United States
Environmental Protection
Agency
Washington. D.C. 20460
September 1982
&EPA
CHESAPEAKE BAY
PROORAM: TECHNICAL-
REPORT SUMMARIES
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Foreword
For hundreds of years Chesapeake Bay has provided the
natural resources for commercial and recreational pursuits.
The productive waters of the Bay support oysters, clams, crabs,
and commercial and sports fish. Migratory birds and waterfowl
find food in its waters and beds of submerged aquatic vegeta-
tion. The estuary is also used for assimilation of wastes from
numerous industrial and municipal dischargers. Rising pressure
on these resources, however, has put increasing demand on the
Bay's capability to maintain them. This pressure will no doubt
continue as the Bay area population increases in the future.
Congress, in 1976, recognized these problems and directed
the U.S. Environmental Protection Agency (EPA) to begin an
in-depth study of the Bay. In this study, known as the
Chesapeake Bay Program (GBP), research projects were conducted
on nutrient enrichment, toxic chemicals, and the decline of
submerged aquatic vegetation in Chesapeake Bay. All of the
research was directed toward helping decision-makers understand
some of the Bay's problems and know better how to regulate land
activities that could affect the Bay and its resources. These
investigations took place at many research institutes and
universities, and involved a cooperative effort among State,
Federal, and private organizations.
The research projects summarized in these compendiums
present an overview of our investigations into water quality
problems of the Bay. In addition, the projects form the
foundation for our second final report, Chesapeake Bay Program
Technical Studies: A Synthesis, and, as such, represent the
heart of the scientific knowledge gained during our program.
Tudor T. Davies, Director
Chesapeake Bay Program
Thomas B. DeMoss, Deputy Director
Chesapeake Bay Program
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903R821O3
U.S. Environmental Protection Agency
Chesapeake Bay Program
Technical Report Summaries
September 1982
This document provides summaries of 13 technical studies
initiated by the Chesapeake Bay Program.
A separate, more complete document, to be published sometime
this winter, will include approximately 25 additional summaries.
Credits
EDITORS: AUTHORS:
Debra Allender Barker Stephen Katsanos
Elizabeth Giles Macalaster Debra Allender Barker
Linda C. Davidson
PRODUCTION: Judy Broersma1
Ned Burger
Dorothy Szepesi Ian Gillelan
Janet Malarkey
Laurie Harmon
Contents
Introduction i
Nutrients 1
Toxic Substances 25
Submerged Aquatic Vegetation 37
Tables of Weights and Measures 57
Principal Investigators ....... 59
Reports to be Included in Final Edition 61
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Introduction
In the fall of 1977, State (Maryland and Virginia)
managers, EPA officials, and citizen groups cooperated to
identify ten major problem areas to be addressed by the
Program. Three of those areas received extensive attention:
nutrient enrichment, toxic chemicals, and the decline of
submerged aquatic vegetation. Forty principal investigators,
from more than 30 institutions and organizations, evaluated
ongoing research in the three problem areas and provided new
research efforts to help fill in the missing pieces. This
volume summarizes some of those projects.
The projects summarized in this report (and in the winter
edition) form the basis for the CBP's three primary phases.
From the research projects, as well as from other sources, a
synthesis of the most up-to-date knowledge of the three problem
areas was done. This is presented in the CBP's second final
report, Chesapeake Bay Program Technical Studies: A Synthesis,
which will be available this fall. Information from the
synthesis papers, together with other historical data, were
used in the second major phase of the program, a
characterization of the water quality and resources in
Chesapeake Bay. A report on this analysis will be completed in
1983. The final phase of the CBP, the management study, pulls
together knowledge gained from the synthesis of the CBP's
technical studies and characterization analysis, as well as
from the program's modeling studies. Pollution control options
determined from the management study are presented in the CBP's
last report which will be finished in 1983.
This report contains summaries of 13 research projects that
were initiated by the U.S. EPA's Chesapeake Bay Program, all of
which are available from the National Technical Information
Service. Our final edition, to be published sometime this
winter, will include approximately 25 additional summaries.
The individual project reports summarized in this volume can be
obtained from the National Technical Information Service at
5285 Port Royal Road, Springfield, Virginia, 22161
(703-487-4650).
NUTRIENT ENRICHMENT
The CBP studied nutrients because the natural process of
nutrient enrichment, or eutrophication, is being hastened by
anthropogenic contributions of primarily nitrogen and
phosphorus compounds. Though needed by Bay organisms to grow,
excesses of these nutrients can deteriorate water quality.
When nutrients are introduced into an estuary in excessive
amounts, detrimental effects may result. Growth of
phytoplankton may be stimulated, causing dense and unsightly
blooms. Or a few species may dominate, resulting in declines
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of other types and loss of species diversity. Although
phytoplankton blooms produce photosynthetic oxygen as they
develop, respiration may exceed photosynthesis as they die. As
a result, oxygen will be depleted from the water. In addition,
grazers and decomposers deplete oxygen by respiration as they
consume the phytoplankton. Consequently, oxygen depletion from
the water is a common corollary to nutrient enrichment.
To consider implementation of eutrophication control
measures in a manner beneficial to Bay resources, the
relationship of nutrients to water quality must be thoroughly
understood. Researchers have identified the fundamental
processes involved in the entire Bay system and historic trends
in nutrient enrichment as compared to current levels. This
effort has identified eutrophication trends and provided.a
better understanding of nutrient enrichment in the Bay.
TOXIC CHEMICALS
Before the initiation of the CBP in 1976, no systematic
study of toxic materials in the Bay had ever been attempted.
Toxic .-substances are usually defined as chemicals or chemical
compounds that can poison living plants and animals, including
humans. Two classes of toxic substances are potentially
damaging to the Bay environment: inorganic and organic
compounds. The inorganic materials are primarily metals. They
can be produced and delivered to the Bay by natural processes
as well as by human activities. Potentially toxic metals
include arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu),
mercury (Hg), lead (Pb), nickel (Ni), tin (Sn), and zinc (Zn).
Many of the organic compounds are products of human
activities. However, a few polynuclear aromatic compounds
(PNA's) can occur naturally, and thus augment production of
synthetic compounds. Some of the classes of synthetic organic
compounds found in the Bay include: pesticides; phthalate
esters; alkyl-benzines; plasticisers; polychlorinated biphenyls
(PCB's); and other halogenated hydrocarbon compounds.
To establish the role of toxic substances in the Bay
ecosystem, a thorough understanding of the Bay's chemical,
physical, and biological dynamics was necessary. It was
important to develop reliable information on the current level
of toxins in the Bay, as well as information on the sources,
pathways, and fate of these substances in the estuarine
environment. This was the first time a Bay-wide assessment of
baseline concentrations of toxic substances had been done.
Research efforts in the toxic substances program centered on .
obtaining this information by studying the behavior of toxic
materials coming from industrial, agricultural, and atmospheric
sources. From such studies, resource management and regulatory
strategies can be designed to reduce or eliminate environmental
hazards, and protect and improve the quality of the Bay.
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SUBMERGED AQUATIC VEGETATION
SAV has dramatically declined in the Bay since 1970. Such
a decline is a major indication of ecological change.- Because
of its value to the Bay as a food source, habitat, nutrient
buffer, and sediment trap, the CBP included it as a critical
research area. SAV is eaten by ducks, geese, fish, and other
species that benefit from its contribution to the
detritus-based food web (dead organic matter). SAV also
provides habitat for many organisms — nurseries for juvenile
stages of some fish species; refuge for molting blue crabs, and
other invertebrates. A stable habitat for infauna and a
substrate for epiphytic plants and animals is also provided.
Additionally, SAV buffers nutrients in the Bay by absorbing
nutrients from the water column during spring runoff and
releasing them in autumn as detritus. SAV is considered to be
a nutrient "pump," taking up nutrients from the sediment
through its roots and releasing them as detritus. SAV also
slows water movement, and its filtering action causes sediment
to settle to the bottom, allowing the binding of sediment which
helps to mitigate shoreline erosion and improves water clarity.
Correlating research results with information related to
the effects of human activities on SAV has enabled scientists
to determine the likely causes of the decline of these valuable
plants. This will lead to the delineation of environmental
conditions necessary for improved growth of SAV which, in turn,
will provide Bay resource managers with the information they
need to evaluate management options.
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NUTRIENTS
Governing Chesapeake Waters: A History of Water Quality
Controls on Chesapeake Bay, 1607-1972 3
Historical Review of Water Quality and Climatic Data from
Chesapeake Bay with Emphasis on Effect of Enrichment ... 6
Water Quality Monitoring of the Three Major Tributaries
to the Chesapeake Bay . 11
Ware River Intensive Watershed Study 14
Evaluation of Management Tools in the Occoquan Watershed . . 19
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Governing Chesapeake Waters: A History of Water Quality
Controls on Chesapeake Bay, 1607-1972
John Capper, Garrett Power, and Frank R. Shivers
Chesapeake Bay has been called the most-studied and best
understood estuary in the United States. Yet it. is practically
unexamined in the areas of the social sciences and the
humanities. The many planning documents, of which the Corps of
Engineers' Chesapeake Bay Study is the largest, are general
compilations of information and issues rather than original
pieces of research.
As a result, the present study has had the benefit of
little scholarship to point the way. For example, nowhere is
there even a simple compilation or listing of the State
agencies that have been involved with the Bay over time.
Records of what the government has been doing with the Bay,
written as they are in varying documents, and scattered in
various libraries in both Virginia and Maryland, have not found
their way into the numerous bibliographies that have been
assembled for the Bay. And the relationship of the governments
of both, states to the Bay is imperfectly documented. In
Virginia, the State Water Control Board did not produce annual
reports until 1972, the cutoff date for this study. In
Maryland, the reports of water quality agencies tend to be
perfunctory and repetitive, and give little indication of the
real issues facing the agencies over the years. The researcher
is forced to approach his material as though he were an
archeologist, finding a few shards here, a few bone fragments
there. Piecing together a coherent story out of the fragments
requires a certain amount of logic, a workable hypothesis about
the overall nature of the creature to be described, and some
theories about how the evidence fits together.
This report has relied primarily on written sources. Those
proving most fruitful have been the annual reports of various
state agencies; the occassional reports of study commissions
and blue ribbon panels; and the codes, statutes, and case law
of the two states. Agency files proved difficult to use
because they are boxed and stored, full of irrelevant material,
disorganized, and uncataloged.
Use has also been made of the abundant collections of
newspaper files in libraries. While newspaper articles may
have questionable accuracy, they identify key issues and place
them definitively in time. Without them, numerous
controversies, left only to the official archivists, would go
unrecorded. In this study, information from newspapers gives a
sample of issues, and shows the broad trends in water quality
awareness.
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Another useful source has been feature articles in
magazines. These are particularly useful, because they both
reflect, and partially shape, the public attitudes toward the
Bay. Changes in these attitudes provide data used throughout
the report.
Introduction
Although tens of millions of dollars have been spent during
the twentieth century for studies of the environmental quality
of the Chesapeake Bay estuarine system, little attention has
been paid to examination of the political, cultural, and
economic character of Bay governance.
As part of the Congressional mandate establishing the
Chesapeake Bay Program (CBP) , the Environmental Protection
Agency (EPA) was directed to review regional agencies
responsible for Chesapeake Bay management, issues of concern in
the region, and factors that must be considered in future
programs developed for management of Chesapeake Bay
enviromental quality.
This report discusses the physical, chemical, biological,
and engineering aspects of the Bay in the context of political,
cultural, and economic events which occurred nationally and in
the region between 1607 and 1972. The objective is to present
the debate concerning Chesapeake Bay quality as expressed
through changes in public opinion within the region and how
public attitude influenced the political process.
Procedure/Methodology
The authors drew on their expertise in the areas of
resource planning, legislation, and Chesapeake Bay history to
construct a temporal characterization of how the concept of
water quality has been defined and managed in the Chesapeake
Bay basin. In many respects the authors describe the history
of Chesapeake Bay uses, and how priority for specific uses was
established through the legislative process.
The authors, for the most part, relied on written sources
such as reports from study commissions, legislation, case law,
and, in some instances, regulatory agency files to describe
important issues which surfaced in the region during the 400
year recorded history of the Bay. The evolution of Bay
management is presented within the context of four eras:
Colonial times to the turn of the century; 1900 to World War
II; World War II to 1960; and 1960 to 1972.
Resuits/Conclusions
It is concluded that prior to the twentieth century the
Chesapeake Bay management focus was primarily concerned with
protection of public health and fisheries marketability. Only
recently has the public initiated efforts to establish
regulatory authorities directed toward enhancing or protecting
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Chesapeake Bay water quality. The authors maintain, however,
that Bay government agencies are often acting merely in
response to public opinion and political pressure rather than
following a course based on thoughtful analysis of
environmental and economic conditions.
