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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Chesapeake Bay Program
2083 West Street -Suite 5G
Annapolis, Maryland 21401
301-266-0077
FTS-922-3912
To All Interested Citizens, Legislators,
Administrators and Researchers:
Enclosed are the first three Brief-Summary Report packages of the
Chesapeake Bay Program's Information Series, a set of publications
describing findings, observations and management implications of
research sponsored by the Chesapeake Bay Program.
The Briefs and Summaries cover the three areas in which the Chesapeake
Bay Program sponsors research—Bay Grasses, Nutrients and Toxics. The
headings on the reports are colored differently for each area—Green for
Bay Grasses, Blue for Nutrients and Rust for Toxics. There will be
several reports under each area; they are numbered at the top right
hand corner of the reports. In this mailing, you have the first two
reports under the Toxics area, and one in the Bay Grasses area. The
notebook we have provided is for your use in storing the reports.
You will be receiving both the Briefs and Summaries throughout the
remainder of the Chesapeake Bay Program. The Briefs are short, simplified
descriptions of Chesapeake Bay Program research, designed to make the
reader quickly aware of the general contents of that particular project.
The Summaries go further, giving more detailed and technical explanations
of the various projects. Through both types we hope to keep you
informed of our research results and their importance to the health of the
Chesapeake Bay.
If you have any comments regarding the Briefs and Summaries, please do not
hesitate to contact Elizabeth Macalaster at the Chesapeake Bay Program in
Annapolis. We want to communicate this material in the best way possible
and appreciate any suggestions.
Tudor T. Davies
Director,
Chesapeake Bay Program
TTD/jfl
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EPA SAV
Chesapeake Distribution and Abundance
Bay Program
Information July 1980
Series
In Search of Bay Grasses
Scientists refer to them collectively
as submerged aquatic vegetation,, SAV,
for short„
Eight types of these grasses grow in
the shallower waters of the Chesapeake
Bay. To the casual observer, they may
appear to be inconsequential, or even
a nuisance. But, to fish, crabs, and
waterfowl, they axe food, shelter, and
nursery—the essentials of life itself„
Since 1972, Bay grasses have been de-
clining dramatically in distribution
and number,, And no one knows why.
One of the many objectives of the
EPA's Chesapeake Bay Program Submerged
Aquatic Vegetation Program is to find
out what is causing this decline,,
Two of Many Studies
To determine the distribution and
abundance of these grasses, companion
studies were started in 1978: one,
covering the Maryland portion of the
Bay, under Dr„ Richard R. Anderson, of
the American University, in Washington,
D.C.j the other, covering the lower
part of the Bay, under Dr0 Robert J.
Orth, of the Virginia Institute of
Marine Science, Gloucester Point, Vir-
ginia,,*
These are just two of thirty-nine
studies involving hundreds of scien-
tists engaged in research for the
Chesapeake Bay Program„
Grass Roots Census
Both groups set out to determine what
grasses are growing where, how abun-
dant they are, and how their patterns
of growth have changed„
Archival aerial photographs provided
clues to the pasta
To determine the present status of SAV
distribution and abundance, teams of
scientists took aerial photographs
from all over the Bay and mapped their
findings. They then analyzed the maps
and compared them with historical
photographs dating back to about 19^0.
As a result, there is now much more
information concerning the distribu-
tion and abundance of these important
grasseso This information is available
to everyone concerned about the Bay
and its future„
The greatest distribution and abun-
dance of submerged grasses in Maryland
occur in the area around the Chester
River and Eastern Bay. Only marginal
distributions of grasses were found on
the Western Shore from Baltimore Har-
bor to Herring Bay, in the Choptank
River system, and along the lower
Eastern Shore« And almost no grasses
were found in the Patuxent and lower
Potomac Rivers or in the upper part
of the Bayu
In Virginia, Bay grasses were found
mainly at the mouths of the major riv-
ers and along the eastern and western
"Two follow-up studies were conducted In the upper and lower Bay in 1979i but results are not yet available.
-------
Pennsylvania
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shorelineso In the tributaries, small
grass beds were found along certain
sections of the Potomac River and
Chickahominy River,
Field studies also provided useful in-
formation on the diversity and density
of Bay grasses, as well as associa-
tions of the various species, which
were found to vary with the depth and
salinity of the water,,
Now What?
What does it all mean?
Already, copies of maps produced by
these studies have been distributed to
Maryland and Virginia resource manage-
ment agencies, which will use them in
reviewing applications for dredging
and disposal permits. The purpose is
to avoid disturbing established com-
munities of grasses.
Beyond that, while it is clear from
archival photographs that Bay grasses
have been disappearing in almost all
areas for at least ten years, it is
not clear how long or to what extent
this trend will continue. Nor are the
reasons for the decline yet clear. By
correlating the findings of these
studies with those of others in the
Chesapeake Bay Program, scientists
hope to be able to predict patterns of
change and recommend ways of prevent-
ing further damage to the delicate
ecosystem we call the Chesapeake Bay.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency»
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
For more information, contacts
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
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EPA
Chesapeake
Bay Program
Information
Series
Too Much of a Good Thing
Nutrients—phosphorus, nitrogen,
carbon—are necessary for plants and
animals to grow. In the Chesapeake
Bay, nutrients exist naturally, but
human-related activities, including
agricultural and urban runoff,
sewage discharge and septic tank
leakage, are adding more and more of
these elements. When too many nu-
trients enter the Bay they cause
overenrichment of the water, be-
coming harmful, ratner than
nourishing to Bay life.
Over the Falls
To learn how nutrients are affecting
the water quality of the Bay, the
U.S. Environmental Protection
Agency's Chesapeake Bay Program is
calculating nutrient loadings, the
total amounts of nutrients carried
by water entering the tidal Bay. In
one study conducted by the U.S.
Geological Survey, scientists are
looking at amounts of nutrients
flowing past fall lines of the
James, Potomac and Susquehanna
Rivers. The fall lines of these
rivers are areas where the Piedmont
Province and Coastal Plain meet.
Waterfalls often exist at fall
lines, and the tide's effects end
here.
The scientists picked these rivers
because they are the Bay's largest
tributaries and contribute over 85%
of the estuary's freshwater. Thus,
Nutrients
Fall Line
Nutrient Studies
January 1981
most of the nutrients entering the
Bay from human-related sources come
via these rivers.
Three River Sampling
The Geological Survey scientists
collect water samples from the three
rivers at sites shown in Figure 1.
inowingo
\ Dam
Carti
Figure 1. Fall Line Sampling Sites.
For deep-water samples, they use a
torpedo-shaped container which faces
the river current and continually
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collects samples as it is lowered
from the surface to the bottom and
raised back to the surface again.
For shallower and slow-flowing
stream reaches, the scientists use a
brabi or steel, weighted bottle.
Figure 2. shows a researcher
collecting water samples from a
bridge. The truck in the photo-
graph is equipped with a small
laboratory, allowing the scientists
to process their samples on location.
Figure 2. U.S. Geological Survey researcher samples from
a bridge using a specially built crane.
Chemical analyses of water samples
give the scientists concentrations
of nutrients flowing past the river
fall lines. This information
together with measurements on flow
rate give total amounts of the
nutrients over a day or year.
The scientists have also devised a
more cost-effective sampling
method. Some nutrients the scien-
tists measure correlate well with
stream flow, suspended sediments or
electrical conductivity. The
ability to correlate a nutrient
concentration, say of phosphorus,
with a physical factor such as
stream flow saves scientists time
and money, because they need only
measure stream flow to obtain a good
estimate of the concentrations of
phosphorus. Thus, they avoid the
time and expense involved in
analyzing their samples.
Good Nutrition
Results from the fall line research
will provide information on sources,
quantities and kinds of nutrients
flowing to the Chesapeake Bay. The
Susquehanna, Potomac and James
Rivers are the major sources of
freshwater to the Bay. Therefore,
assessing nutrients coming
from these tributaries will help
scientists assess levels of enrich-
ment in the Bay and how to control
them. The Bay Program's mathe-
matical models will, in turn, help
managers determine how many
nutrients should travel across the
fall lines to maintain or improve
certain water quality conditions.
Thus, Bay life will be assured of
receiving the right amounts of
nourishment.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U.S. Environmental Protection Agency.
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21^01
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Author: Elizabeth Macalaster, Editor: Greg McGinty, Editorial Assistant: Dottie Van Doren
-------
EPA
Chesapeake
Bay Program
Information
Series
Sedimental Journeys
The Chesapeake Bay is gradually get-
ting wider and shallower, largely
because of erosion and the deposit of
fine-grain sediments.
The characteristic combination of a
net inward flow of water in the lower
layer and a net outward or seaward
flow near the surface makes this estu-
ary a natural sediment trap.
Not so natural, however, is the addi-
tion of toxic chemicals. Their trans-
port and deposition can be closely
correlated with those of fine-grain
s ediments„
Traveling Companions
Toxics move with sediment. Track one,
and you track the other, and thereby
perhaps predict where toxics might
threaten biological life in the Bay.
It was on that premise that baseline
sediment studies were started in the
Maryland and Virginia portions of the
Bay, one headed by Randall T. Kerhin,
of The Johns Hopkins University's
Maryland Geological Survey, the other
headed by John M. Ziegler, of the Vir-
ginia Institute of Marine Science.
Toxics
Baseline Sediment Studies
July 1980
Lost and Found
Tides, currents, wave action, and
estuarine flow all influence the trav-
els of sediments—and therefore toxics„
Samples of bottom sediments, from more
than 6,500 sites, provided information
about their physical characteristics—
water content, grain size, and carbon
and sulfur content.
Historic charts and shoreline maps
from 1850 and from 1950 and later were
studied to document sites of erosion
and sediment deposits. Factors that
alter depths, such as changes in sea
level, changes in the continental
crust, and tidal variations, were also
taken into acccunt.
From this, a sediment "budget," a com-
parison between sediments entering the
Bay and sediments leaving the Bay, was
developed. Since the Bay is a sediment
trap, the amount of sediment entering
can be expected to outweigh the amount
leaving. It has been estimated that
since salt water first entered the Bay,
about ^5 billion cubic meters of sedi-
ment have been trapped.
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Scientists sampling bottom sediments
Detailed maps axe now being developed
to outline the distribution of sedi-
ments by grain size, to show sites of
erosion and sediment deposit and vari-
ations in the carbon, sulfur, and
water content of the sediment.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency„
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
Useful Information
Knowing more about sediments in the
Bay means knowing more about erosion
patterns, about the filling in of
channels, and about places to dispose
of dredge spoils.
Water-content data will help scien-
tists determine how long it will take
for dredged materials to dry out.
We now have clues to the paths toxics
are likely to follow and where toxics
are likely to accumulate.
We are better prepared to protect
shellfish and to manage the develop-
ment of new shellfish beds0
Information about sediment patterns
will also be useful to Chesapeake Bay
Program researchers investigating the
recent decline in submerged aquatic
vegetation.
An important by-product of the field
sampling in the lower Bay is a refine-
ment of the LORAN C navagational sys-
tem used by air and sea pilots,
resulting in better Bay navigation.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21^01
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
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EPA
Chesapeake
Bay Program
Information
Series
NUTRIENTS
Circulation in the
Chesapeake Bay
April 1981
The Bay in Motion
The Layered Look
Knowing the movement of the Bay's
waters is basic to our under-
standing the Bay as an ecosystem.
The Bay is dynamic, its waters
constantly circulating in intricate
patterns, picking up and depositing
material sometimes miles from its
origin. These patterns are commonly
altered by seasonal fluctuations,
weather changes and tides, forces
that largely influence the movement
of the whole system.
The Bay is used not only for trans-
portation, but is itself a tireless
transporter. Some of the many sub-
stances circulation moves are nu-
trients. Phosphorus, nitrogen, and
calcium are among these important
organic and inorganic chemicals
which enter the Bay from decaying
plant and animal matter, or from
overland runoff and shoreline ero-
sion.
Freshwater inflow from rivers is one
of the major forces affecting estua-
rine circulation (the Coriolis
effect, wind, and tides are the
others). Freshwater from the Bay's
many tributaries flows seaward to-
ward the mouth in the water's upper
layers. Seawater from the open
ocean also enters the Bay, but
travels upward in the lower portion
of the water column. These opposing
flows form a unique, two-layered
pattern in the upper Bay east of
Baltimore and in parts of the Bay's
major tributaries. Figure 1. illus-
trates this two- layered flow.
Fresh Water
Without nutrients the Bay's plants
and animals would die; but too much
can harm Bay life and diminish the
water quality. Understanding how
circulation transports pollutants
such as excessive nutrients will
help scientists and managers know
what measures need to be taken to
limit certain nutrient loadings and
maintain the right amount of
nourishment in the Bay.
Figure 1. Two-layered flow pattern showing denser, heavier
seawater (dark blue) flowing along the bottom of the Bay.
Salt Water
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The meeting of fresh- and seawater
in this two-layer pattern forms
fronts, or saltwater intrusions,
which move up and downstream in
response to the amount of freshwater
entering the tributaries and Bay.
Many organisms use the upstream flow
to move into and within the
estuary. The young and larvae of
ocean-spawning fish such as
menhaden, croaker and eel use this
means to reach their nursery grounds.
—^^A^^
Fresh Water
Sediment Traps
Where the saltwater fronts touch the
bottom of the Bay, special zones are
formed; fine sediments from the
upper layers sink, and are trapped
by heavy, incoming seawater. Here,
the sediments are mixed around and
because these areas are often
clouded, or turbid, they are called
zones of maximum turbidity. (See
Figure 2.) Nutrients are also mixed
here, causing the areas to be rich
and productive. Plankton blooms
often occur near these zones, and
the availability of these tiny
plants as food for fish larvae make
these areas important spawning and
nursery grounds.
Down Under
Although the two-layered flow forms
the basic circulation pattern for a
large part of the Bay, seasonal
changes and other influences often
alter it. When more freshwater
enters, as is the case in the
spring, the Bay becomes stratified,
and the zone of saltwater intrusion
is pushed downstream. In the
autumn, the intrusions are pushed
ups tream.
Wind is another force that can alter
the Bay's circulation pattern. If
the wind blows in the same direction
Figure 2. Zone of maximum turbidity Area with arrows indicates
where sediment is trapped and mixed
as the surface water moves , it will
enhance stratification. If the wind
blows in the opposite direction of
surface movement, stratification
will break down. Wind is an impor-
tant factor in mixing the Bay's
waters.
Storms can drastically change the
two-layered flow. In 1972 Hurricane
Agnes poured so much freshwater and
sediments into the Bay, that surface
salinities were forced miles down-
stream producing a highly stratified
system, and many habitats were
changed. The rooted aquatic plants
in the upper Bay were nearly wiped
out.
Finding the Routes
Because circulation patterns in the
Bay are important, yet complex, the
Chesapeake Bay Program is developing
a mathematical model to help scien-
tists understand the Bay's move-
ments. By pointing out some of the
pathways pollutants can travel, the
model will identify whether nutrient
controls are needed and if so, where.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management implications of the Chesapeake Bay
Program, a project of the U. S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
Citizens Program for the
Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Salt Water
Author: Elizabeth Macalaster, Editorial Assistant: Dottie Van Doren
-------
EPA
Chesapeake
Bay Program
Information
Series
SAV
Biostratigraphy of the
Chesapeake Bay
September 1980
Time Machine
Biostratigraphy is a special tool, a
time machine which takes geologists
back through time to learn about the
history of living things. By
studying layers of Bay sediments
which have built up over time,
scientists can see how animal and
plant communities have changed and
what land activities may have
contributed to those changes.
