16
25
8
7
.3
29972
2883
2555
13089
8616
3760
6049
3014
87
355
55
42
310
112
198
69
43
2.4
Industrial
6517
397

2720
2320

540











2721
119

5236
3871

1917











Total
112416
16415

50818
35822

24893


64
7
4
41
16
25
8
7
0.3
32693
3002

18325
12487

7966


355
55

310
112

69


                                   (continued)
                                   205
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TABLE IV.12(a).  (continued)
            Drainage         Water  Quality             Above  the  fall  line
 J|         Basin             Parameter        Municipal	Industrial	Total

                                BODS             7349              71           7420
 _                             TP              1574               3           1577
 M         James               OP              1218
                    TN              3730              7.4        3737
                    TKN             3280              7.4        3287
(0216)              N023             450
                    NH34            2567                         2567
                    ORGN             713
                    FLOW              24
                                  206

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TABLE IV.12(b).
ESTIMATES OF NUTRIENT LOADS FROM MUNICIPAL AND INDUSTRIAL POINT
SOURCES BELOW THE FUNCTIONALLY-DEFINED FALL LINE
(LBS/DAY EXCEPT FLOW IN MGD)

Drainage
Basin


Susquehanna

(0212)





Upper
Chesapeake
Bay and
De Imarva

(0213)




Potomac

(0214)






Rappahannock/
York

(0215)



Water Quality
Parameter
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
NO 23
NH34
ORGN
FLOW
Below the fall line
Municipal
134
34
29
85
71
14
58
13
.6
54824
8224
5781
26406
12916
9482
10404
4303
164
50277
6700
5251
57489
26764
30298
23445
9263
502
2675
576
458
1542
1196
346
922
273
10.4
Industrial
609
133

294
5




9271
789

6857
6602

3822


984
815

1666
2009

204


2537
95

823
690

345


Total
743
167

379
76




64095
9013

33263
19518

14226


51261
7515

59155
28773

23649


5212
671

2365
1886

1267


                                   (continued)
                                   207
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TABLE IV.12(b).  (continued)
Drainage

Basin
James


(0216)
Water Quality

  Parameter


    BOD5
    TP
    OP
    TN
    TKN
    N023
    NH34
    ORGN
    FLOW
        Below the fall line

Municipal	Industrial	Total
 74688
 10346
  7237
 43770
 39303
  7216
 32991
  6277
   231
17971
 1906


 6044
 4169


 2295
92659
12252


47535
43472


35286
                                  208

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TABLE IV.12U).  ESTIMATES OF NUTRIENT LOADS FROM MUNICIPAL AND INDUSTRIAL POINT
                SOURCES TOTALED ABOVE AND BELOW THE FUNCTIONALLY-DEFINED FALL
                LINE (LBS/DAY EXCEPT FLOW IN MGD)

Drainage
Basin


Susquehanna

(0212)





Upper
Chesapeake
Bay and
Delmarva

(0213)




Potomac

(0214)






Rap pahannock/
York

(0215)



Water Quality
Parameter
BODS
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
BOD5
TP
OP
TN
TKN
N023
NH34
ORGN
FLOW
Above and
Municipal
106033
16052
11533
48183
33573
14610
24411
9162
330
54888
8231
5785
26447
12932
9507
10412
4310
164.3
80249
9583
7806
70578
35380
34058
29494
12277
589
3030
631
500
1852
1308
544
991
317
12.8
below the fall
Industrial
7127
530

3014
2325

540


11952
749

6857
6602

3822


3705
934

6902
5880

2121


2537
95

823
690

345


line
Total
113160
16582

51197
35898

24951


66840
8980

33304
19534

14234


83954
10517

77480
41260

31615


5567
726

2675
1998

1336


                                   (continued)
                                  209
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TABLE IV.12(c). (continued)
Drainage Water Quality Above and below the fall
Basin Parameter Municipal Industrial
BOD5 82037 18040
TP 11920 1909
James OP 8455
TN 47500 3772
(0216) TKN 42583 4176
N023 7666
NH34 35558 2295
ORGN 6990
FLOW 256

210
line
Total
100077
13829
51272
46759
37853



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TABLE IV.13.  TOTAL ESTIMATED AVERAGE SEASONAL AND ANNUAL NUTRIENT LOADINGS           •
             FROM POINT SOURCES TO THE TIDAL PORTIONS(l) OF THE CHESAPEAKE

             BAY SYSTEM

Constituent
TN
N023
NH34
TKN
TP
OP
Daily
(Thousands of Pounds)
142.7
47.4
74.5
93.7
29.6
18.8
Winter
Spring
(Millions
12.8
4.26
6.70
8.44
2.67
1.69
13.1
4.36
6.85
8.62
2.72
1.73
Summer
of Pounds)
13.1
4.36
6.85
8.62
2.72
1.73
Fall

13.0
4.31
6.78
8.53
2.70
1.71
Annua 1

52.1
17.3
27.2
34.2
10.8
6.85
 ^'Discharges entering the system downstream of the functional fall line as
             in this
                                                                                     I

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                                    211
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                                  SECTION V

                         BOTTOM FLUXES OF NUTRIENTS
CONCEPTUAL FRAMEWORK

    The bottom sediments of Chesapeake Bay and its tributaries  constitute  a
large reservoir of nutrients available for potential  release to the  water
column.  The nutrients enter the sediments primarily  as organic and
inorganic particulates that settle out of the overlying water.   Biological
and chemical reactions convert the organicallly-bound nutrients to
inorganic forms, reaching an equilibrium distribution between a soluble
phase in sediment interstitial (pore)  water and a particulate phase
adsorbed onto the sediment solids.  Thus,  the sediments represent  a  sink
capable of retaining a portion of the nutrients settling out of the  water
column.  But they also represent a source because part of the remineralized
nutrients diffuse out of the sediments through the pore water,  part  is
advected out via sediment disturbance  by burrowing animals or physical
resuspension; and those remineralized  on the sediment surface escape
directly to the overlying water.
    The sediments are a complex environment so, for analytical  purposes, we
adopted a simplified conceptual framework, shown in Figure V.I. We  will
consider the sediments to have discrete layers distinguishable  by  the
chemical and biological processes occurring in each.   Figure V.I diagrams  a
vertical section of sediment.  The organic fluff layer is composed of
colloidal material and fine particles  that are unconsolidated,  have  a
density near that of water, and may be resuspended and transported by near-
bottom currents.  The underlying, compacted surface layer is somewhat more
consolidated material that is not readily resuspended in the water column,
and its surface is oxidized when the overlying water  contains oxygen.  If
the overlying water becomes anoxic, so does the compacted surface  layer.
The largest portion of the sediments is the compacted, anoxic layer, which
is subject to biological processes in the upper 15 inches or so.  Various
parts of this Section will refer to this conceptualization.
    Two methods will be used to estimate the rate of  nutrient release from
the sediments to the water column.  The first makes use of the  sediment
gravity core samples taken during the course of the Chesapeake  Bay Program
(Hill and Conkwright 1981, Tyree et al. 1981, Bricker1 1981) as well as
those from the U.S. Geological Survey's Potomac River Project.   The  second
approach uses measurements of nutrient release into domes placed on  the
bottom as part of the Bay Program's nutrient dynamics study. These  two
methods will be used to compute ranges of potential nitrogen and phosphorus
flux.

PORE WATER STUDIES

    The lower limit for potential nutrient flux out of the sediment  is
estimated from the pore water studies; other factors, like bioturbation, may
^Personal Communication:  "Benthic Flux of Nutrients from Pore Water
  Studies," O.P. Bricker, Northeast Research,  U.S.  Geological Survey,
  Reston, VA, October,  1981.
                                   212

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       OVERLYING  WATER COLUMN

                                      ORGANIC FLUFF
                                        COMPACTED SURFACE
                                              LAYER
                                         COMPACTED ANOXIC
                                               LAYER
      ปJ.ซซJ WET-?

Figure V.
Conceptual diagram of estuarinซ sediment column.
                              213
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increase the actual nutrient flux over that described by pore water study.
Over 100 cores taken in the main Bay were analyzed for nutrient content.
The rates of potential nutrient diffusion out of the sediment were then
calculated for each CBP segment (see Figure V.I) based on the concentration
gradients in the sediment, the porosity of the sediment, and a
characteristic coefficient for molecular diffusion determined by ion
activity and the diffusing characteristics of the molecules.  The results
appear in Table V.I.  Nitrogen is released primarily as ammonium at
calculated rates of 0.5 to 8.8 millionth of a pound of nitrogen per square
foot per day.  The winter values are the arithmetic mean of values for the
other seasons, since no cores were taken in winter.  This information was
then extrapolated to the entire segment by multiplying the values in Table
V.I by the area of the Bay bottom in each segment composed of more than 50
percent organically-enriched mud (functionally, areas that have less than
50 percent sand).  The total daily potential release per segment was then
multiplied by the number of days per season to obtain the seasonal input to
each segment from the sediments as shown in Table V.2.  The total nitrogen
and phosphorus input from the sediments for each season appears in the
right hand column, and the total annual input for each segment appears at
the bottom of Table V.2.  The minimum potential annual inputs from the
sediment are 32.2 million pounds (1045.9 x 10^2 micro moles) of nitrogen
and 7.44 million pounds (100 x 1Q12 micro moles) of phosphorus.


TABLE V.I. POTENTIAL NITROGEN AND PHOSPHORUS UNIT AREA DIFFUSION FROM
           SEDIMENT PORE WATERS (UNITS ARE 10~6 POUNDS PER SQUARE FOOT PER
           DAY AS N OR P)

Segment
Spring
NH4+
P04-3
Summer
NH4+
P04-3
Fall
NH4+
P04-3
Winter(2)
NH4+
P04~3
CB-1

4.5
0.006

1.4
0.55d-

6.3
0.082

4.1
0.21
CB-2

0.5
0.27

1.8
> 0.43

1.4
0.095

1.3
0.27
CB-3

1.6
0.55

3.5
0.77

1.6
0.78

2.2
0.70
CB-4

5.2
1.1

5.0
0.53

1.3
1.5

3.8
1.0
CB-5

3.7
1.4

3.5
0.85

3.7
0.84

3.6
1.0
CB-6 CB-7 CB-8

2.8(D 1.0 2.8(1)
0.58(1) 0.21 0.58(D

3.2(D 4.3 3.2(D
o.io d)o.68 0.55(1)

3.6 8.8 2.3
0.18 0.14 0.16

3.21 4.7 2.8
0.29 0.35 0.43

       calculated as mean of other measurements taken is same season
 (across columns)
^Winter values calculated as mean for other seasons in each segment (down
 columns) because no winter data were taken.
                                   214

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TABLE V.2,  POTENTIAL NITROGEN AND PHOSPHORUS MASS DIFFUSION FROM SEDIMENT PORE
           WATERS FOR EACH SEGMENT  (UNITS ARE THOUSANDS OF POUNDS N OR P)

Segmentd)cB-2 CB-3 CB-4
j>prj.ng
NH4+
P04-3
Summer
NH4 +
P04~3
Fall
NV
P04™3
Winter
NH4 +
P04~3
Total Annual
NH4+
P04-3

80
41

283
68

222
14

191
41

776
164

647
211

1355
300

616
300

862
266

3480
1077

2710
559

2618
280

647
750

1940
518

7915
2107
CB-5

2279
818

2156
518

2279
505

2187
614

8901
2455
CB-6

770
164

893
27

986
48

862
818

3511
1057
CB-7 CB-8 Total Bay

400
89

1724
280

3511
55

1848
136

7483
560

43
7

22
7

37
3

43
7

145
24

6929
1889

9051
1480

8298
1675

7933
2400

32211
7444

(1)
   No values are indicated for segment CB-1 because no substantial area in
    that segment is composed of organically-enriched mud (less than 50 percent
    sand).
    On a seasonal basis, ammonium and phosphorus behave differently.
Ammonium is released year-round, regardless of whether the overlying  water
and compacted surface layer are oxygenated or anoxic (Taft 1982).
Phosphate, however, seems to be trapped by the compacted surface  layer when
it is oxygenated, and released rapidly when it becomes anoxic. Therefore,
phosphate release by pore diffusion should be most significant during
summer in regions of the Bay where the overlying water is anoxic.
Moreover, release should be a two-step event.  In step one, a large mass of
phosphorus, approximately equivalent to that which has accumulated in the
compacted surface layer during the previous nine months of oxygenated
conditions, is released rather quickly.  In step two, diffusion out of the
pore water continues at a slower rate, governed by concentration  gradients
and sediment characteristics, for the period of anoxia in the deep water.
    This concept can be tested by calculating the amount of phosphate that
would be trapped in the compacted surface layer during fall,  winter,  and
spring within the bottom region subjected to anoxia.  If this amount  of
phosphate were released at once into the volume of anoxic water,  it would
produce a phosphate concentration of 0.22 mg/L.  The observed phosphate
concentration shortly after the onset of deep water anoxia is about 0.124
                                   215
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mg/L (Taft 1982, Figure 5).  So our estimate exceeds, but is reasonably
close, to the observed values.  This result suggests that the concept is
basically correct, but that the system is not operating as a simple on-off
release mechanism.  Also, our calculatioan does not account for transport
out of the deep water to the surface layer, which does occur and would make
the observed values less than the calculated ones.
    In light of this behavior, and for the purpose of the seasonal
comparison of various phosphorus sources made in Section VIII,  the
assumption that the calculated annual flux of phosphorus from the pore
waters is released in the summer months appears to be reasonably well
supported.

DOME STUDIES

    Direct measurements of nutrient release from the sediments were made
with diver-installed domes in five locations in the main portion of the Bay
during August 1980 and May 1981.  The dome technique measures both
diffusion of nutrients (primarily ammonium since the domes were placed in
oxygenated bottom water) and remineralization on the sediment surface.  It
could also include nutrient release caused by burrowing animals if they
were covered by the dome.  Thus dome measurements give the upper limit for
potential nutrient release from the sediments.
    The dome results appear in Table V.3.  The spring values for both
nutrients are less than the summer values with phosphate flux being zero in
all but the northern most segment.  Although the compacted surface layer
was oxygenated, phosphate release was observed in summer but not in
spring.  This result suggests that diffusion is blocked by, and
remineralization is minimal in, the compacted surface layer and the organic
fluff layer during spring.  The latter may be due to low temperatures and
correspondingly low biological activity.  Both nutrients show marked flux
rates in summer reflecting increased biological activity in the surface
layers probably stimulated by warmer temperatures.
    The magnitude of nutrient remineralization in the two surface layers
can be obtained as the dome release minus the calculated diffusion from
pore water.  With the use of the data in Tables V.I and V.3,
remineralization in the surface-sediment layers accounts for 80 to 90
percent of the nitrogen release and for 30 to 90 percent of the phosphorus
release in summer (except for segment CB-3, which has a lower dome rate
than diffusion rate).  For purposes of this analysis, we consider that the
processes by which nutrients are remineralized on the sediment surface are
similar to those operating in the water column.  Sorption of remineralized
nutrients onto sediment particles could occur, but would not influence our
conclusions, because the dome flux rates were determined from measured
nutrient concentration changes.
                                  216

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TABLE V.3.   NUTRIENT RELEASE FROM THE SEDIMENTS MEASURED UNDER DOMES
            (UNITS ARE 10-6 POUNDS PER SQUARE FOOT PER DAY)

Segment
Spring
NH4+
P04-3
Summer
ซV
P04~3
CB-2 CB-3 CB-4 CB-5 CB-6 CB-7 CB-8

3.3 4.1 4.2 5.5 5.5 5.5 5.5
0.5 0 0 0 0 00
12 7.0 46 18 18 18 18
0.6 0.5 6.1 1.5 1.5 1.5 1.5

TABLE V.4.
NUTRIENT RELEASE IN EACH SEGMENT CALCULATED FROM DOME STUDIES
(UNITS ARE THOUSANDS OF POUNDS)

Segment
Spring
NH4 +
P04-3
Summer
P04~3
CB-2 CB-3 CB-4 CB-5 CB-6 CB-7 CB-8 Total Bay

524 1602 2187 3357 1509 2218 92 11489
68 0 00000 68
1910 2741 23900 11026 4959 7300 308 52144
95 177 3137 955 409 614 20 5407

SUMMARY
    The upper and lower limits for nutrient release from the sediments have
been established for the main portion of Chesapeake Bay.  The lower limits,
from diffusion calculations (Table V.2) , are about 32 million pounds of
nitrogen (as ammonium) and 7.4 million pounds of phosphorus (as phosphate)
per year.  The upper limits can be estimated from the spring and summer
dome studies (Table V.4) by multiplying the spring values by three, to
account for winter and fall, and adding the product to the summer values.
The result is 86.6 million pounds of nitrogen and 5.6 million pounds of
phosphorus.  The difference in the nitrogen values (54.6 million pounds)
represents regeneration in the unconsolidated sediment layer.  The
similarity of values for phosphorus suggests suppression of diffusive flux
and dominance of regeneration in the unconsolidated layer during
experimental measurements.  There is clearly a need for more field studies
on sediment processes.
    The relationship between benthic and other nutrient sources is shown in
Chapter VIII.  For example, during the summer the bottom is the major
source of ammonium and orthophosphorus (Table VIII.4b).
                                  217
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                                  SECTION VI

               NUTRIENT  FLUXES AT THE MOUTH OF CHESAPEAKE  BAY
    Since Chesapeake Bay receives ocean water at its mouth,  it also
receives nutrients from the ocean.  However,  it is not clear whether there
is net gain or loss of nutrients at the ocean boundary.  Nutrient transport
at the mouth is dependent on the direction and magnitude of  water flow,  and
on the nutrient concentrations in the water.   The long term  net flow is  out
of the Bay and is equal to the riverflow minus evaporation,  plus
precipitation input.  However, over any short time interval, meteorological
conditions can drive water into or out of the Bay continually for several
days at a time.  These short term variations  make it difficult to calculate
long term nutrient transport.
    Calculations are also complicated by the  structure of water flow at  the
mouth.  Within the Bay, the fresher, lighter  river water overlays the
saltier, heavier ocean water.  At the mouth,  however, the basin geometry
and the earth's rotation interact so that the ocean water inflow often
occurs at all depths on the north side with outflow on the south side of
the mouth.  Thus, the two-layer structure is  side by side rather than top
and bottom.
    As part of the Chesapeake Bay Program, an intensive study of the mouth
region was made in July 1980.  Current measuring devices were deployed at
five locations across the mouth for 38 days.   Nutrient measurements were
made at each current meter location for eight consecutive days during the
deployment.
    When the current meter data are averaged  over the 38 days beginning
June 23, 1980, the net flow, less tidal currents, is obtained.  Figure VI.1
shows net flow along the bottom into the Bay  on both the south (left) and
north side.  (Positive velocity equals inflow.)  Net outflow occurred at
the surface all across the mouth and from the surface to the bottom near
the middle of the mouth.  These results differ somewhat from the flow
structure expected from previous work (Boicourt, in progress), but we will
use them for flux calculations, because nutrient data were collected
concurrently with the flow measurements.
    The nutrient fluxes were calculated from nutrient concentrations
measured within isotachs shown in Figure VI.1.  The measured concentrations
were integrated over the area between isotachs to give nutrient fluxes for
each range of current velocity.  These values were then summed to give
fluxes into and out of the Bay.
    If the net water fluxes are multiplied by nutrient concentrations, the
nutrient fluxes are obtained.  Table VI.1 shows the nutrient fluxes
calculated in this way.  The net fluxes of organic carbon and total
nitrogen were out of the Bay, whereas total phosphorus and suspended solids
fluxes were into the Bay for this period.  For the reasons mentioned above,
it is difficult to extrapolate this information to seasonal  or annual
fluxes, but a comparison with another kind of information can be made.
Table VI.2 shows the fluxes calculated from a very simple box model
approach (Taft et al. 1978), using unpublished data collected during
several periods in 1975-1976.  It can be seen that the flux  of particulate
nutrients for 1975-1976 was generally out of  the Bay.  The values for the
                                  218

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particles alone are much higher than both particle and total fluxes for
July 1980.  Comparing the suspended solids flux for July 1980 of +55,000
Ibs./day (+290 g-s"1) (Table VI.I) with the total' particulate organic
fluxes for August 1975 and 1976 (Table VI.2) shows a difference by about a
factor of ten.  The net flux of suspended solids is into the Bay,  whereas
the net particulate organic flux is out of the Bay.  This could be
reasonably explained if incoming material were enriched with inorganic
particles, and if outgoing material were enriched with organic particles
such as phytoplankton.
    Assume that the values in Table VI.2 are too high, because they are
derived from measurements made ten miles inside the Bay rather than at the
mouth.  Further assume, however, that the net flux is out and the relative
differences among the seasons represented in Table VI.2 are approximately
correct.  That is, the spring flux of organic carbon is higher than the
summer flux by about 1.5 times.  We can than construct an approximate flux
of total carbon out of the Bay by multiplying the total organic carbon flux
of -695,250 Ibs./day (-3650 g's'^-d) by 1.5 for spring.  The winter flux
is likewise taken as 1.5 times -695,250 Ibs./day (-3650 g's"1).  We can
assume the fall flux equals the summer values for lack of better
information.

The average annual flux then is:

                  Summer      -695,250 Ibs./day (-3650 g's"1)
                  Fall        -695,250 Ibs./day (-3650 g's"1)
                  Winter      -1,040,250 Ibs./day (-5475 g's"1)
                  Spring      -1,040,250 Ibs./day (-5475 g's"1)
                       TOTAL  -3,471,000 Ibs./day (-18,250 g's^)

                          AVERAGE  -  867,750 Ibs./day (- 4,562 g's"1)

Thus, the net flow of organic carbon out of the Bay is estimated to be
867,750 Ibs./day (4562 g's"1) for a full year or 316 million pounds per
year (1440x10^  g-yr"1).  If we then apply the same reasoning to the
other nutrients, we calculate the net outflow of nitrogen to be 3  million
pounds per year (12.6x10^ g'yr"1), and the net inflow of phosphorus
to be 1.7 million pounds per year (7.9x10^ g'yr"1).
    The difference in sign between the suspended solids and total
phosphorus fluxes, on the one hand, and the remaining nutrient fluxes,  on
the other, is interesting and can be explained.  The suspended solids data
contain both organic and inorganic particles.  Since the net flux  of
organic particles seems to be out of the Bay, the observed inflow  must  be
due to inorganic sediments entering the Bay from the ocean.  This
interpretation is consistent with ideas put forth by Schubel concerning net
sediment transport into Chesapeake Bay from the ocean.  The net inflow  of
phosphorus from the ocean to the Bay is consistent with the notion that
nitrogen is limiting to phytoplankton biomass in the ocean, so that
phosphorus may be present in excess in the ocean water entering the Bay.
It may also be sorbed onto suspended sediment particles entering the Bay.
                                   220

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    It should be clear to the reader from this summary of the available
data that our understanding of transport through the Bay mouth is still
quite rudimentary.'  The calculations made here should be used to form
additional scientific questions focused on improving insight into this
important aspect of  nutrient dynamics in Chesapeake Bay.
    At any rate, the net flux of nutrients to the Bay from the ocean
appears to be small  enough related to the other sources that it can be
ignored for calculating nutrient sources to the Bay system without the
introduction of a major error.  Although minor on a Bay-wide scale,
however, oceanic flux of nutrients may be of local importance.
TABLE VI. 1.  NUTRIENT FLUXES ACROSS THE MOUTH OF CHESAPEAKE BAY IN JULY
             1980  (UNITS ARE THOUSANDS OF POUNDS PER DAY)
             POSITIVE VALUES INDICATE FLUX INTO THE BAY


Total Organic Carbon
Total Nitrogen
Total Phosphorus
Total Suspended Solids
Particulate Organic Carbon
Particulate Organic Nitrogen
Flux In
+ 1170
+ 184
+ 14
+ 3,969
+ 247
+ 33
Flux Out
1846
190
13
- 3,914
348
49
Net Flux
676
6
+ 1
+ 55
101
16

TABLE VI.2.  FLUXES OF PARTICULATE MATERIAL AT THE BAY MOUTH CALCULATED
             WITH A BOX MODEL  (UNITS ARE THOUSANDS OF POUNDS PER DAY)
             POSITIVE IS INTO THE BAY (1)

Time
February 1975
May 1975
August 1975
February 1976
April 1976
August 1976
C
+1890
- 874
- 461
-6016
- 446
- 373
N
+ 265
- 122
- 76
- 67
- 63
- 60
P
+13
-6
-4
-3
-3
-3
Chi a
+4
-7
-0.6
-1.4
-1.1
-1.1
Total
+ 2,168
- 1,002
541
- 6,086
512
- 436

^"•^Information in table from unpublished data (Taft).   Box model  concept
   to be published in Spring 1982.
                                  221
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    The minimal flux of nutrients out of the Bay has profound implications
for management.  Nearly all of the materials that enter the Bay remain
there; nutrients trickle out of the Bay mouth at a very slow rate.   Thus,
even if nutrient loads were dramatically reduced, Bay-wide improvement of
water quality would be very slow.  It would take many years for the
accumulated mass of nutrients to leave the system.
                                 222

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                                 SECTION VII

                   PRIMARY PRODUCTIVITY IN CHESAPEAKE BAY
                                                I
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                                                I
    Primary productivity is the rate of organic carbon production from
inorganic carbon by plants and constitutes an important source of nutrition
to Chesapeake Bay.  For purposes of this Section,  only phytoplankton               M
productivity is considered.  The productivity by submerged aquatic                 0
vegetation (SAV) is covered in the synthesis paper on SAV (part III).
    The basic data set used here for primary productivity calculations was         *
collected on bi-monthly cruises during 1972 and 1973 (Taylor 1982).   Values        I
measured at single stations have been averaged over the regions shown on
the map in Figure VII. 1.  Further, the measurements have been integrated
over various depths of euphotic zone according to location in the Bay.             •
    The single station measurements and multiplying factors for surface            •
area and euphotic zone depth are shown in Table VII. 1.  As one might expect
productivity is generally greater in summer than in winter by factors of           1|
five to 20, depending on region, as well as on higher light levels and             Jj
temperatures in the summer.  Also, annual average productivity per square
foot is higher in the upper Bay than lower, because of the greater                 ^
availability of nutrients.  However, owing to the proportionally greater           M
area of the lower Bay, total productivity is greater in the lower Bay              ^
regions.  Productivity is about equally divided between the states with 30
x 108 Ibs. C/yr (14 x 1011 gC/yr) in Maryland (Table VII. 1, Regions                 •
I-VII) and 32 x 108 Ibs. C/yr (15 x 1011 gC/yr) in Virginia (Regions               J
VIII-IX) for a total of 62 x 108 Ibs. C/yr. (29 x 1011 gC/yr).
    The amount of nitrogen and phosphorus required to support this amount          •
of productivity can be estimated from the ratio of C:N:P in phytoplankton.         •
This ratio is commonly taken to be 106:16:1 by atoms (Redfield ratio).             ^
    The nitrogen requirement estimated from the Redfield ratio is 11 x
10 8 Ibs. N/yr. (5.2 x 10* 1 gN/yr) , and the phosphorus requirement is               W
1.5 x 108 Ibs. P/yr. (0.7 x 10*1 gP/yr) .  These requirements are met,               ™
in part by inputs from rivers, the atmosphere, point sources, and the
sediments and, in part, by recycling of organic materials into inorganic           It
nutrient forms.  Table VII. 2 shows the annual total nitrogen and phosphorus        ฃ
inputs compared with the amount required to support the observed
phytoplankton primary productivity.  The annual inputs are 302.8 million           •
pounds of nitrogen and 30.2 million pounds of phosphorus.  Accounting for          •
the estimated net flux at the mouth and the nutrient "stored" in the water
column yields 380.0 million pounds of nitrogen and 38.4 million pounds of
phosphorus either in the Bay or entering it annually.  The requirements to         •
support phytoplankton primary productivity are, as a minimum, three  times          •ป
greater than the supply for nitrogen and four times greater for
phosphorus.  This additional amount of nutrient must be supplied by                 •
recycling in the water through the mechanisms discussed in Chapter 2 of            J|
this part, including grazing and decomposition of organic matter.
    The seasonal relationships between phytoplankton productivity (Table           —
VII. 3) and nutrient inputs is shown in Tables VII. 4 through VII. 7.  In the         •
winter (Table VII. 4), nitrogen entering the Bay potentially supports about         ™
seven-tenths of the productivity in winter.  This is shown by dividing
nutrients in, or entering the Bay, by those required to support primary            fl|
223
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               CHESAPEAKE BAY
Figure VII.1.
Map of Chesapeake Bay showing regions  in which primary
productivity measurements  have been  averaged.
                                 224

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productivity.  Nitrogen supports about one-half of the  productivity in            1^
spring (Table VII.5), about one-tenth in summer (Table  VII.6),  and  about           Q
one-fifth in the fall (Table VII.7).   Incoming phosphorus  potentially
supports about two-fifths of the productivity in winter, about  one-quarter         A
in spring, about one-fifth in summer, and one-eighth in the  fall.                  M
Nutrients entering and leaving the system as migrating  finfish  could not  be
evaluated.  The nutrients in fish caught, amounts to about eight million
pounds N and one million pounds P annually,  but these values are not              V
included in the Tables.                                                           w
    The nutrient estimates were made  assuming that all  of  the inputs are
thoroughly mixed in the Bay, an incorrect assumption.  Most  nutrients are         •
probably retained in the tributaries  for a considerable length  of  time.            A
Moreover, most of the incoming nutrients seem to enter  the sediments rather
quickly.  Note also that the estimates of production are only for  the Bay         ^
proper; the tributaries have not been included.                                   •
                                  225
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TABLE VII.1.  PRIMARY PRODUCTIVITY MEASUREMENTS AND FACTORS USED TO
              CALCULATE ANNUAL AVERAGE PRODUCTIVITY FOR CHESAPEAKE BAY
              DEVELOPED FROM DATA BY FLEMER 1970 AND TAYLORl 1973

2/73
I
II
III
IV
V
VI
VII
VIII
IX
4/73
1.8 x 10-6
374
344
611
481
339
320
-
315
677
5049
1366
891
891
891
713

6/73
pounds
6237
2257
1722
1129
1426
1960
1188
1010
8/73
C/ft2
6653
6118
3089
4752
2317
2851
2079
1485
10/73
/day
2376
2257
1541
1188
1960
1426
1307
1485
12/73

386
1960
1485
499
653
594
1307
653
(
(
Av.
6273
2784
2998
1636
1490
1264
1340
1319
990
S
U
R
F
A
C
E
A
R
E
A
106)
ft2) (
—
3809
2066
5853
3680
7371
4186
14246
22284
E
U
P
H
0
T
I D
C E
P
Z T
0 H
N
E
:ft.;
—
15
15
15
18
18
20
20
24
E
U
P
H
0
T V
I 0
C L
U
Z M
0 E
N
E
(109)
) (ft3)
1.0
57
31
88
66
133
84
285
535
Total
A
N
N
U P
A R
L 0
D
A U
V C
E T
R I
A 0
G N
E
do8)
(lbs-C)

5.7
3.4
5.3
3.6
6.1
4.1
13.7
19.3
62.2

  Personal Communication:  "Primary Production Data for the Chesapeake Bay,
  1973," W.R. Taylor, Chesapeake Bay Institute, Shady Side, MD, January, 1982.
                                  226

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TABLE VII.2.  RELATION BETWEEN ANNUAL PLANKTON PRODUCTIVITY AND
              ANNUAL NUTRIENT INPUTS



Required to support' 1'
Primary Productivity
Annual input from '2)
Atmosphere
Fluvial sources
Point sources
Sediments
Total inputs
Net Flux at the mouth ^3^
Net inputs
Total Nutrient in the water'^'
Nutrients in or entering
the Bay annually
Nutrients recycled' 5)
% Productivity supported by
available nutrients
% Productivity supported by
recycling
Total N
Millions

1100

40.4
178.1
52.1
32.2
302.8
- 3.0
299.8
80.2
380.0

720.0
34.6%

65.5%

Total P
of Pounds

150

1.64
10.3
10.8
7.44
30.2
+ 1.7
31.9
6.5
38.4

111.6
25.6%

74.4%


(^Calculated from Table VII.1

<2)From Table VIII.1

^3^From Chapter VI

(^Estimated as the product of average concentrations of readily-
   available algal nutrients and water volume.  The nutrient forms
   are:  available nitrogen = nitrate and ammonium
         available phosphorus = soluble reactive phosphorus

'•''Inorganic nutrient forms regenerated from organic forms by
   grazing, decomposition, and other processes.
                                   227
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TABLE VII. 3. SEASONAL PRIMARY PRODUCTIVITY IN CHESAPEAKE BAY

Season % Annual productivity
Spring 20
Summer 45
Fall 25
Winter 10



TABLE VII. 4. RELATION BETWEEN WINTER
NUTRIENT INPUTS





Required to support
Primary Productivity
Input from
Atmosphere
Fluvial sources
Point sources
Sediments
Total inputs
Net Flux at the mouth
Net inputs
Total Nutrient in the water
Nutrients in or entering
the Bay

Nutrients recycled
% Productivity potentially supported
by available nutrients
% Productivity supported by
recycling


108 pounds C/ season
12.4
28.0
15.6
6.2



PHYTOPLANKTON PRODUCTIVITY AND




Total N Total P<1)
Millions of Pounds


110 15

6.2 0.2
51.4 3.0
12.8 2.7
7.9
78.3 5.9
- 0.9 + 0.3
77.4 6.2
18.2 0.5
95.6 6.7


14.4 8.3
86.9 44.7%
13.1% 55.3%

(1) Source is Tables VII. 2 and VII. 3 for Total N and Total P.

228



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TABLE VI1.5.  RELATION BETWEEN  SPRING PHYTOPLANKTON PRODUCTIVITY AND
              NUTRIENT INPUTS


Required to support
Primary Productivity
Input from
Atmosphere
Fluvial sources
Point sources
Sediments
Total inputs
Net Flux at the mouth
Net inputs
Total Nutrient in the water
Nutrients in or entering
the Bay
Nutrients recycled
% Productivity supported by
available nutrients
% Productivity supported by
recycling
Total N
Millions of
220
16.2
72.2
13.1
6.9
108.4
- 0.9
107.5
18.2
125.7
94.3
57.1%
42.9%
Total P
Pounds
30
0.51
4.21
2.72

7.4
+ 0.3
7.7
0.5
8.2
21.8
27.3%
72.7%

                                    229
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TABLE VII.6.   RELATION BETWEEN SUMMER PHYTOPLANKTON PRODUCTIVITY AND
              NUTRIENT INPUTS



Required to support
Primary Productivity
Input from
Atmosphere
Fluvial sources
Point sources
Sediments
Total inputs
Net Flux at the mouth
Net inputs
Total Nutrient in the water
Nutrients in or entering
the Bay
Nutrients recycled
% Productivity supported by
available nutrients
% Productivity supported by
recycling
Total N
Millions

497

12.2
25.1
13.1
9.1
59.5
- 0.6
58.9
22.8
81.7

415.3
16.4%

83.6%

Total P
of Pounds

68

0.6
1.4
2.7
7.4
12.1
+ 0.2
12.3
5.0
17.3

50.7
25.4%

74.6%


                                  230

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TABLE VII.7.  RELATION BETWEEN FALL PHYTOPLANKTON PRODUCTIVITY AND
              NUTRIENT INPUTS


Required to support
Primary Productivity
Input from
Atmosphere
Fluvial sources
Point sources
Sediments
Total inputs
Net Flux at the mouth
Net inputs
Total Nutrient in the water
Nutrients in or entering
the Bay
Nutrients recycled
% Productivity supported by
available nutrients
% Productivity supported by
recycling
Total N
Millions
277
5.9
27.9
13.0
8.3
55.1
- 0.6
54.5
21.0
75.5
201.5
27.3%
72.7%
Total P
of Pounds
38
0.3
1.5
2.7

4.5
+ 0.2
4.7
0.5
5.2
32.8
13.7%
86.3%

                                   231
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                                  SECTION VIII

           SUMMARY AND CONCLUSIONS:  THE MANAGEMENT QUESTIONS ANSWERED


    This section is divided into two sub-sections.   The first synthesizes the
results of Chapters II through VI, presenting annual and seasonal loadings
from all sources, and computing the total Bay-wide  nutrient and sediment input
budgets.  The second half of the chapter contains a restatement of the
pertinent Management Questions listed in the Introduction (Section I).
Following each question is a statement of answers that draws upon the data
presented here as well as upon other sources that are as complete, technically
correct, and editorially succinct as possible within the limitations of the
authors capabilities.

ANNUAL AND SEASONAL LOADINGS OF NUTRIENTS TO THE BAY FROM MAJOR SOURCES

    The nutrient loading estimates from each source have been accumulated and,
in some cases reformatted to develop estimates of the total nutrient inputs to
the tidal Chesapeake Bay system.  The results have  been depicted in terms of
the total mass flux into the tidal system for the year and each of the
seasons.  As previously stated, the months included in each season are as
follows:
    WINTER:  December, January, February  (90 days)
    SPRING:  March,  April, May            (92 days)
    SUMMER:  June,  July, August           (92 days)
    FALL:    September,  October, November (91 days)
    ANNUAL:  December - November          (365 days)
    The sources included in the synthesis are Atmospheric, Fluvial, Point
(below fall line),  and Bottom.  As mentioned at the end of Chapter VI, the
ocean has been eliminated from consideration as a source for the purposes of
this paper because  the net flux was insignificant.   The annual and seasonal
nutrient input budgets are presented in Table VIII.l(a) through VIII.5(a).
    The fraction that each source represents of the annual (or seasonal) total
for each constituent has been computed, expressed as a percentage, and
included as the "b"  section of each Table [Tables VIII.l(b) through VIII.5(b)].

TABLE VIII.l(a).  AVERAGE ANNUAL NUTRIENT AND FLUVIAL SEDIMENT INPUT TO THE
                 WATER COLUMN OF THE TIDAL CHESAPEAKE BAY SYSTEM
                 (MILLIONS OF POUNDS)

Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sediment (SED)
Atmospheric
Sources
40.4
14.5
8.91
25.9
1.64
0.40

Fluvial
Sources
178.1
111.5
9.06
58.6
10.3
3.24
6630.
Point
Sources
52.1
17.3
27.2
34.2
10.8
6.85

Benthic
Sources
32.2

32.2
32.2
7.44
7.44

Total

302.8
143.3
77.4
150.9
30.2
17.9
6630.

                                      232

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TABLE VIII.l(b).  PERCENTAGES OF ANNUAL NUTRIENT LOADINGS FROM VARIOUS SOURCES


Constituent
Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Atmospheric
Sources
13.3
10.1
11.5
17.2
5.4
2.2
Fluvial
Sources
58.8
77.8
11.7
38.8
34.1
18.1
Point
Sources
17.2
12.1
35.2
22.7
35.8
38.2
Benthic
Sources
10.6
41.6
21.3
24.7
41.5


Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sediment (SED)
Atmospheric
Sources
6.16
2.95
2.06
3.21
0.21
0.09

Fluvial
Sources
51.4
32.2
2.62
16.8
2.97
0.933
1830.
Point
Sources
12.8
4.26
6.70
8.44
2.67
1.69

Benthic
Sources
7.93

7.93
7.93



Total

78.3
39.4
19.3
36.4
5.85
2.71
1830.

TABLE VIII.2(b). PERCENTAGES OF WINTER NUTRIENT LOADINGS FROM VARIOUS SOURCES


Constituent Atmospheric

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sources
7.9
7.5
10.7
8.8
3.6
3.3
Fluvial
Sources
65.7
81.7
13.6
46.1
50.8
34.4
Point
Sources
16.3
10.8
34.7
23.2
45.6
62.3
Benthic
Sources
10.1

41.1
21.8



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TABLE VIII.2(a).  AVERAGE WINTER NUTRIENT AND FLUVIAL SEDIMENT INPUT TO THE        *
                 WATER COLUMN OF THE TIDAL CHESAPEAKE BAY SYSTEM

                 (MILLIONS OF POUNDS)                                             •
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TABLE VIII.3(a).  AVERAGE SPRING NUTRIENT AND FLUVIAL SEDIMENT INPUT TO THE

                 WATER COLUMN OF THE TIDAL CHESAPEAKE BAY SYSTEM

                 (MILLIONS OF POUNDS)

Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sediment (SED)
Atmospheric
Sources
16.2
4.70
3.45
11.5
0.51
0.10

Fluvial
Sources
72.2
45.3
3.73
23.6
4.29
1.28
2870.
Point
Sources
13.1
4.36
6.85
8.62
2.72
1.73

Benthic
Sources
6.93

6.93
6.93



Total

108.
54.
21.
50.
7.
3.
2870.

