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                                                                     903R85003

                                                            841 Chestnut
                                                            Philadelphia,




ro

225
 C54
 984-5
                                                     1984
                                                     1985

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CONTENTS
Executive Summary                 1

The Water Quality Base              3

Sediment & Toxics                  8

Centerfold Map                     12

Plankton & the Food Chain          14

Citizen Monitoring                  17

SAV: Habitat & Nursery             18

The Harvest: Finfish                20

The Harvest: Shellfish              22

Case Study: The Patuxent          24



ACKNOWLEDGEMENTS	

Executive Editor/Designer: B.G. Bandler
Designer/Production Coordinator/Illustrator:
Karen L Teramura
Editorial Assistants:  Elizabeth C. Krome,
Catherine L. Leger.
Production Assistant: Karen L. McDonald
Illustration Assistant: Steven L. Coon.
Photos Skip Brown
CBP Monitoring Subcommittee Representative:
Bert Brun.
EPA Monitoring Coordinator 1984-1985:
Kent Mountford.
Chairman, CBP Monitoring Subcommittee:
William M. Eichbaum.



SYMBOLS	

cfs      cubic feet per second
DO     dissolved oxygen
mgd     million gallons per day
mg/l     milligrams per liter (=ppm)
N       nitrogen
P       phosphorus
PAHs   polynuclear aromatic
         hydrocarbons
PCBs   polychlorinated biphenyls
ppb      parts per billion
ppm      parts per million
ppt      parts per thousand
SAV     submerged aquatic vegetation
STP     sewage treatment plant
TN      total nitrogen
TP      total phosphorus
TSS      total suspended solids
 u.g/1      micrograms per  liter (=ppb)
 u.m      micrometer (=micron)
 >        more than
 <        less than
          Monitoring is a key element in restoring the Chesapeake Bay. Monitoring
          keeps managers, researchers, and citizens current on the health of the
     Bay, and measures the progress of control strategies.  Under the Chesapeake
     Bay Agreement of 1983, the implementation Committee established a Monitoring
     Subcommittee to develop and Implement a Bay-wide coordinated monitoring
     program. The EPA/state cooperative program began in May, 1884 and afull
     sampling network was in place on the mainstem Chesapeake by July.

        The Chesapeake Bay Monitoring Network is a complex arrangement involving
     the federal government, three states (Virginia, Maryland, and Pennsylvania) plus
     the District of Columbia, three universities, seven private research institutions,
     and more than 125 individuals. The network is comprised of 167 stations that
     cover not only the mainstem Bay, but key portions of its 150 tributaries.
     Nineteen physical, chemical, and biological parameters are being monitored 20
     times a year.

        Monitoring data can provide a sound scientific basis for making important
     Bay program decisions. Monitoring data can serve environmental managers in a
     wide variety of Bay restoration programs-living resources, soil and land
     conservation, wastewater treatment, computer modeling-and in the legislative
     process.
GLOSSARY
Algae


Bacteria

Baseline


Benthos


Biomass
Estuary


Fall line
           Simplest of all aquatic plants.
           Most important Bay algae are the
           microscopic phytoplankton.
           Single-celled micro- organisms
           that usually lack chlorophyll.
           In reference to data, the initial
           measurements against which
           later data are compared.
           Plant and animal life whose
           habitat is the bottom of a sea,
           lake, or river.
           Quantity (weight) of living matter
           Highly productive bay and river
           ecosystems where fresh water
           meets salt water.
Nonpoint
Nutrient
pH
           Zone where a major river changes
           from free-flowing (inland
           freshwater) to tidally affected
           (coastal).
Food chain Feeding sequence from plankton
           through higher predator
           organisms
Inorganic  Combinations of elements (such
           as metals) that do not include
           organic carbon; generally non-
           volatile, not combustible, and not
           biodegradable.
Monitoring Observing, tracking, or
           measuring for a special purpose.
Nitrogen   Essential nutrient; several forms
           organic and inorganic (ammonia,
           nitrate, nitrite); also atmospheric
           gas. Expressed in mg/l
           Applied to pollution source'
           diffuse rather than point (pipe)
           discharge, i.e. farm runoff
           Primary element necessary for
           the growth of living organisms,
           generally applied to nitrogen and
           phosphorus, but also carbon and
           silicon. Excessive nutrient loads
           result in eutrophication.
           Measure of acidity or alkalinity
           On a 0-14 scale, 7.0 denotes
           neutrality, less than 7 acidity and
           over 7 alkalinity.
Phosphorus Essential nutrient that occurs in
           various forms: inorganic
           (orthophosphate, pyrophosphate,
           tripoly- phosphate), and organic
           Minute plants and animals that
           passively float or weakly swim in
           water.
           The total amount of dissolved
           salts per 1,000 units of water
           (PPt).
           Newly attached juvenile oysters
           Reproductive process in fish and
           other aquatic animals.
           Tidal river River under tidal
           influence with a low saline and
           upper freshwater reach.
                                                            MARCH 1987
                                            Plankton
                                            Salinity
                                            Spat
                                            Spawning

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                                                                                         903R85003
     This second report from the Chesapeake Bay Program Monitoring Subcommittee
     summarizes data collected at over 165 stations Bay-wide for the new coordinated
monitoring program from June 1984 through September 1985. This initial effort
represents  the groundwork of a large, complex, and rapidly growing store of
information.

   The challenge of the monitoring process should not be over simplified. Because
the Bay is so large and complex, it will take an estimated three to five years to sift out
the natural variability within a given year and between years in order to achieve a base-
line characterization of the Bay, and to understand the slow and subtle changes
resulting from management actions. Time and a consistent sampling program are
essential to meet monitoring objectives.  The major objectives are to determine long-
term trends and the driving forces behind them, and to establish the link between water
quality and the health of the Bay's living resources. The monitoring program should
help to distinguish the effects on the Bay from natural events (like flows and salinities)
from man-induced pollutants (such as excessive nutrients). Management actions will
become increasingly focused as a result of this knowledge.  The new program's
comprehensive, in-depth information on Bay processes is already being  used to design
two water-quality models for the purpose of projecting how restoration programs can
achieve improvements in the Bay.

   The first  part of this report focuses on the physical-chemical characteristics of the
Bay: flows, salinity, dissolved oxygen, chlorophyll a, and nutrients (the  water-quality
base) plus sediments and toxics.  The centerfold offers a broad capsulated picture of the
monitoring network and  the 1984-1985 Chesapeake.  The second half of the
publication covers the Chesapeake's living resources, from plankton, the important
first  link in the food chain, through submerged aquatic vegetation  (SAV), and the Bay's
finfish and shellfish harvests. The 1984-1985  data summary concludes  with the early
results of the citizen monitoring program and a look at the Patuxent River.
Background  boxes to help define and put the summary observations in context have
been provided in each section. We suggest you read the boxes before the main text.
Please note that in addition to this 28-page summary report, a more detailed
compendium, composed  of 19 chapters that focus on different aspects of the
monitoring program, is available.

   The 1984-1985 monitoring period comprised two very different years, and the Bay
responded accordingly.  Generally, 1984 was a wet year and 1985 a dry year.
Streamflow in 1984 was  23% above average, while in 1985 it was substantially below
average for the better part of the year. In November 1985, however, dry conditions
were punctuated by tropical  storm Juan.  Juan's effects were confined, for the most
part, to the lower Bay and had less impact than did "Agnes"  in 1972.  Flooding and
sediment loadings  were extensive in Virginia's major tributaries.  The data indicate that
there is some good news to report for SAV, waterfowl, and striped bass. SAV is one
of the bellwethers that led to the conclusion that the Bay was in decline. A 26%
increase in total SAV acreage from 1984 to 1985 is cause for optimism. This is a
hopeful sign  for living resources, including the many Bay waterfowl that use SAV as
U.S. lid-, oii.nsntal Protection Agency
Region 111 Information Resource
Center (3PM52)
841 Chestnut Street
Philadelphia, PA   19107

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food and habitat.  Many waterfowl species remain in trouble, but the populations of a
few species (mallard, bufflehead, and the Canada goose) have increased, presumably
due to their finding food sources other than SAV. The Maryland striped bass ban and
stringent harvest restrictions in Virginia, the Potomac River, and most coastal Atlantic
states appear to be protecting the relatively strong 1982 "rockfish" year-class. When
members of this year-class are adults  and spawn (in 1988), it is hoped they will have
better water quality and that healthier year-classes will result.  Generally, during 1984
and 1985 shellfish were still under stress.  While higher oyster spatfalls were observed
in 1985, survival rates remained low.  Harvests of the pugnacious blue-crab were gooc
in both years.  While mainstem benthic animals suffer as  the number of areas with
low summer oxygen levels increases,  it is  possible that wastewater treatment
improvements are helping some tributary clams to have more stable populations.

   The monitoring results underscore the uniqueness of patterns within each Bay sub-
basin, and the importance of Bay-wide inter-relationships. Higher streamflows in 198<
brought large pulses of nutrients, which triggered heavy plankton growth, particularly
in the upper tidal-fresh reaches of the Potomac and Patuxent rivers.  Dry 1985 broughi
higher salinities and, therefore, less clearly defined surface-to-bottom salinity
differences and some improvement in deep-water oxygen conditions. High salinity,
while conducive to better oyster spat production, encourages intrusion up-Bay of oyste
diseases, MSX and Dermo, and the predatory oyster drill. Higher than  usual plankton
concentrations were noted during the  monitoring period.  High productivity appears to
result in high levels of unconsumed plankton,  which die and settle in deep water wher
decomposition processes deplete oxygen.  Both summers had periods of low oxygen
and anoxia, but the severity and duration of these periods were substantially greater in
1984 than in  1985. Surveys in 1984 found oxygen-poor  waters extending further into
Virginia's Chesapeake than had been  previously documented.  Monitoring in both
summers revealed that hypoxia and deep-water dissolved oxygen (DO) concentrations
are more dynamic than previously expected, a finding that makes trend analysis of DC
very difficult. Toxicants data contribute to our understanding of what toxic substance;
are where, and the relationship among toxicants, fine-grained sediments, and the
benthic community.  While there have been overall increases in toxics levels since
1979, there is less DDT.  Future reports will benefit from a developing toxics strategy
and ongoing work to monitor organics and metals.

   Has progress been made?  While  it is  still  too early to document that our control
programs are saving the Bay, it can be said that the 1984-1985 observations are
valuable and represent a solid start toward establishing a base-line characterization.
The first Bay-wide monitoring network, including nearly every tributary, is in place
and is designed to link water-quality  monitoring with important habitat and living
resource monitoring.  Communication and coordination now exist and have improved
within and among agencies at all levels. So, while the Bay's problems  are still with
us, there is cause for modest optimism. Most important, there is a commitment to
the Bay-wide goal of restoring the Chesapeake.

