EPA 903-R-04-003
CBP/TRS 232/00
July 2004
Chesapeake Bay
NTRODUCTION
Cr
CaWinectes sap/dus
Fossil
Shark
Tooth
Chesapeake Bay Program
,4 Wdtershet/ Partnership
Oxyrhina desori
EPA Report Collection
Regional Center for Environmental Information
U.S. EPA Region HI
Philadelphia, PA 19103
-------
Note: This edition of Chesapeake Bay: Introduction to an Ecosystem is an update of the 1994 edition
and includes information through January 2004.
1994 Version
Editor
Kathryn Reshetiloff
Illustrations and Layout
Sandra Janniche
Reviewers
Richard Batiuk
Peter Bergstrom
Carin Bisland
Walter Boynton
Sherri Cooper
Eugene Cronin
Richard Everett
Douglas Forsell
Eileen Setzler-
Hamilton
Michael Hirshfield
Carl Hershner
Frederick Howard
Steven Jordan
Robert Lippson
Lori Mackey
Tamara McCandless
Kent Mountford
Kate Naughten
Robert Orth
Nita Sylvester
Christopher Victoria
\
Regional Center for Environmental Information
US EPA Region III
1650AichSt.
Philadelphia, PA 19103
2004 Update
Laura Pyzik
Jennifer Caddick
Peter Marx
Chesapeake Bay Progran
A Wafers/red Partnership
Recycled/Recyclable—Printed with Vegetable Oil Based Inks on Recycled Paper (30% Postconsumer)
Printed by the U.S. Environmental Protection Agency for the Chesapeake Bay Program
-------
Contents,
THE CHESAPEAKE BAY ECOSYSTEM 1
The Watershed 1
The Chesapeake Bay—An Important Resource 2
A Threatened Resource 3
GEOLOGY OF THE CHESAPEAKE 5
Geologic History 5
The Chesapeake Bay 5
Erosion and Sedimentation 6
WATER & SEDIMENTS 8
Water: Salinity, Temperature and Circulation 8
Suspended Sediments: Composition and Effects 10
Chemical Make-up: Composition and Dissolved Gases 11
HABITATS 14
Islands and Inlands 14
Freshwater Tributaries 14
Shallow Water 15
Open Water 15
LIVING RESOURCES & BIOLOGICAL COMMUNITIES 16
Wetlands 17
Underwater Bay Grasses 18
Plankton 20
The Swimmers 21
Life at the Bottom 22
FOOD PRODUCTION & CONSUMPTION 24
The Food Web 25
Direct and Detrital Pathways 26
PRESERVING THE CHESAPEAKE BAY: THE BIG PICTURE 28
Be Part of the Solution, Not Part of the Problem 29
For More Information 30
GLOSSARY OF TERMS 31
\'< :••• TJl1- Ai-v^r-J.rl
T.'.I-\ - •'. '•...-. xv iev Environmental
Uoi/ArJ
L" iliv^v-ip
-------
The Chesapeake Bay
Watershed
_ J Chesapeake Bay Watershed
-------
The Chesapeake Bay Ecosystem
The physical processes that drive the Chesapeake Bay
ecosystem sustain the many habitats and organisms
found there. Complex relationships exist among the living
resources of the Bay watershed. Even the smallest of crea-
tures plays a vital role in the overall health and production of
the Bay. Forests and wetlands around the Bay and the entire
watershed filter sediments and pollutants while supporting
birds, mammals and fish. Small fish and crabs find shelter
and food among lush beds of underwater Bay grasses. Unno-
ticed by the naked eye, phytoplankton and microzooplankton
drift with the currents, becoming food for copepods and
small fish. Clams and oysters pump Bay water through their
gills, filtering out both plankton and sediment. During the
fall and winter, waterfowl by the thousands descend upon the
Bay, feeding in wetlands and shallow waters. Bald eagles
and osprey, perched high above the water, feed perch, men-
haden and other small fish to their young. The spectrum of
aquatic environments, from freshwater to seawater, creates a
unique ecosystem abundant with life.
The relentless encroachment of people threatens the eco-
logical balance of the Bay. Approximately 16 million people
live, work and play in the watershed. Each individual
directly affects the Bay by adding waste, consuming
resources and changing the character of the land, water and
air that surround it. However, through the choices we make
every day, we can lessen our impact on the Bay's health. We
must nurture what scientist Aldo Leopold once called our
"wild rootage", a recognition of the fundamental connection
and dependency between society and the environment. As
advocates for the Bay and its many living resources, we can
preserve the Chesapeake for years to come.
The Watershed
The Chesapeake Bay receives about half its water volume
from the Atlantic Ocean. The rest drains into the Bay from an
enormous 64,000 square-mile drainage basin or watershed.
The watershed includes parts of New York, Pennsylvania,
West Virginia, Delaware, Maryland and Virginia and the entire
District of Columbia. Freshwater from springs, streams, small
creeks and rivers flows downhill, mixing with ocean water to
form the estuarine system. Soil, air,
water, plants and animals, including
humans, form a complex web of
interdependencies that make up the
ecosystem. The people living in the
Chesapeake watershed play an
important role in this ecosystem.
The activities and problems occur-
ring throughout the entire watershed
significantly impact the functions
and relationships of the Bay. We
must choose whether our role will
be destructive or productive.
BAY FACT
POPULATION: Chesapeake Bay Watershed
2020
(projected)
2000
1980
6 8 10 12
Millions of People
14
16
18
Chesapeake Bay Ecosystem
-------
Waterman handtonging
for oysters.
The Chesapeake Bay—
An Important Resource
BAY FACT
Through the years, residents and visitors alike
have found the Chesapeake Bay imposing, yet hos-
pitable. The Algonquin Indians called it "Chesepi-
ooc," meaning great shellfish bay. Spanish
explorers described the Bay as ". . . the best and
largest port in the world." Captain John Smith, an
English explorer, extolled, "The country is not
mountainous nor yet low but such pleasant plain
hills and fertile valleys . . . rivers and brooks, all running most
pleasantly into a fair Bay." All were impressed with its size,
navigability and abundance of wildlife and food.
Today, the Bay is still one of this country's most valuable
natural treasures. Even after centuries of intensive use, the Bay
remains a highly productive natural resource. It supplies mil-
lions of pounds of seafood, functions as a major hub for ship-
ping and commerce, provides natural habitat for wildlife and
offers a variety of recreational opportunities for residents and
visitors.
Oysters and blue crabs are famous Bay delicacies. From the
1950s to the 1970s, the average annual oyster catch was about
25 million pounds per year. Since the early 1980s, however, the
catch has declined dramatically due to over-harvesting, disease
and the loss or degradation of habitat. As for Bay blue crab har-
vesting, historically the Chesapeake has been the largest pro-
ducer of blue crabs in the country, contributing more than a
third of the nation's catch. In 2002, however, the Bay's blue
crab harvest was only 50 million pounds, well below the long-
term average of 73 million pounds. The states of Maryland and
Virginia have pledged to jointly manage the Bay's blue crab
Prtof to the late
\ 800s, oysters
were so abundant
that some oyster
reefs po$ed
navigational
hazards to boats.
harvests by reducing harvest levels by 15 percent.
Harvesting of soft-shelled clams and an extensive
finfish industry, primarily based on menhaden and
striped bass, round out the Chesapeake's commer-
cial seafood production. In 2001, the dockside
value of commercial shellfish and finfish harvests
was close to $ 175 million.
The hospitable climate, lush vegetation and
natural beauty of the Chesapeake have made it an
increasingly popular recreational area. Boating,
crabbing, swimming, hunting and camping are
major attractions. Both power and sail boating have grown
dramatically. In Maryland and Virginia, more than 447.000
pleasure boats and other personal craft were registered in 2002.
Sportfishing is another major recreational activity m the
Chesapeake region. It is estimated that more than one million
anglers travel to the Bay each year to fish off the shores of
Maryland and Virginia.
The Chesapeake also is a key commercial waterway, with
two major Atlantic ports located here, Hampton Roads and
Baltimore. The Hampton Roads Complex, which includes
Portsmouth, Norfolk, Hampton and Newport News, dominates
the mouth of the Bay, and ranks third in the nation for metric
tons of exports. At the northern end of the Bay, the Port of Bal-
timore is ranked fifteenth in volume of exports in foreign trade.
In all, these two ports handled more than 84 million metric
tons of both imports and exports in 2001. Both Baltimore and
Hampton Roads are near the coal-producing regions of
Appalachia, making them essential to exporting coal.
Shipbuilding and other related industries also depend on the
Bay. Industries and power companies use large volumes of
water from the Bay for industrial processes and cooling.
Chesapeake Bay: Introduction to an Ecosystem
-------
Perhaps the Chesapeake's most valuable function, yet
most difficult to put a price tag on, is its role as habitat
for living resources. The Bay and its surrounding
watershed provide homes for a multitude
of plants and animals.
Waterfowl and other birds migrating along the
Atlantic Flyway stop here, finding food and shelter in
coves and marshes. The Chesapeake is the winter home
for tundra swans, Canada geese and a variety of ducks,
including canvasbacks, pintails, scoters, eiders and ruddy
ducks. On average, nearly one million waterfowl winter
each year on the Bay. It is also a major nesting area
for the threatened bald eagle. The Bay region also is
home to the world's largest population of another
raptor, the osprey, with more than 2,000 nesting pairs.
The Chesapeake's tidal freshwater tributaries
provide spawning and nursery sites for several
important species of fish, such as white and yellow
perch, striped bass, herring and shad. During the
warmer months, numerous marine species,
including bluefish, weakfish, croaker, menhaden,
flounder and spot, enter the Bay to feed on
its rich food supply.
A Threatened Resource
The Chesapeake Bay, the largest
estuary in the United States, is part
of an extremely productive and
complex ecosystem. This ecosystem
consists of the Bay, its tributaries and the
living resources it supports. Humans also are a part of
this ecosystem. We are beginning to understand how our
activities affect the Bay's ecology. Growing commercial,
industrial, recreational and urban activities continue to
threaten the Bay and its living resources.
Overharvesting and loss of habitat threaten fish and shell-
fish species. These two factors, plus disease, have decimated
the oyster population. Excess sediment and nutrients endan-
ger the Bay's water quality. Hypoxia (low dissolved oxygen)
and anoxia (absence of dissolved oxygen) are particularly
harmful to bottom-dwelling (benthic) species. Chemical con-
taminants, particularly high in industrialized urban areas,
accumulate in the tissues of birds, fish and shellfish. Three
areas, known as Regions of Concern, where living resources
likely are being affected by chemical contaminants are the
Baltimore Harbor/Patapsco River in Maryland, the Anacostia
Canada goose
(Branta canadens/s)
BAY FACT
The Chesapeake is
fairly shallow. A
person six feet tall
could wade over
700,000 acres
of the Bay
without becoming
completely
submerged.
Canvasback
(Aythya valisineria)
Osprey
1 (Pandion haliaetus)
Great blue heron
(Ardea herodias)
Tundra swan
(Cygnus columbianus)
Chesapeake Bay Ecosystem
-------
River in the District of Columbia and the Elizabeth
River in Virginia.
To find the causes of and potential remedies for
these problems, it is necessary to see the Bay from
an ecological perspective. All too often we think of
ourselves as external to our environment and ignore
the many relationships that link people, other living
creatures and the surrounding habitat. If we ignore
these connections when seeking solutions to prob-
lems, more and greater problems may result.