4
4
0
6
52
11


TABLE VIII. 3 (b). PERCENTAGES OF SPRING NUTRIENT


Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)


Atmospheric
Sources
14.9
8.6
16.5
22.7
6.8
3.2
LOADINGS


Fluvial
Sources
66.6
83.3
17.8
46.6
57.0
41.2
FROM VARIOUS SOURCES


Point
Sources
12.1
8.0
32.7
17.0
36.2
55.6


Benthic
Sources
6.4

33.1
13.7






















TABLE VIII.4(a).  AVERAGE SUMMER NUTRIENT AND FLUVIAL SEDIMENT INPUT TO THE
                 WATER COLUMN OF THE TIDAL CHESAPEAKE BAY SYSTEM
                 (MILLIONS OF POUNDS)

Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sediment (SED)
Atmospheric
Sources
12.2
4.70
1.89
7.47
0.60
0.11

Fluvial
Sources
25.1
15.8
1.26
8.18
1.42
0.49
955.9
Point
Sources
13.1
4.36
6.85
8.62
2.72
1.73

Benthic
Sources
9.05

9.05
9.05
7.44
7.44

Total

59.5
24.9
19.05
33.4
12.2
9.77
955.9

                                     234

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TABLE VIII.4(b).  PERCENTAGES OF SUMMER NUTRIENT LOADINGS FROM VARIOUS SOURCES


Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Atmospheric
Sources
20.5
18.9
9.9
22.4
4.9
1.1
Fluvial
Sources
42.2
63.6
6.6
24.5
11.7
5.0
Point
Sources
22.0
17.5
36.0
25.8
22.3
17.7
Benthic
Sources
15.2

47.5
27.1
61.1
76.2

TABLE VIII.5(aX  AVERAGE FALL NUTRIENT AND FLUVIAL SEDIMENT INPUT TO THE WATER
                 COLUMN OF THE TIDAL CHESAPEAKE BAY SYSTEM
                 (MILLIONS OF POUNDS)

Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Sediment (SED)
Atmospheric
Sources
5.91
2.12
1.51
3.78
0.30
0.12

Fluvial
Sources
27.9
17.7
1.42
9.06
1.49
0.53
975.
Point
Sources
13.0
4.31
6.78
8.53
2.70
1.71

Benthic
Sources
8.30

8.30
8.30



Total

55.1
24.1
18.0
29.7
4.49
2.36
975.

TABLE VIII. 5 (b). PERCENTAGES OF FALL NUTRIENT LOADINGS FROM VARIOUS SOURCES

Constituent

Total Nitrogen-N (TN)
Nitrite + Nitrate Nitrogen-N (N023)
Ammonia Nitrogen-N (NH34)
Total Kjeldahl Nitrogen-N (TKN)
Total Phosphorous-P (TP)
Orthophosphorus-P (OP)
Atmospheric
Sources
10.7
8.8
8.4
12.7
6.7
5.1
Fluvial
Sources
50.6
73.4
7.9
30.5
33.2
22.5
Point
Sources
23.6
17.9
37.7
28.7
60.1
72.5
Benthic
Sources
15.1

46.1
27.9











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    The reader should be cautioned that the sum of the individual seasonal
totals (Tables VIII.2(a) - VIII.5(a)) will not always agree exactly with the       <•
annual totals shown in Table VIII.l(a).  The reason for this is that the           •
annual load shown for the fluvial sources column of Table VIII.l(a) represents
the results of the regression model equations applied in Section III for
annual loads that are developed independently of the individual seasonal           •
                                     235
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models.  The annual loads are not simply the sum of the four seasonal model
outputs, therefore, and any differences between the computations using the
annual model and the sum of the individual seasons are an artifact of the
regression analysis.  The difference between presented annual values and the
sum of the four seasons is usually less then one percent.
    Examination of the data presented in Tables VIII.l(a) through VIII.5(b)
reveals some interesting, if not new, information about the loading mechanisms
that effect the Bay system.  The need to look beyond annual loadings into the
seasonality of loading patterns is evident.   Shown below are the deviations
from the seasonal loadings for nitrogen and  phosphorous that would be
"expected" if the annual loads (Table VIII. 1) were distributed evenly into
seasons.
TABLE VIII.6.  SEASONAL DISTRIBUTION OF NUTRIENT LOADINGS


Nutrient
TN
TN
TN
TN
TP
TP
TP
TP

Season
Winter
Spring
Summer
Fall
Winter
Spring
Summer
Fall
"Expected"
Value
74.7
76.3
76.3
75.5
7.45
7.61
7.61
7.53
Actual
Value
78.3
108.4
59.5
55.1
5.85
7.52
12.2
4.49
Percent of
Expected Value
104.8
142.1
78.0
73.0
78.5
98.8
160.3
59.6

% Deviation
+4.8
+42.1
-22.0
-27.0
-21.5
-2.0
+60.3
-40.4

    In other words, the expected loads are defined as those that would be
computed by applying an average annual loading rate expressed as daily loads
(Ibs/day) to the number of days in each season.  These values are useful as a
device to elucidate the importance of seasonal considerations of nutrient
loading dynamics.
    An immediate point of interest when studying Table VIII.6 of seasonal
deviations is that while the spring freshet carries a large nitrogen and
phosphorous load, a disproportionately large amount of the annual nitrogen
budget is delivered [Table VIII.3(a) and VIII.3(b)].  The reason that
phosphorous appears to remain close to the "expected" value is because the
effect of the spring freshet load is offset by the very large pulse of
phosphorous (seven million pounds) released from the sediments during the
period of bottom-water anoxia in early summer [Table VIII.4(a)].  A secondary
reason for this effect is that the ratio of total nitrogen to total
phosphorous in runoff is in excess of three times greater then the TN:TP ratio
of the point source load.l  Point source loadings of total phosphorous are
usually double those in runoff in summer and fall [Table VIII.4(a) and
VIII.5(a)], about equal in the winter [Table VIII.2(a)], and about half as
  TN:TP for runoff varies from 17 to 19 while the TN:TP for point sources is
  4.8.
                                     236

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great as the runoff TP load during the spring [Table VIII.3(a)]  because of the     tt
effect of the freshet.  In contrast, nitrogen from runoff always exceeds that      B
from point sources with the greatest deviation occurring in the  spring [Table
VIII.3(a)] when the nonpoint source nitrogen flux is probably more than four       •
times greater than the point source nitrogen flux.  In summary,  the largest        •
portion of the annual nitrogen loading budget enters the tidal system during
the winter-spring period, and the largest portion of the annual  phosphorous
budget enters during the spring-summer period.  This seems  vto support Taft's       •
observation that biomass within the euphotic zone in the Bay is  most likely        9
controlled (limited) by phosphorous in the spring and nitrogen in the summer
(See Chapter 2 of this part).                                                      It
    The nitrogen being discharged from both fluvial and point sources is           ^
predominately nitrite-nitrate.  However,  a larger portion of the total
nitrogen load from point sources is in the ammonia phase than for nonpoint         M
sources [Table VIII.l(b)].  In fact, point sources discharge much more ammonia     I
than fluvial sources every season, even during the freshet  [Tables VIII.2(b)
to 5(b)].  This load of ammonia, plus the input from the bottom  would support
the hypothesis that nitrate is transported conservatively (without changes in      •
form) through the upper Bay in the spring because of phytoplankton preferences     •
for ammonia (see Chapter 2).  If phytoplankton growth in the upper Bay has
sufficient ammonia-nitrogen for support of the population then                     •
nitrate-nitrogen will transport to the lower Bay without being utilized.  With     •
large fluvial loads occurring in the late spring, we can expect  the lower Bay
to receive these loads in a form readily available for algal assimulation, a        _
condition which is apparent from field monitoring data.                             •

NUTRIENT BUDGETS

    With the information assembled in Tables VII.2 and VIII.1, it is possible       0
to construct annual budgets for nitrogen and phosphorus transport.  Such
budgets, of course, suffer from uncertainties in the data,  but are useful for       M
visualizing the relative importance of sources and sinks for nutrients.  The        •
greatest uncertainty in our budgets occurs in the exchange  between the Bay and
the ocean.  Since data are scanty, our estimates are based  on defendable, but
imperfect, assumptions.  The amount of nutrient loss to the sediments in each       •
budget was determined by subtracting the difference between the  sum of the          •
inputs and the sum of the outputs.  Therefore, it has an uncertainty equal to,
or greater than, the uncertainty in the ocean exchange estimate.  Even with         •
the uncertainties, the budgets reflect what happens in the  estuary:  It is          JP
filling with sediments; it is trapping nutrients.
    Figure VIII.1 depicts the annual nitrogen and phosphorus budgets for            ^
Chesapeake Bay.  Two important features,  as discussed above, are exchange at        I
the ocean boundary and the net amount of nutrient removal by sedimentation.
For both nutrients, the transport across the boundary with the ocean is
approximately balanced.  This means that most of the nitrogen and phosphorus,       •
entering from the land and the atmosphere, remain in the system.  Some              •
nutrient is stored in the water but, since water column concentrations do not
increase dramatically from one year to the next, most incoming nutrient must        •
go to the sediments during the annual cycle.  The sedimentation  values in           ฃ
Figure VIII.1 are net rates, indicating permanent burial of about 300 million
                                     237
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                                   Atmosphere
                                       (40)

River Transported .
Input (178) *
Direct Discharge k
(52) P
Nฃ Fixation
(0.025)



N20, NH3 Loss
(0.040)
T




Loss (85)^
Ocean
^ Input
(83)
                         Sedimentation
                            (300)
                                    Atmosphere
                                      (1.6)
                            lent
Sedimentation
    (31.9)
                              Benthic
                              Input
                               (32)
                                                       T
Benthic
Input
(7.4)
               A.
River Transported ^
(10.3) f
Direct Discharge fc
(10.8) '


Loss (5.81
Ocean
A Input
1 (7.6)
                                                                       B.
Figure VIII.1.  Annual (a)  nitrogen and (b)  phosphorus  budgets  for Chesapeake
                Bay.   (In millions  of pounds)
                                       238

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pounds of nitrogen and 31.9 million pounds of phosphorus annually.  About 10       •
percent of the nitrogen and 23 percent of the phosphorus is returned to the        fp
water column from the sediments.
    The nitrogen input to the Bay by nitrogen fixation is not well known, but      A
it should be small compared to other inputs since nitrogen fixation rates in       •
the water are vanishingly small.  We estimate 25,000 pounds per year net input
from marshes.  The nitrogen loss to the atmosphere as ^0 and NHo gas is           ^
also probably small.  Few measurements have been made from which we estimate       •
an annual loss of 40,000 pounds per year from the estuary.  We hope future         ™
research will refine these estimates.
    Neither budget accounts for nutrient gains or losses as fish, crabs, and       •
birds migrate through the system.  In the absolute sense, the numbers are no       ฃ
doubt large, but relative to the other inputs and losses, they should be
small.  By inspection, if all excess nutrients were leaving in the form of a       _
harvestable fishery, eutrophication would not be the problem it is becoming in     •
rhpsflnpflkp Hav.                                                                    ™
Chesapeake Bay.
                                     239
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    Management Questions and Answers

    Below and on the following pages are a restatement  of the nine  Management
Questions and the answers as could best be derived from the available
information.

1.  What is the atmospheric contribution to nutrient  input?

    The atmospheric nutrient contribution that enters directly upon tidal
waters is at least 40 million pounds of nitrogen and  1.6 million pounds of
phosphorous each year [Table VIII.l(a)].  This load constitutes about 13
percent of the annual nitrogen,  and five percent of the annual phosphorous
input budgets [Table VIII.l(b)].  Seasonally,  atmospheric sources may make up
as much as 20 percent of the seasonal total nitrogen  (winter) input and five
percent of the seasonal total phosphorous (summer) input and as little as
seven percent of the total nitrogen load and three percent of the total
phosphorous load in the winter and spring [Tables VIII.2(b) to VIII.5(b)].

2.  What percentage of the nutrients is from point sources?

    On an annual basis, about 20 to 25 percent of the total nitrogen load
entering tidal waters comes from point sources basin-wide [Table VIII.Kb)].
This percentage range would hold even if all of the point sources load
discharged above the Fall Line were transported directly to the tidal system
(a very conservative assumption since losses undoubtedly occur in transport,
especially during the summer)•  The proportions are relatively invariant
throughout the year, reaching the lower end of the range in the spring and the
upper end in the summer and fall.
    To make a reasonable estimate of the percentage of  the phosphorous load
deriving from point sources, some manipulations of the  riverine loading models
developed in Chapter III were performed.  Low flow values were chosen for  each
of the major tributaries^, and the total phosphorous  load expected  to occur
at these flows were computed.  This total flow (sum of  all three tributaries)
was about 9660 cubic feet per second.  Note from Table  IV.12(a) that the total
point source flow entering above the Fall Line is about 688 cfs.  The total
phosphorus load computed to be carried to the tidal system at a stream
discharge of 9660 cfsd is about 1950 Ibs./day or about  0.7 million  pounds  per
year.  If the extremely conservative assumption is made that all of this load
derives from point source discharges and is-summed with the 10.8 million
pounds of point source phosphorous discharged per year  below the Fall Line,
the total point source contribution of phosphorous is computed to be about 40
percent of the total annual phosphorous input budget  of around 11 million
pounds per day.  Seasonally, the point source contribution of phosphorous
makes up as much as 65 percent of the fall total phosphorus input budget and
as little as 25 percent of the summer total phosphorous input budget.
  The "daily discharge that is greater than or equal to the flows that occur
 10 percent of the time" was computed for each major tributary.   They are:
 Susquehanna, 6640 cfsd; Potomac,  1690 cfsd;  James,  1330 cfsd.
                                 240

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3.  What percentage of nutrients is from nonpoint sources and how do they vary
    over time?
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    To discuss nonpoint sources within the structure of this paper,  we define      ซ
three categories of diffuse sources.   They are:                                     I
    i)   Atmospheric contributions                                                 *
    ii)  Land runoff /base flow contributions
    iii) Benthic contributions                                                     •
    Categories i) and ii) are covered separately elsewhere in this Section         •
under the discussions of other Management Questions.  For the purpose of
answering this Management Question,  we define nonpoint sources as the sum of       •
land runoff and base flow (groundwater discharge) which is carried by fluvial      •
processes to the tidal Bay system.  Contributions from the coastal plain are
not considered.
    On an annual basis, the mean total nonpoint  source nitrogen loading is         •
about 50 to 55 percent of the total  input budget, or about 160 to 177 million      "
pounds of nitrogen per year [Tables  VIII. l(a) and VIII. l(b)], making this the
single largest external source of nitrogen loading to the Bay.  Seasonally,         •
the variation in the nonpoint source nitrogen loading is quite dramatic,           •
ranging from about 23-25 million pounds in the summer (36 - 39 percent of the
total source load) to around 69 - 71  million pounds in the spring (63 - 66         im
percent of the total spring nitrogen load) .  The dominant species of nonpoint      •
source nitrogen at the Fall Line is  always nitrite-nitrate, making up
consistently between 62 and 64 percent of the total nitrogen from this source.
    On an average annual basis, the  nonpoint source loading of phosphorous is      •
about 30 to 34 percent of the total  phosphorous  input budget, ranging from         ™
around 9 to 10 million pounds per year.  As much as 65 to 70 percent of this
load on an annual basis is in the suspended phase, meaning most of the
phosphorous is being carried to the  Bay associated with particulate matter and
therefore, not immediately available for phytoplankton utilization.
Seasonally, the nonpoint phosphorous contribution probably varies from about       K
1.2 to 1.4 million pounds (only about 10-11 percent of the summer total            •
phosphorous budget) in the summer to about 4 million pounds in the spring, or
55 percent of the total spring input budget of phosphorous from all sources.
The very low percentage of the load  eminating from fluvial sources in the          •
summer is mainly due to the dominant effect of benthic sources of phosphorous      •
released in that season.
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4.  What are the pollutant runoff rates for particular land uses?

    This is the only management question to be answered in the paper for which     ^
the source information upon which the answer is based is not contained within      •
the text.  The information upon which this answer is based may be found in the     *
EPA Chesapeake Bay Program Information Series Nutrient Summary 3:  "Assessment
of Nonpoint Source Discharge to Chesapeake Bay" (unpublished) .  The data           •
presented in that report are the results of a preliminary analysis of the data     w
from the Chesapeake Bay Program Intensive Watershed Studies (IWS).
    The analysis performed on the data used the volume-weighted mean               tt
concentrations of storm event runoff, computed for the CBP studies (Hartigan,      M
1981) along with some typical expected average annual runoff volumes for
various land use/soil texture combinations, to generate generalized annual         ^
pollutant loadings for various classes of land use.  These data are presented      •
                                  241
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in Table VIII.6.  Although the analysis,  in its preliminary state,  necessarily
produced overlapping ranges of runoff loading rates among land uses,  the data
in Table VIII.6 allow us to assign order  of magnitude rankings for  the land
uses studied by areal loading rate.  The  generalized rankings are shown in
Table VIII.7.
    In all cases, the highest unit area loading rates were generally  exhibited
by cropland sites and the lowest by forest sites.
(N.B. The rankings shown in Table VIII.7  are a very broad generalization!)
TABLE VIII. 7,
CONCENTRATION, MG/L (TOP LINE), AND LOADING RATES, LBS/AC/YR
(BOTTOM LINE), FOR TOTAL SUSPENDED SOLIDS, TOTAL PHOSPHORUS,
ORTHOPHOSPHATE. TOTAL NITROGEN, AND NITRITE-NITRATE FROM VARIOUS
USES OF LAND(1^(2)

Land Use
Cropland(3)
Pasture
Forest
Residential
SED
46.5-3202.8
10.54-2460.83
145.20-669.70
16.45-303.50
9.40-71.5
0.53-48.60
38.00-634.4
47.40-2395.1

TP
0.21-12.49
0.05-9.78
0.38-1.12
0.04-0.51
0.06-0.23
0.00-0.16
0.10-1.66
0.13-5.22

OP
0.01-2.77
0.01-2.20
0.06-0.14
0.01-0.06
0.00-0.04
0.00-0.03
0.02-0.17
0.03-0.54

TN
1.3-22.2
0.75-17.59
2.20-6.20
1.25-2.81
0.40-1.10
0.02-1.00
0.70-2.8
0.87-8.82

N023
0.02-16.20
0.02-12.90
0.30-1.71
0.03-0.78
0.01-0.48
0.00-0.33
0.26-0.90
0.32-2.84


^^Volume-weighted concentration data from preliminary analysis by NVPDC,
   concentration in milligrams per liter.  Personal Communication:
   "Volume-Weighted Mean Concentrations of Storm Event Runoff from EPA/CBP
   Test Watersheds," J.P. Hartigan, Regional Resources Division, Norther
   Virginia Planning District Commission, Falls Church, VA, October 13,  1981.

(^Loading rate computed by CBP staff, in Ibs./ac./year.

'^'Cropland includes primarily conventional and minimum till with some no-
   till land practices.


TABLE VIII.8.  GENERALIZED RANKING OF LAND USES BY UNIT AREA RUNOFF LOADING
              RATE (1 = HIGHEST RATE, 4 = LOWEST RATE)

Land Use
Cropland
Residential
Pasture
Forest
TN
1
2
3
4
N023
1
2
3
4
TP
1
2
3
4
OP
1
2
3
4
SED
1
2
3
4

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                                                                                    I
    For instance, one of the cropland sites in the southern portion of the          tt
western shore produced less nitrite-nitrate per acre than one of the forest         V
sites on the upper Eastern Shore.  Although this example may be anomalous, it
illustrates that there is overlap in the data and that the rankings shown are       ซ
general in nature and by no means apply to all sites on all soil types.   They       •
are intended to give indications of which land uses, in general, have the
highest loading rates and which uses have the lowest rates, relative to  one         ^
another.                                                                            •
    Within the class of developed land use types such as residential and            ™
commercial uses, it has been shown (Smullen,  Hartigan, and Grizzard  1978;
Smullen 1979, NVPDC 1979) that there is a direct relationship between               •
intensity of land use, often measured as the  imperviousness of a site, and the      0
unit area loading rate yield of nutrients. A ranking of the urban uses  by
loading rate is shown in Table VIII.8.                                              ^

TABLE VIII.9. RANKING OF URBAN LAND USES BY UNIT AREA LOADING RATE1 FOR              ™
              NUTRIENTS (HIGHEST LOADING RATE = 1, LOWEST LOADING RATE ป 7)


Land Use	Ranking	

Central Business District                                    1                      •
Shopping Center                                              2
High-Rise Residential                                        3
Multiple Family Housing                                      4                      •
High Density Single Family Housing                           5                      •
Medium Density Single Family Housing                         6
Low Density Single Family Housing                            7                      •


    In general, urban uses exhibit higher unit area loading rates of nutrients
than forest or pasture uses and lower rates than cropland uses.  Exceptions to      •
this "rule of thumb" are that pasture typically will yield slightly higher          m
rates than the very low-density residential uses and that well-managed,
low-tillage cropland uses on pervious soils can yield lower rates than some of      A
the more intensive urban uses.                                                      I

 5.  What percentages of nonpoint source nutrient loadings can be attributed to
particular land uses?                                                               V

    Although it was relatively easy to sort out the point source from nonpoint
source loadings in answering questions 2 and  3, it is more difficult to              •
determine, with any level of precision, the fraction each land use contributes      0
to the overall nonpoint load.  We first must  accept two basic assumptions to
facilitate the estimate, and they are:  (1) that the land uses are                  ป
homogeneously distributed above the fall line; and (2) that baseflow loadings       •
(groundwater contributions) of nutrients may  be considered a constant
background load, and the nonpoint load is measured as surface runoff and
  (Smullen, Hartigan, and Grizzard 1977)
                                     243
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interflow^ nutrient loadings.  The homogeniety of land use assumption is
considered reasonable because most of the urban population resides on the
coastal plain (below the Fall Line) and, with the exception of the mountainous
areas, the agricultural and forest lands in the basin are fairly evenly
distributed.  This assumption is necessary because the closer a source is to
the Bay, the more effect its loading will have upon the water quality of the
system.  Thus, it is important that no large mass of a particular land use
type above the Fall Line be closer than any other type or there would be a
skew of the loadings at the Fall Line reflecting that skew in the land use
distribution.  The second assumption is necessary because we just don't
intuitively understand the functional relationship between land use and the
quality of groundwater discharge on basins the size of the Potomac, James, and
Susquehanna.2  We do know isolated facts — such as, the more fertilizer
applied, the greater the opportunity for increasing groundwater nitrate levels
and the resulting baseflow nitrate loadings in the stream.  For the purpose of
this analysis, it is enough to accept that for land uses that don't involve a
lot of impervious cover, the baseflow loadings will move reasonably well with
the runoff loadings.  That is to say, that land uses exhibiting higher
nutrient runoff loadings will produce groundwater discharge loadings equal to
or greater than those from uses exhibiting lower runoff nutrient loadings.
    The land uses above the Fall Line of the Chesapeake basin are about:
60-65 percent forested, 15-20 percent cropland, 8-12 percent pasture, 3-5
percent urban/suburban, and 2-14 percent other.  These are rough estimates
made from existing land use maps and will adequately serve the purpose of this
"order-of-magnitude" analysis.  Land use/nutrient loading rate relationships
developed locally within the Chesapeake basin (Smullen, Hartigan, and Grizzard
1978, Smullen 1979, NVPDC 1979) used for this analysis are shown below:
Land Use
Percent in Basin
       Estimated
Loading Rate (Ibs./ac./yr.)

Cropland
Pasture
Forest
Urban/Suburban

15-20
8-12
60-65
3-5
TN
8-18
2-6
.5-2
4-10
TP
1.5-5
.3-. 5
.05-.!
1-2

^Interflow is the lateral movement of water through soils to streams at
 shallow soil depths during and directly after storm events.  It is of short
 duration and, for our purposes, can be considered to be part of the runoff
 hydrograph.
*?
^This is a good example of why assessments such as this are best made with
 mathematic models.  They facilitate the orderly sorting out of base flow,
 runoff, and interflow and allow the analyst to handle groundwater
 contributions by inspection of observed flow data.
                                      244

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                                                                                    I
    The unit area loading rates shown above were weighted by the fractions of
the land areas in each use and the following ranges of loading fractions were
obtained:-^
Land Use
Cropland
Pasture
Forest
Urban
Percent of Nonpoint Source Load
     TN              TP
                            45-70
                             4-13
                             9-30
                             2-12
                    60-85
                     3-8
                     4-8
                     4-12
    In summary, agricultural cropland appears to produce the largest fraction
of the nonpoint source load from above the fall lines  by at least a factor of
two for both nitrogen and phosphorous.  This is partly due to a high unit area
loading rate for cropland and mostly due to the large  percentage of the land
area in this use.  Forest loadings of nitrogen are the next highest percentage,
and this is entirely due to the large fraction of the  watershed still being in
forest land.  Urban/ suburban and pasture lands above the Fall Line produce
approximately equal loads.
    By inspection, the percentages shown above would change very little if the
Coastal Plain areas were included.  Although the three major metropolitan
areas (Washington, D.C., Richmond, Virginia, and Baltimore, Maryland) would
increase the total amount of urban land area, this increase would probably be
offset by the large rural land areas of the eastern and western shore portion
of the Coastal Plain.  At any rate, even if the proportion of urban area
doubled, cropland would still be the largest nonpoint  source nutrient load by
an approximate factor of three.

g_  What are the nutrient loadings from the Fall Line?

    The nutrient loadings from the Fall Line are shown in Tables III. 10 and
again in Tables VIII. 2 through VIII. 5.  The values for total nitrogen and
total phosphorus are shown again below in millions of pounds.
                  Annua 1
                              Winter
Spring
                             Summer
                                                                 Fall


The
TN
TP
percentage
178.1
10.3
of the annual
51.4
2.97
above fall
72.2
4.29
line load
25.1 27.9
1.42 0.47
produced in each season are
shown below:




TN
TP
Winter
28.9
28.8
Spring
40.5
41.7
Summer
14.1
13.8
Fall
15.7
4.6
      best and worst case assumptions were used along with some common sense
 judgment.  For example, the lower range of cropland loading was produced by
 assuming the lowest loading rate/percent land use combination for cropland
 and the middle value of the ranges for all other uses.
                                                                                    I
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    From the data presented, it can be seen that the largest fraction of the
fluvial nutrient load (40 percent of both nitrogen and phosphorus) is
discharged to the tidal system during the spring.  Observation of the data in
Table III.10 shows that a large fraction of these spring loads are in forms of
nutrients that are readily available for aquatic plant uptake , with 68
percent of the nitrogen as ammonia or nitrite-nitrate and 34 percent of the
phosphorus as orthophosphorous.  This is important since the spring is the
critical start-up period for the phytoplankton growing season, the aquatic
plant growth that will dominate, in part, the dissolved oxygen and chlorophyll
conditions in the Bay through the summer and into the early fall.  As noted
elsewhere in this chapter, the predominant upstream source of the riverine
transported spring nutrient load is probably runoff and groundwater discharge
from agricultural lands.  The next most important source of nitrogen (but
probably lower by almost an order of magnitude) in spring river discharge from
above the fall line is probably runoff and groundwater discharge from the
melting of the snow-pack in the physiographic provinces upstream of the
Piedmont (see Figure III.2).
    The summer is the period during which the plankton growth in the Bay
reaches the annual maximum (see Chapter 2 of this part).  The fluvial
transported nutrients play a lesser role during this period, providing only
about 39 percent of the readily available nitrogen forms of plant nutrients
and only about 5 percent of the readily available phosphorus.  Plankton
communities flourish during this period primarily by recycling nutrients
already in the water column (put there in part by the spring fluvial process)
as noted in Chapter VII (Table VII.5); and secondarily by the supply of
nitrogen from atmospheric, point and benthic sources and by the supply of
phosphorus from point and bottom sources.

7.  What do the bottom sediments contribute to nutrient inputs?

    On an annual basis, bottom sediments contribute 32 million pounds of
nitrogen and seven million pounds of phosphorus [Table VIII.l(a)].  This makes
up about 10 and 25 percent of the annual nitrogen and phosphorous budgets,
respectively [Table VIII.l(b)].  However, the nitrogen contributed from the
benthic source is predominately ammonia and makes up about 45 percent of the
total annual Bay-wide contribution of this nitrogen species,  which is most
preferred by aquatic plants.  More than 50 percent of the externally supplied
water column ammonia produced during the spring and summer comes from the
benthos.
    The sediments have their most dramatic effect on the nutrient input budget
as a source of phosphorous in the summer.  As discussed in Chapter V, most of
phosphorous migrating up through the sediments via the pore waters is probably
chemically fixed by iron in the overlying oxygen-rich waters and held in a
fluff layer as a small particle, or floe.  This process occurs during most of
the year (late fall, winter, spring).  However, when the oxygen in the lower
layers of the Bay waters is depleted for periods during the summer, most of
the phosphorus incorporated or stored during the rest of the year is probably
released over a very short period of time.  The result is that as much as 62
percent of the phosphorous input to the Bay in the summer could come from this
source.  Other than recycling, the bottom source is probably the single
largest factor in the supply of phosphorous for summer primary productivity.
                                     246

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                  per day)	Annual Average
Winter
Spring
Summer
Fall
Annual Average
88.1
75.3
98.4
91.2
88.3
100
85
111
103

                                                                                    I
                                                                                    I
8.  What are the flux rates of nutrients from the bottom sediments and how do
they vary seasonally?

    The benthic flux rates for nitrogen range from as low as 0.5  pounds of N        A
per square foot per day in portions of the upper Bay in the spring to as high        I
as 5 pounds of N per square foot per day in portions of the upper Bay in the
spring and summer.  The annual seasonal Bay-wide average flux rates for             —
nitrogen are shown below:                                                            I

            Nitrogen Benthic Flux of Nitrogen
                (Thousands of Pounds      Percent of                                B
                                                                                    I
                                                                                    I
    As can be seen above, the summer period exhibits the highest flux rate of
nitrogen from the sediments, and the spring the lowest.   The nitrogen is            •
moving out of the sediments the fastest when the standing crop of                   I
phytoplankton is the largest, and it is being produced in a form readily
available for plant uptake.                                                         —
    As discussed previously, the seasonal variation of phosphorous flux from        •
the sediment to the water column is severe, with about 85 percent of the total      *
annual input being released rapidly sometime from late May to mid-June, with
most of the other 15 percent released from that time through late summer.           B
    An educated guess at the maximum Bay-wide phosphorous release rate is that      m
it might be as high as one-half million pounds a day during the period of the
rapid onset of bottom-water anoxia.  This rate probably levels off to about         M
16,000 pounds per day by late summer and down to near zero by sometime in late      •
fall.

9.  Given the estimated loadings of nutrients for each of the sources, which        •
will be the most important in terms of their effects on the Bay system?             ™

    This is a difficult question to answer because there are so many potential      •
effects on the Bay system that could result from variations in nutrient             |
loadings.  Some effects are understood well; some not so well, and some are
unknown.  However, to provide an answer to this question, we will consider the      M
potential effects on Bay-wide primary production which might result from            I
variations in the amounts of nutrients entering from various sources.
    On an annual basis (Table VII.2), probably only about 20-30 percent of the
Bay proper primary production is supported by nitrogen and phosphorous              •
entering the water column from external sources.  We will assume, for this          •
exercise, that nutrient recycling rates by phytoplankton would vary only
moderately in response to changes in external nutrient supply.  Given this          •
assumption, it can be seen from the data in Table VII.2 that even as much as a      •,
50 percent reduction in both point and nonpoint source annual nutrient
loadings may result in as little as a 10 percent reduction in Bay-wide primary
production.  Seasonally, this effect could decrease to only a 5 percent
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reduction in summer production in response to a 50 percent reduction of summer
point/nonpoint nutrient loading.  If these loading reductions were sustained,
production would probably decrease futher as the nutrient reservoir in the
sediments depleted over time.  These estimated decreases of primary
production  in the short-term approach the detection limit of our ability to
assess such reductions.
    The important point in this discussion is that changes in lower Bay water
quality (essentially meaning the great majority of the Bay that lies below the
mouth of the Patuxent) in response to changes in nutrient inputs would
probably take place slowly over decades.  However, the upper portions of the
Bay and the tidal tributaries would be much more responsive to change in
nutrient loads than the main Bay.  The nutrient loads that the main Bay
receives must travel through these smaller, heavily impacted areas of the
system.
    The nutrient inputs are diluted as they move towards the lower Bay as a
function of ever increasing volume.  In addition, the surface area available
for contributing nutrients from the sediments is much greater in the main Bay
than in the upper portions of the system, resulting in much larger bottom
releases of nutrients.  These factors and others create a situation in the
main Bay that tends to buffer or dampen water quality response to changes in
anthropogenic nutrient loadings.  It is, therefore, reasonable to expect the
water quality of the upper areas (tidal fresh areas) of the system to respond
more quickly to load reductions than the areas of the lower main Bay.
    The apparent improvement in the water quality of the upper Potomac in
response to decreased nutrient loadings over the last decade would seem to
support this concept.  Even though some unknown amount of that improvement is
probably due to differing climatic conditions over the last ten years, some
degree of the improvement is most likely due to the decreases in the external
nutrient supply from POTW's.  We would not expect to see immediate changes in
lower Bay water quality due to that reduction of loading and, in fact, have
not.  Such a change could only be seen over a much longer period of time and
to a lesser (diluted) extent.  This situation would seem to support the
concept that if we manage the local ("near field") problems, the main Bay
("far field") will, in time, respond in kind.  An aggressive policy of water
quality improvement in currently adversely impacted areas should insure the
maintenance of a nondegradation condition in the main Bay.
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                                LITERATURE CITED                                    I

Bricker, O.P., G.  Matisoff,  and G.R.  Holdren Jr.  1977.   Interstitial  Water
    Chemistry of Chesapeake  Bay Sediments.   Basic  Data Report  No.  9, Maryland        •
    Geological Survey,  Department of  Natural Resources,  Baltimore, MD.               •
Correll, D.L., T.L.  Wu,  J.W.  Pierce,  M.A.  Faust,  K.M.  Lomax,  J.C.  Stevenson,         •
    and M.S. Christy.  Rural  Non-Point Pollution  Studies  in Maryland.                ฃ
    EPA-904/9-78-002, U.S. Environmental Protection Agency, Washington,  DC.

Cronin, W.B.  1971.   Volumetric,  Areal and Tidal  Statistics of  the Chesapeake        •
    Bay Estuary and  its Tributaries.   Special Report No.  20., Chesapeake Bay
    Institute of the John Hopkins University, Shady Side,  MD.

Flemer, D.A.  1970.   Primary  Production in the Chesapeake Bay.                       V
    Chesapeake Science,  Vol.  11,  No.  2, pp.117-129.

Gambell, A.W., and D.W.  Fisher.       .  Occurrence of  Sulfate and  Nitrate in         |
    Rainfall.  Journal of Geophysical Research, Vol. 69,  pp 4203-4210.

Guide, V., and 0. Villa, Jr.   1972.   Chesapeake Bay Nutrient  Input                  •
    Study.  Technical Report  47,  Central Regional Laboratory, U.S.                  ™
    Environmental Protection  Agency,  Annapolis, MD.

Hill, J.M.,  and R.D. Conkwright.   1981.  Chesapeake Bay Earth Science                |
    Study:  Interstitial Water Chemistry.   Prepared in cooperation with  the
    U.S. Environmental Protection Agency Chesapeake Bay Program by the               ซ
    Maryland Geological Survey, Department of Natural  Resources, Baltimore, MD.      •

Lang, D.J.  1981. Water Quality  of  the Three Major Tributaries to the
    Chesapeake Bay,  January 1979  - April 1981 —  Estimated Loads and                 •
    Examination of Selected Water-Quality Constituents.  Water  Resources            •
    Investigations - Unpublished  Records,  U.S. Geological Survey,  Towson,  MD.
    (Draft)                                                                          •

Lang, D.J.,  and D. Grason.  1980. Water Quality  Monitoring of  Three Major
    Tributaries to the Chesapeake Bay - Interim Data Report.  Water -                ซ
    Resources Investigations   80-78,  U.S.  Geological Survey,  Towson, MD.            •

Neter, J., and W. Wasserraan.   1974.   Applied Linear Statistical Models.
    Richard  D. Irwin, Inc., Homewood, IL.                                            •

Northern Virginia Planning District  Commission and Virginia Polytechnic
    Institute and State University.   1977.  Occoquan/Four Mile  Run Non-Point         m
    Source Correllation Study:  Technical Report  for the  Period December 1,          I
    1976 - February  28,  1977.  Prepared for Metropolitan  Washington Water
    Resources Planning Board, Washington,  DC.                                       ^

Northern Virginia Planning District  Commission and Virginia Polytechnic              •
    Institute and State University.   1978.  Occoquan/Four Mile  Run Non-Point
    Source Correllation Study. A Final Report.   Prepared for Metropolitan          fl|
    Washington Water Resources Planning Board,  Washington,  DC.
                                   249
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Northern Virginia Planning District Commission.   1979.   Guidebook  for
    Screening Nonpoint Pollution  Management Strategies.   Prepared for  the
    Metropolitan Washington Council of Governments,  Washington,  DC.


SAS Institute.  1979.  SAS User's Guide:   1979 Edition.   SAS  Institute,  Inc.,
    Gary, NC.


Smullen, J.T., J.P.  Hartigan,  and T.J. Grizzard.   1978.   Assessment  of  Runoff
    Pollution in Coastal Watersheds.  In:   Coastal Zone  '78;  A  Symposium on
    the Technical,  Environmental Socio-Economic  and Regulatory Aspects  of
    Coastal Zone Management.  American Society of Civil  Engineers, New  York,
    NY.  pp 840-857.


Smullen, J.T.  1979.  A Simple Empirical  Model of Runoff Pollution for
    Environmental Planning.  M.S. Thesis,  Rutgers University, New  Brunswick,
    NJ.


Stensland, G.J.  1980.  Precipitation Chemistry Trends  in the Northeastern
    United States.   In:  Polluted Rain.  Plenum Press, New York, N.Y.


Taft, J. L., A. J.  Elliott, and W. R. Taylor.   1978. Box Model  Analysis of
    Chesapeake Bay Ammonium and Nitrate Fluxes.   In: Estuarine  Interactions,
    ed. Martin L. Wiley, Academic Press.


Taft, J. L.  1982.   Nutrient Processes.  This Volume.


Tyree, S.Y., M.A.O.  Bynum, J.  Stouffer, S. Pugh,  and P.  Martin.  1981.
    Chesapeake Bay Earth Science Study:  Sediment and Pore Water Chemistry.
    Prepared in cooperation with the U.S.  Environmental  Protection Agency
    Chesapeake Bay Program by the Department of Chemistry, College of William
    and Mary, Williamsburg, VA.  (Draft).


U.S. Environmental Protection Agency - Chesapeake Bay Program.   1982.
    Assessment of Nonpoint Source Discharge to Chesapeake Bay.   Information
    Series Nutrient Summary 3.  USEPA-CBP, Annapolis, MD. (In Press)


Uttormark, P.O., J.D. Chapin,  and K.M. Green.   1974. Estimating Nutrient
    Loadings of Lakes from Non-Point Sources.  EPA-660/3-74-020.   U.S.
    Environmental Protection Agency, Washington,  DC.


Virginia Polytechnic Institute and State  University.  1978. Occoquan/Four
    Mile Run Runoff Pollution Field Study (Fourth Quarterly Report).  Prepared
    for the Northern Virginia Planning District  Commission, Falls  Church, VA.


Virginia Polytechnic Institute and State  University. 1981. Progress Report,
    Evaluation of Management Tools in the  Occoquan Watershed.  Prepared for
    Virginia State Water Control Board, Richmond, VA.


Wade, T.L., and G.T.F. Wong.  1981.  Chemistry of Wet and Dry Fall in Lower
    Chesapeake Bay.   Prepared for the U.S. Environmental  Protection Agency
    Chesapeake Bay Program, Annapolis, MD.
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Ward, J.R.,  and D.A. Eckhart.   1979.   Nonpoint-Source Discharges  in Pequea          f
    Creek Basin, Pennsylvania,  1977.   Water Resources Investigations 79-88,
    U.S. Geological Survey,  Harrisburg,  PA.                                         —

Wolman, M.E.  1968.  The Chesapeake Bay:   Geology and Geography.   In:               *
    Proceedings of the Governor's Conference on Chesapeake Bay.   September
    12-13, 1968.  pp. 7-48.                                                         •



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                                 APPENDIX A


         METHODOLOGY FOR COMPUTATION OF NUTRIENT AND SEDIMENT LOADS
                      TRANSPORTED TO THE BAY BY RIVERS


    The dependent or response variable in each of  the models is  based upon
the flow - weighted daily mean concentration of the constituent  for which
the model is being formulated.  This was done to normalize the effects of
observations taken on the rising versus falling limb of a storm
hydrograph.  To determine flow-weighted concentrations  for days  when
multiple observations were collected, the products of  the concentration for
an observation and the instantaneous flow recorded for  that observation
were summed over all the observations in a day, and that sum was divided by
the sum of the instantaneous flows.   This is shown in  equation A-l:


                              n
                    Cj =     —      Gฃ qฃ             (eq.  A-l)
                            i = 1
    where Cj = flow-weighted mean daily constituent concentration
          Gฃ = individual constituent concentration observation (mg/1)
          q^ = instantaneous discharge at time of observations 'c1  (CFS)
          n  = number of observations in day 'J1 .
For the special case of n = 1, that is only one observation taken on a

particular day (e.g., a base flow observation), the mean daily
concentration is simply set equal to the observed concentration,  or Cj  =
Gฃ, after equation A-l.
Model Formulations:  Models were developed using the basic least  squares
regression normal error model (Neter and Wasserman, 1974) stated  as:

                     Yi = Bo + Blxi + ei       (eq- A~2>
    where BQ and B^ are parameters
          Yฃ and X^ are known constants (dependent and independent
                        variables)
          eฃ are independent N(0,s2)
          (The dependent variable Yฃ is based on Cj, Equation A-l)
All model formulations attempted are based upon the simple linear
regression model (eq. A-2) or the use of some remedial measure involving
transformations of the data.  Transformations were chosen either  to
linearize the regression function (semi-logarithimic or fully-logarithmic)
or to stabilize the error term variance.  Full descriptions of the
methodologies and validity of these approaches can be found in Neter and
Wasserman (1974) or most basic linear statistical models texts.