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                   The  Water  Quality  Base
    quality because they influence
           "" "
crtherpollutants tothe Bay. River
lighter (fresher) water flowing on top of
the h0avfcr$M$MQ wWer. fhtse
difference in salinity, or a stratification
increased:vertical mixing, which
and can i
of«teteS
'Pt0wa*e>$'ate^rAeii^r% Eastern
shore are saltier than western shore
waters because of both the greater
increases in freshwater flows.
organisms for their basic metabolic
processes. It enters the water from
organisms are stressed. Severe
      ''  '  ""   '
                   ); anoxia
                                      Flows of the major tributaries into
                                    the Bay have been monitored for many
                                    years by the U.S. Geological Survey.  As
                                    an indication of the freshwater flow
                                    conditions during the first 15 months of
                                    the water quality monitoring program, the
                                    1984-1985 flows can be compared to the
                                    long-term average flow for the
                                    Susquehanna River, which contributes
                                    50% of the fresh water entering  the
                                    Chesapeake Bay.
                                      Over the past 18 years, the average
                                    flow of the Susquehanna River at
                                    Conowingo Dam has been 41,950 cfs.
                                    The average flows of the Susquehanna in
                                    1984 were 19% above normal; in 1985
                                    they were 27% below normal. There
                                    were major seasonal differences between
                                    these two years: the 1984 summer flows
                                    were much higher than those in  1985.
                                    The monthly average flows for the six
                                    largest Bay tributaries during  1984 and
                                    1985 are shown below.
                                      River flow patterns in each Bay
                                    tributary are unique because rainfall,
                                    topography, land use, and other  factors
differ between basins.  For example,
Patuxent River 1984 and 1985 flows
differed from those of the Susquehanna.
Patuxent River flows in 1984 were close
to the long-term average as of that year
(421 cfs), whereas 1985 flows were 50%
below average. The James and
Rappahannock rivers, however,
experienced higher than normal flows
during 1984 (34% and  54%, respectively)
because of above-average winter and
summer discharge. Between the fall of
1984 and the fall of 1985, the James and
Rappahannock rivers experienced dry
conditions, with flows 20% and 35%
below normal, respectively. In
November 1985, tropical storm Juan
produced heavy rainfall in western and
southern Bay watersheds. While the
storm did not have much impact on the
Susquehanna, the Potomac and James
river basins were profoundly affected by
major floods.  Because the Bay is so
large, a single broad characterization
cannot describe the response of an
individual sub-basin.
                                                                             Mean monthly flows
                                                                              o
                                                                              • Potomac
                                                                              A James
                                                                              O
                                                                                PamunHey
                                                                                Mattaponi -•
                                                J FMAMJJASONDJ FMAMJj A ^ C3 N tt
                                                          19S4                       1985
                                     Freshwater flows into the Bay from these six rivers represent about 90% of all tributary inputs. Flows in 1984
                                     were substantially higher than in 1985. (Source: Maryland Office of Environmental Programs [MDOEP] and
                                     Virginia State Water Control Board[VA SWCB]) Pamunkey and Mattaponi are tributaries to the York River

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Depth
                                                                         I        I
                                                                      Dissolved
                                                                       oxygen
                                                                       (mg/l)
                                                                       1984
                                                                                 39°
                                                                 38°
                                                                37"   Latitude
                                                                      Dissolved
                                                                       oxygen
                                                                       (mg/l)
                                                                       1985
      Susquehanna  Bay
          River    Bridge
Potomac
 River
Mouth of
 the Bay
Susquehanna   Bay
    River     Bridge
Potomac
  River
Mouth of
 the Bay
             t      t
                                         t        t
  Salinity and DO patterns differ from year to year. The bold line represents the bottom of the mainstem, the thin lines represent either averaged salinity (ppt) or DO
  (mg/l) values at various depths. Salinity: the lower numbers in high-How 1984 reveal that much of the Bay experienced lower salinities in 1984 than in 1985.
  Dissolved oxygen: low DO values were more extensive in high-flow 1984 and were further down-Bay. {Source: MD OEP and VA SWCB)
    Salinities were higher and the
vertical salinity gradient was less
pronounced in the lower-flow summer of
1985.  In the deep-trough region of the
mainstem, salinities were  higher in 1985
than in 1984: surface salinities were
approximately 6 ppt higher and  bottom
salinities were about 3 ppt higher.
Similarly, in the Patuxent estuary,
salinities were 4 to 7 ppt higher and
stratification was reduced in  1985
compared to 1984.  In the Rappahannock
River, the same pattern of increased
salinity and decreased  stratification can be
observed for 1985 relative to 1984.
Stratification differences between the two
summers are reflected  in bottom-water
oxygen concentrations.

    Dissolved  oxygen  levels are high
throughout much of the year, in months
when water temperatures are low and  the
water column is well mixed. In the late
spring and summer,  however, high
oxygen demand in the sediment and the
rain of organics into the lower water
column, coupled with limited downward
                 Stratification is the layering of the estuary
               waters: freshwater stream/lows andseawater
               intrusion form two wedges of water going in
               opposite directions. The lighter (fresher) water
               flows on top of the heavier (saltier) water. These
               wedges create surface-to-bottom differences in
               salinity that significantly influence life and
               conditions in the Bay.
                 Stratification is strongest where the two
               wedges meet, and when river Hows are high.
               When stratification is strong, there is little mixing
               between surface and bottom waters.
                 Stratification is weakest at the sources of the
               wedges—the rivers and the ocean—and when
               flows are low. When stratification is weak,
               vertical mixing in the water column increases.
                 The maximum turbidity zone is an area where
               resuspension of bottom sediments is high. It is
               located at the upstream boundary of the saltwater
               wedge.  (Source: MD OEP and VA SWCB)
                          Maximum turbidity
                               zone
             Fresh water.
              river runoff
                e ™*»»* '***** * •v V* *," *.4 ?*'
                                        mixing of oxygen, cause the depletion of
                                        oxygen in deeper waters.
                                            Much has been written about the
                                        phenomenon of low dissolved oxygen in
                                        the Bay's deep waters.  Recent research
                                        efforts by numerous investigators are
                                        likely to shed additional light on the
                                        complex processes that cause, sustain,
                                        and interrupt anoxic and hypoxic
                                        conditions in this region.  The increased
                                        temporal and spatial sampling in the
                                        current monitoring program is making
                                        major contributions to understanding the
                                        Bay's oxygen.
                                            Strongly defined layers of water
                                        (stratification)  have a significant influenc
                                        on the DO characteristics of the estuary.
                                        Stratification inhibits the mixing of
                                        surface and bottom waters, and permits
                                        high  oxygen demands  from sediment anc
                                        the water column to deplete oxygen in th
                                        isolated, deeper water.  Higher than
                                        average flows resulted in  more
                                        pronounced vertical salinity gradients in
                                        the mainstem in the summer of 1984
                                        than in the summer of 1985.

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   Averaged longitudinal DO profiles for
the summers of 1984 and 1985 (shown
on page 4) demonstrate that high flow
permits more extensive regions of low
DO.  Oxygen conditions for comparable
salinity regions in the Bay's mainstem
and its major tributaries were similar.

               Mainstem
   In the mainstem there were several
differences between the two years,
especially in the spatial extent of hypoxic
waters (DO of <1.0 mg/1). In 1984
hypoxic water extended well  into
Virginia's portion of the Bay, reaching as
far south as the mouth of the
Rappahannock River. This did not
happen in 1985, when winds  and tides
caused more frequent re-oxygenation
events and reduced the duration of anoxic
conditions that summer.
   The summer 1984-1985 monitoring
results have shown that mainstem deep-
water dissolved oxygen concentrations are
more dynamic than previously expected.
Even during the summer  of 1984, when
density stratification was  unusually
strong, two major re-aeration  events were
documented in the deep-trough region,
one in early July and one in early August.
At least two re-aeration events were also
documented during the summer of 1985.
This means caution must be used when
comparing current data with data from
cruises in past years.
               Tributaries
   In the Rappahannock  River the clearly
defined stratification in the summer of
1984 appeared to have effects on bottom-
water dissolved oxygen concentrations
similar to those observed in the
mainstem: summer DO depletion was
severe and prolonged. In the Patuxent
River,  on the other hand, the  effects on
dissolved oxygen levels from the
difference in stratification between the
summers of 1984 and 1985 were not as
clearcut as the effects on the mainstem.
The  observed differences between oxygen
behavior of the Patuxent  and  that of the
Bay  indicate that factors other than
salinity stratification influence DO
conditions. Topography, localized storm
events, periodic exchanges with mainstem
waters, and the biological impacts of
nutrient loadings—conditions unique to
each basin-can also affect dissolved
oxygen concentrations.
         Chlorophylls are a group of green photosynthetic pigments that occur
      primarily within plant cells. Chlorophyll-a is the most important of the principal
      photosynthetic pigments. It is responsible for the green color in plants.
      Chlorophyll-a provides a measure of phytoplankton biomass levels, and is
      expressed in micrograms per liter (^g/l). Plankton and chlorophyll levels vary
      in the mainstem and tributaries; levels depend on season, nutrient availability,
      salinity range, and depth, and are influenced by external physical conditions
      such as river flow, sediment load, sunlight, and grazing of phytoplankton by
      zooplankton. As yet, there is no general agreement among scientists on
      target levels for chlorophyll-a.  A chlorophyll-a level of 100 |j.g/l is usually
      cause for concern, however.
    Latitude                                  •%  37WIWtcf;so''5
    Susqueharma River  39°35'      Potomac River  38°        J    «a
                            198*
Bay Bridge
Patuxent River
                   39°
                   38°18'
Mouth of
 the Bay
37°
Chlorophyll-a (chl-a ) levels indicate phytoplankton concentrations. These graphics show surface water chl-a
peaks near the Bay Bridge and just below the Potomac's mouth during summer 1984 and February-May 1985. In
bottom waters, chl-a levels were low in summer, but peaked in the winter/spring of 1985. (Source: MD OEP and
VA SWCB)
   Chlorophyll is found at the highest
levels in the tidal-fresh portions of the
tributaries from spring to early fall.
Plankton growth follows tributary
enrichment by nutrient-laden spring
flows.  The mainstem's higher
concentrations occur in the late winter and
spring.  The die-off and settling of this
large pool of organic matter probably
contributes to the spring oxygen demand
in both the water column and sediments;
this demand leads to the development of
summer deep-trough hypoxia/anoxia in
the mainstem.