- By Stephen Katsanos
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Historical Review of Water Quality and Climatic Data from
Chesapeake Bay with Emphasis on Effect of Enrichment
Donald Heinle, Christopher D'Elia, Jay Taft, John S. Wilson,
Marthe Cole-Jones, Alice B. Caplins, and L. Eugene Cronin
Review of available data on water quality in Chesapeake Bay
has revealed changes over recent decades caused by enrichment
with nutrients. In the upper and middle Bay, and several
tributaries, concentrations of algae during the summer months
have increased since the mid-19601s. There have been decreases
in the clarity of the water. This is associated with increased
algal stocks. Nutrient concentrations have also increased,
phosphorus more notably so than nitrogen. In some of the
tributaries, such as the Patuxent for which we have the most
historically complete data, increased algal production has led
to reduced concentrations of oxygen below the halocline in the
middle part of the sub-estuary. The variations in
concentrations of oxygen are now more extreme in surface waters
than in the early 1960's in the Patuxent. Oxygen
concentrations in the open Bay have not changed greatly, except
possibly under extreme conditions, such as during periods of
extensive ice cover. There have been historical variations in
the abundance of commercial fishery stocks that may be closely
related to climatic variations. Since 1969 or 1980, however,
stocks of many anadromous species and marine spawners that
represent higher trophic levels, have declined to new long-time
lows. The principal exceptions are menhaden (marine-spawning
planktivorous fish) and bluefish (marine-spawning top
predators). That same time interval has, however, been a
period of above average rainfall and corresponding reduced
salinities in the Bay, making conclusions concerning effects of
enrichment difficult to achieve.
Introduction
Enrichment of Chesapeake Bay waters by nutrients from
sewage treatment plants, and agricultural and urban runoff
emerged as a major water quality issue during the 1950's.
Population growth and the related changes in land-use, the
increasing reliance on secondary treatment of municipal wastes,
and the centralization of sewage treatment services in the
region's growing urban centers all contributed to increased
nutrient loadings in some segments of Chesapeake Bay,
particularly the upper Potomac River and Baltimore Harbor. By
1960 blue-green algae were creating nuisance conditions in the
upper Potomac, and detrimental quantities were common in
northern sections of the Bay ten years later.
The relationship between nutrient loadings from various
sources and algae production has been reviewed by a number of
Bay-area scientists, but trends and the extent of water quality
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changes have not been thoroughly documented. This report,
sponsored by the Environmental Protection Agency's Chesapeake
Bay Program, includes an historical review of Chesapeake Bay
water quality and climatic data and documents nutrient-related
changes that have occurred. The emphasis is on the effects of
enrichment by the major nutrients, nitrogen and phosphorus.
Climatic cycles are examined as well as the effects of one
unusual climatic event, Tropical Storm Agnes.
Procedure/Methodology
Temperature and rainfall data applicable to the Chesapeake
Bay region were compiled and examined for long term trends and
possible relationships to the 20 year solar cycle.
Fluctuations in annual mean water temperature were analyzed to
determine the general trends and the frequency of extremely
cold winters. Rainfall and freshwater flow data for the Bay
proper and major tributaries were examined to determine cyclic
trends and nutrient input factors. The frequency and intensity
of major storm events were also examined and compared to
detailed data describing the effects of Tropical Storm Agnes.
All precipitation data were used in the analysis of short-term
variations in freshwater flow. Long-term flow trends were .
determined by analysis of fixed-point salinity data.
The scientists developed estimated nutrient input values
for municipal wastewater treatment facilities currently on-line
and rated as capable of providing secondary treatment. The
loading figures for each major tributary in the Chesapeake Bay
basin (shown below) are based on the assumption that every one
million gallons of secondary effluent contains 73.8 pounds of
phosphorus and 182.6 pounds of nitrogen. The estimated total
point source loadings, based on permitted flow, for the entire
basin are:
Nitrogen
River
Susquehanna
Patuxent
Potomac
Rappahannock
York
James
Chesapeake Bay
(including
tributaries)
Kg day-1
28,841
2,203
38,864
795
323
16,151
108,916
106g yr'1
10,527
804
14,185
290
118
5,895
39,754
Phosphorus
Kg day"1
12,061
890
14,495
321
131
6,528
44,020
106g yr'1
4,402
325
5,290
117
48
2,383
16,067
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Flow data and an inventory of known point sources were used
to produce the following baseline estimates for flow in the
drainage basin and percentage of flow that is treated sewage
effluent:
27-yr average Point Sources Percent of freshwater
River flow (cfs) of sewage (cfs) that is sewage
Susquehanna
Patuxent
Potomac
James
Chesapeake Bay
38,800
1,085
13,900
10,100
75,200
557
41.15
670
302
2.034
1.4
3.8
4.8
3.0
2.7
Trend analysis was based on a review of demographic
statistics, land-use changes, and water quality data; the last
indicator gathered by a number of organizations involved in
sampling Chesapeake Bay waters as far back as 1940. All data,
unless clearly erroneous or suspect, were used. The
investigators attempted to document all analytical techniques,
identify data sources, and discuss the validity and
comparability of various analytical techniques.
Results/Conclusions
Many of the Chesapeake Bay water quality changes,
particularly in the tributaries, occurred prior to
implementation of pollutant discharge permit and monitoring
programs called for by,the 1972 Federal Water Pollution Control
Act. Trends for historic problem areas are difficult to
identify, but data clearly indicate that nutrient loadings are
increasing in historically-enriched areas and throughout the
Bay. Phosphorus loadings are increasing more rapidly than
nitrogen, possibly because of the use of phosphorus compounds
in detergents.
Carbon loadings are also continuing to increase despite
efforts to upgrade solids removal capabilities at municipal
wastewater treatment facilities. Removal capabilities were
improved between 1960 and 1969 through construction of
secondary treatment modes at public wastewater treatment
systems. Total carbon loadings have, however, consistently
increased throughout the 1970"s. Improved removal capabilities
at sewage treatment systems have been outpaced by increases in
regional population and increases in the percentage of
population serviced by centralized treatment.
The population increases and related land-use changes have
not been uniform throughout the region. The lower Susquehanna
River Basin, for example, experienced a 10 percent growth rate
between 1960 and 1970. The population in the Patuxent River
basin nearly doubled during this same period. Effluent
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discharged to the Patuxent rose at a more rapid rate than the
population, increasing from 2.6 million gallons a day (mgd) in
1963 to 26.6 mgd by 1973.
Changes in Chesapeake Bay water quality attributable to
land-use and demographic changes are not uniformly distributed
throughout the Bay. Upper Bay phosphorus concentrations,
variable and seasonal in the past, have increased and are now
relatively uniform all year. Nitrogen concentrations have also
increased, but some of the increased loadings appear to be
passing through the nutrient pool or are lost through
denitrification. Nitrogen appears to be the limiting nutrient
in the upper Bay, but low light intensity in this turbid region
could be restricting algae production. Overall, algae
production has increased.
The effects of nutrient enrichment in the middle Bay are
modest, but early signs of change are present. Current
phosphorus and chlorophyll a_ concentrations are slightly higher
than historic measurements and primary algae stocks show signs
of increased production. Dinoflagellate blooms are now common,
and some data suggest that the deep-water dissolved oxygen
minimum is changing. The effects of the altered dissolved
oxygen regime on remineralization from sediments are
significant and may be driven by particulate organic matter
deposition rates.
The lower Bay is relatively unaffected by nutrient inputs
although phosphorus concentrations have increased slightly.
The negligible increase in nutrient levels may be attributable
to dilution, which is significant in this region due to the
massive exchange of water at the Bay's mouth. Another possible
explanation is that nutrients are being trapped and utilized in
upper sections of the Bay. If light restricts algae production
in these upper regions, the nutrients might begin to progress
further down the Bay and stimulate algae production there.
Increases in algae productivity are now being observed below
the Potomac River.
Concentrations of both major nutrients and chlorophyll &_
have increased in all parts of the Patuxent River and
demonstrate a distinct downstream progression. Ambient
concentrations of nutrients in the upper, turbid portion are
relatively high all year. Although chlorophyll £ has increased
somewhat, light may be limiting primary production. Low
dissolved oxygen concentrations in the upper Patuxent appear
related to high concentrations of particulate carbon, not
chlorophyll. Both nutrient and chlorophyll concentrations have
increased in the lower river segments. Dissolved oxygen levels
in the surface waters are increasingly variable, and extended
periods of near anoxia in bottom waters are now being
observed. Plankton in the Patuxent demonstrate a high
dependence on recycled nitrogen during summer months, which
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suggests that restricting total annual input may limit primary
production. The changes now being observed in the river will
probably progress further as loading rates increase with
population growth in the basin.
Changes in the upper Potomac cannot be documented, because
dissolved oxygen and algae problems were present before
systematic sampling programs were put in place. Algae
production is increasing in the lower reaches, however, and
major changes might occur next near the upper limits of salt
intrusion.
The Rappahannock and York Rivers have both experienced
increases in phosphorus and chlorophyll a_ concentrations.
Trends for nitrogen cannot be determined. Minimum dissolved
oxygen concentrations in the lower York bottom waters have
decreased, but secondary effects have not been thoroughly
studied. Periodic anoxia in the lower York has resulted in
cyclic changes in rates of remineralization from sediments.
Conditions in the upper James are similar to those in the
Potomac. Historic conditions and changes are not well
documented, so trends could not be determined. Concentrations
of both major nutrients have increased in the lower James, but
there has not been a concurrent increase in chlorophyll a_. Low
dissolved oxygen levels in bottom waters have been observed
recently, but trends cannot be established.
Recommendations
Natural dissolved oxygen regimes have been altered by
nutrient inputs to some segments of Chesapeake Bay. Enrichment
problems are occurring in some areas of the Bay but are not
apparent throughout most of the estuary. Prudent, conservative
management can prevent continued degradation.
Sensible efforts to reduce nutrient inputs should
continue. Population projections for the watershed and present
evidence suggest that changes in the ecology of the Bay can
continue unless strategies for reducing nutrient inputs, such
as land application of municipal sewage, are sought and pursued.
- By Stephen Katsanos
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Water Quality Monitoring of the Three Major Tributaries to the
Chesapeake Bay
David J. Lang and David Grason
This project characterizes the inputs from the Susquehanna,
Potomac, and James Rivers — the major sources of freshwater to
Chesapeake Bay. The rivers were monitored for chemical,
physical, and organic components.
The Susquehanna was monitored at Conowingo, Maryland; the
Potomac at the Chain Bridge in Washington, D.C.; and the James
at Cartersville, Virginia. Measurements were made for
suspended sediment, nutrients, carbon, trace metals, key
metals, pesticides, major ions, chlorophyll &_, total solids,
and discharge. Scheduled frequencies of measurement varied
from daily to monthly sampling, depending on the type of
measurement. Supplemental sampling was used to assess the
impact of extreme events such as storms.
Study results provide estimates of pollutant loadings for
use in evaluating the effects of existing and future land-use,
water-use, and regional, economic developments in the
freshwater portions of the Susquehanna, Potomac, and James
River Basins.
Introduction
The objectives of this project were to provide:
1) Estimated loadings of major ions, suspended sediment,
selected nutrient species, and major trace metals for
the two-year data collection period.
2) An assessment of accuracy and limitations inherent in
these estimates.
3) Seasonal characteristics of nutrients, pesticides, and
chlorophyll ji collected during the study.
4) Relationships, comparisons, correlations, and trends
detected in selected water-quality constituents.
Procedure/Methodology
Water-quality data were collected from the three sites at
regular intervals during base flow, and much more intensively
during high flow. Daily or continuous data were collected on
discharge, suspended sediment, specific conductance, and water
temperature. Samples were collected, preserved, and analyzed
according to scientifically-accepted procedures.
Bivariate linear regression equations were used to estimate
all loads in this study. Logarithmic transformations of
constituent loads (computed from instantaneous concentrations,
discharges, and a factor to yield loads in pounds per day) were
regressed against logarithmic transformations of concurrent
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measurements of discharge, suspended sediment, and specific
conductance. The regression lines were fitted analytically by
the method of least squares.
Results/Conclusions
Month by month comparisons of loads do not compare as well
as annual total loads. This is because the regression
technique does not allow for seasonal and antecedent-flow
variations. The regression-load-estimations technique is most
accurate in wetter years having a wide range of flow.
Two pesticides were consistently detected at the Conowingo
and Chain Bridge stations — 2,4-dichlorophenoxyacetic acid
(2,4D) and atrazine, primarily in late spring and summer.
Maximum chlorophyll £ concentrations at all three sites
occurred during the high spring runoff, and are possibly
related to high velocity runoff in the spring. Concentration
peaks of lesser magnitude occurred during the late spring and
summer, and are possibly related to temperatures and nutrient
recycling.
Samples at selected Bay tributaries had total residual
chlorine concentrations of less than, or equal to 0.01 mg
L~l, the lower limit of detection for the technique.
Aluminum, iron, and manganese concentrations correlated
more closely with suspended-sediment totals than with discharge
totals at the Potomac and Susquehanna Rivers. Correlations for
the James River station were not as high.
According to discharge-weighted concentrations of sulfate,
the Susquehanna and Potomac Rivers carry greater sulfate
loadings than the James River, possibly due to coal mining
activities within the former two rivers' drainage basins. The
Potomac River at Chain Bridge has the highest
discharge-weighted average concentration of total nitrogen
(2.20 mg L~l), primarily in the form of nitrite-nitrate. The
James River at Cartersville has the highest discharge-weighted
concentration of both total phosphorus (0.42 mg L~l) and
orthophosphate (0.13 mg L~l).
In general, nutrient parameters associated with suspended
material relate better to suspended sediment, while
constituents with large solubilities relate better to
discharge. All of the nutrient parameters at the Susquehanna
River station correlate closely with discharge. For the
Potomac River site, however, some parameters correlate better
with suspended sediment, while others correlate better with
discharge.