For example, agricultural activities and residential develop-
ment increase the amount of sediment and nutrient-rich fertil-
izers entering the Bay through runoff. Water clarity is reduced
and rivers are silted in. Excess nutrients cause algal blooms that
block sunlight from reaching critical underwater bay grasses,
BAY FACT
known as submerged aquatic vegetation, or
SAV. As bay grass acreage declines, so does the
food, shelter and nursery grounds for many
aquatic species. Solutions to these environmen-
tal problems can only be effective if complex
relationships among all components of the
ecosystem also are considered.
When environmental problems are ap-
proached from an ecosystem perspective, both
living and non-living components are considered when
recommending solutions. A truly effective solution not only
corrects the problem, but avoids damaging other relationships
within the ecosystem. This approach makes problem-solving
a great deal more challenging, but leads to more effective
environmental management.
Chesapeake Bay: Introduction to an Ecosystem
-------
Geology of the Chesapeake
The Chesapeake Bay as we know it today is
the result of thousands of years of con-
tinuous change. The Chesapeake, less than
10,000 years old, continues to change.
Nature, like a dissatisfied artist, is con-
stantly reworking the details. Some modi-
fications enhance the Bay, while others
harm it. All affect the ecosystem and its
interdependent parts. Some changes are
abrupt, while others take place over such a
long time that we can only recognize them
by looking back into geologic history.
Humans are becoming more involved in
the reshaping process, often inadvertently
initiating chains of events that reverberate
through the Bay's ecosystem. Because our
actions can have devastating effects on the entire
system, it is essential that we develop an ade-
quate understanding of the Bay's geological
make-up and fundamental characteristics.
Geologic History
During the latter part of the Pleistocene
epoch, which began one million years ago, the
region that is now the Chesapeake was alter-
nately exposed and submerged as massive
glaciers advanced and retreated up and
down the North American continent. Sea
levels rose and fell in concert with glacial
contraction and expansion. The region still
experiences changes in sea levels, easily
observed over the duration of a century.
The most recent retreat of the
glaciers, which began about 18,000 years
ago, marked the end of the Pleistocene epoch
and brought about the birth of the Chesapeake
Bay. The rising waters from melting glaciers
covered the continental shelf and reached
the mouth of the Bay about 10,000 years
ago. Sea level continued to rise, eventually
submerging the area now known as the
Susquehanna River Valley. The Bay
assumed its present dimensions about 3,000
years ago. . This complex array of drowned
streambeds forms the Chesapeake basin
known today.
D3
Broad Ribbed scallop
(Lyropecten santamaria)
Turret snail (Turritella plebia)
Ark (Anadora stam/nea)
Shark teeth
1 (Otodus obliquus)
2 (Hemipristis serra)
3 (Oxyrhina desori)
The Chesapeake Bay
The Bay proper is approximately 200
miles long, stretching from Havre de
Grace, Maryland, to Norfolk, Virginia. It
varies in width from about 3.4 miles
near Aberdeen, Maryland, to 35 miles
at its widest point, near the mouth of
the Potomac River. Including its tidal
tributaries, the Bay has approximately 11,684
miles of shoreline.
Fifty major tributaries pour water into
the Chesapeake every day. Eighty to
90% of the freshwater entering the Bay
comes from the northern and western
sides. The remaining 10 to 20% is con-
tributed by the eastern shore. Nearly an
equal volume of saltwater enters the Bay
from the ocean.
On average, the Chesapeake holds more
than 15 trillion gallons of water. Although
the Bay's length and width are dramatic, the
average depth is only about 21 feet. The
Bay is shaped like a shallow tray, except
for a few deep troughs believed to be
remnants of the ancient Susquehanna
River. The troughs form a deep channel
along much of the length of the Bay.
This channel allows passage of large
commercial vessels. Because it is so
shallow, the Chesapeake is far more
sensitive to temperature fluctuations and
wind than the open ocean.
To adequately define the Chesapeake
ecosystem, we must go far beyond the
shores of the Bay itself. Although the
Bay lies totally within the Atlantic
Coastal Plain, the watershed includes
parts of the Piedmont Province and the
Appalachian Province. The tributaries
provide a mixture of waters with a broad
geochemical range to the Bay. These
three different geological provinces influ-
ence the Bay. Each contributes its mixture
of minerals, nutrients and sediments.
Geology of the Chesapeake
-------
THE CHESAPEAKE BAY_
Appalachian Province
Piedmont Plateau
Atlantic Coastal Plain
The Atlantic Coastal Plain is a flat, low land area with a
maximum elevation of about 300 feet above sea level. It is
supported by a bed of crystalline
rock, covered with southeasterly-
dipping wedge-shaped layers of
relatively unconsolidated sand,
clay and gravel. Water passing
through this loosely compacted
mixture dissolves many of the min-
erals. The most soluble elements
are iron, calcium and magnesium.
The Atlantic Coastal Plain
extends from the edge of the continental shelf, to the east, to
a fall line that ranges from 15 to 90 miles west of the Bay.
BAY FACT
More than
600 species are
fossilised in ike
sediments of
Catvert Cliffs
in Maryland.
This fall line forms the boundary between the Piedmont
Plateau and the Coastal Plain. Waterfalls and rapids clearly
/ j mark this line, which is close to Interstate 95. Here, the ele-
vation rises to 1,100 feet. Cities such as Fredericksburg and
Richmond in Virginia, Baltimore in Maryland, and the Dis-
trict of Columbia developed along the fall line taking
advantage of the potential water power generated by the
falls. Since colonial ships could not sail past the fall line.
cargo would be transferred to canals or overland shipping.
Cities along the fall line became important areas for
commerce.
The Piedmont Plateau ranges from the fall line in the
east to the Appalachian Mountains in the west. This area is
divided into two geologically distinct regions by Parrs
Ridge, which traverses Carroll, Howard and Montgomery
counties in Maryland and adjacent counties in Pennsylva-
nia. Several types of dense crystalline rock, including
slates, schists, marble and granite, compose the eastern
side. This results in a very diverse topography. Rocks of
the Piedmont tend to be impermeable, and water from the
eastern side is low in the calcium and magnesium salts.
This makes the water soft and easy to lather.
The western side of the Piedmont consists of sand-
stones, shales and siltstones, underlain by limestone. This
limestone bedrock contributes calcium and magnesium to
its water, making it hard. Waters from the western side of
Parrs Ridge flow into the Potomac River, one of the Bay's
largest tributaries.
The Appalachian Province lies in the western and north-
ern parts of the watershed. Sandstone, siltstone, shale and
limestone form the bedrock. These areas, characterized by
mountains and valleys, are rich in coal and natural gas
deposits. Water from this province flows to the Bay mainly
via the Susquehanna River.
The waters that flow into the Bay have different chemical
identities, depending on the geology of the place where the
waters originate. In turn, the nature of the Bay itself depends
on the characteristics and relative volumes of these con-
tributing waters.
Erosion and Sedimentation
Since its formation, the Bay's shore has undergone con-
stant modification by erosion, transport and deposition of
sediments. In this process, areas of strong relief, like penin-
sulas and headlands, are eroded and smoothed by currents
and tides, and the materials are deposited in other parts of the
Bay. Sediments may be deposited in channels. Sediments,
Chesapeake Bay: Introduction to an Ecosystem
-------
carried by the river currents, also are left at the margins of
the Bay and major tributaries, resulting in broad, flat
deposits of mud and silt. Colonization of these areas by
hydrophytic (water-loving) vegetation may stabilize the
sediments and wetlands can develop. Recently, however,
wetlands along shorelines have been retreating inland as sea
level has risen. The speed at which these actions progress
depends on numerous factors, including weather, currents,
composition of the affected land, tides, wind and human
activities.
Many of the islands that existed in the Bay during colonial
times are now submerged. Poplar Island, in Talbot County,
Maryland, illustrates the erosive forces continuing today. In
the early 1600s, the island encompassed several hundred
acres. Over the centuries, rising sea level eroded the perime-
ter of Poplar Island. Though still populated by the 1940s,
only 200 acres remained and the island had been cut in two.
Today, a chain of small islands is all that remains of the orig-
inal Poplar Island. Efforts are under way to stabilize the rem-
nant acres. In addition, the island's original landmass will be
rebuilt by creating marshes that will protect the island from
further erosion and provide a haven for birds and other
wildlife. In contrast, sedimentation also has altered the
landscape. By the mid 1700s, some navigable rivers were
filled in by sediment as more land was cleared for agricul-
ture. Joppatown, Maryland, once a seaport, is now more
than two miles from water. The forces of erosion and sedi-
mentation continue to reshape the details of the Bay.
POPLAR ISLAND: ISLAND EROSION
Mid-19th Century
725 acres
Late 1940s
200 acres
COACHES
ISLAND
V1
POPLAR
ISLAND
JEFFERSON
ISLAND
1993 Remnants
100-125 acres
COACHES
ISLAND
Geology of the Chesapeake
-------
Water & Sediments
Water . . . approximately 70% of the Earth's surface is
covered by it. It makes up about 80% of our total body
weight. Without it, we cannot live. Perhaps, because its pres-
ence is so pervasive in our lives, we tend to think of water as
uniform rather than a substance with extremely diverse char-
acteristics and properties.
In the natural environment, water is never pure. It tends to
hold other substances in solution and easily enters into vari-
ous chemical reactions. As the universal solvent, water is an
important environmental medium. Water normally contains
dissolved gases, such as oxygen, and a variety of organic
(containing carbon) and inorganic materials. The concentra-
tion and distribution of these substances can vary within a
single body of water. Add differences in temperature and cir-
culation, which can enhance or retard certain chemical reac-
tions, and the variety of possible water environments vastly
increases.
Of all bodies of water, estuarine systems offer the great-
est physical variability in water composition. An estuary,
according to the late oceanographer Donald W. Pritchard, is
a "... semi-enclosed body of water which has free connec-
tion with the open sea and within which seawater is measur-
ably diluted by freshwater from land drainage." Within an
estuary, freshwater mixes with saltwater, with each con-
tributing its own chemical and physical characteristics. This
creates a range of environments that support a wide variety
of plants and animals.
Water: Salinity, Temperature and Circulation
The distribution and stability of an estuarine ecosystem,
such as the Chesapeake Bay, depend on three important
physical characteristics of the water: salinity, temperature
and circulation. Each affects and is affected by the others.
SPRING
SALINITY
in parts per
thousand
AUTUMN
SALINITY
in parts per
thousand
Isohalines mark the salt content of surface water. The salinity gradient varies during the year
due to freshwater input: fresher during spring rains, saltier during the drier months of autumn.
Chesapeake Bay: Introduction to an Ecosystem
-------
ZONE OF MAXIMUM
TURBIDITY
Salinity is a key factor influencing the physical make-up
of the Bay. Salinity is the number of grams of dissolved salts
present in 1,000 grams of water. Salinity is usually expressed
in parts per thousand (ppt). Freshwater contains few salts
(less than 0.5 ppt) and is less dense than full ocean strength
seawater, which averages 25 to 30 ppt. This difference in
density causes salinity to increase with depth, and freshwater
to remain at the surface. Water with a salinity of greater than
0.5 ppt but less than 25 ppt is called brackish, meaning a
combination of saltwater and freshwater. Most of the water
in the Bay falls into this category.