               Tributaries
   Chlorophyll patterns in the tributaries
were similar in 1984-1985. The highest
chlorophyll levels in the tributaries were
observed in the warmer seasons above the
             maximum turbidity zones; in the cooler
             months the higher chlorophyll levels
             were found below the maximum turbidity
             zone.  Generally, the nutrient-rich upper
             reaches of the Patuxent and Potomac had
             higher chlorophyll concentrations than
             those of the James or Rappahannock.
             The Patuxent had the highest chlorophyll
             levels  of all the major tributaries.
                 The lower Potomac estuary
             experienced average chlorophyll values of
             40 mg/1 during spring 1985, with a peak
             in May of over 90 u:g/l.  Summer 1985
             chlorophyll levels peaked at unwelcome
             levels  of 100 (ig/1 in the  tidal-fresh
             reaches of both the Patuxent and Potomac
             rivers.
                 The peak chlorophyll concentrations
             in the  tidal-fresh regions of the James and

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    Rappahannock were 20-50 |ig/l and 20-40
    |4.g/l, respectively, with levels decreasing
    downstream to below  10 (J.g/1 near the
    river mouths.
                    Mainstem
        In  general, the upper Bay mainstem
    had higher chlorophyll levels than those
    found in the central and lower Bay
    mainstem; the lowest levels were found at
    the Bay's mouth.  The higher upper
    mainstem levels are largely the result of
    the greater availability of nutrients from
    the Susquehanna River and other upper
    Bay loadings.
        Chlorophyll levels had strong
    seasonal patterns with pronounced
    differences between mainstem surface and
Q  bottom waters.  During the late winter of
     1984-1985  and the spring of 1985, a large
    region of high chlorophyll (30-40 u,g/l)
    was observed in bottom waters. During
     summer hypoxia, bottom chlorophyll
     was very low (under 5 fig/1). During
     summer sporadic  peaks of surface
    phytoplankton growth (30-50 u.g/1) could
     be seen, chiefly in the central and upper
     Bay.  In the lower Bay toward the York
     River generally surface phytoplankton
     chlorophyll was low (5-15 Mg/1).
        Nutrients are a major focus of the
     Bay restoration program. While light,
     temperature, plankton grazing,  and
      Nitrogen (N) and phosphorus (P)
  are essential to plant photosynthesis
  and growth. These nutrients are
  supplied to the Bay from land runoff,
  the atmosphere, fertilizers and STP
  discharges. Nonpoint sources supply
  significant amounts of N (and in some
  tributaries, P); point sources are the
  major sources of P.
      The Bay and its living resources
  once assimilated additional nutrients
  from man's activities, but we have
  exceeded the Bay's capacity and now
  have undesirable phytoplankton levels
  in some areas.  The death and
  decomposition  of these algal plants
  contributes to dissolved-oxygen
  depletion.  Over the last several
  decades, nutrient levels have
  increased in many parts of the Bay,
  particularly in the upper, low-salinity
  reaches of almost all western
  tributaries.
      Sediment plays a significant role in
  nutrient transport and deposition,
  adsorbing both N and P, but primarily
  P. It is believed that there are large N
  and P reserves in bottom sediments
  and that, especially during the warmer
  months, substantial amounts of these
  nutrients are released from the
  sediments back into the water column.
  Such releases  can contribute to algal
  growth.
mixing in the water column play roles in
plant productivity, the levels of nitrogen
(N) and phosphorus (P) are the key
elements in the undesirable Bay over-
enrichment.
   Nitrogen: Between July 1984 and
September 1985, levels of total nitrogen
(TN) in mainstem surface waters ranged
between 1 and 2 mg/1 at the head of the
Bay, and from 0.4 to 0.7 mg/1 in the
lower Bay. The higher upper Bay levels
reflect the strong influence of
Susquehanna River inputs.  In summer
months, bottom-water concentrations of
inorganic N (and P) are high but surface-
water concentrations  are generally low.
    Values of TN were  higher (generally
at or above 2 mg/1) in the  tidal-fresh
regions of the Patuxent and Potomac
rivers than in the upper Bay mainstem. In
the tidal-fresh portions  of the
Rappahannock and James, however, TN
levels were comparable to those found at
the mainstem head.  In all the tributaries,
TN  declined somewhat in the salinity
transition zones, and declined further in
the lower estuaries to levels around
0.5-1.0 mg/1.
    The nitrogen enrichment found in the
tidal-fresh regions of the tributaries is the
result of both nonpoint and point-source
impacts.  Peaks in N during winter and
        Total nitrogen
        (mg/1)
        2.00
        1.33
Nitrates
(mg/1)
                       Latitude
                       Susquehanna River Mouth C39°35'), Bay Bridge C39°), Patuxent River Mouth C38°18'), Potomac River Mouth (38°) Mouth of the Bay (37°)
        Nutrient levels in the mainstem Bay in 1984-1985 are shown in these three graphics. The first two graphics look different, but are similar: the nitrate values shown in
        the middle make up a large portion of the total nitrogen values shown on the left. Highest nitrogen levels are up-Bay. Phosphate levels on the bottom of the Bay are
        generally low except during the warm months, when bottom waters become low in oxygen and phosphate is released from the sediments. (Source: MD OEPand VA
        SWCB)

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spring high-flow periods can be attributed
primarily to high nonpoint source loads.
   Phosphorus: The pattern of total
phosphorus (TP) concentrations is similar
to that for nitrogen, but not quite as
clearly defined. In mainstem surface
waters, TP peaked in the turbidity
maximum region at about 0.05 to 0.08
mg/1 and declined down-Bay to levels
generally less than 0.04 mg/1.
   During summer hypoxia in the deep-
trough region, P fluxes from the
sediments into the overlying waters (see
pg. 18). As with the bottom-water
accumulation of inorganic N, these higher
P levels may nourish summer algal
populations when and where vertical
mixing occurs.
   Tributary TP levels in 1984-1985
reveal differences between rivers.  The
Patuxent River had the highest TP levels
of the four major tributaries, with levels
in the tidal-fresh, transition, and lower
estuarine zones approximately 0.30-0.35,
0.25, and 0.1 mg/1,  respectively. The
Potomac and James rivers had similar TP
levels of approximately 0.15, 0.1-0.2,
and 0.05-0.010 mg/1 in tidal-fresh,
transition, and lower estuarine reaches,
respectively.  The lowest TP values were
found in the Rappahannock River, and
were approximately 0.05-0.10, 0.05-0.10
and 0.03-0.05 mg/1 in the tidal-fresh,
transition, and lower estuarine zones,
respectively.  TP showed surprisingly
little seasonal variation.
 2.0
 Mean total nitrogen (mg/1)
 25
 Mean total phosphorus (mg/1)
 32
                     CD Tidal fresh
     Patuxent  Potomac
      River    River
  Average total nitrogen and phosphorus
  concentrations in lour important Bay tributaries,
  July 1984-September 1985. (Source: MDOEP
  andVASWCB)

    The Susquehanna, Potomac and James
rivers are the three largest rivers
discharging to the Bay. Together these
three rivers represent 84% of the
freshwater flow.  The exact proportion of
the total river  input load represented by
these three rivers must be determined by
extrapolation of the monitoring data to
cover unmonitored portions of the
Chesapeake Bay watershed. Methods of
 extrapolation range from simple flow-
 base techniques to sophisticated watershed
 computer models.
    Based on the monitoring data, it is
 apparent that a simple flow-based
 extrapolation would not be very accurate.
 Considering only the flow and nutrient
 loads for 1984 and 1985 it is clear that, of
 these three rivers, the Susquehanna was
 the major contributor of flow and
 nutrients to the Bay. However, during
 the monitoring period, the Susquehanna's
 nutrient loadings (66% TN and 42% TP)
 were not in proportion to its flow (63%).
 If a simple flow-based extrapolation were
 used as an estimate  for TP loads for the
 Susquehanna, a 21% over-estimate would
 result.  Important factors unique to each
 watershed (topography, soils, land use,
 population density, etc.) also influence
 the magnitude of the loads delivered to the
 estuary and must be taken into account in
 order to produce an accurate estimate  of
 nutrient loads.
    Nevertheless, the strong influence of
 changing river flows on nutrient loads is
 clearly evident in both the long-term
 record of annual loads and in the  seasonal
 loads calculated from the 1984-1985
 monitoring data. In years and seasons
 when river flow  is high, nutrient loads are
 also high. For example, approximately
 80% of the flow and nutrient loads
 delivered to the estuary by the
 Susquehanna and Potomac in 1984 came
 in the winter and spring.  D
 Mean annual flow
Annual load of total nitrogen
Annual load of total phosphorus
 thousands of kilograms per day
 60
thousands of kilograms per day
400
thousands of cubic feet per second
   1978 79   80  81   82   83  84   85
                                             1978 79   80  81   82   83  84   85
                                            1978  79   80  81  82   83  84   85
  Annual flows and nutrient loadings for the Susquehanna and Potomac rivers between 1978-1985 are compared above. The Susquehanna is the largest Bay tributary.
  In 1984-1985, it contributed 63% of the freshwater flows to the Bay, and 66% of TN and 42% of TP. The Potomac's nutrient contributions are proportionately higher
  than its Hows. Approximately 80% of the flows and nutrient loadings delivered to the Bay's mainstem by the Susquehanna and the Potomac in high-How 1984 were
  delivered in the spring. (Source: MDOEP andVASWCB)

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                            Sediments  &  Toxics
8
Measuring Turbidity, or determining
the amount of suspended solids in the
Bay's water column, is important.
Turbidity can indicate conditions
detrimental to aquatic life.  Two
methods used to measure turbidity
are: (1) visibility measurement with a
Secchi disk; (2) measurement of total
suspended solids (TSS). Higher
Secchi depth readings mean lower
turbidity; higher TSS values mean
higher turbidity.  Measurements by
Secchi disk are made by simply
lowering the disk into the water and
recording the limit of visibility. Bay
Secchi depths generally range from
over 3 meters (clearer waters in the
winter) down to less than 1 meter (over-
enriched waters, usually in the
summer). In the tributaries and
mainstem, Secchi readings can drop
to as low as 0.1 meter following
storms. TSS is determined by
weighing the material filtered from a
known volume of water. The American
Fisheries Society has recommended a
TSS criterion of 100 mg/l (maximum)
for the prevention of mortality to fish,
zooplankton, and benthic animals.
                SEDIMENTS
                  Mainstem
       Monitoring in 1984-1985 confirmed a
    strong north-to-south turbidity gradient in
    the mainstem. Generally, turbidity is
    high in the upper Bay because of the
    Susquehanna's heavy flows and the
    turbidity maximum zone; it decreases
    gradually toward the Potomac's mouth.
       The maximum turbidity zone in the
    Bay proper occurs up-Bay of Baltimore
    near Aberdeen, Md.  Monitoring of this
    area revealed typically low Secchi depths
    (between 0.2 and 0.5 meters) and high
    TSS values (between 15 and 25 mg/l).
    Turbidity decreases gradually down-Bay,
    to a point just above the Potomac's
    mouth. Here the Secchi depths were
    higher (from 1 to 3 meters) and the TSS
    values lower (from 5 to 10 mg/l).
       In the central Bay, from the Potomac's
    mouth to that of the Rappahannock, there
    is sometimes an increase in turbidity.
    Here the  Secchi depths in 1984-1985 were
between 0.9 and 2.9, and the TSS values
ranged from 10 to 40 mg/l.
   From the Rappahannock to the Bay's
mouth the waters again become clearer.
Here Secchi disk readings ranged from 1
to 3 meters, and TSS values ranged from
5 to 15 mg/l.  At the Bay's mouth
turbidity is lowest.
   Lower Bay western shore waters are
generally more turbid than those along
the eastern shore: the earth's rotation
causes relatively clear oceanic water to be
deflected eastward as tidal currents move
up-Bay, and substantial quantities of more
turbid water are added by the discharges
from western Bay tributaries. These
show up as localized peaks in the lower
Buy in the Secchi depth graphic.