Comparisons of data for the Susquehanna River at Harrisburg
and Conowingo indicate that loads of nutrients associate
closely with the water phase (dissolved). Orthophosphate and
nitrite plus nitrate, for example, increase in the downstream
direction. However, for total phosphorous, organic and
Kjeldahl nitrogen, organic carbon, aluminum, iron, and
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manganese (those parameters more closely associated with the
suspended sediments), loads near the mouth of the Susquehanna
River are less than those at Harrisburg, presumably because of
the effects of the intervening hydroelectric dams during years
of average streamflow.
High-flow sediment transport for the Potomac River at Chain
Bridge is heavily influenced by seasonal variations, form and
intensity of precipitation, and antecedent conditions.
Results/Conclusions
Water-quality loadings can be reasonably estimated by
regression techniques, especially for wetter periods of one
year or more.
Net transport of nutrient species and adsorbed constituents
is dominated by relatively few spring and storm-related high
flow events.
Atrazine and 2,4D are the two most consistently detected
pesticides at the Susquehanna and Potomac sites.
The sparsity of coal-mining activity in the James River may
be reponsible for the river's lower sulfate concentrations.
Phosphorus loads are increasing in the James, and
concentrations for both total phosphorus and orthophosphate are
higher than in the other two tributaries.
Peak discharges above 400,000 ft^sec"*- at the Susque-
hanna River at Conowingo resuspend sediments and their related
water quality constituents which had previously been deposited
behind the three.hydroelectric dams. These discharges also
transport constituents to the Bay in excess of those
transported 40 miles upstream at Harrisburg.
Sediment transport at the Potomac River site is heavily
influenced by antecedent and seasonal conditions in addition to
precipitation quality and quantity.
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Ware River Intensive Watershed Study
Gary F. Anderson, Cindy Bosco, and Bruce Neilson
The Ware River intensive watershed study includes
examinations of runoff from four small catchments, instream
transport of runoff, and their impacts on estuarine water
quality.
Runoff quantity and quality were monitored for row crop,
residential,and forested lands in the Ware basin for the period
of October 1979 to July 1981. Loading rates have been
calculated for both baseflow and stormflow contributions at
each study site.
Concentrations increased during stormflow periods for all
water quality constituents except dissolved silica. On the
average, levels increased by an order of magnitude above the
baseflow concentrations for particulate materials, and by a
factor of two for dissolved constituents. Concentrations of
total phosphorus, nitrogen, and dissolved ammonia were
substantially higher in the runoff at the two agricultural
sites than at the residential and forested catchments. The
residential catchment had high concentrations of dissolved
nutrients and BOD5 in both baseflow and storm runoff. Areal
loading rates were controlled by runoff quantity rather than
concentration. The residential site, which produced the
greatest amount of storm runoff, also had the highest loading
rates for all constituents except phosphorous and suspended
solids. The well-drained upland farm produced the least amount
of runoff of the four catchments monitored.
Baseflow accounted for a significant portion of the total
flow at the forested and residential catchments, especially
during winter months when the groundwater table was high.
Nearly half of the total flow measured during the study period
came from the ground. However, storm runoff produced 83 and 70
percent of the total phosphorus and nitrogen loads, and 62 and
91 percent of the BOD5 and suspended solids loads,
respectively. Although only 13 of 114 site-events had rainfall
greater than 5 cm, these accounted for more than 50 percent of
the total storm runoff measured.
Results from the study of estuarine waters indicate that
the Ware River contains a moderate amount of nutrients.
However, during summer months', some of the nutrients,
particularly inorganic phosphorus and organic nitrogen, reach
levels associated with excessive enrichment. The Ware is
typical of other small tributaries of Chesapeake Bay: nutrient
levels are higher at low tide, the estuary is more homogenous
laterally than longitudinally (with respect to nutrients), and
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vertical gradients exist for dissolved oxygen, total
phosphorus, and suspended solids.
The phytoplankton are generally phosphorus limited, except
during the annual spring phytoplankton blooms (April 1979 and
March 1980) when uptake of inorganic nitrogen by plankton
causes the system to be nitrogen limited. Impacts of nonpoint
source pollution are slight and short-lived in the estuary.
This appears to be due to dilution by Bay waters and
sedimentation in the upstream marshes. Thus, impacts are
typically observed only in the shallow upstream portions of the
estuary.
Introduction
The objective of the Ware River Intensive Watershed Study
was to characterize the contribution of various land-uses to
the nonpoint source loadings into the Ware River, a tributary
of Chesapeake Bay. The quality and quantity of runoff for the
major land-uses and physiographic features of the watershed
were measured over a two-year period. During that period, the
nature, extent, and duration of storm-water impacts on the
water quality of the Ware River estuary were also measured.
Procedure/Methodology
The sites selected for the study were occupied by land-uses
typical of the Chesapeake Bay region: a forested site, a
residential site, and two row-crop agriculture sites. These
types of uses occupy about 87 percent of the land area in the
Ware basin.
The undisturbed, mixed forest site was selected primarily
because the catchment was exclusively forested, yet easily
accessible for study. It has moderate slopes but poorly-
drained soils underlying the debris on the forest floor.
The low density residential site is a small subdivision
located adjacent to the shoreline of the estuary. It was
selected in part because the homes have septic tanks and
stormwater runoff is channeled through a series of roadside
ditches.
The two row-crop agricultural sites are in typical corn and
soybean annual rotation. Fertilizer application and herbicides
are used to control weeds. The lowland soils are poorly-
drained, while the upland soils are light, erosive, and well-
drained. Relief is more pronounced at the upland site.
Of the four sites, three have continuous baseflow during
winter due to high water table conditions. The upland
agriculture site exhibits no baseflow. Flows at all sites were
monitored by installing H-flumes in the drainage-ways.
Flow meters were installed at each flume to continuously
monitor baseflow and stormflow conditions. Automatic water
samplers were used to collect flow-proportioned-composite-
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samples during storms. In addition to runoff monitoring
instruments, a recording rain gauge sensitive to 0.01 inch was
installed at each site.
Samples were routinely collected during dry periods when
baseflow occurred in order to characterize loadings during
non-storm conditions. Baseflow and runoff samples were
analyzed for total and dissolved phosphorus, total and
dissolved Kjeldahl nitrogen, BOD5, suspended solids, total and
dissolved ammonia, nitrite-nitrate nitrogen, and dissolved
silica.
Estuarine water quality was studied to determine how it is
affected by runoff. Sampling stations were established
throughout the Ware River estuary and were sampled semi-monthly
throughout the 27-month study with runabouts. Submersible
pumps brought samples of water on board. In addition, several
intensive surveys were conducted on the river to provide a
comprehensive picture of how water quality varies temporally
and spacially in response to tidal and diel effects.
Monitoring was also conducted to study the nutrient dynamics
surrounding the spring chlorophyll a_ maximum and the response
of the estuary to nutrient pulse loads caused by runoff.
Results/Conclusions
Although nutrient concentrations in runoff from both
agriculture sites were significantly higher than at the other
two sites, so little runoff occurred that the total loadings
are lower than at either the forest or residential catchment.
The reduced flow (an order of magnitude below the other sites,
probably due to the fact that much of the rainwater is lost to
percolation into the rapidly permeable soils) more than
compensated for the higher pollutant concentrations in the
runoff. An exception is phosphorus, however, that had very
high concentrations in runoff from the cultivated fields.
Suspended solids coming from the denuded land were also very
high.
The forest and the lowland residential sites have
significant per area baseflow which was comparable in quality.
The baseflow loading at these two sites was a significant
portion of the total. Stormflow from the residential site,
however, was greater than that from the forest on an areal
basis. The manmade ditches and impervious surfaces (about 10
percent of the surface area at the residential site) were
expected to accelerate surface runoff there. Because nutrient
concentrations were generally higher in stormflow, the
stormflow loading rates and combined loading rates were higher
for the residential catchment. Another notable feature of the
residential catchment was the high loading of dissolved
nutrients in baseflow, particularly orthophosphorus and
nitrite-nitrate. This striking difference
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between the baseflow quality of residential and forested
catchments may be due to leaching from nearby septic tank
drainfields or application of fertilizers within the
residential area.
Baseflow accounted for 35 to 60 percent of the total flow
from the forested and residential sites. However, because
nutrient levels were higher in runoff, roughly 70 percent of
the phosphorus, nitrogen, and BODS, and over 90 percent of the'
suspended solids loadings occurred during stormflow.
Loading rates have been calculated for individual storms
which account not only for the catchment size but also for the
amount of rainfall. From these statistics, valid comparisons
among sites having different catchment areas and different
storm conditions can be made. Although the two agriculture
sites did have the highest individual storm loading rate, the
mean and median rates were greatest for the storms at the
residential catchment. That is, most of the time the loading
rate is highest at the residential catchment but, occasionally,
a very high rate occurs at the other sites. Occasional high
rates are important and were responsible for most of the total
load at the two agriculture sites. Analysis of individual
storms did not show any statistically significant relationship
between amount of rainfall, and runoff or loading.
Nutrient concentrations are generally low in the Ware River
estuary, especially when compared to freshwater tributaries or
to larger, more urbanized systems. Even following significant
rain events, extremely low nutrient concentrations for
silicates, total phosphorus, orthophosphates, suspended solids,
organic nitrogen, and nitrate-nitrite nitrogen were found in
the estuarine waters. Moderate nutrient levels were generally
found in upstream reaches where low TN:TP values are
attributable to the discharge of phosphorus-rich wastewaters.
Nutrient water quality at the mouth fluctuated little with
the tides; however, temporal variations in nutrient
concentration were seen elsewhere in the estuary within a tidal
period, especially in the brackish region. Maximum values for
total Kjeldahl nitrogen, ammonia-nitrogen, total organic
carbon, and total phosphorus occurred at times of low water
slack; minimum values were present at high water slack.
Nitrate-nitrite nitrogen concentrations were generally below
detection limit throughout the estuary during the survey.
Spatially, there was a distinct longitudinal gradient
present in the estuary. Although at no station or season were
anoxic conditions encountered in the estuary, the percent
saturation of dissolved oxygen was significantly higher at the
mouth than in the upstream reaches. The study average showed
90 percent oxygen saturation present at the mouth; the upstream
station had only 70 percent.
Similarly, a longitudinal gradient was evident during
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periods of runoff: freshwater storm influence was minimal near
the mouth of the estuary, whereas the upper reaches of the
estuary showed significant responses with respect to nutrient
concentrations and salinity gradients. During periods of
increased freshwater flow, a two-layer circulation system may
exist. Results indicate that the broad portion of the estuary
is essentially well mixed, predominately by tidal processes.
Recommendations
The overall impact of runoff on the Ware River estuary
appears to be slight and relatively short-lived. Impacts are
greatest in the marshes upstream. Nutrient loading rates vary
within and among each land-use site and appear to fluctuate
seasonally. The rates are a function of runoff quantity and
increase accordingly with the amount of baseflow. Further
study is needed to determine the relationship between loading
rates and rainfall amount. The data presented can be used in
conjunction with those from other watershed studies to
calibrate mathematical models of land runoff for the Bay.
However, the comparison of two very similar row-crop practices
showed large differences in pollutant loadings, illustrating
that soil, topography, and drainage properties must be
considered in addition to land-use when making such loading
projections. It is suggested that further watershed studies
monitor subsurface flow to adequately characterize low-lying
coastal watersheds.
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Evaluation of Management Tools in the Occoquan Watershed
Barren Weand and Tom Grizzard
During the period May 1979 to May 1981, nine water-quality
monitoring stations were operated in small catchments in the
Occoquan Watershed of Northern Virginia. The study sites
incorporated different land-uses (pasture-land, corn croplands,
suburban development, and forest) as well as contrasting
management approaches (heavy versus light grazing, no-till
versus minimum-till cropping, and detention ponds). Water
samples were routinely analyzed for total suspended solids,
ammonia nitrogen, total Kjeldahl nitrogen, oxidized nitrogen,
ortho-phosphorus, total soluble phosphorus and total
phosphorus. Meterological records were also kept during the
study period^and collections of dryfall and precipitation were
routinely analyzed.
Loading rates, calculated as kilograms per hectare per
centimeter precipitation, indicated that the heavily-grazed
pasture site generally exhibited the highest pollutant
concentrations. The forested site and lightly-grazed pasture
typically generated the least pollutant export. Significant
differences were observed between the no-till and minimum-till
croplands. The greatest differences were in the transport of
soluble nutrient forms. Results of measurements at the
storawater pond were sometimes ambiguous, but some evidence
indicated that proper maintenance of such a structure greatly
improves its efficiency.
Measurements of atmospheric pollutant loadings indicated
that the greater proportion generally came from wetfall.
Annual loadings for various constitutents were calculated. The
existence of acid rain in the study area was confirmed
repeatedly, and the source was hypothesized to be sulfur oxides.
Introduction
This study was designed to characterize nonpoint source
pollution from various land-use areas within the Occoquan
Watershed and to provide a basis for the comparison of selected
management practices. The data base was also intended to be
used in the calibration of a mathematical pollutant transport
model. Actual data collection began May 15, 1979 and continued
through May 31, 1981.
Procedures/Methodology
Nine monitoring stations were established in small
watersheds, primarily in agricultural areas. Drainage areas
appropriate to the established criteria were selected with the
assistance of the U.S. Cooperative Extension Service (CES), the
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U.S. Soil Conservation Service (SCS), and the Virginia Division
of Forestry (VDF).