Telltale Fossils
In the layers of the Chesapeake
Bay's sediments are trapped aquatic
organisms. They lived and died and
became buried under layers and
layers of sediments, fossilized into
permanent records of what once
existed. As part of the Chesapeake
Bay Program's Submerged Aquatic
Vegetation (SAV) Program, scientists
at the Johns Hopkins University are
using biostratigraphy to study some
of these fossils. Right now, their
work is only exploratory and
concentrates on a few sites in the
Bay. At these locations, the
scientists are particularly looking
at fossils of pollen grains, diatoms
(microscopic, one-celled, aquatic
plants) and seeds of bay grasses to
learn how land uses and natural
disturbances have affected
populations of these organisms over
time.
Scientists can tell a lot from
pollen grains. From changes in
pollen grain types, they can tell
when land in a certain area was
cleared of forest and when agri-
culture began. And, the amount of
pollen in the sediment layers will
show how quickly sediment was
deposited.
Changes in diatom populations can
also give scientists a measure of
water quality, because these tiny
plants respond very quickly to
changes in nutrients, turbidity,
trace metals and other water quality
factors.
Because of the important role SAV
plays in the Chesapeake Bay, the
disappearance of these plants is a
major concern to everyone. Studying
how both human and natural
activities, such as major storms,
affected seed populations of SAV in
the past may help scientists
determine why bay grasses are
declining now.
Following the Clues
The Johns Hopkins University
scientists are sampling three areas
in the Chesapeake Bay—the Patuxent
River in Maryland, the Ware River in
Virginia and the Upper Chesapeake
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Diatoms
Pollen
Grain
Kasmer
These are some of the kinds of fossils found in sediment layers of the Chesapeake Bay.
Bay. Sediment samples from each
area provide the scientists with
fossils from different layers, or
time periods, by counting the
numbers and kinds of fossil diatoms,
pollen grains and SAV seeds, and
then comparing this information with
historical records, the researchers
can estimate changes in land uses
from pre-settlement times up to the
present and can correlate tnose uses
to changes in the fossil populations.
Studies from the Upper Chesapeake
Bay have shown, among other things,
that both amounts and kinds of SAV
and diatoms have changed over time.
The scientists relate the changes,
in part, to the settlement of land
in this region. Land clearance in
the early 1800's, for example,
caused an increase in siltation in
the water, leaving less light for
plants to use in photosynthesis.
Thus, diatom populations declined
drastically. Another obvious change
was caused by Hurricane Agnes in
1972. Floodwaters from this storm
destroyed SAV beds in the Upper
Bay. The SAV populations still
haven't recovered in this area.
Using the Past to
Protect the Future
When these scientists finish their
study, they will have reconstructed
a chapter out of history, a special
glimpse at how human and natural
activities have affected some of the
organisms in the Chesapeake Bay.
Much can be learned from knowing how
past changes in land use affected
water quality. This unique look at
some of the historical trends around
the Chesapeake Bay region can help
decision-makers make better choices
for the Bay now and tomorrow.
This is one of a series of briefs,
reports, research summaries, and
final project reports designed to
make available the findings,
observations, and management
implications of the Chesapeake Bay
Program, a project of the U.S.
Environmental Protection Agency. It
is based on conversations with the
principal investigators and on the
final reports covering these
project s.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the
Chesapeake Bay Program
6600 York Road
Baltimore, MD 21212
301/377-6270.
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EPA Toxics
Chesapeake Sediment-Animal Relationships
Bay Program
Information August 1980
Series
Underwater Mix Masters
On the "bottom of the Chesapeake Bay,
there is a hidden world of tiny mol-
luscs, crustaceans, bloodworms, mud
shrimp, and other almost microscopic
animals that burrow into Bay-floor
sediments„ These benthic, or bottom-
dwelling, organisms are masters at
mixing sediment deposits.
Unfortunately, sediments tend more and
more to contain toxics, so these small
creatures could be stirring up trouble„
Questions
When the EPA Chesapeake Bay Program
was started in 1976, there were more
questions than answers about the Bay.
Among them were questions about the
specific relationships between sedi-
ment and animal activities„
Where are the different kinds of ben-
thic organisms found in the Bay? What
kinds of burrow tubes and other struc-
tures do they create? How do they af-
fect the exchange of toxic and other
materials between the sediment and" the
water?
Reinharz, of the Maryland Geological
Survey, and Dr. Donald F. Boesch, of
the Virginia Institute of Marine Sci-
ence.
Using box-core samples, microscopic
examination of sediment particles, and
radiographic, or X-ray, analysis of
the burrows and other structural chan-
ges, investigators have been able to
construct three-dimensional drawings
of the sediment community,,
Figure 1. Three-dimensional diagram of a
sediment community.
Answers
To answer these questions, companion
studies for the upper and lower por-
tions of the Bay are being conducted
by Dr. Owen P. Bricker and Mr. Eli
Crediti Eli Reinharz,
Maryland Geological Survey,
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Figure 2. A sediment community is composed of many kirais of benthic organisms.
Gredlti Martha H. Heigel, Chesapeake Biological Laboratory, Solomons, Maryland.
They have also collected and collated
data on depth distribution, which gen-
erally ranges to about 12 inches
(30 cm). They know what types of feed-
ing methods the various organisms
favor. They know what types of sedi-
mentary structures these animals
"build." And they know which types of
organisms prefer which types of sedi-
ment—sand, clay, mud, or, in some
cases, almost anything.
Scientists also know that the more
wave and current activity there is,
the less building activity goes on.
And, as salinity increases toward the
mouth of the Bay, so does the number
of types of organisms. Moreover, the
more types of organisms and the more
diverse the structures they create,
the greater the rate of chemical ex-
change between sediment and water.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency„
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
Management Tools
What good is it to know so much about
creatures that are so small and, to
the average observer, seemingly insig-
nificant?
They may be an important key to manag-
ing some of the Bay's biggest future
problems, those dealing with the in-
crease of toxic materials in Bay
waters. Knowing the distribution of
benthic organisms and the extent of
their mixing operations can help pre-
dict how long toxic substances will
remain in the system. In addition,
gathering information on the diversity
and abundance of benthic animals will
provide baseline data for comparisons
between healthy communities and those
that might be affected by toxics and
other environmental hazards.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
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EPA Toxics
Chesapeake Investigation of Organic Pollutants
Bay Program
Information September 1980
Series
Tied Up With Carbon
Organic compounds, the building
blocks of life, contain carbon atoms
linked one to another in long chains
or rings. Most of these compounds
come from living things, from plants
and animals. But more recently, man
has begun to make new chains and
rings never before found in the
environment. These new compounds,
the synthetic organic compounds, are
a great boon to modern society.
These are our plastics, our pest-
icides and too often, our new
pollutants.
H-C=C-H
/ \
H-C—C C —C-H
// X # %
H-C C—C c-H
\ / \ /
H-C=C-H H-C=C-H
Phenanthrene is a carbon compound with
a ringed structure.
Choked Up With Organics
Because many of these compounds are
new to Mother Nature, they do not
break down easily in the
environment. They are tough to
digest, they persist. Some, in
fact, relatively few, are toxic.
But those few can cause reproductive
failure, birth defects and cancer.
The U.S. Environmental Protection
Agency (E.P.A.) estimates that
40,000 to 60,000 synthetic organic
compounds are in use in this
country. And the problem is that no
one knows much about the toxicity of
most of these compounds.
To learn more about toxic substances
and their effects on the Chesapeake
Bay, E.P.A.'s Chesapeake Bay Program
is conducting a series of studies on
the sources of toxic substances, how
they reach the Bay and where they
settle in the estuary. In one
study, scientists at the Virginia
Institute of Marine Science (VIMS)
are collecting and analyzing samples
from water, sediment, oysters and
clams to find out what kinds of
organic compounds, and how much of
each, exist in the Bay.
-------
Untying the Carbon
To analyze the sediment and mollusc
samples, scientists are using what
seem to be rooms full of elaborate
instruments. But all of these
complicated tools serve important
roles in identifying the organic
compounds. At least four
instruments are involved in the
identification scheme. By isolating
the compounds and their components,
each instrument progressively
uncovers a little more information.
At the end of the identification
process, the very structure of the
carbon atoms for each compound is
revealed.
The VIMS scientists have finished
collecting data for their mollusc
and sediment samples and have begun
analysis.
Using a different method, the
scientists test the water samples
only for a certain kind of organic
compound, a group called volatile
halogenated compounds. These
substances are formed when waste
water already containing natural
organic compounds is chlorinated.
Bromoform and the common anesthetic,
chloroform, are examples. So far,
the VIMS scientists found low con-
centrations of halogenated compounds
in water samples from the Bay.
Plot to Protect
The VIMS team has a shrewd plot in
mind, one which should help protect
the Chesapeake Bay from toxic
synthetic organic compounds.
Through their identification scheme,
they can select and monitor for
groups of chemicals with known
toxicity, and also watch for the
appearance of new, potentially
harmful compounds. They've designed
this system so that managers can do
the monitoring themselves after the
project is finished. By the end of
the study, the scientists will also
have produced a map showing where
toxic compounds have been found in
the Bay and where places which nat-
urally trap pollutants may occur.
With this knowledge, managers can
monitor, and then if needed, place
limits on harmful substances
entering the Chesapeake Bay.
This is one of a series of briefs,
reports, research summaries, and
final project reports designed to
make available the findings,
observations, and management
implications of the Chesapeake Bay
Program, a project of the U.S.
Environmental Protection Agency. It
is based on conversations with the
principal investigators and on the
final reports covering these
projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the
Chesapeake Bay Program
6600 York Road
Baltimore, MD 21212
301/377-6270.
-------
EPA
SAV
Chesapeake
Bay Program
Information
Series
Light and Decline
of Bay Grasses
August 1981
Linked to Light
For submerged aquatic vegetation
(SAV) living in the Chesapeake Bay,
light is life itself. The watery
environment in which these aquatic
plants live is full of bits of sedi-
ment, chemicals, nutrients, even
tiny plants and seeds. These bits
and pieces reflect or absorb light
as it travels through the water,
creating an obstacle course certain
to prevent some of the light from
reaching the grasses living just
below the surface. In addition,
only a small portion of the light
actually reaching the plant is used
in photosynthesis—the process in
which plants use light energy to
produce food.
Redhead grass, a native Bay grass, and Eurasian watermilfoil, an
intruder, are two of the SAV species used in light experiments at
the University of Maryland's Horn Point Laboratory.
Illustrations from: Summary of Available Information on
Chesapeake Bay Submerged Vegetation, Maryland Department of
Natural Resources, U. S. Environmental Protection Agency and
Fish and Wildlife Service, U.S. Department of the Interior.
FWS/OBS-78/66, August 1978, pgs. 3 & 16.
In the Shadows
Scientists believe that low light
levels in the Bay's waters may be
one cause of SAV's decline. Under
the U.S. Environmental Protection
Agency's Chesapeake Bay Program,
researchers in both Maryland and
Virginia are studying the relation-
ship between SAV and light and what
environmental changes may influence
the amount of light reaching these
grasses. In one kind of experiment,
researchers are finding out just how
sensitive SAV is to light. At the
University of Maryland's Horn Point
Laboratory, scientists are growing
SAV populations in aquaria under
artificial and natural light. Using
special shading screens, they can
allow either a little or a lot of
light to reach the plants. To learn
how well plants photosynthesize
under the range of shading, they
measure oxygen which plants release
during photosynthesis. So far,
researchers are finding that SAV is
very sensitive to light, with small
changes in amounts of light energy
causing large changes in the amounts
of oxygen produced.
Turbidity (which can be measured as
concentration of sediment in water)
is one environmental condition that
scientists think may prevent light
from reaching SAV. To test this
theory they are experimenting with
populations of eelgrass grown in
-------
laboratory aquaria. The scientists
dose some aquaria with high amounts
of sediment, others with small
amounts. The researchers then mea-
sure the amount of oxygen produced
in the aquaria over time compared
with undosed, or control colonies.
In one set of experiments, scien-
tists found that when turbidity is
increased from a dose of 20 milli-
grams per liter (mg/L) to 100 mg/L,
a five-fold increase, as much as a
50 percent reduction in photo-
synthesis occurs.
Blocking the Way
Another area being investigated is
how the growth of plants and animals
living on SAV affects the amount of
light absorbed by the blades. Many
kinds of small plants and animals
live naturally on blades of SAV, but
unnaturally large populations can
grow when too many nutrients, coming
perhaps from human sources, are
present in the water. Either the
encrusting plants and animals use
the nutrients directly, or they feed
on increased supplies of algae which
have already consumed the nutrients.
As more and more fouling organisms
grow, less and less light can be
absorbed by the SAV leaves, creating
low light levels that scientists
believe may be a cause of SAV's de-
cline.
Increased growth of fouling plants
on eelgrass may also be caused by a
lack of natural predation. Scien-
tists at the Virginia Institute of
Marine Science (VIMS) are investi-
gating the role of a small snail
living on blades of eelgrass. By
grazing on the fouling plants, this
Arrow points out two kinds of diatoms which live on blades of eelgrass.
i
A scanning electron microscope took this photograph of part of an
eelgrass blade. The cleared area where Bittium has grazed shows
the underlying cellular structure of the leaf Whole diatoms (one-
celled plants), blue-green algae, bacteria and organic detritus form
the crust on which Bittium feeds. Photo by: Jacques van Mont-
frans, Virginia Institute of Marine Science.
snail keeps the blades clean and
free to absorb light. Eelgrass pop-
ulations in the lower Bay have fewer
of these snails now than in the
past. Scientists speculate that
absence of snails may cause eelgrass
to foul to the extent that light is
blocked from entering the blades.
Researchers at VIMS are now studying
the habits of this snail and what
factors, such as temperature and
salinity, might be responsible for
reduced populations.
Out of the Darkness
Through these and other experiments,
scientists are chipping away at the
secret of the SAV decline. By
learning first how SAV populations
are altered by certain conditions
such as low light levels, and then
what causes those conditions, scien-
tists and managers will know better
how to manage SAV.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management implications of the Chesapeake Bay
Program, a project of the U. S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
Citizens Program for the
Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Author: Elizabeth Macalaster, Editorial Assistant: Janet Malarkey
-------
EPA
Chesapeake
Bay Program
Information
Series
SAV
Waterfowl and the
Decline of SAV
October 1981
A Winter Haven
The Bay, with its rich shoal waters,
protected estuarine rivers and mild,
usually ice-free winters, offers an
ideal wintering spot for many of the
continent's migratory waterfowl. A
million and a half unswerving geese,
swans and ducks spend the winter in
the Bay area or rest while migrating
farther south. These harbingers of
a new season in the Chesapeake Bay
have been favorites of both sports-
men and nature lovers ever since the
area was settled.
Populations of the Bay's waterfowl
can change from year to year depend-
ing on hunting regulations, diseases
and environmental changes such as
weather or water conditions on
breeding grounds. Another recent
ecological change in many parts of
the Bay has been a decline in sub-
merged aquatic vegetation (SAV), a
food resource many species of water-
fowl use. Scientists believe that
the decline of this important vege-
tation may be one cause for the
sharp reduction of some waterfowl
species in the Bay.