In all, twelve separate models were tested, made up of three sub-groups
with arithmatic, semi-log transformation by each axis, and
log-transformations on both axes performed within each sub-group.  All
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logarithms are taken as Napierian logarithms.  The model formulations are           •
described below.                                                                    ™

Concentration Models:  The basic form of this model sub-group is the                •
relationship between the mean daily, flow-weighted concentration of a               0
constituent (C, mg/1) versus the mean daily discharge.   (Q in cubic feet
per second per day [Cfsd]).  The four models investigated are shown below:           •
         i)   C versus Q                                                            I
         ii)  ln(C) versus Q
         iii) C versus ln(Q)
         iv)  ln(C) versus ln(Q)                                                    8

Loading Rate Models:   The basic form of this model sub-group is the
relationship between daily constituent loading rate (LR, Ibs/day) ,  computed         •
as the product of the flow-weighted constituent concentration for the day,           f
the mean daily discharge for the day, and a conversion factor, versus the
mean daily discharge (Q, cfsd)l.  The four transformations investigated             ซ
are shown below:                                                                    •
         i)   LR versus Q                                                           *
         ii)  ln(LR)  versus Q
         iii) LR versus ln(Q)                                                       fl|
         iv)  ln(LR)  versus ln(Q)                                                   •
    It is noted that a functional relationship exists between the mass of
pollutant washed off and discharge that is inherent in the determination of         •
the dependent variable term for this model.  It follows that the use of the         •
least squares method may not result in the best linear unbiased estimation
of the data in the Gauss-Markov theorem sense. 2  Although other biased or     •      ซ
nonlinear estimation approaches such as distribution-free or non-parametric         I
statistics might yield smaller variances, the least squares approach was            ™
chosen for its simplicity and ease of application.  It is also noted that
although the coefficients of determination developed from these models              B
remain useful for comparison with other models, the 't' tests for the slope         0
may not be useful for comparison with the other models because of the
suspected bias in the relationships.                                                M

Variance-Stabilizing Transformation Models:  The basic form of this
sub-group involves a transformation to stabilize error variances.  Residual
analysis through scatter plot observations of the C versus Q type models            •
(above) suggested that in many cases the variance of the error was                  ™
increasing with the volume of discharge.  That is, the relationships
appeared to have heterosadastic tendencies, exhibiting non-constant
variance over the range of observed flows.  Therefore,  the estimator BQ
                                  253
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     nutrient loading rate is computed as:                                           f
                   LR = K x C x Q
    where LR = Nutrient loading rate ( Ibs/day)                                      —
          K = Conversion factor equal to 5.38 (liter-sec. -Ib/mg.-f t-^-day)           I
          C ** Nutrient concentration in mg/1                                        *
          Q = Mean daily discharge in cubic feet per second
*That is to say, the least squares estimator may not have  a minimum                 •
 variance within the class? of linear, unbiased estimators.                           ™
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and BI (eq. A-2),  though still unbiased,  are no longer minimum variance
unbiased estimators.  Neter and Wasserman (1974) suggest a transformation
of the form:
                          Y'= Y   and  X1  = j.          (eq.  III-3,  III-4)
                              X              X
to minimize the variance.  The general form, then,  of this group of  model
is as follows:


      i) (C/Q) versus (1/Q)
     ii) ln(C/Q) versus (1/Q)
    iii) (C/Q) versus ln(l/Q)
     iv) ln(C/Q) versus ln(l/Q)
 Neter and Wasserman point out that this  transformation is really
equivalent to using weighted least squares and further indicate that the
relationship remains unbiased.  Regression statistics ('t1 tests) remain
fully useful.


Regression Analysis
    The correlation coefficient for each  of the models described above were
computed at each site for the water quality parameters listed in Table
A.I.  The coefficients of determination for the Susquehanna,  Potomac and
James models are shown in Table A.2, A.3  and A.4.  Only models exhibiting
coefficients in excess of 0.50 are shown.


TABLE A.I.  WATER QUALITY VARIABLES INCLUDED IN REGRESSION ANALYSIS

Water Quality Parameter
Total Nitrogen (as N)
(Particulate & dissolved)
Dissolved Nitrogen (as N)
Total Kjeldahl Nitrogen (as N)
Total Nitrite plus Total Nitrate
Nitrogen (as N)
Total Ammonia Nitrogen (as N)
Total Phosphorus (as P)
STORET No.
600
602
625
630
610
665
Variable Name
TN
DN
TKN
N02 + N03
or N023
NH3 + NH4
or NH34
TP
  (Particulate & dissolved)


Dissolved Phosphorus (as P)


Total Orthosphosphorus (as P)


Suspended Sediment
  666


70507


80154
DP


OP


SED
    The Tables (A.2, A.3, and A.4) show that poor fits (r2   0.50)  were
found in almost all cases for the concentration-versus-discharge models.
                                   254

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In most cases, visual inspection of scatter diagrams allows a case to be           •
made for heteroodasticity and, for this reason, the variance-stabilizing
transformation were favored in selecting appropriate models.!  Only when           m
correlation coefficients were significantly below 0.65 or "t" tests                •
(HO;BI = 0) indicated that Bj_, the slope, was not significantly                    ™
different from zero at the 95 percent confidence level was a loading rate
model chosen.                                                                      •
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^•During the course of examination of the concentrations predicted by each          B
 of the models over the range of flow observed in the period of record, it         •
 was determined that the arithmetic form of the variance-stabilizing
 transformation (C/Q versus 1/Q) yielded unrealistically high values for           m
 discharges in excess of those observed during the period of the monitoring        •
 program.  The log-log transformation of this model [ln(C/Q) versus
 ln(l/Q)] proved to be much better behaved in predicting concentrations for        _
 these higher flows.  The curves produced with this transformation "flatten        •
 out" very quickly as flows approach those at the upper limit of the               '
 discharge data observed during the field program.  Therefore, only the log
 transformed versions of the variance-stabilizing transformation were              •
 considered for cases exhibiting heterosodasticity.                                I
                                  255

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TABLE A.2.   REGRESSION MODEL RESULTS FOR THE  SUSQUEHANNA RIVER AT  CONOWINGO,
            MD (1578310)  RESULTS DISPLAYED ONLY FOR MODELS  EXHIBITING
            COEFFICIENTS OF DETERMINATION IN  EXCESS OF 0.50

Water Quality
Constituent
TN






DN






N023






NH34



TKN





Model
C/Q vs. 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (l/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
in (LR) vs. in (Q)
r2
.948
.503
.916
.852
.722
.611
.933
.972
.518
.926
.832
.742
.618
.931
.927
.382
.887
.859
.668
.694
.906
.575
.558
.611
.713
.916
.551
.805
.644
.707
.850
d.f .
86
86
86
86
86
86
83
66
66
66
66
66
66
66
86
86
86
86
86
86
86
87
87
86
86
87
87
87
87
87
87
                                 (continued)
                                 256

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TABLE A.2.  (continued)

Water Quality
Constituent      Model                 r2        d.f.
TP






DP




OP



SED





C vs. Q
In (C) vs. Q
C/Q vs. 1/Q
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
In (C/Q) vs 1/Q
In (C/Q) vs. In (1/Q)
In (LR) vs.Q
In (LR) vs. In (Q)
In (C) vs. Q
C/Q vs. 1/Q
In (C/Q) vs 1/Q
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
.518
.503
.863
.565
.696
.792
.885
.565
.778
.597
.612
.797
.512
.639
.600
.730
.677
.542
.667
.550
.741
.665
87
97
87
87
87
87
87
88
85
88
85
85
60
66
66
66
96
93
93
93
93
93
                                   257

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TABLE A.3.  REGRESSION MODEL RESULTS FOR THE POTOMAC RIVER AT CHAIN BRIDGE,
            WASHINGTON, DC  (1646580) RESULTS DISPLAYED ONLY FOR MODELS
            EXHIBITING COEFFICIENTS OF DETERMINATION IN EXCESS OF 0.50

Water Quality
Constituent
TN





DN







N023




NH34
TKN





TP



DP



Model
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. In (Q)
In (LR) vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs. In (1/Q)
In (LR) vs.Q
In (LR) vs. In (Q)
In (C/Q) vs 1/Q
In (C/Q) vs. In (1/Q)
In (LR) vs. In (Q)

r2
.847
.551
.776
.856
.571
.914
.704
.597
.681
.840
.721
.717
.592
.913
.637
.618
.804
.637
.869
.707
.682
.580
.565
.719
.531
.849
.510
.588
.549
.847
.576
.718
.801

d.f.
64
64
64
64
64
64
63
63
63
63
63
63
63
63
64
64
64
64
64
61
80
80
80
80
80
80
80
79
79
79
'77
77
77
                                 (continued)
                                  258

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TABLE A.3.  (continued)
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Water Quality                                                                     flj
Constituent      Model                r2    d.f.                                  I



OP           C/Q vs.  1/Q              .583        56
             In (C/Q) vs.  In (1/Q)     .622        47
             In (LR)  vs.Q              .573        47                               •
             In (LR)  vs. In (Q)        .696        47                               •

SED          C vs.  Q                   .515    60                                   •
             In (C) vs.  Q              .512    60                                   |
             In (C) vs In  (Q)          .658    60
             LR vs. Q                 .796    60                                   _
             In (LR)  vs.Q              .640    60                                   •
             In (LR)  vs. In (Q)        .879    60                                   •


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TABLE A.4,  REGRESSION MODEL RESULTS FOR THE JAMES RIVER AT CARTERSVILLE,  VA.
           (2035000) RESULTS DISPLAYED ONLY FOR MODELS EXHIBITING
           COEFFICIENTS OF DETERMINATION IN EXCESS OF 0.50

Water Quality
Constituent
TN







DN






N023






NH34



TKN







Model
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (l/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (l/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
LR vs. In (Q)
In (LR) vs. In (Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)

r2
.769
.679
.633
.817
.842
.728
.523
.909
.861
.728
.713
.894
.720
.713
.909
.530
.509
.759
.816
.568
.614
.824
.646
.525
.551
.725
.653
.617
.509
.665
.786
.727
.862

d.f.
54
54
54
54
54
54
54
54
38
38
38
38
38
38
38
56
56
56
56
56
56
56
49
56
49
49
55
55
55
55
55
55
55
                                 (continued)
                                  260

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TABLE A.4.  (continued)
Water Quality
Constituent
TP






DP






OP




SED






Model
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
C/Q vs. 1/Q
In (C/Q) vs 1/Q
C/Q vs In (1/Q)
In (C/Q) vs. In (1/Q)
In (LR) vs. In (Q)
C vs. Q
In (C) vs. Q
C vs. In (Q)
In (C) vs In (Q)
LR vs. Q
In (LR) vs.Q
In (LR) vs. In (Q)
r2
.781
.718
.522
.669
.715
.758
.762
.873
.754
.588
.908
.626
.526
.581
.809
.725
.537
.815
.511
.631
.539
.535
.723
.841
.647
.903
d.f.
56
56
56
56
56
56
56
56
56
56
56
56
56
56
48
46
48
46
46
71
71
71
71
71
71
71

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                           SUMMARY AND CONCLUSIONS
    Increased population and changed land uses  (deforestation,  agriculture,
urbanization) in the Chesapeake Bay watershed have  caused  increases  in
nutrient and sediment loads to the Bay system over  the  past  50  years.   The
challenge facing water quality managers is to restrict  excessive  nutrient
addition as efficiently as possible, at the most effective times  and
locations, and for the least expense.  The Nutrients  projects of  the
Chesapeake Bay Program, discussed in this Synthesis Paper, were designed to
help managers meet this challenge by increasing their understanding  of  the
nutrients problem, its sources, and important processes.


THE NUTRIENT ENRICHMENT PROBLEM


    Many areas of the Chesapeake Bay system have a  serious nutrient
enrichment problem.  Our studies indicate that  the  upper  Bay, between
Turkey Point and the Bay Bridge, upper Potomac, upper Patuxent, and  upper
James are heavily enriched; the mid-Bay,  lower  Patuxent,  lower  Potomac,
Rappahannock, York and middle James Rivers are  moderately  enriched.  These
areas are considered to be enriched, because chlorophyll  a_ levels are
elevated over historical levels.
    Nutrient enrichment results in enhanced phytoplankton  production and
higher levels of organic matter in the water column.   Decomposition  of
excessive organic matter results in depletion of oxygen from deeper  waters,
posing a hazard for bottom-dwelling animals.
    Nutrient enrichment also alters the composition of phytoplankton
species.  Such changes have been shown to affect fisheries species
composition in other systems, and may have the  same effect in Chesapeake
Bay.
    The increased turbidity resulting from nutrient enrichment  decreases
the amount of light available for submerged aquatic vegetation  (SAV), and
has been implicated in their decline.


Solving the Problem:  The Importance of Nutrient Processes


    The extreme solution to nutrient enrichment problems  is  to  eliminate
the entry of excess nutrients to the Bay system. However, because of
social and economic restraints, this is not possible.  Instead, we must
restrict the particular nutrients most responsible  for the problems, at  the
most effective times and places.  To do this requires an  understanding  of
nutrient processes.
    Seasonal factors determine the times at which nutrient restriction  is
the most effective.  The availability of nutrients  follows an annual
cycle.  In spring, heavy flows bring a substantial  amount  of nitrate into
the Bay.  In summer, deoxygenation of deep water results  in  release  of
phosphate from bottom sediments and the accumulation  of phosphate and
ammonium in bottom waters.  In the fall,  re-oxygenation of deep waters
results in loss of phosphate from the water column  and  oxidation  of
ammonium to nitrite and nitrate.
                                 262

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                                                 I
    Nutrient limitation of phytoplankton growth is a function of nutrient
availability and the intrinsic requirements  of phytoplankton.  Healthy             _
phytoplankton require carbon,  nitrogen,  and  phosphorus  in certain ratios.          I
The nutrient in least supply with respect to the requirements of                   ™
phytoplankton will limit their growth.   Nutrient limitation occurs only if
other environmental conditions (like light availability)  are satisfactory;          fl
when too little light is available,  for  example, light  becomes the limiting         •
factor.  When a nutrient is limiting,  addition of that  nutrient will
stimulate phytoplankton growth.                                                     •
    Phosphorus is potentially  limiting in the tidal-fresh reaches of  the           I
Bay throughout the year (sediments of  tidal-fresh segments do not become
anoxic, so phosphorus is not released  from them).  In the remainder of the
Bay system, phosphorus is potentially  limiting in spring  and fall;  nitrogen         I
is potentially limiting in summer.  Light is limiting in  winter and in             •
situations of high turbidity.
    Whether increases in algal production result in problems depends,  in           •
part, on nutrient cycling.  Water column nutrient cycling processes,  such          •
as hydrodynamics and grazing,  help remove excess plankton biomass from the
system.  Decomposition, on the other hand, depletes the system of oxygen.
Regeneration of inorganic nutrients through  these processes provides  a             •
source of nutrients for phytoplankton  growth.                                      ™
    Nutrient cycling processes in the  sediments affect  levels of nutrients
in the water column.  Phosphorus is removed  from the water column by
adsorption to iron and manganese compounds,  to be released in summer  from
anoxic areas.  Ammonium fluxes into, or  out  of, the sediments, depending on
pore water concentrations and  oxidation  state.                                     •
    Marshes and Bay grasses contribute to nutrient recycling by taking up          I
nutrients during their growing season (periods of peak  availability)  and
releasing nutrients during the winter  through decomposition.  Thus, they
act as nutrient buffers.                                                           I
    Once the role of specific  nutrients  in specific times and places  is            •
understood, nutrient sources must be known before exact and economical
solutions to nutrient problems can be  developed.                                   •

Nutrient Sources:  The Key to  Comprehensive  Control

    On an annual basis, atmospheric contribution to the tidal waters  of the         I
Bay system make up about 13 percent of the nitrogen and five percent  of the         *
phosphorus.  In winter, up to 20 percent of  the nitrogen  may come from
atmospheric sources.                                                               I
    Point sources contribute up to 25  percent of the nitrogen and 40                •
percent of the phsophorus annually.  While the nitrogen contribution  varies
little during the year, the phosphorus contribution may be as much as 65           •
percent in the fall.                                                               •
    Nonpoint sources (land runoff/base flow) contribute up to 55 percent of
the nitrogen annually, the largest source of this nutrient to the Bay
system.  In spring, nonpoint sources contribute up to 66  percent of the            M
total nitrogen.  Nonpoint sources of phosphorus make up about 34 percent of         •
the annual total; in spring the contribution is about 55  percent.  The land-
use contributing the most to these percentages, both on a unit area basis
and as percentage of the total, is cropland.
263
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    Bottom sediments contribute about 10 percent  of nitrogen and  25  percent
of phosphorus annually.  The nitrogen contribution,  primarily as  ammonia,
is more than 50 percent in spring and summer.   The  bottom of the  Bay is  the
largest contributor of phosphorus in the summer,  supplying as much as 62
percent of this nutrient.
                                  264

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                               Appendix A

                    CBP Nutrient Enrichment Projects
Definition of Chesapeake
Bay Problems of Excess-
ive Enrichment or Eutro-
phication
Evaluation of Management
Tools in Two Chesapeake Bay
Watersheds in Virginia

Evaluation of Water Quality
Management Tools in the
Chester River Basin

Intensive Watershed Study
(Patuxent River Basin)

An Assessment of Nonpoint
Source Discharge, Pequea
Creek Basin, Lancaster County,
Pennsylvania.

Modeling Philosophy and
Approach for Chesapeake Bay
Program Watershed Studies

Fall Line Monitoring of the
Potomac, Susquehanna, and
James Rivers

Land Use and Point Source
Nutrient Loading in the
Chesapeake Bay Region

Chesapeake Bay Circulation
Model

Water Quality Laboratory
for Chesapeake Bay and its
Subestuaries at Hampton
Institute

Chesapeake Bay Nutrient
Dynamics
L. Eugene Cronin
Bruce Nielson
Andrew McErlean
Donald Heinle
Kenneth Webb
Jay Taft
Robert V. Davis
Thomas Grizzard
Bruce Nielson

Howard Wilson
Charles Bostater
Howard Wilson
Charles Bostater

Robert J. Bielo
Janice Ward
Robert Ambrose
David Grason
David Lang
Benjamin J. Mason
Robert Shubinski
Larry T. Cheung
Jay Taft
Chesapeake Research
Consortium
Virginia State Water
Control Board
Maryland Water Resources
Administration
Maryland Water Resources
Administration

Susquehanna River Basin
Commission
U.S. EPA Environmental Re-
search Laboratory, Athens,
Georgia

Water Resources Division,
U.S. Geological Survey
Geomet, Incorporated
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Water Resources Engineers, Inc.
Hampton Institute
Chesapeake Bay Institute
                                     265
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    PART III
TOXIC SUBSTANCES
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W                                             by
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                            R. Bieri, 0. Bricker, R. Byrne, R. Diaz,
                            IG. Helz, J. Hill, R. Huggett, R. Kerhin,
                             M. Nichols, E. Reinharz, L. Schaffner,
                                   D. Wilding, and C. Strobe1
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•m                                        Duane  Wilding
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                                  CONTENTS

Number
                                                                               I
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Figures	    269       •
Tables	    271       •
Sections
    1.   Introduction	    275
    2.   Findings from Studies on Metals	    280
         Sources
              Industries and POTWs below the fall line	    280
                                                                               I

          j-iiuusuri.es cinu ruins uexuw me LULL  j. me  ........    zou       H
          Atmospheric sources  	    282       •
          Urban runoff	    286       *
          River sources	    287
     Distribution and Concentration of Dissolved Metals  	    293       I
                                                                                   I
     Distribution and Concentration of Metals in Suspended
       Material	    299
     Distribution and Concentration of Metals in Bottom
       Sediments	    306
     Metals in Interstitial Water  	    306
3.   Findings from Studies on Organic Compounds  	    313
     Sources	    313        •
     Organic Compounds in Bottom Sediments 	    314        ™
     Organic Compounds in Oysters  	    319
     Conclusions	    322        •
4.   Patterns of Toxic Metal Enrichment  	    324        |
     Interpretation of Processes Affecting Metal Distributions  .  .    324
     Metal Enrichment	    325        _
          Historic metal inupt recorded in sediments  	    327        •
     Metal-Sediment Relationships  	    329        *
5.   Findings on Sediments and Biota	    331
          Character of Bed Sediments	    331        I
               Texture	    331        •
               Water Content	    332
               Carbon and Sulfur	    332        •
               Patterns of sedimentation 	    334        f
          Benthic Organisms	    336
               Character of benthic fauna  	    336        _
               Community composition 	    337        I
               Vertical distribution 	    337        •
               Bioturbation  	    337
               Biological sediment mixing and fate of toxicants.  .    338        •
6.   Toxic Substances and Biota	    341        |
     Exposure Assessment	    341
     Toxicity Studies	    342        H
          Histopathology 	    342        •
          Sediment bioassays 	    342
          Effluent toxicity tests  	    343
7.   Conclusions, Interpretations, and Management                              •
       Implications  	    345        •
8.   Research Needs	    349
                                   267
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Literature Cited 	 352
Appendices
    A.  Inventory of project data discussed  in this  report	362
    B.  Summary of data sources for  trace metals  in  the  Chesapeake
        Bay and tributaries	365
    C.  Summary of data sources for  organic  chemicals  in the
        Chesapeake Bay and tributaries	367
    D.  Areal distribution of sediment  type  in Chesapeake Bay;  from
        data of Kerhin et al. (1982)  and Byrne et al.  (1982)	368
    E.  Summary of Chesapeake Bay toxic source assessment and
        bioassay tests ......... 	  , 369
    F.  Results of fish bioassays for effluent samples by species  .  .  . 375
    G.  Results of invertebrate bioassays  for  effluent samples  by
        species	375
    H.  Results of bacterial and grass  bioassays  	 376
    I.  Results of Salmonella/Microsomal assays for  mutogenicity of
        Chesapeake Bay effluent samples	377
    J.  Results of mammalian cellclonal acute  cytotoxicity  assay  .... 378
                                  268

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                                   FIGURES

Number
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 1       Graph of age versus metal  content  of Cu and  Zn  showing                     •
         historical increase of "excess"  metal concentration  due  to
         atmospheric deposition in  Chesapeake Bay core 4 (Helz et al.
         1981) by comparison to Farm River  Marsh concentrations	285        •

 2       Temporal variations of:  (a)  Susquehanna River  discharge at
         Conowingo Dam;  (b)  corresponding Fe;  and (c) Mn                           •
         concentrations,  dissolved,  suspended, and total.  Data based               •
         on instantaneous measurements and  samples at peak inflows  .  .  .  290

 3       Plot of:  (a) dissolved Mo  content versus salinity,  and  (b)                •
         dissolved Cr content versus salinity for samples from surface              ™
         water along the  Chesapeake  Bay length,  June-July 1979	294

 4(a)    Ratio of dissolved  Cu concentration  in surface  water to                    |
         dissolved Cu concentration  in bottom water versus salinity.  .  .  296

 4(b)    Ratio of dissolved  Mo concentration  in surface  water to                    •
         dissolved Mo concentration  in bottom water versus salinity.  .  .  296

 5(a)    Plot of the ratio of dissolved Cu  concentrations in  surface                I
         water to bottom  water versus  the ratio of surface salinity                 •
         to bottom salinity	298

 5(b)    Plot of the ratio of dissolved Mo  concentration in surface                 •
         water to bottom water versus  the ratio of surface salinity
         to bottom salinity	298

 6       Longitudinal-depth  distributions of  mean metal  concentration               •
         per gram of suspended material,  along the axis  of Chesapeake
         Bay, for (a) Cd, (b) Cu, and  (c) Pb.   Relatively high zones,               W
         shaded	300        |

 7       Distribution of  metal content in surface suspended material                jm
         with distance along the Bay axis.  Median values and range of              B
         concentrations from all available  observations.  Shaded  zone
         indicates magnitude of departure between median values and mean
         values for Fe-corrected average  shale,  open circles	301        •

 8       Distribution of  metal content in near-bottom suspended
         material with distance along  the Bay axis. Median values and              M
         range of concentrations from all available observations.                   ฃ
         Shaded zone indicates magnitude  of departure between median
         values and mean values for Fe-corrected average shale, open                _
         circles	302        •
                                   269
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Number                                                                  Page


 9       Distribution of Cu content in bottom sediments  of  (a)  bulk
         bed sediment, unfractionated, and (b)  the less  than  63 u  size
         fraction, fractionated	307


10       Distribution of Zn content in bottom sediments  of  (a)  bulk
         sediment, and (b)  the less than 63 u size fraction	308


11       Vertical profiles  of Si02, P04, HCO$,  Mn, Fe, and  NH4  in
         interstitial water composition for a station  in central
         Chesapeake Bay, September-November 1978 	 310


12       Distribution of Chemical Sedimentary Environments  in Chesapeake
         Bay, based on data of Hill and Conkwright (1981)	311


13       Typical gas chromatogram of a sediment sample	315


14       Chart of station locations and bar graph  representing
         concentration sums of all resolvable peaks for  organic
         compounds in sediments,  spring samples 1979	316


15       Chart of station locations and bar graph  representing
         concentration sums of all resolvable peaks for  organic
         compounds after normalizing for silt and  clay content,
         spring samples 1979	317


16       Chart of station locations and bar graphs representing
         concentrations sums of all resolvable peaks for organic
         compounds in oysters, spring samples  1979	318


17       Distribution of PNA, benzo(a)pyrene, in channel sediments
         from Baltimore Harbor and the Patapsco River.   Relative
         concentration relates to height of column at  each  location.  .  . 321


18       Longitudinal distribution of enrichment factors for  Cu, Mn,
         Pb, and Zn in bed  sediments along the length  of Chesapeake
         Bay.  Zn enrichment zones shaded	326


19       Metal/aluminum ratios, Zn/Al, Cu/Al, for  three  cores from
         northern and central Chesapeake Bay, cores 4, 18,  and  60.
         Dates in ZlOpjj years; departure of metal/aluminum  and
         metal/iron ratios  from background in each core, shaded	328


20       Relationship of percent water content to  percent mud content
         for surface sediment samples from the southern  Bay	333


21       Sedimentation zones in areas of fine sediment,  greater than
         40 percent clay with greater than 1.0  m of shoaling  per 100
         years, in the Bay  proper	335


22       Distribution of percent  bioturbation in sediments, Fall 1978.  . 339
                                   270

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Number
1


2
3

4


5(a)



5(b)


5(c)

5(d)


6

7


8


9(a)




9(b)

9(c)


10




TABLES

Page
Point source loadings of metals from industries and publicly
owned treatment works (POTWs), in counties below the fall line

Atmospheric input of selected metals to Chesapeake Bay .... 283


Urban runoff loadings from major metropolitan areas of the


Average annual loadings for selected dissolved metals at
monitoring stations on the Susquehanna, Potomac, and James


Annual and long-term mean annual flows for the Susquehanna,


Comparison of CBP loadings from the Susquehanna River with

Metal loading rate factors for the Susquehanna, Potomac, and


Data for capacity/inflow ratios and percentage of suspended

Source inventory of metal influx to Chesapeake Bay, metric


Summary of mean and median dissolved metal concentrations
and range of Bay-wide values, ug per ml. Data from Kingston
(1982)' cruise of June- July 1979 	 	 299
Summary of mean metal concentrations and range of Bay-wide
values per gram of suspended material, left and weight per
volume of suspended material, right. Data from Nichols
(1981) for eight cruises along the Bay length between months of

Mean, median, and range of metal content for one cruise along
the Bay length, June- July 1979. Data from Kingston (1982). . 303
Mean particulate dissolved and total metal content in surface


Flux estimates of selected dissolved constituents from
Chesapeake Bay bed sediments mm/cm^/yf . 	 	 312


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Number


11       Relationship of bulk chemical analyses  of  metals  (Helz  et
         al. 1981) versus sediment parameters  (Byrne  et  al.  1981)
         by stepwise regression 	  330


12       Summary of histological  abnormalities found  in  Macoma
         balthica clams from upper and lower Bay tributaries.  Data
         represent number of clams with abnormalities; parentheses
         indicates the percent of total from the River	343

13       Toxicity tests performed on industrial  effluent	344
                                  272

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aerosol:

anoxic:
anthropogenic :
As

bioecology:


Cd
Ce

Co
Cr
Cu
diagenesis:



dpm cm" 2
Eh
fall line:

Fe
ft3/sec
Hg

interstitial:

lithology:
loads :

Mn
Mo

Technical Glossary
A colloidal solution in which a substance in which the
other is dispersed, is a gas.
Total deprivation of oxygen.
Of human origin and development.
arsenic

The science that deals with the interrelations of
communities of animals and plants with their environment.

cadmium
cesium

cobalt
ch romium
copper
Physical and chemical changes occurring to sediments
during and after the period of decomposition up until
the time of consolidation.

distintegrations per minute per square centimeter
oxidation-reduction potential
Geographical line indicating the beginning of a plateau,
usually marked by many waterfalls and rapids.
iron
cubic feet per second
mercury

Of, forming, or occurring in small or narrow spaces
between things or parts.
Science of rock structures.
Quantity of a constituent per unit per time.

manganese
molybdenum

1



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mT
Ni
oxic:
Pb
ppt
ps=
Sc
Sn
synergism:
Th
U
ug cm"~2
Zn










metric tons
nickel
applied to a soil layer from which much of the silica
that was combined with iron and alumina has been leached
lead
parts per thousand
expression of sulfur ion content
scandium
tin
The property or condition of working together, such as
muscles together effecting a certain motion, or of
hormones, or medical substances.
thorium
uranium
micrograms per centimeter
zinc








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                                  SECTION 1

                                INTRODUCTION
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     This part of the CBP Synthesis Report  summarizes  and integrates  the           8
research findings and recommendations  of 13 projects of  the  Chesapeake  Bay          •
Toxic Substances Program performed between  July 1978 and October 1981.   The
following sections describe research on potentially toxic substances,  or           •
toxicants, in water-sediments and selected  biota.   The subjects  considered          •
include a brief review of metals, their sources,  distribution and behavior,
and then a review of sources and distribution of  organic chemicals.                 _
Finally, information concerning the significance  of toxicants in the  Bay           •
and their pattern of enrichment is provided.  Most information synthesized          •*
in this report can be traced to its origin  in scientific project reports
listed in Appendix A.                                                              •
     The last three decades have witnessed  some disturbing changes in              jง
Chesapeake Bay.  Some biotic components are less  abundant than in the past
and are below natural levels.  Oyster reproduction has diminished                  ฃ
throughout the Bay.  Of particular concern  is the virtual disappearance of          •
rooted aquatic plants over a large portion  of the Bay  floor.   Fish,  such as
shad and striped bass, once spawned in astronomical numbers;  but in  recent
years, they have declined severely (Cronin  1977).   Taken together, these           •
changes are cause for concern.                                                      9
     An understanding of what is happening, and why, to grass, bass,  shad,
and oysters still eludes scientists, though toxic substances are strongly          •
suspected to be at least partially responsible.  The lessons learned  from          f
DDT and PCB contamination show that toxicants can cause substantial
ecological damage, ranging from reproductive failure in fish and birds  to          ^
inhibition of photosynthesis in phytoplankton.  The outbreak of                     M
neurological illness with 52 deaths caused  by mercury  (Hg) poisoning  of            ™
shellfish in Japan amplifies the fact that  toxic  contamination in seafood
resources can reach humans.  Release of Kepone into the James River  in             •
Virginia, resulted in closure of the estuary to fishing for years, with an          V
enormous economic loss and a. need for a large-scale, expensive cleanup.
Chlorine, a widely used biocide in sewage treatment plants,  is strongly            ซ•
suspected of causing massive fish kills in  the James River in 1973 (Douglas        •
1979).
     Toxic substances are usually defined as chemicals or chemical
compounds that can poison living plants and animals,  including humans,  or          •
impair physical or chemical processes.  Two classes of toxic substances            ™
pose a threat to the Bay environment:   inorganic  and organic compounds.
The inorganic materials are the metals.  They can be produced and delivered        M
to the Bay by natural processes as well as  by human activities.                     j|
Potentially toxic metals include arsenic (As), cadmium (Cd) , chromium (Cr)  ,
copper (Cu), mercury (Hg), tin (Sn), and zinc (Zn). Many of the organic           •
compounds are products of human activities.  However,  a few polynuclear            •
aromatic compounds (PNAs) can occur naturally, and thus augment the
synthetic compounds.  The main classes of organic compounds are pesticides,
phthalate esters, polynuclear aromatic hydrocarbons, metalorganic                   I
compounds, alkyl-benzines, plasticisers, polychlorinated biphenyls (PCBs),          ซi
and other halogenated hydrocarbon compounds.
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    Assessing the effects of toxic substances on biota has always been a
difficult task.  Effects range from rapid death, or acute toxicity,  to
gradual reductions in spawning s.uccess,  or chronic toxicity.   Months,  or
years of careful observations may be required to determine chronic effects
for one chemical on one species.   Effects of chemical mixtures on several
species or a community are even more difficult to detect.  The environment
may also experience synergistic and antagonistic effects through exposure
to two or more chemicals.  In addition,  toxic effects can be masked by wide
fluctuations in natural conditions.  In the laboratory, scientists have
attempted to simulate effects of chemicals on the natural environment  by
subjecting single organisms, or a limited number of organisms, to
toxicants, and observing the cause-and-effeet relationships.   But transfer
of this information to interpret changes in entire faunal communities, with
their wide variability within species,  has achieved only limited success.
    Because it is difficult to specify cause-and-effect relationships
between toxicants and Bay resources, we attempted, during the Chesapeake
Bay Program, to determine areas where levels of toxicants are high (above
standards or threshold levels), and then relate these levels  to known  toxic
effects.  This evaluation will give us some insight into the existence of
toxicity problems.
    In summary, some trends recognized at the onset of the Program caused
us to believe that the status of toxic substances in the Bay should be
studied.  These trends included:   (1) decline of biotic components in  the
past three decades (Cronin et al. 1977); (2) increases in the number of
potentially toxic chemicals being synthesized, produced, and used in the
region (Huggett et al. 1977); (3) discharge of large amounts  of potentially
toxic substances (Brush 1974); (4) increase in population growth and
industrial activity; (5) accumulation of toxicants in the sediments and
biota, including commercial food species, many thousand-fold  more than in
ambient concentrations in the water (Huggett et al. 1974b, Huggett et  al.
1977); and (6) carcinogenic nature of many organic compounds  found in  the
Bay.  At the same time the Bay is an important environmental  resource  for
fisheries, wildlife, and recreation.  Since controlling the threat of  toxic
substances to viable ecological resources requires new knowledge of their
sources, distribution, and fate in the Bay ecosystem, we studied these;
factors.
    Before the initiation of the CBP, information on metals and organic
compounds was scarce.  Data on the existence of metals were limited to the
distribution and abundance of some trace metals in the northern Bay and
several western tributaries.  Likewise,  available information on organic
compounds consisted of levels of some chlorinated hydrocarbons (DDT, PCBs)
and Kepone found in selected bivalves,  fish, phytoplankton, and sediments
of some parts of the Bay and tributaries.  The CBP studies not only support
and systematically expand this knowledge, but add information on sources of
metals and organic compounds to the Bay, their behavior in the estuary, and
impacts on resources.
    Published information on potentially toxic metals in the Bay prior to
the Chesapeake Bay Program, and from other studies, is summarized in
Appendix B.  Of note are studies of the Cu and Zn in oysters and sediments
of the James and Rappahannock Rivers (Huggett et al. 1974a) that indicate
differences in concentration gradients of the metals between sediments and
oysters.  Additionally, Carpenter et al. (1975) revealed marked temporal
                                276

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                                                                                   I
variations of the dissolved and suspended metals,  Fe,  Mn,  and  Zn,                   •
discharged over an annual cycle by the Susquehanna River.   Our studies              •
support these findings as discussed in Section 2.   Villa and Johnson (1974)
and Johnson and Villa (1976) reported high concentrations  of metals  in
Baltimore Harbor and the Elizabeth River.  By using a  mass balance of              •
metals for Northern Chesapeake Bay, Helz (1976)  found  that at  least  half  of         ™
the Cd, Cr, Cu, and Pb input comes from human sources.  Further assessment
of contributions from human sources is presented in Section 2.  Goldberg  et         1^
al. (1978a), in a study of northern and central  Chesapeake Bay, revealed            J|
anthropogenic fluxes of metal concentrations in  upper  parts of sediment
cores.  Since this study showed that sediment puts material into the               ซ
system, we assessed sediments as a source.  (See Section 2 for discussion          •
of our results).  The status of knowledge on biological  effects of metals
is presented by Frazier 1972, Cronin et al.  1974,  Hansen et al. 1974, and
Tsai et al. 1979.  These studies indicate a biological toxicity problem             I
that was cursorily studied by the GBP (see Section 6).                             m
    Prior information on synthetic organic compounds in the Bay is scant.
Many synthetic compounds have been only newly created, with the necessary          m
analytical instruments to detect them only recently developed.  Of note             •
(Appendix C) is the EPA National Estuarine Monitoring  Program  between 1965
and 1972, utilizing oysters (Munson and Huggett  1972).  Additionally,
Munson (1973) found that Chester River bed sediments,  suspended sediment,          V
and shellfish stocks contained chlorinated hydrocarbons  derived from               9
Chesapeake Bay.  The Upper Bay Survey (Munson 1975) provided data  on
chlorinated hydrocarbon (PCBs, Chlordane, and DDT) sources and                     ~V
concentrations in suspended material and bed sediments as  well as  in               J
shellfish and zooplankton.  This study gave insights into  routes and rates
of transfer.  Section 2 of this paper expands on this  information.  A              _
consolidated listing of toxicants found in Chesapeake  biota, water,  and             M
sediment, and a listing of toxicant data files is  provided by  CRC  (1978).
The intensive studies of Kepone in the James Estuary after 1975 provide
detailed data for a single toxicant in a single  tributary  estuary.  They            V
cover studies of biota (Roberts and Bendl 1980,  Huggett  et al. 1980,               •
Huggett and Bender 1980) and sediments (Trotman  and Nichols 1978,  Lunsford
1981, Nichols et al. 1979).                                                        •
    Brush's (1974) inventory of sewage treatment plants  lists  information          A
on sources of toxicants.  Additionally, the EPA-States National Pollutant
Discharge Elimination System (NPDES), which began in 1973, contains                 _
extensive file data on metals and a few organic  compounds  discharged from          •
point sources such as industrial effluents and sewage  treatment plants.             ™
    In 1978 the GBP initiated research on toxic  substances, aiming to
provide new information and the data base necessary to manage  toxic  inputs          V
to the Bay.  It is the first comprehensive effort  to address problems of            |
potentially toxic substances in the Bay on a regional  scale.  Specifically,
we attempted to:                                                                   mm

    o    determine the present distribution and  concentration  of selected
         toxic substances in Bay sediments, water, and biota;
    o    assess the present input rates of potentially toxic substances  to           •
         the Bay, their location, and composition;                                 •
    o    identify the major transport paths for toxic  substances,  their
         chemical behavior, and sites of accumulation; and                          •
                                  277
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    o    determine the impacts of potentially toxic substances  on the Bay
         ecosystem.

    The chief studies were of four main types:

    (l) Baseline Inventory
         An assessment of the spatial distribution of sediments,  biota,
         water characteristics, and toxic substances, (what toxic
         substances are present? where are they located?)  and in what form
         or state (organic, inorganic, dissolved,  particulate?) (Are they a
         problem?)

    (2) Source Assessment
         An identification of sources and estimation of the potential toxic
         inputs discharged by industry, sewage treatment plants,  and the
         atmosphere.

    (3) Behavior and Fate
         An assessment of the mechanisms and routes of transport, sites  of
         accumulation, chemical behavior, and likely biological impacts.

    (4) Synthesis
         A summary of research findings and integration of toxic substances
         with system components.

    The program elements are interrelated scientifically by treating the
Bay as a geochemical system with reservoirs.  Sources, sinks, and pathways
of material transports (such as air, water, and sediments) are the
principal reservoirs inventoried; dissolved materials and biota are the
main interacting components.  As toxic substances are transferred between
reservoirs and components, and from sources to sinks, they proceed along
characteristic pathways, undergo transformation,  and accumulate in viable
and sedimentary constituents.
    Research plans focused on toxic substances in the sediment  reservoir,
because toxicants have a great affinity for fine-grained sediment (which
has a large surface area for sorption per unit mass).  Levels in the water
column may, in some cases, be important, but our  work concentrated on
sediment reservoirs because toxicants have a long residence time in
sediments, build up to high concentrations, and are easily detected.
Although toxic substances discharged in dissolved form can have a direct
impact, their effect is believed to be short-lived because of rapid water
movement and constant dilution.  Consequently, sediments have a longer
residence time in the Bay than dissolved substances.  Thus, they can build
up high concentrations of toxicants.
    Growth of the region has increased the supply of sediment delivered  to
the Bay and, when combined with toxic substances,  poses a significant
problem to the Bay environment.  Clearing land for agriculture  and
development has accelerated watershed erosion (Wolman 1967) and increased
loads of suspended sediment (Schubel and Meade 1974).  Suspended sediment
creates turbidity which can decrease light penetration and adversely affect
aquatic plants and primary production.  As sediment fills channels and
harbors, it creates a need for dredging and for disposal of contaminated
sediment.
                                 278

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    As in the previous part on nutrient enrichment, this section was              •
written around several questions relevant to those interested in managing         jj^
water quality of the Bay.  The three basic questions addressed in this
paper are:                                                                        ซ

    Is there a toxic chemical problem in the Bay?                                 ~
    What is the distribution of toxic chemicals in the Bay?
    What are the sources and loadings of pollutants of concern?                   1m

A more detailed list of these questions, with their answers,  appears as the
final section of this paper.  The answers are drawn from the  paper and            ซ
serve as a summary of the technical material from a manager's perspective.        •
They should concisely support Section 6, Conclusions and Research Needs.
                                     279
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                                  SECTION 2

                       FINDINGS FROM STUDIES ON METALS
    This chapter explains the results from CBP research on sources  of
metals to the Bay and their distribution and concentration in the estuary.
The first part on sources discusses inputs of metals from industries  and
publicly owned treatment works (POTWs),  the atmosphere, urban runoff, and
three principal tributaries of Chesapeake Bay.  The remaining sections
summarize results from CBP studies on the concentration of metals in  the
Bay.  Once in the estuary, the behavior of metals depends on how they
respond to the Bay's chemical, biological, and physical processes.   Some
metals, for example, will become dissolved in the estuarine water.  Others
will associate with suspended matter, while certain amounts and types will
be found in bottom sediments and interstitial water.  This section  deals
with metals partitioned in all of their phases.
SOURCES

    The CBP initiated studies to assess the input of metals from several
major sources to the Bay.  These sources are:   industries and POTWs,
atmospheric deposition,  urban runoff, and three of the Bay's principal
tributaries.  Approximate loadings were computed for these sources to
provide an estimate of the relative contributions each source makes.