              Tributaries
   Between their turbidity maximum
zones and their confluence with the Bay,
the tributaries have turbidity and TSS
patterns comparable to those in the Bay
proper. Unlike the main Bay, however,
tributaries like the Patuxent, Potomac,
and James have large stretches of tidal
freshwater, where extensive high-turbidity
areas can result not only from re-
suspended sediment but also from algal
blooms.
   The Susquehanna's sediment loadings
(an average of 1.8 million tons annually)
strongly track with  river flow and are
delivered directly into the mainstem.  In
wetter periods, typically winter and
spring, sediment loads are much higher
than in the summer and fall, when flows
are generally lower. The Susquehanna is
unusual because  several reservoirs trap
sediment, at least temporarily, and
moderate loadings. The result is that  the
sediment contribution of the Susquehanna
River to the Bay is often proportionately
lower than its flows.
   The Patuxent contributes only 0.5%
of the Bay's freshwater flows, but its
sediment loadings are proportionately
higher than its flows. In the Patuxent's
maximum turbidity zone (in the vicinity
of Lower Marlboro), spring TSS peaks
exceeded 80 mg/l.  This high turbidity
results not only from loadings, but also
from the natural bottom-to-surface
mixing in the water column. Secchi
depths of 0.2 meters and less were
observed in the 1984-85 monitoring
period. In the lower Patuxent the waters
become comparable to those of the
mainstem at its confluence.
   The Potomac is the second largest
contributor of freshwater to the Bay but
contributes proportionately the most
sediment to the Chesapeake system.  An
estimated 1.5 million tons  are discharged
at the fall line in an average year. Most
of this sediment remains in the upper and
mid-estuary (there is a small net transport
of 1% from the main Bay  into the lower
Potomac).
   The Potomac's sediment loadings in
1984  and 1985 were 22%  and 126%
higher than average. The higher figure
for 1985 reflects the effect of tropical
storm Juan: approximately 1,134,000
tons of sediment was discharged from the
upper Potomac basin in  November alone.
   The average Secchi disk readings for
the Potomac in Washington, D.C. (where
algal  blooms also contribute to the river's
turbidity), ranged from just over 1.1
meters down to  0.6 meters in  1985.
Most of the heavily sediment-laden
Anacostia within the District of
Columbia had Secchi depth readings less
than 0.3 meters.
   The share of the total sediment
loadings into the Bay from Virginia's
James River is 16%.  The  upper reaches
of both the James and the  Rappahannock
have  comparable Secchi depths (0.6 m),
and both show a steady decrease in
turbidity from their tidal freshwater
portions to their mouths. Their lower
estuarine zones  show a  marked difference
however.  The James carries a heavier
load of TSS than the Rappahannock (13.3
mg/l  and 5.5 mg/l at the fall line,
respectively), and tends to remain turbid
longer. The average Secchi reading in the
lower James ranges from 0.9  to 1.4
meters, while the readings in  the lower
Rappahannock generally range from 1.4
to 1.8 meters.
   The James and the Rappahannock
experienced higher than normal flows in
 1984: 34% and 54%, respectively.
Between the fall of 1984 and October
 1985 both rivers experienced dry
conditions. The flow of the James was
20%  below normal; the Rappahannock
flows were 35% below normal. The
James was significantly affected by
tropical storm Juan.

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Turbidity
Secchi
depth (m
 4.5
Latitude
Susquehanna River 39°35'
Bay Bridge       39°
Patuxent River     38° 18'
Potomac River  38

              37°
Mouth of
 the Bay
Secchi depth readings can be converted to a relative
measure of turbidity, or a picture of the lack of water
clarity in the Bay. Turbidity can indicate conditions
detrimental to aquatic life. This graphic shows the
turbidity profile in the Bay's mainstem in 1984 and
1985. The higher values in the graphic indicate higher
turbidity (and lower Secchi depths). Shown is how
spring high flows affect turbidity, especially in the
upper mainstem. Most of the turbid water is near the
Bay Bridge in the area of heavy inflows from the
Susquehanna and other upper Bay tributaries.  The
highest turbidity was in the upper Bay during the
summer of 1984 and the winter/spring of 1985 during
periods of Susquehanna River high flows. (Source:
MDOEPandVASWCB)
                           |flth^flew-*rwlfl'i§nwd*Q   ::  .§      ThaarrniwI^etffnffrtiisontiiH^ns
                         .  reach the sea, the Bay's rivers        (at the fall line) from the Susquehanna,

                                                                ^.-^•^f'ii^a^^f'. Those*
                      after these waters have left the Bay,       toadings reveal that the sediment
                      the fine-grained, mostly inorganic   _  X:   contributions of the three rivers are .

                      that they have transported remain,  '"^£   flows. For example, while the Potomac
                      suspended in the Chesapeake's water     contributes W*£(tftim annual f tow to '

                      or^W Bay d^nrtfi we «HW roi^Ni ,       The flow p«it^^«aiehi-B^
for photosynthesis, changes the

and carries unwelcome trave
as excess nutrients and toxic

                      largest contributor of freshwater (50%)    estuary was 238 t
                                                             '   year of 1930, whereas 4,160,000 tons
                                                           ~'               '
         Nonpoint sources
         farm & urban runoff
         groundwater runoff
                 (S+N+T)
         Atmosphere (N+T)
         	
 Lighter freshwater
        - Point sources
         sewage treatement
         plants (N+T)
    Fresh-saltwater transition
     [maximum turbidity zone)
 The complex relationship between sediment, nutrients, and toxics and their pathways is simplified in this illustration. The atmosphere contributes toxics to the Bay, but
 the majority of toxics are introduced into the Bay system along with nutrients from both point and nonpoint sources. Sediments, particularly fine-grained sediments, can
 adsorb, transport, store, and release both toxics and nutrients.  Toxics and nutrients can pass up the food chain, be held in suspension, or be stored in bottom sediments
 for later release. (Source: NOAA/National Status and Trends,  MD OEP, VA SWCB and Virginia Institute of Marine Science [VIMS])

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        Some 66,000 chemicals are being
        used in t» O.S, of which 60,000
  have been classified by EPA as potentially
  if not definitely hazardous. It is not
  surprising , therefore, that toxic substances
  are found in Bay water and sediments. The
  Chesapeake Bay Program found the levels
  of both organic compounds and heavy
  metals to be unnaturally, sometimes
  atermfagly l»igh»'parleulaity aiound urban
  areas such as Baltimore and
  NorfolWHamplon Roads. In Patapseo River
  (BafflmoreJ stdhnenfe. metal
  concentrations as high as 140 times natural
  background levels have been found.
     Wh i le not cu rren By a serious th real,
  toxicants are being found in the tissue of
  the Chesapeake's living resources. The
  compounds of greatest concern are metals
  such as cadmtott, chromium, copper, zinc,
  lead, nickel ; complex organic chemicals
  such as polphfcwtRated Mphanyls (PC Be),
  chlordane, Kepone, polyaromatic
  hydrocarbons {PAHs), arid DDT; and other
  chemicals such as chlorine.  Limited
  studies of ambient levels of highly toxic
  tributyltin (used in boat anti-fouling paint)
  began In HiSat several harbor sites Bay-
  wide; results are expected fay spring of
     Low concentrations of these toxic
  compounds imy hawltte immediate
  effect on organisms, but long-term low-
  dosage exposure is not well understood.
  I ncreas ingly higher concentrations of toxic
  compounds cause reduced fish
  reproduction, deformities, and abnormal
  behavior; they nay exacerbate disease
  effects and cause eventual mortalities.
  Toxicants can cause an imbalance in
  species; they can be accumulated by
  organisms that reach tie family dinner
      To xic materials enter fee Bay system
  turner plante), and nonpotat sources (urban
  and agricultural runoff, dump sites, and tt»
  atmosphere). The major toxicant
  TartspotB* Is fte Bay system are the
  Ifeabelh Rtorand SaMmere Hartxsr
  (PsJapseofliwierj. Theaiajortlbuiarfes
  also contribute toxic loadings.
      TheOty estimated that over 800,000
  metric tons of 13 metals enter the Gay from
   The toa
-------
   Polynuclear aromatic hydrocarbons
(PAHs):  Studies elsewhere have
associated sediment contamination by
PAHs with occurrences of serious
histopathological cancers such as
cancerous lesions in fish. Although
disorders of this kind were not observed in
Bay croaker and spot, occurrences of other
types of lesions were correlated with
concentrations of total PAHs in sediment.
   Metals: Sample sites in the upper
Bay yielded consistently higher levels of
metals  in oyster tissue man sites in the
central and lower Bay. The relative roles
of contamination and natural processes
(availability of metals increases in fresh
water)  have not been determined. D
      Sediments bind metals and
   organics just as they do nutrients,
   transporting them to the Bay system
   from the rivers and land runoff, and
   then retaining them on the bottom of
   the Bay. More than 60% of the total
   input into the Bay of iron, manganese,
   nickel, lead, and zinc is held in the bed
   sediments.
      The ability of sediment to bind and
   store chemicals is related to the size
   of sediment particles. Fine-grained
   sediments have a relatively higher
   surface area per unit mass than do
   more coarse-grained ones.  Therefore,
   with all other factors being equal,
   those chemicals that associate with
   surfaces will be more concentrated in
   fine-grained sediments.  Fine-grained
   sediments usually contain a higher
   proportion of naturally occurring
   organic matter. Thus, chemicals that
   combine with these natural organics
   are more abundant in fine-grained
   sediments.  Also, fine-grained
   sediments have higher concentrations
   of metals.
      The natural variability of the
   contaminants in the system, seasonal
   cycling of pollutants within sediments,
   and the pathways by which these
   toxics go from sediment to the Bay's
   living resources are processes not
   fully understood.
 Monitoring lor toxicants has been conducted at 87
 stations along the mainstem of the Chesapeake Bay
 and in the Maryland tributaries. (Sources: VIMS, MD
 OEP, andNOAA)
     Chesapeake
   Toxicant Monitoring
          Stations
                                                                                                                             11
   VIRGINIA
O SetMmentand organic
   monitoring stations
   MARYLAND
   Sediment or§aotes tOKtes
   heavy metaf rojnitQrina. stations

   Bioaccumulation and sediment
   organic toxics ntonitorfnf sfatteftf
   National Status'artd Tr«nd& Pteflrurn  „  , -
  . Chesapeake Bay mussel Watch Stations ,    ftf
A Chesapeake Bay benthic surveillance stations