Because of the economic and recrea-
tional importance of waterfowl to
the Bay, the U.S. Environmental
Protection Agency's Chesapeake Bay
Program initiated projects to study
the relationship between SAV and
waterfowl. The study was done by
Robert Munro and Matthew Perry at
the Migratory Bird and Habitat
Research Laboratory in Laurel,
Maryland, covering the period from
1971 to 1979. Munro and Perry
looked at waterfowl population sur-
veys in Maryland, taken annually by
the U.S. Fish and Wildlife Service
and then at trends in the distribu-
tion and abundance of SAV beds in
those areas.
Redheads Prefer Grass
The decline in SAV, according to
Munro and Perry's study, caused some
waterfowl species to leave the Bay
area and others to change their
feeding habits. During the 1971 to
1979 study period, many pintails and
wigeons left the area. These ducks
This wigeon, a favorite of Bay sportsmen, is largely a vegetation
eater. Scientists have linked its absence in the Bay area during
winter months to a decline in SAV. (Photo by R.E. Munro)
-------
are both dabblers, feeding in dense,
vegetated areas. Apparently, they
were still tied to SAV for a large
part of their diet, unable to switch
to more available animal food. The
redhead, a diving duck, also did not
change its diet and left for lusher
habitats farther south. However,
the canvasback, another diving duck,
changed its food preference to clams
and was thus able to stay. Scien-
tists believe that the structure of
some ducks' gullets and bills pre-
vents them from changing feeding
habits.
Whistling swans and Canada geese are
two other types of waterfowl that
have adapted their feeding habits
and remained in the Bay area. These
waterfowl have even expanded their
populations, foraging on the rich
grain fields around the Bay.
Signs of Change
The general decrease in kinds of
waterfowl wintering in the Bay area
during the 1970's reflects environ-
mental changes occurring during this
time. The absence of some waterfowl
species shows that SAV and other
parts of the Bay ecosystem are
tightly tied together and that chan-
ges in one part can vastly affect
another. To encourage the return of
the Bay waterfowl and thus help en-
sure a healthy estuary, scientists
will continue to study the cause of
decline in SAV and how these changes
affect other parts of the Bay.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management implications of the Chesapeake Bay
Program, a project of the U. S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
Citizens Program for the
Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Author: Elizabeth Macalaster, Editorial Assistant: Janet Malarkey
-------
summary 1
EPA Nutrients
Chesapeake Fall Line
Bay Program Nutrient Studies
Information January 1981
Series
Importance
Nutrients, are essential to the
health of plants and animals living
in the Chesapeake Bay. Carbon,
phosphorus and nitrogen are three of
the major nutrients needed by the
simplest to the most complex living
organisms in the Bay for main-
tenance, growth and reproduction.
However, these elements are
nourishing only in the right
quantities. In excess, nutrients
can alter water quality and harm Bay
life. Decaying plant and animal
matter provide nutrients naturally
to the Bay, but agricultural and
urban runoff, sewage discharge and
septic tank leakage add additional
quantities. These human activities
can produce a glut of nutrients, or
overenrichment, leading to acceler-
ated plant growth (algal blooms),
noxious odors, decreases in oxygen
supplies and even fish kills.
Because excesses of nutrients
threaten to diminish the Bay's water
quality, the U.S. Environmental
Protection Agency's Chesapeake Bay
Program is looking at present
enrichment in the Bay and acceptable
nutrient levels for the future. One
of the Bay Program's projects in
this area involves quantifying
nutrient loadings (total amount of
nutrients carried by the water)
coming into the Bay from its three
largest tributaries—the Susque-
hanna, Jaraes and Potomac Rivers.
Together, these rivers contribute
about 85% of the freshwater flowing
into the Bay. Thus, measuring
amounts of nutrients traveling past
the fall lines (the upstream points
of tidal influence) of these rivers
is important in assessing the
amounts of nutrients entering the
Bay.
Data from this study will also be
used for a mathematical model that
will help identify current and
future water quality problems in the
Bay. Specifically, the model will
relate nutrient loadings to existing
and future land use, water use, and
regional and economic development of
the Chesapeake Bay area. The model
will also evaluate the feasibility
for controlling loads from .land
runoff. This information will help
management agencies assess relative
nutrient contributions to the Bay
and determine sources of the
greatest inputs. In turn, they will
be able to make better decisions on
ways of maintaining or improving the
estuary's water quality.
The only other major effort to
assess tributary input into the
Chesapeake Bay was made by E.P.A.
from 1969 to 1970. The U.S.
Geological Survey team will compare
these historical data and methods to
their own findings and determine the
existence of any trends for the ten
year period (1969-1979). From the
-------
trend information, scientists and
managers will know how water quality
factors might relate to certain
natural and human-related events
over time.
This summary, one of a series of
publications describing Chesapeake
Bay Program research, presents the
most current findings of the fall
line studies being conducted by
David Lang and David Grason of the
U.S. Geological Survey in Towson,
Maryland.
bridges and prepare the samples on
location. Figure 2. shows the
sample system being used. All water
samples are refrigerated or other-
wise preserved, and sent to labo-
ratories in Atlanta, Georgia or
Harrisburg, Pennsylvania for
analysis.
Research
Sampling
The Susquehanna, Potomac and James
River monitoring sites are located
at Conowingo, Maryland, Chain Bridge
at Washington, D.C., and Carters-
ville, Virginia, respectively (See
Figure 1.). Along with major
nutrients the scientists from the
U.S. Geological Survey are measuring
suspended sediment, which can
transport nutrients, stream
discharge (the volume of water pass-
ing a point along a stream in a
given time) and specific conductance
(a measure of dissolved ions, or how
well the water sample conducts
electricity).
To collect most of the water
samples, the scientists use a
depth-integrating sampler—a heavy,
torpedo-shaped container. This
device faces the river current and
continually collects samples as it is
lowered from the surface to the
bottom and raised back to the sur-
face again. For shallow and
slower-flowing stream reaches,
scientists use a dip bottle—a
simple brass or steel, weighted
bottle. A truck equipped with a
power crane and a small laboratory
allows the scientists to sample from
Figure 1. Fall Line Sampling Sites.
Figure 2. U.S. Geological Survey researcher samples from
a bridge using a specially built crane.
inowingo
A Dam
-------
Results
When the researchers want to look at
these data, they can obtain
computerized printouts of graphs
with the required information al-
ready plotted. Figures 3. to 5. are
actual plots (redrawn) obtained from
data collected at Chain Bridge.
To calculate total amounts of
nutrients flowing past the Chain
Bridge fall line, the scientists
first determine flow rates of water
and concentrations of specific
nutrients in the water. Figure 3.,
for example, shows the concen-
tration of suspended sediments
flowing across the fall line at the
Chain Bridge station over a one-and
a-half-year period. Figure 4. shows
the stream flow during that same
time. From these flow rate and con-
centration figures, scientists can
calculate total sediment loads in
pounds per day, shown in Figure 5.
High peaks on the graphs result from
storm conditions where both
streamflow and concentrations of
suspended sediments are high.
The U.S. Geological Survey team is
also attempting to correlate
nutrient concentrations with stream
flow, suspended sediments, and
~•8015*
900
PLOT OF OAILY SEDIMENT CONCENTRATION VERSUS TIME
70-00-1* 70-10-20 79-01-11 79-03-27 79-06-10 79-00-24 79-11-07 00-01-21 00-04-OS B0-0t>-19 00-09-02
Figure 3. Plot of Dally Sediment Concentration Versus Time.
-------
PLOT OF OAILY DISCHAHGE VERSUS TIME
7H-10-J8 79-01-11 79-03-27 79-06-10 79-08-24 79-11-07 80-01-21 80-0»-05 80-06-19 80-09-02
DATE
Figure 4. Plot of Daily Discharge Versus Time.
specific conductance. The scien-
tists have found correlations of
some significance with many of the
nutrient parameters. Successful
correlation means more economical
sampling, because only physical
parameters (water flow, suspended
sediments) need to be measured.
For example, phosphorus has a high
correlation with suspended sedi-
ments. The Geological Survey
scientists can, therefore, calculate
good estimates of phosphorus without
actually measuring the element.
-------
plot of Daily seoikent loads versus time
P0O155
275000
r-soo :c
2?b0 0 0
175000
'J 150000
100000
75000
50000
aaA
78-08-1* 78-10-28 79-01-11 79-03-27 79-06-10 79-08-2* 79-11-07 80-01-21 80-04-05 8n"06-19 80-09-02
Figure 5. Hot of Dally Sediment Loads Versus Time.
This summary highlights the research
findings from an ongoing project
sponsored by the Chesapeake Bay
Program: Water-Quality Monitoring
of Three Major Tributaries To The
Chesapeake Bay-Interim Data Report
(Principal Investigators, David J.
Lang and David Grason, U.S.
Geological Survey) September 1980.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U.S. Environmental Protection Agency.
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21^+01
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road.
Baltimore, MD 21212
301/377-6270
Author: Elizabeth Macalaster, Editor: Greg McGinty, Editorial Assistant: Dottle Van Doren
-------
summary 1
EPA
SAV
Chesapeake
Distribution and Abundance
Bay Program
Information
July 1980
Series
Importance
Over the last ten years, Bay grass
populations, which play an important
role in the coastal Bay ecosystem,
have declined.
Grasses growing along the shoreline
regions of the Bay:
—Provide food and shelter to many
animals, such as waterfowl, fish,
and shellfish.
—Provide breeding and spawning
grounds for many of these animals0
—Help stabilize the Bay bottom,.
--Filter and provide oxygen to Bay
waters.
--Recycle nutrients, such as phos-
phorus and nitrogen, which are re-
quired by many plants and animals.
—Act as a buffer and take up toxic
substances.
The loss of Bay grasses may indicate
changes in water quality of the Chesa-
peake Bay. Many factors, including
excessive nutrients, chlorine, dis-
ease, dredging, boat traffic, weather,
turbidity, herbicides, or a combina-
tion of several of these factors, are
suspected causes of this decline. How-
ever, no one is sure whether the de-
cline is part of a natural cycle or is
caused by human activities.
A series of research projects is being
conducted by the Chesapeake Bay Pro-
gram to investigate the causes of this
decline in Bay grasses. This research
summary, which is one of a series of
publications describing Chesapeake Bay
Program research, presents the find-
ings of the 1978 SAV distribution and
abundance projects.
Research
Mapping of Grasses
Aerial photography was used to deter-
mine where grasses are found in the
Chesapeake Bay. During the summer of
1978, photographs were taken of the
Bay shoreline, where grasses are found.
This shallow coastal region, less than
three meters deep, is the area where
light can penetrate, allowing the
growth of rooted aquatic grasses.
The photographic information was trans-
ferred to U.S. Geological Survey maps,
so that a complete inventory of the
distribution of Bay grasses could be
produced.
In Virginia, 31 maps were produced of
areas where grass was observed. Of
these, 27 cover the eastern and west-
ern shores of the Bay and show 207,^+80
acres of grasses. The other four maps,
which cover Bay tributaries, show 338
acres of Bay grasses.
-------
Pennsylvania
Maryland
CHESAPEAKE BAY
Susquehanna River.
: feg
Baltimore
Washington. DC
cn^B've'
Virg>n,a
Chesapeake Bay
.Parrott Island ,
Mobjack Bay
:k Rivetf^
. Hamptor
Atlantic Ocean
Norfolk
The areas with the most grasses were:
--Along the western shoreline of the
Bay between the Back and. York Rivers.
—Shoreline of Mobjack Bay.
--Shallow areas east of Tangier Island,
and. other Bay islands.
In the Virginia tributaries, small
grass beds were found along the Poto-
mac River from Matox Greek to Mathias
Neck Point and along the Chickahominy
River, a tributary of the James River„
Figure 1, The Chesapeake Bay*
EPA Research Summary, Chesapeake Bay Office of Research and Development,
May i960.
(See Figure I.)
In the Virginia region of the Bay,
grasses were found mainly at the
mouths of the major rivers and along
the eastern and western shorelines.
For the Maryland region of the Bay, 77
maps were produced. Of these, 17 cover-
ed areas showing no mappable vegeta-
tion, and 24 contained, less than 25
acres of grasses. Figure 2 shows the
acreage of Bay grasses found in Mary-
land waters.
Figure 2, Bay Grasses of Maryland.
Susquehanna Flats
Upper Eastern Shore
Upper Western Shore
Chester River
Central Western Shore
Eastern Bay
Choptank River
Patuxent River
Lower Western Shore
Lower Potomac
2,000
Lower Eastern Shore
T"
3,ooo 4,ooo
ACRES
5,000
1 1
6,000 7,000
As this figure shows, the Maryland mid-Bay
sites, such as the Chester River, Eastern Bay,
and Choptank River, have the greatest abun-
dance of Bay grasses, as compared to the other
Maryland Bay regions.
-------
Field Study Results
Field, studies were used to verify aer-
ial photography information and to
identify plant species.
Analysis showed that the kinds of
grasses found in an area were related
to the salinity of the water. Table 1
shows the relationship between species
and salinity.
Table 1. Relationship Between Grass Species
and Salinity.
Salinity
Fresh Water
Intermediate
Low
High
Major Species Found
Coontail
Ceratophyllum demersum
Bushy pondweed
Na.ias guadalupensis
Waterweed
El odea canadensis
Wild celery
Vallsneria americana
Horned pondweed
Zanichellia palustris
Redhead grass
Potamogeton perfolictus
Eurasian milfoil
Myriophyllum spicatum
Sago pondweed
Potamogeton pectinatus
Eelgrass
Zostera marina
Widgeongrass
Ruppia maritima
The two main species found in the
lower Bay were eelgrass and widgeon-
grass. Widgeongrass is usually found
in shallow, protected regions, whereas
eelgrass is usually found in the deep-
er, more exposed areas, along the
shore.
The field data for the Maryland study
confirmed that the midportion of the
Bay from the Magothy to the Choptank
Rivers had the greatest diversity of
species. This diversity declined to
two or three species in the southern
portion of the eastern shore, where
horned ponweed and widgeongrass were
usually found.
Historical Distribution of Bay Grasses
To determine how the dsitribution of
grasses has changed over time, early
aerial photographs were studied. This
information showed that there has been
a downward trend in grasses in the
Chesapeake Bay over the last ten years
In the Virginia region of the Bay, six
areas had photography available for
selected years between 1937 anc* 1978.
These sites were Paxrott Island,
Fleets Bay, Mumfort Islands, Jenkins
Neck, the East River, and Vancluse
Shores. Of these areas, only Vancluse
Shores did not show significant
changes in the amount of grass present
In general, the amount of vegetation
observed in 1937 increased for about a
35-year period until a dramatic de-
cline occurred in the 1970®s. This
decline continued through the 1978
inventory, which documented the lowest
levels of vegetation seen over the
last 40 years. Some researchers be-
lieve that, because the 1937 and I973
data are similar, the factors respon-
sible for the 1930's decline may also
be active in the present decline.
In Virginia, the greatest decline oc-
curred in the lower reaches of the
major rivers. North of the York River
on the western shore, significant de-
clines were also noted. The maps in
Figure 3 are part of a series of six
that illustrate the changes in the
grass population at the Fleets Bay
site. Similar series exist for the
other five sites and are contained in
the full Virginia report.
-------
KILOMETER
MAR 29, 19 37
KILOMCTE*
NOV 24, 1974
<10% 10-40% 40-70%
Figure 3„ Historical Distribution of Grasses
at Fleets Bay, Virginia.