Industries and POTWs Below the Fall Line

    Rates of metal input from point sources in the Bay drainage basin were
estimated for industries and POTWs below the fall line from data obtained
between 1974 and 1980.  Information from the National Enforcement
Investigations Center (NEIC) of the U.S. Environmental Protection Agency
(EPA) was used to place in priority the toxic dischargers from the
approximately 5000 point source dischargers in the entire Chesapeake Bay
basin.  It was determined that there are 1000 major toxic dischargers, of
which 122 are located below the fall line.  For these 122 industries,
loading estimates were computed for selected metals we found in relatively
high concentrations in Bay sediments.
    Concentration of metals in various industrial effluents was obtained
from EPA effluent sampling data from Resources for the Future in the
"Pollution Matrix Lookup Routine."  Concentration values were assigned
based on the industry's Standard Industrial Classification (SIC) code.  The
discharge rates for each industry were obtained from data collected for an
EPA project referred to as the "Industrial Facilities Discharger File"
(IFD).  Loadings of metals in metric tons per year were computed by
multiplying the effluent discharge rate (in millions of gallons per day
[MGD]) by the concentration of the various metals milligrams per liter
(mg/L), applying the appropriate conversion factors.  However, when
assigning effluent concentration values, the industries discharging cooling
water were assigned concentrations representative of cooling water, not
waste water.  Those industries discharging cooling water and process
                                 280

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waste water were assigned concentration values approximately 85 percent
less than those industries in the same SIC code but discharging all process
waste water.
    Loadings from POTWs were computed by multiplying discharge flow rates
(MGD),  obtained from the EPA 1980 Needs Survey, by concentration values
obtained from results of pilot-scale studies conducted by the EPA Municipal
Environmental Research Laboratory (MERL) (Petrasek 1980).  Discharge flow
rates are compiled in the Needs Survey for use in Congressional allotment
of construction grant funds to upgrade or expand existing POTWs.
    Computation of loadings showed that discharge of metals is greatest in
areas of high industrial activity and large population centers.  With the
exception of Fe, all of the metals listed in Table 1 have established
criteria levels.  These levels vary for each metal and for chronic versus
acute toxicity.  In localized areas, such as Baltimore Harbor and Elizabeth
River,  the quantities of metals discharged create situations with a strong
potential for high aquatic toxicity.  For example, in Baltimore Harbor,
metals are discharged in moderate amounts; but because of low flushing
rates (10 percent renewal rate) (Sinex and Helz, unpublished), these metals
concentrate in Harbor waters.  Although we have no data to demonstrate the
severity of the problem in the water column, Sinex and Helz (unpublished)
have shown from bottom sediment samples that the bulk of metals discharged
in the Baltimore Harbor does, in fact, remain in the Harbor.
    The distribution of metal loadings for POTWs and industries (Table l)
shows that discharges of Cd, Cr, Cu, Fe, and Zn from POTWs and industries
in Baltimore County and Baltimore City far exceed those from other
counties.  Lead from POTWs in Baltimore City is higher than in other
counties.  Substantial inputs from POTWs are also noted for Cr, Fe, and Zn
in Richmond City, Norfolk City, and Hopewell City.  Lead is notably large
in industrial discharge from Louisa County.  Taken as a whole, industrial
loadings are more than twice as large as treatment plant loadings.

Atmospheric Sources

    Pollutants from the atmosphere can deposit directly as dryfall (dust)
and as dissolved constitutents in precipitation (rain, snow, hail).
Because we lacked data on the dryfall component of atmospheric deposition,
no estimate of dryfall loading to the Bay is made in this section.
However, Lazrus et al. (1970) and Davis and Galloway (1981) have done some
work on dryfall atmospheric deposition of metals.  Lazrus et al. (1970)
showed that the deposition of metals from the atmosphere varies by a factor
of three or less between North Carolina and Northern Virginia.  Thus, the
atmospheric deposition over the Bay is probably fairly uniform.  Based on a
residence time of 4.7 days for small aerosols (particles < 1 u) and a
predominantly easterly air flow, Davis and Galloway (1981) revealed that
atmospheric contaminants may reach the Bay from industrialized areas of the
midwest.  Deposits in industrialized areas, such as Baltimore, consist of
heavy particulates that settle out rapidly, as well as small aerosols that
rain out in the vicinity of the city.  Thus, the concentration of metals  in
dryfall around Baltimore decreases with distance from the city (Baltimore
Regional Planning Council, unpublished data), but such industrial centers
constitute only a small percentage of the Bay's area.
    CBP funded projects investigated atmospheric inputs to the Bay from
                                 282

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precipitation.  Two sources were used to evaluate atmospheric loads —
storm data from the Maryland Geological Survey and marsh cores.  Data from
the Maryland Geological Survey's sampling of six storm events from April to
September 1981 were used to compute atmospheric loadings listed in Table
2.  Because the areal variability of the deposition rate from each storm
could not be determined at this time, we developed loading estimates that
assume uniform concentrations over the entire Bay.  Omitted from these
estimates are dryfall loading rates and deposition that occur on the land
surface in the drainage basins, eventually reaching the Bay or tributaries
from surface runoff.  Because of these limitations, the values presented in
Table 2 are conservative estimates of total atmospheric deposition.

TABLE 2.  ATMOSPHERIC INPUT OF SELECTED METALS FROM WETFALL TO CHESAPEAKE
          BAY AND TRIBUTARIES
Metals
  Volume1-
  Weighted
Concentration
   (ug/g)
  Main Bay2
(metric tons/
   year)
Main Bay and
Tributaries^
(metric tons/
   year)







Cd
Cu
Fe
Mn
Ni
Pb
Zn
0.23
2.20
6.85
1.77
1.95
2.66
65.20
2
16
50
13
14
19
467
3
28
87
22
25
34
825

1
2
3
Based on
Maryland
Surface
Surface
sampling from six storm events. Data from
Geological Survey (Conkwright et al. 1982).
area of Main Bay = 6,500 km^.
area of Bay & Tributaries = 11,500 km^ •
    Loadings computed using average annual precipitation of
    1.1 meters.

    Results from these studies show that quantities of metals entering Bay
waters from atmospheric deposition are significant.  The concentrations of
metals i ,1 the atmosphere are proportional to the total mass of the metals
released into the atmosphere from fossil fuel combustion, manufacturing
processe.3, and many other anthropogenic and natural processes.  The input of
Zn, as shown in Table 2, is high because of its high emissions from fossil
fuel combustion and other manufacturing processes like plating and cement
production (Forstner and Wittman 1979).  The total load of Zn from the
atmosphere is at least double the amount from point source (Table 1) .   This
suggests that some of the remote areas of the Bay, where anthropogenic
contamination is assumed to be negligible are, in fact, areas receiving heavy
inputs of metals, especially Zn.  Other areas receiving high amounts of
                                 283
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metals must also absorb elevated levels from the atmosphere,  thereby worsening
the problem.
    Marsh deposits can record the atmospheric flux of trace metals deposited
over time, thus providing another estimate of atmospheric input.  The surface
of the high marsh, Spartina patens,  which is exposed to the atmosphere 95
percent of the time, retains most all atmospheric inputs.  Although marsh
cores from the Bay are scarce, McCaffrey and Thomson (1980)  can estimate the
atmospheric flux to the Bay from another core from Farm River Marsh, in Long
Island Sound, Connecticut.  In the Farm River Marsh core, all of the metals
are assumed to have been deposited from the atmosphere.  The concentration of
these metals (Cu, Pb,  and Zn) from the marsh samples was divided by the
concentration of 210pjj present in the sample.  All of the 210pb in t^e
marsh samples is assumed to have been deposited from the atmosphere (Helz et
al. 1981).  The metal to 210p^ ratio from the marsh core is then assumed to
be similar for the Helz cores, because the deposition rate between Long Island
and the Bay is probably nearly the same.  Therefore, by knowing ^lOp^
concentrations in the Chesapeake cores, and applying the ratio from the marsh
core, an estimate of the atmospheric contribution of these metals can be made.
    In the northern Bay, core 4 (Table 3) shows that approximately 10 percent
of the Cu (Cu/210Pb  Cu) and five percent of Zn (Zn/210Pb  Zn) is supplied
from the atmosphere.  However, in other cores from the central Bay (not shown)
about 25 percent of the Cu and 13 percent of the Zn is of atmospheric origin.
Consequently, the atmosphere becomes an important source in zones distant from
sources of water pollution.  When atmospheric and water pollution occur
concurrently, the trend of "excess"  metal over the background for the marsh,
representing the atmospheric flux, is similar to those of Bay sediments as
shown in Figure 1.  Thus, atmospheric sources contribute to the increase of
excess metals with time.
    The trend, observed in Figure 1  for Zn in core 4 and in the Farm River
marsh core, shows that Zn appears to be decreasing from a maximum value
occurring around 1930 to 1940.  The  recent decrease could be due to an
alteration in manufacturing processes or shifts in fossil fuel consumption
(burning more oil instead of coal),  thereby releasing less Zn to the
atmosphere.
                                  284

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1
1
1
COPPER ZINC •
//a/a u Q /a ^
f^ Tf * 9 f\ Tf if
0 50 100 150 200 0 50 100 150 200 _
1980-




1940-

1900-

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•.• ::> ' (SOU
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*A

•''''••.i-y *
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l i l 1 •
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:i:";-::;-:=::t:f S:v.^
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: :' -.'::•' •• ' ' :;'•:• :; •'•:;:. . ••:::•• • :;:: \ + •
<:•.-• ,.:•:.-. ••::;:;.:.'-:;:::, -•:. ' j/
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.-• . /.•. . •'••'• ':'•: :'•:' ' :'|>>->*\). •
'^\ ":';.:::-. f*Z |
'•'•" ' 'J^ X -dM
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+
1
1
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o Chesapeake Bay
Core 4
+ + Farm River Marsh, w
Conn.
1
1
Figure 1. Graph of age versus metal content of Cu and Zn showing ป
historical increase of "excess" metal concentration in
Chesapeake Bay core 4 (Helz et al. 1981), by comparison •
to Farm River Marsh concentrations (McCaffrey and |
Thomson 1980).
1
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285 m

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TABLE 3. TOTAL EXCESS METALS IN CHESAPEAKE BAY CORES CONTRASTED WITH FARM
         RIVER MARSH

Core
4
18
60
Farm
210Pb Standing
Crop (dpm cm-2)2
7
10.5
10.0
River Marshl
Cu
(ug cm-2)
793
630
644

Zn
(ug cm-2)
3000
1500
1500

Cu/210pb
113
60
64
13
Zn/210pb
428
142
150
19

1From Benniger (1978).
     cm~2 - decays per minute per square centimeter.
Urban Runoff

   As previously discussed, the deposition of airborne pollutants to the Bay's
surface may be an important transport mechanism.  Another pathway by which
atmospheric pollutants enter the Bay is urban runoff.  Some rainwater (and
dust) deposited in urban areas eventually reaches the Bay.  This transport is
facilitated by the high percentage of paved surface area in urban regions.
Flowing over the roads and other impervious and pervious surfaces,  runoff
accumulates certain metals in dissolved and particulate phases,  notably Pb
from the combustion of leaded gasoline, Zn from the abrasion of tires,  and Cu
and Cr from automobile brake shoes.
   Although urban runoff is usually considered a nonpoint source, on a
Bay-wide scale, loadings from the three major cities in the Bay area are of
sufficient magnitude to represent major localized point sources.  Table 4
shows annual loadings of metals from Baltimore, Hampton Roads,  and  Washington,
DC runoff.  Loadings were computed from data supplied by Hartigan (October 21,
1981, memorandum).  Concentrations of metals in runoff were derived by
averaging results from runoff data collected during the Metropolitan
Washington NURP study and an early 208 monitoring study in the  Occoquan River
and Four Mile Run basins of Northern Virginia.  Surface runoff  volumes  were
obtained by assuming that soils are sandy loam and by computing values  for the
various land use categories based on 1967 hourly rainfall record (rain  gage at
Washington National Airport) .
   The loading values listed in Table 4 show that urban runoff  is a
significant source of metals.  Metals exhibiting the highest loadings are Fe,
Pb , and Zn.  Iron is not considered a toxic metal; loading values are included
only for comparison.  The high Pb and Zn values reflect local sources of these
metals such as automobile exhaust, incinerators, refuse, and other  urban
activities that generate dust, gases, and other noxious by-products.  Since
rain is the major component of runoff, the concentrations of metals in  rain
and other forms of precipitation will also cause high metal loadings in urban
runoff.
                                 236

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                                                                                    I

Metro Area
Baltimore
Norfolk/
Newport News/
Hampton
Washington,
DC
Total
Cd
5


1

1
7
Cr
3


4

4
11
Cu
3


2

4
9
Fe
291


213

473
977
Mn
5


3

7
15
Ni
6


4

10
20
Pb
3.5


26

50
111
Zn
19


15

29
63

River Sources
 TABLE 4   URBAN RUNOFF LOADINGS FROM THREE MAJOR METROPOLITAN AREAS OF              I
          CHESAPEAKE  BAY  (AREA VALUES IN METRIC TONS/YEAR)


                                                                                    I


                                                                                    I


                                                                                    I


                                                                                    I


                                                                                    I
    An estimate of annual loadings of selected metals at the fall line of
 three rivers, the Susquehanna, Potomac, and James, was derived from samples         —
 collected approximately bi-weekly to monthly by the U.S. Geological Survey          •
 between October 1978 and April 1981 (Lang and Grason, unpublished).
 Loading values were computed, using one of the methods described below.

 Prediction Model —                                                                  0
    Various mathematical models were used to fit a relationship between
 concentration (C) and flow (Q) or loading rate (LR) and flow.  The various          •
 models used were as follows:   C versus Q, ln(C) versus Q,  C versus ln(Q) ,            •
 ln(C) versus ln(Q) , C/Q versus 1/Q, ln(C/Q) versus 1/Q, C/Q versus ln(l/Q),
 ln(C/Q) versus 1/Q, LR versus Q,  ln(LR) versus Q,  LR versus ln(Q), and              _
 ln(LR) versus ln(Q) .  A concentration and/or loading rate was then computed         •
 for each day, using the best model and observed daily flow rates.  These            ™
 daily loadings were then summed for the total annual loading.


    To obtain loadings using this method, a flow weighted,  mean daily
 concentration was first calculated as follows:                                       •
                                                                                    ง
                   cmean = i ^
                                  nst                                               M
This value was then multiplied by mean daily flow to obtain a daily                 •
loading.  Daily loadings for each month were then averaged to give an
averge daily loading for that month.  These averages were then multiplied
by the number of days in the month to give a monthly loading.                       •
    The monthly loadings were averaged to give an average monthly loading.           9
Where no samples were taken in a month, the monthly average was used for
these months, and the monthly loadings were summed to give a yearly loading.         •

Mean or Median Value from Sampling Data Applied to Long-Term Mean Annual
Flow —
    This method involved using the mean or median value of the various              H
parameters as reported by the USGS (Lang and Grason 1980) and the long-term         ™
mean annual flow to compute the loadings.
                                 287
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    The loadings and the computation method used for each metal are listed
in Table 5(a).  The discharge flows for these years and the long-term mean
annual flows are listed in Table 5(b) .   The flow rates for 1979 were
significantly above normal for all three rivers and, for 1980, were
somewhat less than normal except for the James which was approximately ten
percent higher than the long—term mean annual flow.  Therefore, the
computed average loading for these years is probably slightly higher than
normal.
TABLE 5(a).
ESTIMATED AVERAGE ANNUAL LOADINGS FOR VARIOUS METALS FROM THE

MAJOR TRIBUTARIES OF CHESAPEAKE BAY FOR 1979-1980 PERIOD*

(VALUES IN METRIC TONS/YEAR) (FROM LANG AND GRASON 1980)

Parameter
Al-D
Al-S
Al-T
As-T
Cd-T
Co-T
Cr-T
Cu-T
Fe-D
Fe-S
Hg-T
Mg-D
Mn-D
Mn-S
Mn-T
Ni-T
Pb-T
Zn-T
Susquehanna
@ Conowingo Dam
6,509
156,061
161,618
82
65
59
383
390
1,844
192,422
23
232
7,552
7,326
14,469
229
174
837
(2)
(2)
(2)
(2)
(3)
(2)
(3)
(2)
(1)
(2)
(2)
(2)
(2)
(2)
(2)
(1)
(3)
(1)
Potomac
@ Chain Bridge
1,724
36,061
37,626
13
4
39
105
86
839
76,227
-
61
86
1,929
1,933
109
102
322
(2)
(2)
(2)
(2)
(2)
(1)
(1)
(1)
(2)
(2)

(1)
(3)
(3)
(3)
(1)
(3)
(1)
James
@ Cartersville, VA Totals
2,631
30,890
33,884
20
6
48
63
41
567
27,783
6
31
104
2,277
2,327
64
31
285
(2)
(2)
(2)
(1)
(3)
(2)
(3)
(1)
(1)
(1)
(2)
(2)
(2)
(2)
(2)
(1)
(3)
(1)
10,864
223,012
233,128
115
75
146
551
517
3,250
296,432
29
324
7,742
11,532
19,229
402
307
1,444

*Values listed represent the mean of 1979 and 1980 calender year loadings.


(1)  Computed using a model

(2)  Computed using sum of averages method
(3)  Computed using the reported mean or median value applied against the
     long term mean annual flow


D - Dissolved
S - Suspended
T - Total
                                288

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Susquehanna
Potomac
James
1979
Calendar Year
(ft3 sec-1)
52,200 (+34%)2
20,400 (+79%)
12,000 (+70%)
1980
Calendar Year
Cft3 sec-1)
28,400 (-27%)
11,000 (- 3%)
7,790 (+10%)
Long 'Term
Average
(ft3 sec-1)
38,900
11,400
7,050

                                                                                   I
                                                                                   I
TABLE 5(b)5  ANNUAL AND LONG-TERM MEAN ANNUAL FLOWS FOR THE SUSQUEHANNA,
            POTOMAC, AND JAMES RIVERS1                                             g
                                                                                   I
                                                                                   I
                                                                                   I
iData from U.S. Geological Survey, unpublished                                      ^
^Values in parenthesis represent the percent difference from the long-term          •
 mean annual flow.


    Table 5(a) lists loading values for 13 metals of which several — Al,            ™
Fe, Mg, Mn — are not considered toxic.  Some of these metals, such as Al
and Fe, are contributed primarily from natural erosion processes and cannot         •
indicate pollution.  All of the metals in this list occur in crustal                (
material and, therefore, are naturally found in rivers.  This makes it
difficult to determine the natural from the anthropogenic contributions, a          M
subject more fully discussed in Section 4.  It is important to mention,             •
however, that even though some metals are contained in naturally-occurring
soil and crustal material, the rate of this sediment entering the river may
be dramatically enhanced by farming and other rural and urban activities.            •
    Of importance to note in Table 5(a) are the high loadings for Cr,  Cu,            w
and Zn.  These values reflect contributions from point and nonpoint
sources, erosion, and other sources.  Zinc values are particularly high and         •
may be the direct result of the observed high concentrations of Zn in the           H
precipiation that falls on these drainage basins.  Of the three rivers, the
Susquehanna produces the highest loadings, primarily because of the higher          _
flows in this river.                                                                I
    Concentrations of total metal content in the rivers vary with total             ™
suspended material and with river flow.  As shown in Figure 2, the
concentration of suspended Fe at high inflow is more than 20 times the              II
concentration at low inflow, and Mn is more than 15 times the concentration         •
at low inflow.  Some metals, like Mn, also exhibit seasonal changes in
partitioning between dissolved particulate concentrations (Figure 2).                
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         o
         CD
         O>
         cn
                        (a)  RIVER DISCHARGE
                         128            SUSQUEHANNA
 8-


 6-


 4-


 2-
                                                 TIME
                                                 SERIES
                            LONGITUDINAL  SECTIONS	.—
               o 13,400
               O ~1
               6-
60O-


400:


200:
         T I  I  I

           I4.0OO
         n  ii  i  T  i  r  i




      (b)  IRON,

              SUSPENDED
                                                     4700
                                                     TOTAL
  (c) MANGANESE


JTOTAL DISSOLVED
             SUSPENDED
                   T—i—i—T~n—i—i—i—i—i—i—i—i^ i  i—i—i—i
                   (JFMAMJ vlASONQiJ FMAMi

                   !         1979           !    1980  !
Figure  2.  Temporal variations of:  (a)  Susquehanna River discharge at
          Conowingo Dam,  and corresponding  (b) Fe, and  (c) Mn
          concentrations,  dissolved,  suspended, and total.  Data  from
          Lang and Grason (1980) bused  m instantaneous measurements
          and samples at peak inflows.
                                         290

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Cd
Co
Cr
Cu
Fe
Mn
Ni
Zn
2
20
220
106
36,500
6,100
150
570
2
90
50
100
40,000
5,000
200
600
0
-78
+340
+6
-9
+22
-25
-5

                                                                                   I
                                                                                   I
approximately 300 percent higher in the 1980 estimates than in the
1965-1966 estimates.                                                               M
    Comparison of the loadings from the three rivers in Table 5(a)                 •
indicates that the Susquehanna contributes a greater proportion of metals
than the Potomac or James.  To provide an estimate of the relative yield
(or load per unit area) from these river basins, loading rate factors were         •
computed by dividing the loadings listed in Table 4 by the area of the             w
drainage basin above the fall line for each river system.  These values are
listed in Table 5(d) .  Generally, the Susquehanna appears to be no more            •
enriched than the Potomac or James.  Although certain metals are more              JJ
enriched in one river system compared to the other two, the differences are
significant for only several metals and may be largely explained by errors         _
in sampling or loading computation.                                                •

TABLE 5(c).  COMPARISON OF COMPUTED LOADINGS FOR THE SUSQUEHANNA RIVER WITH
             THOSE OF CARPENTER! (LOADINGS IN METRIC TONS/YEAR)
                                                                                    •
               1980                  Annual Loadings         Percent Difference     ^
       Computed Loadings with     Reported by Carpenter2       From Carpenter       I
Metal Flow = 28,400 ft3 sec"1     Flow = 28,012 ft3 sec'1                (%)        *

                                                                                    I
                                                                                    I

                                                                                    I
^Carpenter, J. H., W. L. Bradford, and V. Grant (1975).                             W
^Sampled approximately one mile downstream from Conowingo dam every week
 for the period of April 1965 through August 1966.                                  Bj

    Although rivers are a major source of metals,  it is not known what
proportion of these loadings enter the Bay.  Monitoring on the Susquehanna
generated loading values for the river just prior  to discharge into the             •
Bay, but the James, Potomac, and many other tributaries discharge into              9
fresh water, tidal, and brackish-water reaches of  substantial length.
    Prior studies of eight Bay tributaries indicate that the bulk of                •
suspended sediment is trapped within the tributaries — for example, in the           J|
Back River (Helz et al. 1975), the Chester (Palmer 1974), the Choptank
(Yarbro 1981), the Patuxent (Keefe et al. 1976), the Rappahannock (Nichols          .
1977), and the James (Nichols 1972, O'Connor 1981).  Entrapment of sediment         I
is recorded either by direct measurements of suspended sediment transport,
or by historical shoaling rates with an evaluation of these rates in
relation to inputs of suspended sediment from different sources.                    V
                                  291
                                                                                    I
                                                                                    I

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TABLE 5(d).
METAL LOADING RATE FACTORS FOR THE SUSQUEHANNA, POTOMAC, AND

JAMES RIVER DRAINAGE BASINS* (VALUES IN METRIC TONS/KM2)

Metal
Al-D
Al-S
Al-T
As-T
Cd-T
Co-T
Cr-T
Cu-T
Fe-D
Fe-S
Hg-T
Mg-D
Mn-D
Mn-S
Mn-T
Ni-T
Pb-T
Zn-T
Basin Area (km2)
Susquehanna
240
5,759
5,964
3
2
2
14
14
68
7,110
1
9
279
270
534
8
6
31
27,100
Potomac
149
3,119
5,255
1
1
3
9
7
73
6,594

5
7
167
167
9
9
28
11,560
James
420
4,937
5,415
3
1
8
10
7
91
4,440
1
5
17
364
372
10
5
46
6,257

* Values computed by dividing loadings listed in Table 5(a) by the area of

  the drainage basin above the USGS monitoring station.


    The ability of these rivers to trap river-borne sediment was determined

by calculating a capacity inflow ratio, using intertidal volume for

capacity, and potential inflow (drainage area times annual precipitation)

for inflow assuming all precipitation is runoff.  As indicated in Table 6,

tributary estuaries such as the Rappahannock and Choptank act as very
efficient sediment traps.  Therefore, if most of the sediment is trapped in
the estuarine portion of these rivers, then the bulk of river-borne

toxicants that are adsorbed to the sediment are also likely trapped.

Despite the high efficiency of these rivers to trap sediment, some sediment

will escape, especially during storms.  At such times, these rivers and

other similar areas should be monitored for exceptionally high levels of
toxicants.
                                 292

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TABLE 6.  DATA FOR CAPACITY/INFLOW RATIOS AND PERCENTAGE OF SUSPENDED
          SEDIMENT TRAPPED
    System
Capacity/Inflow
Sed.  Trapped
     Source
Rappahannock
Choptank
Susquehanna
 - Northern
Chesapeake Bay
      0.7
      2.0
      0.04
    90%
    92%
    75%
Nichols (1977)
Yarbro  (1981)
Biggs   (1970)
    A summary of total metal influx to Chesapeake Bay and its tributaries
from different natural and anthropogenic sources is presented in Table 7.
The estimates are products of two quantities, average metal concentration
and rate of discharge.  Accuracy of the data varies with the number of
measurements per unit time, seasonal variations in constituent composition,
and many other factors.  This table shows that the sum of industrial and
municipal wastewater loadings (point sources) represents a major
contribution of metals to the Bay.  Rivers are the only other source that
exceed the point sources.  However, the loadings from rivers actually
represent a combination of the other sources that discharge into these
rivers above the point where loadings were estimated.  That is, the
river-loading estimates contain some fraction of anthropogenic and natural
contributions and become a pathway for these sources.  From the results
shown in Table 5(d) , it appears that the relative proportions of the metal
sources in these river systems are fairly uniform.  However, because point
sources do contribute to some part of the river loadings and are also one
of  the major sources for the Bay,  this suggests that for most metals, point
sources are probably the major source to the Bay, wich loadings from urban
runoff and shoreline erosion significant for some metals.
    The upper Bay and the upper reaches of the Potomac and James estuaries
are critical areas  for fish spawning and other biological activities.  From
our studies of metal concentrations in the Bay (discussed in Section 3 and
Section 4), we know that the Northern Bay does exhibit elevated metal
concentrations.  Therefore, the Susquehanna River represents a major source
of  metals, causing  the Northern Bay to have elevated concentrations.

DISTRIBUTION AND CONCENTRATION OF  DISSOLVED METALS

    Some of  the metals,  entering  the Bay from any one of the sources
previously discussed, will dissolve in the estuarine water.  In this form,
metal data are available for Cd,  Ce, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sc,
Th, U,  and Zn  in surface water and bottom water  for  one  sampling cruise
during  June-July 1979  (Kingston et al. 1982).
    Kingston's data show that a correlation  exists  between metal
concentration  and  salinity for Cr, Mo, and U (Figure 3a, Figure 3b) .
Uranium and  Mo concentrations increase linearly with increasing salinity
and approach average  seawater concentrations at  the  upper end  of the
                                 293
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-
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• ,

^ •
^^ •
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1 1 1 1 !•!•*! *•• 1 VV^l • 1* lo 1 1
0 2 4 6 8 10 12 14 16 18 20 22 24
SALINITY, ppt.
1
1
1
Figure 3. Plot of (a) dissolved Mo content versus salinity, and (b)
1 dissolved Cr content versus salinity for samples from surface
water along the Chesapeake Bay length, June- July, 1979. Data
from Kingston (1982).
1
_ 294
1

-------
•"-Values in parenthesis represent  percent  of total  loading
                                                                                    I
 TABLE  7.   LOADINGS OF METALS FROM THE MAJOR  SOURCES AND PATHWAYS TO                 I
           CHESAPEAKE BAY  (VALUES IN METRIC TONS/YEAR)
                                                                                    I
Source           Cd         Cr        Cu         Fe         Pb         Zn


Industry      178 (66)   200 (19)   190 (22)  2,006 (1)     155 (22)    167 (  6)    |

Municipal                                                                          ^
  Wastewater    6 ( 2)   200 (19)    99 (12)    625 (1)      68 (10)    284 (10)    •

Atmospheric     3 ( 1)     	       28 (  3)     87 (1)      34 (  5)    825 (29)

Urban Runoff    7(2)    10 ( 1)     9(1)    977 (1)     111 (16)     63 (  2)    V

Rivers         75 (28)   551 (53)   517 (59) 199,682 (77)   307 (43)   1444 (50)    m

Shore Erosion   1(1)    83 ( 8)    29 (  3)  57,200 (22)    28 (4)     96 (  3)
                                                                                    I
salinity range.  This trend indicates that marine waters are the source of          •
these metals, and that the concentration gradient is a result of dilution           ฃ
of marine water by river runoff.  It also indicates that these metals are
not significantly involved in chemical or biological processes in the Bay.          ซ
By contrast, Cr concentrations decrease as salinity increases to a value            •
approximating average seawater concentration at the upper end of the
salinity range.  This relationship indicates that river runoff is the major
source of Cr , and that dilution by marine water controls dissolved Cr               I
concentrations in the estuary.  The scatter in the Cr data, however, is             w
much greater (Figure 3b) than that for Mo, possibly indicating the
influence of other processes in addition to dilution by marine waters.              <•
    All of the other dissolved metals investigated, Cd , Ce , Co , Cu ,  Ni , Pb ,         ฃ
and Zn, are significantly affected by processes other than dilution.
Therefore, plots of dissolved metal concentration versus salinity show              ^
little correlation.  Cadmium, Cu ,  Ni, Sn, and Zn tend to decrease in                •
concentration with increasing salinity,  although there is much scatter in
the data.  Differences in metal concentrations in relation to salinity may
arise from varying strength of sources (marine versus freshwater, or                •
others), fluctuating chemical behavior (oxidizing versus reducing,  salinity         m
differences), hydrodynamic mixing  patterns,  and other factors.
    Patterns of enrichment emerge  from plots of the ratio of dissolved              •
metal in surface water to dissolved metal in bottom water,  versus salinity          I
of the surface water (Figure 4).  If surface waters are enriched (contain
elevated concentrations) in a metal, the ratio is greater than one;  if              M
bottom waters are enriched, the ratio is less than one;  if the surface and          •
bottom concentrations are the same, the  ratio is equal to one.   For
example, in Figure 4a, the dissolved-Cu-concentration-in-near-surface-water
samples to dissolved-Cu-concentration-in-near-bottom-water ratios are               B
mostly greater than one, and significantly greater than one in the  10 to 15         W
                                295
                                                                                   I

                                                                                   I

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                                                                                    I


ppt range of salinity values.  This suggests that the mid-Bay (where
salinities range from 10 to 15 ppt) has much higher Cu concentrations in            _
the surface waters,  relative to the bottom waters.  Salinity indicates the          •
•val ^ t~ i vrt* r\s\a i f~ i /~\ n *ป 1 /~\ T*ป cr t~\\ a ฃacซ^'iiov-'\r T.T!"ปO *• & & r* •*<• -i o V^m ^•n f" /*\/•ป /^ i ซ *" o   i^~\ o t* ^ ป~in              ^^"
                                                                                    I

                                                                                    I
relative position along the estuary where enrichment occurs.  The term
enrichment refers to the concentration of the metal in the surface water as
a function of concentration in bottom water.  This ratio does not indicate
absolute concentration and cannot be used as an index of abnormal metal
content.
    Figure 5a compares the ratio of dissolved metal concentration in
surface water to dissolved metal concentration in bottom water, with the
ratio of surface water salinity to bottom-water salinity.  On these plots,
a salinity ratio of one indicates there is no halocline and, therefore,
little or no stratification.  The data displayed in Figure 5 can be divided          •
into four quadrants.  For example, in Figure 5(b), the ratios of                     ™
dissolved-Mo-concentrations-in-near-surface-water samples to
dissolved-Mo-concentrations-in-near-bottom-water samples, appear to fall             •
primarily in the bottom, left-hand quadrant.  This indicates that Bay                |
waters display a tendency for Mo concentrations to be higher in salty,
bottom waters than surface waters.  If the ratio exceeds one, the surface            _
water is more saline; if the ratio is less than one, the bottom water is             •
more saline.  As in the previous graphs,  a metal ratio greater than one              *
indicates surface enrichment, whereas a ratio less than one indicates
bottom enrichment.                                                                   fl
    Plots like those of figure 5b show that Cu, Ni, and Zn are strongly              •
enriched in surface waters, particularly under conditions of strong
halocline development.  Under the same conditions, Co, Cr, and Mo are                •
strongly enriched in bottom waters.  Similar data show that Cd is enriched           M
in low-salinity surface water.  Cobalt shows enrichment in surface waters
of salinity up to approximately eight ppt, and in bottom waters over the
salinity range from eight to 15 ppt.  Chromium is enriched in surface                •
waters up to 15 ppt salinity and in bottom waters from eight to 20 ppt.              ™
Copper, Ni, and Zn are strongly enriched in surface waters from five to 18
ppt.  Uranium is enriched in bottom waters in the range seven to 15 ppt.             •
    Table 8 summarizes univariate statistics for near-bottom and                     ^
near-surface dissolved metal concentrations throughout Chesapeake Bay as
sampled and analyzed by Kingston et al. (1982).  Because of the high                 M
precision and accuracy used in these analyses ,•the information in Table 8            M
represents data generated for the first time for several metals in Bay
waters.  These numbers, then, are "benchwork" values from which to compare
future numbers, and can indicate potential increases or decreases in                 •
contaminated areas.                                                                  9
    The NBS investigations (Kingston et al. 1982) analyzed particulate as
well as the dissolved concentrations in the sample.  This information                •
provides better understanding of how the various metals partition between            M
dissolved and adsorbed phases.  Dissolved metal concentrations are very
important, because this phase is completely biologically available.                  —
Therefore, some of the maximum values shown in Table 8 may be hazardous to           •
aquatic life in Bay waters where these high concentrations are found.                ^
                                 297
                                                                                     I

                                                                                     I

                                                                                     I

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TABLE 8.  SUMMARY OF MEAN AND MEDIAN METAL CONCENTRATIONS AND RANGE
          OF BAY-WIDE VALUES (UG/L) (DATA FROM KINGSTON ET AL.  1982)
          CRUISE OF JUNE-JULY 1979.

Dissolved

Cd
Co
Cr
Cu
Fe
Mn
Mo
Ni
Pb
Sc
Sn
Th
U
Zn
N*
45
102
102
79
102
102
102
102
102
102
9
39
102
102
Mean
0.05
0.07
0.17
0.66
3.12
13.88
3.26
1.21
0.11
0.0006
0.86
0.001
0.93
1.19
Median
0.04
0.05
0.11
0.48
1.63
3.34
2.93
1.15
0.05
0.0005
0.86
0.001
0.88
0.42
Range
0.007-0.101
0.01-0.56
0-1.68
0.15-2.25
0.09-71.67
0-388
0.61-8.68
0.5-2.59
0-1.59
0.0002-0.002
0.31-1.61
-
0.13-2.57
0-11.11

    *N is number of samples treated.
DISTRIBUTION AND CONCENTRATIONS OF METALS IN SUSPENDED MATERIAL


    Chesapeake Bay Program research has shown the distribution of metals in
suspended material displays marked longitudinal and vertical gradients.
Although concentrations were highly variable between samples and surveys,
the mean metal content per gram of material exhibits distinct trends
(Nichols et al. 1981).  Content of the metals, As, Cd, Cu, Pb, Hg, Ni,  Sn,
and Zn, reached a maximum in near-surface suspended material of the central
Bay, shown in Figures 6a, 6b, and 6c.  Because this part of the Bay is  an
area of high biological activity, elevated levels of these metals could
threaten biota there.  The concentrations for these metals were higher  than
farther landward near major sources in the Susquehanna River mouth and
Baltimore Harbor zone.  Particularly high maxima or "hot spots" were
observed for Cu and Cd (Figure 7 and Figure 8).  The mean concentrations
for Cu and Cd were five to 10 times greater than the Susquehanna River
mouth.  Secondary maxima occurred in the main Bay off Baltimore Harbor  for
surface concentrations of Cd, Mn, Ni, Pb, Sn, and Zn (Figure 7 and Figure
8).  High levels of metals at these "hot spots" indicate areas of possible
toxic impacts.
    Metal concentrations were higher in surface and mid-depth suspended
material than near the bottom, a trend resulting in stratified
distributions.  For example, Cu, Ni, Sn, and Zn concentrations were higher
in surface than in near-bottom water in the same zone by a factor of two or
more.  Again, these results indicate where unnatural levels of metals can
occur, with a consequence of increased risk of toxicity.
                                  299
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                                                         ^
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        221918 16  I4l3(l2 II
                                              '• MEAN  CADMIUM u
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-------
Figure 7.





















METALS IN







STATION






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• DISTANCE, km
Distribution of metal
distance along the Bay

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content in surface suspended material with
axis. Median values and range of concentrat
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, 1

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1

1


1


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•
ions m
           from all available observations of Nichols et al.  (1981).   Shaded zone
           indicates magnitude of departure between median values and mean values
           for Fe-corrected average shale, open circles.
                                     301
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                                      METALS IN SUSPENDED MATERIAL

                                               NEAR-BOTTOM
                                 STATION

                    221918 16 14 1312 II  10  9   8   76521
                     CADMIUM 6
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 2

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400


300



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                    ARSENIC
                     MEDIAN
                     COPPER
                         j.72 ' JT3
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                     LEAD
                      280 240  200  160  120  80   40
                             ซ	DISTANCE, km
                                                      STATION

                                         221918 16 14 13 12 II 10  9  8
                                                                              76  5  2
                                      200


                                      100


                                       0

                                      60
                                                          MANGANESE
                                                                           [   ] Departure from
                                                                           1 ..... 1 Average Shole
                                                                   AVERAGE SHALE,
                                                                   F. CORRECTED
                                                          MERCURY
                                                          NICKEL
                                                           TIN
                                                           ZINC
                                          280  240  200  160  120   80  40

                                                      DISTANCE, km
          Figure  8.
     Distribution of metal  content  in near-bottom suspended
     material  with distance along the Bay axis.   Median values and
     range of  concentrations from all available  observations of
     Nichols et  al. (1981).  Shaded  zone indicates magnitude of
     departure between median values  and mean values for
     Fe-corrected average shale, open circles.
                                                302

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    Concentrations of metals in suspended material changed with season.
Seasonal changes were marked by a 10-fold increase in surface Cu
concentrations between March to April and May to August  (Nichols et al.
1981).  Zinc was higher in March to April than at other  times,  whereas Pb
was highest during June.   Table 9(a) summarizes the mean metal
concentrations and range of values at all sample depths  throughout  the Bay
(Nichols et al. 1981).  Table 9(b) , from Kingston et al.  (1982), 'supports
these values.