Site one was a heavily-grazed pasture, as evidenced by
visible erosion and loss of vegetative cover. The soils in
this 12.7 hectare (ha) drainage area are moderately well-
drained and relatively inefficient in producing runoff. While
the upper reaches of the drainage showed a 4 percent average
slope and better cover vegetation, the lower drainage was
characterized by a 6 percent average slope and thin, poorly-
established vegetation.
Site two was a no-till corn field of 10.8 ha, which was
located on the same farm as sites one, three, and four. Soils
similar to site one were predominant, and a relatively uniform
slope of 8.5 percent was evidenced over the drainage area.
Drainage from this area entered the pond. After the first
season of monitoring, the management practice at this location
was changed to minimum-till.
Site three was a small area of heavily-grazed pasture
adjacent to site two and upstream of a farm pond. The drainage
area was 4.5 ha, with a uniform slope of about 10 percent. The
primary function of this station was to provide data on input
to the farm pond (see site four).
Site four was located immediately below a farm pond and
received runoff from sites two and three. Water flowed from
the 5-ha pond by means of a 10-cm diameter riser pipe. Pool
height in the pond varied seasonally according to precipita-
tion, and at times even the emergency spillway was overtopped.
Total drainage area to this lower station was 20.8 ha.
Site five was a very lightly-grazed pasture of 7.6 ha. The
average slope here was 3.5 percent, and canopy heights of over
60 cm were observed late in the growing season. This site was
paired with site one in an attempt to evaluate the effects of
different management practices on pollutant loadings.
Site six was originally set up at a no-till corn cropland,
but had to be abandoned shortly thereafter because of a change
in management practices and problems with landowner
cooperation. No data at this site were recorded.
Site seven drained 27.6-ha and collected runoff from a
suburban townhouse development via a 183-cm corrugated metal
pipe. The area was approximately 90 percent townhouse
development, and 10 percent open land. Flow from this drainage
proceeded to a dry, stormwater management pond, and was paired
with site eight.
Site eight measured outflow from the stormwater management
p'ond. Drainage to the pond included an area not measured at
site seven, for a total drainage area of 35.7 ha. A perforated
riser pipe provided detention in the pond, with the effluent
passing through a concrete conduit. Together, sites seven and
eight provided the potential for compiling a pollutant
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transport mass balance for the stormwater pond, and thus formed
a management pair.
Site nine contained 30.6 ha of hardwood forest. Because
the area was relatively undisturbed, this site represented
pre-development conditions. The average slope in the watershed
was 9.4 percent. Good under-canopy vegetation, and a thick
layer of litter reduced runoff potential at this site.
Site ten contained 10.4 ha of corn, representing
minimum—till management. The average slope was about 3.4
percent. This site was paired with site two in order to
compare effects of management practices on pollutant loadings.
Each monitoring station was equipped with instruments which
provded data on precipitation and runoff, and collected runoff
samples during storm events. At one station, samples of
atmospheric fallout were collected. Meterological parameters
— including so-lar insolation, mean wind speed, net
evaporation, temperature, and relative humidity — were also
measured at this station.
Most of the monitoring sites were fitted with a type-H
flume for primary flow control. Continuous stage measurements
were recorded using pressure, transducer-type flowmeters. Each
site also contained an automated sampler for the collection of
discrete samples and a tipping bucket raingage which recorded
rainfall in increments of 0.25 mm of precipitation.
The focus of the analytical efforts was on nutrient forms.
The following determinations were routinely made: total
Kjeldahl nitrogen (TKN); soluble Kjeldahl nitrogen (SKN);
ammonia nitrogen (NI^-N); oxidized nitrogen (ox-N), or
combined nitrate and nitrite nitrogen; total phosphorus (TP);
total soluble phosphorus (TSP); and total suspended solids
(TSS).
Other analyses were also carried out with less frequency
than those identified above. These included biochemical oxygen
demand (BOD), chemical oxygen demand (COD), lead, zinc,
pesticides, herbicides, and various soil parameters.
Re suits/Conclusions
During the study period (May 1979 through May 1981) a total
of 245 storm events we're monitored. The distribution of
monitored events was uneven, due to varying precipitation
patterns and different hydraulic efficiencies at each site.
Both median values for pollutant concentrations and
loadings measured at the various sites were used for
comparison. Whisker and box plots were also incorporated to
provide a better interpretation of the data distribution.
The cropland sites (sites two and ten) produced relatively
high nutrient concentrations in stormwater runoff. Pollutant
loads were also found to be higher at site ten. The use of
commercial fertilizers and animal manure on such lands
obviously contributed to the nutrient levels observed.
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As expected, the hardwood forest (site nine) and the
lightly-grazed site (site five) produced both the lowest
pollutant concentrations and loads. The lower levels of the
forest are attributed to its abundant ground cover and forest
canopy. The general lack of soil disturbance within the
catchments is probably the basic factor in the low production
of pollutants.
The concentrations of TSS, TKN, and TP were generally
higher at the heavily-grazed pastureland (site one), reflecting
the erodable nature of the soils in this catchment. As in the
case of the cropland site (site ten), site one had high median
loadings. The lowest concentrations were at the lightly-grazed
pasture site (site five) and forrested site (site nine).
Site seven, the suburban site, produced high levels of
pollutant concentrations and loadings. It is interesting to
note that the median loading of total nitrogen at this site was
as high, or higher, than those levels at the cropland sites.
This may reflect the use of fertilizers in the suburban
environment. The loading rates for total phosphorus and total
suspended solids showed a similar pattern.
Data variability was evident .among the parameters analyzed,
and from site to site. For example, site seven was sampled
more than any others and showed relatively small variabilities,
and may reflect the unchanging nature of the site. The
cropland sites (two and ten), however, undergo more
intermittent disturbances, resulting in greater variabilities.
In addition, some water quality data were collected on an
irregular basis. These data included concentrations of zinc
and lead, measurements of biochemical and chemical oxygen
demands, and analyses of pesticides.
Lead was detected only in the suburban catchment, and even
then infrequently. Zinc appeared to be much more prevalent.
The largest concentrations of total zinc were found at sites
one and two, which were located on the same farm. Zinc was
most consistently detected at the suburban site, but also found
in all samples analyzed.
Median values of COD at all sites were nearly the same,
except for the heavily-grazed pasture (site one), which was
much higher. The forest site exhibited the lowest COD
concentrations. In general, the BOD values measured were
rather low. This may be due, in part, to constituents in the
runoff (such as heavy metals or pesticides) which could inhibit
bacterial growth. Analysis of filtered and unfiltered samples
indicated that more than half of the BOD measured was soluble.
Analysis of inhibited and uninhibited samples indicated that
carbonaceous BOD represented 70 to 90 percent of the total.
During the course of this study, two sets of samples were
collected specifically for analysis of pesticides and
herbicides. The initial results were of some concern at that
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time because of relatively high concentrations of poly-
chlorinated biphenyls (PCB's).
A broader scan for pesticides and herbicides was carried
out seven months later. Levels of PCB's in these samples were
noticeably lower. None of these samples was filtered, so that
the variations observed in duplicate analyses might be due to
differences in the suspended matter included in each individual
sample.
Comparison of management practices indicated that the
heavily-grazed pasture consistently produced greater pollutant
concentrations than the lightly-grazed pasture. Statistical
differences in pollutant concentrations were found for TN, TSN,
TKN, ox-N, TP, and TSS. The similarity of these two sites, in
terms of soils and hydraulic efficiencies, underscored the
effect of management practices on pollutant export.
In comparing the no-till and minimum-till cropland site,
statistically significant differences in observed
concentrations were found for TN, TSN, ox-N, OP, and TSP.
These differences were related primarily to soluble nutrient
forms. During the study, site two was converted from no-till
management to a minimum-till approach. The data suggest that
both pollutant concentrations and hydraulic efficiencies
increased under the minimum-till management.
Initial study of the farm pond indicated that removal
efficiencies for suspended solids and nutrients were over 85
percent. However, allowance was not made for pond storage
capacity in these estimates. After a survey was conducted to
establish that capacity, an ensuing drought precluded
additional estimates from being made. Concentration data
alone, however, indicated high removal efficiencies for TSS and
TP (85 percent and 86 percent, respectively), and a relatively
low removal efficiency of 34 percent for TN.
Although 27 paired storms were monitored at the suburban
detention pond site, the results were often contradictory.
Because a satisfactory water balance could not be routinely
made between the monitoring stations used, it was impossible to
compare pollutant loadings with adequate confidence.
The cleaning (maintenance) of the stormwater pond during
this study provided an interesting contrast. Evidence suggests
that removal of most pollutants was increased after the
maintenance activity was completed.
Atmospheric loadings were measured using a wetfall/dryfall
collector located in an agricultural setting. Annual pollutant
loadings from wetfall commonly exceeded those from dryfall.
More solids deposition resulted from dryfall, however: over 60
percent of the total load (96.1 kg/ha/yr). Nutrient loadings
were 16.8 kg/ha/yr for TN, and 0.65 kg/ha/yr for TP.
The pH of precipitation measured during this study was
ordinarily in the range to warrant the term "acid" rain. The
range of pH values observed was from 3.2 to 6.1, with a
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median value of 3.8. Indirect evidence suggested that sulfates
were the causative factor.
The small catchments studied were all within the Occoquan
Watershed. Similar studies of larger basins within the
watershed were simultaneously carried out under the Occoquan
Watershed Monitoring Program. Comparison of these results
indicated that generally higher pollutant concentrations
occurred at the small catchment sites. Unit area loads,
however, were generally higher at the stream sites, due to the
greater hydraulic efficiencies of the larger basins.
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TOXIC
SUBSTANCE S
The Characterization of the Chesapeake Bay: A Systematic
Analysis of Toxic Trace Elements 27
Fate, Transport, and Transformation of Toxic Substances:
Significance of Suspended Sediment and Fluid Mud ...... 31
Dredging: Implementation of Innovative Dredging Techniques
in the Chesapeake Bay 34
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The Characterization of the Chesapeake Bay:
A Systematic Analysis of Toxic Trace Elements
H.M. Kingston, R.R. Greenberg, E.S. Beary, B.R. Hardas, J.R.
Moody, T.C. Rains, and W.S. Liggett
As part of a multidisciplinary study of Chesapeake Bay, the
National Bureau of Standards (NBS) was asked to develop the
techniques and procedures necessary to measure concentrations
of trace and toxic elements within the water column throughout
the length of Chesapeake Bay. The Inorganic Analytical
Research Division of the Center for Analytical Chemistry at NBS
has completed the analysis for selected elements [cadmium (Cd),
cesium (Ce) , chromium (Cr) , cobalt (Co), copper (Cu) , iron,
(Fe), manganese (Mn) , molybdenum (Mo), nickel (Ni), lead (Pb),
scandium (Sc), tin (Sn), thorium (Th), uranium (U), and zinc
(Zn)], including some elements at concentrations consistently
below one picogram per milliliter.
The characterization of Chesapeake Bay was divided into
five major phases. The first included the development and
construction of a sampling system for the trace metallic
elements dissolved in water and a filtration system for
collecting the particulate elemental component.
The second phase consisted of sampling chemical
stabilization by acidification and storage of the samples in
the field. The total complement of 102 samples was obtained,
filtered, acidified, and stabilized. There were also 51
replicate bottom samples obtained and frozen for archival use.
A series of over 30 blanks was also prepared and integrated
with the 102 water samples to be analyzed.
The third major phase of activity consisted of the chemical
separation and preparation of samples for the analytical
instrumental methods. The chemical separation/sample
preparation stage of this work has been described in the
literature for both instrumental techniques.
The fourth major phase consisted of instrumental analysis
of the samples for the trace elements. The total number of
elemental concentrations resulting from the analyses of the
contracted elements exceeded 3000 and involved several thousand
more unreported analyses totaling over 5000 separate
determinations.
The fifth major phase involved data reduction and
evaluation of the statistical significance of the blank. The
blanks were statistically modeled for each element, and the
blank and uncertainty of the blanks were applied to the data.
The concentrations were adjusted uniformly to at least the 95
percent confidence limit.
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Introduction
This report describes the National Bureau of Standards'
(NBS) efforts in a raultidisciplinary study of Chesapeake Bay
coordinated by the U.S. EPA's Chesapeake Bay Program. The NBS
used the best available technology to determine the_trace and
toxic element concentrations in the water column. As part of
this program, the NBS collected and analyzed both the dissolved
and suspended particulate fractions of 102 water samples
covering the entire length of Chesapeake Bay. The elements of
interest include Cd, Ce, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sc,
Sn, Th, U, and Zn. Specific chemical pre-concentration,
separations, and manipulations were used to prepare the samples
for analysis by Neutron Activation Analysis (NAA) and Graphite
Furnace Atomic Absorption Spectrometry (GFAAS).
Except for neutron activation analysis and anodic stripping
voltammetry, no analytical techniques are currently available
for the untreated sample determination of trace elements in
seawater at concentrations below 5 ug L~l. Usually, it is
necessary to preconcentrate the trace elements from a large
volume and separate the transition elements from the alkali and
alkaline earth elements. In such sample preparations, the
efficiency of concentration, completeness of separation, and
total analytical blank become critical to the final
instrumental method.
A more recent separation procedure utilizing Chelex resin
produced a sample devoid of alkali, alkaline earth, and halogen
elements, and left a dilute nitric acid/ammonium nitrate matrix
containing only the trace elements of the seawater sample.