Seawater from the Atlantic Ocean enters the mouth of the
Bay. Salinity is highest at that point and gradually decreases
as one moves north. Salinity levels within the Chesapeake
vary widely, both seasonally and from year to year, depend-
ing on the volume of freshwater flowing into the Bay. On a
map, isohalines, or salinity contours, mark the salt content of
surface waters. Because the greatest volume of freshwater
enters the Bay from northern and western tributaries, isoha-
lines tend to show a southwest to northeast tilt. The rotation
of the Earth also drives this salinity gradient. Known as the
Coriolis Force, it deflects flowing water to the right in the
Northern Hemisphere so that saltier water moving up the
Bay is deflected toward the Eastern Shore. Therefore, the
water near the Eastern Shore of the Bay is saltier than water
near the Western Shore.
Temperature dramatically changes the rate of chemical and
biological reactions within the water. Because the Bay is so
shallow, its capacity to store heat over time is relatively small.
As a result, water temperature fluctuates throughout the year,
ranging from 34 to 84 degrees Fahrenheit. These changes in
BAY QUOTE
".,, the tide is
also governed by
the wind. South-
east makes the
highest flood and
northwest the
lowest ebb."
Rev. Hugh (ones, 1697
water temperature influence when
plants and animals feed, reproduce,
move locally or migrate. The tem-
perature profile of the Bay is fairly
predictable. During spring and
summer, surface and shallow
waters are warmer than deeper
waters, creating two distinct tem-
perature layers. The turbulence of
the water can help to break down
this layering.
Just as circulation moves much-needed blood throughout
the human body, circulation of water transports plankton,
fish eggs, shellfish larvae, sediments, dissolved oxygen, min-
erals and nutrients throughout the Bay. Circulation is driven
primarily by the movements of freshwater from the north and
saltwater from the south. Circulation causes nutrients and
sediments to be mixed and resuspended. This mixing creates
a zone of maximum turbidity that, due to the amount of
available nutrients, is often used as a nursery area for fish
and other organisms.
Weather can disrupt or reinforce this two-layered circula-
tion pattern. Wind plays a role in the mixing of the Bay's
waters. Wind also can raise or lower the level of surface
waters and occasionally reverse the direction of flow. Strong
northwest winds, associated with high-pressure areas, push
water away from the Atlantic Coast, creating exceptionally
low tides. Strong northeast winds, associated with low-pres-
sure areas, produce exceptionally high tides.
Together, salinity, temperature and circulation dictate
the physical characteristics of water. The warmer, lighter
Water & Sediments
-------
The change in temperature and salinity divides the Bay into saltier bottom
water and lighter, fresher surface water. A blurry mixing layer, known as the
pycnocline, divides the two. Strong winds can pile surface water against one
shore of the Bay. To reestablish equilibrium, the bottom layer flows up into
shallower water.
30
freshwater flows seaward over a layer of saltier and denser
water flowing upstream. The opposing movement of these
two flows forms saltwater fronts, or gradients, that move up
and down the Bay in response to the input of freshwater. A
layer separating water of different densities, known as a pyc-
nocline, is formed. The pycnocline is characterized by inten-
sive mixing of these two layers. This stratification varies
within any season depending on rainfall. Stratification is usu-
ally highest in the spring as the amount of freshwater in the
Bay increases due to melting snow and frequent rain. Strati-
fication is maintained throughout summer due to the warm-
ing of surface waters.
In autumn, fresher surface waters cool faster than deeper
waters and sink. Vertical mixing of the two water layers
occurs rapidly, usually overnight. This mixing moves nutri-
ents up from the bottom, making them available to phyto-
plankton and other organisms inhabiting upper water levels.
This turnover also distributes much-needed dissolved oxygen
to deeper waters. During the winter, water temperature and
salinity are relatively constant from surface to bottom.
Suspended Sediments:
Composition and Effects
The waters of the Chesapeake and its
tributaries transport huge quantities of sedi-
ments. Although sediments are a natural
part of the Bay ecosystem, accumulation of
excessive amounts of sediments is undesir-
able because they can fill in ports and
waterways. This sedimentation process
already has caused several colonial sea-
ports, like Port Tobacco and Bladensburg,
Maryland, to become landlocked. As they
settle to the bottom of the Bay, sediments
can smother bottom-dwelling plants and
animals, such as oysters and clams. Sedi-
ments suspended in the water column cause
the water to become cloudy, or turbid,
decreasing the light available for underwa-
ter bay grasses.
In the upper Bay and tributaries, sedi-
ments consist of fine-grained silts and clays
that are light and can be carried long dis-
tances by the fresh, upper layer of water. As
they move into the Bay, the particles slowly
descend into the denser saline layer. Here,
the particles may reverse direction and flow
back up toward tidal tributaries with the
lower layer of water. As the upstream flow
decreases, the sediments settle to the bottom.
Sediments in the middle Bay are mostly made of silts and
clays and mainly are derived from shoreline erosion. In the
lower Bay, by contrast, the sediments are sandier and heavier
and result from shore erosion and inputs from the ocean.
Sediments drop to the bottom fairly rapidly, remain near their
original source and are less likely to be resuspended than
finer silts.
Sediments also can carry high concentrations of certain
toxic materials. Individual sediment particles have a large sur-
face area, and many molecules easily attach to them. As a
result, sediments can act as chemical sinks by absorbing met-
als, nutrients, oil, pesticides and other potentially toxic materi-
als. Thus, areas of high sediment deposition sometimes have
high concentrations of nutrients, persistent (long-lasting)
chemicals and contaminants, which may later be released.
PYCNOCLINE
SALT CONTENT
(parls/'thousand)
TEMPERATURE
(degrees Celsius)
10
Chesapeake Bay: Introduction to an Ecosystem
-------
DISSOLVED INORGANIC
COMPOUNDS IN
SEAWATER
(in parts per million)
TRACE ELEMENTS
.95 ppm
PURE WATER
CHEMICAL MAKE-UP
i
MINOR COMPONENTS
109.6 ppm
MAJOR COMPONENTS
Potassium Calcium Sulfate Magnesium Sodium Chlorine
380 ppm 400 ppm 885 ppm 1350 ppm 10,500 ppm 19,000 ppm
Chemical Make-up:
Composition and Dissolved Gases
Like temperature and salinity, the chemical composition
of the water also helps determine the distribution and abun-
dance of plant and animal life within the Bay. The waters of
the Chesapeake contain organic and inorganic materials,
including dissolved gases, nutrients, inorganic salts, trace
elements, heavy metals and potentially toxic chemicals.
Composition of Water
The composition of seawater is relatively constant from
place to place. Freshwater, however, varies depending on the
soil and rocks with which the water has come in contact.
Both fresh and saltwater contain many natural dissolved
materials from several sources. Microorganisms, such as
bacteria, decompose dead organisms and release compounds
into the water. Live organisms also release compounds
directly into the water. In addition, dissolved material enters
the Bay via its tributaries and the ocean.
Seawater also contains hundreds of trace elements that are
important in many biological reactions. For example, living
organisms require minute quantities of cobalt to make
vitamin B-12. Metals such as mercury, lead, chromium
and cadmium also naturally occur in low concentra-
tions. As you move down the Bay the composition of
the water follows the salinity gradients. Major con-
stituents include chlorides, sodium, magnesium, cal-
cium and potassium.
Dissolved salts are important to the life cycles of
many organisms. Some fish spawn in fresh or slightly
brackish water and must move to more saline waters as
they mature. These species have internal mechanisms
that enable them to cope with the changes in salinity.
Dissolved Gases
Dissolved oxygen is essential for most animals
inhabiting the Bay. The amount of available oxygen is
affected by salinity and temperature. Cold water can
hold more dissolved oxygen than warmer water, and
freshwater holds more than saline water. Thus, con-
centrations of dissolved oxy-
gen vary, in part, with both
location and time. Oxygen is
transferred from the atmos-
phere into surface waters by
diffusion and the aerating
action of the wind. It also is
added as a byproduct of pho-
tosynthesis. Floating and rooted
aquatic plants and phytoplankton
release oxygen when photosynthe-
sizing. Since photosynthesis re-
quires light, production of oxygen
by aquatic plants is limited to shallow water areas, usually
less than six feet deep. Surface water is nearly saturated with
oxygen most of the year, while deep bottom waters range
from saturated to anoxic (no oxygen present).
During the winter, respiration levels of organisms are rel-
atively low. Vertical mixing is good, and there is little salin-
ity or temperature stratification. As a result, dissolved
oxygen is plentiful throughout the water column. During the
spring and summer, increased levels of animal and microbial
respiration and greater stratification may reduce vertical
mixing, resulting in low levels of dissolved oxygen in deep
water. In fact, deep parts of some tributaries like the Patux-
ent, Potomac and Rappahannock rivers and deep waters of
the Bay's mainstem can become anoxic in summer. In the
autumn when surface waters cool, vertical mixing occurs and
deep waters are re-oxygenated.
BAY FACT
Due to a lack of
oxygen in the
water, hundreds
of blue crabs
may run out onto
land. This rare
phenomenon ts
(mown as a
"crab
Water & Sediments
11
-------
Minimal
Phosphorus &
Nitrogen Inputs
Excessive
Phosphorus &
Nitrogen Inputs
\ Healthy j
. Oyster Reef ,\i
:.; . . . Benthic Community W'£3mK
5 Barren
5V Oyster Reef
PP£ ;;: Lack of Benthic Community • •' '•,
•<;•'•'••'••' '• '•:/:--..-'..:-''••'.';. ''.- :-.'... ''"' •/ : :•.'.;' •.«"
Carbon dioxide, another dissolved gas, is important to the
well-being of the Bay's aquatic environment. It provides the
carbon that plants use to produce new tissue during photo-
synthesis and is a byproduct of respiration. Carbon dioxide
is more soluble in water than oxygen. Its availability also is
affected by temperature and salinity in much the same fash-
ion as oxygen.
Nitrogen and Phosphorus
Nitrogen is essential to the production of plant and animal
tissue. It is used primarily by plants and animals to synthe-
size protein. Nitrogen enters the ecosystem in several chem-
ical forms. It also occurs in other dissolved or particulate
forms, such as in the tissues of living and dead organisms.
Some bacteria and blue-green algae can extract nitrogen
gas from the atmosphere and transform it into organic nitro-
gen compounds. This process, called nitrogen fixation,
cycles nitrogen between organic and inorganic components.
Other bacteria release nitrogen gas back into the atmosphere
as part of their normal metabolism in a process called
denitrification. Denitrification removes about 25% of the
nitrogen entering the Bay each year.
Phosphorus is another key nutrient in the Bay's eco-
system. In the water, phosphorus occurs in dissolved organic
and inorganic forms, often attached to particles of sediment.
This nutrient is essential to cellular growth and reproduction.
Phytoplankton and bacteria assimilate and use phosphorus in
their growth cycles. Phosphates (the organic form) are pre-
ferred, but organisms will use other forms of phosphorus
when phosphates are unavailable.
In the presence of oxygen, high concentrations of phos-
phates in the water will combine with suspended particles.
These particles eventually settle to the Bay bottom and are
temporarily removed from the cycling process. Phosphates
often become long-term constituents of the bottom sedi-
ments. Phosphorus compounds in the Bay generally occur in
greater concentrations in less saline areas, such as the upper
part of the Bay and tributaries. Overall, phosphorus concen-
trations vary more in the summer than winter.
Nutrients, like nitrogen and phosphorus, occur naturally
in water, soil and air. Just as the nitrogen and phosphorus in
12
Chesapeake Bay: Introduction to an Ecosystem
-------
fertilizer aids the growth of agricultural crops, both
nutrients are vital to the growth of plants within the
Bay. Excess nutrients, however, are pollutants.