TABLE 9(a). SUMMARY OF MEAN METAL CONCENTRATIONS AND RANGE OF BAY-WIDE
            VALUES, PER GRAM OF SUSPENDED MATERIAL, LEFT; AND WEIGHT PER
            VOLUME OF SUSPENDED MATERIAL, RIGHT (DATA FROM NICHOLS  ET AL.
            1981) FOR MORE THAN 550 SAMPLES AND 8 CRUISES ALONG THE BAY-
            LENGTH BETWEEN MONTHS OF MARCH AND SEPTEMBER 1979 AND 1980
 Metal
Mean
Metal
Mean
As ug/g
Cd ug/g
Cu ug/g
Fe ug/g
Hg ug/g
Mn ug/g
Ni ug/g
Pb ug/g
Sn ug/g
Zn mg/g
13.00
14.16
127.96
3.11x10?
3.89
2880
95.80
160.30
17.97
750
0.55-100.00
0.12-790.00
9.90-570.00
0.29-17xl07
0.5-59.00
80-46,000
4.80-770.00
21.00-730.00
0.25-290.00
100-7100
As ug/L
Cd ug/L
Cu ug/L
Fe mg/L
Hg ug/L
Mn ug/L
Ni ug/L
Pb ug/L
Sn ug/L
Zn ug/L
0.32
0.14
1.84
88xl05
0.035
65.13
2.00
2.27
0.20
11.02
•^HMB^riMhWB
0.006-5.00
0.003-3.80
0.068-17.00
1.0-1200xl05
0.01-0.47
0.48-1000.00
0.03-34.00
0.10-15.00
0.01-4.80
0.55-94.00

TABLE 9(b).  MEAN, MEDIAN, AND RANGE OF METAL CONTENT FOR ONE CRUISE  ALONG

             THE BAY-LENGTH (JUNE-JULY 1979) (DATA FROM KINGSTON 1982)
                         N*
                     Mean
       Median
              Range
Cd
Co
Cr
Cu
Fe
Mn
Mo
Ni
Pb
Sc
Sn
Th
U
Zn
51
102
102
102
102
102
12
102
96
102
-
100
86
90
0.018
0.24
0.75
0.65
342.45
38.16
0.08
0.57
0.75
0.11
-
0.10
0.029
2.15
0.008
0.06
0.23
0.36
131.50
19.20
0.03
0.27
0.23
0.04
-
0.04
0.012
0.73
0.001-0.11
0.17-2.37
0-5.31
0.1-4.69
14-2911
1.2-349
0.01-0.25
0.03-5
0.01-7.3
0.003-0.93
-
0.002-0.68
0.002-0.192
0-15.2

          *N is number of samples treated.
                                 303
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                                                                                    I
    Concentrations of metals and other chemical constituents can be                 •
expressed in several ways,  including concentration expressed as weight of
the specific metal per unit weight of suspended material,  and per unit
volume of water.   The expression used depends  on the substance (water or            •
sediment) being analyzed.   Discussion of metal concentrations thus far has           ป
been based on concentrations expressed on a weight per weight basis.
However, when metal distributions reported as  weight per  volume are                 •
examined, the metal concentrations are directly proportional to the                 •
concentration of total suspended material.  Therefore, mean metal
concentrations of As, Fe,  Mn, Ni, Pb, Sn, and  Zn were highest in the  zone           _
of the turbidity maximum where suspended sediment concentrations are                 •
highest (Nichols et al. 1981).  Likewise, near-bottom metal concentrations           •
of most metals were usually higher than surface concentrations, resulting
in stratified distributions.                                                        •
    In addition to seasonal variations, metal  concentrations were highly            0
variable on short-time scales.  For example, concentrations of Cu and Pb
per gram of suspended material from the turbidity maximum zone of the               M
northern Bay, varied more than two-fold over a tidal cycle.  By contrast,           •
Fe, Mn, and Zn varied within relatively narrow limits. These fluctuations
are associted with large fluctuations of suspended material entering  the
Bay, and moderate fluctuations of particle size and organic content as              •
tidal currents resuspended sediment from the bed.  Such short-term (tidal)           •
changes added to long-term (seasonal) variations produce  wide ranges  in
metal content.  These variations must be taken into account for planning            •
metal samplings for monitoring and meaningful  interpretation of data.               •
    Despite the wide spatial and temporal variations of metal
concentrations, many metals correlated statistically with each other,               _
allowing the potential use of one or several as predictors.  For example,           •
from the VIMS cruise series (Nichols et al. 1981), Fe-Mn,  Cu-Zn, and  Ni~Zn,          •
Ni-Fe, and Zn-Fe had r > 0.80.  Many metals from the NBS  cruise (Kingston
et al. 1982) also correlated with each other:   Co, Cr, Fe, Sc, Th, Zn, Cu,           •
Mn, Pb, and Ni with r ~?Q.90.  These associations reflect  the affinity of            V
metals for suspended material through adsorption or uptake, and show  that
many metals display similar behavior.  Metals  like Mo, U,  and Cd did  not            M
correlate, however, because they tend to stay  in solution.  The similar             •
behavior of these metals can be used to predict the occurrence of unknown
concentrations when only one metal is known.  Moreover, Fe was found  useful
as a surrogate element since it is naturally abundant.  Iron also varies            •
within relatively narrow limits throughout the Bay.  Its  use for                    ™
normalizing enrichment factors is demonstrated in a separate section.
    A comparison of the mean metal content of the dissolved fraction  and            •
the corresponding particulate fraction per volume of suspended material             |
[Table 9(c)] reveals several significant trends.  The ratio of dissolved to
total metal content provides an index to the mobility of  the metal, and             ซ
thus its availability to biota.  For example,  Mo and U are dominately in            •
dissolved form in both surface and bottom water, whereas  Co, Fe, Mn,  Pb,
Sc, and Th are dominately in the particulate form.  Note  that Zn displays
much higher percentages in surface water than  in bottom water.  Therefore,           •
samples of surface water alone are not indicative of the  dissolved Zn               ป
content in bottom water.  By contrast, Mn (both particulate and dissolved)
is much higher in bottom water than in surface water in summer.  This trend          •
                                 305
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probably reflects mobilization and release of Mn from central Bay sediments
during summer anoxia.  The index provides an indication of which metals
organisms are exposed to in summer.  Since dissolved metals generally have
a shorter residence time in the Bay than particulate metals,  the index
further predicts that metals like Mo and U will likely escape the Bay
whereas Co, Cr, Fe, Mn, and Sc are most likely retained in the estuary.
The fate of other metals probably varies with natural biochemical and
sedimentological processes native to the Bay.
DISTRIBUTION AND CONCENTRATION OF METALS IN BOTTOM SEDIMENTS

    During the Bay Program, surface sediments were analyzed for As,  Cd,  Co,
Cr, Fe, Hg, Mn, Ni, Pb, and Zn by Helz et al. (1981) and Nichols et  al.
(1981).  All of these metals are more concentrated in the fine fraction
(
-------
 77ฐ 30'
                                 75ฐ 30
38ฐ
45T
36ฐ
45'
     DISTRIBUTION  OF COPPER.ppm
      IN UNFRACTIONATEO SEDIMENT
DISTRIBUTION OF
   COPPER ppm
IN FRACTIONATED SEDIMENT
                                               •  10 00 PPM


                                                  35.00 PPM


                                                  70.00 PPM
  Figure 9.   Distribution of Cu content in  bottom sediments of  (a)  bulk
               bed sediment,  unfractionated,  and (b) the  less than 63 u
               size fraction,  fractionated.   Data fromHelz et al.  (1981).
                                         307
                                      38ฐ
                                      45'
                                      36ฐ
                                      45
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77ฐ
     DISTRIBUTION OFZINC,ppm
      IN UNFRACTIONATEO  SEDIMENT
DISTRIBUTION   OF
      ZINC, ppm

IN FRACTIONATED SEDIMENT
     • 100.00 PPM
  Figure  10.  Distribution of  Zn content  in bottom  sediments  of (a) bulk
               sediment, and  (b)  the less  than 63  u  size fraction.   Data
               from  Helz et al.  (1981).
                                                                                   36ฐ
                                                                                   45'
                                         303

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                                                                                  I
of nutrients and trace elements.   Previous investigations,  Berner (1979)           •
and Bricker and Troups (1975), show a substantial transfer  of trace metals         •
from the sediment to the water column.   The principal vehicle for
transporting this material from the sediment to the overlying water is the
interstitial or pore water (water contained in the sediment).  Many of the         •
constituents of interstitial waters are derived from chemical reactions of         W
water with the solid material of  the sediment.
    The constituents and parameters measured on 97 cores by Hill et al.            •
(1981) and Tyree et al. (1981) are:                                                J

         Na+, K+, NH*, Ca+ + , Mg++, F~,  Cl", N0~,                                    _

         N0~, PO*. SO]T, SO^, HCO*. pH,  pS=, Eh,                                    •
         Conductivity, Fe,  Mn,  and SiO .
                                 309
I
A subset of these cores was analyzed for the trace metals Pb,  Cd,  Cu, and
Zn.  Figure 11 is a graphical presentation of some core data of a                   ซ
representative station.                                                            •
    The transport of dissolved constituents across the sediment-water
interface proceeds in response to concentration differences.  Constituents
migrate from areas of high concentration to more dilute areas  according to         •
Pick's law (Lerman 1979).  Generally, the concentration of nutrients (such         •
as NHJ, P04, and HCOp and trace elements in the interstitial
water exceeds the concentration in the overlying water column.  Thus, the          •
gradient predicts that these materials are transported from the sediment           •
into the water column.
    The chemical sedimentary environment controls the concentration of
constituents in the interstitial water that, in turn, controls the                 •
transport of materials between the water column and sediment,  and  within           ™
the sediment.  Three major chemical sedimentary environments have  been
identified for the main portion of the Bay:  the northern Bay; the central         •
Bay, including upper and lower parts; and the southern Bay, including two          |
subsections (Figure 12).  The chemical environments are classified
according to a set of parameters, which influence and reflect  the  redox            m*
state of the sediment.  These parameters are:  major ionic composition ot          •
the interstitial water; organic carbon content of the sediment; reduced
sulfur content of the sediment; degree of SO^ reduction;  Eh; and the
concentrations of dissolved sulfide species, Fe, Mn, and NHฃ.   The                 •
three environments correspond to Berner's (1981) method of classification          9
of sedimentary environments.
    The northern Bay, as shown in Figure 12, is primarily characterized            •
by:  (1) ratios of the major ion concentrations that differ in comparison          •
to ratios from marine-dominated environments, (2) high organic carbon
content (five to six percent), (3) absence of dissolved sulfide species,           _
(4) complete ( >80 percent) reduction of available SO^, and (5) the                •
most positive Eh values in the Bay.  The primary chracteristics of the             '
central Bay environment are:  (1) intermediate to high organic content (two
to five percent), (2) high concentration of dissolved species, (3) variable        •
degree of S0ฃ reduction between cores, and (4) the most negative Eh in             •
the Bay.  The southern Bay characteristics are:  (1) low organic carbon
(zero to two percent), (2) essentially no S0ฃ reduction (^20 percent),             m
 I

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                                                          310
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Figure 12.  Distribution of chemical sedimentary environments in
            Chesapeake Bay, based on data of Hill and Conkwrighi:
            (1981).
                                   311
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(3) very little detectable NHฃ, and (4) and Eh more positive than the
central Bay, but more negative than the northern Bay.
    Estimates of the transport of material, with respect to the
sediment-water interface, according to the three major chemical sedimentary
environments, are presented in Table 10.  The ranges include seasonal
changes of temperature and salinity, which can markedly effect the chemical
environment.  The fluxes calculated from the concentration gradients
generally indicate:   CD NHฃ,  HCO^, and PC>4 are added to the
overlying water column in the northern and central Bay; (2) Fe and Mn are
transported to the overlying water column in the northern Bay, but
stabilized in the sediments in the central and southern Bay; (3) sediments
contribute sulfide (HS~) to the overlying water of the central Bay, and
(4) PO^ is stabilized in the sediments of the southern Bay.  The trace
metal data indicate that the concentration of the metals in the interstitial

water corresponds to the chemical sedimentary environments, but the
concentration gradient profiles are too complicated for a simple Fick's law
estimate.


TABLE 10  GENERAL ESTIMATED RANGES OF FLUXES DIVIDED ACCORDING TO CHEMICAL
          ENVIRONMENT, VALUES EXPRESSED AS u MOLS/M2/DAY
            NHj


Northern
   Bay   + 50-+700
Central
   Bay   +200-+2000
Southern
   Bay       **
FeH
             Mn"1
HC03
P04
HS"
 20-+70   -100-+60   +800-+3000     +  30-+80         **


-100-  0    -  60-+30   +100-+20,000  - 20-+70  +400-+30.000


- 30—10   -30—10          *       -100—20         *
** - Chemical species below detection limits in these areas
 * - Core data did not fit the simplified model used to estimate the fluxes


Note:    Positive flux values reflect transport into the overlying water
         column; conversely negative values reflect transport into the
         sediment.
                                 312

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                                  SECTION 3

                 FINDINGS FROM STUDIES ON ORGANIC COMPOUNDS
SOURCES
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    The following chapter explains the results from CBP  research on the
distribution and concentration of organic compounds in Chesapeake Bay.
Since polynuclear aromatic compounds (PNAs)  constitute the largest                 •
proportion of toxic synthetic substances entering the Bay (and are also             I
listed on EPA's Pollutant list), much of the CBP research focused on these
compounds.  Other organic compounds, including dieldrin,  terpenoid,  DDT,
and other pesticides were detected.  However, extensive,  quantitative              •
analyses were performed on PNAs.  In this section,  sources of PNAs to the          •
Bay are discussed, followed by results of analyses  on levels of organic
compounds found in bottom sediments and oysters.  The remainder of the              •
chapter interprets these results and considers important  factors affecting         •
the distribution and abundance of organic compounds.
                                                                                   I
    The major source of most of the organic compounds (PNAs)  entering the          B
Bay is the burning of fossil fuels, coal,  oil,  and wood.   Sources  from the         0
Patapsco River also produce compounds made up of substituted  benzenes.
These compounds are also released in industrial processes such as  coal              •
liquefication and gasification (Bjoreth and Dennis 1979,  Cooke and Dennis          •
1980).  Simple substituted aromatic compounds are assembled at high
temperatures (combustion gases) to produce PNA compounds, with different
compounds dependent primarily on the combustion temperature and secondarily        •
on the fuel source.  As indicated by PNA analysis of old  sediments                 •
deposited prior to human's use of fossil fuel,  very few aromatic compounds
were produced by organisms.  Most PNA compounds produced  by combustion              H
differ from those in oil or in the complex polymeric network  of coal  in            J|
that combustion products are generally not substituted.
    Specific sources of PNAs in the Bay region include vehicles burning            M
gasoline and diesel oil, coal and oil fired power plants, coal and oil              I
fired heating industrial plants, oil and wood home heating, and forest  and
refuse fires.  PNA compounds can be transported from the  locations of the
sources to the Bay by air-borne particulates containing PNA (smoke and              •
exhaust), airborne volatile PNAs, water-borne particulates (sediment)              •
containing land runoff and river-borne PNAs, and compounds carried in
solution by rivers and land runoff.  Some small amounts of PNAs are                •
produced in the Bay by the combustion of vessel fuels.                             •
    Within the Bay, large concentrations of PNAs were found at the mouths
of rivers.  Some small subestuaries, like the Elizabeth River and  Baltimore        _
Harbor, with very high industrial actvity and population  density,  can also         •
produce high local PNA concentrations.  PNA compounds are probably                 ™
continuously increasing throughout the Bay, because these many sources
repeatedly produce PNA that is stable over long periods in the Bay water            •
and sediments.  A final source of PNA to the Bay is long-range atmospheric         •
transport by Northern Hemisphere air currents.  Chesapeake Bay is  receiving
air-borne PNA in vapor and particulates introduced in other regions of  the          •
                                 313
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 United States  or  other  Northern  Hemisphere  countries.   Contributions  to  PNA
 concentrations in the Bay  from such  long-range  sources  are  probably uniform
 from place to  place, because  the Bay and  its watershed  area (which together
 serve as  a PNA collection  basin) are small  with respect  to  the areal  extent
 of  single air  masses.
ORGANIC  COMPOUNDS IN BOTTOM  SEDIMENTS

    Analyses of sediment samples collected  for  the Bay Program during the
spring and  fall of  1979 (Bieri et al.  1981) revealed that over 300 organic
compounds were abundant enough to either be identified or given a surrogate
name by  assigning a relative retention  time.  Only a small percentage of
these 300 is not toxic in certain amounts.  In  some samples, the complexity
and abundance of compounds present were so  great  that many individual
species  at  relatively low concentrations were undoubtedly not detected.  It
is, therefore, probable that thousands of compounds were present.  An
example  is  presented in Figure 13, which is an  actual gas chromatogram
showing  individual peaks.  These peaks represent  at least one compound
superimposed on'a background of peaks  from numerous compounds of lower
concentrations.  This is commonly called an unresolved complex mixture.
    The  distribution of organic compounds in bottom sediments (Figure 14)
is presented as bar graphs representing summed  concentrations on a
logarithmic scale of chromatographically resolvable compounds eluting in
the "aromatic" fraction.  The figures show that the highest total
concentrations are encountered in the northern  portion of Chesapeake Bay.
Furthermore, samples from Stations 2, 4, 6, 7,  10, 11, and 12 in the lower
Bay are  almost devoid of these compounds.  However, with the exception of
the fall 1979 sample from Station 9, samples from river mouth stations,
numbers  1, 3, 5, and 8, contained substantial sums—between 100 and 1000
parts per billion (Figure 14).
    To demonstrate that the northern Bay and the river mouths have
unnaturally high levels of organic compounds,  it is necessary to account
for variations in sediment character.  Fine-grained sediments usually
contain higher organic concentrations than coarse sediments,  and this can
explain  some of the anomalous distributions.  In general, sediment samples
from the northern Bay and the major river mouths contained a higher
fraction of silt and clay than elsewhere.  When the samples  are normalized
for silt and clay content the distributions (Figure 15)  change  in the
concentration sums in the northern Bay with the exception of Station 27,
Fall 1979.  In the lower Bay, only Stations 1, 3, 9,  11  and  12  have
increased.  Without further analyses of samples collected within the
subestuaries, it is impossible to determine whether high concentrations  in
sediments collected near the major river mouths were  due to  sediment grain
size or unnaturally high inputs from upstream.  Normalizing  the northern
Bay data did not substantially change the distribution pattern.   With the
exception of the fall  Station 19  sample,  there is a trend of  increasing
concentrations from below the Potomac River mouth toward the  Baltimore
Harbor mouth.  North of Baltimore,  the concentration  sums decrease  and  then
increase to another maximum toward the Susquehanna mouth.  Inside  the
Susquehanna mouth (Station  27)  samples showed  considerable variation
between spring and  fall,  differences that may  arise from variations  of
                                314

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                                       SEDIMENT  SUM  OF  ALL  PEAKS, ppb


                                           \2      i /->3      i /"\^       i /*\*      i ffc
                10"
                    10'
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Figure 14.  Chart of  station locations and bar graph  representing
            concentration suras  of all resolvable peaks  for  organic
            compounds in sediments,  spring samples  1979.  Data from
            Bieri et  al.  (1981).
                                      316

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                              10
                                    SEDIMENT  NORMALIZED TO SILT/CLAY
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Figure 15. chart of station  locations  and bar  graph representing
           concentration sums  (ppb)  of all  resolvable peaks  for
           organic compounds after normalizing for silt and  clay
           content.  Spring  samples,  1979.   Data  from Bieri  et al.  (1981)
                                 317
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                                         SUM OF ALL PEAKS, ppb
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Figure 16.  Chart of station locations and bar graphs representing
           concentration sums of all resolvable peaks for organic
           compounds in oysters, spring samples, 1979 (Bieri et al.
           1981).
                                   318

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                                                                                  I
river flow that scour sediments during high spring flow and deposit
sediment during low fall flow.                                                     •
    The trends for PNAs follow the trends for sums of all concentrations:          Jj
(l) the concentrations are higher in samples from the northern Bay than in
the southern Bay;  (2) in the southern Bay,  highest concentrations are found       _
near river mouths; (3) concentrations tend  to increase up the Bay from the        I
Potomac River mouth toward Baltimore Harbor; and (4)  the Susquehanna River
mouth sediments show considerable variability, but can reach extreme
concentrations.  Data displayed for several individual members of the PNA         •
family show even more clearly that a concentration maximum occurs in the          •
northern Bay in the vicinity of Baltimore Harbor, suggesting that this area
is an important source of PNA families (Bieri et al.  1981)                        •


ORGANIC COMPOUNDS IN OYSTERS

    In addition to sediments, oysters were  also collected during the Bay          •
Program and their tissue was analyzed for organic compounds.  The gas
chromatograms of oyster tissue extracts were much less complex than those         •
of sediments, with the concentration of individual compounds substantially        |
lower.  The graphs for oysters (Figure 16)  show no longitudinal trends like
those in sediments (Bieri et al. 1981). In addition,  methyl esters of fatty       _
acids were present in most samples, as were some ketones.  We hypothesize         I
that many of these compounds have a biogenic or natural origin.  Since they       ™
are often present in higher concentrations  than identified pollutants, the
summed concentrations may not represent a realistic pollutant content in          I
oysters.  Therefore, we examined the number of compounds detected and their       |
distributions rather than their sums.  Altogether, we identified 127
organic compounds.  Oysters collected at the mouth of the James River             m
contained 94 of these compounds.  Oysters collected from Occohonnock Creek        •
(Station 7) contained 27, and those from near Baltimore Harbor (Station 22)
had 24.  The oysters that contained the next highest  numbers of compounds
were from Holland Point (Station 20) with 23 compounds, and Onancock Inlet        I
(Station 10) with 19 compounds.  Although this analysis suggests that these       ซ
areas have the highest contamination of organic compounds in oysters, there
is no apparent reason why oysters from the  Occohonnock Creek, Holland             H
Point, and Onancock Inlet should compare to the James River and Baltimore         |
Harbor, where sediment concentration of organic compounds is greatest.  It
is very likely that salinity or some other physical or chemical factor is         M
influencing the levels of organic compounds in oysters.                           I
    If only the most concentrated compounds are considered, a similar
pattern emerges.  There were 42 compounds detected whose individual
concentrations exceeded 50 ppb.  The samples from the James River mouth           I
(Station 3) contained 29 percent of these.   The next  highest were from            •
Baltimore Harbor  (Station 22) with 24 percent.  These were followed by
Station 10 with 21 percent, Station 20 with 17 percent, and Station 7 with        •
14 percent.  In summary, the following sequence emerges from abundance of         I
compounds:  James River ^Occohonnock Creek">near Baltimore Harbor> Holland
Point7 Onancock Inlet.  For individual compound concentrations greater than
50 ppb:  James River >near Baltimore Harbor "7 Onancock Inlet> Holland Point"?        •
Occohonnock Creek.  In both cases the same five stations emerge as being           ™
the highest.
                                  319
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    Although the presence of oysters in these locations indicates that
numbers and levels of organic compounds in their tissue are probably not
lethal, elevated concentrations can reach biota higher in the food web.
Oysters and other invertebrates can store organic compounds in their
tissue, passing on that amount to consumers.   These organisms, in turn,  may
accumulate harmful levels.
    Comparison of the compounds detected in the oysters with those found in
nearby sediments showed little correlation (Bieri et al. 1981),  indicating
that oysters are not so useful as sediments to monitor the Bay for organic
compounds.  In sediment samples, the most abundant compounds were PNAs.
With the exception of dibenzo-thiophene, fluoranthene, pyrene, and
benzo(e)pyrene, none were detected in oysters.  This could be due to the
compounds not being biologically available to the oysters; or the oysters
may depurate them very rapidly, or metabolize them to other compounds that
were not identified.
ORGANIC COMPOUNDS IN BALTIMORE HARBOR

    The CBP's sampling effort in Baltimore Harbor was identical to the work
previously discussed for the main Bay.  In addition, the CBP funded the
Monsanto Research Corporation (MRC) to sample the major industrial and POTW
dischargers in Baltimore Harbor.  Together these two projects provided a
mechanism by which the compounds found in Harbor sediments could be traced
to possible sources in industrial and POTW effluents.  Concentrations of
the organic compounds in the Harbor sediments were generally much higher
than those samples from the Bay.  Additionally,  many of the compounds found
in the sediments were also detected in the point source dischargers.
    Forty-one bottom sediments were collected from the Patapsco River and
Baltimore Harbor during spring 1981 (Bieri et al. 1981).  The PNAs dominate
the aromatic  compounds in the river as in samples from Chesapake Bay
proper.  In some cases, the concentrations were  ten to twenty times higher
than the highest found in the Bay.   The concentrations of the PNAs within
the river also vary drastically with location.  This suggests that there
are either point sources of PNAs or non-uniform water circulation and
sediment type that cause the organic compounds to accumulate more in
specific areas.  It is likely that  a combination of these two factors is
responsible for the distributions.
    Figure 17 represents the concentrations of one of the PNAs,
[benzo(a)pyrene], normalized to silt and clay content, in the channel
sediments from the Patapsco River.   It is obvious that there are several
areas where relatively high levels  exist.  Point sources may be partially
responsible for the anomalously high concentrations that at one location
reach 5.5 ppm.  The benzo(a)pyrene  concentration in Bay sediments is
depicted by the cylinder farthest to the right.   The concentration here is
about equal to that of the station  next closest  within the Patapsco,  260
ppb versus 290 ppb, respectively.  This suggests, but does not prove, that
the peak of PNAs found in the Bay near the Patapsco River mouth could be
the result of transport from the Patapsco.
    One sample from the Patpasco River gave a very anomalous gas
chromatographic fingerprint that was dominated by an abundance of compounds
with relatively low rentention times and high concentrations.  The
                                 320

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Figure  17.
      62 61  55 60 59 58 57  56 0 N  M  L K  J  I  H  G  F  E  B A
    FERRY BAR  CURTIS  BAY         GRAVITY  CORE  STATIONS



  Distribution  of PNA, beriEo(a)pyrene in  channel sediments
  from Baltimore Harbor  and the Patapsco  River.   Relative
  concentration relates  to height of column  at  each

  location.
                          321
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compounds were not PNAs.  Mass spectrometric analysis and comparison with
EPA-NIH Mass Spectral Data Base showed that they were composed of
substituted benzenes.  The mass spectrometry data files were searched to
see if these compounds were present at any other locations but had been
hidden by more concentrated PNAs.  The search showed that several of the
substituted benzenes were either definitely present, probably present,  or
not present.  The substituted benzene, 6-phenyldodecane, has a widespread
distribution within the Patapsco River,  and data indicate that sediments in
the adjacent Bay also probably contain it.  The sample with the highest
concentration was collected landward from the river mouth.
    Effluent sampling data generated by Monsanto Research Corporation
(1981) showed that an effluent collected very near the sediment station
contained substituted benzenes and, specifically, 6-phenylododecane.  Using
this compound as a tracer, we must conclude that organic compounds can
enter the Patapsco River from point sources, travel throughout the river,
and probably into the Bay.  The fact that 6-phenyldodecane was only
"probably present" in the two eastern most samples prevents stating that
this is definitely the case, but it is difficult to conceive of a mechanism
that would totally stop the eastward migration of the compound at the mouth
of the River.  It is not surprising that these two stations yield data that
are less definitive than the others, because they are in the Bay where more
mixing and dispersion occurs, and they are farthest from the source.
    The methodology developed through the Bay Program for analyzing organic
compounds within sediment of Chesapeake Bay has tremendous potential as an
analytical tool for tracking known and unknown organic compounds in the
system.  The technique essentially generates a chromatographic
"fingerprint" of the peaks found in the sample.  These peaks are "tagged"
by co-injecting relative retention markers and labeling each peak with a
relative retention number.  This becomes important when an unknown peak is
found in a point source discharge and also in nearby sediment or resident
fish tissue.  This information allows one to "flag" potential problem
compounds that may be building up or bioaccumulating in the Bay system.
The technique was used in Phase II of the Monsanto Research Corporation
Source Assessment Effluent Analysis and IMS sediment and oyster tissue
analyses.  A wealth of data on organic compounds is now available in the
CBP data banks, and can be used for years, even decades to come.
    In summary, the basis for our argument, stating that some of the
organic compounds in the northern Bay sediments come from the Patapsco
River, is that (1) PNA concentrations along the Bay rise near the Patapsco
River mouth, (2) concentrations are much higher in the Patapsco River than
in the Bay, and (3) the distribution of 6-phenylododecane is wide spread.
Additional identification of compounds found in Harbor and Bay sediments
and detected in the point source effluents has been done, but will not be
discussed further in this paper.
CONCLUSIONS

    Results from studies on organic compounds show that Chesapeake Bay
contains many polynuclear aromatic hydrocarbons with lesser amounts in Bay
oysters (Bieri et al. 1981).  Because PNA compounds are fairly stable, they
are transported by current flow and sediment motion to other locations in
                                  322

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the Bay.  In general, PNA compounds associate with sediment particles,
partitioning in such a way that concentrations on sediment particles  are          .
much higher than in solution.                                                      •
    The influence of a local PNA source on PNA concentrations in the  Bay
will depend on the proximity of the source to the Bay,  the magnitude  of the
source, the prevailing wind and water runoff patterns,  and the                    I
characteristics of Bay sediments and current in the local region.                  •
    From this information, it can be expected that PNA concentrations in
the Bay should be highest in areas of sedimentation near industrial                •
regions, high population density areas, and power plant sites.  Gradually,         •
over a period of years, diffusion, advection, and sediment transport  will
spread PNA compounds over wider areas of the Bay.  Although PNA transport
from potential sources to sinks in the Bay can be described, quantitative         •
measures of concentrations and transport rates are scant and inadequate.          •
    The question which must be answered is:  are the concentrations
primarily the result of human activity or do they occur naturally from            •
sources such as natural oil seeps or forest fires?  The distribution  and          p
abundance of the PNAs within the Bay and the Patapsco River indicate  that
human activity is mainly responsible.  The established origin of most             _
unsubstituted PNAs (perylene is an exception) in high temperature reactions       I
(Badger 1962, Schmelz and Hoffman 1976, Youngblood and Blumer 1975, Hase          *
and Hites 1976) leaves little doubt about this fact.  Since such
pyrosynthesized PNAs can travel considerable distances (Lunde and Bjorseth         •
1977, Lunde et al. 1976), their occurrence is widespread.  This may explain       •
the presence of such PNAs in the relatively pristine areas of the Ware and
Rhode Rivers, where chrysene concentrations range from 26 to 110 ppb, and         •
benzo(a)pyrene from seven to 100 ppb.  The majority of these PNAs, however,       |
likely settle close to the source and, from there, reach the Bay by runoff
and river transport.                                                              _
    With the increasing combustion of fossil and other carbonaceous fuels,         •
it is likely that the PNA levels in the Bay will increase.  Unfortunately,         ™
the toxicity data required to assess the resulting impact on the Bay's
biota are inadequate.  We do not know the toxicities of the individual            B
components, much less the combinations, and we do not know if they are            •
available to the biota.  But the fact that many of them are carcinogenic,
mutagenic, and teratogenic to mammals is enough cause for concern.   .             •
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                                  SECTION 4

                     PATTERNS OF TOXIC METAL ENRICHMENT
    A limited, but important aspect of GBP research on metals in the Bay
includes several studies on factors affecting their distribution and
concentration.  The dynamic nature of the Bay largely influences the
behavior of metals and, consequently, their threat to the estuary.   This
section describes studies conducted on some of the behavioral aspects of
metal inputs.  It includes sections on processes affecting metal
distribution; enrichment of metals above natural levels;  historical trends
in metal enrichment; and the important relationship between metals  and
sediment.
INTERPRETATION OF PROCESSES AFFECTING METAL DISTRIBUTIONS

    Chemical substances like trace metals are continuously added to
estuaries by inflowing tributary rivers,  shoreline erosion,  the coastal
marine environment, the atmosphere, and the biosphere.   Much of this
material, dissolved and particulate, consists of the natural products of
weathering, erosion processes,  and of biological activity.  In addition,
anthropogenic products and wastes enter the estuary either directly in
effluent discharges or by nonpoint source runoff.  A large proportion of
both the natural and anthropogenic material is intimately associated with
sediments, particularly those of fine particle size and large surface
area.
    Suspended material is not only a reservoir for metals, but a vehicle
that carries metals from their source to  their depositional  sink.  It is an
exchange medium for scavenging and removal of toxic metals from the water
column.  The metal distributions per liter of water show that the zone of
the turbidity maximum is the most enriched (elevated above natural levels)
part of the suspended material reservoir  (Nichols et al. 1981).
Additionally, time-series observations show that much material is
resuspended from the bed, and that river-borne material is most likely
trapped in the convergence of seaward-flowing river water and
landward-flowing estuarine water.  Enrichment is enhanced by small particle
size (5-llu) of the material and by the relatively long residence time of
particles in this zone.
    In the central and lower Bay, metals  borne on suspended  material can be
transported along two pathways, a hydrodynamic route, and a  bioecologic
route.  The hydrodynamic route is revealed by dispersion patterns of metals
in bottom sediments (Helz et al. 1981), whereby seaward transport from
potential sources is indicated along the  west side of the Bay.  This route
is in accord with the path of estuarine flow and the salinity regime.
Landward transport through the lower Bay  is indicated from metal
distributions of Cr (Helz et al. 1981) that extend landward  from the Bay
mouth along the eastern side.
    The relatively enriched metal content of central Bay surface water
suggests that metals like Cd, Cu, Ni, and Pb follow a bioecological path.
Because the enriched zone is generally an area of high  suspended organic
                                324

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                                                                                  I
loads with more than 50 percent combustible organic material,  it  seems
likely that the metals are assimilated from solution by phytoplankton or          •
from suspension by zooplankton.  Once in the food chain the metals  can be         •
further enriched (or bio-magnified)  in fish or filter-feeding  shellfish.
METAL ENRICHMENT
                                 325
                                                                                  I
    Both nonpoint and point sources contribute metals and many organic             I
compounds to the Bay and tributaries from anthropogenic sources (Huggett  et        •
al. 1974b, Helz 1976, Brush 1974).   These levels  are superimposed  on a
background of natural concentrations.   To assess  the impact  of human              H
activity and control amounts reaching the Bay, it is critical to                  •
distinguish natural from anthropogenic levels.
    Some organic compounds occur rarely,  or not at all in nature,  and their
presence and concentration in sediments is direct evidence of anthropogenic        •
input.  The metals, however, occur both naturally and anthropogenically.           •
For a given concentration of metal, there is no direct way to determine the
portion that is natural and that which is anthropogenic.   One method is to        •
derive a ratio of the metal in question to a baseline metal  also contained        g
in the sample.  The baseline metal should have no known anthropogenic
source and should be naturally abundant so that no known pollution sources        —
could significantly affect its concentration.   The accuracy  of this method        •
can be verified by statistical tests.   The precision would require                ™
comparison to known standards, which for this particular measurement, do
not exist.  Therefore, we cannot verify the precision and have not, at  this        B
time, determined the accuracy of this method.                                      I
    Two metals, Al and Fe, were chosen to derive  the ratios  for determining
anthropogenic levels of metals.  Scandium was used by Kingston et  al.              •
(1982) in suspended sediment samples,  because it  is believed to have no           •
anthropogenic sources.  Aluminum and Fe were used in bottom  sediments,  and
Fe was used in fluid mud samples.  Concentrations of metals  in these
samples were normalized using Sc, Fe,  or Al in ratios with concentrations         •
of the metals in average crustal or shale material.  For example,  the ratio        •
of Fe in average shale to Fe in Bay sediment and  also to the concentration
of metal in crustal material, yields an expected  value for Bay sediment.           •
The complete relation is:                                                         |
                              EF = (X/Fe) sediment sample
                                   (X/Fe) crust or shale                          •
Where X/Fe is the ratio of the concentration of metal X to Fe in the              •
sediment sample and in the crust.
    The advantage of this geochemical baseline level is that it provides  a
standard for comparing data throughout the Bay.  It assumes  that the              •
Chesapeake drainage basin is representative of average crust, and  that  a           •
uniform crustal average exists throughout the region.  Consequently, it
does not account for local metal variations.  Because the method is               •
chemical, it is independent of sediment physical  properties  like particle          |
size; it is affected, however, by compositional changes such as varying
organic content within sediment.                                                   _
    Analyses show that enrichment factors in bed  sediment for Cd,  Co, Mn,           •
Pb, and Zn are largely greater than two,  and occasionally reach seven in           ™
the Baltimore-Susquehanna River area (Figure 18).  For As, Cr,  Cu,  Hg,  Ni,
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                        326

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         Zn/AI
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                              Zn/AI
   1940-
   1900-
    1860-
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              024
                        *—BACKGROUND
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   1980-
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   1940-
   1900-
    1860-
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              20    40

            Cu  (ppm)
20    40
 Cu  (ppm)
 20    40
   Cu (ppm)
                                                              60
     Figure 19.  Metal/aluminum ratios, Zn/AI and Cu/AI, for three cores
                from northern and central Chesapeake Bay, coresJ{Q 18,
                and 60.  Data from Helz et al.  1981.  Dates in    Pb
                years; departure of metal/aluminum and metal/iron ratios
                from background in each core, shaded.
                              328

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                                                                                  I
of four kilometers per year.                                                       _
    When interpreting concentration profiles from sediment core samples,  we       •
must be sure that the vertical concentration gradients are not a result of
diagenetic processes that may alter the chemical environment within these
sediments.  Interstitial water data of Hill and Conkwright (1981) on              B
oxidation-reduction (redox) potential and pH values were examined to              M
provide an indication of the magnitude of the various chemical diagenetic
processes in the sediment core samples.  These data reveal no correlations        •
between redox and pH, and metals, so we assume that the upward changes for        •
the metal/aluminum ratios are not diagenetic; that is, there has been
enrichment of trace metals with time.  It is not now possible, and may
never be, to assign a specific cause or source to these metal increases.           •
However, we can speculate that human activity in the watershed and Bay has        •
been sufficient to cause widespread perturbations.  Deforestation for
agriculture, mining, industrial pollution, the construction of three              •
hydropower dams in the 1920s and 1930s, the construction of the sea-level         ||
Chesapeake and Delaware Canal, air pollution, domestic sewage, floods, and
hurricanes probably all contribute to the changes observed.                       _
    Metal enrichment ratios in surface sediments vary in known geological         •
patterns in the Baltimore-Susquehanna River zone as shown in Figure 18.
The ratios increase near the surface of cores with time, matching those
patterns in Figure 19.  These results show that the northern Chesapeake           B
sediments are experiencing important anthropogenic sources for Co, Cu, Ni,        0
Pb, and Zn.
METAL - SEDIMENT RELATIONSHIPS
                                                                                   I
    Analyses of metal concentrations and sediment characteristics performed        •
during the CBP reveal a close association between metal content and certain        •
sediment parameters.  Ninety-six paired samples of surface sediments from
the southern Bay metals and sediment parameters were subjected to stepwise         H
regressions of metal content and sediment parameters.  Every metal analyzed        |
had a significant correlation with at least three independent variables
(Table 11).  Every metal had the highest correlation with percent silt and         *
clay; metals in southern Bay sediments were dominantly associated with the         •
fine particulate fraction.  Over 30 years of research in other estuaries
has consistently verified this finding (Forstner and Whittman 1979).
Correlations with latitude represent axial variation and with longitude,           •
lateral variation that, in turn, may reflect origins.  These sources can be        ™
either up-bay or western-shore rivers, or an association with salinity that
is higher seaward and along the eastern shore, than along the western              B
shore.  The regression equations are useful for predicting the metal               |
content of bed sediments in the southern Bay when only sediment size
analyses are available.                                                            ซ
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TABLE 11.  RELATIONSHIP OF BULK CHEM ANALYSES OF METALS (HELZ ET AL.
           UNPUBLISHED) VERSUS SEDIMENT PARAMETERS (BYRNE ET AL.
           UNPUBLISHED) BY STEPWISE REGRESSION

Stepwise Regression
Metal
Cd
Co
Cr
Cu
Fe

Mn
Ni
Pb
Zn

R2 1
.856
.763
.885
.797
.822

.738
.850
.791
.769

Ranked
Silt, Clay,
Silt, Clay,
Silt, Clay,
Silt, Clay,
Silt, Clay,
Longitude
Silt, Clay,
Silt, Clay,
Silt, Clay,
Silt, Clay,
Longitude
Parameters2
Latitude
Carbon, Latitude, Longitude
Mean Size, Latitude, Longitude
Mean Size, Longitude
Mean Size, Carbon, Latitude,

Carbon, Latitude, Longitude
Carbon, Latitude, Longitude
Carbon, Latitude, Longitude
Mean Size, Carbon, Latitude,


^-Significant at .0001
     parameters are percent silt, percent clay, mean size,  percent
 organic carbon, percent sulfur, percent ^0, Latitude, Longitude.
 Parameters were not ranked when they did not meet a 0 . 15 significance
 level.
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                                  SECTION 5

                       FINDINGS ON SEDIMENTS AND BIOTA
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    This section describes results of GBP research on aspects of sediment         |
and biota that influence the fate and transport of metals in the Bay.   The
first part discusses physical and chemical characteristics of sediment,  as        •
well as patterns of sedimentation.  The second half of the section                •
describes the character of benthic animals in the Bay and how their
activities influence the availability of toxic chemicals.


CHARACTER OF BED SEDIMENTS

    Because of the close association between metals and sediment, the              •
character of bottom sediment (including its texture, water content, carbon
and sulphur content), and sedimentation rates were determined in detail
(Kerhin et al. unpublished,  Byrne et al. 1982, Carron 1979).                      •
    Information about the surface sediments was derived from more than 4000       •
samples collected on a 1.0 to 1.4 Km grid.  Grain size of the sand fraction
was analyzed by a Rapid Sediment Analyzer, and the clay and silt fractions        •
were analyzed by settling and pippette withdrawal and a Coulter Electronic        ฃ
Counter.  Total carbon and sulfur were analyzed in a LECO induction furnace
equipped with a gasometric carbon analyzer and an automatic titrater.              _
Water content was determined gravimetrically by weight loss on drying.            •

Texture

    Sediment texture is characterized by its particle size, with sand  the         |
largest and clay the smallest component.  Bay sediments are differentiated
into 10 classes according to the percentages of sand (0.063-2mm), silt            •
(0.004-0.063 mm), and clay (0.0006-0.004 mm), following Shepard (1954).   Of       J|
the three end members, sand covers 57.4 percent of the total Bay surface
area; silt and clay less than 2.2 percent, whereas the rest of the area
consists of mixtures of sand, silt, and clay.  Of the total sand area  (3600       •
Km2)( 60 percent lies in Virginia.  Sand, together with mixtures of sand,         ™
silty-clay, and sandy-silt types, cover 85 percent of the total Bay area,
with nearly all the silty clay in Maryland and most silty sand in Virginia.       •
    The distribution of sediment types in the Bay is controlled by the kind       |
of material supplied and by the processes at the site of deposition.  In
the northern Bay, with the exception of the Susquehanna Flats, the                ซ
predominate sediment type, silty clay, accumulates in the vicinity of  a           •
potential source, the Susquehanna River.  As the Bay becomes wider seaward
and the relative influence of river-derived sediment decreases, sand and
clay eroded from banks and shores are the most abundant sediment.  Sand           •
accumulates in more energetic zones, for example, on shoals less than  about       •
six meters, and close to its shore source.  Silty clay, by contrast,
resides in deep water greater than about 10 meters, a less energetic zone         •
of inhibited wave stirring on the bed.  This fine-grained sediment includes       |
river-borne as well as marine material, shore sediment, and some skeletal
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material produced in the central Bay itself.   The basic pattern of sand on
the shoals and silty clay at greater depths is interrupted by patches  of
mixed sediment, silty sand, clayey sand,  and  sand-silt-clay.   A linear zone
of clay at intermediate depths along the western side,  between the South
River and the Potomac represents a terrace exposure of  old Coastal Plain
formations.  Similarly, a large zone of sand  on shoals  along  the eastern
side, between Bloodsworth-Smith and Tangier Islands,  is probably relic
sediment.
    Sediments of the southern Bay are distinctly coarser than elsewhere.
Silt predominates over clay and, therefore, zones of  fine sediment in  deep
water are clayey-silt or sandy-silt.  Sand resides on shoals  less than 12
meters and in channels of the Bay entrance.  Locally, deep channels greater
than 20 meters that are scoured by currents are floored by coarse sand.