From DlstriUitlon and Abandance of Submerged Aquatic Vegetation In the Lower Chesapeake Bay¦ ".TKinlai Orth, ft. S., K. A. Moore, and H. H. Gorden, Virginia
Institute of Marine Science, Gloucester Point, VA, EPA Report No. 600/8-79-029/ SAV1t Sept. i9?9.
-------
In Maryland, the historical analysis
was not as clear-cut„ Three sites were
selected: the Chester River, Eastern
Bay, and the Gunpowder River„ The
Chester River site showed fluctuations
in the amount of vegetation present.
The Eastern Bay area showed a downward
trend in acres of grasses found, al-
though photographs were available only
for three years. The third site, the
Gunpowder River, which includes the
Dundee, Saltpeter, and Seneca Creeks,
was chosen because of its nearness to
the C. P. Crane Generating Station,
which discharges cooling water into
Saltpeter Creek, The data before and
after the plant opened in 1962 show no
changes in grass populations, but this
may not reflect a normal situation,
since, during this period, there was a
sudden increase in the abundance of
Eurasian milfoil, an introduced spe-
cies 0
ginia resource management agencies,
for use in the review of permit appli-
cations for dredging and disposal and
shoreline construction. The maps have
already aided Virginia agencies in
avoiding disturbance of established
grass communities and are thereby
helping to protect the Bay ecosystem.
From all the historical data, it seems
that the populations of rooted aquatic
grasses have been declining in most
areas of the Bay over the last ten
y ears.
Management Implications
The maps developed in the two projects
provide a basis for future comparisons
of changes in the populations of Bay
grasses. At present, the maps are be-
ing put to practical use. Copies have
been distributed to Maryland and Vir-
This summary highlights the research
findings from two projects sponsored
by the Chesapeake Bay Program: Distri-
bution and Abundance of the Submerged
Aquatic Vegetation in the Lower Chesa-
peake Bay, Virginia—1978 (Principal
Investigator, Robert J. Orth, Virginia
Institute of Marine Science) and Dis-
tribution of Submerged Vascular Plants
in the Chesapeake Bay. Maryland—1978
(Principal Investigator, Richard R,
Anderson, American University).
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency,,
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
-------
summary 1
EPA
Chesapeake
Bay Program
Information
Series
¦¦¦¦¦¦
Importance
Many toxic substances are now being
discharged directly or indirectly into
the Chesapeake Bay. Since many of
these toxic chemicals end up in the
sediments of the Bay, deposition and
erosion have significant effects upon
the fate of these chemicals. Further-
more, interaction between toxic sub-
stances and benthic or bottom-dwelling
organisms takes place in the sediments,,
For these reasons, two organizations
sponsored by the Chesapeake Bay Pro-
gram (Toxics Program), the Virginia
Institute of Marine Science and the
Maryland Geological Survey, are con-
ducting baseline sediment studies to:
—Determine the distribution and
physical properties of Bay sediments.
—Identify sites of erosion and
deposition in the Bay.
—Develop a total sediment budget
for the Bay.
This research summary, which is one of
a series of publications describing
Chesapeake Bay Program research, pre-
sents the preliminary findings of
these baseline sediment studies,
which are being conducted at the
Johns Hopkins University's Maryland
Geological Survey and at the Virginia
Institute of Marine Science.
Toxics
Baseline Sediment Studies
July 1980
Background
The modern Chesapeake Bay system was
formed by the flooding of the ances-
tral Susquehanna and Virginia River
valleys, beginning some 10,000 to
15»000 years ago.
In the river systems, strong currents
carried sediment and other matter out-
ward toward the ocean. But, with the
change to an estuary, in which sea-
water flows into the Bay in the lower
layers and fresh water flows outward
in the upper layers, the total flow of
fresh water became less. A decrease in
the ability of the Bay's upper layers
to hold material in suspension re-
sulted, and now, only very fine-grain
matter reaches the mouth of the Bay0
The rest settles to the bottom and is
trapped within the zone of the turbid-
ity maximum, an area in the northern
section of the Bay about five miles
long. Here is where the interfacing
fresh and salt water touch the bottom.
Heavier sediments sink through the in-
terface, but are usually pushed back
by the inward flow of seawater. Light-
er particles are trapped and mixed
around at this interface, often caus-
ing the area to become turbid.
-------
Since the time of salt-water intrusion,
the Chesapeake Bay has trapped approx-
imately 45 billion cubic meters of
sediment, coming primarily from land
runoff, shore erosion, primary produc-
tion, and the sea. Deposition of Bay
sediments also results from erosion of
islands and shorelines, and from the
creation or expansion of channels and
sand bars through shifting currents.
Research
Sediment Sampling and Analysis
The plan for the field sampling was
based on a uniform grid system to en-
sure Bay-wide sampling. Sediment pro-
files (box-core and gravity-core sam-
ples) were collected at k,500 sites in
the Maryland region of the Bay and
2,018 locations in the Virginia por-
tion. In the field, physical charac-
teristics of the samples were noted,
and laboratory analysis provided
information on grain size and water,
carbon, and sulfur content of the
sediments.
Preliminary results have indicated
that j
—Sands are generally found in the
shallow areas and lower reaches of
the Bay.
--Clayey silts and silty clays were
found in the deeper Bay regions.
--Water and total carbon content
increase as the mean grain size
becomes finer.
The beach and near-shore sands are
distributed primarily by wave action,
whereas the sediments in the main
channel are influenced mainly by estu-
arine processes. Between these two
zones lies a region of sediment mixing
that may result from combined tidal,
current, and wave actions.
Exposed areas of geologically old
coastal-plain sediments were discover-
ed on the Bay floor on the eastern
shore along Poplar Island. Along the
Calvert County shoreline on the west-
ern shore, scientists found a similar
outcrop.
Erosion and Deposition
Two methods are being used to document
sites of erosion and deposition in the
Chesapeake Bay:
—Comparison of historic bathymetric
(water depth) charts.
--Assessment of shoreline erosion by
reviewing historical shoreline maps.
Bathymetric data from the 1950 and
later surveys and 1850 surveys were
compared. However, other factors be-
sides deposition and erosion alter
depths, such as sea-level changes,
continental-crust changes, and semi-
annual and annual tidal variations.
An equation incorporating these fac-
tors was used to compare the sets of
bathymetric data. These comparisons
resulted in the determination of aver-
age sedimentation rates for different
Bay regions.
-------
Researchers in Virginia noted an
interesting pattern when they compared
average sedimentation rates to water
depths in three areas: Motjack Bay,
Pocomoke Sound, and the main stem of
the Bay. Both the main stem of the
Bay and Motjack Bay show the following
pattern of sedimentation rates:
Sedimentation
Rate
Depth
High
0-6 ft. (0 - 1.8 m)
Low
6-12 ft. (1.8 - 3*7
High
12 ft. (3.7 m)
•
A high sedimentation rate was found
for the shallow and deep areas, and a
low rate for the 6-to-12-foot depths.
Pocomoke Sound was similar, except
that it lacked the high rate for shal-
low depths.
The average deposit rate in the lower
Bay has been found to be 22 inches
(55 cm) per century. In general, the
lower Bay is filling with sediments at
a slightly faster rate than the rela-
tive sea-level rise.
In Maryland, similar results were
found:
—Major deposition in the main chan-
nel is causing the Bay to become
shallower.
—Erosion along the slopes of the
channel is causing the Bay to become
wider.
—Varying patterns of erosion and
deposition occur along near-shore
areas.
To assess shoreline erosion, the Mary-
land researchers used historical shore-
line maps to designate all Maryland
shorelines as areas of sediment loss
or gain. Existing geological informa-
tion is being used to calculate the
sediment types (sand, silt, and clay)
available to the Bay through shoreline
erosion. The Virginia investigators
have also undertaken a sampling pro-
gram to permit quantitative estimates
of the volumes of sand, silt, and clay
derived from corresponding areas of
shoreline erosion. They have estimated
that between I85O and 1950. some 95
million cubic yards of sediments have
eroded from lower Bay shores.
Sediment Budget
A sediment budget is basically a com-
parison of sediments entering the Bay
and sediments leaving the Bay, to
determine net gain or loss. Since the
Chesapeake Bay acts like a sediment
trap (sink), most of the sediments
sink to the Bay bottom, resulting in
a net gain.
Formulation of a budget for the Bay
requires an inventory of the principal
sediment sources and sinks and rates
of deposition. The principal sources
of sediment are:
—The tributaries.
—Erosion of shorelines.
—Sediments from the continental shelf
entering through the Bay mouth.
—Decaying organisms.
-------
Sediment Maps
Using results from this research,
detailed maps of the Chesapeake Bay
are being compiled to outline:
—Distribution of sediments by grain
size.
—Sites of erosion and deposition.
--Carbon and sulfur content of
sediments.
--Water content of sediments.
Once completed, the research will
provide three major products:
—Information concerning the recent
history of the bottom sediments of
the Chesapeake Bay.
—Maps detailing the present sedi-
ment distribution of the entire
Bay.
--A sediment budget, or an account of
the sediment volumes entering the
Chesapeake Bay from specific sources
and an account of the deposition of
these sediments.
Management Implications
The results of this research will help
define the relationship between sedi-
ments and toxic substances in the Bay.
At present, little is known about the
paths that toxic substances follow
once they enter the Bay. It is known,
however, that toxic substances tend to
cling to clay and other fine-sediment
particles. Potential toxic "hot spots,"
or areas of toxic-chemical accumula-
tion, may be predicted using informa-
tion on sediment characteristics.
Understanding the general role of
sediments as the site of toxic-chemi-
cal deposition, transformation, or
uptake by organisms is a prerequisite
to managing toxics.
Species of submerged aquatic vegeta-
tion, or Bay grasses, live on sedi-
ments suited to their survival. The
habitats of bottom-dwelling organisms
like clams and worms are also limited
by the nature of the sediments. These
baseline sediment studies will provide
the data required to establish the
connection between sediment types and
organisms that live there. In particu-
lar, the data will be very important
for those studying the recent decline
of submerged aquatic vegetation.
This research will be useful to mana-
gers when addressing such issues as
loss of land by erosion, filling in of
main shipping channels, or the choice
of suitable sites for disposal of
dredge material. For example, areas of
high natural deposition may be appro-
priate for the disposal of dredged
material. Reestablishment of the natu-
ral biota is more likely if the sedi-
ment characteristics of the dredging
and disposal sites are similar.
Water-content data from these studies
will help determine how long it will
take for dredged materials to dry out,
a major consideration for managers.
Information on sediment characteris-
tics, especially their distribution,
may help identify potential shellfish
habitats and aid managers who desig-
nate areas for shellfish harvesting
and for the development of new oyster
bars.
-------
From the surface samples, the research-
ers have identified sediment types,
including potential areas for sand and
gravel extraction. In the future, such
construction-aggregate mining may be-
come an important economic resource in
the Chesapeake Bay.
Another by-product of the field sam-
pling of the lower-Bay study was a
refinement of the LORAN C theoretical
values. LORAN C, Long Range Aid to
Navigation, is a radio navigation de-
vice used by air and sea pilots.
LORAN C is also used by scientists to
accurately locate sampling stations in
a body of water. The researchers study-
ing sediment properties in the lower
Bay developed bias correction factors
for the LORAN G theoretical values at
2,018 locations. The tabulated loca-
tions will now give other Chesapeake
Bay scientists the ability to collect
additional data from the same loca-
tions more accurately. The corrected
values will also assist boaters and
pilots in navigating with greater pre-
cision.
This summary highlights the research
findings from two ongoing projects
sponsored by the Chesapeake Bay Pro-
gram: Chesapeake Bay Earth Science
Study Sedimentology of the Chesapeake
Bay (Maryland). Principal Investiga-
tor, Randall T. Kerhin, Maryland Geo-
logical Survey, and Baseline Sediment
Studies to Determine Distribution,
Physical Properties, Sedimentation
Budgets and Rates (Virginia), Princi-
pal Investigator, John M. Ziegler,
Virginia Institute of Marine Science.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency0
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21^01
301/266-0077
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
-------
summary z
EPA
Chesapeake
Bay Program
Information
Series
SAV
Biostratigraphy of the
Chesapeake Bay
September 1980
Importance
Biostratigraphy is a method
geologists use to analyze sediment
layers and their fossil remains. By
counting the numbers and kinds of
fossils in each layer, scientists
can identify changes in populations
of animals and plants over time.
Aquatic organisms such as diatoms
(microscopic, one-celled plants),
pollen, and seeds of terrestrial and
aquatic plants, are trapped and
preserved in the layers of the Bay's
sediments. These fossil remains
represent a portion of the estuarine
biota at the time of deposition. By
analyzing these fossils, scientists
can evaluate changes in biology and
chemistry of the Chesapeake Bay and
its tributaries, and thus, identify
historic changes and trends in uses
of the river basins.
Variations in species composition
and in numbers of terrestrial pollen
grains over time indicate changes in
watershed uses, as well as how
quickly sediment was deposited.
Each species of flowering plant
produces a distinctive form of
pollen, and scientists can examine a
pollen grain microscopically to
determine which species of plant
produced it. In a watershed,
changes from high percentages of oak
to ragweed pollen, indicate that the
land has been cleared of forest.
Low concentrations of pollen in the
sediment generally indicate high
rates of sediment deposition.
Historical records can date when
these changes occurred, and
scientists can then use the dated
sediment layers, or horizons, to
calculate sedimentation rates. De-
termining how quickly sediment was
deposited at different times will
provide a measure of turbidity and
siltation, important factors affect-
ing water quality at those times.
Changes in amounts and composition
of diatom populations indicate
changes in water quality, because
diatoms will quickly respond to
changes in nutrients, levels of
turbidity, temperature, trace metals
and other factors. Characterizing
diatom populations at different
times provides a record of changing
conditions, such as progressive
eutrophication (excessive nutrients)
in the Bay.
Researchers at the Johns Hopkins
University are currently using
biostratigraphy to study changes in
submerged aquatic vegetation (SAV)
populations, eutrophication, and
sedimentation rates in the
Chesapeake Bay over long periods of
time. They will examine historical
records for dates of human activity
and meteorological events to
determine if population changes of
-------
2.
SAV, diatoms, and pollen coincide
with periods of major human
activities or natural disturbances.
This summary will highlight research
to date of a research project headed
by Dr. Grace S. Brush at the Johns
Hopkins University. It is one of a
series of publications describing
Chesapeake Bay Program research.
Research Sampling Sites
The Johns Hopkins University
researchers sampled three areas in
the Chesapeake Bay--the Patuxent
River, the Ware River and the Upper
Chesapeake Bay (see Figure 1). The
Patuxent and Ware Rivers were
chosen, because other Chesapeake Bay
Program scientists and engineers are
currently studying these
watersheds. Also, the Patuxent
represents an area of intensive
development, while the Ware River is
a more pristine watershed;
biostratigraphic data from these two
regions would, therefore, provide
valuable comparisons between the
impact on water quality of different
land uses. The Susquehanna
Flats-Furnace Bay area in the Upper
Chesapeake Bay was chosen because
historically, this watershed has
been intensively used for both
farmland and industrial
development. In addition, large
populations of SAV once grew there.
Several sediment cores were taken at
each of the three regions using a
piston corer 5.4 cm (about 2 inches)
in diameter and ranging in length
from one to two meters. This device
extracts cores up to 180 cm (70.9
inches) long.
Figure 1. Sampling sites for sediment cores
in the Chesapeake Bay.
Core Analysis
The scientists have completed their
analysis of cores collected in the
Furnace Bay region. They have
nearly finished with the Patuxent
cores and have just begun the Ware
River sampling.