Sewage treatment plants, industries, vehicle
exhaust, acid rain, and runoff from agricultural, res-
idential and urban areas are additional sources of
nutrients entering the Bay. Nutrient pollution is the
number one problem in the Bay system.
Excess amounts of nitrogen and phosphorus
cause the rapid growth of phytoplankton, creating
dense populations or algal blooms. These blooms become so
dense that they reduce the amount of sunlight available to
underwater bay grasses. Without sufficient light, plants can-
not photosynthesize and produce the food they need to sur-
vive. Algae also may grow directly on the surface of bay
grasses, blocking light. Another hazard of nutrient-enriched
algal blooms comes after the algae die. As the blooms decay,
oxygen is used up in decomposition. This can lead to dan-
gerously low oxygen levels that can harm and even kill
aquatic organisms.
Besides nutrients, people add other substances to the
Bay's water, creating serious pollution problems. Heavy
metals, insecticides, herbicides and a variety of synthetic
products and byproducts can be toxic to living resources.
These contaminants reach the Bay through municipal and
BAY FACT
industrial wastewater, runoff from agricul-
tural, residential and urban areas and atmos-
pheric deposition.
This situation is improving. In many cases,
industrial wastewater is treated to remove
contaminants. The use of especially damag-
ing synthetic substances, like DDT and
Kepone, has been banned.
Since 1987, regional Bay restoration lead-
ers have worked together to reduce the
amount of nutrients flowing into the Bay and its rivers. In
2003, the six Bay watershed states, the District of Columbia
and the U.S. Environmental Protection Agency agreed to
steep cuts in the amount of nutrients flowing into the Bay
and its rivers.
The new nutrient reduction goals, or allocations, call for
Bay watershed states to reduce the amount of nitrogen flowing
into the Bay from the 274 million pounds in 2001 to no more
than 175 million pounds per year by 2010, and phosphorus
from 19.1 million pounds to no more than 12.8 million pounds
per year by 2010. When coordinated nutrient reduction efforts
began in 1985, 338 million pounds of nitrogen and 27.1 mil-
lion pounds of phosphorus entered the Bay annually. When
achieved, the new allocations will provide the water quality
necessary for the Bay's plants and animals to thrive.
Water & Sediments
13
-------
Habitats
The Bay provides food, water, cover and nesting or nurs-
ery areas, collectively known as habitat, to more than
3,000 migratory and resident wildlife species. All plants and
animals have specific habitat requirements that must be sat-
isfied in order to live and thrive. Food, temperature, water,
salinity, nutrients, substrate, light, oxygen and shelter
requirements vary with each species. These physical and
chemical variables largely determine which species can be
supported by a particular habitat.
As a highly productive estuary, the Chesapeake Bay pro-
vides an array of habitats. Habitat types range from hard-
wood forests of the Appalachian mountains to saltwater
marshes in the Bay. These habitats are influenced by climate,
soils, water, plant and animal interactions and human activi-
ties. Four major habitat areas are critical to the survival of the
living resources of the Bay.
Islands and Inlands
Lands near water sources support a multitude of species,
from insects, amphibians and reptiles to birds and mammals.
Streambanks, floodplains and wetlands form the
transition from water to land. These areas act as
buffers by removing sediments, nutrients, organic
matter and pollutants from runoff before these sub-
stances can enter the water. Forests and forested
wetlands are particularly important to waterfowl,
other migratory birds and colonial waterbirds.
Forested uplands and wetlands are nesting and
resting habitat for neotropical migratory birds.
These birds breed in the United States but winter in
Central and South America. Some neotropical
birds breed in the forests found in the Bay water-
shed. The Bay lies within the Atlantic Flyway, a
major migration route for neotropical migrants and
migrating waterfowl, and is a significant resting
area for birds.
Surrounded by water and cut off from most
large predators, Bay islands are a haven for
colonial waterbirds (terns and herons), waterfowl
(ducks) and raptors (osprey and bald eagles).
Islands also can protect underwater bay grasses and
shallow water areas from erosion and sedimen-
tation. However, islands themselves are eroding at
alarming rates, mostly due to sea level rise and the
erosive force of wind and waves.
Freshwater Tributaries
Within the Chesapeake Bay watershed, five major
rivers—the Susquehanna, Potomac, Rappahannock, York
and James—provide almost 90% of the freshwater to the
Bay. These rivers and other smaller rivers, along with the
hundreds of thousands of creeks and streams that feed them,
provide habitat necessary for the production of many fish
species. Anadromous fish spend their adult lives in the ocean
but must spawn in freshwater. Anadromous fish species in
the Bay include striped bass (rockfish), blueback herring,
alewife, American and hickory shad, shortnose sturgeon and
Atlantic sturgeon. Semi-anadromous fish, such as white and
yellow perch, inhabit tidal tributaries but also require fresh-
water to spawn.
While all of these species have different habitat require-
ments, all must have access to freshwater spawning grounds.
However, due to dams and other obstacles, many historical
spawning grounds are no longer available to fish. Fish not
only need access to spawning grounds but require good
stream and water quality conditions for the development and
14
Chesapeake Bay: Introduction to an Ecosystem
-------
BAY QUOTE
"I«somweri
place
more
survival of eggs and juvenile fish. Nutrients,
chemical contaminants, excessive sediment
and low dissolved oxygen degrade spawn-
ing and nursery habitat.
Shallow Water
Shallow water provides habitats for many J«»
life stages of invertebrates, fish and water- .>, o^k
fowl. Shrimp, killifish and juveniles of
larger fish species use bay grass beds, tidal
marshes and shallow shoreline margins as nursery areas and
for refuge. Predators, including blue crabs, spot, striped bass,
waterfowl, colonial waterbirds and raptors, forage for food
there. Along shorelines, fallen trees and limbs also give cover
to small aquatic animals. Even unvegetated areas, exposed at
low tide, are productive feeding areas. Microscopic plants
cycle nutrients and are fed upon by crabs and fish.
Open Water
Striped bass, bluefish, weakfish, American shad,
blueback herring, alewife, bay anchovy and Atlantic
menhaden live in the open, or pelagic, waters of the
Bay. Although unseen by the naked eye, microscopic
plants and animal life (plankton) float in the open
waters. These tiny organisms form the food base for
many other animals. Hundreds of thousands of win-
tering ducks, particularly sea ducks like scoters, old-
squaw and mergansers, depend on open water for the
shellfish, invertebrates and fish they eat during the winter
months. Open water also supports oysters and other bottom-
dwellers. Oysters and other filter feeders help maintain water
quality by filtering suspended organic particles out of the
water. The oyster reef itself is a solid structure that provides
habitat for other shellfish, finfish and crabs.
Habitats
15
-------
Living Resources &
Biological Communities
Within every habitat, communities of organisms
exist in close relationship to each other. Commu-
nities may be as small as an oyster bar or as large as the
entire Bay. The relationships among species form a com-
plex web. Some organisms produce food and others
serve as prey. Some communities, such as underwater ,f
Bay grasses, provide both food and cover. Many //
organisms fit into more than one of these categories.
The functions within a given community are almost
endless, and the Chesapeake Bay supports countless
communities both large and small.
Change is characteristic
of ecological systems
including the Bay. Germina-'
tion of plant seeds, birth of
animals, growth, local
movement and migration
affect the species composi-
tion of each community, as
do changes in water quality, loss of habitat
or overharvesting.
Some variations in community struc-
ture, such as seasonal changes, follow a
predictable pattern. Every year, waterfowl
migrate to the Bay to spend the winter feed-
ing in uplands, wetlands and shallow water areas.
Then, each spring, they return to northern
parts of the continent to breed. After mating
each summer, female blue crabs migrate to
the mouth of the Bay to spawn, while the
males remain in the upper and
middle Bay. Anadromous
fish, like shad and herring,
spend most of their lives in
the ocean, but each spring
enter the Bay and migrate into
freshwater to spawn. These are
just a few of the seasonal
variations that occur.
Some Bay communities are
prone to rapid population fluc-
tuations of one or more species.
This is particularly true of plankton. Rapid
Sea Nettle
(Chrysaora qu/nquecirrha)
Striped bass
(Morone saxatilis)
American oyster
(Crassostrea
virgmica)
changes in plankton diversity and
abundance may occur hourly or daily
due to the interaction of biologi-
cal, physical and chemical
factors.
Many species exhibit long-
term patterns in population
abundance and distribution.
For example, croakers suffer
high mortalities during excep-
tionally cold weather. This
fish was abundant in the Bay
during the late 1930s and
early 1940s. It is believed
that relatively mild winters in
the late 1930s and early
1940s promoted the
high numbers of
croakers. Human-in-
duced pressures can
affect long-term patterns.
Striped bass declined rap-
idly in the late 1970s and
through the 1980s due to
overharvesting and subse-
quent reproductive failure.
However, successful man-
agement measures led to a
restored stock in 1995.
Individual species may
belong to a variety of communi-
ties and use different habitats
throughout their life cycles.
Habitats are connected and
communities often overlap.
Changes in a particular habitat
not only may affect the communi-
ties it supports but other habitais
and communities as well.
In the Chesapeake, wetlands,
grass beds, plankton, fish and bot-
tom-dwellers are biological commu-
nities supported by the Bay's diverse
16
Chesapeake Bay: Introduction to an Ecosystem
-------
habitats. Wetlands are transitional areas between water and
land. Bay grass beds range from mean low tide to a depth of
about six feet or where light becomes limiting to plant
growth, although some freshwater species thrive in water up
to nine feet deep. Open water supports the plankton commu-
nity, composed mostly of minute creatures that float and drift
with the movement of the water, and the nekton community,
the fish and other swimmers that move freely throughout the
Bay and its tributaries. The bottom sediments support ben-
thic organisms.
Wetlands
Wetlands are environments subjected to periodic flooding
or prolonged saturation, producing specific plant communi-
ties and soil types. The presence of water affects
the type of soil that develops and the types of
plants and animals that live there. Wetlands are
characterized by hydrophytic vegetation (water-
loving plants adapted to wet soils) and hydric
soils (saturated or periodically flooded soils).
There are two broad categories of wetlands in the
Bay watershed. Wetlands within the reach of tides
are considered tidal. Salinity in tidal wetlands
ranges from fresh to saltwater. Nontidal or palus-
trine wetlands are freshwater areas unaffected by
the tides. Wetlands receive water by rain, ground-
BAY FACT
Wetlands are
among the
most productive
ecosystems in the
world, producing
more food (in the
form of detritus)
than many
agricultural fields.
water seepage, adjacent streams and, in the case of tidal wet-
lands, tides. Salinity, substrate and frequency of flooding
determine the specific plant and animal life a wetland can
support.
Tidal wetlands are dominated by nonwoody or herba-
ceous vegetation and are subjected to tidal flooding. These
wetlands have a low marsh zone (flooded by every high tide)
and a high marsh zone (flooded by extremely high tides).
Plants such as smooth cordgrass are found in the low marsh
zone of brackish and saltwater marshes. The high marsh
zone may be dominated by saltmeadow cordgrass, black
needlerush, saltgrass or marsh elder. Freshwater marshes
also have low and high zones. Along the water's edge, you
may find wild rice, arrow arum, pickerel weed and pond lily.
In the high zone, cattail and big cordgrass may be prevalent.
Nontidal wetlands frequently contain bul-
rush, broad-leaved cattail, jewel weed, spike
rushes and sedges. Forested wetlands, often
referred to as swamps, may have permanent
standing water or may be seasonally flooded.