Water Content

    Sediments with high clay and silt content have a correspondingly high
water content and thus, potentially high toxicant content.  The mean water
content of surface samples expressed as percent of wet  sediment by weight,
range from 16 to 83 percent for Maryland (Kerhin et al. unpublished) and
from 13 to 75 percent for Virginia (Byrne et al. unpublished).  The mean of
all samples in Maryland is 47.4 percent and 30 percent  for Virginia.  A
plot of water content versus mud (clay and silt) content for Virginia
sediments is shown in Figure 20.  This graph shows a linear trend whereby
water content increases with increasing mud content.   A similar trend  was
revealed for Maryland except for clay samples from the  relic  terrace zone
of the upper middle Bay, an area with relatively less water content for a
given clay content.  The high water content of fine sediment  (greater  than
about 64 percent dry weight or equivalent to a density  of 1.30 g/cm^)
defines fluid mud that is a sub-reservoir for toxicants.

Carbon and Sulfur

    Organic carbon and sulfur affect the fate of toxicants in sediments by
determining the redox state of the sediments after deposition.  When
organic matter and sulfate of seawater is reduced, hydrogen sulfide (l^S)
is produced, and metal sulfides (as Fe2S04.) are formed  and concentrated
in the sediment.  Thus, they are more available to biota.
    Organic carbon in bed sediments averages 2.2 percent dry  weight for
Maryland and 1.0 percent for Virginia.  The bulk analyses of  organic carbon
include organic matter of plant and animal tissues as well as skeletal
parts.  Isolated high values reaching 10 percent in the northern Bay are
attributed in part to bituminous coal particles.  The organic carbon
content shows a preference for fine sediment (Byrne et  al. unpublished).
Regression analyses indicate strongest associations with clay fractions.
Consequently, organic carbon content is higher (greater than three percent)
in the deep central Bay, where fine sediment  accumulates, than in the
nearshore zones of sandy sediment.  Inner parts of tributary  embayments
like Mobjack Bay and Pocomoke Sound contain more than three percent organic
carbon content.  The distributions of organic carbon content  reveal two
main sources:  the Susquehanna River for the  northern Bay and primary
production for the central Bay.  Mid-Bay organic carbon levels are the
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      80 H
      70-
      60-
   z
   LU
   H-

   O
   o

   cr
   LU
      10-
       0-1
             r  =0.90

             y  = 0.45x  4- 18.4
         0   10   20  30  40   50  60  70  80   90  100

                      MUD,  % WEIGHT
Figure 20.   Relationship  of percent water content to percent mud
            content for surface  sediment samples from the Bay.  Data
            from Byrne et al.  (1982) and Kerhin et al. (1982).
                            333
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result of high biological activity (primary production)  in this area.   The
high productivity levels produce elevated carbon concentrations in the
water, ultimately causing high levels of detritus (organic matter
containing high organic carbon content)  to be deposited  and mixed with
bottom sediments.  The Susquehanna River contains high carbon levels from
natural detrital matter (leaves, humus,  fecal material,  etc.),  pollution
sources (such as POTWs), and other natural and anthropogenic carbon sources
in this drainage basin.
    The bulk analyses of sulfur measure  the total reduced sulfur in the
form of sulfide and metal compounds,  organic sulfides, and sulfate residues
of interstitial waters.  Sulfur content  of northern Bay  sediments is
relatively low, less than 0.5 percent for most samples (Kerhin  et al.
1982), whereas the middle Bay has one to two percent. Anomalously high
values found in the main channel off  the Choptank River  are believed to be
caused by the flux of sulfur out of nearby or underlying Miocene sediments
(Kerhin et al. 1982).  This is indicated by the interstitial water
chemistry that exhibits positive down-core sulfide fluxes.  Sulfur content
of samples from Virginia is generally less than 0.5 percent except for deep
zones south of the Potomac River mouth.
    Sulfur in the sediments is derived from two main sources, seawater and
decomposition of proteins in organic  detritus.  Relatively high sulfur
content of middle Bay sediments is probably derived from landward-moving
oceanic water as well as by deposition of phytoplankton  degradation
products from near-surface water.  Sulfur content increases with organic
carbon content in most Bay samples except the northern Bay which has
relative low sulfur content and high  organic carbon.  This relation probaby
relates to a terrigenous influence of waste from the Susquehanna River.

Patterns of Sedimentation

    Changes in water depth of the Bay were established by comparing depth
soundings on old charts.  These changes  relate to sediment deposition and
erosion.  Charts of Virginia provided good coverage between 1850-1860 and
1950-1960, but in Maryland some were  surveyed after 1900, and the record of
depth changes spans 30 years (Carron 1979, Byrne et al.  1982, Kerhin et al.
1982).
    Charts of the northern Bay generally show that shoaling areas
(long-term filling in greater than 0.5 meters per century) exceed deepening
areas.  Changes greater than 2.5 meters  per century are  recorded locally in
the channel near Tolchester and off Kent Island, Maryland (Figure 21).  As
the channel deepens farther seaward,  high shoaling O2.5 meters per
century) occurs locally on the channel floor of the upper and lower middle
Bay.  The deepest holes of the channel leading through the central Bay are
sites of depth increase or erosion, in excess of two meters per century.
Farther seaward, erosional zones are  also recorded in deeper parts of the
main channel near Cape Charles and in the north-entrance channels to the
Bay.
    Zones flanking the main channel display many variations that relate to
bathymetry and geology as well as to  modern sedimentary  processes.  For
example, inner parts of marginal shoals  are deepening, an indication of
erosion, but outer (channel-ward) parts  show no change or slight shoaling.
In a general way, the change from deepening to shoaling  relates to the
concept of erosion of a marine shoreline as it approaches adjustment to
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             >80% SILT 8 CLAY

             >l.0m SHOALING PER
               100 YRS.
Figure 21.  Sedimentation  zones  in areas of fine sediment, greater
            than 40 percent clay,  with greater than 1.0 m of shoaling
            per 100 years, in  the  Bay proper.   Data from Byrne et al.
            1982 and Kerhin et al. (1982).


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modern wave processes.  The material eroded from the shore or inner
shallows must be transported either laterally or channel-ward where it  is
deposited in deep, less energetic zones along the adjacent channel.  The
maximum shoaling rate in Virginia occurs in water depths of eight to 12
meters.  For example, the clay terrace off Calvert County is largely
erosional.  It contains shoaling patches of sand along nearshore parts,
suggesting offshore transport of eroded shore sand.  Variable patterns  on
the "sand shield" around Tangier and Smith Islands, either slight deepening
or shoaling in depths less than seven meters, indicate the constant
reworking of sediments by wave action, local shoreline sources of sediment,
migration of longshore bars, and relic sedimentary features.  Other areas,
like the steep eastern side of the main channel south of Core Point, have
alternating patterns of shoaling and deepening that suggest slumping of the
channel wall.  This is confirmed by sub-bottom profiles that show slump
scars at the slope break of the eastern channel wall and multiple sediment
layers on the nearby channel floor.
    The Chesapeake entrance and Bay floor, extending landward about 40
kilometers, is predominately shoaling (Figure 21).  Most deposition occurs
on elongate shoals; some occurs on flanks of the large Horseshoe Shoal, the
main Chesapeake channel floor, and the lower part of old Plantation Flats.
Most of the shoaling material is fine to very fine sand, probably derived
from the Bay entrance on adjacent shores and inner shelf, and transported
landward by the net residual bottom flow.
    Toxicants may be expected to accumulate in areas of fine sediment
shoaling.  The rate of toxicant accumulation will vary from place to place
in proportion to the shoaling rate (Figure 21).  By contrast, deep channels
where erosion is active, are poor places to dump waste materials because
the currents would remove them.  Areas in which the channel is stable or
shoaling are the best sites for disposing waste materials.
BENTHIC ORGANISMS

    Benthic organisms act with physical processes to either enhance or
inhibit movement of toxic material.  They can redistribute dissolved
toxicants in interstitial water or mix contaminated sediment within the
bed, as well as between the bed and overlying water.  Through their feeding
and burrowing activities, they can bury new surface sediment or expose
older deposits.  At the same time, their activity can stabilize surface
sediments through binding or tube building.  On the other hand, they can
mobilize sediment by decreasing compaction and increasing water content.
By feeding and filtering suspended sediment and by excretion, they produce
fecal material and, in turn, promote sedimentation.

Character of Benthic Fauna

    The distribution of benthic organisms in Chesapake Bay has been
documented in a number of studies (Boesch 1977a,  1977b; Holland et al.
1977; and Loi and Wilson 1979), most of which indicate that both physical
(salinity, substrate type, depth) and biological  (competition and
predation) factors influence the distribution and abundance of the
macrobenthos.  The wide range of habitats sampled in this study affords the
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Species Diversity
Bioturbation
                                                                                  I
opportunity to make generalizations concerning species distribution on a
Bay-wide basis.  To avoid the confounding effects of seasonality on               B
community structure, fall 1978 and summer 1979 collections were considered        |
separately in a numerical classification analysis (Diaz and Schaffner 1981,
Reihnarz and O'Connell 1981).                                                     g

Community Composition

    Of the animals sampled in the Bay,  polychaete annelids were the most          •
abundant and diverse taxonomic group,  consisting of 23,797 individuals and        •
95 species.  Crustaceans were second in abundance and diversity with 10,427
individuals and 48 species,  and molluscs were third with 5,088 individuals        •
and 43 species.  Miscellaneous groups  were represented by 310 individuals         ฃ
and 17 species.
    Although the number of species did not change drastically from fall           ^
1978 to summer 1979, a great disparity existed between the number of              •
individuals and the relative composition of fauna collected.  Some of this        ™
disparity is explained by an increase  in the percentage of muddy stations
sampled in the summer relative to the  fall.  More .importantly, summer             B
collections, particularly in the lower Bay, contained large numbers of            •
juvenile polychaetes that were presumably recruited to the sediments during
the spring.  Low abundances  in fall collections may result from the heavy         •
predation pressure, by blue  crabs and  fish, exerted on these populations          •
throughout the summer (Virnstein 1977).
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    Mud habitats were generally less diverse and had fewer species than
sand or mixed-sediment habitats.  In some cases, these results related to          •
the fact that stations were located in deep channels or sound areas where          |
periodic oxygen depletion resulted in a depauperate fauna (Diaz and
Schaffner 1981, Reinharz and O'Connell 1981).                                      —

Vertical Distribution                                                              *

    The majority of macrobenthic organisms, in all salinity regimes and            V
sediment types, were found in the upper 10 centemeters of the sediment             m
column.  Generally, mixed or sandy sediments had the greatest percentage of
deep-living organisms.  Most of the organisms below 10 centimeters are             •
annelids.                                                                          •
                                                                                   I
    Evidence from both the vertical distribution studies and x-radiography
suggests that nearly all of the benthic communities in the Bay have the
potential to move and mix sediments, which in turn can affect the fate and         fl
distribution of sediment-bound toxicants.  The modifications of physical           |
structure in sediments by organisms (bioturbation) fall into three
categories: (1) the construction of tubes as dwelling structures, (2) the          •
abandonment and subsequent filling-in of old tubes, and (3) general                •
sediment disturbance and mixing from locomotion.  Analyses of the degree of
bioturbation as estimated from x-radiography of box cores indicate that
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levels of bioturbation and types of biogenic structures vary depending on
both salinity regime and sediment type (see Reinharz et al.  1980,  Nilson et
al. 1980).
    Sandy habitats in the Bay are generally restricted to the head and
mouth of the Bay as well as to some areas along the eastern  shore.
Physical structures preserved in these regions include cross-bedding
patterns and ripple lamination.  In shallow, high energy regions of the
upper Bay, some of these structures have been completely disrupted because
of wave action.  Sands in the lower Bay generally have a uniform
bioturbated sediment fabric, reflecting movement and mixing  by communities
composed of a highly mobile fauna.
    Mud habitats are most abundant in the lower salinity regimes of the
Bay, north of the Rappahannock River.  Physical structures dominate the
muddy sediments of deep channels and holes at the mouths of  major rivers.
Stressful fluid mud substrate and periodic summer anoxia allow only the
temporary settling of opportunistic species.
    Muds in shallower regions are less likely to suffer anoxic conditions
and have a more diverse fauna for mixing sediments.  In all  areas of the
Bay, biogenic structural diversity is greatest in shallow mud habitats.
    Bay-wide patterns in degree of bioturbation, based on x-rays of
sediment cores, are summarized in Figure 22.  Sediments are  highly
bioturbated (90-100 percent) throughout most of the Bay.  Areas where
bioturbation is low include the uppermost oligohaline reaches of the Bay,
deep channels, sounds, and river mouths that are presumably  subjected to
periodic oxygen depletion and often characterized by fluid mud substrate.

Biological Sediment Mixing and Fate of Toxicants

    Evidence from both the vertical distribution studies and x-radiography
suggests that nearly all of the benthic communities in the Bay have the
potential to move and mix sediments and, in turn, influence  the fate and
distribution of sediment-bound toxicants.  Several studies (Rhoads 1963,
Gordon 1966) have measured particle mixing rates of common marine
invertebrates of shallow-water North Atlantic habitats and have found them
to exceed annual sedimentation rates.  Depending on local sedimentation
rates, sediment-bound toxicants may be retained in the upper sediment
layers as a result of biological activities.
    Areas of high sedimentation rate (generally in the oligohaline salinity
regime of the upper Bay [Figure 21] and in some channel areas) were
generally found to have low levels of bioturbation.  Thus, the fate of
sediment-bound toxicants in these areas would probably be primarily
controlled by non-biological physical factors such as storms.  The fate of
toxic materials in the mud habitats of the central and lower Bay,  where
bioturbation averages greater than 90 percent, would probably be influenced
by biological mixing.  The probability for retention of toxicants in
surface-sediment layers in these habitats seems high because of the
turnover of sediments by animals.
    The effect of bioturbation on the vertical distribution  of heavy metals
in the sediment is revealed by depth distribution of radioactive lead.
This isotope, 210 Pb, is delivered uniformly to the Bay from atmospheric
sources.  Once in the sediments, its concentration is proportional to the
rate of sedimentation and time because it radioactively decays.  The deeper
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the sediment, the less 210pfc (Helz et al.  1981).  This is found to be the
case in areas where there is little or no  bioturbation;  for example,  in the
deep muddy channels of the middle Bay.  However, in areas of high
bioturbation there is a zone of uniform 210pjj concentration that
corresponds to a biologically active zone  where animals  are mixing the
sediments.  Such areas were found in the upper and lower Bay where
bioturbation caused mixing of sediments down to levels equivalent to  50
years of deposition.  Therefore, in these  areas toxicants are not likely to
be buried.
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                                  SECTION 6

                         TOXIC SUBSTANCES AND BIOTA
EXPOSURE ASSESSMENT
                                 341
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    An important question remaining in the CBP's investigation of toxic
substances is whether or not levels found in the Bay are harmful to the            •
many organisms living there.  Although assessing the toxicity of metals and        |
organic compounds was not part of the GBP's original scope of work, a
limited evaluation of some metals and organic compounds was done.  Further         •
assessment of the problem is presented in the third CBP final report,              •
Characterization of Chesapeake Bay (in progress).  Specifically, the
characterization report includes discussion of levels of organic compounds
and metals in the water column and bed sediment, with a separate section on        I
Kepone in the James River.                                                         |
    This section addresses toxicity studies done during the research
portion of the Bay Program.  It includes results from the CBP's exposure           •
assessment, experiments on histopathology of a native bivalve,  and                 I
bioassays of sediment and industrial effluent.
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    This discussion only addresses concentrations of toxic chemicals in the
water column measured during the CBP Toxic Substances Program,  and for
which we have EPA criteria.  The EPA Ambient Water Quality Criteria
Documents (EPA 1980) for priority pollutants, lists the criteria values.             M
These are expressed as the total recoverable concentration in the water             I
column, including dissolved, plus the potentially biologically  available
fraction associated with suspended sediment.  Assuming that any metal
attributable to enrichment is potentially biologically available to biota,          •
we can calculate the "available" concentration of that metal.  Adding this          •
to the concentration of dissolved metal produces a reasonable,  and probably
conservative, estimate of the total recoverable value.                              •
    Except for the Baltimore-Susquehanna River mouth zones, no  metal                J|
exceeded the EPA criteria in the Bay proper.  Above Baltimore,  several
stations barely exceeded the 24-hour average (chronic) criteria for Cd or           ซ
Cu.  The criteria violated are based on subtle chronic effects  of sensitive         •
species, the impact of which is not understood, and the calculated
concentrations exceeded these criteria only marginally.  These  violations
alone do not necessarily imply a serious ecological impact.  Additionally,          •
there is some evidence that organisms can acclimate to toxic substances,             •
thereby lowering their sensitivity to those toxicants.  On the  other hand,
there may be species that are more sensitive than the species tested.  In           •
addition, synergistic interactions may greatly increase the toxicity of a           |
pollutant, thereby affecting the biota even at sub-criteria levels.
    Although this assessment does not show immediate ecological impacts,             _
the toxicity of some Bay sediment (see section on Sediment Bioassays) and           •
the proximity of metal concentrations to EPA criteria values (recommended           *
levels for water) indicate that north of Baltimore the Bay may  border on
toxic impacts.  Additional loadings of toxic substances to these waters             B
may, therefore, prove harmful to the biota.                                         |
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TOXICITY STUDIES

Histopathology

    Diaz et al. (1981) conducted preliminary studies on populations of the
bivalve, Macoma balthica, to determine potential toxic effects.  [See
"Characterization of Chesapeake Bay" in progress for more complete
analyses.]  Macoma balthica is an infaunal species that burrows to 30
centimeters deep in soft mud.  Although not a commercial species,  Macoma
was selected because it has varied feeding habits in both surface deposits
and suspended material, and it is ubiquitous.  Seven hundred and forty
clams were analyzed for abnormalities from relatively contaminated sites of
the Patapsco and Elizabeth Rivers and from relatively uncontaminated sites
of the Rhode and Ware Rivers.  Of the 740 clams examined, only 26
pathogenic cases,  or 3.5 percent, were found (Table 12).  No statistical
relationship is evident between the pathogenic conditions and the river
system in which the clams reside, indicating that the data do not reveal
any adverse effects of sediment-associated contaminates.

Sediment Bioassays

    Since many potential toxicants accumulate in the sediments at
concentrations higher  than in the water column, preliminary bioassays were
performed on sediment  from 70 sites throughout the Bay and selected
tributaries including  the Patapsco and Elizabeth Rivers.  The infaunal
amphipod Repoynius abronius, a species considered sensitive to sediment
contamination, was collected from relatively uncontaminated sediment and
water from Oregon.  Repoynius abronius was placed in test sediment from the
Bay, and in the relatively uncontaminated sediment for control, at the EPA
Marine Science Center, Newport, Oregon.  The samples were split and run in
both quiet (non-stirred) and stirred, aerated, overlying water of 25 ppt
salinity.  The stirring action was induced to release interstitial water
and obtain a common salinity in all samples.  After ten days, the number of
survivors were recorded from sieved samples.
    The highest mortalities, greater than 90 percent, occurred in stirred
and non-stirred samples from the upper reaches of the Patapsco and
Elizabeth tributaries  and from the northern Bay, particularly in the zone
between Baltimore and  the Susquehanna River mouth.  As shown in sections
III and IV, sediments  from this zone are generally more enriched in metals
and organic compounds  than elsewhere.  The results of these experiments
conclude that toxicants may cause experimental mortality.
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TABLE 12.  SUMMARY OF HISTOLOGICAL ABNORMALITIES FOUND IN MACOMA BALTHICA
           CLAMS FROM UPPER AND LOWER BAY TRIBUTARIES  (DATA REPRESENT
           NUMBER OF CLAMS WITH ABNORMALITIES; PARENTHESES INDICATE THE
           PERCENT OF TOTAL FROM THE RIVER)

Total Clams
Examined
Upper Bay
Pa taps co River
Rhode River
Lower Bay
Elizabeth River
Ware River
Totals
404
189
83
64
740
Number
of Pathogenic Cases
Dermo
7(1
2(1
1(1
2(3
12
.73)
.06)
.21)
.12)

Bacteria
1(0.25)
1(0.53)
0(0.0)
0(0.0)
2
Glandular
Cysts
1(0.25)
5(2.65)
1(1.21)
5(7.81)
12
Total
9(2.23)
8(4.23)
2(2.41)
7(10.93)
26

Effluent Toxicity Tests


    Of an estimated 5000 discharges in the Chesapeake region,  approximately
1000 are considered to have the potential for discharging toxic material
based on criteria established by the National Enforcement Investigation
Center of the U.S. Environmental Protection Agency.  As part of the CBP
Source Assessment Program, effluent from fifty of these dischargers was
sampled and characterized in terms of major chemical species (down to 1-10
ppm) and their potential toxic effect on biota as determined by bioassay
tests.  The selections were based on industries with the highest potential
for toxicity (not known toxicity problems).  The criteria for  ranking the
industries were based on flow rate of effluent and expected concentration
of chemicals in the effluent.  The bioassays were conducted to evaluate, or
indicate toxicity of the effluent.  The dischargers from which effluent was
sampled during the Program are shown in Appendix E.  This appendix also
shows the many different bioassays performed and the experimental results.
Values of results are expressed as percentages of diluted effluent that
caused death for various species tested.  The EC5Q> LC5Q, [or  SC2Qi
ECjQ (Effluent Concentration)] is the percentage of effluent that would
inhibit growth by 50 percent.  LC5Q (lethal concentration)  is  the
percentage of effluent that caused a 50 percent kill of the species.
SC2Q is the percentage of the effluent that stimulated growth  by 20
percent.  Bioassays were performed on fish, several invertebrates,
bacteria, and seagrass.  Table 13 shows the kinds of tests  used.
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 TABLE 13.   TESTS  USED FOR MEASURING POTENTIAL  TOXICITY  OF  INDUSTRIAL
             EFFLUENT

Organism
Fathead minnow
Sheepshead minnow
Daphnia sp.
Mysid shrimp
Thalassia sp.
Marine bacteria
Test
96 hr. LC50
96 hr. EC50
48 hr. LC50
96 hr. LC50
3 -week EC50
EC50 Microtox

 Results:   Bioassays of Fathead minnows and  Sheepshead minnows were tested
 at minimal,  low, moderate,  and high  toxicity values  (NT-75, 50-75, 25-49,
 and 0-24  respectively, Appendix F).  Twenty percent  of  the effluents
 sampled exhibited moderate  to high toxicity, whereas 80 percent exhibited
 minimal to low.
     Invertebrate bioassays  of Daphnia and mysid shrimp were tested at
 minimal,  low, moderate, and high toxicity values, NT-75, 50-75, 25-49, and
 0-24 respectively (Appendix G).  With the results of these two bioassays
 combined,  approximately 30  percent of the effluents  sampled indicated
 moderate  to  high toxicity.  In addition, the mysid shrimp appeared more
 susceptible  than the Daphnia to the  toxic substances found in the effluents,
     A Marine Bacteria Bioluminescence Bioassay indicates that 50 percent of
 the effluent samples were moderate to highly toxic.  However, a bioassay on
 Thalassia (Sea Grass) displayed little or no effect  from the effluents
 (Appendix H).
     Mutagenic and cytotoxic effects  were tested by utilizing
 Salmonella/microsomal (Ames Test) spot tests and plate incorporation assays
 (not listed  in Table 13). These were performed on filtrates and extracts of
 10  effluent  samples.  No mutagenic response was observed in the pour-plate
 assay with the particulate recovered from sample filtration (Appendix I).
A positive mutagenic response in sample A108 Filtrate I was observed using
 the  plate assay.  The spot test of effluent sample A104 Filtrate I showed
an  increase  in revertants over the control, but no clear positive response.
     The Chinese hamster ovary (CHO) mammalian cell cytotoxicity assays
showed that  effluent samples from A105,  A106,  A110 exhibited medium level
 toxicity  for the sample as received;  A100 showed low toxicity in samples
A102, A103, A104, A106, A108,  and A110 (Appendix J).  Acetone extracts of
the  particulate showed low or very low toxicity ratings for samples A100,
A103, A106, A107, A108, and AllO.   Samples A101 and A109 showed no toxicity
 for  any of the three types of sample.
     In summary,  effluent bioassays on fish, invertebrates,  and bacteria
indicate  that 20 to 50 percent of the effluents sampled had moderate  to
high toxicity.   A greater risk of toxicity in  the  Bay is generally
associated with high effluent  toxicity.
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                                                                                    I
                                   SECTION 7
            CONCLUSIONS,  INTERPRETATIONS, AND MANAGEMENT IMPLICATIONS


    The following abbreviated statements are organized to review the key            I
observational findings (underlined) followed by an interpretation and
management implication(s).  •                                                         _


METALS

1.  The Bay receives metals from human and  natural sources through rivers,  the      B
atmosphere, and industry.  The rivers are a dominant pathway for Cr, Cu, Fe>
and Zn; industry is a dominant source of Cd, and the atmosphere is a                •
significant pathway for Pb and Zn.  Metal input to the main Bay is greatest         B
from the Susquehanna River.
    Metal input from rivers is relatively high because of large contributions
from geologic weathering and soil erosion of fine sediment in the drainage           B
basins.  Additionally, rivers supply metals from municipal and industrial           ™
effluents and, indirectly,  from atmospheric deposition on the drainage basin.
The Susquehanna River is a strong pathway because of its  relatively large           •
water and sediment discharge.                                                       |
    The Susquehanna is the only river that  discharges directly into the Bay.
Main tributaries, like the James and Potomac,  discharge into estuaries that         •
entrap sediment and sediment-borne toxicants.                                        B

2.  Bay water contains the metals, Mo and U, mainly in dissolved form (j> 90
percent of total metal), and they positively and linearly correlate with            B
salinity.  The metals Cd, Co, Cr, Cu, Ni, Pb,  and Zn occur both in dissolved         B
and particulate form (between 10 and 90 percent are dissolved), whereas more
than 90 percent of the Fe,  Mn, Sc, and Th occurs in particulate form.               •
    Relatively high concentrations of Mo and U are probably controlled by           B
alkalinity of Bay water and by dilution of  seawater with  river inflow.  The
concentrations of metals Cd, Co, Cr, Cu, Pb, Ni, and Zn are controlled by           a
complex interactions of chemical solubility, sediment adsorption-, and               B
bioconcentration; Fe, Mn, Sc, and Th distributions are mainly a function of
sediment adsorption-precipitation reactions.  Metals in dissolved form are
diluted, mixed, and flushed through the Bay and, therefore, their effects are       B
short-lived.  Metals in particulate form, however, have a longer residence           B
time in the Bay and can build up to high concentrations through
bioaccumulation and sediment adsorption.                                            •
    The relevant management practice is to monitor and control metals               B
discharge while taking into consideration the different solubilities,
bioavailability, and adsorption properties  of the different metals.  Through         _
consideration and understanding of these properties, one  can better regulate         B
the type, amount, and location of allowed discharges.  As  an example,               ™
dissolved metals are readily taken up by plankton, whereas particulate metals
are likely consumed by suspension feeders or benthic filter feeders.  Adverse       B
effects, however, will vary with the chemistry of the metal and the response         B
of the organism to the metals.
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3-  Concentrations of As, Cd, Cu, Hg,  Ni,  Pb,  Sn, and Zn per gram of suspended
material are maximal in near-surface suspended material of the central Bay.
Enrichment factors range:  Cd, 10-118; Cu, 12-27; Pb, 37-51; and Zn, 16-74.
The percentage of organic matter in this zone  is generally higher than
elsewhere.
    The association of a relatively high content of metals with organic matter
in the same zone suggests that biological  activity is the proximal cause of
accumulation.  The metals can be derived from multiple sources, natural or
anthropogenic.
    Control of bioaccumulations can be affected by changes in water quality
that will reduce productivity.  These  changes  include lower light, increased
turbidity, lower nutrient input, and reduced mixing.  However, some biota,
such as phytoplankton, require certain metals, like Mn for photosynthesis.
Other metals such as cupric ions, with extreme reactivities, interfere with
uptake of essential metals.  Because metals, sediments, and nutrients are
interrelated, they need to be managed  together.  Piecemeal management of
single components cannot succeed.
    Most control measures have focused on near-field discharges and immediate
effects.  There is a need to manage for subtle changes and "far—field"
effects.  Processes leading to bioaccumulation and particle concentration in
the turbidity maximum need to be taken into account in any effective
management plan.  Moreover, water, particulates, sediments, and biota should
be managed as a dynamic system in which trace  metals are continually being
repartitioned.

4.  Secondary maxima of Cd, Mn, Ni, Pb, Sn, and Zn concentrations per gram of
suspended material are found in near-surface water of the Bay off the Patapsco
River.
    These secondary "hot spots" suggest that metals are derived in part from
the Patapsco River and Baltimore Harbor via near-surface currents or, for
another part, by periodic resuspension from old dredged material on the Bay
floor.
    The relevant management practice is to stabilize potential sources of
contaminated sediment from the Harbor  either by removing future dredged
material from the system or by stabilizing the natural sediment through
consolidation, dewatering, or grass cover-

-*'  Sediments from the northernmost part of the Bay floor are enriched
relative to average crustal shale in Cd, Co, Cu, Mn, Ni, Pb, and Zn by factors
of two to eight.  Cd, Pb, and Zn are enriched throughout the main Bay by
factors of two to six relative to average shale.
    The Susquehanna River is a distinctive primary source of metals in bed
sediments of the northernmost Bay.  This is confirmed by similar enrichment
factors and similar metal-Fe ratios in the river and northern Bay.  The metals
are sequestered in fine sediment and associated with river-borne organic
material.  Since enrichment factors diminish markedly with distance seaward
from Kent Island, contaminated sediment is probably not transported seaward  of
the Patapsco mouth in quantity.  This  assumes  diagenetic processes are not
contributing significantly to the seaward  reduction of enrichment.  Instead,
metals mainly accumulate in the turbidity  maximum zone where suspended
sediment is trapped.  Once deposited,  the  metals can be resolubilized and,
thus, released from contaminated sediment  and  potentially available to the
biota.
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                                                                              I
Because the Bay system is complex,  it requires a fairly sophisticated
                                                                               I
input of technical information about the system being managed.  It should be       I
managed with a scientific data base and a knowledge of processes affecting         •
behavior transport and fate of potential toxics.  Therefore,  effective
management decisions should be coupled to monitoring data and scientific           •
knowledge of processes.                                                            fj
    The new information on distribution of enriched bed sediment provides data
with which to broadly classify potential dredged material.   Such a                 •
classification provides input for decisions on dredged spoil  management — its     •
best use, disposal techniques, or dumping sites.

6-  The Bay floor is a major sink for metals and organic compounds.   More than     •
60 percent of the total input of Fe, Mn, Ni, Pb, and Zn is  retained  in the bed     •
sediments.
    Bed sediments in the central and northern Bay are enriched with  metals,        •
(Cu, Pb, Zn) to depths of 14 to 26 cm, representing about 60  to 90 years of        •
deposition.  Metal enrichment reaches a peak between four and 18 cm  (1930 and
1960) and diminishes toward the surface.
    The enriched metal peaks in the northern Bay probably represent  peak metal     •
loading from a dominant source, the Susquehanna.  The influx  was first felt in     •
the northern Bay and later in the central Bay.  Zones of fast sedimentation
are sensitive to contamination.  When metals are buried deeper than  the zone
of active diagenesis, they may be effectively immobilized and thus unavailable
to biota.
    Since sediments record long-term changes in metal loading, they  can            •
provide an indication of future trends if the depositional  flux is coupled to      I
the input flux.  Whereas analyses of water samples from contaminated zones may
not detect some toxic chemicals in small amounts, sediments with toxic
substances that are strongly sorbed can build up to levels  and thus  be readily     I
detected.                                                                          |

7.  Major transport pathways for metals follow either a hydrodynamic route or      •
a bioecologic route.  The principal sinks for toxics are located in                 •
near-source zones where fine sediment accumulates.
    The hydrodynamic route through the northern Bay follows the pattern of
estuarine circulation; that is, seaward through the river and upper  estuarine      I
layer, and landward through the lower layer.  This route leads to entrapment       •
of contaminated sediment near the inner limit of salty water  close to its
major source the Susquehanna River.  Secondary sinks of accumulation occur in      •
less energetic zones:  the central Bay axial basin and inner  reaches and           I
mouths of tributaries that promote moderate to fast sedimentation and
accumulation of fine sediment.                                                     •

8.  More than 300 organic compounds were detected in Bay sediments.   Most were
PNAs having anthropogenic sources, and many compounds are among EPA's priority
pollutants.                                                                        I
    The organic compounds tend to associate with fine suspended material in        •
the water and accumulate on the Bay floor as the suspended  material  settles.
Because of their polarity, some organic compounds may occur in dissolved form,     •
but they are below the detection limit of most present-day  instrumentation.        |
Significant concentrations of priority pollutants are cause for concern about
sources and effects on Bay ecology.                                                _
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9.  Concentrations of organic compounds in bed sediment are greatest in the
northern Bay.  Seaward from the Patapsco River, concentrations decrease to the
Potomac River mouth.  In the southern Bay, concentrations near tributary
mouths are greater than elsewhere.
    The Susquehanna River is a source of many organic compounds.  The
compounds are likely supplied from pollution sources and atmospheric
deposition on the drainage basin, and they accumulate in the turbidity maximum
zone where fine sediment is trapped.  Accumulation at tributary mouths relates
either to the accumulation of fine sediment or to sources of contamination in
the tributaries.
    If contaminates have distinctive point sources as industrial discharges
they should be controlled pursuant to Federal and state policy.

10.  Concentrations of organic compounds are higher and more variable in the
Patapsco River than in the main Bay.
    A Patapsco River source of organic compounds is indicated by the
distribution of concentrations that are high in landward parts of the river.
Additionally, they vary as the location of sources varies within the river.
Most PNAs, however, are widespread, mixed, and lack specific sources.  Part of
the contaminated sediment is trapped within Baltimore Harbor and the Patapsco
River, but some escapes to the Bay.  This is revealed by the occurrence of a
Patapsco derived compound, 6-phenylodecane, in the main Bay.  Since
concentrations diminish seaward from the river mouth and down Bay, dispersion
of significant quantities is probably low.

11.  More than 120 organic compounds were detected in oysters from the Bay.
The compounds, methyl esters, fatty acids, and ketones, were present in most
oysters, but PNA's were scarce.
    The organic compounds in oysters may have a biogenic or natural origin.
Because the composition in oysters differs from sediments, and has fewer PNAs,
oysters are of lesser importance for general monitoring of organic compounds
in the Bay.  The oyster, however, can be useful for monitoring specific PNA
compounds as benzo(a)pyyrene which is a suggested carcinogenic compound or an
oyster metabolite.

12.  Bay-wide bioassays reveal that sediments from inner reaches of the
Patapsco and Elizabeth Rivers and from the northern-most Bay have a higher
toxicity than elsewhere.
    Effluent bioassays of fish, invertebrates, and bacteria indicate that 20
to 50 percent of the effluents sampled had moderate to high toxicity.
    The occurrence of relatively high toxicity and low survival rate generally
relates to zones of high metal content and high organic compounds in bed
sediments close to major sources.  We speculate that high sediment toxicity is
produced by a combination of high metal content and high loads of organic
compounds.  It remains to be determined what acceptable levels of sediment
pollution the Bay resources can endure.  Generally, a greater risk of toxicity
in the Bay is associated with high effluent toxicity, unless organisms can
adapt to certain concentration levels.
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                                  SECTION 8

                               RESEARCH NEEDS
                                                                                  I
                                                                                  I
    Chesapeake Bay is a very complex estuarine system,  and our knowledge of       •
hydrodynamic,  sedimentological,  and bio-ecological processes is limited.
The data gained in this study point to gaps in our knowledge that deserve
future research.                                                                  •

1.  Inasmuch as results show that some sediment-associated toxicants occur
outside major harbors (the Patapsco River and Hampton Roads) and seaward of       •
Kent Island, it remains to be determined how much material presently              •
escapes the harbors and northern-most Bay.  Is the contaminated sediment
outside the harbors a product of disposal activities or presently escaping        H
near-source contamination zones?  Do harbor contaminates contribute to            I
up-Bay, or up-tributary, contamination zones by landward transport?               *

2.  Since results show maximal particulate concentrations of abnormally           H
high Cd, Cu, Pb, and Zn in surface waters of the central Bay,  a location          •
far from major sources, it remains to be determined how they get there.
The distribution of metal in various states (dissolved, colloidal,                 M
particulate; organic or inorganic) must be determined together to                 •
demonstrate how the metals are partitioned on a seasonal basis.  We must
learn if metals stimulate production of organic matter  like plankton or, by
contrast, affect the health of organisms in the central Bay.  And,  does           •
bio-accumulation and turnover make the metals more or less mobile?                 •
                                                                                   I
3.  Whereas the present research deals mainly with metals and organic
compounds supplied to the Bay at more or less normal conditions,  episodic
events may control their distribution.  Floods,  hurricanes,  and storms can
produce exceptional conditions for massive resuspension and  dispersal of           •
sediment-borne metals.  Observations are needed  to study the impact of             •
short-term events with respect to the following:  How much sediment and
toxicant are released or mobilized by an event compared to average
conditions?  What are the corresponding effects  on marine resources?  How          I
long does it take to recover, decontaminate,  or  come to a new chemical             •
equilibrium?

4.  Synthesis results reveal that atmospheric inputs of potentially toxic          |
material can compose a significant portion of the total toxic load.  It
appears that atmospheric inputs are relatively important in  areas far from         ซ
contamination sources, especially for metals  like Cd, Cu, and Pb, and the          •
organic compound like PNAs.  We must determine,  in detail, the magnitude
and extent of atmospheric inputs relative to  water-borne inputs.   With
increasing use of fossil fuels, are atmospheric  imputs increasing the total        •
toxicant input to the Bay despite controls on water-borne inputs?  There is        •
a need to determine if atmospheric inputs are from distant sources and
homogeneous, affecting the entire Bay.  Because  atmospheric  dry and wetfall        •
collects on salt marshes, and the flux can be recorded by marsh deposits,          |
attention should focus on high marsh sediments that reflect  atmospheric
influence.  The historical record combined with  monitoring should provide          _
an early warning of increasing anthropogenic  inputs from the atmosphere.           •
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5.  To ascertain the validity of data acquired,  future efforts should
account for variability of field sampling through a rigorous statistical
sampling plan.  This study reveals that the concentrations of metals and
organic compounds can vary widely with location, especially in suspended
material.  Verifying results are needed to account for short-term tidal
variations; fortnightly, neap-spring changes; and seasonal as well as
non-periodic changes of episodic events.

6.  Chesapeake Bay has, at least on one occasion, been the recipient of the
direct disposal of pesticides like Kepone (Huggett et al.  1980).
Fortunately, the quantities were small and the assimilation capacity large
enough so that no adverse effects on the  biota were noted.  The disposal of
such compounds in this manner was, and is, illegal.  This  indicates that
laws alone are insufficient to protect the Bay and that chemical monitoring
is necessary.  The chemical monitoring of effluents and sediments collected
near outfalls shows that more effort of this type is needed to prevent
future "Kepone episodes" (Bieri et al. 1981).  Key sinks in the Bay also
require monitoring.  Because some dissolved toxicants are  difficult to
detect in near-source zones, monitoring of peripheral sediment sinks having
fast deposition can provide an early warning of increased  loading.  (For
details see separate Monitoring Recommendations, Flemmer et al.,
unpublished)
    In this study over 300 organic compounds were analyzed, but results
indicate that "thousands of other compounds are present at low
concentrations."  Therefore, monitoring needs to account for a wide
compositional range of organic compounds  having low concentrations.  These
data are needed to establish valid baselines as well as to detect anomalous
concentrations of pollutants before they  build up.  To guide State water
pollution control authorities, an effluent toxicity characterization
program is needed to screen industrial effluents for toxic chemicals and to
determine their degree of toxicity, both  acute and chronic.

7.  Additional toxicity data are needed to evaluate impacts on the Bay's
living resources and to formulate diagnostic criteria that are generally
accepted.  Little is known about the toxicity of individual components, and
less is known about the toxicity of populations or communities.  Most
bioassays have examined acute effects; little is known about long-term
chronic effects.  Moreover, the Bay ecosystem is complex and dynamic,
involving the interactions of physio-chemical parameters and biological
components with time.  We need to know if the toxicants found in the Bay
are biologically available.  Once organisms are exposed to toxicants, can
they adapt to certain concentration levels?  Most bioconcentrations have
been treated as static levels in tissues  of organisms.  Some organisms,
however, accumulate toxicants quickly, whereas others that metabolize
slowly can accumulate toxicants slowly but to high levels.  Therefore,
bioaccumulation needs to be examined as a dynamic equilbrium determined by
the metabolism rate.