Pennsylvania
Maryland
CHESAPEAKE BAY
Susquehann^ Fl^ts
SCALE .» MILES
Washington. DC
Patuxent
Norfolk
-------
3.
The core samples are analyzed in
several steps. The core is split
lengthwise; one side is for
extracting seeds, the other for
diatoms and pollen. The seed
section is divided into small
samples which are then soaked in
dilute acid to break apart the
sediment. The samples are then run
through a series of sieves. The
larger mesh sizes sort out the
seeds, while the smaller-meshed
sieves catch the residue.
Scientists examine the residues to
determine the coarseness of the
sediment on which SAV grows.
The diatom/pollen sample is also
divided into small sections, then
weighed, dried and treated with
chemicals. The chemicals break
apart the sediment and isolate the
pollen grains which are then counted
and identified as to species.
Generally, the fewer numbers of
grains present, the greater the
sedimentation rates in that area.
Scientists use a similar procedure
to extract, count, and identify
diatoms. An increase in numbers of
diatoms usually indicates an
increase in eutrophic conditions.
Figures 2, 3 and 4 illustrate the
kinds of SAV seeds, pollen grains
and diatoms found in the core
samples.
Results
From analyses of the Furnace Bay
cores, the Johns Hopkins team has
constructed a graph (Figures 5-7)
relating land uses from
pre-settlement up to 1980, to
populations of SAV and diatoms.
Figures 5-7 show that:
Figure 2. Bay Grass Seed Fossils
Figure 3. Pollen
Grain Fossils
Figure 4. Diatom Fossils
-------
1980
1980
1950
1950
1920
1920
1890
1890
1860
1860
1830
1830
1800
1800
1770
1770
Figure 5. Furnace Bay: Effects of land use on SAV and diatom
populations, showing watershed uses over time.
-SAV beds are continuous from
before human settlement in the
early 1800's up to the time of
Hurricane Agnes in 1972.
-Some changes in SAV species
accompanied settlement.
-SAV practically disappeared after
Agnes
-The kinds of diatoms changed from
those living attached to rocks or
other plants (epiphytes) before
settlement, to types living freely
in the water (plankton).
-Diatom species changed from those
preferring low nutrient levels to
types preferring high nutrients by
the early 20th Century.
DIATOMS
TOTAL NO.
DIATOMS
WATER
QUALITY
2 Epiphytes
11 Plankton
Med-high
nutrients
*8 x 108
1 Epiphyte
3 Plankton
Med-high
nutrients
*6 x 106
6 Epiphytes
3 Plankton
High
nutrients
20 Epiphytes
3 Plankton
Low
nutrients
*24 x 10e
8 Epiphytes
0 Plankton
Med-low
nutrients
' No.'s in millions
WATERSHED
(see map)
SUBMERGED
AQUATICS
FURNACE BAY
-Amounts of diatoms decreased 24
fold from before settlement to
after settlement.
Decreases in the amounts of both SAV
and diatoms relates to the
settlement of the land in the Upper
-------
5.
1980
1950
1920
1890
1860
1830
1800
1770
DIATOMS
SUBMERGED
AQUATICS
TOTAL NO
TYPES
DIATOMS
2 Epiphytes
11 Planklon
Wed-high
nutrients
6 x 10*
Med-high
nutrients
1 Epiphyte
3 Plankton
B x 10*
High
nutrients
6 Epiphytes
3 Plankton
•6 x 10*
20 Epiphytes
3 Plankton
1 x 10*
8 Epiphytes
0 Plankton
Med-low
nutrients
24 x 10*
FURNACE BAY
WATERSHED £
(see map)
No.'s in millions
1980
1950
1920
1890
1860
1830
1800
1770
Figure 6. Furnace Bay: Effects of land use on SAV and diatom
populations, showing changes in SAV populations over time.
Chesapeake Bay region. Land
clearance in the early 1800's caused
an increase in siltation in the
water, resulting in less light
available for plants to use in
photosynthesis. This factor may
have been the reason for the decline
in numbers of diatoms after
settlement, according to the Johns
Hopkins researchers. Later, the
numbers increased at about the time
inorganic fertilizers were added to
the watershed. The additional
nutrients may have compensated for
possible light-limiting conditions,
thus allowing the populations to
increase.
Hurricane Agnes caused the most
disasterous change by wiping out SAV
populations and causing a shift in
the diatom populations to planktonic
forms. The storm may have provided
an avenue for toxics to reach the
Bay or its plant life. Variations
in the diatoms also suggest that the
Upper Bay has become increasingly
eutrophic with increased use of the
watershed.
Management Implications
Continuous increased siltation,
whether resulting from agriculture,
lumbering or urbanization, can have
-------
6.
1980
1950
1920
1890
1860
1830
1800
1770
DIATOMS
SUBMERGED
AQUATICS
TOTAL NO
DIATOMS
2 Epiphytes
11 Plankton
Med-high
nutrients
6 x 106
Med-high
nutrients
1 Epiphyte
3 Plankton
8 x 10*
6 Epiphytes
3 Plankton
High
nutrients
6 x 10*
20 Epiphytes
3 Plankton
1 x 10*
8 Epiphytes
0 Plankton
Med-low
nutrients
*24 x 10
FURNACE BAY
WATERSHED £
(see map)
No. s In millions
1980
1950
1920
1890
1860
1830
1800
1770
Figure 7. Furnace Bay: Effects
populations, showing changes in
profound (largely injurious) effects
on water quality and biota. This
research gives a unique, historical
perspective on how water quality has
been affected by human activity and
natural disturbances in the past.
Managers can use this information to
suggest how future activities might
affect the Bay's water quality.
Knowing the amounts of pollen and
their distribution at certain times
will not only indicate to managers
what kinds of land uses can
influence sediment transport, but
will also help them estimate the
rate and distance that sediment moves.
of land use on SAV and diatom
diatom populations over time.
The changes in amounts and kinds of
diatom populations in the Bay as
they relate to past land uses
indicate what conditions can
contribute to increased
eutrophication in the future.
This summary highlights the research
findings from a project sponsored by
the Chesapeake Bay Program;
Biostratigraphy of the Chesapeake
Bay and Its Tributaries, (Principal
Investigator, Grace S. Brush, The
Johns Hopkins University).
For more information, contact:
EPA Chesapeake Bay Program
301/266-0077
-------
summary
EPA
Chesapeake
Bay Program
Information
Series
NUTRIENTS
Circulation in the
Chesapeake Bay
April 1981
Importance
The addition of nutrients such as
phosphorus, nitrogen, and calcium to
water is a natural and healthful
process. These organic and in-
organic chemicals can enter the Bay
from decaying plant and animal mat-
ter or from overland runoff and
shoreline erosion. Living organisms
in the Bay use nutrients for main-
tenance, growth and reproduction.
However, increased human activity
can accelerate nutrient enrichment,
turning lakes into swamps, stag-
nating bodies of water and harming
organisms living there. The accel-
eration process is well understood
in lakes, but has been little stud-
ied in estuarine systems.
Because nutrients largely affect the
water quality of the Bay yet have
been so little studied, EPA's Chesa-
peake Bay Program began a program to
investigate nutrient enrichment in
the Chesapeake Bay. One of the pro-
gram's aims is to evaluate alterna-
tives for controlling nutrient load-
ing from the land. However, before
control measures can be accurately
assessed, the relationship between
nutrients and water quality in an
estuarine environment must be under-
s tood.
One important channel to understand-
ing how nutrients affect water qual-
ity is to look at circulation in the
Bay. Water circulation moves and
distributes much material in this
estuary, including nutrients. Pat-
terns of water circulation control
not only pathways of nutrients, but
also the distribution of organisms
relying on these chemicals. Hie
quality of the Bay, in turn, can be
measured in large part by the num-
bers and kinds of organisms living
there.
Since circulation carries and dis-
tributes other constituents includ-
ing pollutants and sediment, it has
far greater implications for water
quality than just nutrient
enrichment. The Chesapeake Bay Pro-
gram is developing a computerized
model of circulation in the Bay.
The model will simulate the circu-
lation patterns described here, and
thus, help discern some of the pol-
lutant pathways in the Bay. Model-
ing water circulation and its impli-
cations for understanding water
quality will be the subject of a
future summary in the Chesapeake Bay
Program's Information Series.
The Four Forces
Freshwater Inflow
One of the most powerful forces af-
fecting circulation in estuaries is
freshwater inflow. Most freshwater
entering an estuary comes from pre-
cipitation that falls in the drain-
-------
2.
age basin. Fresh water reaches the
tidal waters by streams and under-
ground movement which run into
rivers and eventually the estuary.
—A—A—,
Fresh Water
At the same time, saltwater from the
mouth of the estuary flows along the
bottom up toward the head, creating
a characteristic gradient in salin-
ity from the mouth (high salinity)
to the head (low salinity). This
flow pattern can be seen as a two-
layered flow. The top layer con-
tains less saline water which flows
seaward; the bottom section is sal-
tier, denser water with a tendency
to flow up the Bay. The two layers
are separated by an intermediate
layer, the halocline, in which the
increase in salinity is very abrupt
(See Figure 1). This two-layered
pattern forms saltwater fronts, or
intrusions, which move up and down-
stream in response to river flow.
Figure 1. Two-layered flow pattern showing saltwater intrusion
(dark blue area).
Fresh Water
Zones of maximum turbidity are loca-
ted where these fronts touch bottom
(See Figure 2). In the upper Bay
and upper tributaries the zones
usually range from five to ten
miles. These areas act as sediment
traps where sediment particles
washed in with freshwater settle
into the lower layers and are then
pushed back upstream by inward-
flowing seawater. They are trapped
and mixed around at the interface
between fresh- and seawater, often
causing the area to become turbid.
Because of the turbulent action,
which brings rich bottom water up to
surface layers, these zones can be
very productive. Nutrients are
mixed in these areas and become
available to phytoplankton in the
upper layers of the water. The tur-
bulent action itself keeps phyto-
plankton suspended in the lighted
zones of the water, allowing the
tiny plants to use light in photo-
synthesis. Zones of maximum turbid-
ity may, subsequently, represent
important nursery grounds for many
anadromous fish—striped bass,
Figure 2. Zone of maximum turbidity. Area with arrows indicates
where sediment is trapped and mixed.
herring and alewives , among others.
If the location of these fronts is
in some way altered by a change in
freshwater inflow, the amounts of
nutrients available, and hence the
productivity of plankton, may be
altered, possibly affecting the
abundance and diversity of biota.
During the year, freshwater inflow
fluctuates widely. The greatest
inflow occurs in the spring from
rainfall and melting snow. Strati-
fication (layering) of an estuary is
strongest at this time, while in the
fall when inflow is weakest, no dis-
tinct layers may appear at all. A
reduction in flow can change the
two-layered circulation pattern by
shifting the turbidity maximum zone
upstream, thereby compressing spawn-
Salt Water
Saltwater
-------
3.
ing and nursery grounds. Stratifi-
cation will also decrease resulting
in greater mixing of salinity.
Inflow also varies within any season
depending on rainfall or catastro-
phic events like storms. In 1972,
Hurricane Agnes caused the Bay's
tributaries to swell with flood-
waters; over a third of the region
received more than 12 inches of
rain.l Most rivers crested at
levels higher than previously noted
in some 200 years of record, and
flows in the Susquehanna alone aver-
aged 15.5 times greater than
normal.2 Consequences on nutrient
distribution and on other biota were
drastic in the upper Bay, where Bay
grasses all but disappeared.
Coriolis Effect
All things which move over the sur-
face of the earth, whether birds,
wind, rivers, bullets or rockets,
slide from their appointed path to
the right in the Northern Hemis-
phere, to the left in the Southern
Hemisphere. This sidewise drifting
is called the Coriolis Effect, named
after the 19th century mathematician
G.G. Coriolis, who made the first
complete analysis of it. The effect
is caused by the clockwise rotation
of the earth.
In the Bay, the effect shows its
power by moving salt water from
tidal action slightly to the eastern
side. Saltwater thus hugs the Eas-
tern Shore, while freshwater flows
seaward close to the Western Shore.
1. Impact of Tropical Storm Agnes
on Chesapeake Bay. Baltimore
District, Corps of Engineers, Dept.
Army, March 1975. p. 9.
2. Impact of Tropical Storm Agnes
on Chesapeake Bay. Baltimore
District, Corps of Engineers, Dept.
Army, March 1975. p. 11.
Figures 3 and 4 show how the
Coriolis effect influences patterns
of salinity in the Bay. This type
of flow pattern has implications for
the distribution of plants
and animals which re-
quire different
salinities in
their habitats.
Top View
Figure 3. Salinity patterns in a shallow estuary altered by the
Coriolis effect. The numbers correspond to concentration of salts in
the water, expressed as parts of salts per thousand parts of water
(ppt). Seawater is about 35 ppt or 3.5% salts.
Western
Shore
Cross Section at Mid-point
Eastern
Shore
20%.
25%,
Figure 4. Cross section of an estuary showing effect of Coriolis force
on isohalines (locations in the water where the salinity is equal).
-------
4.
Wind
The greatest effect of wind on
estuarine circulation is seen in
day-to-day wind patterns. Wind
pushes water, thereby imposing mix-
ing patterns of the water, espe-
cially in shallow estuaries such as
the Chesapeake Bay. On the Bay,
prevailing winds are westerly.
Since the Coriolis effect will
deflect moving water to the right
going up the Bay, these two forces
together push water generally
eastward. The wind shows its
greatest power where the estuary is
less sheltered and wider.
Wind also works together with
barometric pressure which depresses
or raises the level of surface water
on the Bay. These two forces
influence the nature of the classic
two-layered circulation by
occasionally causing a flow
reversal. The forces of wind and
barometric pressure changes may
produce complex internal waves.
These waves or oscillations may be
important in contributing to
vertical mixing, churning up nu-
trients from rich bottom waters.
Spring
Earth
Moon
©
Moon
- f
sfe.
Earth
Neap
Effect of the gravitational forces
of the sun and the moon on the
earth's bodies of water.
Earth
Moon
Tides
Tides are waves with a length of
about half the circumference of the
earth (23,300 km, 12,600 miles) and
are caused by the gravitational
attraction of the sun and moon on
the earth. The attraction is
strongest on the side of the earth
facing the moon, causing the water
on that side to bulge out and be
pulled toward the moon. The sun
also exerts tidal influence on the
seas, although the bulge is smaller,
because the sun is so much farther
away.
The effect of the sun becomes espe-
cially important when the sun and
moon are lined up with the earth
(See Figure 5). The combined gravi-
tational attraction produces a very
strong tide, called the spring
Figure 5. Location of the sun and moon relative to the earth during
spring and neap tides. Dark area represents shadowed parts of the
moon and earth.
tide. It occurs about every 14 days
at new and full moon. Neap tides,
or tides with ranges lower than nor-
mal , occur when the sun and moon are
at right angles to each other, also
about every 14 days.
In an estuary such as the Bay, daily
tides could affect stratification,
slightly altering circulation pat-
terns. A flood tide will push the
salt water intrusion further up-
stream in the upper Bay and tribu-
taries than an ebb tide . Spring
and neap tides emphasize these fluc-
tuations; while a spring tide de-
creases stratification, a neap tide
increases stratification.
-------
5.
Seasonal Circulation in the
Chesapeake Bay
Seasons in the Chesapeake Bay are
noted by important changes in circu-
lation. Freshwater inflow, one of
the four forces driving circulation,
almost entirely on its own causes
these variations. Changes are re-
flected primarily in salinity and
are revealed at zones of maximum
turbidity and in the two-layered
flow.