Trees commonly found in forested wetlands
include red maple, black gum, river birch,
black willow, Atlantic white cedar and bald
cypress. Willows, alders and button bushes are
types of shrubs present in forested wetlands.
Approximately 1.5 million acres of wet-
lands remain in the Bay watershed, less than
A Button bush
(Cephalanthus occidentals)
B Big cordgrass
(Spartina cynosuroides)
C Narrow-leaved cattail
(Typha angustifolia)
D Black needlerush
(Juncus roemerianus)
E Saltmeadow cordgrass
(Sparina patens)
F Wild rice
(Zizania aquatica)
G Widgeon grass
(Ruppia maritima)
Living Resources & Biological Communities
-------
A Black willow
(Salix nigra)
B Red maple
(Acer rubrum)
C River birch
(Betula nigra)
D Jewehveed
(Impatiens capensis)
E River bulrush
(Sdrpus fluviatilis)
f Broad-leaved cattail
(Typha lattfolia)
half of the wetlands that were here during colonial times. Of
the remaining wetlands, 13% are tidal and 87% are nontidal.
Often viewed as wastelands, wetlands were drained or
filled for farms, residential developments, commercial build-
ings, highways and roads. Over the past several decades, our
understanding and appreciation of wetlands has increased.
Plant diversity, biochemical reactions and hydrology of
these habitats make them extremely productive. Wetlands
support large quantities of plant biomass. The huge amount
of visible plant material in wetlands makes up only the
above-ground biomass. The below-ground biomass, com-
posed of root and rhizome material, is often more than dou-
ble the above-ground biomass. This creates a tremendous
reservoir of nutrients and chemicals bound up in plant tissue
and sediments.
Many of the Bay's living resources depend on these wet-
land habitats for their survival. Tidal wetlands are the win-
tering homes for great flocks of migratory waterfowl. Other
wildlife, including muskrats, beavers, otters, songbirds and
wading birds, rely on wetlands for food and cover. Fish and
shellfish, many of which are commercially valuable, use
wetlands as spawning or nursery areas. Thousands of aquatic
animals, including reptiles,
amphibians, worms, insects, snails,
mussels and tiny crustaceans,
thrive in wetlands and are food for
other organisms.
The abundance of food and
shelter provided by wetland vege-
tation is essential to other members
of this community. A host of inver-
tebrates feed on decomposing
plants and animals. This nutrient-
BAY FACT
Two'thirds of
the nation's
commercial fish
and shellfish
depend on
wetlands as
nursery or
spawning grounds.
rich detritus is also available to juvenile stages of fish and
crabs. A dense layer of microscopic plants and animals,
including bacteria and algae, coats the land surface and
serves as food. Stems of larger plants provide another good
source of food. Decomposing plants and animals are the
major food source for other wetland inhabitants.
Wetlands are also important for controlling flood and
storm waters. Fast-moving water is slowed by vegetation and
temporarily stored in wetlands. The gradual release of water
reduces erosion and possible property damage. Coastal wet-
lands absorb the erosive energy of waves, further reducing
erosion.
Poised between land and water, wetlands act as buffers,
regulating the flow of sediments and nutrients into rivers and
the Bay. As water runs off the land and passes through wet-
lands, it is filtered. Suspended solids, including sediment
pollutants, settle and are trapped by vegetation. Nutrients,
carried to wetlands by tides, precipitation, runoff and
groundwater, are trapped and used by wetland vegetation. As
plant material decomposes, nutrients are released back into
the Bay and its tributaries, facilitated by floodwaters or tides.
Economically, wetlands provide opportunities for fishing,
crabbing and hunting. Other popular activities include hik-
ing, birdwatching, photography and wildlife study. People
are lured by the beauty of wetlands to enjoy the sights and
sounds that these areas can offer.
Underwater Bay Grasses
In the shallow waters of the Bay, underwater grasses sway
in the aquatic breeze of the current. Known as submerged
aquatic vegetation or SAV, these amazing plant communities
provide food and shelter for waterfowl, fish, shellfish and
18
Chesapeake Bay: introduction to an Ecosystem
-------
invertebrates. Like other green plants, bay grasses produce
oxygen, a precious and sometimes lacking commodity in the
Bay. These underwater plants also trap sediment that can
cloud the water and bury bottom-dwelling organisms like
oysters. As waves roll into grass beds, the movement is
slowed and energy is dispelled, protecting shorelines from
erosion. During the growing season, Bay grasses take up and
retain nitrogen and phosphorus, removing excess nutrients
that could fuel unwanted growth of algae in the surrounding
waters.
Like a forest, field or wetland, a grass bed serves as habi-
tat for many aquatic animals. Microscopic zooplankton feed
on decaying Bay grasses and, in turn, are food for larger Bay
organisms. Minnows dart between the plants and graze on
tiny organisms that grow on the stems and leaves. Small fish
seek refuge from larger and hungrier mouths. Shedding blue
crabs conceal themselves in the vegetation until their new
shells have hardened. Thus, grasses are a key contributor to
the energy cycling in the Bay. Bay grasses are a valuable
source of food, especially for waterfowl. In the fall and win-
ter, migrating waterfowl search the sediment for nutritious
seeds, roots and tubers. Resident waterfowl may feed on
grasses year-round.
Fourteen species of grasses are commonly found in the
Bay or nearby rivers. Salinity, water depth and bottom sedi-
ment determine where each species can grow. Survival of
Bay grasses is affected most by the amount of light that
reaches the plants. Poor water quality resulting in less light
penetration is the primary cause for declining grasses.
Factors that affect water clarity, therefore, also affect the
growth of bay grasses. Suspended sediment and other solids
cloud the water, blocking precious sunlight from the grasses.
Excessive amounts of suspended sediment may cover the
plants completely. Sources of suspended sediments include
runoff from farmland, building sites and highway construc-
tion. Shoreline erosion also adds sediment to the Bay. Land
development, boat traffic and loss of shoreline vegetation
can accelerate natural erosion.
Nutrients, although vital to all ecosystems, can create
problems when present in excessive amounts. Major sources
of nutrients include sewage treatment plants, acid rain, agri-
cultural fields and fertilized lawns. High levels of nutrients
stimulate rapid growth of algae, known as blooms. Algal
blooms cloud the water and reduce the amount of sunlight
reaching Bay grasses. Certain types of algae grow directly on
the plants, further reducing available sunlight.
Common Underwater Bay Grasses
Widgeon grass
(Ruppia maritima)
Eelgrass
(Zostera marina)
Wild celery
(Vallisneria americana)
Redhead grass
(Potamogeton perfoliatus)
Living Resources & Biological Communities 19
-------
Historically, more than 200,000
acres of grasses grew along the
shoreline of the Bay. By 1984, a
survey of bay grasses documented
only 37,000 acres in the Bay and its
tidal tributaries. Declining water
quality, disturbance of grass beds
and alteration of shallow water
habitat all contributed to the Bay-
wide decline. The absence of
grasses translates into a loss of food
and habitat for many Chesapeake
Bay species. However, bay grasses
have rebounded steadily since the
low point in 1984. In 2003, scien-
tists estimated that about 64,709
acres of underwater grasses were
living in the Bay.
Water quality is the key to restor-
ing grasses. Scientists have identi-
fied the water quality conditions
and requirements necessary for the
survival of five grass species: wild
celery found in freshwater, sago
pondweed, redhead grass and wid-
geon grass found in more estuarine
water and eelgrass found in the
lower Bay in saltier water. Each
species is an important source of
food for waterfowl. Bay grasses are
making a comeback, however.
Water quality is beginning to
improve due to the ban of phos-
phates in detergents, reduction of
fertilizer use by farmers and home-
owners, protection of shallow water
habitat and the reduction of nutri-
ents in sewage effluent.
Plankton
Mainly unseen by the naked eye,
a community made up of predomi-
nantly microscopic organisms also
fuels the Bay ecosystem. These tiny
plants and animals, called plankton,
drift at the mercy of the currents
and tides. Some of the tiny crea-
tures move up and down in the
BAY FACT
water may contain
water column to take advantage of light. Others will drop
below the pycnocline, a zone between waters with different
densities, to avoid being washed out to the ocean.
Phytoplankton are tiny single-celled plants. Like higher
plants, phytoplankton require light to live and reproduce.
Therefore, the largest concentrations occur near the surface.
Salinity affects phytoplankton dis-
tribution with the largest number of
species preferring the saltier waters
near the mouth of the Bay. The
amount of nutrients in the water is a
major determinant to the abundance
of these plants. The largest concen-
trations of phytoplankton in the '";, .
Bay occur during the spring when
nutrients are replenished by freshwater runoff from the
watershed. These high concentrations produce the character-
istic brown-green color of estuarine and near-shore waters.
Although there are many species of phytoplankton, the major
types in the Bay are diatoms and dinoflagellates. When
dinoflagellates dominate the water, a red-tinted bloorn,
called a mahogany tide, may be produced. Mahogany tides
typically occur on warm, calm days, often following rain.
Diatoms, which are present throughout much of the year,
may account for 50% of total algal production.
Changes in chemical conditions, such as the addition of
nutrients, can cause rapid increases in the amount of algae.
These algal blooms can have serious consequences. They
block light from reaching SAV beds. Even after they die,
they can cause problems. Deposition and subsequent decom-
position of large masses of plankton in the mainstem of the
Bay can deplete dissolved oxygen, suffocating other estuar-
ine animals.
Phytoplankton are the major food source for microscopic
animals called zooplankton. Dominating the zooplankton are
the copepods (tiny crustaceans about one millimeter long)
and fish larvae. Zooplankton are distributed according to
salinity levels. Distribution patterns also are related to those
of their main food source—the phytoplankton. Zooplankton
also feed on other particulate plant matter and bacteria.
Tiny larvae of invertebrates and fish also are considered
zooplankton. Although this planktonic stage is only tempo-
rary, the larvae are a significant part of the community. These
larvae are consumed by larger animals, and may, as they
grow, consume copepods.
Another group of zooplankton found in the Bay are the
protozoa. These single-celled animals feed on detritus and
bacteria. They, in turn, become food for larvae, copepods and
larger protozoa.
20
Chesapeake Bay: Introduction to an Ecosystem
-------
Bacteria play an important function in the Bay. They are
essentially the decomposers. Their primary function is to
break down dead matter, particularly plants. Through this
process, nutrients in dead plant and animal matter again
become available for growing plants. Bacteria are eaten by
zooplankton and other filter-feeding animals in the Bay.
Bacteria can be residents of the Bay or can be introduced
through various pathways, including human sewage and
runoff from the land. Coliform bacteria are normal resident
bacteria found in the intestines of mammals. The presence of
coliform in a body of water indicates that human or other
animal wastes are present. Coliform bacteria are an indicator
that disease-producing pathogens may be present in the
water.
Clearly visible to the unaided eye, jellyfishes and comb
jellies are the largest zooplankton. Some of these gelatinous
creatures swim, though they are still at the mercy of the
water currents. Jellyfishes have tentacles with stinging cells
used to stun prey. The most famous jellyfish in the Chesa-
peake is the sea nettle. Sea nettles feed voraciously on other
zooplankton, including fish larvae, comb jellies and even
small fish. Because of the large volume of water in their bod-
ies, few animals except sea turtles prey on sea nettles. Comb
jellies, lacking the stinging cells of nettles, capture prey with
adhesive cells. They, too, consume vast quantities of small
copepods and zooplankton, especially oyster larvae.