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                   Plankton   & The  Food   Chain
14
             They form a vast array of several
             hyrui red -species with such
        unfamiliar names as dinoflagellates,
* pinhead measures 2,000 |j.m across-
 and invisible to the unaided eye, or as
 large as a jellyfish. Millions of them
 can te present In alter of water,
 ThtWjaptwaif producers, teonsymers,
,~a«l            form the flr# Holt of
                        and
 interdependent food chain, and are
 critical in assessing the slate of the
                                 are
        photosynthesis: they use sunlight,
        carbon dioxide, water, dissolved
        produce the carbohydrates on which
        all life d epends. ' Most phytoplankton
        serve as tin important food source,
        take up carbon dioxide, and add
        G3«^entoitiawat«ieslymrt Problems
        develop when an overabundance erf
        dominating, and a depletion of oxygen
        as they die and decompose. Minute
        phytoplankton tentatively identified as
        cyanobacteria appear tjljettie most
        Chesapeake Bay.
           2o0$sntap ar elbe animal forms
        of plankton. Like phytoplankton, they
        are generally grouped according to
        size, from the smallest to the largest:
        m icrozooplankton (smaller than 200
        (im), mesozoo plankton, (larger than
        200 ^im) and macrozoopiankton (larger
        Iftan 500 u,m). They are usually the
        prime consumers of phytoplankton.
           Zooplankton include certain types
        of protozoans, rotifers, crustaceans,
        fish and shellfish. These usually
        cwerotiaiple tolntafe qre 0ft»cr!iieal
        food for larval and juvenile (and some
                    Many fishes
   Plankton and benthic monitoring
for the new cooperative Bay-wide program
was initiated in 1984-1985.  This
program is an important advance toward
understanding the Chesapeake Bay.
Plankton were collected at 23 Bay
stations simultaneously with water-
quality data, allowing biological and
water-quality data to be examined
together.  Benthic samples are collected at
86 stations.
                                                 Phytoplankton
                                        The Bay is one of the most productive
                                     estuaries in the world. It is not
                                     surprising, therefore, that the 1984-1985
                                     sampling revealed a continuous supply of
                                     phytoplankton. Phytoplankton activity
                                     is greater in the freshwater and transition
                                     (0.5-5.0 ppt) zones of the Bay and its
                                     tributaries where there are high nutrient
                                     concentrations.
                                        Maryland's 12-month sampling
                                     revealed high productivity in the upper
                                     freshwater portions of the Potomac and
                                     Patuxent. The upper two freshwater and
                                     transition stations in the  mainstem Bay,
                                     however, showed the lowest productivity.
                                     This low production was at the mouth of
                                     the Susquehanna, where high potential
                                     productivity is inhibited  by high
                                     turbidity. The highest productivity in
                                     Maryland's part of the Bay was found in
                                     the mainstem (mesohaline zone, 5-18
                                     ppt)  near the Chesapeake Bay Bridge.
                                        The seasonal pattern of phytoplankton
                                     productivity in 1984-1985 was typical:
                                     high late-summer productivity due to
                                     longer days and warm waters; a fall peak
                                     followed by low winter productivity; a
                                     major spring peak following an influx of
                                     nutrients with the spring freshwater
                                     inflows.
                                        Productivity and seasonal patterns for
                                     the Potomac and Patuxent were similar.
                                     The  Patuxent, however,  had higher and
                                     more frequent peaks of productivity than
any other area sampled.  Patuxent River
carbon fixation rates (a measure of
organic production) were 40% higher than
Bay rates, and chlorophyll-a  values (a
measure of biomass) were 50%-200%
higher.
   In terms of composition, diatoms
were dominant during the late-
winter/spring and fall blooms. Small
coccoid green cells (possibly
cyanobacteria)  were numerically dominani
in the Bay in Maryland the rest of the
year.  During 1984-1985, large quantities
of phytoplankton settled into deeper Bay
waters, where their decomposition would
further deplete  oxygen in bottom water.
   Virginia sampling of the mainstem
was limited to the three-month period
July-September 1985.  The data indicate:
diverse population patterns with distinct
differences in phytoplankton composition
and concentrations between the central anc
lower Bay; significantly greater
abundances and diversity in the deeper
water layer; a greater diversity and
concentration of species  near the Bay's
mouth.
                                                   Zooplankton
                                          During 1984-1985, microzooplankton
                                       were sampled in Maryland's portion of the
                                       Bay, and mesozooplankton were sampled
                                       in both Maryland and Virginia. As with
                                       phytoplankton, higher zooplankton
                                       biomass was found in the upper
                                       freshwater and transition zones. Maryland
                                       sampling revealed nothing surprising in
                                       species composition, abundance, or
                                       distribution: shrimp-like crustacean
                                       copepods, Acartia and Eurytemora, were
                                       the dominant zooplankters. In Virginia's
                                       lower Bay, isolated and unexpected high
                                       concentrations of copepods were found.
                                          Zooplankton seasonal peaks occurred.
                                       Coupled with phytoplankton growth,
                                       there were spring and fall peaks, which

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Species of phytoplankton (left border)
and zooplankton (right border)
accompany other Bay inhabitants
(center) whose life cycles include both
benthic and planktonic forms.
Complete life cycles are shown for the
blue crab (Callinectes sapidus) and
sea nettle (Chrysaora quinquecirrha).
Other species shown include:
Phytoplankton

   1    Cyanobacteria
   2    Cylindrotheca closterium
   3    Cyclotella meneghiana
   4    Katodinium rotundatum
   5    Ceratium lineatum
   6    Skeletonema costatum
   7    Rhizosolenia alata
   8    Prorocentrum micans
   9    Cryptomonas sp
  10    Chaetoceros decipiens
  11    Rhizosolenia fragilissima
  12    Cyclotella striata
 Zooplankton

   13    Keratella cochlearis
   14    Trochophore larva of oyster
   15    Daphnia retrocurva (rare)
   16    Bosmina longirostris
   17    Alona affinis
   18    Barnacle nauplius
   19    Blue crab zoea
   20    Trochophore larva of polychaete
   21    Acartia clausi
   22    Acartia tonsa
   23    Podon polyphemoides
 Benthos

   24    Nereis succinea
   25    Mya arenaria
15

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   Millions of animals live on or
burrow in the bottom of Chesapeake
Bay. They are known collectively as
the "benthos." Because of their limited
mobility (worms, clams, shrimp, and
snails) or lack of mobility (oysters and
mussels), they are good indicators of
localized water quality. Some, such
as oysters, crabs, and clams, are
commercially valuable. The less
familiar worms, small crustaceans,
snails, and anemones are also
important. Benthic organisms form
one of the major intermediate links
between the primary producers
(phytoplankton) and the higher trophic
levels such as fish and waterfowl.
Their burrowing and feeding activities
are also important in the nutrient
cycles that control the Bay's
productivity. The benthic community
is not uniformly distributed over the
bottom. Salinity, sediment type, and
dissolved oxygen are the major
determinants in their distribution.
Currents, pollutants, diseases, and
predation further shape their
distribution and abundance. The
greatest benthic variety (some 150
species) occurs in the saltier waters of
the lower Bay.
were more pronounced in the less saline
waters.  The monitoring results support
the concept of "coupling" between
phytoplankton and zooplankton: the
seasonal microzooplankton peaks
coincided with or followed by one month
the phytoplankton peaks; the
mesozooplankton peaks coincided with
the phytoplankton peaks during the
spring bloom, but at other times tracked
more closely microzooplankton
abundance. This phenomenon also
suggests that microzooplankton is an
important link between phytoplankton
and the larger mesozooplankton in the
food chain for much of the year.
                Benthos
    Over the last several decades, die
duration aai'extent of tow 
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                                 Citizen   Monitoring
     How Citizens Can Get Involved

   •Join the annual hunt for submerged
   aquatic vegetation;
   • Learn how individuals can reduce
   their contribution to pollution;
   • Participate in activities to restore
   and protect the Bay;
   • As a member of an organization, set
   up a water-quality monitoring project
   for a local watershed.
   CONTACT: Citizens Program for the Chesapeake
   Bay, Inc., 6600 York Road, Baltimore, MD 21212;
   or Kathleen Ellett, Citizen Monitoring Coordinator,
   Chesapeake Bay Program, 410 Severn Avenue,
   Annapolis, MD 21403.
   A citizen volunteer monitoring
program was started in the summer of
1985 by the Citizens Program for the
Chesapeake Bay, Inc. (CPCB).  The
program monitors the near-shore waters
of two major Chesapeake Bay tributaries,
the Patuxent and the James.  The purpose
of this program is to demonstrate that
volunteers can  collect reliable water-
quality data that will help managers detect
and assess long-term Bay ecological
trends for the near-shore habitat. This
pilot project will determine the
appropriateness of a larger, permanent
program.
   Data are being collected at 19 sites on
the Patuxent and 16 sites on the James,
from the head of tide to the mouth. Five
surface water-quality factors are measured
weekly at each site: water temperature;
pH (using a color comparator kit);
turbidity (using a Secchi disk); dissolved
oxygen (using  a micro-Winkler titration),
and salinity (using an hydrometer). In
addition, monitors record weather and
general ecological observations about the
site on the Data Collection Form.  They
send this data to the program coordinator
at the Chesapeake Bay Program Liaison
Office for entry into the Bay Program
computer and subsequent periodic
analysis.
   There are 37 participants in  the
program. Of those who originally started
in the program, 81% are still monitoring.
The citizen monitors come from a variety
of backgrounds and professions-farmers,
students, housewives, teachers, scientists,
bureaucrats, retired military, and medical
professionals are monitors. All
volunteers attend a training session and an
annual workshop;  they receive computer
printouts and plots of their data, plus a
newsletter.  The newsletter, River Trends,
contains monitoring results, informative
articles, and sampling tips.
   Results obtained so far indicate that
trained volunteers can collect quality-
controlled data. A comparison of citizen
data with data collected by the Virginia
Water Control  Board on the James River
and by Maryland's Office  of
Environmental Programs on the Patuxent
River shows similar results.
   The first comparison was made for
four stations on each river where the state
had a station close to a citizen  monitoring
site.  The results of the comparison
showed that dissolved oxygen and Secchi
disk readings were in close agreement; pH
values were similar.  Water temperatures
showed differences only during
extraordinarily hot weather when the
                  Citizen's Monitoring
                      Stations
  Upper Marlboro1
                                                                                   • Richmond
                            WlllUmlburg
       Citizen's Monitoring
            Stations
                                                                                                                 f
shallower waters of the volunteer
monitoring stations warmed significantly.
Salinity values were comparable,
although  the hydrometers consistently
read about 3 ppt higher than the
conductivity meters used by the state
agencies.
   Volunteers have demonstrated their
ability and willingness to collect data on
short notice during and after such tropical
storms as Gloria and Juan, when state and
federal programs were less able to respond
quickly.  Secchi disk depths recorded by
volunteers along the James River clearly
showed the increased river turbidity
following those two storms. In late
1985, citizens reported hypoxic/anoxic
conditions in the bottom waters of St.
Leonard's Creek, a tributary of the
Patuxent River. The main channel of the
Patuxent is known to have low dissolved-
oxygen levels in late summer, but low
D.O. levels had not been reported
previously in water as shallow as St.
Leonard's Creek (3-4 meters). The extent
and duration of this phenomenon was to
be explored in 1986.
   CPCB began sponsoring a similar
program on the Conestoga River in
Lancaster County, Pennsylvania in the
fall of 1986.  Similar projects  have been
started in Maryland with the help of
CPCB: on Back Creek in Annapolis,
West River in Anne Arundel County,  and
on the Choptank River on the Eastern
Shore.
                                                                                                                           17

-------
                     SAV
                      &  Nursery
      The restoration of submerged
      aquatic vegetation {SAV} is a
 Bay cleanup priority for mvsral
 reasons, One reason is is high
 primaiy productivity «*is high rate of
 biomassaocwnylation,' in addition,
 aquatic plants form an important (ink in
 the food chain,, betwwn. nytrterfe In
 thewstef eeJittMi and sediment, and
 the animals. Many waterfowl are
'
food; Aquatic plants are also
s*aAif^fttWltrtt'fc%jic»s^te« as
 species of commercially important fish
                '
                running" ol;#»
 nitrogen and phosphorus. Seasonally,
 SAV provides an important source of
                     '      '
 of
                            wry
                         Jnnmf
                       £»


                  Chesapeake Bay
                  submerged aquatic
                  vegetation (SAV), in
                  severe decline from
                  the late 1960s until
                  1984, showed an
                  overall increase of
                  26% (47,893 acres)
                  from 1984 to 1985.
                  The largest increase
                  was found mid-Bay,
          N  v     along the Eastern
Shore.  There was a slight decrease in the
upper Bay, and little change was observed
in the distribution and abundance of SAV
in the lower Bay. There has been some
slight improvement in the declining
numbers of migratory waterfowl,
especially in SAV-resurgent areas.