8.  A major problem for future research is determining the relative
capacities of different parts of the Bay  to assimilate toxicants.  Although
a numerical model can predict the distribution and resulting concentration
of a given input and its residence time,  toxicants are subject to
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transformation and building up through biological and sedimentological            _
processes.  A single concentration level value applied to the  entire Bay is       •
not a universally valid criteria for control because it does not take into        •
account the characteristics of the receiving segment.  We need to know the
relationship between the contaminate concentrations and their  toxic  effect        •
on the biota in each receiving segment.  This requires much better data and       ||
a greater understanding than now exists.  In particular,  we need to
overcome the difficulties of:   (l) making accurate measurements of diverse        •
and potentially toxic compounds at very low concentrations; (2) measuring         •
the toxicity effects of chemicals on organisms; and (3) making valid              *
interpretations by comparing laboratory results and field observations.
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                              LITERATURE CITED


Aller, R.C.  1978.  The Effects  of Animal Sediment Interactions  on
    Geochemical Processes Near the Sediment-Water Interface.   In:
    Estuarine Interactions.  M.L.  Wiley,  ed.  Academic Press.   NY.   pp.
    157-172.


Aller, R.C.  1978.  Experimental  Studies of  Changes Produced  by  Deposit
    Feeders on Pore Water, Sediment and  Overlying Water Chemistry.
    American Journal of Science.  78:1185-1234.


Aller, R.C.  1980.  Relationships of Tube-Dwelling Benthos with  Sediment
    and Over-lying Water Chemistry.  In:  Marine Benthic Dynamics. K.R.
    Tenore and B.C. Coull, eds.   University  of  South Carolina Press,
    Columbia, SC.  pp. 285-308.


Badger, G.M.  1962.  Mode of Formation of Carcinogens in Human
    Environment.  Nat. Cancer Inst.  Monogr.  9:1-16.


Barnard, T.A., Jr.  1971.  The Role of an Anadromous Fish,  the Alewife,
    Alosa pseudoharengus (Wilson) in Pesticide  Transport. Thesis. VIMS,
    College of William and Mary,  Williamsburg,  VA.


Bean, D.J., and K.M. Duke.  1981.  Fractionation Bioassy Selected
    Chesapeake Bay Discharges. EPA 68-02-2686,  Industrial Environmental
    Research Laboratory, Office  of Energy, Minerals, and Industry, Research
    Triangle Park, NC.  170 pp.


Benninger, L.K.  1978.  210Pb Balance in Long Island Sound.   Geochim.
    Cosmochim. Acta. 42:1165-1174.


Berner, R.A.  1979.  Kinetics of Nutrient Regeneration in Anoxic Marine
    Sediments.  In:  Origin and  Distribution of the Elements. L.H. Ahrens,
    ed. Pergamon Press,  pp. 279-292.


Bieri, R.H., P. DeFur, R.J.  Huggett, W.  Maclntyre, P. Shou, C.L. Smith, and
    C.W. Su.  1981.  Organic Compounds in Surface Sediments and  Oyster
    Tissues from the Chesapeake  Bay.  Final  Report to the U.S.EPA.
    Chesapeake Bay Program,  Grant No. R  806012010, 179 pp.


Biggs, R.B.  1970.  Sources  and  Distribution of Suspended Sediment in
    Northern Chesapeake Bay.  Marine Geology. 9:187-201.


Biggs, R.B., J.C. Miller, M.J. Otely, and C.L.  Shields.  1972.  A  Mass
    Balance Model of Trace Metals in Several Delaware Watersheds.
    University of Delaware Water  Resources Center Report. 47 pp.


Bjoreth, A., and A.J. Dennis.  1979.  Polynuclear Aromatic Hydrocarbons.
    Fourth Int. Symp. Battelle Press, Columbus,  OH.


Boesch, D.F.  1977.  A New Look  at the Zonation of Benthos Along the
    Estuarine Gradient.  In:   Ecology of Marine Benthos.  B.C.  Coull, ed.
                                 352

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                                                                                  I
    University of South Carolina Press,  Columbia,  SC.   pp.  245-266.
Boesch,  D.F.  1977.   Application of Numerical  Classification in Ecological         |
    Investigations of Water Pollution.   EPA-600/3-77-033,  U.S.
    Environmental Protection Agency,  Ecological  Research  Series.   114  pp.          •

Bricker, O.P., and B.N. Troup.   1975.  Sediment-Water Exchange  in
    Chesapeake Bay.  In:  Estuarine Research. L.E.  Cronin,  ed. Academic            _
    Press, NY.  Vol.  1:3-27.                                                      •

Brush, L.  1974.  Inventory of  Sewage Treatment  Plants for Chesapeake  Bay.
    Chesapeake Research Consortium.  Publication No.  28:62.                        •

Carpenter, J. , W.L.  Bradford, and V.  Grant.   1975.  Processes Affecting the
    Composition of Estuarine Waters ("HCC>3," Fe , Mn,  Zn,  Cu, Ni,  Cr, Co,           M
    and Cd) .  In:  Estuarine Research.  L.E.  Cronin, ed. Academic  Press,            •
    NY.   Vol. 1:188-214.                                                          •

Carron,  M.J.  1979.   The Virgina Chesapeake  Bay:  Recent  Sedimentation and         I
    Paleodrainage . Ph.D. Dissertation.  Virginia  Institute of Marine Science       •
    of the College of William and Mary, Williamsburg , VA.

Chesapeake Research Consortium.  1978.   Chesapeake Bay Baseline Data              •
    Acquisition:  Toxics in the Chesapeake Bay.  Chesapeake Research
    Consortium, Inc.   Annapolis, MD.  Contr.  Rept.  238 pp.

Commonwealth of Virginia State  Water Control  Board.   1981.  Toxics Source          •
    Assessment Phase III:  Field Sampling and  Toxicity Tests for  Twenty
    Industrial and Municipal Outfalls in Virginia.  EPA-R805859,                   •
    Commonwealth of Virginia State Water Control Board.   13  pp. •*• App.             |

Cooke, M. and A.J. Dennis.   1980.  Polynuclear Aromatic Hydrocarbons.              •
    Fifth Int. Symp.  Battelle Press,  Columbus, OH.                                 •

Correll, D.L., T.L.  Wu, J.W. Pierce,  M.A. Faust, K.M  Lomax,  J.C.  Stevenson,
    and M.S. Christy.  1978.  Rural Non-Point  Pollution Studies in Maryland       I
    (Non-Point Pollution Studies on Agricultural Land Use Type  Prevalent  in       B
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Cronin,  L.E.  In press.  Pollution in Chesapeake Bay:  A  Case History  and          J
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Cronin,  L.E., D.W. Pritchard, J.R. Schubel,  and  J.A.  Sherk,  eds.   1974.
    Metals in Baltimore Harbor and Upper Chesapeake Bay and Their                 •
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Cronin,  L.E., M.G. Gross, M.P.  Lynch, and J.K. Sullivan.   1977.  The
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Davis, A.O., and J.N. Galloway.  1981.   Atmospheric Lead and Zinc

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Douglas, J.E., Jr.  1979.  Summary Report of the Select  Inter-Agency Task
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Eaton, A.  1979.  Impact of Anoxia on Mn Fluxes in Chesapeake Bay.
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Eaton, A., V. Grant, and M.G. Gross.  1980.   Chemical Tracers for Particle
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EPA Region II Water Quality Standards Office.  1980.   Summary Table for All
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Ferri, K.  1977.  Input of Trace Metals to Mid-Chesapeake Bay from Shore
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Fisher, Allan C., Jr.  1980.  My Chesapeake—Queen of Bays.  National
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Frazier, John M.  1972.  Current Status of Knowledge of  the Biological
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    1981.  Trace Metals:  A Review and Assessment.  In:   Proceedings of
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Gianessi, Leonard.  1981.  Pollution Matrix Lookup Routine.  Unpublished
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Goldberg, E., V. Hodge, J. Griffin, E.  Gamble,  0.  Bricker, G. Mattisoff, G.
    Holdren, and R. Braun.  1978.  A Pollution History of Chesapeake Bay.
    Geochimea et Cosmochimica Acta. 42:1413-1425.


Goldberg, E.D., V.T. Bowen, J.W. Farrington, G. Harvey,  J.H. Martin, P.L.
    Parker, R.W. Risebrough, W. Robertson, E. Schneider,  and E.  Gamble.
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Gouldii on the Intertidal Sediments of Barnstable Harbor.   Limnology          •
Grimmer, G. and H.  Boehnke.   1972.   Determination of Polycyclic  Aromatic           •
    Hydrocarbons in Atmospheric Dust and Automotive-Exhaust Gas  by                g
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Hansen, D.J., P.R.  Parrish,  and J.  Forester.   1974.   Aroclor 1016:                 •
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Hase, A.,  and R.A.  Hites.  1976.  Identification  and Analysis of Organic           |
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Helz, G.  1976.  Trace Element Inventory For  the  Northern Chesapeake  Bay.          •
    Geochimea et Cosmochimica Acta.  40:573-80.

Helz, G.R., R.J. Huggett, and J.M.  Hill.  1975.   Behavior of Mn, Fe,  Cu,           •
    Zn, Cd, and Pb.  Discharged From Waste-Water  Treatment Plant into an           •
    Estuarine Environment.  Water  Res.  9:631-636.

Helz, George R., Scott A. Sinex, George H.  Setlock,  and Adriana  Y.                 •
    Cantillo.  1981.  Chesapeake Bay Sediment  Trace  Elements. University  of
    Maryland.  College Park, MD.  202 pp.
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Hill, James M., and Robert D. Conkwright.  1981.   Chesapeake Bay Earth            •
    Science Study:   Interstitial Water Chemistry. EPA-R805963.   59 pp.

Holland, A.F., N.K. Mountford, and J.A. Mihursky.  1977.  Temporal                |
    Variation in Upper Bay Mesohaline Benthic  Communities.   Chesapeake
    Science. 18:370-378.                                                          •

Huggett, R.J., F.A. Cross, and M.E. Bender.  1974.  Distribution of Copper
    and Zinc in Oysters and Sediments From Three  Coastal-Plain Estuaries.
    In: Proceedings of a Symposium on Mineral  Cycling in Southeastern             •
    Ecosystems. Augusta, GA.  pp.  224-238.                                         •

Huggett, R.J., M.E. Bender,  and H.D. Stone.  1971.  Mercury in Sediments
    from Three Virginia Estuaries.  Chesapeake Science.  12:280-282.
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Huggett, R.J., M.M. Nichols, and M.E. Bender.   1980.   Kepone Contamination         _
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    Workshop Report on Toxic Substances.  Proc.  Bi-State  Conference on
    Chesapeake Bay. Chesapeake Research  Constorium. Publication No.
    61:121-127.


Huggett, Robert J., and Michael E.  Bender.   1980.   Keypone in the James
    River. Environmental Science and Technology.  14(8):  918-923.


Johnson, Patricia G.,  and Ortero Villa,  Jr.   1976.   Distribution of Metals
    in Elizabeth River Sediments.  EPA 903/9-76-023, U.S. Environmental
    Protection Agency.  Annapolis,  MD.  88 pp.


Keefe, C.W., D.A. Flemer, and D.H.  Hamilton.  1976.  Seston Distribution in
    the Patuxent Estuary.  Chesapeake Science.  17(1):56-58.


Kingston, Howard M., Robert R. Greenberg,  Ellyn S.  Beary, Billy R. Hardas,
    John R. Moody, Theodore C. Rains, and  Walter S. Liggett.  1982.  The
    Characterization of the Chesapeake Bay:   A Systematic Analysis of Toxic
    Trace Elements.  EPA-79-D-X-0717.  67  pp.


Lang, D.J. and D. Grason.  1980.  Water  Quality Monitoring of Three Major
    Tributaries of the Chesapeake Bay -  Interim Data Report.
    USGS/WR1-80-78, U.S. Geological Survey,  Towson, MD.   66 pp.


Lazrus, A.L., E. Lorange, and J.P.  Lodge,  Jr.  1970.  Lead and Other Metal
    Ions in United States Precipitation.  Environmental  Science and
    Technology. 4:55-58.


Lerman, A.  1979.  Geochemical Processes Water and  Sediment Environments.
    John Wiley & Sons. NY.  481 pp.


Loi, T.N., and B.J. Wilson.  1979.   Macroinfaunal  Structure and Effects of
    Thermal Discharges in a Mesohaline Habitat of  Chesapeake Bay, Near
    Nuclear a Power Plant.  Marine Biology.   55:3-16.


Lunde, G. , and A. Bjorseth.  1977.   Polycydic Aromatic  Hydrocarbons in
    Long-range Transported Aerosols.   Nature.  268(5620):518-519 .


Lunde, G., J. Gether,  N. Gjos, and M-B.  S.  Lande.   1976.   Organic
    Micropollutants in Precipitation in  Norway.   In:  Atmospheric
    Environment.  Vol. 11.  Pergamon Press,  G.B. 1007-1014.


Lunsford, Charles A.  1981.  Kepone Distribution in the  Water Column of the
    James River Estuary—1976-78.  Pesticides Monitoring  Journal.
    14(4):119-124.


Lunsford, C.A., C.L. Walton, and J.W. Shell.  1980.  Summary of Kepone Study
    Results—1976-1978.  Bulletin No. 46.  Virginia  State  Water Control
    Board.  83 pp.


Matisoff, G., O.P. Bricker, G.R. Holdren,  and P. Kaerk.   1975.   Spatial and
    Temporal Variations in the Interstitial  Water Chemistry of Chesapeake
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    Environmental Framework of Coastal Plain Estuaries.   B.  Nelson,  ed.
    Geological Society of America Memoir. 133.  pp. 169-212.
    1980.  The Biogenic Structure of Lower Chesapeake Bay Sediments.  EPA
    R805982-01-0.  U.S. Environmental Protection Agency.  103 pp.
                                                                                   I
    Bay Sediments.  In: Marine Chemistry of the Coastal Environments.  T.M.
    Church, ed. American Chemical Society Symposium Series.  18:343-363.             •

McCaffrey, Richard J.,  and John Thomson.  1980.  A Record of Sediment  and
    Trace Metals in a Conneticut Salt Marsh.  In:  Estaurine Physics and           •
    Chemistry:   Studies in Long Island Sound.  Bary Saltzman, ed.  Academic          |
    Press, NY.  pp. 165-236.

Monsanto Research Corporation. Toxic Point Assessment of Industrial                •
    Discharges  to the Chesapeake Bay Basin.  Phase III:   Protocol
    Verification Study.  EPA-68-02-3161, Monsanto Research Corporation,
    Dayton, OH.  Preliminary draft.  Vol I.  86 pp.                                I

Munson, T.O.  1976.  Upper Bay Survey.  Westinghouse Electric Corporation.
    Oceanic Division.  Annapolis, MD. Vol. 1.   54 pp.                              •

Munson, T.O.  1973.  Chester River Study:  A Joint Investigation by the
    State of Maryland Department of Natural Resources and Westinghouse
    Electric Corporation.  W.D. Clarke, H.D. Palmer, and L.C. Murdock, eds.         •
    Westinghouse Ocean Research Laboratory.  Annapolis,  MD.   Vol. 111:9-27.         •

Munson, T.O.  1975.  Upper Bay Survey, Final Report to the Maryland
    Department  of Natural Resources.  T.O. Munson, O.K.  Ela, and C.
    Rutledge, eds. Westinghouse Oceanic Division.  Annapolis, MD.  Vol.
    2:1-36.                                                                        _

Munson, Thomas  0., and Robert J. Huggett.  1972.  Current Status of
    Research on the Biological Effects of Pesticides in Chesapeake Bay.
    Chesapeake Science.  13(12):154-156.                                           I

Nichols, M.  1972.  Sediments of the James River Estuary.  In:
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    Flood. Journal of Sedimentary Petrology.  47:1171-1186.                         •

Nichols, Maynard M.,  and Norman H. Cutshall.  1979.   Tracing Kepone
    Contamination in James Estuary Sediments.  In:   Proceedings of                 •
    International Council for the Exploration of the Sea,  Workshop on              ป
    Sediment and Pollution Interchange in Shallow Seas. Texel,  the
    Netherlands.  Paper No. 8.                                                     •

Nichols, Maynard, Richard Harris, and Galen Thompson.  1981.  Significance
    of Suspended Trace Metals and Fluid Mud in Chesapeake Bay.   EPA                _
    R806002-01-1, U.S. Environmental Protection Agency.  Annapolis, MD.            •
    129 pp.                                                                        •

Nielsen, K.I., R.J. Diaz, D.F. Boesch, R. Bertelsen, and M.  Kravitz.               •
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    Strata in an Allochthonous Shelf Environment:   The Washington
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O'Connor, Donald J., and John A.  Mueller, Eds.   1981.   Modeling of Toxic
    Substances  in Natural Water Systems.  In:   Twenty-Sixth Summer Institute
    in Water Pollution Control, Bronx.  NY.  186 pp.


Owens, J.P., K.  Stefansson, and L.A. Sirkin.   1974.  Chemical,  Mineralogic,
    and Palynologic Character of the Upper Wisconsinan-Lower Holocene Fill
    in Parts of  Hudson, Delaware, and Chesapeake Estuaries.   Journal of
    Sedimentary  Petrology.  44:390-408.


Palmer, H.D.  1974.  Estuarine Sedimentation,  Chesapeake Bay,  Maryland.  In:
    International Symposium on Interrelationships of  Estuarine and
    Continental  Shelf Sedimentation.  Bordeaux, France.  pp. 215-224.


Pearson, T.H.,  and R. Rosenberg.   1978.   Macrobenthic  Succession in

    Relation to  Organic Enrichment and Pollution of the Marine
    Environment.  Oceanography and Marine Biology Annual Review.
    16:229-311.


Petrasek, Albert C.  Distribution and Removal  of Metal in a Pilot-Scale
    POTW.  Municipal Environmental Research Laboratory, Office of Research
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Petrasek, Albert C., Jr., Barry M. Austern, Thomas A.  Pressley, Lawrence
    A. Winslow,  Robert H. Wise.  1980.   Behavior of Selected Organic
    Priority Pollutants  in Wastewater Collection and  Treatment Systems.
    Presented at the WPCF 53rd Annual Conference, Las  Vegas, NV.  28 pp.


Pheiffer, T.H. ,  O.K. Donnelly, and D.A.  Possehl.  1972.  Water Quality
    Conditions In the Chesapeake Bay System.  EPA Tech. Rept. 55, U.S.
    Environmental Protection Agency.  Annapolis, MD.   313 pp.


Randall, C.W.,  R. C. Hoehn, T.J.  Grizzard, S.P. Gawlik, Jr., D.R. Helsel,
    and W.D. Lorenz, Jr.  1981.  The Significance of  Heavy Metals in Urban
    Runoff Entering the Occoquan Reservoir.  Bull. No. 132.  Virginia Water
    Resources Research Center, Virginia Polytechnic Institute and State
    University.


Reinharz, E., and A. O'Connell.  1981.   Animal-Sediment Relationships of
    the Upper Chesapeake Bay.  EPA R805964,  U.S. Environmental Protection
    Agency.   71 pp.


Rhoads, D.C.  1963.  Rates of Sediment Reworking By Yoldia limatula in
    Buzzards Bay Massachusetts and Long Island Sound.   Journal of
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Roberts,  M.H.,  and R.  Bendl.   1980.   Acute Toxicity of Kepone  to Selected         •
    Freshwater  Fishes.  VIMS  Manuscript.

Schmeltz, I.,  and D. Hoffman.   1976.   Formation of Polynuclear Aromatic            •
    Hydrocarbons from Combustion of  Organic Matter.  In:   Carcinogenesis.
    R.I.  Freudenthal and P.W.  Jones,  eds.   Raven Press, NY.  1:225-239.            •

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    Chesapeake  Bay:  Some Observations.   The Coastal Society.  Proc.  Second
    Annual Confr.  New Orleans,   pp.  70-115.                                      •

Schubel,  J.R.,  and D.J.  Hirschberg.   1977.   Pb-210 Determined  Sedimentation
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                                                                                   I
Schubel, J.R.,  and R.H.  Meade.   1974.   Man's Impact on Estuarine                   _
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    University of  Maryland,  Towson, MD.   38 pp.

Smethie, W.M., Jr.,  C.A.  Nittrouer, and  R.F.L.  Self.   1981.   The Use of            •
    Radon-222 As a Tracer of Sediment Irrigation and  Mixing On  the
    Washington Continental Shelf.  Marine Geology.  42:173-200.                     •

Sommer, S.E. and A.J.  Pyzik.  1974.   Geochemistry of  Middle Chesapeake  Bay
    Sediments For Upper Cretaceous to Present.   Chesapeake Science.                 _
    15:39-44.                                                                      •

Thornton, J.D., S.J.  Eisenreich,  J.W. Munder,  and E.  Gorham.  1981.   Trace
    Metal and Strong Acid Composition of Rain  and Snow in Northern                  B
    Minnesota.  In:   Atmospheric  Pollutants in Natural  Waters.  S.J.                 •
    Eisenreich, ed.   Ann Arbor Science Publishers,  Inc.,  MI.  pp. 261-284.

Tsai, C., J. Welch,  K. Chang, J.  Schaeffer, and L.E.  Cronin.  1979.                 E
    Bioassay of Baltimore Sediments.   Estuaries 2(3):141-153.

Toxic Work Group.  Plan of Action for  Accumulation in  the  Food Chain.               •
    1978.  Unpublished Manuscript. U.S. Environmental Protection Agency,           •
    Chesapeake Bay Program.   Annapolis,  MD.  23 pp.


    Institute of Marine Science,  Gloucester Point.   24 pp.

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    Chesapeake Bay Earth Science Study Sediment  and Pore Water Chemistry.
    EPA-R8059660, College of William and Mary, Williamsburg,  VA.    166  pp.


U.S. Environmental Protection Agency.   1977.  Evaluation of the Problem
    Posed by In-Place Pollutants in Baltimore Harbor and Recommendation of
    Corrective Action.   EPA-440/5-77-015A,  Washington,  DC.   64 pp.


U.S. Environmental Protection Agency.   1978.  The Feasibility of  Mitigating
    Kepone Contamination In the James  River Basin.   EPA Office of Water and
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U.S. Environmental Protection Agency.   1974.  Methods for Chemical Analysis
    of Water and Wastes. EPA-625/6-74-003,  Washington,  DC.  82 pp.


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    Harbor Sediments.  U.S. Environmental Protection Agency,  Annapolis
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Virnstein, R.W.  1977.  The Importance of Predation By Crabs  and  Fishes on
    Bethnic Infauna In Chesapeake Bay.  Ecology.   58:1199-1217.


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    Chesapeake Bay. NASA, Greenbelt, MD.  NAS5-20961.  44 pp.


Wilson, S.C., B.M. Hughes, and G.D. Rawlings.  1981.  Toxic Point Source
    Assessment of Industrial Discharges to the  Chesapeake Bay Basin.  Phase
    III:  Protocol Verification Study. EPA-68-02-3161,  Monsanto Research
    Corporation, Dayton, OH.  Preliminary draft.   Vol.  11:396 pp.


Wilson, S.C., B.M. Hughes, and G.D. Rawlings.  1981.  Toxic Point Source
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Wilson, S.C., B.M. Hughes, and G.D. Rawlings.  1981.  Toxic Point Source
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    Corporation, Dayton, OH.  Preliminary draft.   Vol.  IV:467 pp.


Wilson, S .J. , J.J. Brooks, D.W. Dunn,  J.A.  Gridley, F.A. Kulik, J.V.
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    and M. Kemp.  1981.  Seston Dynamics and a Seston Budget for the               ™
    Choptank River Estuary in Maryland.  University of Maryland, Horn Point
    Envir. Lab, Cambridge, MD. and Maryland Department of Natural                 B
    Resources, Tidewater Administration. 220 pp.                                  •

Youngblood, W.W., and M. Blumer.  1975.  Polycyclic Aromatic Hydrocarbons          •>
    in the Environment:  Homologous Series in Soil and Recent Marine               •
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                                 361
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-------
APPENDIX B
SUMMARY OF DATA SOUCES FOR TRACE METALS IN
THE
CHESAPEAKE BAY AND TRIBUTARIES


Area

James, York,
& Rappahannock
Rivers
Potomac River


James River
Northern Bay
(1974)
Patapsco River
& Balto. Harbor
Northern Bay
(1974)
Northern Bay


Northern Bay
& Susquehanna

Central Bay

Back River

Northern Bay
Rappahannock
River (





Reference

Huggett et al.
(1971)
Pheiffer (1972)


Hugget t
& Bender (1975)
Owens et al.
Villa &
Johnson (1974)
Sommer & Pyzik

Cronin
(1974)

Carpenter


Matisoff (1975)

Helz et al.
(1975)
Helz (1975)
Huggett et al.
1975)





Metals

Hg

Ag,Ba,Cd,Co,Cr,
Cu,Fe,Li,Mn,Ni,
Pb,Sr,V,Zn
Cu.Zn
B,Ba,Ce,Cr,Mn,V
Zn.Zr
Cd,Cr,Cu,Hg,Mn,Ni
Pb,Zn
Co,Cu,Ni,Pb,V

Fe.Mn.Zn


Co,Cr,Cu,Fe,Mn,Ni,
(1975)
Zn.Cd.Pb
Fe , Mn

Cd , Cu , Fe , Mn , Pb , Zn

Cd,Co,Cr,Cu,Pb,Fe
Mn.Ni.Zn
Cu.Zn


365


Component
Bed Sediments

Bed Sediments


Oysters & Bed
Sediments
Bed Sediments
Bed Sediments

Bed Sediments

Bed Sediments


Dissolved and

Suspended
Sediment
Interstitial
Sediment &
Water
Bed Sediments

Bed Sediments
Bed Sediments



1
1



1

I



1
1

1

1





1
1

•

1
1
1
1
1

-------
1
1

1

1

1
w

1

1

1
w
1
1


1
1
1
I
1
1
1
1


(APPENDIX B, CONTINUED)
Area Reference Metals

Northern Bay Matisoff et al.
(1975)
Rhode River Frazier Cd ,Cu,Fe,Mn,Zn
(1976)
Elizabeth Johnson & Cd ,Cr,Cu,Hg,Pb, Zn
River Villa (1976)
Patuxent River Ferri (1977) Cd ,Co,Cr,Cu,Fe,
Mn,Ni,Pb,Zn
Northern Bay Schubel and Cr,Cu,Ni,Pb
Hirschberg (1977)
Patapsco River EPA-A40/5-77-015A As , Cd ,Cr,Cu,Hg,
& Balto. Harbor Mn,Ni,Pb,Zn
Northern Bay Goldberg et al. Ag,Al,Cd,Co,Cr,Cu,
(1978) Fe,Mn,Ni,Pb,Zn,V
Northern Bay Eaton et al. Mn
(1979)
Northern Bay Eaton (1980) Fe.Ti.Zn









366



Component


Bed Sediments

Bed Sediments

Bed Sediments

Bed Sediments

Bed Sediments

Bed Sediments
Dissolved Bed
Sediments
Suspended
Sediments










-------




APPENDIX C.




Area
Chesapeake Bay &
Selected Tribs.
James ,
Rappahannock,
& Potomac Rivers
Chester River

Northern Bay



Cape Charles,
Lynnhaven Bay

James River

James River


James River


James River
James River







SUMMARY OF DATA
IN CHESAPEAKE



Reference
Munson &
Huggett (1972)
Barnard (1971)


Munson (1973)

Munson (1975)



Goldberg et al.
(1978)

U.S. EPA (1978)

Huggett (1980)


Huggett &
Bender (1980)

Lunsford (1980)
Nichols &
Gutshall (1981)






FOR ORGANIC CHEMICALS
BAY AND TRIBUTARIES



Organic Chemicals
DDT compounds
DDT compounds


PCBs,
Chloradane,
DDT
PCBs
Chloradane
DDT

PCBs
DDT compounds
PNAs, DAHs
Kepone

Kepone


Kepone


Kepone
Ke pone






367




Component
Oysters
Fish


Sediments
Shellfish

Sediments
Shellfish
Zooplankton

Oysters


Soil, water,
Bed sediments
Bed sediments
& biota

Biota, Bed
sediments ,
Suspended
sediments
Bed sediments
Bed sediments







1
1
1
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1

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-------
                                 APPENDIX F
          RESULTS OF FISH BIOASSAYS FOR EFFLUENT SAMPLES BY SPECIES
Toxic ity Index _ Fathead Minnow _ Sheepshead Minnow _ Totals

Minimal                        14                      3              17
75-NT2*
Low                             3                                      3
Moderate                        2                                      2
25-49
High                           _3                                     _3
0-24


Totals                         22                      3              25
   NT is not toxic; a 100% effluent concentration did not kill 50% of the
    test species.
                                 APPENDIX G.


      RESULTS OF INVERTEBRATE BIOASSAYS FOR EFFLUENT SAMPLES BY SPECIES
Minimal                       9                   18                 27
75-NT2*
Low                           2                    8                 10
50-74
Moderate                      2                    46
25-49
Totals                       15                   41                 56
*NT2 is not toxic; a 100% effluent concentration did not kill at least
 50% of the test species.
                                                                                  I
                                                                                  I
                                                                                  I
                                                                                  I
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                                                                                  I
                                                                                  I
                                                                                  I
                                                                                  I
                                                                                  I
	=      I
Toxicity Index	Daphnia (Magna)	Mysid Shrimp	Total          _
                                                                                   I

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                                              APPENDIX H.

                               RESULTS OF BACTERIAL AND GRASS BIOASSAYS
           Minimal                          5
           75-NT
           Low                             1
           50-74
           Moderate                        1
           25-49
           High                            5
                                          12
 •         Toxicity Index	Microtox (Marine Bacteria)	Thalassia (Sea Grass)

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                                                376

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                                 APPENDIX I.


        RESULTS OF SALMONELLA/MICROSOMAL ASSAYS FOR MUTOGENICITY OF

                       CHESAPEAKE BAY EFFLUENT  SAMPLES

Plant Number/Sample
Filtrate I*
A101
A102
A103
A104
A106
A107
A108
A109
Filtrate II**
A100
A105
A110
Particulate *** - Acetone
A100
A101
A102
A103
A104
A105
A106
A107
A108
A109
A110
Spot Test

(-) negative
(-) negative
(-) negative
(-) inconclusive
(-) negative
(-) negative
(-) negative
(-) negative

0
-
—
Extract
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Not performed
Plate Incorporation

(-) negative
(-) negative
(-) negative
(-) negative
(-) negative
(-) negative
(+) positive
(-) negative

_
-
-

negative
negative
negative
negative
negative
negative
negative
negative
negative
negative
negative

*   Filtrate I - Filtrate from initial filtering through a .45  u filter.
**  Filtrate II - Filtrate I passed through a 0.2 u filter.
*** Particulate - Material retained on polyester drain disc  and a 5  u

    teflon filter.
                                      377
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                                  APPENDIX  J.


                            RESULTS OF MAMMALIAN  CELL

                         CLONAL ACUTE CYTOTOXICITY ASSAY

Neat Effluents
Sterilized by
Filtered
Sterilized
Antibiotic Addition Effluents
Sample
Number
A100
A101
A102
A103
A104
A105
A106
A107
A108
A109
A110
EC50>a
pL/mL
150
ND
Ce
ND
ND
25
45
ND
C
C
55
Toxicity ฃ€59 Toxicity
rating pL/raL rating
LC NDd
ND
200 L
200 L
250 L
MS ND
M 200 L
ND
200
ND
M 200
Particulate
Extract, Acetone
Concentrate
EC5Q,bToxicity
pL/mL rating
600
ND
ND
700
ND
ND
300
650
700
ND
300
L


VLf


L
VL
VL

L

Effective concentration at 50% killing


 Normalized to toxicity of particulate extracts recovered from 1,000 mL
 of neat sample.


cLow, 60-600 pL/mL.


 No toxicity found at highest concentration tested and with no
 contamination.


eMicrobial contamination; toxicity not determined.


fVery low, 600pL/mL


^Moderate, 6-60PL/mL
                                     378

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          PART IV


SUBMERGED AQUATIC VEGETATION
       Robert J.  Orth
       W. R. Boynton
      K. L. Heck, Jr.
         W.  M.  Kemp
        J.  C. Means
        T. W. Jone s
      J. C. Stevenson
     Richard L. Wetzel
      Robin F.  VanTine
      Polly A.  Penhale
   Technical Coordinators


      Walter Valentine
        David Flemer
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      Kenneth A.  Moore                                     •
          379
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                                 INTRODUCTION
    This part of the GBP's scientific synthesis summarizes and integrates
almost three years of research on t:he occurrence of submerged aquatic
vegetation (SAV) in Chesapeake Bay,, the role and value of SAV in the
Chesapeake Bay ecosystem, and major factors controlling SAV's past and
future survival.  The four chapterป cornstituting the SAV part draw on the
findings of over a dozen separate research projects, each of which has
produced a final report containing a detailed account of research design,
methods, and results.  These projects are listed in Appendix A.  In
addition to GBP-funded research, this part includes information from other
research as well as from personal communications.
    The CBP included SAV as a critical research area because of its
ecological role and value, its precipitous decline during the 1970's, and
the urgent need to discover why the grasses were disappearing.  The life
history of SAV and its decline in Chesapeake Bay have been fully presented
in a 1978 Summary of Literature on SAV in Chesapeake Bay (Stevenson and
Confer).  The papers presented here seek to further clarify the SAV
problems presented in the 1978 Summary and to suggest reasons for its
decline.
    Four features of SAV's role in the Bay — food source, habitat,
nutrient buffer, and sediment trap — illustrate its ecological
importance.  As a food source, SAV had a partly documented,  partly assumed
role in the ecology and economy of Chesapeake Bay.  SAV is eaten by ducks,
geese, and some fish, and it contributes to the detritus-based food web.
SAV also provides habitat for many organisms—nurseries for  juvenile stages
of some fish species; refuge for molting blue crabs, other invertebrates,
and certain fish species; a stable habitat for infauna; a substrate for
epiphytic plants and animals; and a habitat for all fauna subsisting
directly on SAV and its epiphytes, or the detritus derived from them.
Additionally, SAV was thought to buffer nutrients in the Bay by absorbing
nutrients from the water column during spring runoff and releasing them in
autumn as detritus.  SAV was also considered to be a nutrient "pump,"
taking up nutrients from the sediment through its roots and  releasing them
as detritus.  Other presumed functions of SAV were the baffling of water
movement, causing sediment to settle to the bottom, and the  binding of
sediment, helping to mediate shoreline erosion.
    The most compelling evidence for the decline of SAV during the 1970's
is an upper-Bay annual summer submerged vegetation survey conducted by the
U.S. Fish and Wildlife Service and the Maryland Department of Natural
Resources and an aerial mapping survey of the lower Bay SAV  conducted by
the Virginia Insitute of Marine Science (VIMS).  The Maryland survey shows
that 28.5 percent of 640 sample stations had SAV in 1971,  whereas only 21
percent had SAV in 1972, 10.5 percent in 1973,  and 14.9 percent in 1974
(Kerwin et al. 1976).  This survey covered the entire Maryland portion of
the Bay, except the Potomac River, making it by far the most extensive
survey available.  The aerial survey of lower Bay SAV shows  dramatic
declines in the Rappahannock, Piankatank, and York Rivers between 1971 and
1974 (Orth and Gordon 1975).  The 1970's decline was especially alarming
because it affected all areas and all species,  though not all to the same
degree, something not observed in previous distribution shifts.   The only
other documented major perturbations were the decimation of  eelgrass
(Zostera marina) in the 1930's presumably caused by a disease organism and
                               380

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                                                                                  I
the outbreak of Eurasion milfoil (Myriophyllum spicatum) in the late 1950's
and early 1960's.  These changes directly affected only one species.              .
    In our search for reasons for the Bay-wide SAV decline, we assumed that       •
one or more fundamental properties of the Bay ecosystem were being                *
altered.  Disease was ruled out because it probably would not have affected
all species.  Point sources of pollution, although they may have been a           •
contributing cause, were probably not the direct underlying cause because         •
of their localized nature.   We conjectured that herbicides from
agricultural runoff were directly harming SAV, that sediment loading was          •
increasing turbidity thereby decreasing the amount of light available to          •
SAV,  and that nutrient loading to the system was stimulating the growth of
phytoplankton, which were further shading the SAV and competing for               _
nutrients.  One of the disturbing features of these working hypotheses was        •
that they pointed to a gradual and fundamental change in the Bay,  thought         '
to be brought about largely by the increased human activity associated with
a population growth of more than 100 percent in the Bay area during the           B
last 40 years.                                                                    f|
    Following the decision to include SAV as a study area in the GBP, a
Plan of Action that set forth the goals and objectives of the study was           ซ
developed.  The study's ultimate goal was to develop a plan for managing          I
the Bay system to maintain SAV as a viable resource.  To meet that goal, we
conducted basic research on the structure and function of SAV-based
ecosystems, including inventories of the biota and observations of ambient,       •
abiotic variables in SAV beds and at nearby sites that were devoid of SAV         •
but otherwise similar.  In addition to observations of the natural
ecosystem, manipulative studies were designed in the field and laboratory         •
on system dynamics.  These manipulative studies aimed at better                   |
understanding the role and value of SAV and the factors controlling its
growth and survival.  This latter information would elucidate causes of the       ^
recent decline in SAV, as well as the requirements for future survival.           I
Finally, interpretation of aerial photography and analysis of SAV seeds in
Bay bottom cores were to be used to investigate current and past
distribution and abundance of SAV.  This information would put in                 •
historical perspective the magnitude of the current decline and provide a         •
baseline against which to measure future changes.
    The following four papers are organized around fundamental questions of        •
interest to someone charged with managing this valuable resource.   The             •
first question is:  Is there a problem concerning SAV in Chesapeake Bay?
To answer this, one first must show that there has been a decline in SAV           ^
that is different in character or degree from natural fluctuations.  The           •
first paper addresses this point.  Second, one must show that SAV has some         ™
value and that its loss will have negative ecological and economic
impacts:  the subject of the second paper.  If there is a problem, the next        •
question must be:  What caused it?  As stated above, we explored various           •
hypotheses about the decline.  Separate papers (three and four) are devoted
to herbicides and light as they were thought to be the most likely causes.         M
A list of the detailed Management Questions and answers appears at the end         •
of the SAV synthesis.
                                  387
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abiotic:


anoxia:


biotic:


copepod:



denitrification:



detritus:


dinoflagellate:



fluvial:


halocline:



nonpoint source:




point source:




primary producitivity:



rotifer:




Secchi depth:




watershed:
       Technical Glossary



Without life, inorganic.


Total deprivation of oxygen.


Of life, or caused by living organisms.


Small, sometimes parasitic, Crustacea living in either
salt or fresh water.


Single-celled organism, mainly marine and often with a
cellulose shell.


Accumulation of disintegrated material, or debris.


Single-celled organism, mainly marine and often with a
cellulose shell.


Of, found in, or produced by a river.


A level of marked change, especially increase,  in the
salinity of seawater at a certain depth.


Source of a nutrient or other constituent coming from
diffuse areas such as pasture and forests, and
atmosphere.


Source of nutrients or other constituents coming from
a distinct source such as a pipe from a sewage
treatment plant.


The amount of organic matter made in a given time by
the autotrophic organisms in an ecosystem.


Microscopic invertebrate animal found mostly in fresh
waters, having one or more rings of cilia at the front
end to the body.


Depth at which a Secchi disk can be seen.  The  Secchi
disk is an instrument for measuring the light
attenuation of natural waters.


The area drained by a river or river system.
                                382

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                  TECHNICAL SYMBOLS
C
cm
CW
d
g
h
ha
kg
km
L
LAI
m
M
ug-at
uE
umoles
MLW
mm
NADPH2

nm
pMax
ppb
ppm
ppt
sec
y
   Celsius
   centimeter
   carapace width
   day
   gram
   hour
   hectare
   kilogram
   kilometer
   liter
   leaf area index
   meter
   molar
   microgram atom
   micro-Einstein
   micro-moles
   mean low water
   milimeter
   coenzyme reducing carbon dioxide
   to sugar in photosynthesis
   nanometer
   maximum rate of photosynthesis
   parts per billion
   parts per million
   parts per thousand
   second
— year
                   383
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  DISTRIBUTION AND ABUNDANCE OF SUBMERGED AQUATIC
VEGETATION IN CHESAPEAKE BAY:  A SCIENTIFIC SUMMARY
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                                                 by
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I                                Robert J. Orth and Kenneth A. Moore
                                Virginia  Institute of  Marine  Science
                                 of the College  of William and  Mary
•                               Gloucester Point, Virginia  23062
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                  384

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                                  CONTENTS
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Figures	386
Tables	"	387
Sections
    1.  Introduction	388
    2.  Methods	390
    3.  Present Distribution  	  392
    4.  Past Distribution	397
           Historical Trends (1700-1930)   	  397
           Recent Past (1930-1980)  	398
              The Eelgrass Wasting Disease 1931-1932   	  398           •
              The Milfoil Problem 1959-1965 	  399           •
              The Bay-wide Problem 1960-1980	401
                1965	403           •
                1965-1970	403           |
                1970-1975	406
                IP 75-1980	415           g
    5.  The Atlantic Coast	418           •
    6.  Worldwide Patterns  	  420
    7.  Conclusions	422
Literature Cited  	  426           •
                                  385
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FIGURES
Number
1 Map of Chesapeake Bay showing the lower, middle, and

2 Map of the mouth of the East River and a portion of Mobjack Bay


4 Population fluctuations of watermilfoil compared to the


5 Distribution of SAV in Chesapeake Bay ~ 1965 	 	 . .



8 Trends in SAV occurrence in the Maryland portion of


9 Trends in SAV occurrence in six areas in the middle Bay

10 Changes in the distribution and abundance of SAV at the

11 Trends in SAV coverage in the lower zone of Chesapeake
Bav 	

12 Distribution of SAV in Chesapeake Bay - 1980 	

13 Pattern of recent changes in the distribution of SAV in
Chesapeake Bay 	 	 	
14 Location of sections of the Bay with the greatest SAV decline. .