This procedure was used in conjunction with GFAA to analyze
Chesapeake Bay estuarine samples.
Procedure/Methodology
A method of preparation for solid samples from 100 mL of
estuarine or seawater, using Chelex 100 resin, followed by the
determination of 12 trace elements by NAA was used in this
study. This procedure has been used to analyze NBS SRM 1643a,
as well as high salinity water samples collected near the mouth
of Chesapeake Bay.
The extremely low trace concentrations in these estuarine
waters made the procedural blank critically important. The
integrity of the sample can be compromised by just brief
exposure to normal laboratory air, or less-than-exhaustively-
cleaned containers. In addition, the extremely high
concentrations of alkali, alkaline earth, and halogen elements
in the marine water matrix make direct analysis difficult, or
impossible for most analytical techniques.
To circumvent these problems, special chemical and
instrumental procedures were developed. Chemical
separation/preconcentration procedures based on the chelating
resin Chelex-100 were applied prior to NAA and GFAAS analysis.
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The elimination of the matrix elements allowed the
determination of many elements that could not otherwise be
analyzed, and enhanced the sensitivity of other elements of
interest. The control of the blank in this procedure has
enabled its contribution to be sufficiently low that it did not
limit the measurement of most elements in pristine samples.
To ensure sample integrity and accurate analytical blank
determinations, 30 dissolved and particulate blanks were
prepared during the sample collection. The blanks were then
carried through all manipulations and analyses as additional
samples.
Evaluations were made using statistical comparisons with
data of known statistical reliability. The analysis, blank
contribution, corrections, and mathematical manipulation of the
data in this report have resulted in 58 data sets which are of
known statistical reliability. These data sets contain the
sample numbers arranged in a numerical sequence approximating
the geological arrangement of Chesapeake Bay, from Susquehanna
River to, and including, the Atlantic. Ocean. The
concentrations are given as a best value, and as a maximum and
minimum value which represents at least the 95 percent
confidence limit of the concentration. The significant figures
of each concentration are determined by the range of the
maximum and minimum value.
Although initially it may appear of uncertain interpretive
value, a technique using mathematical ratios was used to look
at relative amounts of elements. Scandium was chosen for this
purpose, because it has relatively few anthropogenic uses.
Because it is not used in a refined form in industry, and is
refractory in nature, it is not expected to be introduced into
the environment in an enriched state or in significant
quantities. When these ratios are divided by ratios of average
crustal material, a crustal enrichment factor (EF) results.
This is done for convenience and also to allow a crude
comparison with naturally-occurring material.
In these data the concentrations from Wedepohls"
compilation for crustal elements has been used. Similar,
though not identical, results could be obtained using other
compilations. Additionally, the computation of EF's relative
to average soils and average sedimentary rocks would be of
value to see how the suspended sediments of Chesapeake Bay
differ from those natural materials.
Ideally, the EF's for each element will remain constant if
the sources contributing to the suspended sediment remain the
same. Although the concentration of the various elements may
fluctuate several orders of magnitude from sampling to
sampling, the EF's should be constant if the sources are
constant as they are not affected by mass loading.
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Results/Conclusions
Uses of these EF's to produce an interpretive model for
evaluating and concluding elemental relationship and origins
can be postulated. However, actual conclusions cannot be drawn
until a rigorous scrutiny of the statistical significance of
the individual sets of enrichment factors has been completed.
Because this technique has not been used previously for water
particulates, many cross references between elements and
geological positioning, as well as within set limits, must be
evaluated.
In this report, the enrichment factors normalized to the
Wedepohl crustal numbers have been given without interpretation
to at least the 90 percent confidence limit.
These data are of sufficiently well-known reliability that
statistical comparisons result in significant trends of known
reliability. This work has not been included in this report
and is sufficiently complex to comprise a separate
recently-begun effort.
-By Ian Gillelan
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Fate, Transport, and Transformation of Toxics Substances:
Significance of Suspended Sediment and Fluid Mud
Maynard Nichols, Richard Harris, Galen Thompson, and Bruce
Neilson
This research aimed to determine the distribution of
selected metals in suspended material and fluid mud, to
identify potential zones of toxic accumulation, and to trace
their transport routes.
Observations of flow, salinity, suspended material, pH, and
dissolved oxygen were accomplished in Bay-wide longitudinal
sections and at four anchor stations in the northern Bay
between March 1979 and April 1980. The observations cover a
range of conditions, including seasonal high-low river
discharge, sediment influx, neap-spring tide range, and
oxygenated-anoxic water. Samples of suspended material, fluid
mud, and bed sediment were analyzed for their particle size,
organic matter, and metal content.
Metal concentrations of arsenic (As), copper (Cu),
manganese (Mn), nickel (Ni), lead (Pb) , tin (Sn), and zinc (Zn)
in fluid mud and bed sediment per gram of material decrease
seaward from a maximum in the Baltimore-Susquehanna River
area. The metals Mn, Pb, and Zn are four to six times greater
than Fe-corrected average shale, indicating major human input
and significant accumulation in this zone.
Metal concentrations of cadmium (Cd), Cu, Pb, Ni, and Zn
are maximal in surface suspended material from the central
Bay. They are higher than landward, near potential sources,
and they exceed concentrations in bed sediment two to 80
times. The enrichment is not natural compared to average shale
or plankton; it is most likely created by bio-accumulation.
Transport of particle-associated metals from major sources
follows either hydrodynamic pathways leading to particle
accumulation by the estuarine circulation, or bio-ecological
routes leading to bio-accumulation.
Management and monitoring strategies can reduce potentially
toxic metals to acceptable levels and warn management agencies
of toxic hazards.
This report is submitted by the Virginia Institute of
Marine Science, School .of Marine Science, College of William
and Mary under sponsorship of the U.S. Environmental Protection
Agency. This report covers the period July 1, 1978 to August
30, 1982.
Introduction
Each year, a substantial load of trace metals enters
Chesapeake Bay from both natural and human sources. Regional
production of toxic metals is increasing with increasing
industrial activity and sewage discharge. At least half of all
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Cd, Pb, Cu, and Cr reaching the Bay results from sewage and
industrial waste. Low concentrations of metals are essential
to Bay environment; however, if they are excessive, detrimental
consequences may result. Toxic effects have not been
demonstrated, but disturbing changes in the Bay environment
have been observed: a decrease in oyster and striped bass
populations, a lack of shad runs in the upper Bay, and
declining clam catches. Knowledge of contamination levels,
transport routes, and reservoirs of potential contaminants is
necessary because toxicants may alter the quality of the Bay
over periods of time.
This study investigates the role of suspended sediment and
fluid mud in the fate of toxic metals in the Chesapeake Bay
system. Fluid mud, an intermediate stage between mobile
suspended material and mud, is chemically important because it
is a reservoir for potentially toxic metals and a medium for
chemical transfer.
Procedure/Methodology
• A series of field observations defined the Bay-wide
distribution of metal contaminants in the following way:
suspended material was collected for analysis of toxic metals;
water in which they occur was characterized; and sediments with
which metals associate were analyzed for particle size and
physical properties. Temporal variations of sediment and metal
loading were established and potential zones of metal
accumulation and their transport routes identified. Field
observations included contrasting conditions such as seasonal
high-low river discharge and sediment influx, neap-spring tide
range, and oxygenated-anoxic water differences. The survey of
122 stations, with regard to these variables, along with the
parameters of temperature, salinity, dissolved oxygen, pH, and
total amounts of suspended material, resulted in 5576
measurements, including analyses of six to 11 metals.
Bed sediment and fluid mud were obtained with a stainless
steel Smith-MacIntyre grab or Bouma box core. Suspended
material collected on Nucleopore filters was analyzed by flame
atomic absorption for Fe, Mn, and Zn. Flameless atomic
absorption was used to obtain concentrations of As, Cd, Cu,
mercury (Hg), Ni, Pb, and Sn.
Results/Conclusions
The Bay was characterized from the hydrographic and
sedimentologic measurements and observations gathered from
eight cruises. The turbidity maximum zone (stations 12 to 18)
contains high suspended loads, fine particle size, and low
organic carbon percentages. Low suspended loads, coarse
particle size, and high organic percentages are common to the
central Bay zone (stations 8 to 11); while stations one to
seven, representing the near entrance reaches, have
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intermediate suspended loads, moderate particle size, and
moderate organic percentages. Conditions in the deeper
portions of the central Bay region favor accumulation of metals
and fluid mud because of fine-grained, moderately-organic
sediments which deposit rapidly.
Metal distributions in suspended material are vertically
stratified, with mean surface and mid-depth concentrations
greater than near-bottom depths. Cadmium, Cu, and Pb of
surface and mid-depth waters are three to 12 times higher in
summer than in spring. Concentrations of Cd, Cu, Pb, Ni, and
Zn are maximal in surface suspended matter from the central
Bay, suggesting bio-accumulation of metals from distant sources.
Bay water is well-buffered against pH change and is
oxygenated, except in summer when near bottom water of the
central Bay (below 10 m depth) is anoxic. Also, time, depth,
and distance seaward are conditions which affect physical,
chemical, and sedimentologic rates of transport and
accumulation of toxic materials.
Recommendations
By dealing with Chesapeake Bay as an entity, the state of
the Bay can be improved by reducing input of such potentially
toxic metals as Cd, Cu, Ni, Pb, and Zn from wastewater and
industrial discharges. Nutrients which stimulate organic
production should be reduced in an attempt to alleviate the
suspended solids load, of which some 40 to 60 percent is
composed of organic material. Entrapment of river-borne
sediment can be deterred by regulating inflows during periods
of high sediment influx.
Potentially toxic metals should be managed by controlling
them at their sources, by learning the long term changes and
"far field" effects in zones of accumulation, and by
recognizing amounts of toxicants in the system which are above
natural levels, as well as the associations between metals and
sediment. A monitoring system of the Bay and its tributaries,
with a scientific data base, should be established to warn Bay
managers of toxic hazards. Research should consider such
factors as bio-accumulation of toxicants in plankton, the
significance of repetitive sediment resuspensions, and the
tributaries as sinks or sources of metals and sediments.
-By Debra A. Barker
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Dredging: Implementation of Innovative Dredging Techniques in
the Chesapeake Bay
Don V. Aurand and Alexandra Mamantov
The environmental effect of dredging and dredged material
disposal has been an issue in the Chesapeake Bay region for
some time. This report reviews eleven years of dredging
records for Federal projects, six years of dredging records for
private projects, current management programs, and scientific
literature to define current programs and their effectiveness.
Potential technological improvements are also described. A
series of recommendations for improving dredging practices in
Chesapeake Bay is provided.
It appears that current operations do not produce major
consequences on the ecology of the Bay. However, attention
should be given to future programs in order to ensure that the
quality of the Bay does not deteriorate. Specific suggestions
for possible improvements are: implementation of study
programs to more clearly define the chemical nature of the
sediments; better long-range planning with respect to disposal
options; comprehensive monitoring programs'to clarify long-term
impacts; use of incentive payments to encourage innovative
technologies; replacement of seasonal dredging restrictions by
turbidity standards; possible Federal ownership of a small,
pneumatic dredge for use in highly polluted areas; and repeal
or modification of those portions of the Jones Act affecting
importation of dredging equipment.
Introduction
Maryland, Virginia, and two Corps of Engineer's district
offices set performance standards and issue permits for both
new starts and maintenance dredging projects in Chesapeake
Bay. Individually, and in some cases through joint review
sessions, officials within the appropriate state and Corps
district offices evaluate private and Federal dredging
proposals for compliance with environmental guidelines and
procedural requirements established by State and Federal
legislation. Federal laws, including the Clean Water Act,
National Environmental Policy Act, and Resource Conservation
and Recovery Act, set minimum standards for evaluating dredging
proposals. States can establish requirements more stringent
than those authorized by Federal statute. Standards, permit
processing procedures, and project operational requirements
mandated by Maryland and Virginia differ. The two Corps
district offices also employ different procedures to review
dredging permit applications.
The environmental and economic effects of both private and
public dredging projects are major issues within the Chesapeake
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Bay region. The Bay is an important commercial fishery and
recreational area. It also contains two major commercial
ports, Baltimore and Norfolk, which together load approximately
90 percent of domestic coal exports, excluding the Great Lakes.
Coal exports in 1980 reached 92 million tons, a 39 percent
increase over 1979 shipments. The two Chesapeake Bay ports
were unable to expeditiously process shipments, and colliers
were forced to drop anchor and wait until dockage and loading
facilities were available. The coal industry projects that
export demand could rise to 280 million tons by the year 2000.
The industry maintains, however, that increased coal shipments
cannot be moved through Baltimore and Norfolk unless channels
and harborage facilities are expanded.
Harbor expansion, maintenance dredging, and private
dredging are viewed cautiously by Bay fishermen and
environmentalists for several reasons. Dredging itself results
in increased turbidity, which some view as detrimental to
fisheries. Dredged sediment disposal is also a major problem,
particularly in the northern portions of the Bay. Although
open water disposal was practiced in the past, concern over
turbidity and the disposal of sediments contaminated by toxic
pollutants has resulted in increased use of costly upland or
confined disposal.
This report, prepared for the Environmental Protection
Agency's Chesapeake Bay Program examines environmental,
economic, and procedural issues related to dredging that have
been raised in the Chesapeake Bay region. Dredging methods,
effects, specific program requirements, and permit processing
procedures are reviewed. The volume of dredging activity (both
private and public), types of equipment used domestically and
abroad, costs, and approaches for streamlining the permitting
process are also examined.