              Upper Bay
   There was a slight decrease of 4.5%
(7,472 acres) in the abundance of SAV in
the upper Bay zone, with declines revealed
in three of the four sections studied.
There was  a 142% increase (259 acres) in
the sparsely vegetated Eastern Shore
section, principally along the Elk and
Sassafras rivers. More than half (66%) of
this zone's  SAV is in the Susquehanna
Rats area,  and this zone is dominated by
wildcelery, Eurasian watermilfoil, and
hydrilla. Redhead grass and widgeongrass
dominate in the Eastern Shore area.
             Middle Bay
   The 1985 SAV "good news" was the
increase in grasses in all sections of the
middle Bay zone over the previous year,
resulting in a 389% increase (12,315
acres) for the entire zone. Even the
Patuxent River, while still sparsely
vegetated, showed a 401% increase (22
acres in 1984 to 109 acres in 1985). In
the Potomac River, increases were seen in
both the upper and lower sections, 140%
(3,557 acres) and 59% (941 acres)
respectively. Ten species of Bay grasses
were found in the upper Potomac section,
with Eurasian watermilfoil and hydrilla
the most prevalent.  Widgeongrass was
found to be the dominant aquatic plant in
the mainstem of the middle Bay zone.

              Lower Bay
   There were  no major changes in SAV
in the nine sections of the lower Bay zone
between 1984 and 1985.  The largest
change occurred in  the Reedville section,
where the 1985 survey revealed a decrease
of 34% (425 acres) in SAV distribution
from 1984.  Most of the Bay's grasses
(59%) are in the lower Bay zone, with
68% of this zone's vegetation located
along the Eastern Shore bay side. Bay
grasses are still absent in two of the six
areas of historical abundance in the lower
bay. Widgeongrass and eelgrass are the
dominant SAV in the lower Bay. D
                                           Analysis of surveys of Bay waterfowl over 39 years (1948-1986) by the
                                           U.S. Fish & Wildlife Service reveals that the overall long-term average
                                           population of Bay waterfowl during January is 1 million birds. The average
                                           for the 1980s is also 1  million birds, but the species composition reflects
                                           major changes. Of the thirteen species of waterfowl studied, only three had
                                           higher population averages in the 1980s than in the 1948-1979 period. The
                                           mallard and bufflehead have shown population increases of 16% and 17%,
                                           respectively. Canada goose populations have shown a more dramatic
                                           increase of 75% (apparently due to their finding food sources other than
                                           SAV). All other species, however, have shown significant declines. The
                                           declines in canvasback and redhead duck populations appear to be directly
                                           related to the degradation of waterfowl habitat in the Bay. A balanced mix
                                           of waterfowl species is not likely unless the Bay's SAV beds recover.

-------
         77°iOO'


       Kilometers
   0  10  20 30  40  BALTIMORE
	       WASHINGTON
^  '       ~*" DC
    Chesapeake Bay, '*-
	  submerged      *xS;v£
     aquatic
     vegetation
     monitoring zones
SAV
Thousands
of acres
75

50

25

0



Thousands of acres
150

100

50


*
0~
tf?
55
&
s?
^•tf
£*
1
ft£-
v*-
i*




1950 1985


—














1978 1984 1985
                                                                   SAV Beds
                                                                   aerial view
                                                                   U1985

                                                                   No growth
                                                                   in 1984
                                                                  Barren Island Pt
                                                                                                19

-------
                                  The   Harvest:  Finfi
20
      The esteemed striped bass, or
      "rockfish," can live more than 30
years and can grow to a great size While
the usual maximum size has been 60
pounds in recent years, rockfish weighing
over 100 pounds were recorded in the late
1800s, and have been occasionally
reported in recent years.
   In  its native range along the Atlantic
Coast, the striped bass spawns from
February through July. In the Chesapeake,
spawning generally occurs from late April
through May. Rockfish spawn in fresh or
nearly fresh water,  normally in the upper
tidal reaches of all major Bay tributaries.
The Chesapeake is regarded as the center
of abundance for the species, and
historically its migratory stocks have been
considered the major source for the Atlantic
Coast harvests. In  the 1970s, when
rockfish stocks were larger, it was
estimated that the Chesapeake stock
contributed 90% to the Atlantic Coast
striped bass harvests. With reduced Bay
stocks, the current  contribution would
appear to average  between 50% and 70%
Abundance, health, and conditions of
Chesapeake stocks are therefore critical to
the entire Atlantic fishery.
   The trend of decreasing numbers of
harvestable anadromous fish (estuarine or
marine fish that spawn in freshwater),
showed no change in 1984-1985.
Anadromous fish spawning results remain
poor, and abundance of juveniles low.
There is some optimism, however: the
most important anadromous fish, the
striped bass, or "rockfish," appears to be
benefiting from recent protective
regulations, and hatchery-release programs
have been initiated. Also, more data
about striped bass are now being collected
in the upper Potomac River, a significant
striped bass  spawning ground. An
excellent intermittent data base exists on
striped bass  spawning in the upper
Potomac. There has been a lack of
information, however, on juveniles and
adult fish in the river's reach in the
nation's capital.  The new data collection
program initiated by the District of
Columbia in 1985  will rectify this.
Also, the states are standardizing the
available Chesapeake Bay commercial
catch information on the most important
Bay fisheries.
   The health of the striped bass remains
a high-priority concern.  Research efforts
focus on  stock assessments, young-of-
year analyses, larval abundance and
transport studies, related habitat
investigations, hatchery restocking
programs, and laboratory toxicity studies.
   It appears that the striped bass
harvesting moratorium in Maryland and
the partial ban in Virginia are protecting
the important 1982 year-class as intended.
The marked increase in striped bass
observed in Virginia since 1981, and the
large numbers of young stripers caught in
unregulated D.C. waters in 1985, are
believed  to be a result of the bans.
   In 1985, Maryland banned harvesting
of striped bass because of the drastic
declines  in commercial rockfish landings
since the mid-1970s. Declines in
commercial fishery landings for both the
Chesapeake and the Atlantic reveal poor
recruitment into the fishery since the
1970 "super" year-class.  The 1982 year-
class of rockfish, which will not spawn
until  1988, is the object of protection
because  its abundance offers considerable
Mean number of striped bass per catch
30 Maryland 1954-1985
25
20
15
10
5
0


1954






n




n
55
—
-







n
—






—

—







—

60 65
—











—





Mean number of striped

5
4 r
3
<


0

i—
'





bass per catch
Virginia 1967-1985

i * No data 1973-1979

,


if
1967 70 72

*
"1
...

\\
fi

- |



80 82 84 85





—i

~



j_|



HBH

70 75

r

hn
80
—
1

41n

84 85
        Striped bass young-of-year indices (abundance) show great variability. Due to differences in habitat and capture method, the indices of the two states are similar, but
        not identical. The unusually high 1970 index dominates in both states. Virginia's indices increased steadily from 1981 through 1984, butdroppedin 1985. Maryland's
        indices have been very low since 1978, with the larger 1982 year-class the object of state protection. (Source: MD Department of Natural Resources [DNR] and VA
        Marine Resources Commission)

-------
  Commercial striped bass landings in pounds 1970*1985
 5000
                                       n Maryland
 4000
 3000
 2000
 1000
                                                            I Virginia
                                                It
                                                         n_nJMn.
        1970
72
74
76
78      80
82
84 85
   Commercial striped bass landings in Maryland and Virginia 1970-1985. (Source: NOAA/National Marine
   Fisheries Service [NMFS])
potential for increasing the spawning
stock.
   While Virginia is optimistic about the
number of rockfish in its waters, recent
stock assessment work has confirmed that
the 1982  year-class is the only reasonably
abundant one in Maryland.  Data reveal
very few fish older than the 1981 year-
class in the Potomac, and a very low ratio
of females—the egg layers on which good
year-classes depend-to males.  The
Potomac  pattern appears to be the general
case for Maryland's portion of the Bay.
   Maryland striped bass spawning
stocks have been low; they were lowest
in 1982 and 1983, and slightly higher in
1984 and 1985, largely due to the
protected 1982 year-class males. Striper
egg and larval abundance also continues
to be low.  Intensive Maryland habitat
studies, which seek to relate water quality
and other habitat factors to larval
abundance, are currently under way.  A
combination of low pH, which tends to
mobilize  naturally high levels of
aluminum (which impairs larval gill
function), and low hardness found in
some Eastern Shore rivers such as the
Choptank, may be causing significant
larval mortalities.
   Fishery biologists recognize that there
is a high  mortality rate (over 99%) in
early life history  stages of striped bass;
the mortality rate declines considerably,
however, when individuals reach the
juvenile or "fingerling" (2 to 5 months
old) stage.  Juvenile or young-of-year
abundance firmly establishes the strength
of the newly recruited year-class, and
allows projections of its contribution to
the commercial fishery  in subsequent
years.
                          Both Maryland and Virginia survey
                       juvenile striped bass annually.  Young
                       fish are trapped either by seine net (Md.)
                       or by seining and trawling (Va.).  The
                       young stripers are counted and the totals
                       averaged.  Due to differences in habitat
                       and capture method, Maryland and
                       Virginia juvenile indices are similar but
                       not identical. Maryland's more shallow
                       shoreline allows for more extensive
                       seining and higher young-of-year catches
                       than is possible along Virginia's deeper
                       shores. The Maryland indices, therefore,
                       will be higher than those in Virginia.
                          In Maryland,  a juvenile index of 8 has
                       been considered the minimum desirable
                       index because historically, year-classes
                       with an index of 8 or better have
                       apparently supported a commercial fishery
                       of 2 million pounds of stripers annually.
                       Since the 1970 year-class with a very
                       high index of 30, however, Maryland
                       juvenile indices have been alarmingly
                       low.  The 1982 index of 8.4 was followed
                       by low indices of 1.4 (1983), 4.2  (1984),
                       and 2.9 (1985). In the District of
                       Columbia, recent young-of-year averages
                       (not available prior to 1984) were also
                       low:  2.4 (1984)  and 3.9 (1985).  The
                       Virginia young-of-year indices, however,
                       show a steady increase from 1.6 (1981) to
                       4.4 (1984).  The  1984 index was the
                       highest number of juveniles recorded in
                       Virginia since the record 1970 year-class
                       with an index of 6.4.  The 1985 juvenile
                       year-class index of 2.3 was only average.
                           Since mortality of striped bass in the
                       wild is greatest from the fertilized egg
                       through the fingerling stage, hatchery
                       rearing may be a bridge  to an improved
                       fishery. Striped bass are now being reared
                       in U.S. Fish & Wildlife  Service and
Maryland hatcheries until the fall, when
they are less vulnerable and big enough to
be tagged and released into selected Bay
areas.  Experimental tagging and tag
recovery programs were initiated in both
Maryland and Virginia in late 1985. The
expectation is for a release of 3.5 million
fish in Maryland alone by the end of the
program in 1989. What has been learned:
a large number of striped bass can be
raised in hatcheries, tagged, and released
into Bay tributaries successfully.  The
next step is to determine the program's
impact.
   Stocks of other anadromous fish such
as shad, river herrings, and yellow perch
remain at all-time lows.  White perch
numbers are also low. Abundance
estimates of the harvest-banned shad from
1980 through 1985 indicate a trend of
generally increasing stocks, but numbers
of young-of-year and adults remain
extremely low.  Harvests of marine-
spawning fish, dependent on oceanic
rather than Bay conditions, are relatively
good.  Ocean-spawning menhaden, sea
trout, spot, and bluefish harvests
remained stable or increased during 1984-
1985.
   The first preliminary comprehensive
assessment on thirteen Bay species
(including striped bass) represents
progress in bringing together the
available commercial catch data in a
uniform manner.  Assessments of six
additional species are  scheduled.  While
the assessments are based on those fish
reported (as  opposed to those which may
actually have been caught), and while no
complete set of information exists for any
one of the Bay fisheries, the value of this t
preliminary effort is that it will more
clearly reveal important missing
information. HI