386


Page

391
393
400
T V \J

402

404
405-

407

409


411
412


416

417


423
424







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                                   TABLES
Number                                                             Page
1   Species Associations of SAV in Chesapeake Bay	339
2   Numbers of Hectares of Bottom Covered with SAV in                              •
     Chesapeake Bay,  1978	394           ™
3   Numbers of Hectares of Bottom Covered with SAV in the                          •
     Lower Bay Zone,  1971-1980	395           •
4   Changes in Harvested Scallops, 1928-1981  	  399           g
5   Percent of Sampled Stations Containing SAV in the Maryland
     Section of Chesapeake Bay	408


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                                  SECTION 1  .

                                 INTRODUCTION
    The Chesapeake Bay, with its extensive littoral zone and broad salinity
regime of 0 to 25 ppt, supports many different species of submerged aquatic
vegetation (SAV) (Anderson 1972, Stevenson and Confer 1978, Orth et al.
1979).  Approximately ten species of submerged vascular plants are abundant
in the Bay, with another ten species occurring less frequently.  In many
areas, more than one species is found in a particular bed of SAV because of
the similarity in the physiological tolerances of some species.  Between
regions of the Bay, salinity appears to be the most important factor in
controlling the species composition of an individual bed of SAV (Stevenson
and Confer 1978), while sediment composition and light regime are important
factors in controlling the distribution of SAV within regions of the Bay.
All species, regardless of the salinity regime, are found in regions of the
Bay's littoral zone and are located in water less than two to three meters
deep (mean low water - MLW), primarily because of low levels of light that
occur below these depths (Wetzel et al. 1981).
    Three associations of SAV can be described in Chesapeake Bay based on
their salinity tolerances as well as on their co-occurrence in mixed beds
of SAV (Table 1) (Orth et al. 1979, Stevenson and Confer 1978).  The first
association, consisting of Najas guadalupensis (bushy pondweed),
Ceratophyllum demersum (coontail),  Elodea canadensis (waterweed), and
Vallisneria americana (wildcelery), contains species that can tolerate
fresh to slightly brackish water and are found in the upper reaches of the
Bay and in the tidal freshwater areas of the Bay tributaries.  The second
association, including Ruppia maritima (widgeon grass), Myriophyllum
spicatum (Eurasian watermilfoil), Potamogeton pectinatus (sago pondweed),
Potamogeton perfoliatus (redhead grass), Zannichellia palustris (horned
pondweed), and Vallisneria americana (wildcelery),  is tolerant of slightly
higher salinities than the first group.  This group is found in the middle
reaches of the Bay and its tributaries.  The third  group, consisting of
Zostera marina (eelgrass) and Ruppia maritima (widgeon grass), is tolerant
of the highest salinities in the Bay and is found in the lower sections of
the Bay and its tributaries.
    Since 1978 SAV has been the subject of an intensive research program
funded by the U.S. Environmental Protection Agency's Chesapeake Bay Program
(EPA/CBP).  SAV was determined to be a high priority area of research in
this program because of its high primary productivity; its important roles
in the Chesapeake Bay ecosystem — a food source for waterfowl, a habitat
and nursery area for many species of commercially important fish and
invertebrates, a shoreline erosion control mechanism, and a nutrient
buffer.  Most importantly, research was focused on  SAV because of the
dramatic, Bay-wide decline of these species in the  late 1960's and 1970's.
                                  388

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Table 1. SPECIES ASSOCIATIONS OF SAV IN CHESAPEAKE BAY AND ITS
         TRIBUTARIES BASED ON THEIR SALINITY TOLERANCES AS WELL AS THEIR
                                                                                  I
         CO-OCCURRENCE WITH OTHER SPECIES (COMMON NAME OF EACH SPECIES            •
         GIVEN IN PARENTHESIS)                                                    "

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   Group 1	Group 2	Group 3	
Ceratophyllum demersum     Myriopliyllum spicatum           Ruppia maritima
   (coontail)              "(Eurasian watermilfoil)         (widgeon grass)         •
Elodea canadensis          Potamogeton pectinatus          Zostera marina          •
   (common elodea)          (sago pondweed)                 (eelgrass)
Najas guadalupensis        Potamogeton perfoliatus
   (southern naiad)         (redhead grass)•
Vallisneria americana      Ruppia maritima                                         •
   (wildcelery)             (widgeon grass)
                           Vallisneria americana                                   •
                            (wildceleryl•
                           Zannichellia palustris
	  (horned pondweed)	       _

    One of the main elements of the SAV program was to examine the current         •
distribution and abundance of submerged grasses in Chesapeake Bay using
aerial photography to map the vegetation.  In addition, the historical             •
record of aerial photography was examined for recent evidence (less than 40        |
years) of alterations in SAV abundance, and a biostratigraphic analysis of
sediment was performed to detect evidence of longer term (greater than 40          mt
years) alterations in the abundance or species composition SAV beds in             •
several locations within the Bay.  A comparison was made to answer basic
questions on the magnitude of the present decline of SAV as compared with
documented historic declines,  and to determine whether the curent decline          •
was part of a natural cycle or a decline attributed to recent non-cyclic           •
perturbations.
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                                  SECTION 2

                                   METHODS
    The accurate delineation of SAV communities to analyze their
distribution and abundance is difficult, especially when the areas of
interest may incorporate hundreds of miles of shoreline that are subject to
turbid water conditions.  These communities are not static,  but represent
dynamic elements whose distribution and abundance can vary in both space
and time.  Distinct differences in SAV beds can be observed in time frames
of less than two months.  To avoid the problems associated with labor-
intensive field surveys that provide only a limited view of SAV
distribution, remote sensing techniques (aerial photographs) were used to
acquire a synoptic view of the existing beds of SAV.
    In 1978, the entire shoreline of Chesapeake Bay and its tributaries,
from the Susquehanna Flats to the mouth of the Bay, was flown with light
planes equipped with mapping cameras to acquire aerial photographs of all
existing beds of SAV.  Beds of SAV observed on the aerial film were mapped
directly onto U.S.G.S. topographic quadrangles, and the areas of each bed
were determined with an electronic planimeter (see Orth et al. 1979, and
Anderson and Macomber 1980 for detailed information on methodologies used
for this work).  Field surveys of selected sites corroborated information
observed on the aerial photographs and provided species information.
Aerial photography comparable to that obtained in 1978 was acquired in 1980
and 1981 for Virginia's SAV only.
    Data on the past distribution and abundance of SAV in the Bay were
acquired from several sources:  aerial photographs of the Bay's shoreline
and near-shore zone dating back to 1937; reports of field surveys conducted
by state and Federal laboratories, as well as by individual scientists
throughout the Bay area; studies on the biostratigraphical analysis of
estuarine sediments for seeds and pollen of SAV species (Brush et al. 1980,
1981); and anecdotal information supplied by watermen, landowners, and
other interested citizens who had observed changes in the abundance of SAV
in numerous areas of the Bay during the last 40 years.
    We have organized the discussion of SAV distribution into three zones
(Figure 1).  The area between the mouth of the Bay to a line stretching
from the mouth of the Potomac River to just above Smith Island will be
referred to as the lower Bay zone; the area between Smith Island and
Chesapeake Bay Bridge at Kent Island will be referred to as  the middle Bay
zone;  and the area between Chesapeake Bay Bridge and Susquehanna Flats will
be referred to as the upper Bay zone.  These zones have distinct salinity
regimes that influence the type of SAV community that will grow within each
area.   The salinity within each zone roughly coincides with the major
salinity zones of the estuaries:  polyhaline (18-25 ppt), lower zone;
mesohaline (5-18 ppt), middle zone; oligohaline (0.5-5.0 ppt), upper zone.
Despite the fact that the major rivers (James, York, Rappahannock, Potomac,
and Patuxent) as well as the smaller tributaries (for example, Choptank,
Chester, and Piankatank) of the Bay have their own distinct salinity
patterns, the distribution of the grasses in each river will be discussed
within the zone where it connects to the Bay proper.
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                                  SECTION 3

                             PRESENT DISTRIBUTION
    The results of the 1978 SAV aerial survey and mapping of the entire Bay
and its tributaries documented the existence of significant stands of
vegetation (Orth et al. 1979,  Anderson and Macomber 1980).   A total of
16,044 ha (39,629 acres) of bottom was found to be vegetated.  Table 2
presents area values for major sections within each zone.
    In the lower Bay zone (Figure 1) where salinities range from 16-18 ppt
to 25 ppt, two species predominated:  eelgrass (Z. marina)  and widgeon
grass (R. maritima).  Horned pondweed (Z. palustris) was present, but
occurred infrequently.  In 1978,  there were approximately 9400 ha (23,218
acres) of bottom covered with SAV in this zone.  This included 46 ha (114
acres) of SAV that were found in the Chickahominy River, a  fresh to
brackish water tributary of James River.  These areas ranged from very
dense to very sparse in SAV coverage.  The largest and most dense grass
flats were concentrated in several main regions:  (1) along the western
shore of the Bay from just north of the James River to the  Rappahannock
River, especially in the region of Mobjack Bay; (2) behind  protective
sandbars along the Bay's eastern shore; and (3) in the shoal area between
Tangier Island and Smith Island.   The SAV bed between Tangier and Smith
Island was the single, most extensive vegetated area in the entire Bay,
with a total area coverage of 2394 ha (5912 acres) or 26 percent of the
total vegetated bottom in the lower zone and 15 percent of  the total
vegetated bottom in the entire Bay.  1980 data for the upper Bay were not
available.
    Updated aerial photographs taken of the lower Bay in 1980 and 1981
indicate a decrease in abundance  in 1980 followed by slight rebounding in
1981 (Table 3).  The pattern of change determined for one section of the
Mobjack Bay area since 1974 (Figure 2) illustrates a decrease in vegetation
in the outer, generally deeper portions of the beds, a common pattern in
areas where the vegetation has declined.  It is significant to note that in
one intensively sampled site in the York River a general increase in
vegetation abundance was observed from 1978 to 1981.  Examination of this
site revealed that this increase  was a result of a large number of
seedlings, many with seed coats still evident, that were growing only in
the most shallow areas of this location.  Subsequent rapid  growth and
spreading of the seedlings are indicative of the potential  importance of
seeds to the reestablishment of the vegetation (Orth and Moore, in press).
    In the middle zone of the Bay (Figure 1), SAV was found to shift from
Zostera-Ruppia dominated beds to the lower salinity Potamogeton,
Zannichellia, Vallisneria, and Myriophyllum beds.  This zone contained
4,546 ha (11,229 acres) of bottom covered with SAV in 1978.  The greatest
concentration of vegetation (77 percent of 3500 ha) was located in the
Little Choptank River to Eastern  Bay area of the eastern shore (Table 2).
Only five percent or 227 ha (561  acres) of the vegetation occurred between
the Little Choptank River and Smith Island.  An equally small amount [six
percent or 273 ha (674 acres)] occurred along the western shore of the Bay
                                 392

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                                          CO  CO
                                    (7)  0)  0)  (7)
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TABLE 2.  NUMBERS OF HECTARES OF BOTTOM, COVERED WITH SUBMERGED AQUATIC
          VEGETATION IN 1978 FOR DIFFERENT SECTIONS WITHIN THE THREE ZONES
          IN THE CHESAPEAKE BAY   (NUMBERS OF HECTARES ROUNDED OFF TO NEAREST
          WHOLE NUMBER)(DATA FROM ORTH et al. 1979, ANDERSON AND MACOMBER
          1980)
                                                                        Zone
Section                                                      Hectares   Totals

 1. Susquehanna Flats                                         110      Upper
 2. Upper Eastern Shore (Elk, Bohemia, and Sassafras
                         Rivers)                               29
 3. Upper Western Shore (Bush, Gunpowder, Middle, Back
                         and Magothy Rivers, and Baltimore              2098
                         Harbor)                              484      hectares
 4. Chester River                                            1475
 5. Central Western Shore (Severn, South, and West Rivers,
                           and Herring Bay)                   241
 6. Eastern Bay (Wye, East, and Miles Rivers)                 1800
 7. Choptank River (Harris and Broad Creeks, Tred-Avon
                    and Little Choptank Rivers, and
                    Trippe Bay)                               1740     Middle
 8. Patuxent River                                              3
 9. Middle Western Shore (Herring Bay to mouth of Potomac
                          River)                               11       4546
10. Lower Potomac River Section (Nanjemoy Creek to mouth               hectares
                                 of Potomac)                  541
11. Middle Eastern Shore (Honga River to Smith Island and
                          including Fishing Bay, Nanticoke,
                          Wicomico, and Manokin Rivers)       210
12. Tangier Island Complex (includes from Smith Island and
                            Big Annemessex River to
                            Chesconessex Creek)              3759
13. Lower Eastern Shore (Chesconessex Creek to Ell'iots
                         Creek)                              1991      Lower
14. Reedville (includes area from Fleets Bay to Great
               Wicomico River)                                364
15. Rappahannock River (includes Rappahannock and                       9354
                        Piankatank Rivers, and Milford                 hectares
                        Haven)                                 93
16. New Point Comfort Region                                  271
17. Mobjack Bay (includes East, North, Ware, and Severn
                 Rivers)                                     1785
18. York River (Clay Bank to mouth of York)                   157
19. Lower Western Shore (includes Poquoson and Back
                         Rivers)                              925
20. James River (Hampton Roads area only)                       9
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TABLE 3.  NUMBERS OF HECTARES OF BOTTOM,  COVERED WITH SUBMERGED AQUATIC             I
          VEGETATION IN 1971, 1974,  1978, 1980,  AND 1981 FOR DIFFERENT              m
          SECTIONS IN THE LOWER BAY  ZONE   (NUMBERS OF HECTARES  ROUNDED OFF TO
          NEAREST WHOLE NUMBER)(* INDICATES SECTIONS THAT WERE  NOT MAPPED           •
          THAT YEAR) (DATA FROM ORTH AND GORDON 1975,  ORTH  et  al.  1979,
          AND UNPUBLISHED DATA)
                                                          Year
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Section                                     1971   1974    1978    1980    1981

Tangier Island Complex
  (Includes from MD-VA border to                                                   ซ
   Chesconessex Creek)                        *      *    2814    2420    2794        •
Lower Eastern Shore                                                                —
  (Chesconessex Creek to Elliots Creek)        *      *    1991    1370    1691
Reedville                                                                          •
  (Includes area from Windmill Pt.  to                                              •
   Smith Pt.)                                 *       *     364      31     133
Rappahannock River                                                                 •
  (Includes Rappahannock and Piankatank                                             |
   Rivers, and Milford Haven)               1273     68      93       3      43
New Point Comfort Region                     168    233     271     182     207        _
Mobjack Bay                                                                        •
  (Includes East, North, Ware, and  Severn                                          •
   Rivers)                                  1294   1593    1785    1317    1275
York River (Clay Bank to mouth of York)       493    141     157     135     142        •
Lower Western Shore                                                                |
  (Includes Poquoson and Back Rivers)       1620   1069     925    1002     996
James River (Hampton Roads area only)         *       7    	9    	0      0         •
TOTAL FOR LOWER BAY ZONE                                 8,409   6,460    7281        J



from the mouth of the Potomac River to Chesapeake Bay Bridge,  including the         •
South, Severn, Rhode, and West Rivers.  The Patuxent River had  virtually no
vegetation with only three ha (7.4  acres) being observed along  the entire          •
length of the river.  A small amount [12 percent or 545  ha (1346 acres)] of         |
the total vegetation in this zone was found in the Potomac River in the
vicinity of Nanjemoy Creek, Port Tobacco River, Mathias  Point Neck, and            _
Mattox and Machodoc Creeks, at a distance of 50 to 100 km from the river's         •
mouth.  These beds fringe the shoreline  on the lower portions of the creeks         m
and the Potomac River proper, near U.S.  301 bridge, and  are dominated  by P.
perfoliatus and V_._ americana.  This was  the only vegetation found along the         •
entire length of the Potomac River, except for small pockets of SAV that           •
existed at the heads of several small marsh creeks (Carter and Haramis
1980, Carter et al. 1980).  In addition, this is the only area of                  •
comparable vegetation found along any of the Bay's major western                   |
tributaries (James, York, Rappahannock,  Potomac, and Patuxent Rivers).
Less intensive surveys in 1979 showed only slight decreases from the 1978          _
distributional patterns to those in 1979, but considerable declines in 1981         •
were observed throughout the middle zone of the Bay (personal information          *
from unmapped data).
                                    395
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    The upper zone of the Bay (Figure 1)  contained 2098 ha (5182 acres)  of
substrate covered with SAV in 1978 (Table 2),  with the species association
shifting from Group 2 to Group 1 (Table 1) .   Susquehanna Flats had 110 ha
(272 acres) of vegetation in 1978, most of which occurred in scattered
beds.  This was a very small area when compared to abundance of SAV in the
late 1960s and early 1970s.  Only two species  were present on the Flats  in
1978, Eurasian watermilfoil (M. spicatum) and  wildcelery (V. americana);
eleven species were found by researchers  in  1971 (Bayley et al. 1978).
Approximately 23 percent of the total bottom area covered with SAV in this
zone was in the Gunpowder, Middle, Bush,  and Magothy Rivers located along
the western shore, whereas almost no vegetation was present in the Elk,
Bohemia, and Sassafras Rivers on the eastern shore.  About 70 percent [1469
ha (3628 acres)] of the total bottom area covered with vegetation was
present in the Chester River and Eastern Neck area.  The Chester River area
contained a diverse assemblage of SAV, with  seven species recorded during
the 1978 survey.  Less intensive surveys  in  1979 show little change in
distribution patterns from 1978, but surveys in 1981 indicate considerable
declines in this zone.
    In summary, the survey of SAV in the  Bay in 1978 indicated the presence
of many apparently healthy beds in various  sections of the Bay.  There
were, however, large sections devoid of almost all vegetation where, in
earlier years (1965-1970), luxuriant beds persisted (see Figure 5).
Tributaries with major reductions of SAV  included portions of the York,
Rappahannock, Potomac, Patuxent, Choptank,  Chester, and Piankatank Rivers.
SAV populations in other areas along the  main stem of the Bay, including
Susquehanna Flats, the area between Smith Point on the Potomac River, and
Windmill Point on the Rappahannock River, and an area between Smith Island
and Eastern Bay, which includes many smaller rivers, have also significantly
declined.  More recent evidence from ground  truth surveys and aerial
photographs taken from 1978 to 1981 indicate that this decline has
continued in certain areas.  This suggests  a widespread but complex pattern
of recent major decline, involving the entire spectrum of SAV communities
found in the Bay, from the mouth of the Bay  to Susquehanna Flats at the
head of the Bay.
                                  396

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                                  SECTION 4

                              PAST DISTRIBUTION
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    A detailed discussion of past trends of SAV distribution and abundance          _
is hindered by the lack of adequate data for many sites over a long period          •
of time.  A review of the available historical information indicates that           ™
SAV has generally, in the past, been very abundant throughout the Bay.  In
the last 50 years, however, there have been several distinct periods where          I
SAV, in some large portions of the Bay, has undergone major fluctuations,           |
although SAV populations have been known to undergo erratic oscillations
within small areas (Stevenson and Confer 1978).                                     m


HISTORICAL TRENDS (1700-1930)

    The pattern of SAV distribution and abundance in the Bay during this            •
period was determined primarily from indirect evidence, pollen and seed
analysis, and qualitative observations.  Aerial photography can usually             •
provide good evidence for the presence of SAV, but was not generally                |
available until the late 1930s.  If it can be assumed that less
urbanization during this period resulted in better water quality throughout         _
the Bay and its tributaries (Heinle et al. 1980), conditions may have been          •
more favorable for the growth of SAV.                                               ™
    Biostratigraphical analysis of sediments for SAV seeds and pollen from
Furnace Bay (Brush et al. 1980), a small embayment off Susquehanna Flats,           I
indicates the continuous presence of SAV seeds from the 17th century.               I
However, there appear to have been some changes in species of SAV (for
example, declines of Najas spp.) corresponding to changes in land use, such         •
as deforestation.  Increased erosion and sedimentation from these practices         I
possibly resulted in more turbid water conditions and, thus, the eventual
decline of species less adapted to low light levels.
    The Potomac River, the largest tidal tributary in the Bay, historically         •
contained numerous species of SAV that were very abundant.  Several species         ™
(wild celery, coontail, naiad, and elodea) were reported in the vicinity of
Washington, D.C. in one of the earliest accounts (Seaman 1875).  Gumming et         •
al. (1916) provided a map of the Potomac River below Washington, DC that            |
showed the river having a narrow channel and wide shallow margins that he
reported to be extensively vegetated with curly pondweed (P_. crispus),              •
wildcelery (V. americana), and coontail (C. demersum).  Many other pondweed         I
species were reported at mouths of tributaries below Washington, D.C.
(Hitchcock and Standley 1919), indicating the widespread presence of SAV
species in the tidal portion of the Potomac River.                                  •
    Eelgrass (Z. marina) apparently underwent some decline in Chesapeake            ™
Bay area in the~~late 19th century, although the magnitude of the decline
was never quantified.  Cottam (1934, 1935) states that a guide from the             •
Honga River Gunning Club reported on the decline of eelgrass in Dorchester          |
County, Maryland in 1893-1894.  Cottam also reports an interview with a
member of the Maryland Game Commission who commented on the decline of              _
eelgrass in Chesapeake Bay in 1889 (at the time of the Johnstown Flood) and         •
stated that it was 25 years before eelgrass fully recovered.  Cottam
                                 397
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documents other declines of eelgrass along the east coast of the U.S. —
one as early as 1854.  From these accounts, it appears that eelgrass has
undergone several fluctuations during this period (1700-1930),  suggesting
some irregular, though undefined, perturbations on the system.
    In summary, evidence suggests that in the Bay:  (1) SAV was apparently
much more widespread from 1700 to 1930 than it is today; (2) SAV had been a
persistent feature of shallow water habitats, although there may have been
some localized shifts in species composition of the beds; and (3) abundance
of eelgrass has apparently undergone changes several times.


RECENT PAST (1930-1980)

    With an increased awareness of the value of SAV as a food source for
waterfowl wintering in the Bay and observations of major fluctuations in
the Bay and elsewhere, researchers placed more focus on the distribution
and abundance of SAV during this period.  This research led to the
availability of more quantitative information; as a result, a much greater
perspective can be obtained.  During these last 50 years, there have been
two distinct events in which significant changes occurred within individual
species of SAV:  (1) the eelgrass wasting disease in the 1930's; and (2)
the watermilfoil (M. spicaturn) problem in the late 1950's and early
1960's.  Even far more dramatic are the changes in SAV populations in the
Bay in the 1960's and 1970's, when, unlike the eelgrass and milfoil events,
all species in almost all areas of the Bay were affected to some degree.
The following three sections discuss each of these periods.

The Eelgrass Wasting Disease (1931-1932)

    The most documented decline of a species in the Bay was that of
eelgrass in the early 1930's.  This decline was recorded not only in the
Bay area, but also along the entire east coast of the U.S. and the west
coast of Europe (Cottam 1934, 1935; den Hartog 1970; Rasmussen 1977).
Cottam (1934) comments, based on information from his surveys of historical
records and personal inquiries of fishermen, watermen, and scientists,  that
"in the memory of man there has been no period of scarcity at all
comparable to the present one (1931-1932 compared to other past periods)."
The extent of the decline in Chesapeake Bay was never quantified, but
aerial photographs taken in 1937, five to six years after the height of the
decline, are available for almost all of the shoreline in the lower Bay.  A
review of many areas in the lower Bay and subsequent mapping of six sites
(Orth et al. 1979) shows areas of bottom in shallow water covered with
large amounts of submerged vegetation (it was assumed to be eelgrass based
on knowledge of present day patterns and anecdotal information from
long-time residents of these areas).  All six areas showed subsequent
increases in later years up to 1972.  Although quantitative information is
lacking prior to the wasting disease, we assume that the vegetation present
in 1937 represented partial recovery from the height of the decline in
1931-1932.  Cottam (1935) confirmed our conclusions from aerial photographs
when he reported that Chesapeake Bay eelgrass was showing "an encouraging
change, with a few localized areas fast approaching the normal."
                                  398

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                                                                                   I
    One indication of the magnitude and severity of the decline of
eelgrass, experienced not only in Chesapeake Bay but also along the east           ซ
coast of the U.S. and the west coast of Europe, was found in the coastal           m
lagoons on Virginia's seaside.  These areas contained dense beds of
eelgrass that supported a large bay scallop industry.  The post-veliger
larvae of the scallop require eelgrass as a setting substrate (Gutsell             I
1930).  Without eelgrass, there can be no scallops because a scallop lives,         I
at the longest, two years, and a change or disappearance of eelgrass
results in rapid shifts of the scallop population.  Indeed, this is what           •
happened (Table 4).  The commercial fishery that resulted in a harvest of          I
over 14,000 kg per year in the late 1920s and early 1930s completely
declined in 1933, over a span of just two years.  Eelgrass has never               _
recovered in the seaside bays as compared with Chesapeake Bay and many             •
other areas where it had substantially declined (Cottam and Munro 1954),           ™
nor has the scallop industry ever returned.

TABLE 4.  CHANGES IN AMOUNT OF SCALLOPS (SHUCKED MEAT) HARVESTED FROM THE          |
          DELMARVA PENINSULA FROM 1928-1975 (COLLATED FROM U.S. FISHERIES
          DIGEST)                                                                  _


Year                           Harvested scallops (kg shucked meat)
1928
1929
1930
1931
1932
1933
1934
5,050
16,038
25,549
17,170
9,220
0
0
1981
                                                                                   I

                                                                                   I

                                                                                   I

                                                                                   I
The Milfoil Problem (1959-1965)

    A second major period of extensive SAV fluctuation in the Bay was the
large increase in Eurasian watermilfoil (M.  spicatum) in the late 1950's           I
and early 1960's (Stennis 1970, Bayley et al.  1978,  Stevenson and Confer           •
1978b).  The area affected by the milfoil was  restricted to the upper Bay
area and a large section of the Potomac River  (Figure 3).  The intolerance         •
of milfoil to high salinity water limited its  downward expansion in the            |
Bay, but reasons for its sudden expansion in abundance during this period
are not well understood.  Until 1955,  milfoil  was found only sporadically          M
in the Bay, apparently introduced from Europe  to the U.S. between 1880 and         •
1900 (Rawls 1978).  Biostratigraphic evidence  substantiated its recent
arrival to Chesapeake Bay (Brush et al. 1980).  Milfoil seeds were found in
sections of sediment cores from Furnace Bay  near Susquehanna Flats and             I
dated only to approximately 1935, though sediments from the cores had              •
recorded events, including the presence of other SAV species, to 1770.
                                 399
                                                                                   I

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    Milfoil increased Bay-wide from 20,200 ha (49,894 acres) in 1960 to
40,500 ha (100,035 acres) in 1961 (Rawls 1978).  In contrast, the 1978
baywide SAV survey found that only 16,000 ha (39,525 acres) of bottom were         •
covered by all SAV species combined.  In creeks along the Potomac River,           •
the milfoil reached densities so high that it was considered a nuisance,
and attempts to eradicate it with applications of 2-4 D were initiated             •
(Rawls 1978).                                                                -      |
    The Susquehanna Flats area typifies the changes noted during the rapid
expansion of milfoil.  In 1957,  a survey conducted of SAV found that               _
milfoil did not occur at any sampling stations.  Subsequently, it was found        I
in one percent of these stations in 1958, 47 percent in 1959, 82 percent in        ™
1960, and 89 percent in 1961 and 1962.  After 1962, milfoil declined in the
Flats, with slight increases in 1966 and 1967.  The most serious effect            •
associated with the rapid increase in milfoil was a decline in other native        |
species such as common elodea (E. canadensis), naiad (N. guadalupensis),
and wildcelery (V^ americana).  The decline of native species is shown in          ซ
Figure 4.  For example, this graph shows that in 1963 abundance of native          I
plant material was below 50, while abundance of watermilfoil was over 200.
Bayley et al. (1978) suggest that the decline of native species was due to
competitive exclusion by milfoil.  As milfoil declined, these native               •
species returned, but were found at a lower density and covered less area          •
than prior to the milfoil expansion (Bayley et al. 1978).

The Bay-wide Problem (1960-1980)                                                   |

    In the 1960's and 1970's a number of field surveys and aerial surveys          _
were conducted to estimate the distribution and abundance of SAV in the            m
Bay.  These estimates, when considered with the results of the SAV                 "
distribution projects funded by the Bay Program, reveal dramatic results.
The combined data show a pattern of vegetation decline that includes all           •
species in all sections of the Bay and a present abundance of vegetation           |
that may be at its lowest level in recorded history.
    The results of this recent decline were first evident in changes in            m
diving duck populations in the Bay (Perry et al. 1981).  Two species, in           •
particular, the canvasback (Aythya valisineria) and the redhead (Aythya
americana), have shown significant population declines in the last 10 years
in the Bay despite increases in the overall North American and Atlantic            •
flyway populations.  These two duck species have traditionally used SAV as         "
food (Stewart 1962).  The decline in their preferred food source presumably
led to the decline in the total number of ducks found in the Bay.  Since           •
the SAV decline, canvasbacks have altered their feeding habits to include          ||
clams, and redheads still feed predominantly on vegetation.
    To illustrate the major changes of SAV populations that have occurred          ซ
in the Bay area in the last 20 years, we have delineated SAV distribution          I
on a Bay-wide basis at five-year intervals beginning in 1965 and                   m
subsequently in 1970, 1975, and 1980 (Figures 5, 6, 7, and 12).  1965 was
chosen as a starting point because of the lack of complete information for         I
Bay-wide determination prior to 1965; the compounding problem of the               •
explosion in the late 1950's of Eurasian watermilfoil, which declined by
1965; and the relatively abundant Bay-wide distribution of SAV during this         •
time, apparent from archival photographs and anecdotal information.  Though        •
the scale of the map is small in relation to the generally small size of
                                 401
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    300 H
      TOTAL  NO. OF ALL SPECIES
      EURASIAN WATERMILFOIL
                    (abundance)
      DOMINANT NATIVE  AQUATICS
                        (abundance)
          -Vallisneria amer/cana
          -Najas spp
         -Elodea canadensis
    2504
<
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    200 H
o
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                                                                   .- 16
                                                                   h!4
                                                                   h!2
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    50 H
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                                U R  <
                                                                   h 4
                                                                   h 2
       58 ' 59 ' 60' 61 '62' 63 ' 64 ' 65 ' 66 '67 '68 '69 '70 ' 71 ' 72'73'74'75
                                   YEARS
Figure 4.   Population  fluctuations  of  watermilfoil  compared to  the
            dominant native species  and total number of species  found
            on the  Susquehanna Flats from 1958-1975  (figure adapted
            from Bayley et al. 1978).
                                   402

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                                                                                  I
most SAV areas, the changes that occurred in SAV distribution in each of
the five-year intervals were sufficiently dramatic so as to appear quite          m
distinct in the respective figures.  Note, for example, the large changes         •
in abundance of SAV in Susquehanna Flats area, Patuxent, and Potomac Rivers
from 1965 to 1975.  We are aware that the small scale is not suitable for
small populations of SAV related to the size of the entire Bay, but the           flj
overall changes in SAV on a Bay-wide basis are more easily perceived on           I
this size map.  Though in some respects the following maps are qualitative,
they represent the culmination of a large effort to incorporate whatever          m
quantitative data were available with the most reliable qualitative data.         •
These maps are the first effort to place into perspective the complex
changes that have been observed in SAV populations over the last 20 years.

1965--                                                                            •
    In 1965, SAV was quite abundant throughout the Bay and in all of the
major tributaries (Figure 5) despite the compounding effects of the milfoil       •
problem in the early 1960's (Bayley et al. 1978).  One area, however, that        |
had been reported to have abundant SAV (Gumming et al. 1916), but no longer
contained any, was the freshwater tidal portion of the Potomac River              •
(Carter and Haramis 1980, Carter et al. 1980).  The SAV of this area              •
apparently declined in the 1930s and had all but disappeared by 1939
(Martin and Uhler 1939).  The lower reaches of the Potomac still contained
abundant stands of vegetation in 1965 based on evidence from aerial               •
photographs of the Coan, Yeocomico, and lower Machodoc Rivers and from            •
personal accounts of local watermen.  In addition, an intensive benthic
survey for the soft shell clam, Mya arenaria, in the lower Potomac in 1961        •
revealed abundant stands of SAV.  The lower reaches contained eelgrass,           •
while numerous brackish water species abounded farther upstream
(Pfitzenmeyer and Drobeck 1963).                                                  _

1965-1970—                                                                       •
    By 1970 there were still substantial stands of SAV throughout the Bay
but evidence indicates some major losses had occurred in several areas            I
(Figure 6).  Vegetation in the entire Patuxent River had all but completely       I
disappeared (R. Anderson, personal communication) by 1970, with declines
being first noted in the mid-1960's.  Anecdotal accounts indicate that            •
populations of eelgrass adjacent to Chesapeake Biological Laboratory at the       I
mouth of the Patuxent River were severely depressed in the late 1960's and
gone by 1970.  The vegetation in the lower Potomac River evidenced in
aerial photographs of the 1960's was also almost completely absent.  In           •
addition, vegetation in many of the eastern shore upriver sections of the         •
Choptank, Chester, Gunpowder, and Bush Rivers, as well as in the entire
Nanticoke and Wicomico Rivers in the middle and upper Bay zones, was absent       •
or in very reduced abundance (Boynton, personal communication).                   B
    SAV in some localized areas around the Bay, including Susquehanna Flats
(Bayley et al. 1978) and the Chester River area (Anderson and Macomber            im
1980), had increased in coverage from 1965 to 1970, though not to previous        •
levels.  The increase in these years may have been the result of the
reemergence of native SAV species in response to the decline of milfoil
(Bayley et al. 1978).                                                              •
    One of the first significant surveys of the upper Bay during this              •
period was that conducted by Stotts from 1967 to 1969 (Stotts 1970).  Over
                                  403
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Figure 5 • Distribution of SAV in Chesapeake Bay - 1965.
                           404

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Fieure fi.  Distribution of SAV in the  Chesapeake Bay - 1970,
                           405
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1,000 transects were sampled from the Virginia - Maryland border to
Susquehanna Flats.  The survey findings indicate that many areas contained
significant beds of vegetation, especially in the more southern locations,
from the Choptank River to Smith Island.  Stotts reported, however, that
large declines of SAV occurred in July and August in several locations
north of the Choptank and that SAV did not appear as robust as in the more
southern areas, indicating that these systems were being stressed by
environmental factors.  Examination of aerial photographs taken in
September, 1970, shows large beds of vegetation in the same areas where SAV
was reported to be abundant by Stotts1 survey, especially in the lower
reaches of the Chester River, Eastern Bay, Little Choptank River, Honga
River, and Bloodsworth Island.
    In contrast to the declines evidenced during this period in the
upstream, low salinity regions of the Bay and its tributaries, the higher
salinity regions vegetated with eelgrass and widgeon grass showed as yet
little evidence of any deterioration.  Aerial photographs document that
extremely dense beds characterized much of the shoreline of the lower Bay
and its tributaries, and many areas showed a continued increase in coverage
since the 1930's (Orth and Gordon 1975, Orth 1976, Orth et al. 1979).

1970-1975—
    By 1975 the Bay-wide situation for SAV had changed dramatically along
the entire length of the Bay proper (Figure 7).  Indeed, the abundance of
vegetation in 1975 represented what we feel was, until then, the lowest
recorded abundance of vegetation in Chesapeake Bay and its tributaries as
far back as records indicate.  The decline of SAV that first began in the
mid-1960s and continued to the early 1970's, was now observed in all
sections of the Bay, with some areas affected more than others.  This
decline also appeared to accelerate after Tropical Storm Agnes influenced
the Bay in June 1972.
    Much of the information available for this period for the upper and
middle Bay zones is from the 644 station survey of SAV conducted once a
year in Maryland waters beginning in 1971 by the Maryland Department of
Natural Resources and the U.S. Fish and Wildlife Service (Kerwin et al.
1977; unpublished files).  Their data showed that SAV declined in the
surveyed areas between 1971, when 28.5 percent of the stations were
vegetated, and 1973, when 10.5 percent of the stations were vegetated
(Table 5, Figure 8).  SAV fluctuated at comparatively low levels from 1974
to 1975, decreasing to 8.7 percent in 1975.  The number of major areas with
no SAV increased from five in 1971 to 11 in 1975, an increase of 100
percent (Figure 1 and Table 5).  This survey also shows that individual
sections of the Bay had not exhibited a uniform trend, but that the head of
the Bay and lower eastern shore have fared the worst, while the middle
sections of the Maryland eastern and western shores fared the best.
    Large reductions in vegetation were observed immediately after Agnes,
in July and August, 1972, in many sections of the upper Bay zone (Figure
7), principally the Elk, Bohemia, Sassafras, Back, Middle, Magothy, and
Chester Rivers, Howell and Swan Point, Susquehanna Flats, and the
headwaters of the Bush and Gunpowder Rivers (Figure 7 and Table 5) (Kerwin
et a!4 1977).  In addition, sections of the middle Bay zone, primarily
those in the northern end, such as the Severn River, appeared to be rapidly
denuded of grasses.  The species that were most affected were the fresh and
                                 406

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Figure 7.   Distribution of SAV in the Chesapeake Bay - 1975.
                              407
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brackish water species:  coontail (C. demersum),  common elodea (E.
canadensis), southern naiad (N. guadalupensis), wildcelery (V. americana),
sago pondweed (P. pectinatus), and redhead grass  (P. perfoliatus) (Table 1),
    Vegetation in the middle and lower zones of the Bay started to decline
in 1973.  In the middle zone, regions affected were:  the Choptank and
Little Choptank Rivers, James Island, Manokin River, Big and Little
Annemessex Rivers, and Bloodsworth and Smith Islands.   Species affected in
these areas included many of the same low salinity species that were
rapidly lost from the upper Bay section in 1972 as well as the higher
saline species, eelgrass and widgeon grass.  The  decline of SAV at some
locations on the lower eastern shore where eelgrass and widgeon grass had
predominated is shown in Figure 9.
    In the lower zone, where data are available primarily from detailed
aerial photographs (Orth and Gordon 1975, Orth et al.  1979), vegetation in
the York, Rappahannock, and Piankatank Rivers, as well as in many small
tributaries, was reduced substantially during this period (Figure 7).  To
highlight the changes that occurred with SAV communities in the lower Bay,
six areas were mapped for historical changes in the distribution and
abundance of SAV (Orth et al. 1979).  These changes are shown in detail for
one of the sites:  Mumfort Island in the York River (Figure 10).  SAV
coverage in the lower Bay generally increased at  all these sites from the
1930s to 1970; there was a marked decline beginning around 1970 (Figures 10
and 11).  Our data, especially for the York River, indicated that the
decline of SAV occurred in the summer of 1973, as evidenced by the presence
of large beds of SAV in April 1973 that were absent in April 1974.
Comparison of means indicated that there were significant differences
between pre-1972 and post-1972 coverages at Parrott Island in the
Rappahannock River (p=0.001), Mumfort Island in the York River (p=0.002),
and East River in Mobjack Bay (p=0.038).  At Jenkins Neck at the mouth of
the York River, where the trend was more gradual, regression analysis
indicates a significant decline (p=0.02).  At Fleets Bay, just above the
mouth of the Rappahannock River, regression analysis indicates the decline
was significant (p=0.019).  Only Vaucluse Shores  on the eastern shore
showed no significant decline (p-0.14).
    Several distinct patterns in the decline of vegetation in the lower Bay
are evidenced.  First, it appears that losses of  vegetation were greatest
in all the areas where eelgrass formerly reached  its upriver or upbay
limits.  For example, eelgrass beds disappeared from the Maryland portion
of the eastern shore while remaining in the Virginia portion.  Along the
western shore of the lower Bay, SAV beds declined the most in the northern
areas and least in the southern areas.  Within the major tributaries, SAV
disappeared, leaving only some beds at the mouths of the rivers.  In nearly
all the small creeks and tributaries where eelgrass beds continued to exist
in 1975, the former distribution included areas further upstream.  Second,
in addition to the upstream-downstream movement,  it appears that the
vegetation declined in the deeper, offshore sections of the beds rather
than in the shallower, nearshore areas (Figure 2).
                                410

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                                                                                   1
1975-1980—
    Between 1975 and 1980, the Bay-wide status of SAV appeared to be one of        |
continuing decline in almost all areas of the Bay (Figure 11).  The upper          |
Bay survey by the Maryland Department of Natural Resources continued to
show a small percentage of stations vegetated with SAV with a trend toward         g
decreasing levels to 1979 (unpublished data).  A small increase was                I
observed in 1980, but this was due to a large increase in vegetated
stations at the Smith Island site (Table 5 and Figure 9).  All sites, where
a decline in abundance in the early 1970's from the lower eastern shore was        I
observed, except for Smith Island, continued to decline to much lower              I
levels (Figure 9).  Another significant point was the continual increase in
the number of areas that contained no SAV.  By 1980,  16 areas, or 62               I
percent of the total areas identified for this survey now contained no SAV,        J
compared with five areas or 19 percent in 1971 (Table 5 and Figure 8).
    In the lower Bay zone, the total for the mapped areas of the western
shore from the Rappahannock River to the James River between 1974 and 1978         I
remained similar (Table 3).  Although there were observed declines, losses         '
were offset by increases in the sizes of some grassbeds, especially those
in Mobjack Bay.  Losses were observed in many of the smaller beds that             t
remained in some localities after the 1973-1974 period, but had totally            ]
disappeared by 1978, particularly in Fleets Bay, where 76 percent of the
vegetation mapped in 1974 declined by 1978.  Between 1978 and 1980, almost         t
all sections of the lower Bay declined.  Now, in some sections                     1
(Rappahannock River and Reedville), almost no SAV remains (Table 3, and
Figures 11 and 12).
                                  415
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