Procedure/Me thodology
Dredging records for the eleven years from 1970 to 1980 for
Federal projects, and for the six years from 1975 to 1980 for
private permits were examined at the Corps of Engineers
Baltimore and Norfolk district offices. Historic dredging
practices (equipment used), volume of material removed,
disposal method (open water, upland, or confined disposal),
project location, and project costs were determined. Federal
statutory requirements, state standards, and permitting
procedures were reviewed, and differences in processing
techniques used by the two Corps district offices and the two
states were described.
Domestic and foreign dredging equipment (importation of
foreign equipment is restricted by the Jones Act) were
examined. Equipment capabilities, design features, and
turbidity factors were evaluated.
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Resuits/Conclusions
The invesigators conclude that the overall environment of
Chesapeake Bay has not been adversely affected by past dredging
and disposal operations. They state, however, that concerns
over dredging and disposal of contaminated sediments are
legitimate and deserve special consideration.
Several options are presented, both technological and
managerial, that the investigators feel could help minimize
dredging costs — attributable to compliance with environmental
standards — and ease permit processing procedures without
increasing the risk of environmental degradation.
Other options include: repeal or modification of the Jones
Act to ease restrictions on importation of equipment
manufactured abroad; use of positioning equipment and silt
curtains to minimize turbidity; and increased use of pneumatic
dredges on small projects and on projects involving the removal
of contaminated sediments.
Options for improving management of dredging programs,
including measures that might streamline the permit review
process are: use of turbidity performance standards instead of
imposing seasonal moratoriums on dredging activity; chemical
and bioassay testing of sediments for toxic contaminants; use
of advanced treatment methods in confined disposal areas; and
revision of effluent standards for upland disposal areas.
Recommendations
The investigators recommend that state regulatory agencies
evaluate several of the above options and possibly modify their
dredging programs accordingly. Specifically, they suggest that
states attempt to eliminate uncertainty concerning the extent
of sediment contamination within their jurisdictions by
sampling and then developing advance plans for dredging and
disposing of contaminated sediments. They also recommend
existing policies requiring confined disposal be reevaluated
and justified. States should encourage dredging contractors to
use new, innovative equipment, but incentives instead of
requirements should be the basis of such encouragement. Also,
seasonal restrictions on dredging should be repealed and
replaced by turbidity standards.
Two recomendations are advanced for consideration by
Congress and the Corps of Engineers. Repeal of appropriate
portions of the Jones Act is advocated, and the investigators
suggest that the Corps of Engineers investigate the purchase of
advanced pneumatic dredging equipment for use on the east coast.
-By Stephen Katsanos
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SUBMERGED AQUATIC
VEGETAT-TOTV
Distribution and Abundance of Submerged Aquatic Vegetation
in the Lower Chesapeake Bay, Virginia . 39
Distribution of Submersed Vascular Plants, Chesapeake
Bay, Maryland 42
Distribution and Abundance of Waterfowl and Submerged
Aquatic Vegetation in Chesapeake Bay 45
The Biology arid Propagation of Eelgrass, Zostera marina,
in Chesapeake Bay 48
Sediment Suspension and Resuspension from Small Craft
Induced Turbulence 53
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Distribution and Abundance of Submerged Aquatic Vegetation in
the Lower Chesapeake Bay, Virginia
Robert J. Orth, Kenneth A. Moore, and Hayden H. Gordon
Aerial photography and surface information were employed to
delineate the distribution and abundance of submerged aquatic
vegetation (SAV) in the lower Chesapeake Bay and its
tributaries. Imagery of SAV determined from the aerial
photographs was transferred onto 31 topographic quadrangles
which represented over 8500 hectares of SAV. All information
from this 1978 mapping effort was entered into a computerized
data base.
The areas with the greatest concentration of SAV were
located along the western shore of the Bay between Back River
and York River; along the shoreline of Mobjack Bay; the shoal
area between Tangier and Smith Islands and east of Great Fox
Island; and behind the sand bars near Hungars and Cherrystone
Creeks. The oligohaline and freshwater regions were
essentially lacking SAV.
Analysis of 40 years of SAV historical data of six selected
sites in the lower Bay revealed reduced coverage and density in
the late 1930's (compared to coverage in 1970), an increase
from 1937 to 1970, and then a large loss between 1971 and 1974
at five of the six sites. The decline continued through 1978
when the lowest levels of SAV in 40 years were witnessed.
Introduction
Submerged aquatic vegetation (SAV) systems serve many
functional roles in the Chesapeake Bay ecosystem. Among these
are habitat for macroinvertebrates, protection from predators
for many species of juvenile fishes and crabs, and food for
herbivores which feed off the diverse epiphytic growth on SAV
blades. Submerged aquatic vegetation converts an otherwise
bare sand or mud bottom into a complicated vegetated community
that not only supports a varied animal population but also
serves as a very efficient "nutrient pump" that moves nutrients
from the sediment to the water column and vice versa. In
addition, these grass beds aid in the reduction of shoreline
erosion by absorbing wave energy due to the binding of the
sediment by the roots and leaves of the plants.
Chesapeake Bay supports extensive shoal areas that are
heavily vegetated with SAV. Historically, emphasis has been
placed on these areas due to their importance as food for
waterfowl. However, with the recent decline of SAV in the
1970's, their other important roles are now apparent. It is
clear that these areas are important to the well-being of the
Bay and must be properly managed. Proper management of SAV
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must begin not only with recognition of the importance of the
resource but also with knowledge of where the resource is
located and its abundance as well as the dynamics of the
system. Thus, the objective of this study was to define the
current distribution of SAV in the lower Chesapeake Bay and to
focus on any trends related to the dynamics of the system that
might exist in the historical records.
Procedure/Methodology
Aerial photography and field investigations were employed
to delineate the distribution and abundance of SAV in the lower
Chesapeake Bay. Aerial photographs were transferred onto
topographic quadrangles (1:24,000). Individual SAV beds were
measured and computed with an electronic planimeter and stored
in a computer data base. Four density categories were applied
to each bed: less than 10 percent cover, 10 to 40 percent
cover, 40 to 70 percent cover, and 70 to 100 percent cover.
Field investigations were done at numerous sites for species
composition, percent cover, and bottom sediment types.
Results/Conclusions
Thirty-one mylar USGS topographic quadrangles were produced
showing significant areas of SAV. Twenty-seven of these were
of mesohaline and polyhaline areas which were dominated by a
species mixture of Zostera marina and Ruppia maritima. The
remaining four depicted significant areas of SAV in oligohaline
and freshwater regions of the Potomac, Chickahominy, and James
Rivers.
The oligohaline and freshwater regions essentially lacked
SAV. Field investigations revealed mostly small areas of SAV
usually adjacent to tidal marshes. The mesohaline and
polyhaline regions of the largest rivers and creeks along the
Chesapeake Bay shoreline contained the greatest concentrations
of SAV. The most significant areas were: along the western
shore of the Bay between Back River and the York River; along
the shoreline of Mobjack Bay; throughout the shoal areas
between Tangier and Smith Islands and east of the Great Fox
Islands; and behind large protective sand bars near Hungars
Creek and Cherrystone Creek that are located along the Bay's
eastern shoreline.
The distribution of SAV species in tidal waters were
classified into three associations based on their co-occurence:
(1) eelgrass (Zostera marina) and widgeongrass (Ruppia
maritima) dominating mesohaline and polyhaline waters; (2)
pondweeds (Potamogeton spp) and pondweeds (Zannichellia
palustris) dominating oligohaline waters; and (3) the
freshwater species coontail (Ceratophyllum demersum). Species
diversity increased in an upstream direction.
Analysis of 40 years of historical SAV data for six
selected areas revealed changes in grass bed coverage. Five of
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the six sites, Mumfort Island and Jenkins Neck in the York, the
East River in Mobjack Bay, Parrott Island in the Rappahannock
River, and Fleets Bay, located between the Rappahannock and
Potomac Rivers, showed reduced coverage and density in the late
1930's, an increase from 1937 to 1970, and then the largest
loss between 1971 and 1974. Abundance of SAV at the sixth
site, Vaucluse Shores (at the mouth of Hungars Creek on the
eastern shore), has not changed so dramatically as the other
sites. Differences have been attributed to changes in the
physical features (sand bars and sand spits) in this area.
Decreases in SAV at the first five sites continued through 1978
when the distribution and abundance was the smallest observed
over the last 40 years.
Recommendations
Submerged aquatic vegetation communities are dynamic
systems that change annually and seasonally in abundance. At
present, much attention is directed to these systems because
they are in a reduced state of abundance.
Aerial photography should be taken under the constraints of
tidal height, sun angle, wind conditions, and other factors; at
altitudes of 3740 meters which allows direct comparison to the
standard topographic quadrangle (1:24,000); and during the
early summer to record maximum standing crop of the
vegetation. It is recommended that aerial photographs be
taken, at the minimum, on an annual basis. In addition,
because the oligohaline and freshwater regions have been shown
to have scattered small beds of SAV that are not evident from
the aerial photographs, it is recommended that further field
studies be done in these areas to provide an understanding of
the distribution, abundance, and resource value of the
vegetation.
-By Linda C. Davidson
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Distribution of Submersed Vascular Plants, Chesapeake Bay,
Maryland
Richard R. Anderson
This research was initiated with the overall objectives of
determining past and current (1978) distribution of submersed
aquatic vegetation (SAV) in Chesapeake Bay, Maryland, and to
formulate recommendations for future surveys with regard to
frequency and methodology.
Current distribution of SAV was determined through
interpretation of 1:24,000 scale black-and-white photographs
were obtained during the growing season. Field work was
conducted in all areas with the use of a seaplane.
Distribution of SAV was mapped on 1:24,000 U.S. Geological
Survey (USGS) topographic map mylars. Seventy seven maps were
produced. Of the 40 sheets with less than 10 hectares of
vegetation, 11 were north of the Chester/Magothy Rivers and 21
were south of the Choptank/Upper Patuxent Rivers to Smith
Island on the Eastern Shore. This indicates that, the
mid-portions of Chesapeake Bay were relatively healthy with
regard to distribution of submersed vegetation. This area of
the Bay also contained the highest diversity of submersed
vegetation.
Current diversity declined rapidly from eight types in the
mid-Bay to two to three species in the southern portion of the
Eastern Shore were Zannichellia palustris and Ruppia maritima
predominated. There were only a few small areas of Zostera
marina found in the lower Bay, those being in the South Marsh
Island area.
Past distribution of SAV was determined through
interpretation of archival photographs of varying scale and
type. Distribution from 1952 to 1978 at various times within
those years was plotted for three areas in the upper Bay.
These sites encompassed the Chester River area, the Eastern Bay
area, and one site on the western shore to include Salt Peter
and Seneca Creeks.
Of the three areas, the Chester River site had the most
usable photography. Trends in the Chester River area indicate
fluctuation in distribution of SAV with time. The "bloom" and
consequent decline of Myriophyllum spicatum over the whole Bay
may have accounted for some of this fluctuation. The 1972 data
show a decline in SAV, possibly from effects of a tropical
storm during June of that year. There was an encouraging
increase in distribution shown in the 1978 survey.
The Eastern Bay area site had very little data available
for ascertaining distribution, but there does appear to be a
downward trend from 1970 to 1978. The Salt Peter/Seneca Creek
area site was selected due to the presence of a thermal power
generating station which discharges heated water into Salt
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Peter Creek. Operation of this plant began in 1962. SAV
distribution data prior to 1960 and after beginning of
operations (1964) indicate a relatively stable situation. This
was, however, the time of Myriophyllum "blooms" and may mask
the absence of other more thermally sensitive species. There
also appears to be a slight downward trend in distribution from
1970 to 1978.
Recommendations for future SAV surveys include larger-
scale, color photography that would better define species
association in areas defined as "critical," at a frequency of
at least once every three years.
This report was submitted by The American University under
sponsorship of the U.S. Environmental Protection Agency, and
covers the period June 1, 1978 to January 31, 1980. Work was
completed as of September 30, 1979.
Introduction
Over the last ten years the Bay grass population of the
Chesapeake has declined dramatically. In an attempt to better
understand the trends in distribution and abundance of
submersed aquatic vegetation, aerial photography was used to
establish an SAV inventory of the Maryland portion of the Bay.
By interpreting these black and white photos, investigators
hoped to focus on species concentrations and to assess the
usefulness of photography for estimating past and future trends.
While SAV beds may seem bothersome to some boaters, their
importance to the Bay's ecosystem is seemingly limitless.
Grasses are a principal source of food for waterfowl and some
herbivorous fish species. SAV serves as a habitat for species
of copepods and molluscs and as a nursery or shelter area for
fishes and crabs. Grasses are the primary producers of
vegetative biomass: almost all of the above ground crop is
contributed to the detrital food chain. SAV has a wave-
dampening function that reduces shoreline erosion and allows
sediments to settle. Bay grasses also act as nutrient buffers
and seasonally-important sources of dissolved oxygen.
For these many reasons, this study was conducted to
determine past and current distributions of SAV, and to
formulate recommendations for future surveys.
Procedure/Methodology
During the summer of 1978, aerial photographs were taken of
the Bay shoreline where grasses are found. Fourteen percent of
the area could not be photographed due to military restrictions,
but field work was substituted. Field studies were also
conducted in other areas to verify photographic information and
to identify dominant species.