-------
                             The   Harvest:  Shellfish
         With oyster reproduction and
      survival declining seriously over the last
      decade, the higher spatfall in both
      Maryland and Virginia in 1985 was good
      news.  Over the 1984-1985 monitoring
      period, however, spat survival rates
      remained low and still unexplained. No
      changes were noted in the dismal picture
      for soft-shell clams, but the blue crab
      fishery remains healthy, if unpredictable.
         Rainfall and temperature are key
22   variables that determine oyster harvests.
      A strong correlation has been found
      between high salinity and good oyster
      reproduction.  Dry summers, for example,
      may provide the oyster with highly saline
      waters and good feeding and growing
      conditions as a result. This same kind of
      weather, however, can encourage oyster
      diseases. The significant effect of rainfall
      and temperature on the productivity and
      health of the Bay's resources is evident
      when one examines the condition of the
                Bay's shellfish, particularly in 1984 and
                1985.
                   While there has been no long-term
                trend in rainfall/salinity, there has been a
                distinct trend toward warmer falls and
                winters over the last 10 years.  The
                spring of 1985, with below-normal
                rainfall, was followed by one of the three
                warmest autumns in 30 years (which
                extended into the winter). The drier and
                warmer fall of 1985 resulted in a
                considerably longer spawning season  than
                that of 1984; the oyster spawning season
                extended beyond the normal June-
                September period into late October.
                   Both Maryland and Virginia had high
                spatfall as a result. Virginia's spatfall
                was moderate to heavy in the 1984  and
                1985 spawning seasons.  The heavier spat
                sets generally occurred in 1985,
                particularly on the James River seed beds.
                There was considerable temporal and
                spatial variability in the spatfall. The
                                           occurrence of heavy spatfalls, despite low
                                           brood stock, underscored the importance
                                           of local weather and climate in the
                                           determination of year-class strength.
                                              Although its 1984 spatfall (2.4 spat
                                           per bushel) continued a downward trend,
                                           Maryland found high numbers of spat on
                                           its 55 key oyster bars in 1985. The
                                           Maryland spatfall  average in 1985
                                           exceeded 100 spat per bushel.  The highet
                                           spatfall was welcome, but it was limited
                                           mainly to the mouth of the Potomac
                                           River and Maryland's Eastern Shore
                                           tributaries. This area is greatly reduced
                                           compared with  that area where high spat
                                           sets were recorded between 1938 and
                                           1965.
                                              The survival of spat to yearling
                                           continues to be of prime concern.  In this
                                           regard, unfortunately, 1984 and 1985 were
                                           not exceptions.  In Virginia, the state-
                                           wide poor survival of spat to yearling was
                                           evident in the oyster bar surveys that
      250
      200
      150
      100
      50
               n
                        Mean number of oyster spatset per shell
                        ~           Virginia 1965-1985
                           jonfciiij
                        1965
                                 70
                                         75
                                                 80
                                                      84 85
              Don
           n
                                         Mean number of oyster spatset per bushel
                                                              Maryland 1944-1985
                                                                   * No data
                nn
Dru J  I L
                                          II
            1944
50
55
60
65
70
75
8485
         Oyster spat set for Maryland (1944-1985) and Virginia's James River (1965-1985). The density of the annual spat set is a measure ol oyster reproductive success.
         Spat set is measured annually but with different methods by the two states. Maryland measures the number of spat per bushel; Virginia measures spat per shell.
         Shown here is the great variability of spat set in both states. The relatively higher sets for the two states in 1985 was good news. (Source: MDDNRand VIMS)

-------
  Commercial  oyster harvest in millions of pounds
  20
                                                                   Maryland
  10
                       I

                                                                  I Virginia
 I
      1S6S  70
74
78
82
84 85
  Commercial oyster harvests. Since the turn of the century, the trend has been one of decreasing harvests of
  smaller oysters. Even though management practices such as shell and seed planting have helped to stabilized
  the harvests since the 1960s, the current Bay-wide landings average around 2.6 million bushels (U.S.) annually.
  It has been estimated that the sustainable yield of Maryland oysters Is 2-3 million bushels annually. Virginia's
  oyster industry has not recovered from the disease attack of the late 1950s.  (Source: NOAA/NMFS)
followed the heavy 1985 spawning season
(predation by the abundant blue crab may
play an important role). Bay biologists
point out that the success of the oyster
fishery depends on a number of
consecutive years of above-average spat
set, as well as the absence of threats from
harvest pressure, disease, and lack of
dissolved oxygen.

   MSX and Dermo can pose serious
disease threats to the oyster industry.
MSX attacks adult oysters (the peak
period  of infection is June), flourishing in
the same saline conditions that favor
oyster production. Virginia's oyster
industry has been threatened by MSX
since 1959.  The organism has been a
problem in Maryland waters since 1963.
Maryland's high spat sets in the early
1980s were offset by an extensive
outbreak of MSX in the 1982-1983
season.

   While conditions in 1984 and 1985
were not conducive to  the spread of MSX
in Virginia, Maryland's lower Bay waters
experienced some Dermo mortalities and
conditions conducive to MSX infestation
in 1985.  Mortalities resulting from the
latter would be seen in 1986.
                The stocks of Maryland's soft-shell
             clams continue to be low;  1984 and 1985
             harvests were each only about 1 million
             pounds. The crab fishery remains the one
             source of "good news" for the Bay's
             fisheries, however. While historically
             crab harvests have fluctuated wildly, the
             fishery appears to be unthreatened. Both
             1984 and 1985 were good years for crabs.
             Bay-wide crab harvests were 59 million
             pounds and 46 million pounds in 1984
             and 1985 respectively.

                One reason for the lack of concern
             about this crop (the Bay's second most
             valuable), is because crab year-classes are
             believed to depend more on the
             environmental  conditions and
             hydrological effects associated with the
             Bay's mouth than other factors.  The
             higher salinity  of the Bay's mouth is also
             essential for crab spawning and larval
             growth. The circulation pattern at and
             outside the mouth of the Bay  can
             transport crab larvae into the up-Bay
             water currents  of the deeper, saltier water
             layers, or can carry them into ocean
             currents and permanently offshore. D
     The American oyster has been
     important to the Bay's economy
since the mid-1880s, when the
average annual yield for Maryland
alone was about 12 million bushels.
Since the turn of the century, the trend
has been decreasing harvests of
smaller oysters.  Even though
management practices, such as shell
and seed planting, have helped to
stabilize the harvests since the
1960s, current Bay-wide landings
average around 2.6 million bushels
(U.S.) annually.
   The density of the annual oyster
spat set is a measure of oyster
reproduction success. Free-swimming
oyster larvae (2 to 4 weeks old) drop to
the bottom to set; they attach to
suitably clean and firm substrate
(usually oyster shell) in order to grow.
These spatfalls are measured  annually
by Virginia and Maryland, and
monitored carefully since, in spite of
improvement in Virginia's spat sets
since 1980, there has been an overall
Bay-wide decline in spatfall for more
than ten years. Setting patterns and
survival rates have varied widely.
Spat set has long been considered a
reasonable indicator of subsequent
harvests, but its predictive value has
been reduced over the last couple of
decades because of poor spat
survival.
   In addition to low reproduction and
larval survival rates, increased
demand, and harvesting, oysters have
been affected by weather and
disease. Oysters require a salinity
range of 5-35 ppt. Freshwater inflow,
therefore, is a key variable affecting
reproduction and mortality.
   The oyster diseases known as
Dermo (Perkinsus marinus) and MSX
(Haplosporid/um nelsoni) have taken
their periodic tolls on the oyster
fishery. These organisms are
associated with higher salinities
(above 15 ppt), and are far more
regularly a threat in the saltier waters
of Virginia and lower Maryland. Their
attacks on middle and upper Maryland
Bay shellfish are less frequent but can
be devastating.
   The naturally fluctuating harvests
of the economically important soft-
shell clam have dwindled. The reason
for the soft-shell clam decline is not
apparent, although low-oxygen areas,
disease, and heavy harvesting are
suspect.
   Crab harvests are variable but
high, and the fishery appears
unstressed. The fishery is controlled
primarily by the better environmental
factors near the Bay's mouth, where
crabs spawn.