Figure 6 is a map of the Bay showing
zones of maximum turbidity and areas
where the two-layered flow would
most likely be susceptible to sea-
sonal changes. The rivers on the
Western Shore contribute most of the
freshwater to the Bay. During the
month of March, these rivers togeth-
er contributed an average of 160
thousand cubic feet per second over
a 16 year period according to a 1968
U.S.G.S. report (See Figure 7).
This number is about 80 times
greater than the same contribution
during September.
How does this massive difference in
freshwater inflow during the spring
affect circulation? In the major
rivers on the western side of the
Bay stratification increases, and
the water will exhibit a more ob-
vious two-layered flow with a dis-
tinct halocline. The zone of maxi-
mum turbidity will shift downstream,
widening spawning grounds in those
rivers. However, at the same time,
vertical mixing decreases, limiting
the availability of nutrients and
oxygen to the water column.
Productivity will begin to decrease
and continue throughout the summer.
Certain parts of the northern tribu-
taries closest to the Bay may ex-
hibit a three-layered circulation
pattern at their mouths if the
freshwater inflow is great enough.
Water from the Susquehanna River,
for example, can cause this type of
Figure 6. Areas of maximum turbidity and where three-layered flow
in the Bay is possible.
flow pattern in Baltimore Harbor
(See Figure 8). In this situation,
freshwater from the river flows into
Patuxent
River )
Choptank
' River
Potomac.
York
River
Susquehanna River
Patapsco
River
West River
Chester River
Nanticoke
River
Rappahannock
River
Wicomico
River
*
Cape
Charles
Zone of Maximum
Turbidity
O Possible
RiUver°
Pokomoke
River
James River
Cape
Henry
River
-------
6.
I | E Mouth of Chesapeake Bay
] D Above James River
M C Below Potomac River
I | B Above Potomac River
I | A Mouth ot Susquehanna River
160- r-
140- —
120
100-
80-
60-
J FMAMJ JASON D
Source: Monthly Surface Water Inflow to the
Chesapeake Bay, USDOI, Geological
Survey, Water Resources Division,
Arlington, VA, October 1968,
by Conrad d. Bue
Figure 7. Typical seasonal freshwater inflow showing relative input at various locations in the Bay.
the Harbor in an upper layer,
looping outward via a middle
section. Because flushing action
from this pattern is very slow,
Baltimore Harbor can act as a sink,
trapping material within it.
During the autumn, freshwater in-
flow, barring storms, is drastically
lower. Zones of maximum turbidity
shift upstream, narrowing spawning
grounds as well as reducing the
amount of water over spawning beds.
Potuxent
River )
Choptank
' River
Potomac.
Patapsco
River
Susquehanna River
Chester River
wunpowder
River
Nanticoke
River
Rappahannock
River
Wicomico
River
Pokomoke
River
James River
. Cape
Charles
Cape
Henry
West River
River
Scale 1:1,470,000 approx.
0 10 20 mi.
1 i i i
-------
7.
Partly for this reason, most of the
Bay's anadramous fish travel up-
stream to spawn during late winter
and early spring. Vertical mixing
also increases during the fall, and
more nutrients and oxygen become
available to enrich the water column.
The seasonal circulation patterns
described here, and the resulting
effects on nutrients are natural
fluctuations. Accelerated enrich-
ment from human activity has unknown
effects on these intricate inter-
actions. Studying circulation will
help us understand the pathways and
effects of pollutants, and thus,
what limits we may have to impose on
sources contributing pollutants to
the Bay.
Fresh Water
Figure 8. Three-layered flow pattern showing a freshwater upper
layer and salty lower layer flowing inward and flushing outward
through a middle, brackish layer.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management implications of the Chesapeake Bay
Program, a project of the U. S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
Author: Elizabeth Macalaster, Editorial Assistant: Dottle Van Doren
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
Citizens Program for the
Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Salt Water
-------
summary z
EPA
Chesapeake
Bay Program
Information
Series
Toxics
Sediment-Animal Relationships
August 1980
Importance
The sediments of the Bay contain a
variety of nutrients, minerals, decay-
ing organic matter, and, possibly,
toxic chemicals. The benthic, or
bottom-dwelling, organisms mix these
sediments, much as earthworms mix the
earth of a flower garden. Such organ-
isms play a vital role in the exchange
of materials, including toxic com-
pounds, within the sediments and
between the sediments and Bay waters.
To better understand the complex rela-
tionships between sediments and the
organisms that inhabit them, two of
the organizations sponsored by the
Chesapeake Bay Program are conducting
companion studies in Maryland and
Virginia. This research summary, which
is one of a series of publications
describing Chesapeake Bay Program
research, presents the preliminary
findings of these sediment-animal
studies.
Research
The main objectives of the research
are to:
—Investigate the diversity and abun-
dance of benthic organisms and the
types of sedimentary structures,
such as burrow tubes, that they
create.
—Determine the relationships among
species of organisms found, sediment
types, and pollutant concentrations.
-Diagram in three-dimensional fashion
the benthic environment, to illus-
trate the distribution of benthic
organisms and their mixing opera-
tions.
-Assess the impact of the benthic
animals on the exchange of materials,
in particular toxic materials, be-
tween the sediment and the water.
Box-core samples, which provide a
glimpse of the vertical profile of the
benthic environment, were collected at
65 Bay-wide sampling sites, 25 in
Virginia and 40 in Maryland. Once
these samples were taken, the box
cores were dissected, and radiographic
(x-ray), biological, grain-size, and
carbon analyses were done. From these
analyses, several observations have
been made.
The Virginia researchers found benthic
organisms in sediment as deep as the
longest box cores collected (24 inches
or 60 centimeters). However, animals
are seldom found deeper than 12 inches
(30 cm.). This finding suggests that
benthic organisms mix surface sedi-
ments into deeper layers that were de-
posited up to 100 years earlier,
depending on local sedimentation rates
and depth of burrowing. Most organisms
are concentrated in the upper few cen-
timeters of sediment. Differences in
densities and vertical distributions
-------
of organisms were found between sam-
pling periods, reflecting characteris-
tic seasonal fluctuations. A micro-
scopic examination of sediment
particles was also undertaken to
describe and quantify their form and
size, and to determine the presence
of organic carbon and sulfur.
The radiographic analysis identified
the organisms responsible for the
structures observed. Examples of the
organisms identified include blood-
worms and other polychaetes, molluscs,
and certain crustaceans.
Information collected is used to con-
struct three-dimensional drawings to
represent the sediment community. Spe-
cific organisms and their burrow sys-
tems will be illustrated to show the
diversity of sedimentary structures.
An example of a three-dimensional
drawing is presented in Figure 1.
Data on depth distribution, feeding
types, and habitat preference of com-
mon organisms found in the box cores
are presented in Table 1. The wide
range of species' characteristics in-
dicates the variety of niches in the
sediment community.
Preliminary results of the projects
show that:
—Biologic activity in the bottom
sediments is much reduced in high-
energy environments, such as the
near-shore, because of wave and
current action.
—From the Susquehanna Flats to the
mouth of the Bay, a gradual increase
in numbers of biogenic structures
is observed. As salinity increases,
there is a corresponding increase
in the number of types of organ-
isms in the sediment.
—In deeper areas of the Bay, few
burrows and tubes were found, be-
cause deeper areas of the Bay lack
oxygen at certain times of the
year.
—The density of organisms and the
diversity of sedimentary struc-
tures are reliable indicators of
chemical exchange rates between the
sediment and the water,
—Benthic animals inhabit Chesapeake-
Bay sediments to at least 2b
inches (60 cm); however, most
organisms are located in the top
4/5 inch (2 cm).
—The density of organisms and their
vertical distribution change season-
ally. These fluctuations signifi-
cantly affect the distribution of
chemicals in the sediments.
tary structures and benthic organisms
Credit: Eli Reinharz,
Marylawi Geological Survey
Figure 1. Three-dimensional diagram of sedimen-
-------
TABIE 1. Characteristics of Some Benthic
Organisms Found in the Chesapeake Bay-
Depth
Distri- Feeding Sedimentary Habitat
bution Type Structures Preference
Mollusks
Busycon carica
(Whelks)
Anadara transversa
(smallnon commer-
cial salt water
clam)
Macoma balthica
(Baltic macoma)
small non commer-
cial salt water
clam)
Annelids (segmented
worms)
Clymenella torquata
surface
to 1.2 in.
3 cm
surface
0-8 in.
0-20 cm
carnivore
0-10 in.
0-25 cm
furrows left from
plowing action
feeds on suspended obvious fecal pel-
plants and animals lets, sometimes
in the water
selective bottom
feeder, or sus-
pension feeder
sub-surface
selective bottom
feeder
left in piles
fecal pellets -
5.84 kg sed/m^
vertical sand tubes
for transport of 02
and food - 168.5
liters/m^/yr
sand-higher
salinities
euryhaline (a wide
range of salinities)
silty clay to medi-
um sand
all sediment types
but prefers finer
types
silty fine sand to
medium sand
Loimia medusa
0-16 in. selective bottom
0-40 cm sediment feeder
using tentacles
on surface
U-shaped sand tube fine sediments
Nereis succinea
(bloodworm)
0-6 in. omnivorous
0-15 cm forager, non-
selective bottom
sediment feeder
burrower, producing
fecal mounds
wide range
Pectinaria gouldii
0-2.4 in.
0-6 cm
selective sub-
surface feeder
using tentacles
to sort food
mobile tube dweller,
carrying tube along
with it - reworks
6 g sed./worm/day
silt-fine sand
Crustaceans
Ampelisca abdita 0-1.2 in.
(amphipod) 0-3 cm
selective surface
feeder using an-
tennae to scrape
along surface
tube dweller whose
numbers can become
so great as to sta-
bilize sediment,
increasing the sed-
imentation rate
fine sediments
Upogebia affinis 0-8 in.
(mud shrimp) 0-20 cm
suspension feeder burrower
muddy sand
Adapted from: Borsch, D.F. and Karl J. Nilsen, "The Biogenic Structure of Chesapeake Bay
Sediments" EPA Chesapeake Bay Program, Trimester Report - 15 September 1979
-------
—The greater the abundance and di-
versity of biogenic structures,
the greater the exchange rates be-
tween bottom sediments and water
will be.
In summary, the information gathered
to date from these projects has re-
sulted in knowledge concerning:
—benthic community structure,
—seasonal variations.
—variability of sedimentary struc-
tures down the Bay, down the sed-
iment column, and between sediment
types.
—sedimentary structures produced by
each species.
Management Implications
This project will provide information
on the relationship between benthic
organisms and toxic materials in
sediments, in addition to particle
size, sediment type, organic and
total carbon, sulfur, and water-
content correlations.
The information gathered may identify
sites where toxic materials are being
mixed throughout the sediments. Since
benthic organisms cause vertical mix-
ing, they can distribute toxic sub-
stances that have settled on the
bottom throughout the sediments and
back into the water column.
This is one of a series of briefs,
reports, research summaries, and final
project reports designed to make avail-
able the findings, observations, and
management implications of the Chesa-
peake Bay Program, a project of the
U. S. Environmental Protection Agency.
It is based on conversations with the
principal investigators and on the
final reports covering these projects.
In general, the animal-sediment
studies will provide basic informa-
tion that may aid in the development
of toxic-substances policies. For
instance, the identification of areas
with potentially high toxic-chemical
content would be useful in desig-
nating areas for commercial shellfish
operations. Knowledge of the estuarine
environment of the Bay bottom would
also help assess the impact of dredge
material disposal on benthic communi-
ties o Care samples with no benthic
animals or sedimentary structures,
for example, might point to a dead
area, which may have been harmed by
dredge material, or a core full of
benthic animals and structures from a
once dead area would indicate where
communities have recolonized.
These kinds of data provide a basis
for future comparisons of the distri-
bution and abundance of benthic
organisms. Such population trends may
serve as an important indicator of
the Bay's health.
This summary highlights the research
findings from two ongoing projects
sponsored by the Chesapeake Bay
Program: Chesapeake Bay Earth Science
Study - Animal-Sediment Relationship
(Maryland) - (Principal Investigator,
Dr. Owen P. Bricker, Maryland
Geological Survey) and The Biogenic
Strueture of Chesapeake Bav Sediments
(Virginia) - (Principal Investigator,
Dr. Donald F. Boesch, Virginia
Institute of Marine Science).
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21^01
301/266-00?7
or
Citizens Program for the Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
-------
summary 3
EPA
Chesapeake
Bay Program
Information
Series
SAV
Light and Decline
of Bay Grasses
August 1981
Importance
Survival of submerged aquatic vega-
tation (SAV) in the Bay relies
largely on the availability of
light. Unlike their terrestrial
neighbors, these aquatic plants are
submerged in a watery medium which
dissolves, suspends, transports, and
deposits a wide assortment of sub-
stances. The dissolved and sus-
pended materials reflect and absorb
light as it passes through the water
prior to reaching the plant. In
comparison to land plants, then, SAV
receives limited amounts of light,
making light a major factor in con-
trolling its growth and distribu-
tion. This requirement is why SAV
lives primarily in the shallow
waters of the Bay.
Ordinarily, sunlight is the source
of energy for photosynthesis, the
process in plants during which car-
bon dioxide and water combine to
form glucose, releasing oxygen as a
product. Light from nearly all of
the radiant energy spectrum (x-ray
to infrared) is effective in photo-
synthesis. Leaves commonly absorb
about one half of the total radiant
energy to which they are exposed
(including about 80% of the visible
light), but only a small fraction of
the absorbed light energy is changed
by photosynthesis into potential
chemical energy for the production
of food. Thus, the efficiency with
which SAV utilizes the quantities of
light is very important to its sur-
vival .
Fluctuations in populations of Bay
grasses have always existed; but
radical declines of all species in
the early 1970's brought attention
to these valuable grasses and led to
intensive studies by researchers in
both Maryland and Virginia under the
U.S. Enivronmental Protection
Agency's Chesapeake Bay Program.
Part of the Program's research has
focused on causes of the decline
including climatic changes, light
reductions, and increased herbicide
usage. Because of the important
role light plays in the growth of
Bay grasses, several studies on
light are being conducted. By
understanding how light and other
environmental factors control the
growth and survival of SAV, scien-
tists can understand the underlying
factors causing populations to fluc-
tuate. Effective management pro-
grams to improve detrimental condi-
tions, such as reduced light avail-
ability, can then be implemented.
This research summary is one in a
series of publications describing
Chesapeake Bay Program research. It
highlights research projects to date
by W. Michael Kemp, et al., at
University of Maryland's Horn Point
Laboratory and Chesapeake Biological
Laboratory, Robert L. Wetzel, et
-------
2.
al. , and Robert J. Orth, et al., at
the Virginia Institute of Marine
Science in Gloucester Point,
Virginia.
Research
Scientists in the Bay area have sug-
gested that reduced light conditions
could be partly responsible for the
recent decline in SAV. These re-
searchers are conducting several
studies on how the quantity of light
affects growth of SAV. Three rea-
sons for reduced growth of SAV are:
1. SAV is very sensitive to light.
2. Suspended solids (turbidity)
reflect light.
Bath
Water-Level
Plexiglass
Cylinder
Plastic
Pot
Cylinder
Water-Level
Aquatic Plant
Rooted In
Sediments
Pedestal
Stir-Bar
Magnetic
Stirrer
3. Colonies of epibiota (filter-
feeding plants and animals) on
leaves reflect light.