The Swimmers
Swimmers comprise the nekton community. These organ-
isms can control and direct their movements. This group
includes fish, some crustaceans and other invertebrates.
Approximately 350 species of fish can be found in the
Chesapeake Bay. They can be divided into permanent resi-
dents and migratory fish. The residents tend to be smaller in
size and do not travel the long distances that migratory
species do.
Smaller resident species, such as killifish, normally occur
in shallow water where they feed on a variety of inverte-
brates. The bay anchovy, the most abundant fish in the Bay,
is a key player in the Chesapeake food web. Bay anchovies
feed primarily upon zooplankton. Adult anchovies also may
consume larval fish, crab larvae and some benthic species. In
turn, the bay anchovy is a major food source for predatory
Bay anchovy
(Anchoa mitchilli)
Weakfish
(Cynoscion regalis)
Striped killifish
(Fundulus majalis)
Bluefish
(Pomatomus saltatrix)
Striped bass
(Morone saxatilis)
Living Resources & Biological Communities
21
-------
fish like striped bass, bluefish and weakfish, as
well as some birds and mammals.
Migratory fish fall into two categories:
anadromous, which spawn in the Bay or its trib-
utaries, and catadromous fish, which spawn in
the ocean. Anadromous fish migrate varying dis-
tances to spawn in freshwater. Some can even be
considered Bay residents. For instance, during
the spawning season, yellow and white perch
travel short distances from the brackish water of
the middle Bay to freshwater areas of the upper
Bay or tributaries. Striped bass also spawn in the tidal fresh-
water areas of the Bay and major tributaries. Some remain in
the Chesapeake to feed while others migrate to ocean waters.
Shad and herring are truly anadromous, traveling from the
ocean to freshwater to spawn and returning to the ocean to
feed. Eels are the only catadromous species in the Bay.
Although they live in the Bay for long periods, eels eventu-
ally migrate to the Sargasso Sea in the central North Atlantic
to spawn.
Other fish utilize the Bay strictly for feeding. Croaker,
drum, menhaden, weakfish and spot journey into the Bay
while still in their larval stage to take advantage of the rich
supply of food. The abundance of menhaden supports a com-
mercial fishing industry and provides food for predatory fish
and birds. Bluefish enter the Bay only as young adults or
mature fish.
Besides fish, crustaceans and invertebrates may be part of
the nekton community. Larger animals like sharks, rays, sea
turtles, and occasionally marine dolphins and whales enter
the Bay.
The blue crab is difficult to place in any one community,
because it requires a variety of aquatic habitats, from the
mouth of the Bay to fresher rivers and creeks, in order to
BAY FACT
Oysters are
alternate
hermaphrodites,
meaning they can
sense aender
imbalances and
change their sen.
complete its life cycle. Throughout the year,
crabs may burrow into the Bay bottom, shed and
mate in shallow waters and beds of bay grasses
or swim freely in open water. The first life stage
of a blue crab, called the zoea, is microscopic
and lives a planktonic free-floating existence.
After several molts, the zoea reaches its second
larval stage: the megalops. Another molt and a
tiny crab form is apparent. Both juvenile and
adult blue crabs forage on the bottom and hiber-
nate there through the winter. In spring, the crab
quickly begins migrating from the southern part
of the Chesapeake to tidal rivers and northern portions of the
Bay. During the rest of the year, adult blue crabs are dis-
persed throughout the Bay, swimming considerable dis-
tances using their powerful paddle-like back fins.
Life at the Bottom
The organisms that live on and in the bottom sediments of
the Bay form complex communities. Known as benthos, these
bottom-dwellers include animals, plants and bacteria. Benthic
organisms often are differentiated by their habitat. Epifauna,
like oysters, barnacles and sponges, live upon a surface.
Worms and clams, considered infauna, form their own com-
munity structure beneath the bottom sediments, connected to
the water by tubes and tunnels. The roots and lower portions
of bay grasses supply the physical support for a variety of epi-
phytic organisms. An oyster bar, and the many species it sup-
ports, is another example of a benthic community. Benthic
communities that exist on or in bare, unvegetated substrate are
made up of mollusks, worms and crustaceans.
As with all aquatic life in the Bay, salinity affects the dis-
tribution of bottom-dwellers, but sediment type also plays a
role. Neither coarse sand nor soft mud support rich benthic
LIFE STAGES OF A BLUE CRAB
Zoea
Immature
Crab
22
Chesapeake Bay: Introduction to an Ecosystem
-------
A A Hard clam (Mercenana mercenana)
B Atlantic oyster drill (Urosalpim cinerea)
C Common clam worm (Nereis succinea)
D Red ribbon worm (Micrura leidyi)
E Soft-shelled clam (Mya arenaria)
BENTHIC COMMUNITY
F Glassy tubeworm (Spiochaetopterus oculatus) J Oyster spat
G Black-fingered mud crab (Panopeus herbstii) K Ivory barnacle (Balanus ebumeus)
H Whip mudworms (Polydora ligni) L Skilletfish (Gobiesox strumosus)
I Sea squirts (Mo/gu/a manhattensis) M American oyster (Crassostrea virginica)
B >.
• ' a
. .••«.-.,, •(>,.«
-------
Food Production & Consumption
The most important relationship among Chesapeake Bay
species is their dependence upon each other as food. We
are all carbon-based creatures. Carbon is the basic element
of organic compounds, such as proteins, carbohydrates,
lipids and nucleic acids. These compounds are the building
blocks of life that make up the bodies of living organisms.
Feeding is the process by which organisms cycle energy-rich
carbon through the ecosystem. Each organism supplies the
fuel needed to sustain other life forms.
Plants and some bacteria can produce their own food
through a process known as photosynthesis. Using energy
from the sun, carbon dioxide and water are combined to form
high-energy organic compounds. These organic compounds
and other necessary chemicals form a plant's cellular struc-
ture, allowing it to grow. Because of this ability to use car-
bon dioxide and sunlight to produce their own food, plants
are called autotrophs or self-feeders. They are the primary
food producers. All other organisms must feed, directly or
indirectly, on organic material produced by plants.
Animals cannot process carbon via photosynthesis.
Instead, they acquire carbon by eating the organic matter
contained in plant and animal tissue or dissolved in water.
The animal breaks this organic material down into com-
ponents it can use for energy and growth. Animals are
heterotrophs or other-feeders.
CARBON-OXYGEN CYCLE
Sunlight
BAY FACT
Each year,
crabbers catch
approximately
two-thirds of
the adult blue
crab population
in the Bay.
Every biological activity, such as reproduction, growth,
movement and bodily functions, requires energy. Whether
organisms produce food themselves or ingest it from other
sources, they all must break down organic molecules to use
the carbon and energy contained within. This process is
called respiration.
Aerobic respiration uses oxygen
and releases carbon in the form of
carbon dioxide. It compliments
photosynthesis, which uses carbon
dioxide and produces oxygen.
Together, aerobic respiration and
photosynthesis compose the
carbon-oxygen cycle.
All living things respire, but
autotrophs carry out photosynthesis
as well. Plants usually release more oxygen than they con-
sume, and animals use that excess oxygen for respiration. 1 a
turn, animals release carbon dioxide, which plants require
for photosynthesis.
While carbon and oxygen are two of the most prevalent
elements in our physical make-up, many others are needed.
Nitrogen and phosphorus are two such elements. They are
crucial to the operation of the Bay's life support system.
Nitrogen is a major component of all organisms, prima-
rily as a key ingredient in protein. When an organism dies,
bacteria breaks down proteins into amino acids. Bacteria
then remove the carbon, converting the acids into ammonia.
Plants are able to use ammonia as a source of nitrogen. In the
presence of oxygen, bacteria can convert ammonia to nitrite
and nitrate, also good sources of nitrogen. Under low oxygen
conditions, some bacteria convert nitrate to gaseous nitrogen
that is unavailable to most aquatic organisms. However, in
tidal freshwater, some blue-green algae are able to use
gaseous nitrogen directly.
Phosphorus is another element essential to plant growth
During decomposition and in the presence of oxygen, bacte-
ria convert organic phosphorus to phosphate. Phosphates are
readily used by plants. However, phosphate also attaches to
sediment particles and settles out of water very quickly. The
resulting decrease in available phosphorus can limit planl
growth.
Temperature, sunlight, carbon dioxide and usable nitro-
gen and phosphorus control the rate of photosynthesis. Since
plants are the only organisms able to produce new food from
inorganic matter, the rate of photosynthesis determines the
24
Chesapeake Bay: Introduction to an Ecosystem
-------
FOOD CHAIN
Producers
Decomposers &
Detritus Feeders
production of organic carbon compounds and, ultimately, the
availability of food in the Bay ecosystem.
To illustrate how these factors affect the productivity of the
Bay, examine the Chesapeake's most abundant food
producer—the phytoplankton. Like all plants, phytoplankton
require sunlight, nutrients and water. In the Bay, water is
never a limiting factor. However, the amount of sunlight and
nutrients can limit phytoplankton growth. The amount of sun-
light available to an aquatic plant depends on the sun's alti-
tude, cloud cover, water depth and turbidity (cloudiness of
water). Temperature also controls the rate of photosynthesis.
Nutrients in the form of carbon dioxide and usable nitro-
gen and phosphorus are rarely available in the exact propor-
tions required by plants. Normally, one nutrient is in short
supply compared to the others and is considered the limiting
nutrient. If a limiting nutrient is added, a growth spurt may
occur. Conversely, reducing the amount of a limiting nutrient
causes plant production to decline.
Phosphorus controls the growth of some phytoplankton
species in the spring, especially in the tidal freshwater and
brackish areas. Nitrogen is the prime limiting factor at higher
salinities, particularly during warm months. Carbon dioxide
limitations may control the rate of photosynthesis during
algal blooms in tidal freshwater.
The Bay's life support system depends on maintaining the
delicate balance between the living and non-living compo-
nents. Although the Chesapeake's potential production
capacity is massive, it is also finite. Problems affecting the
simplest producers dramatically affect the survival of con-
sumers.
The Food Web
As one organism eats another, a food chain is formed.
Each step along a food chain is known as a trophic level, and
every organism can be categorized by its feeding or trophic
level. The most basic trophic level is made up of producers:
plants and algae that make their own food. Organisms that
eat plants or other animals are consumers. Decomposers
digest the bodies of dead plants and animals and the waste
products of both. An example of a simple food chain starts
with phytoplankton converting sunlight and nutrients into
living tissue. They, in turn, are eaten by copepods—members
of the zooplankton community. The copepods then are con-
sumed by bay anchovies, which are eaten by bluefish and
striped bass. These fish can be harvested and eaten by peo-
ple. This illustrates how organic carbon compounds origi-
nally produced by a plant pass through successively higher
trophic levels.
Food production and consumption in the Bay are rarely
this simple or direct. Seldom does one organism feed exclu-
sively on another. Usually, several food chains are inter-
woven together to form a food web. Decomposers appear
throughout the food web, breaking organic matter down into
nutrients. These nutrients are again available to producers.
Food Production & Consumption
25
-------
This complex network of feeding continuously cycles
organic matter back into the ecosystem.
The transfer of energy from one organism to the next is,
however, inefficient. Only about 10% of the available energy
is transferred from one trophic level to the next. For exam-
ple, only a portion of the total amount of phytoplankton car-
bon ingested by zooplankton is assimilated by the
zooplankton's digestive system. Some of that is used for res-
piration, bodily functions and locomotion. A small fraction is
used for growth and reproduction. Since these are the only
functions that produce additional tissue, only this fraction of
energy is available to the consumer at the next trophic level.