-------
             A  Case  Study:  The  Patuxent
     The Patuxent River w the longest
     Wrastaterlyerinttoiyland, and
its watershed fs the w% fti^or sub*
stale,
         , and ftndMng- have
                  ^
gaaHor ft» JWyxtht, fwwww, isle
order tb        t ttlftiHQ the good
b«t*4'*l                   wthh
                h^^efiutaBi

to
       jri     ''
                    fill tltese
                            in
land
Tlie teertorllfcft rfthi JPaiu»nt*as
evfcfertt tytttt
 wihtnfhe wrta^fwd.ffepp; 2?) has
 revealed increased nutrient
                          n^d tn
. have also been noted, such as drastic
 fraction of what ft was in the 1960s.
 Citizen monitoring stations

^ OEP water quality stations

 Sewage treatment plants

 Maximum turbidity zones
The Office of Environmental Programs
of Maryland's Dept. of Health and Mental
Hygiene initiated a $3 million Patuxent
River program in 1982. Known as the
Patuxent Strategy, the program's major
objective is to address the causes of the
observed water quality decline from a
basin-wide perspective. Research,
monitoring, and modeling will provide
managers not only the necessary
information to understand better the
processes affecting water quality, but
also the means to evaluate the
effectiveness of various management
options. (Source: EPA, MD OEP)
The Patuxent is approximately 110 mi
long from its origin on Parris Ridge to its
confluence with the Chesapeake Bay.
The river drains portions of seven
Maryland counties, and an area of
approximately 930 sq. mi. Its average
flow is 396 cfs; its contributes 0.5% of
the Bay's freshwater flows. The
Patuxent estuary is deep: it ranks sixth
in volume and second in average depth
of the Bay's primary tributaries. About
27% of the land is agricultural, 29%
urban, and 44% forested. The upper
25% of the basin lies within the Piedmont
Province; the lower portion is within the
Coastal Plain. High nutrient and
suspended sediment levels are the
primary water-quality problems.

-------
Historical data reveal the long-term undesirable trend of increased
nutrient enrichment and decreased dissolved oxygen levels in the
Patuxent River.

PHOSPHORUS  Two types of phosphorus (P) are commonly reported:  dissolved
inorganic P (DIP) and total P (TP).  The Patuxent's longest nutrient record is that for
DIP. DIP data collected at Broomes Island in 1939, 1963, and 1969 reveal significant
increases in DIP levels. Values of DIP near the mouth of the estuary have also
increased over the years. The estimated annual loadings of TP from upstream sources
to the Patuxent estuary for 1965:  180,779 Ibs; 1970: 341,717 Ibs; 1975:  608,476
Ibs; and 1985: 216,500 Ibs. During the 1984-1985 monitoring period, the Patuxent
River had the highest TP levels of the tributaries monitored.  The Patuxent River TP
concentrations in the tidal-fresh, transition, and lower estuarine zones were
approximately 0.30-0.35, 0.25, and 0.1 mg/1, respectively.

NITROGEN Of the nitrogen forms that are routinely measured, only nitrate was
measured in the Patuxent prior to major STP construction.  Shown at right is the
profile of nitrate values for Lower Marlboro in the low-salinity reach of the Patuxent.
The data reveal  a clear seasonal pattern of nitrate concentration, with high values in
winter throughout the estuary, and low values in the summer and fall. Nitrate values
tend to be strongly correlated with river flows.  The graph shows increases in nitrate
levels after winter periods in both 1936 and 1963, with a major increase in the latter.
Lower Marlboro winter values in  1969 were 8 times higher than those reported in
1963, and 20  times higher than those reported in 1936. The estimated annual total
loadings of TN from upstream sources to the Patuxent River estuary for 1965:
509,268 Ibs; 1975: 2,462,563 Ibs; and for 1985:  1,900,000 Ibs. The 1984-1985
values of TN  were generally at or above 2 mg/1 in the tidal-fresh river.

CHLOROPHYLL-a  Chlorophyll-a  values have increased over the years as shown
in the graph.  The data collected  at Benedict Bridge, Md., at the lower end of the
turbidity maximum region and in the mesohaline segment of the estuary, show that
maximum observed late-winter and spring values increased by over 100% between
1964 and 1969.  Excessive phytoplankton growth from the increased levels of
phosphorus and nitrogen was  becoming apparent in the early 1970s.  In 1984-1985,
the highest concentrations of chlorophyll-a during the warmer seasons were found in
the upper Patuxent estuary. Chlorophyll levels peaked at 100 ug/1 in the tidal-fresh
reach of the Patuxent in the summer of 1985.

DISSOLVED OXYGEN  The lowest DO levels generally occur in the deeper
bottom waters during warm seasons.  A comparison of the June and  August low DO
values in the lower Patuxent estuary's bottom waters in 1938 and 1978 is shown to
the right. The comparison reveals 1978 minimum DO levels substantially lower than
those observed in 1938, beginning at Benedict and continuing downstream. No zero
values were found in 1938, while zero levels were common in 1978. In the summers
of 1984 and 1985, the DO levels ranged between 5.0 and 9.5 mg/1 in surface waters,
and between 0 and 8.0 mg/1 in bottom waters. CPCB monitoring program volunteers
reported hypoxic/anoxic conditions in the bottom waters of shallow St. Leonard's
Creek in the summer of 1985. While the main channel of the Patuxent is known to
have low dissolved oxygen levels in late summer, low DO levels  have only
occasionally been reported in water as shallow as St. Leonard's Creek (3-4 meters).
(Source:  Chesapeake Biological Laboratory, University of MD)
       JFMAMJJASOND
    40
*=   30 -
   ' 20
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                                        25
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                              June
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                               -•-BAY

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              CONTRIBUTORS

The coordinated monitoring network, created on behalf
of the Chesapeake Bay Program, has drawn upon
government resources at federal, state, and. local levels,
and their contractors, and major university research
institutions throughout the Chesapeake basin. Their
coordinated efforts and dedication to the common goal
of restoring and protecting the Chesapeake Bay have
made this report possible. This report was assembled
by the Monitoring Subcommittee by authority of the
Chesapeake Bay Executive Council, the Implementation
Committee, the Citizens Advisory Committee, and the
Scientific and Technical Advisory Committee.

           FEDERAL GOVERNMENT

National Oceanic and Atmospheric Administration
National Ocean Service, Office of Oceanography and
    Marine Assessment, 6001 Executive Blvd.,
    RocMlle, MD 20852.  301/443-8501.  Charles Ehler,
    Director.
     David R. Browne, Cart W. Fisher, Bruce Parker.
    Rockwall Building, 11400 RockvBe Pike, Rockvilte,
    MD 20852.301/443-8655.
     John A. Calder, Gary Shigenaka.
Estuarine Programs Office, Universal Bldg. S,, 1825
    Connecticut Ave., N.W., Washington, D.C. 20009.
    202/673-5243. Virginia Tippie, Director.
     David M, Goodrich, Samuel E. McCoy, James P.
     Thomas.
US. Environmental Protection Agency, Region ill
Chesapeake Bay Liaison Office, 410 Severn Ave.,
    Annapolis, MD 21403.301/266-6873. Charles S.
    Spooner, Director.
     Richard BaBuk, Patricia Bonner, Nina Fisher,
     Catherine L. Leger, Kent Mountford.
Computer Sciences Corporation, 410 Severn Ave., Suite
    109, Annapolis, MD 21403. 301/266-6873. Lacy
    Nasteff, Director.
Environmental Photographic Interpretation Center, Vint
    Hill Farm Station, Box 1S75, Warrenton, VA 22186.
    703/347-6348. Sam E. Williams, Acting Chief.
     James Simons.
U.S. Fish & Wildlife Service
Annapolis Field Office, Chesapeake Bay Restoration
    Program, 1825 B. Virginia Ave., Annapolis, MD
    21401. 301/269-6324. Glenn Kinser, Director.
     Bert Brun, Charfes M. Wooley.
Patuxent Wildlife Research Center,  Laurel, MD 20708.
    301/498-0331. David Trauger, Director.
     Matthew C. Perry.
                   REGIONAL

 Chesapeake Research Consortium, P.O. Box 1120,
    Gloucester Pi, VA 23062. 804/642-7150. Maurice
    Lynch, Director.
     Ka'en L. McDonald
 Interstate Commission on the Potomac River Basin,
    Suito 300,6110 Executive Blvd., Rockviile, MD
    208!i2-3903.  301/984-1908. L.E. Zeni, Executive
    Director.
     Beverly Bandler, Mary-Ellen Webster.
 Citizens Program for the Chesapeake Bay, Inc., 6600
    York Rd., Baltimore, MD21212. 301/377-6270.
    Frances H. Fianigan, Director.
     Kathleen K. Ellett.
            DISTRICT OF COLUMBIA

Department of Consumer and Regulatory Affairs, 614 H
    Stre«t, N.W., Washington, D.C. 20001.  201/727-
    7170. Donald G.Murray, Director.
Department of Consumer and Regulatory Affairs,
    Environmental Control Division, 5010 Overlook Ave.,
    S.W , Washington, D.C. 20032. 202/783-3192.
    Anantha Padmanabha, Director.
     James Collier, James Cummins, Hamid Karimi.
 Martin Marietta envinwn&ntal %st*fns;^00 Rums^?
    Hd,, Columbia, MJ%04S.
    Talb^ Central (Manager.         •
     A. Frederick Hallaiwi, fm& Jays/toft
 University of Maryland; i5hes*pettefitoRigjc«l,
    Laboratory, Bo^, Soloirorta,
   .
 , Fa*%,
'
     Walter ft Bayrtefl,
                    "
 Un)vers% of Marytrrt,
 '   Laboratory, P.O. i*fc775» Carrt«dge,'MD 21 813.' -
                                            '" ! :
Susquehirma
   St,,Harfi$
   BtefcT,Director,
                                                                     VIRGIN!*'
                   MARYLAND

 Academy of Natural Sciences, Benedict Estuarine
    Research Laboratory, Benedict, MD 20612.
    301/274-3134. James G. Sanders, Director.
     David C. Brownlee, Kevin G. Sellner.
 Department of Health and Mental Hygiene, Office of
    Environmental Programs, 201 West Preston Street,
    Baltimore, MD 21201.301/225-6316. William M.
    Eichbaum, Assistant Secretary.
     Michael Haire, Robert Magnien, Robert Summers.
 Department of Natural Resources, Tidewater
    Adrnnistration, Tawes State Office Building,
    Annapolis, MD 21401.301/269-3767. Paul Massicot,
    Director.
     Stephen J. Jordan, Chris Bonzek, Cynthia
     Stonger.
College el WJIiam *t;M*y-r
.•  Science, GteadiiJp ioint, y* ;p06fej
   7000.' Frantf Oi
     Hert»rtAusBqi
     Huggett,
CM Dominion Untv*r'%.
   Labo«ory,
   Raym&nal W.
     Arthur J. Butt'   '     .
OWDominion University,Oept.
   Harold G. Marshall, Cfialrrnaft:
     Ray S. Birdsong, Uahiel 0»«
Virginia State WaW Gonttor Bbanf,
   St., Richmond, W23238,
   Burton,  Executive Director.       •/
     AlanE.PoiloA,BflbertC.-Sieafrl«tf,
Space limitations prevent the full listing of additional institutional and individual nteflies, but lh» Chesapeaks ffaf. • •
Program would like to acknowledge the cooperation of the following: €hesape«t» Bay Foundation, Mtejfopolilarl
Washington Council of Governments, Pennsylvania Department of Environmental ffesonrtes, Patprrw*? HtvW
Fisheries; Commission, U.S. Army Corps of Engineers (Baltimore and Norfolk Districts), U.S. O»pafW»ntotO4f&Js«,
U.S. Geological Survey, Virginia Council on the Environment, Virginia Game & W«nd FiShwSts Coonrtssion,
Virginia Marine Resources Commission.
For furthsr Information, write: the Chesapeake Bay Program, 410 Sewem Aw!,

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