1. Sensitivity Experiments
To test the first hypothesis, re-
searchers at the University of
Maryland's Horn Point Laboratory
conducted experiments on two
dominant species of SAV, Potamogeton
perfoliatus (redhead grass) and
MyriophyHum spicatum (Eurasian
watermilfoil). The plants were
rooted in styrofoam cups containing
estuarine sediments and grown in
chambers. See Figure 1. Each cham-
ber was covered with a shroud of
different combinations of screens,
allowing the researchers to simulate
a wide range of light conditions—
from 8.8 to 100 percent of incident
light (light that falls on some-
thing). Outdoor measurements were
made using a similar setup. Hourly
rates of photosynthesis were estima-
ted by measuring changes in concen-
tration of dissolved oxygen, a pro-
duct of photosynthesis, in the tanks.
Responses to varying quantities bf
light by the two SAV species follow-
ed a hyperbolic curve (shown in Fig-
ure 2) where with increasing light,
Figure 1. Diagram of experimental chamber for measuring light-
manipulated rates of photosynthesis. Several of those cylinders sit
in a water bath.
Source: Kemp, W. M., J. C. Stevenson, W. R. Boynton, and J. C.
Means, Submerged Aquatic Vegetation in Chesapeake Bay:
Its Role In Bay Systems and Factors Leading to its
Decline. U. S. Environmental Protection Agency,
Chesapeake Bay Program. Cooperative Agreement No.
R805932, February 1981.
photosynthesis rapidly increases,
then levels off. The saturation
level, the quantity of light at
which the plants approach their max-
imum photosynthetic capabilities,
begins for both species at about 600
microeinsteins (a unit measuring
light quantities). But at this
point, watermilfoil produced more
oxygen, at nearly four milligrams of
oxygen per gram of plant per hour (4
mg 02(g plant)~lh~l), compared
with three mg02(g plant)~lh~l
for redhead grass. Thus, water-
milfoil shows greater photosynthetic
capabilities and would probably
survive better in low light
conditions. The steep, initial
slope of both curves shows that a
slight change in quantity of light
causes a large change in photo-
synthetic rate, indicating that
-------
3.
Pmax
Pmax
Eurasian Watermilfoil
Redhead Grass
Light Intensity, In Microelnsteins tyAEin m~2 sec-1)
Figure 2. Photosynthetlc responses of two submerged grasses to changing light conditions.
Source: Kemp, W. M., J. C. Stevenson, W. R. Boynton, and J. C. Means, Submerged Aquatic Vegetation
lr. Chesapeake Bay: Its Role In Bay Systems and Factors Leading to its Decline. U.S. Environmental
Protection Agency, Chesapeake Bay Program. Vol. 1 Cooperative Agreement No. R805932, February 1981.
these two species are very sensitive
to decreases in light levels.
At the Virginia Institute of Marine
Science (VIMS), similar baseline
experiments on light levels are
being conducted in the field using
plexiglass dome enclosures. (See
Figure 3). By monitoring the dis-
solved oxygen concentrations in each
dome scientists can calculate
the oxygen production and thus, the
photosynthetic rate of an entire SAV
community. Researchers have begun
Instrument package
Pumping station
4-point anchoring system
Figure 3. Dome enclosure used to measure photosynthetlc rate In SAV communities.
Source: Robert J. Wetzel, Virginia Institute of Marine Science
-------
shading experiments with these
domes, aiming to determine how sen-
sitive whole communities are to
light levels. Their results will
appear as curves, similar to those
done by the researchers at Horn
Point, but will show photosynthetic
capability for communities composed
of more than one species.
2. Turbidity Experiments
The direct effects of turbidity on
plant productivity were examined by
Horn Point researchers. Eelgrass
populations were grown in aquaria
using natural estuarine water and
sediments under fluorescent lights.
The researchers added high and low
doses of sieved sediments to the
colonies of eelgrass. Each day dis-
solved oxygen was measured at dawn
and dusk, and before and after sedi-
ment treatments.
Figures 4 and 5 show the results of
this experiment. Figure 4 shows the
effects of sediment addition on
light availability, with nearly
twice as much light available in the
untreated systems. The control sys-
tems (with just circulating water),
as the upper line in Figure 5 shows,
were also much more productive than
either the low or high dosed colo-
nies. The similar responses (lower
lines in Figure 5) of the plants to
both low and high doses of sediment
show a nonlinear response, sug-
gesting that plants are very sen-
sitive to a little turbidity, and
that after a certain concentration
continued introduction of sediments
does not further reduce plant pro-
duction. Using mathematical equa-
tions, the scientists project that
an increase in turbidity from 20 to
100 milligrams per liter could cause
a 50 percent reduction in available
light at 0.5 meter depth. Such
drastic increases in turbidity are
known to occur within hours fol-
lowing a widespread storm.
40 -
; 30-
untreated, or control colonies
low doses of sediment
20
.9 10 -
0
high doses of sediment
T
8
Time of Experiment in Days
Figure 4. Effects of sediment on availability of light to SAV.
1.5-
untreated, or control colonies
O
o>
1.0-
©
£
C
>
to
O
o
£ 05
c
®
o
a
a
< „
I
low doses of sediment
1
I I
s I \
z
I
high doses of sediment
Time of Experiment In Days
Figure 5. Photosynthetic response to sediment loading.
Source: Kemp, W. M., J. C. Stevenson, W. R. Boynton, and J. C.
Means, Submerged Aquatic Vegetation in Chesapeake Bay:
Its Bole in Bay Systems and Factors Leading to its
Decline. U. S. Environmental Protection Agency,
Chesapeake Bay Program. Vol. 1. Cooperative Agreement
No. E805932, February 1981.
3. Epibiota Experiments
Scientists at both Horn Point and
VIMS are investigating the effect of
fouling by plants and animals (epi-
bota) on light availability to SAV
-------
leaves. Researchers at Horn Point
hypothesize that nutrient enrichment
in the Bay causes increases in
phytoplankton and bacteria which
serve as food to fouling animals
such as barnacles, hydroids and
worms. These organisms, in turn,
are able to proliferate on SAV
leaves. Added to the colonies of
fouling animals are floral compon-
ents, such as diatoms and bacteria;
the total encrustation reduces light
available to the SAV.
From field studies, scientists found
differences in observed fouling
rates in different areas. Special
plates (used to collect fouling or-
ganisms) in open areas or on the
fringe of a grass bed, had fouling
rates 18 times greater than those
inside the bed. The researchers
believe that inside the bed, cur-
rents are baffled, or slowed, so
that less food reaches the epibiota
compared with other areas subject to
more active currents. Recruitment
of epibiota could also be greater in
the latter areas, where the currents
would carry more animals.
The Horn Point scientists are con-
tinuing these investigations with
more field and laboratory studies.
They plan to assess fouling rates of
epibiota in water at varying current
rates and at different nutrient
levels.
At VIMS, researchers are studying
the role of grazers on the epibiota
populations inhabiting blades of
eelgrass. Specifically, they have
been investigating the activities of
one grazer, a snail called Bittium
varium which feeds on epiflora
(plant component of epibiota) grow-
ing on eelgrass.
The VIMS scientists have used a
scanning electron microscope (SEM)
to study the effects of Bittium
grazing on eelgrass epibiota. Pre-
liminary studies from SEM photo-
graphs have shown that the grazing
of a single Bittium can be a signi-
ficant factor in reducing the plant
growth along its grazing trail (See
Figure 6 ). In laboratory experi-
ments, the researchers found that
blades with Bittium had 2-1/2 times
less epiphytic material (by weight)
than control blades (without
Bittium). It appears that Bittium
eats or bulldozes material off, or
to one side of the blade.
In the years preceding Hurricane
Agnes, which struck the Bay in June
1972, Bittium was the most abundant
animal found on eelgrass. It has a
,A •/, • > . - &
• t A z. /~
Figure 6. Trail left by Bittium
grazing on blade of eelgrass. The
crust contains fragments of
diatoms, bacteria, blue-green
algae and organic debris.
Photo by: Jacques van Mont-
frans, Virginia Institute of
Marine Science.
-------
6.
life cycle of 1.5 years with the
release of young from eggs in June.
Hurricane Agnes caused a drastic and
sudden decrease of salinities in
eelgrass beds at that time and may
have killed the entire one-year
class of Bittum that had just
hatched. Thus, the decline of the
grass in 1973 was possibly due to
absence of a dense grazing popula-
tion which under normal conditions
would have kept eelgrass relatively
clear of epibiotic growth. Combined
with the usual summertime depression
of available light from increased
turbidity, the VIMS scientists hypo-
the size that the plants were unable
to photosynthesize efficiently. The
absence, or reduced abundance of
Bittum in lower western shore eel-
grass beds, to this day, may be the
reason why eelgrass beds have not
expanded as rapidly as they could.
The VIMS researchers will center
future experiments on Bittium's tol-
erance to salinity; the effects of
different Bittium densities on eel-
grass; and the grazing effect by a
single concentration of Bittium on
eelgrass exposed to varying reduc-
tions of sunlight.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management implications of the Chesapeake Bay
Program, a project of the U. S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
For more information, contact:
EPA Chesapeake Bay Program or
2083 West Street
Annapolis, MD 21401
301/266-0077
Citizens Program for the
Chesapeake Bay
6600 York Road
Baltimore, MD 21212
301/377-6270
Author: Elizabeth Macalaster, Editorial Assistant: Janet Malarkey
-------
summary 3
EPA Toxics
Chesapeake Investigation of Organic Pollutants
Bay Program
Information September 1980
Series
Importance
Production of synthetic organic
chemicals has increased considerably
since the Second World War. More
than 1,000 new chemicals are
introduced into the environment each
year. Many, including some
pesticides, plastics, and synthetic
fibers, offer enormous public
benefits. Others, such as PCB's,
are extremely harmful, and the
toxicity of many more synthetic
chemicals remains unknown. Despite
the lack of understanding of these
chemicals' effects, many toxic
synthetic organics enter the envi-
ronment through misuse, ignorance,
willful discharge or spills.
Once they enter the natural
environment, toxic chemicals can
directly harm plants and animals by
damaging certain body organs and
interfering with metabolic
pathways. Or, they can accumulate
in food chains. Within the food
chain, specific animals, especially
clams and oysters, can store up
toxic chemicals in their bodies to a
level where the animals become unfit
for human consumption.
The accumulation of toxic organics
in food chains, and their
potentially adverse ecological and
human health impacts are a primary
concern of the Chesapeake Bay
Program. In response to this
concern, scientists are collecting
data on levels of organic compounds
in the Chesapeake Bay. The data
will include compounds which have
been designated as toxic, as well as
those which have not yet been
categorized as toxic or non-toxic.
This summary, one of a series of
publications describing Chesapeake
Bay Program research, will summarize
findings to date of a two-year
toxics research project headed by
Dr. Robert J. Huggett at the
Virginia Institute of Marine Science
(VIMS) at Gloucester Point,
Virginia. The major goal of this
project is to design and demonstrate
a scheme for detecting, identifying
and locating man-made organic
compounds in the Chesapeake Bay.
Management agencies will be able to
use this system to monitor the
health of the Bay and control
discharges of toxic substances.
Research
Toxic organic chemicals can
accumulate in sediments, in the
tissues of aquatic organisms, and
sometimes in trace amounts in
water. Scientists at VIMS are
collecting samples of sediment,
water and organisms at sites
throughout the Bay, and each sample
is being analyzed to determine what
organic compounds are present.
-------
2.
To collect sediment samples, the
VIMS scientists used a
Smith-Mclntyre grab (Figure 1) and
sampled at 54 sites located at
mouths of major tributaries and at
deeper sites in the Bay (Figure 2).
Figure 1. Smith-McIrityre Grab
The two molluscs chosen for sampling
were Crassostrea virginica, the
American oyster, and Rangia cuneata,
a brackish water clam. The VIMS
scientists collected these molluscs
at 23 sites using either tongs or
dredging methods. They chose to
sample molluscs over other animals,
since individual bivalves move very
little, and thus, the pollutant
concentrations they exhibit reflect
specific areas.
Water samples were collected with
Keminerer bottles (brass tubes which
open and close at both ends) at 36
sampling stations. The sites were
located at major tributary mouths
draining into the Bay, along the
James River, and near suspected
sources of toxic compounds (power
Maryland
CHESAPEAKE BAY
SCALE m MILES
Figure 2. Sediment, Mollusc and Water
Sampling Sites
plants, sewage treatment plants and
industries). (Figure 2)
-------
3.
Analytical Approach
Sediment and Mollusc Samples
Scientists at VIMS are using a
variety of analytical tools to
determine what organic compounds are
present in the samples. Among these
tools are high resolution Glass
Capillary Gas Chromatography, Gas
Chromat ography-Mas s Spect rometry,
High Performance Liquid
Chromatography and Gel Permeation
Chromatography. All of these
instruments are specifically
designed or modified to work with
complex organic mixtures. Each has
a specific function in the
analytical scheme.
So far, the scientists have analyzed
60 to 70 samples and will complete
at least another 100 by the end of
the project. At $500 to $5,000 per
sample, analysis is expensive.
However, monetary costs become
negligible in the face of the
potential environmental losses
created by the presence of synthetic
organics in the Chesapeake Bay.
Literally thousands of organic
compounds exist in almost every
sample; identifying individual
substances would be nearly
impossible without running the
samples through many separations.
Figure 3 shows the basic scheme
involved in identifying organic
compounds. The VIMS team begins
separating the samples by removing
as many organic compounds as
possible. Since living things are
composed of organic molecules, many
naturally-occurring organics are
also removed in the process.
Separating the natural from the
man-made ones is partially achieved
by using one of the instruments, the
Gel Permeation Chromatograph. The
Liquid Chromatograph then separates
the samples into three parts, each
containing organics with similar
characteristics.
GEL
PERMEATION
CHROMATOGRAPH
CARBON STRUCTURE REVEALED
ORGANICS
WITH
SIMILAR
CHARAC
PHENANTHRENE
SOME KNOWN TOXICS / J
IDENTIFIED
DATA ON UNIDENTIFIED
COMPOUND STORED IN
COMPUTER
oo
Figure 3. Identifying Organic Compounds
-------
4.
In the next step, the scientists
begin identifying the compounds in
each of these parts. The Gas
Chromatograph separates many of the
compounds from one another and
estimates amounts of each present.
Designated toxic synthetic organics
are tentatively identified in this
step. Figure 4A is an example of
the output from a Gas
Chromatograph. Each peak, or
signal, such as Peak A, corresponds
to at least one organic compound
found in this sediment sample.
Scientists complete the
identification of the samples by
using the Mass Spectrometer. This
instrument breaks down the compounds
in each sample so that their carbon
structure is revealed. Figure 4B
shows a mass spectrograph of
phenanthrene, the compound labeled
Peak A in the Gas Chromatograph.
Phenanthrene
10 15 20 25 30 35 40
Figure 4A. Gas Chromatograph Showing Phenanthrene
45
50
Opil!jlBl{lUlJiDI|lUl|IUl|iUl|nii|iiii|[iii|mijllll|llll|llll| lll|llll|l! !jiill]iil'^il|illljl!ll|lllljl!ll[!llljlll!|llllj!ni|!IIi|!!!ljU!!JUIl|l!lljli;!^
0 50 100 150
200
Figure 4B. Mass Spectrograph of Phenanthrene
-------
5.