Information from the photographs was then transferred to 77
USGS Maps; 17 of the maps covered areas with no mappable
vegetation and 24 contained less than 10 hectares of grasses.
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To determine how distribution and abundance has changed over
time, archival photos dating from 1952 to 1978 were analyzed.
The Chester River area, the Eastern Bay area, and Salt Peter
and Seneca Creeks were chosen to indicate historical trends.
Resuits/Conclusions
In interpreting the photographic coverage of the Maryland
portion of the Bay, scientists determined that the mid-Chesa-
peake is relatively healthy in both diversity and abundance.
Archival photographs indicate that grasses in the Chester River
area increased until the 1960's, declined, and increased again
until a decline after a tropical storm in 1972. There seems to
be a trend of increased distribution in 1978.
Archival data for the Eastern Bay were too insignificant to
draw any meaningful conclusions. Salt Peter and Seneca Creeks
had a greater distribution of SAV than in the early 1970's but
there seems to be some stabilization in the 1978 survey.
Recommendations
The study suggests that broad SAV surveys should be
initiated every three years to record and predict trends.
Yearly monitoring of regionally-representative areas should be
more complete, including species composition, percentage cover,
and seasonal growth characteristics. Color photography should
be used as it enhances species distinctions. Lab and field
studies should continue so that light, temperature, and other
factors which control the survival of SAV can be determined.
-By Debra A. Barker
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Distribution and Abundance of Waterfowl and Submerged Aquatic
Vegetation in Chesapeake Bay
Robert E. Munro and Matthew C. Perry
Waterfowl populations in Maryland and Virginia portions of
Chesapeake Bay were examined during long-term (1890-1970) and
current (1972-1980) periods to identify trends in their
distribution and abundance. Comparisons were also made between
State and Atlantic Flyway populations and waterfowl species
distributions among survey areas. Distribution and abundance
of submerged aquatic vegetation (SAV) among waterfowl survey
areas in Maryland were summarized for seven plant species
during nine years (1971-1979). These data (SAV species
combined) were used to test the hypothesis that annual
variation in area populations of waterfowl was related to
variation in the abundance of SAV, following an adjustment for
annual variation in the general abundance of waterfowl. The
distribution and abundance of SAV species declined in Maryland
waters during the 1970"s. There were few statistically
significant relationships between distribution and abundance of
waterfowl and SAV. But there was an implied biological
relationship, because the most important waterfowl wintering
areas were also among the most abundantly vegetated areas.
This report was submitted by the U.S. Fish and Wildlife
Service, Migratory Bird and Habitat Research Laboratory under
the sponsorship of the Chesapeake Bay Program, U=S=
Environmental Protection Agency.
Introduction
The Chesapeake Bay is the most important wintering area in
the Atlantic Flyway for more than 1.5 million waterfowl,
including Canada geese (Branta canadensis), whistling swans
(Cygnus columbianus columbianus), canvasbacks (Aythya
valisineria), ruddy ducks (Oxyura jamaicensis), common
goldeneyes (Bucephala clangula americana), redheads (Aythya
americana), black ducks (Anas rubripes), and mallards (Anas
platyrhynchos). The estuary also serves as a resting area for
birds that migrate farther south. Of the 45 species native to
North America, 30 migrate through or winter in Chesapeake Bay.
Large beds of submerged aquatic vegetation, especially
widgeongrass (Ruppia maritima), wild celery (Vallisneria
americana), and sago pondweed (Potamogeton pectinatus),. have
traditionally been important to the Bay's population of
waterfowl. The decline of the grasses, a major source of food
for the birds, prompted this examination of historic and
current relationships between waterfowl and SAV.
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Procedure/Methodology
The U.S. Fish and Wildlife Service (USFWS) conducts annual
population surveys of Chesapeake Bay waterfowl. Although
information may be affected by weather conditions, and by birds
not found, and those found but not counted, these surveys
constitute the only long-term source of information on
waterfowl distribution and abundance. These surveys were
analyzed so that population comparisons between pre-1970
(long-term) and 1972-1980 (current) periods could be made.
United States populations were used as baseline measures to
indicate species trends. Species had to compose at least five
percent of the Atlantic Flyway population to be considered in
this study.
Waterfowl feeding habits were tabulated according to
species, time period (pre-1960, 1960's, and 1970's), and organ
source (gizzard, gullet, or unknown). This information,
collected by Stewart during the 1950's, Rawls during the
1960's, and supplemented with current data, provided the
information necessary to examine relationships between
waterfowl and SAV as a food source.
Distribution and abundance records of SAV, taken from
results of summer surveys conducted by the USFWS and Maryland
Wildlife Administration during 1971-1979, were studie.d to
determine the trends of SAV populations. Linear regression and
analysis of variance techniques were used to examine
relationships between waterfowl and SAV.
Results/Conclusions
Reductions in SAV populations affected the distribution and
abundance of waterfowl species that were historically dependent
on SAV and could not adapt to the changes. Some species left
the area while others changed their feeding habits.
The SAV population as a whole declined dramatically in the
1970's. Vegetated sample stations in Maryland waters declined
from approximately 29 percent during 1971 to 8 to 15 percent
since 1973. Important waterfowl food plants, which were
abundant during the late 1960's, became less prevalent in the
Bay by 1973. Examples include widgeongrass, sago pondweed,
horned pondweed, and wild celery.
Over 600 sampling stations of shoal water habitats were
established to monitor these trends in Bay grass populations
among waterfowl survey areas for nine years. By 1979 each of
the 20 areas had depleted supplies of SAV. The lower Choptank
River, for example, had 25.5 percent of its stations vegetated
in 1971. By 1979, however, this total fell to 12.8 percent.
Eastern Bay, another important wintering area for waterfowl,
fell from 21.4 percent in 1971 to 11.1 percent in 1979.
Widgeongrass, the most important food item of wigeon and
black ducks, was the most abundant and widely distributed
species in each of nine annual surveys. Low populations of
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wigeon, pintails, and redheads, predominantly vegetarian in
nature, were correlated with the overall decline of SAV.
Diving ducks, including canvasbacks and redheads, were most
affected by the SAV decline. Diving ducks have small wings and
legs set back on their bodies, making walking difficult. They
need water to run across prior to flight and are thus unable to
feed in dense marshes or agricultural fields. Redhead
populations, which subsist on SAV, declined in numbers.
Apparently they could not change their diets and exist in an
area with reduced SAV populations. Canvasbacks, on the other
hand, incorporated Baltic clams (Macoma spp) and other
invertebrates into their diets, and therefore remain as
important members 'of the Bay's wintering waterfowl population.
Puddle ducks, which feed by dabbling at the water's
surface, were historically more dependent on vegetation.
Puddle duck populations, as a group, are presently at one third
their former level. Pintail and wigeon populations are now
nearly absent from Maryland wintering areas. Other puddle
ducks, such as black ducks and mallards, have also decreased.
Whistling swans survived the decline of SAV by foraging on
the land. This species now depends more on the availability of
unharvested cereal grains from agricultural fields than on
SAV. The population of Canada geese continued a long-term
increase in numbers during the 1970's. Like swans, Canada
geese rely on cereal grains from fields around the Bay.
Recommendations
The declining numbers of waterfowl that winter in
Chesapeake Bay are cause for concern. Biological links exist
between abundance of grasses and certain waterfowl populations
in the Bay, so that decreases in distribution and abundance of
SAV can directly affect certain species of waterfowl. Recovery
of SAV resources will encourage the return of SAV-dependent
waterfowl that annually migrate through the area. Scientists
should continue to study factors leading to the declension of
SAV and how such changes affect other aspects of the Bay
ecosystem.
-By Debra A. Barker
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The Biology and Propagation of Eelgrass, Zostera Marina, in
Chesapeake Bay
Robert J. Orth and Kenneth A. Moore
Basic biological aspects related to the growth and
propagation of eelgrass in the lower Chesapeake Bay were
studied in a series of six experiments designed to reveal
information on seasonal aspects of standing crops,
reproduction, transplanting and spontaneous revegetation in
denuded areas, and growth of eelgrass seedlings under
laboratory conditions of increased nutrient enrichment.
Data analysis revealed distinct seasonal trends in the
growth cycle of eelgrass. Transplantation of eelgrass plugs in
the fall insures greater survivability than doing so in other
seasons. The primary method of revegetation by Ruppia sp. and
Zostera sp. seems to be by lateral growth from adjacent
unimpacted areas, although seed germination and subsequent
seedling growth may be significant in certain areas. The
addition of a balanced formulation of fertilizer stimulates the
growth of eelgrass under laboratory conditions.
Introduction
Chesapeake Bay eelgrass beds are a valuable natural
resource which .provide a habitat for large numbers of
macroinvertebrates, food for migrating waterfowl, and shelter
for juvenile fishes and blue crabs. In addition, grass beds
aid in the reduction of shoreline erosion by absorbing wave
energy and serving as a sediment trap. Its contribution to the
detrital food chain is also significant.
The recent (1970's) disappearance of eelgrass beds in the
lower Bay has prompted an interest in replanting. Studies have
shown that revegetation under favorable conditions is feasible
but some problems still exist due to a lack of knowledge
related to eelgrass biology. With this in mind, the six
experiments in this study were designed.
I. Seasonal Aspects in the Standing Crop of Eelgrass Beds
Procedure/Methodology
Seasonal changes were observed in three study sites in the
lower main Bay for changes in standing crop and to aid in the
description of the reproductive biology of eelgrass:
a) near the mouth of Browns Bay in Mobjack Bay;
b) adjacent to the Guinea Marshes at the mouth of the
York River; and at
c) Vaucluse Shore at the mouth of Hungars Creek on the
Eastern Shore.
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From June 1978 through June 1979, monthly ring samples were
taken at each site. A 0.1 m2 ring was placed on the bottom
and all vegetation, including the roots and rhizomes, to a
depth of about. 10 cm was removed. Beginning in June 1979, core
samples were taken as well. A comparison of the two procedures
revealed little differences. Six core samples were taken at
each site until January 1980 when sampling was reduced to three
cores. Sample analysis yielded information on the number of
vegetative and reproductive shoots per meter squared (m2)}
mean length of shoots, biomass of the leaf, and root and
rhizome fractions per m2. Temperature and salinity
measurements, as well as sediment samples, were taken at each
site.
From November 1979 to May 1980 monthly seedling samples
were taken at the Guinea Marsh in-shore area. These were
analyzed for maximum length of the primary leaf, and the number
of shoots and leaves per seedling.
Resuits/Conclusions
Each of the three sites showed similar trends for maximum
and minimum values of parameters such as shoot biomass, shoot
density, and number of reproductive shoots. The period of
maximum biomass for vegetative shoots was in summer with the
minimum occurring in the fall or winter months. However, there
was a difference in the maximum biomass of the two years with
1980 showing a higher volume than 1979. This fact seems to
indicate the presence of some enviromental control (e.g.,
temperature) or biological control (waterfowl interactions)
that affects all grass beds and can vary from year to year.
Appearance and growth of new shoots occurred after
mid-August and continued to be produced throughout the winter
and spring. Measurements of mean length of shoots showed a
distinct trend for all sites. Peak length occured in June-July
for all sites except Vaucluse Shore which had peak length in
May, possibly as a result of temperatures rising faster in this
more shallow area.
Some differences existed as to the number of seedlings
observed at each site. This is probably due not only to seed
production differences within a particular area but also to
possible seed dispersal from other areas.
II. Anthesis and Seed Production in Zostera marina L
Procedure/Methodology
Random samples were taken at seven to 10 day intervals from
March 11, 1980 to May 28, 1980 at three sites to describe the
timing involved in the flowering process of eelgrass. A subset
of samples was taken beginning in January, 1980 in order to
ascertain the beginning of the flowering period. Samples were
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analyzed for the number of vegetative and reproductive shoots,
length, number and position of spadices per shoot; and number
and size ranges of anthers and pistils within each spadix.
Results/Conclusions
Reproductive shoots were first observed in February 1980.
Pollen release was first observed April 10, 1980 when the
average water temperature was 14.3°C, and was completed at
all stations by May 19, 1980. By May 28 the fruiting process
was at full maturity. The period from pollen release to
initial seed development and release was 28 days. This process
begins and ends one month earlier in lower Chesapeake Bay than
in areas further north.
III. Seed Germination of Eelgrass in the Lower Chesapeake Bay
Procedure/Methodology
Reproductive shoots of eelgrass were examined at nine
stations weekly beginning in late April 1979 to identify the
timing of eelgrass seed germination.
Results/Conclusions
Seed germination occurred every month except July and
August when temperatures were too high for germination. The
major period of seed germination occurred between November 1
and March 31 when water temperatures did not exceed 10°C.
Storage of seeds at temperatures above 15 °C will prevent
germination but may result in rotting. The data collected
implies that low temperature, rather than salinity, may be the
primary cause for seed germination. There does not seem to be
a dormant period between seed release and germination.
The rate of seed germination varied from site to site. It
was implied that these differences may be the result of subtle
environmental differences such as runoff, temperature
differences, or depth at which seeds are buried in the
sediments.
IV. Tranplantation of Eelgrass into Recently Denuded Areas
Procedure/Methodology
Plants were removed from an established bed at the Guinea
Marsh area and transplanted at a site near Mumfort Island in
the York River. The Mumfort Island area was selected because
it had been the site of extensive eelgrass beds but was now
devoid of Zostera. In addition, it was fairly isolated and
would probably not be disturbed by people.