Economically important foods like fish and shellfish
depend upon lower trophic level organisms. For every pound
of commercial fish taken from the Chesapeake, almost 8,000
pounds of plankton had to be produced. An ecosystem must
be enormously productive to support substantial populations
of organisms at the highest trophic levels. Massive quantities
of plants are required to support relatively few carnivores,
such as the striped bass or bluefish. Because producers are
the basis of all food, they influence the production of other
organisms. However, an overabundance of producers like
algae also can be detrimental, causing a loss of Bay grasses
and reducing the amount of dissolved oxygen available to
other organisms.
Toxic substances in contaminated prey also can be passed
on to the consumer. Heavy metals and organic chemicals are
stored in the fatty tissues of animals and con-
centrate there. As a result, an animal's body
may contain a much higher concentration
of the contaminant than did its food.
This phenomenon is known as bioac-
cumulation. The severe decline of
the bald eagle during the 1950s, 1960s
and 1970s was attributed to bioaccumu-
lation. During World War 11, a chemi-
cal pesticide, DDT, was used to control
insects and agricultural pests. Fish and
small mammals that fed on these pests
were in turn contaminated with higher
concentrations. Eagles eating contami-
nated prey concentrated even higher
levels of DDT and its by-product DDE.
The DDE caused the birds to lay
extremely thin-shelled eggs, so thin that most broke in the
nest and many eagle pairs failed to produce young. As a
result of the DDT ban in 1972 and protection provided
by endangered species status, bald eagles have been
able to recover to the population we have today.
Direct and Detrital Pathways
Two basic pathways dominate the estuarine food web.
The direct pathway leads from plants to lower animals to
higher animals. The detrital pathway leads from dead
organic matter to lower animals then to higher animals. The
detrital pathway is dominant in wetlands and bay grass beds.
The direct and detrital pathways coexist and are not eas-
ily separated. Higher plants, such as eelgrass, widgeon grass,
saltmarsh grass and cordgrass, contribute most of their car-
bon as detritus. However, epiphytic algae growing on these
grasses is usually eaten by consumers, putting them in the
direct food web.
In deeper waters, detritus from dead phytoplankton, zoo-
plankton and larger animals, as well as detritus from upland
drainage, wetlands and bay grasses, continually rains down
on the benthos. Bottom-dwelling animals, such as oysters,
clams, crustaceans, tube worms, shrimp and blue crabs, feed
on it.
A Harpacticoid
(Scottolana canadensis)
B Calanoid
(Acartia dausi)
C Cyclopoid
(Oi'thona co/carvaj
BAY FACT
Most larval fish consume
huge amounts of
zooplankton to survive,
A gallon of Bay water
can contain mem than
500,000 woplankton.
26
Chesapeake Bay: Introduction to an Ecosystem
-------
The direct pathway dominates the plankton
community. The smallest of phytoplankton,
known as nannoplankton, are fed upon by larger
microzooplankton. Larger phytoplankton, like
most diatoms and dinoflagellates, provide food
for larger zooplankton and some fish. Bacteria,
fungi, phytoplankton and possibly protozoa pro-
vide food for oysters and clams.
Copepods, a dominant form of zooplankton,
play a key role in the food web between phyto-
plankton and animals. Copepods feed on most
phytoplankton species and occasionally on the
juvenile stages of smaller copepods. In marine waters, most
animal protein production from plant material is carried out
by copepods. Copepods and a related organism, krill, are the
world's largest stock of living animal protein. Larger carni-
vores feed voraciously on them. Herring, for example, may
consume thousands of the tiny creatures in a single day.
Most of the Bay's fish are part of the direct food web, but
their feeding habits are complex. Some experts contend that
BAY FACT
Oysters were once
so plentiful they
could filter the
entire volume of
Bay water in a
few days. This
process now takes
over a year.
menhaden are the dominant fish in the Bay's
intricate food web. The extremely fine gill rakers
of menhaden act as a filtering net. Adult men-
haden swim with their mouths open, consuming
any plankton in their paths. In turn, menhaden are
a major food of striped bass, bluefish and osprey.
They also support a large commercial fishery that
utilizes the fish for animal feed and for products
containing fish meal and oil.
Like menhaden, anchovies and all fish larvae
are primarily zooplankton feeders. Adult striped
bass, bluefish and weakfish feed mainly on other
fish. Striped bass and other predators also may feed upon
young of their own species. Many fish are omnivorous, eat-
ing both plants and animals. Omnivores, like eels and croak-
ers, feed on planktonic copepods, amphipods, crabs, shrimp,
small bivalves and small forage fish. Small forage fish, like
killifish and silversides, often feed upon the epifauna and
epiphytes along wetlands and in shallow water communities.
Food Production & Consumption
27
-------
Preserving the Chesapeake Bay:
the Big Picture
If we want to preserve the Chesapeake Bay and its many
delights for future generations, we must change our per-
spectives. We must view not only what occurs in the Bay
itself, but what happens on the land surrounding
it. It is not enough to protect shorelines, regulate
fisheries and prevent direct disposal of pollu-
tants. We must take into account all of the activi-
ties that occur throughout the watershed from
Cooperstown, New York, to Virginia Beach, Vir-
ginia, and from Pendleton County, West Virginia,
to Seaford, Delaware. Released into this water-
shed, fertilizers, sediment and chemical contam-
inants from agricultural, residential and urban
areas travel downstream to the Bay.
However, even a watershed perspective is not
adequate without personal responsibility. Even
though we acknowledge that activities in the watershed
affect the Bay ecosystem, we must also realize that indi-
vidual actions impact the Bay everyday. Fertilizers and
THE BAY'S
FUTURE
"When we see
the land as a
community to
which we belong,
we may begin to
use it with love
and respect."
Aldo Leopold, 1945
pesticides from yards and gardens affect the Bay as much as
those from large farms. Excessive use of cars produces more
exhaust with nitrogen oxides, which contribute to elevated
nitrogen levels in the Bay. Indiscriminate use of
water results in more water that must be treated
and then discharged into the Bay system.
If we want a clean, healthy Bay that can sus-
tain biological diversity and be economically
stable, we must identify, alter and, if possible,
eliminate our own individual actions that impact
the Bay. People alter ecosystems. The solutions
to problems threatening the Bay are in the
lifestyles we choose. The Bay ecosystem is one
unit where forests are linked to oyster reefs,
housing developments to Bay grasses and
choices to responsibility. Education also is
required. Informed people choose actions that are beneficial
for themselves, their culture, their community and the
Chesapeake Bay.
28
Chesapeake Bay: Introduction to an Ecosystem
-------
BE PART OF THE SOLUTION, NOT PART OF THE PROBLEM
1
2
Reduce your nutrient input to the Bay.
Limit the amount of fertilizers spread
on gardens and lawns. Plant native
vegetation that requires less fertilizer
and water. Leave grass clippings on
lawns and gardens. Maintain your
septic system. Start a compost pile,
instead of using a garbage disposal.
Reduce the use of toxic materials
around your house and yard,
including pesticides.
Use safer, non-toxic alternatives for
cleaning and for controlling pests.
3
Reduce erosion.
Plant strips of native vegetation along
streams and shorelines. Divert runoff
from paved surfaces to vegetated areas.
ave water.
Use water-saving devices in toilets and
sinks. Turn off water when not in use.
Wash cars in grassy areas to soak up
soapy water.
5
Drive less.
Join a carpool or use public
transportation.
6
7
Obey all fishing, hunting and
harvesting regulations.
Be a responsible boater.
Avoid disturbing shallow water areas and
Bay grass beds. Pump boat waste to an
onshore facility.
8
Get involved.
Talk to your elected officials about
your concerns. Join or start a watershed
association to monitor growth and
development locally. Participate in
clean-up activities.
FOR MORE INFORMATION
ABOUT THE
CHESAPEAKE BAY
ECOSYSTEM, VISIT
Preserving the Chesapeake Bay
29
-------
For more information about the Chesapeake Bay and its rivers contact:
Chesapeake Bay Program
(800) YOUR-BAY/(410) 267-5700
www.chesapeakebay.net
B.C. & STATE AGENCIES
Chesapeake Bay Commission
(410) 263-3420
www.chesbay.state.va.us
District of Columbia Department
of Health
(202) 442-5999
dchealth.dc.gov/index.asp
District of Columbia Public Schools
(202) 724-4222
www.kl2.dc.us
Maryland Department of Education
(410) 767-0100
www.msde.state.md.us
Maryland Department of the
Environment
(800) 633-61017(410) 537-3000
www.mde.state.md.us
Maryland Department of Natural
Resources
(877) 620-8367/(410) 260-8710
www.dnr.state.md.us
Pennsylvania's Chesapeake Bay
Education Office
(717)238-7223
www.pacd.org
Pennsylvania Department of
Conservation and Natural Resources
(717)787-9306
www.dcnr.state.pa.us
Pennsylvania Department of Education
(717)783-6788
www.pde.psu.edu
Pennsylvania Department of
Environmental Protection
(717)783-2300
www.dep.state.pa.us
Virginia Department of
Conservation and Recreation
(804) 786-1712
www. dcr. state. va .us/
Virginia Department of Education
(800) 292-3820
www.pen.kl2.va.us
Virginia Department of Environmental
Quality
(800) 592-5482/(804) 698-4000
www.deq.state.va.us
FEDERAL AGENCIES
National Oceanic and Atmospheric
Administration
Chesapeake Bay Office
(410)267-5660
noaa.chesapeakebay.net
National Park Service
Chesapeake Bay Gateways
(410) 267-5747
www.baygateways.net
Natural Resources Conservation Service
(202) 205-0026
www.nrcs.usda.gov
U.S. Army Corps of Engineers
District office in Baltimore
(410) 962-7608
www.nab.usace.army.mil
U.S. Army Environmental Center
(410)436-2556
aec.army.mil/usaec
U.S.D.A. Forest Service
(410)267-5706
www.fs.fed.us
U.S. Department of Education
(800) USA-LEARN
www.ed.gov
U.S. Environmental Protection Agency
Chesapeake Bay Program Office
(800) YOUR-BAY/(410) 267-5700
www.epa.gov/r3chespk
U.S. Fish and Wildlife Service
Chesapeake Bay Field Office
(410)573-4500
www.fws.gov/r5cbfo
U.S. Geological Survey
(888) ASK-USGS/(703) 648-4000
www.usgs.gov
ACADEMIC ORGANIZATIONS
Maryland Sea Grant
(301)403-4220
www.mdsg.umd.edu
Pennsylvania State University
(814) 865-4700
www.psu.edu
University of the District of Columbia
(202) 274-5000
www.wrlc.org/udc.htm
Maryland Cooperative
Extension Service
(301)405-2907
www.agnr.umd.edu
University of Maryland Center for
Environmental Science
(410) 228-9250
www.umces.edu
Virginia Cooperative Extension
(540)231-6704
www.ext.vt.edu
Virginia Institute of Marine Science
(804) 684-7000
www.vims.edu
Virginia Tech
(540)231-6000
www.vt.edu
NONPROFIT ORGANIZATIONS
Alliance for the Chesapeake Bay
410-377-6270
www.acb-onlme.org
Chesapeake Bay Foundation
(410)268-8816
www.cbf.org
Chesapeake Bay Trust
(410)974-2941
www.chesapeakebaytrust.org
30
Chesapeake Bay: Introduction to an Ecosystem
-------
Glossary of Terms
Algae - Simple rootless plants that grow in bodies of water
(e.g., estuaries) at rates in relative proportion to the amounts
of nutrients (e.g. nitrogen and phosphorus) available in water.