At this point, only some of the
organics are identified. Other
signals corresponding to compounds
not identified are stored in a
computer for later examination.
Since thousands of unidentified
compounds exist in a sample, the
researchers have developed a ranking
method to select those most
important for further
identification. The method utilizes
a special computer program which
searches the stored data and
addresses questions such as:
*—Do sampling locations exist where
particular compound or compound
type is present or absent?
—Do sampling locations exist where a
particular compound stands out?
—Do significant trends exist in the
composition or concentration of
these compounds over time?
A compound thus selected would then
undergo further analytical scrutiny
following a process similar to that
used for the separation of organic
compounds within the samples. This
selection method forms a crucial
component of the system for
monitoring the Bay's water quality.
When the Chesapeake Bay Program is
concluded, Maryland and Virginia
will receive the Gas Chromatograph—
Mass Spectrometer so that analysis
and monitoring of toxic substances
can continue.
Water Samples
The water samples are analyzed
utilizing a technique known as
"purge and trap." Briefly, the
water sample is placed in a tube
through which a gas bubbles. If the
sample contains any highly volatile
compounds, such as bromoform or
chloroform, they are stripped from
the sample by the bubbles and
collected in another tube containing
an absorbent. Finally, the com-
pounds are stripped from the
absorbent by heat and run through a
special gas chromatography procedure
which can detect halogenated
compounds.
Results to Date
The VIMS scientists have finished
the first part of their project, the
extraction, separation and
identification scheme. As new anu
better analytical techniques come
along, they will be incorporated to
constantly update the system.
The researchers have also analyzed
two separate samplings of sediments
and molluscs. Computer programs to
store and compare these data are
nearly completed, and comparisons of
samples have begun.
Separate water samplings have been
completed, and the scientists have
analyzed them for volatile
halogenated organics. These
organics are formed by the chlori-
nation of waste water containing
naturally-occurring organic matter.
Some of those identified include
chloroform, 1,1,1,-trichloromethane,
carbon tetrachloride, trichloro-
ethylene and bromoform. In general,
the concentrations found thus far
are less than 0.1 mg/L, the level
which the U.S. Environmental
Protection Agency set in 1978 as the
maximum allowable amount for trihal-
omethanes in drinking water. In a
few locations, for example in the
Potomac River near the Blue Plains
Power Plant, concentrations of some
organics were greater than 10 mg/L.
-------
6.
Management Implications
Toxic organic pollutants are in the
Chesapeake Bay—in the sediment, in
the water and in the animals.
Scientists have designated a few as
hazardous, while the toxicity of
most remains unknown.
Investigating organic pollutants in
the Bay will help scientists
identify what chemicals exist and
how much. The research will allow
scientists to select substances of
known toxicity for long term
monitoring. With further
modification of the techniques
developed by the VIMS scientists,
resource management agencies will be
able to conduct the monitoring
themselves.
At the end of their project, the
VIMS team will produce a map showing
where toxic compounds are found in
the Chesapeake Bay and where natural
sinks for these pollutants exist.
With the information gathered from
monitoring the compounds and from
these maps, managers can effectively
impose limits on certain substances
coming into the Bay, and thus,
ensure this great estuary's
integrity.
This is one of a series of briefs,
reports, research summaries, and
final project reports designed to
make available the findings,
observations, and management
implications of the Chesapeake Bay
Program, a project of the U.S.
Environmental Protection Agency. It
is based on conversations with the
principal investigators and on the
final reports covering these
projects.
For more information, contact:
EPA Chesapeake Bay Program
2083 West Street
Annapolis, MD 21401
301/266-0077
or
Citizens Program for the
Chesapeake Bay Program
6600 York Road
Baltimore, MD 21212
301/377-6270.
-------
summary 4
EPA
Chesapeake
Bay Program
Information
Series
SAV
Waterfowl and the
Decline of SAV
October 1981
Importance
The Chesapeake Bay is the most im-
portant wintering area in the
Atlantic Flyway for more than a mil-
lion and a half waterfowl. Since
settlers first reached the Bay's
shores, these birds have been known
across the country to both hunters
and birdwatchers. Of 45 species of
ducks, geese and swans native to
North America, about 30 migrate
through, or winter in the Bay area,
including Canada geese, whistling
swans, canvasback ducks, ruddy
ducks, common goldeneyes, redheads,
black ducks and mallards. The Bay
is attractive to waterfowl as a win-
tering habitat, because it provides
birds with broad shoal waters in
which to feed, protected rivers and
bays in which to rest, a mild winter
climate usually ice-free and abun-
dant natural food resources. In
addition to being a winter haven,
the Bay also forms an important link
in a chain of resting areas for
birds migrating farther south.
Large beds of Bay grasses have been
traditionally important to wintering
waterfowl as food. Among the impor-
tant species are widgeongrass,
(Ruppia maritima), wildcelery
(Vallisneria americana) and sago
pondweed (Potamogeton pectinatus).
But these food resources declined
radically during the 1970's, possi-
bly affecting the distribution and
abundance of waterfowl in the region.
Widgeongrass
Ruppia maritima
Wildcelery Sago Pondweed
Vallisneria americana Potamogeton pectinatus
Widgeongrass, wild celery and pondweed are some of the
Bay grasses eaten by waterfowl wintering in the Bay.
To determine any relationships be-
tween submerged aquatic vegetation
(SAV) and waterfowl, scientists at
the U.S. Fish and Wildlife Service's
Migratory Bird and Habitat Research
Laboratory in Laurel, Maryland, ex-
amined historic and current levels
of waterfowl and SAV populations,
primarily in Maryland. Their pro-
ject is part of the U.S. Environ-
mental Protection Agency's Chesa-
peake Bay Program SAV studies which
address, among other issues, the
ecological role and value of SAV in
the Bay. Learning more about water-
fowl population trends and how they
relate to the distribution and abun-
dance of SAV will help scientists
-------
2.
understand what ecological changes
can occur in the Bay when numbers
and kinds of SAV are altered.
Through these investigations, the
value of SAV, and thus the need to
control factors underlying its de-
cline will be better understood.
Research
Part of the waterfowl study involved
looking at feeding habits of ducks,
which can be divided into two kinds
of feeders—dabblers and divers.
Dabblers feed by dabbling at the
water's surface or tipping up in
shallow water. Historically, they
have been largely vegetation eaters
and include mallards, black ducks,
pintails and wigeons. Diving ducks,
such as redheads, canvasbacks, ruddy
ducks and common goldeneyes, have
small wings with legs set back on
their bodies, making walking diffi-
cult. Typically, they need open
water across which to run prior to
flight and cannot, therefore, feed
in dense marshes or agricultural
fields. These birds feed on a com-
bination of plant and animal food.
To examine relationships between
both kinds of feeders and pop-
ulations of SAV, the U.S. Fish and
Wildlife Service scientists first
looked at data from annual waterfowl
population surveys. Survey results
prior to 1972 gave measures of long-
term distributions and abundance of
waterfowl, while results from 1972
to 1980 described current Bay water-
fowl resources. The surveys were
conducted from planes which fly over
waterfowl concentrations during
December or January every year.
Observers in the plane estimated
number, species and location of
birds within established survey
areas. Because SAV stock is often
depleted during winter months, the
researchers performed additional
surveys in the autumns of 1978 and
1979 when more SAV was available.
Surveying Grasses:
The scientists also collected data
from SAV surveys. Over 600 sampling
stations of shoal water habitats
were established in 1971 to monitor
annual trends in Bay grass popula-
tions. Table 1 shows the percentage
of SAV within each waterfowl survey
area during the 1970's. By 1979 all
of the 21 areas had drastically de-
pleted stocks of important waterfowl
foods, such as widgeongrass, sago
pondweed and wild celery. For exam-
ple, 25.5 percent of the Lower Chop-
tank River sampling stations were
vegetated in 1971, but this number
fell to 12.8 percent in 1979. In
the Susquehanna Flats area, percent-
age of stations with SAV fell from
36.4 percent in 1971 to only 6.9
percent in 1979.
Using information from both surveys,
the scientists then compared and
statistically analyzed the distribu-
tion and abundance of birds relative
to SAV beds. They found some signi-
ficant relationships between water-
fowl and the decline of the Bay
grasses.
Results
Reductions in SAV had varying
effects on the distribution and
abundance of waterfowl throughout
the study period, depending on
whether or not the species changed
food preference during that time.
Of the dabbling ducks, the mallards
and blacks stayed and are found in
areas where SAV persists. Pintails
and wigeons wintered elsewhere dur-
ing this period. Among diving
ducks, those which did not adapt
their diet to an environment with
reduced SAV populations, tended to
leave the area. Most notable among
-------
3
Survey area*5
1 9
P a
r c e
n t
w 1 t
h
i < i
i i
1 ID 1
1 1
i a i
eta
t i a
i n ,
a n
d s
amp
i 1 e
s i
z e (
)
7 1 1
1 9
7 2
1 9
7 3
1 9
7 4
1 9
7 5
1 9
7 6
1 9
7 7
1 9
7 8 ;
1 9
7 9
lower Choptank Rlvar
25.5
(51)
20.8
(48)
14 . 9
(47)
14.3
(49)
0.0
(47)
21.7
(46)
8.2
(49)
6. 1
(49)
12.8
(47 )
Manokin, Annamassax R.
r.
F
(57)
12.7 (55) iJ.y CSTV 17.6 (34)
T.8
(52)
"TT
(55)
0. FT56)
Chester River
41.7
(36)
13.9
(36)
14.7
(34)
11.8
(34)
11.1
(36)
8 ! 6
(35)
16 .7
(36)
30.6-
(36)
22.2
(36)
Eastern Bay
2 1 .4
(28)
20.8
(24)
14.3
(28)
10.7
(28)
14.8
(27)
18.5
(27)
14.8
(27)
11.1
(27)
11.1
(27)
Smith Island (Maryland)
47 . 1
( 17)
27.3
(11)
25. 0
( 12)
23.5
( 17)
11.8
( 17)
17.6
( 17)
0.0
( 17)
5.9
( 17)
5.9
( 17 )
Bloodsworth, South Marsh I.
27 .5
(40)
13.6
(44)
8.7
(46)
7.0
(43)
0 . 0
(43)
0.0
(45)
0 . 0
(46)
0 . 0
(46)
0 . 0
(45)
Patapsco R., Aberdeen P.G.
1.9
(52)
0 . 0
(50)
2.0
(50)
3.8
(52)
4.5
(22)
1 . 9
(52)
7.7
(52)
3.8
(52)
5.8
(52)
Honqa River
30.0
(30)
23.3
(30)
3.3
(30)
3.3
(30)
3.4
(29)
3.4
(29)
0.0
(30)
3.3
(30)
0 . 0
(30)
Bayshora, Hooper Island
39.1
(23)
17.4
(23)
4.3
(23)
8.7
(23)
4.3
(23)
4.3
(23)
4.3
(23)
0.0
(23)
0.0
(23)
Maqothy - Severn Rivers
33.3
(27)
7.4
(27)
14 .8
(27)
14.8
(27)
( 0)
0.0
(25)
7.4
(27)
11.1
(27)
14.8
(27)
Susquehanna Fiats
36.4 (22)
0.0 (30)
0.0 (30)
6.7 (30)
6 17
(30)
0.0 (29)
0.0 <30)
0.0 (29)
6.9 (29)
Miles R i ver
12.5
( 8)
37.5
( 8)
12.5
( 8)
12.5
( 8)
25.0
( 8)
28.6
( 7)
25.0
( 8)
12.5
( 8)
0.0
( 8)
Wye River
9. 1
(11)
36 .4
( 11)
18.2
(11)
36.4
(11)
9. 1
(11)
18.2
(11)
9. 1
(11)
9. 1
(11)
9. 1
(11)
little Choptank River
10.0
(30)
3.3
(30)
0.0
(30)
0.0
(30)
0.0
(30)
0 . 0
(30)
3.3
(30)
3.3
(30)
0 . 0
(30)
Upper Choptank River
11.1
( 9)
20.0
( 10)
0 . 0
( 10)
0.(b
-( 9)
0.0
(10)
0.0
( 10)
0.0
( 10)
0.0
( 10)
0 . 0
(10)
Fishing Bay
8 . 0
(25)
0 . 0
(25)
0.0
(25)
0.0
(25)
0 . 0
(24)
0.0
(25)
0 . 0
(25)
0 . 0
(25)
0 . 0
(24 )
Sassafras River
20.0
( 10 )
0.0
(10)
0 . 0
( 10 )
0.0
( 10 )
0 . 0
( 10)
0 . 0
( 10)
0.0
( 10)
0 . 0
(10)
0 . 0
(10)
Northeast# Elk, Bohemia R.
5.0
(20)
0.0
(23)
0.0
(23)
0.0
(23)
0.0
(22)
0.0
(22)
0 . 0
(23)
0 . 0
(22)
0 . 0
(23)
Bayshora, Kent County
8.3
( 12)
0.0
( 6)
0.0
( 12)
0.0
( 12)
0.0
( 12)
0.0
( 12)
0 . 0
( 12)
0.0
( 12)
0.0
( 12)
Patuxent River
0.0
(50)
0 . 0
(45)
0.0
(50)
2.0
(50)
0.0
(47)
0.0
(49)
0.0
(49)
0.0
(50)
0.0
(48)
Total
19.2
(624)
9.6
(613)
6.2
(629)
7.2
(6 10)
3.8
(552)
5.7
(628)
5.0
(638)
4.2
(636)
4.4
(63 1
''Data from the files of MBHRL, Laurel, Maryland.
^Frequency occurrence of SAV averaged over years, when multiplied by the extent of shoal habitat <<2.44 m at mlw) in an area,
determined the sequence of survey areas used above.
Table 1. Percent of survey sites covered with SAV during the years 1971 to 1979.
these ducks are Che redheads.
Scientists suggest that one reason
for not being able to switch to a
new food type is the inability of
these birds and others to consume
animal matter because of their gul-
let and bill shape. In contrast,
the canvasback can feed on animals
and has adapted to the situation by
changing its food preference to
clams. This species stayed and is
still found in relatively high num-
bers around the Bay.
Other waterfowl species developed
different feeding patterns and even
expanded their populations during
the study time. Canada geese and
whistling swans, for example, can
Whistling swans are common Bay waterfowl that have adapted to decreasing abundance of SAV by foraging on land.
(Photo by R.E. Munro)
-------
4.
forage on land and now take advan-
tage of the rich agricultural fields
around the Bay.
Although fewer waterfowl species
currently winter in Maryland, re-
searchers believe their numbers can
improve. Since formerly abundant
species still migrate annually
through the area, recovery of SAV
resources will help bring these
birds back.
This summary is one in a series of
publications describing Chesapeake
Bay Program research. It highlights
the research to date of Robert E.
Munro and Matthew C. Perry of the
U.S. Fish and Wildlife Service,
Migratory Bird and Habitat Research
Laboratory in Laurel, Maryland.
This is one of a series of briefs, reports, research
summaries, and final project reports designed to
make available the findings, observations, and
management Implications of the Chesapeake Bay
Program, a project of the U.S. Environmental
Protection Agency. It is based on conversations with
the principal investigators and on the final reports
covering these projects.
For more information, contact: Citizens Program for the
EPA Chesapeake Bay Program or Chesapeake Bay
2083 West Street 6600 York Road
Annapolis, MD 21401 Baltimore, MD 21212
301/266-0077 301/377-6270
Author: Elizabeth Macalaster, Editorial Assistant: Janet Malarkey
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