Transplanting done by two different methods (plugs and
mats) began in March 1979. A second transplanting effort was
done in early June, a third in September and October, and a
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fourth in April 1980. Four additional sites were used in the
transplanting effort during the last three experiments:
Gloucester Point, Aliens Island, Guinea Marsh in the York
River, and Parrott Island in the Rapphannock River. Fertilizer
was used in some transplants to assess the effect on success
rate.
Resuits/Conclusions
A comparison of the two methods of transplanting indicates
that the use of plugs is the better management option for
mitigation mainly because it works better than the mat method,
especially in more wave exposed areas where it costs far less
and some anchoring mechanism is necessary.
Success of the transplants depended on the season of
planting (fall was best and summer had the least success) and
location. Downriver sites (Guinea Marsh, Aliens Island, and
Gloucester Point) had highest success compared to the upriver
site (Mumfort Island). High temperatures and high reduction in
available light (especially at the Mumfort Island site) make
summer the least desirable time for transplanting. Sites
chosen for transplants should have previously supported
Zostera. Better growth results were obtained when Osmocote
fertilizers (14-14-14) were used in spring 1980 transplants at
Aliens Island.
V. Regrowth of Submerged Vegetation into a Recently Denuded
Boat Track
Procedure/Methodology
Monthly observations were made on a denuded one-meter
square plot, within a boat track, to determine the percent of
revegetation, regrowth patterns, and seedling recolonization.
Sediment samples analyzed for particle grain size and
interstitial nutrients were taken from this plot and an
unimpacted vegetated area.
The entire length of the boat track was also observed
monthly to determine revegetation patterns, effects of scouring
or bioturbation, and any changes in orientation of cut. In
addition, temperature, salinity, and PAR light readings were
taken.
Re suits/Conclusions
Revegetation by Ruppia and Zostera occurred primarily as
lateral growth from adjacent unimpacted areas. Ruppia seems to
recolonize more rapidly than Zostera. After seven months
Ruppia had spread over less than half of the denuded area. It
appears that at least two seasons of growth are required for
Ruppia recolonization, and possibly three for Zostera.
Analysis of the sediments reveals them to be fairly homogeneous
to depths of about 20 cm, probably due to active bioturbation.
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No significant difference existed for interstitial nutrients
inside or outside the.denuded area.
VI. Growth of Eelgrass Seedlings Under Laboratory Conditions
of Increased Nutrient Enrichment
Procedure/Methodology
Seedlings were collected from a grass bed at the Guinea
Marsh site on the York River and placed in peat pots containing
soil from the same site. Peat pots were placed in greenhouse
holding tanks receiving flowing estuarine water from the York
River and about fifty percent incident light at the water
surface. Two formulations of Osmocote fertilizer were applied
at three different dosages. Number of shoots, leaf blades per
shoot, and length of the longest blade on the oldest shoot were
recorded at two week intervals from March 20, 1980 to June 13,
1980.
Re suits/Conclusions
Growth by way of increased leaf length and vegetative
production of increased number of shoots is stimulated by
addition of fertilizer. The balanced formulation (14:14:14)
produced better results in increased leaf length than the
nitrogen rich formulation (18:6:12). Sixty percent of the
fertilized plants exhibited three or more shoots per plant as
compared to only four percent of the controls.
Recommendations
Prior to 1978 little was know about the basic biology of
eelgrass. This study, while answering some questions about
eelgrass biology, discovered many others which could not be
answered. Several questions that should be addressed in future
studies are: (1) what controls maximum production of eelgrass
in a particular area; (2) what are the reasons for annual
difference in shoot production and biomass; (3) what are the
temperature and salinity effects on seed germination; and (4)
what are the effects of fluctuating temperatures on seed
storage.
-By Linda C. Davidson
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Sediment Suspension and Resuspension from Small Craft Induced
Turbulence
Hermann Gucinski
The objective of this study was to determine if small
vessels operating in shallow waters have any measurable effects
in producing increased turbidities by the resuspension of fine
sediments that may affect submerged aquatic vegetation (SAV).
A two-phase approach was used, consisting of field tests in
a suitable sub-estuary of Chesapeake Bay and laboratory
measurements of propeller effects. During field trials, two
different vessel types were used to make passes at set speeds
over known water depths. Measurements of light extinction,
transmission,.and suspended sediment were made before and after
boat wake and propeller disturbance. Laboratory experiments
were conducted to delineate propeller contribution to possible
resuspension; this was done using laser-doppler anemometry to
map the turbulence field produced by propeller action.
This report was submitted by Anne Arundel Community College
and the U.S. Naval Academy under the sponsorship of the U.S.
Environmental Protection Agency's Chesapeake Bay Program.
Introduction
Causative factors for the widespread disappearance of SAV
in the Chesapeake Bay, beginning in the early seventies, have
been the subject of intense study. Many mechanisms have been
hypothesized to explain this disappearance, including increased
sediment loads caused by hurricane-produced runoff, the
increasing reliance placed on herbicides in farm operations,
nonpoint source pollution resulting from heavy development
pressures in the coastal zone, and increased turbidities from
increased use of Bay waters and tributaries by recreational
watercraft. No one single factor appears to be responsible for
the stresses causing reduction in SAV growth, but each
mechanism needs investigation to find the most significant, or
any synergistic effects of several interacting processes.
Small vessels operating in shallow waters, or with their
wakes reaching shallow waters, may have measurable effects in
producing increased turbidities by the resuspension of
sediments. The time required for the sediment to settle out of
the water column depends on particle size, the presence of
background turbulence, and motion that may retard the settling
rate and produce significant lateral transport of the
resuspended sediment.
The disturbance may affect rooted SAV if the erosive forces
are great enough to displace organic detritus and inorganic
silts and muds normally stabilized by the rooted plants.
Direct damage to the root may result. If the resuspended
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particles are small and have long settling times, then they can
contribute to increased light extinction in the water column,
possibly reducing the photosynthetic rate of SAV. Sediments
may also settle onto the leaf structures of the plants and
further reduce photosynthesis and respiration, thereby limiting
productivity and stressing the bed further.
Laboratory studies and empirical field studies were used to
assess variables such as depth to which effects can be felt,
the relative magnitude of the suspension, and possible impact
(of a biological nature) of propeller-generated sediment
resuspension.
Procedure/Methodology
Field trials were made at three sites having reasonably
uniform water depths, minimum variation of bottom sediments
with a high percentage of small-sediment particles ( <. 60 u),
and availability of prior data on natural changes in suspended
sediments.
Using two vessels, a 6.7-meter speedboat, and a nine-meter
tugboat, passes at set speeds, chosen for maximum wave-making,
were made along a series of buoys at each site. Before and
after light extinction, transmission measurements, and water
samples were obtained for gravimetric determination of
suspended sediments.
Laboratory experiments, which measured water particle
motion from the effect of a boat propeller, were conducted to
predict the distribution of stresses sufficient for sediment
resuspension.
Resuits/Conclusions
The resuspension of fine sediments in the path of a small
craft is influenced by water depth, depth of immersion, size of
the propeller, the advance ratio, and the wave-making tendency
of the vessel. The depth to which stirring is sufficient
appears to be quite limited. In this study, at depths of
greater than 2 meters, reduction in SAV productivity was
calculated at about 1 percent for small displacement craft of
less than 9000 kg and 130 hp.
Light extinction measurements give the most statistically
reliable and consistent results. They also show a
correspondence to the laboratory results, thereby allowing
formulation of a tentative hypothesis concerning the most
significant variables that affect sediment resuspension.
Transmissionmeter readings, taken concurrently with
photometer measurements, corroborate measurements of light
extinction coefficients. The relatively lesser effects of the
boat having the least propeller immersion is apparent, and is
borne out by statistical comparison.
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The gravimetric determination of suspended sediments was
less statistically significant but does follow the pattern
established by the photometer results.
However, the depths to which boating effects allow sediment
resuspension coincide with depths where SAV growth is limited
in Bay waters. Comparison of SAV maps suggests that areas of
least SAV distribution and slowest recovery are also areas of
greatest boating congestion. No conclusive studies have been
done on this correlation. Sandy sediments predominate close to
shore in waters less than 2.5 meters deep, and fine clay-like
silts and muds are ubiquitous in deeper waters. Such
distribution may have a protective effect for SAV beds in high
wave/wake energy environments.
Recommendations
It is tentatively recommended that ecologically sensitive
areas be investigated for the presence of fine sediments «^ 60
u). Such areas should be protected from excessive traffic,
particularly deep-draft, high-powered displacement craft.
-By Judy Broersma
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TABLES OF WEIGHTS AND MEASURES
LENGTH
English
1 inch (in) = 2. 540 centimeters
1 inch (in)"= 25.40 millimeters
1 foot (ft) = .305 meter
Metric
1 centimeter (cm) = .394 inch
1 millimeter (mm) = .0394 inch
1 meter (m) = 3.281 feet
AREA
1 square foot = 0.093 square meter 1 sq. meter = 10.764 square feet
(ft2) (m2)
1 square mile = 2.590 sq. kilometers 1 sq. kilometer = 0.386 sq. miles
(mi2) (km2)
1 acre (a) = 0.404 hectare 1 hectare (ha) = 2.471 acres
1 gallon (gal) = 3.785 liters
1 cubic foot/sec = .0283 rn^/sec
VOLUME
1 liter (1) = 0.264 gallon (U.S.)
VELOCITY
1 cu. meter/sec = 35.315 ft^/sec
(m3/sec)
TEMPERATURE
degrees Farenheit = 9/5 (°C) + 32 degrees Celsius = 5/9(°F - 32)
MASS
1 ounce = 28,350 milligrams
(oz)
1 ounce = 28.350 grams
1 pound = 0.454 kilograms
1 milligram = 0.0000353 ounces
(mg)
1 gram = 0.0353 ounces
(g)
1 kilogram = 2.205 pounds
(kg)
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PRINCIPAL INVESTIGATORS
Anderson, Gary F.
Virginia Institute of Marine Science
Gloucester Point, VA 23062
Anderson, Richard R.
The American University
• Washington, DC 20016
Aurand, Don
The MITRE Corporation
Metrek Division
1820 Dolley Madison Blvd.
McLean, VA 22102
Capper, John
Maryland Environmental Trust
501 St. Paul Place, Suite 1401
Baltimore, MD 21202
Gucinski, Hermann
Anne Arundel Community College
Environmental Center
Arnold, MD 21012
Heinle, Donald R.
University of Maryland
Center for Environmental & Estuarine Studies
Chesapeake Biological Laboratory
Solomons, MD 20688
Kingston, Howard M.
Center for Analytical Chemistry
National Bureau of Standards
Washington, DC 20234
Lang, David J.
U.S. Geological Survey
208 Carroll Bldg.
8600 LaSalle Road
Towson, MD 21204
Munro, Robert E.
U.S. Fish and Wildlife Service.
Migratory Bird and Habitat Research Laboratory
Laurel, MD 20811
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Nichols, Maynard
Virginia Institute of Marine Science
Gloucester Point, VA 23062
Orth, Robert J.
Virginia Institute of Marine Science
Gloucester Point, VA 23062
Weand, Barren
Occoquan Watershed Monitoring Laboratory
Department of Civil Engineering
Virginia Polytechnic Institute and State University
P.O. Box 784
Manassas, VA 22111
lii §
at O
III 8
O Q. S LU
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REPORTS TO BE INCLUDED IN FINAL EDITION
NUTRIENTS
Effects of Specific Land Uses on Nonpoint Sources:
Pequea Creek Basin, 1979-1980 (Patricia L. Lietman)
Patuxent River Intensive Watershed Study (Charles Bostater)
Chesapeake Bay Nutrient Dynamics (Jay Taft)
Modeling Study (John P. Hartigan)
TOXIC SUBSTANCES
Physical Characteristics and Sediment Budget for Bottom
Sediments in the Maryland Portion of Chesapeake Bay
(Randall Kerhin)
Animal/Sediment Relationships (Eli Reinharz)
Chesapeake Bay Sediment Trace Elements (G.R. Helz)
The Biogenic Structure of Lower Chesapeake Bay Sediments
(R.J. Diaz)
Interstitial Water Chemistry (James Hill)
Investigation of Organic Pollutants in Chesapeake Bay
(Robert Huggett)
Toxic Point Source Assessment of Industrial Discharges
(Gary Rawlings)
Interpretation of Toxic Substances in the Water Column
(Howard Kingston)
Baseline Sediment Studies to Determine Distribution,
Physical Properties, Sedimentation Budgets and Rates in
the Virginia Portion of the Chesapeake Bay (Robert Byrne)
SUBMERGED AQUATIC VEGETATION
Interactive Studies of Light, Epiphytes, and Grazers
(Robert Orth)
Changes in the Chesapeake Bay as Recorded in the Sediments
(Grace Brush)
Propagation and Impact of Herbicides on Submerged Aquatic
Vegetation (Carl Hershner)
Functional Ecology of Submerged Aquatic Vegetation
(Richard Wetzel)
Submerged Aquatic Vegetation in Chesapeake Bay - Its Role
in the Bay Ecosystem and Factors Leading to Its Decline
(Michael Kemp)
ENVIRONMENTAL MANAGEMENT
Review of Regional Water Quality Control (Environmental Law
Institute)
Evaluation of Institutional Arrangements (Resources for the
Future)
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