Amphipods - Small, shrimp-like crustaceans.
Anadromous - Fish that spend most of their life in salt water
but migrate into freshwater tributaries to spawn (i.e., shad,
sturgeon).
Angler - Someone who fishes with a hook, line, and rod.
Anoxic - A condition where no oxygen is present. Much of
the 'anoxic zone' is anaerobic, with absolutely no oxygen, a
condition in which toxic hydrogen sulfide gas is emitted in
the decomposition process.
Aquatic - Living in water.
Autotroph - Any organism that is able to manufacture its
own food. Most plants are autotrophs, as are many protists
and bacteria. Autotrophs may be photoautotrophic, using
light energy to manufacture food, or chemoautotrophic, using
chemical energy.
Benthos (Benthic) - A group of organisms, most often inver-
tebrates, that live in or on the bottom in aquatic habitats (such
as clams that live in the sediments), which are typically
immobile, or of limited mobility or range.
Bioaccumulation - The uptake and storage of chemicals
(e.g., DDTs, PCBs) from the environment by animals and
plants. Uptake can occur through feeding or direct absorption
from water or sediments.
Bivalve - A mollusk with two shells connected by a hinge
(e.g., clams, oysters).
Bloom - A population burst of phytoplankton that remains
within a defined part of the water column.
Brackish - Somewhat salty water (0.5 ppt - 25 ppt), as in an
estuary.
Carnivore - Literally, an organism that eats meat. Most car-
nivores are animals, but a few fungi, plants and protists are as
well.
Catadromous - Fish that live in freshwater and migrate to
saltwater to spawn (i.e., American eel).
Coastal Plain - The level land with generally finer and fer-
tile soils downstream of the piedmont and fall line, where
tidal influence is felt in the rivers.
Consumer - Any organism that must consume other organ-
isms (living or dead) to satisfy its energy needs.
Contaminant - Anything that makes something impure,
unclean or polluted, especially by mixing harmful impurities
into it or by putting it in contact with something harmful.
Copepod - A type of small planktonic crustacean. Copepods
are a major group within the mesozooplankton, and are both
important grazers of phytoplankton and food for fish.
Crustaceans — The class of aquatic arthropods including
copepods, isopods, amphipods, barnacles, shrimp and crabs
which are characterized by having jointed appendage and
gills.
DDT - A group of colorless chemicals used as insecticides.
DDTs are toxic to man and animals when swallowed or
absorbed through the skin.
Denitrification - The conversion of nitrite and nitrate nitro-
gen (after nitrification) to inert nitrogen gas. This treatment
process requires that little or no oxygen be present in the sys-
tem and that an organic food source be provided to foster
growth of another type of bacteria. The organic food source
can be either recycled waste, activated sludge or methanol.
The resultant nitrogen gas is released to the atmosphere.
Dermo - Oyster disease caused by the protozoan parasite,
Perkinsus marinus.
Detritus - Accumulated organic debris from dead organisms,
often an important source of nutrients in a food web.
Diatoms - Microscopic algae with plate-like structures com-
posed of silica. Diatoms are considered a good food source
for zooplankton.
Dinoflagellate -Algae of the order dinoflagellata.
Dissolved Oxygen - Microscopic bubbles of oxygen that are
mixed in the water and occur between water molecules. Dis-
solved oxygen is necessary for healthy lakes, rivers and estu-
aries. Most aquatic plants and animals need oxygen to
survive. Fish will drown in water when the dissolved oxygen
levels get too low. The absence of dissolved oxygen in water
is a sign of possible pollution.
Glossary of Terms
31
-------
Diversity - An ecological measure of the variety of organ-
isms present in a habitat.
Ecology - The study of interrelationships between living
things and their environment
Ecosystem - All the organisms in a particular region and the
environment in which they live. The elements of an ecosys-
tem interact with each other in some way and so depend on
each other either directly or indirectly.
Effluent - The discharge to a body of water from a defined
source, generally consisting of a mixture of waste and water
from industrial or municipal facilities.
Emergent Wetland - A wetland dominated by nonwoody,
soft-stemmed plants.
Endangered - A species that is in immediate danger of
becoming extinct and needs protection to survive.
Environment - The place in which an organism lives and the
circumstances under which it lives. Environment includes
measures like moisture and temperature, as much as it refers
to the actual physical place where an organism is found.
Epiphyte - A plant that grows upon another plant. The epi-
phyte does not 'eat' the plant on which it grows, but merely
uses the plant for structural support or as a way to get off the
ground and into the canopy environment.
Epiphytic - Substances that grow or accumulate on the
leaves of submerged aquatic plants. This material can include
algae, bacteria, detritus and sediment.
Erosion - The disruption and movement of soil particles by
wind, water or ice, either occurring naturally or as a result of
land use.
Estuary -A semi-enclosed body of water that has a free con-
nection with the open sea and within which seawater from the
ocean is diluted measurably with freshwater that is derived
from land drainage (i.e., the Chesapeake Bay). Brackish estu-
arine waters are decreasingly salty in the upstream direction
and vice versa. The ocean tides are projected upstream to the
fall lines.
Fall Line -A line joining the waterfalls on several rivers that
marks the point where each river descends from the upland to
the lowland and marks the limit of navigability of each river.
Filter Feeder - An organism which filters food from the
environment via a straining mechanism, such as gills (e.g.,
barnacle, oyster, menhaden.)
Food Chain / Food Web - The network of feeding relation-
ships in a community as a series of links of trophic levels,
such as primary producers, herbivores and primary carni-
vores. Includes all interactions of predator and prey, along
with the exchange of nutrients into and out of the soil. These
interactions connect the various members of an ecosystem
and describe how energy passes from one organism to
another.
Habitat - The place and conditions in which an organism
lives.
Herbivore - Literally, an organism that eats plants or other
autotrophic organisms. The term is used primarily to describe
animals.
Invertebrate — Animals which lack a backbone and include
such as squids, octopuses, lobsters, shrimps, crabs, shell-
fishes, sea urchins and starfishes.
Land Use - The way land is developed and used in terms of
the kinds of anthropogenic activities that occur (e.g., agricul-
ture, residential areas, industrial areas).
Larva - A discrete stage in many species, beginning with
zygote formation and ending with metamorphosis.
Mammal - Any of a large class called Mammalia; warm-
blooded, usually hairy vertebrates whose offspring are fed
with milk secreted by the mammary gland.
Marine - Refers to the ocean.
Marsh - An emergent wetland that is usually seasonally
flooded or wet and often dominated by one or a few plant
species.
Migratory - Describing groups of organisms that move from
one habitat to another on a regular or seasonal basis.
Mollusk - The invertebrate phylum which contains bivalves
(i.e., oysters), gastropods (i.e. snails) and squids.
Molt - To shed the exoskeleton (outer covering) or prior to
new growth (i.e., blue crab).
MSX - An oyster disease caused by the protozoan parasite,
Haplosporidium nelsoni.
Nekton - Organisms with swimming abilities that permit
them to move actively through the water column and to move
against currents (e.g., fish, crabs).
Nitrification - The process to which bacterial populations,
under aerobic conditions, gradually oxidize ammonium to
nitrate with the intermediate formation of nitrite. Biological
nitrification is a key step in nitrogen removal in wastewater
treatment systems.
32
Chesapeake Bay: Introduction to an Ecosystem
-------
Nitrogen - Nitrogen is used primarily by plants and animals
to synthesize protein. Nitrogen enters the ecosystem in sev-
eral chemical forms and also occurs in other dissolved or par-
ticulate forms, such as tissues of living and dead organisms.
Nonpoint Source - A diffuse source of pollution that cannot
be attributed to a clearly identifiable, specific physical loca-
tion or a defined discharge channel. This includes the nutri-
ents that run off the ground from any land use - croplands,
feedlots, lawns, parking lots, streets, forests, etc. - and enter
waterways. It also includes nutrients that enter through air
pollution, through the groundwater, or from septic systems.
Nutrients - Compounds of nitrogen and phosphorus dis-
solved in water, which are essential to both plants and ani-
mals. Too much nitrogen and phosphorus act as pollutants
and can lead to unwanted consequences - primarily algae
blooms that cloud the water and rob it of oxygen critical to
most forms of aquatic life. Sewage treatment plants, indus-
tries, vehicle exhaust, acid rain, and runoff from agricultural,
residential and urban areas are sources of nutrients entering
the Bay.
Omnivore - Literally, an organism that will eat anything.
Refers to animals that do not restrict their diet only to plants
or other animals.
Pelagic - The open ocean, excluding the ocean bottom and
shore.
Pesticides - A general term used to describe chemical sub-
stances that are used to destroy or control insect or plant
pests. Many of these substances are manufactured and do not
occur naturally in the environment. Others are natural toxics
that are extracted from plants and animals.
pH - Measure of the acidity or basicity of water.
Phosphorus - A key nutrient in the Bay's ecosystem, phos-
phorus occurs in dissolved organic and inorganic forms, often
attached to particles of sediment. This nutrient is a vital com-
ponent in the process of converting sunlight into usable
energy forms for the production of food and fiber. It is also
essential to cellular growth and reproduction for organisms
such as phytoplankton and bacteria. Phosphates, the inor-
ganic form, are preferred, but organisms will use other forms
of phosphorus when phosphates are unavailable.
Photosynthesis - The process by which plants convert car-
bon dioxide and water into carbohydrates and oxygen. The
carbohydrates are then available for use as energy by the
plant or other consuming organisms (CO2+ H2O +SUN-
LIGHT= C6H,2O6 + O2). This process is also referred to as
'primary production.'
Phytoplankton - Plankton are usually very small organisms
that cannot move independently of water currents. Phyto-
plankton are any plankton that are capable of making food
via photosynthesis.
Piedmont - Uplands or hill country above the 'fall line' of
coastal rivers, where rapids or cataracts tumble down to the
level topography where tidal influence begins.
Plankton - Small or microscopic algae and organisms asso-
ciated with surface water and the water column.
Point Source -A source of pollution that can be attributed to
a specific physical location; an identifiable, end of pipe
'point'. The vast majority of point source discharges for
nutrients are from wastewater treatment plants, although
some come from industries.
ppt - Parts per thousand (used as a measurement of salinity).
Predator -An organism that hunts and eats other organisms.
This includes both carnivores, which eat animals, and herbi-
vores, which eat plants.
Prey - An organism hunted and eaten by a predator.
Primary Producers - Organisms, such as algae, that convert
solar energy to organic substances through the molecule
chlorophyll. Primary producers serve as a food source for
higher organisms.
Pycnocline - The zone between waters having different den-
sities. An example from an estuary would be a pycnocline
separating deep, more saline water and shallow, more fresh
water.
Riparian Forest Buffers - An area of trees, usually accom-
panied by shrubs and other vegetation, that is adjacent to a
body of water which is managed to maintain the integrity of
stream channels and shorelines, to reduce the impact of
upland sources of pollution by trapping, filtering and con-
verting sediments, nutrients and other chemicals, and to sup-
ply food, cover and thermal protection to fish and other
wildlife.
Salinity - A measure of the salt concentration of water.
Higher salinity means more dissolved salts. Usually meas-
ured in parts per thousand (ppt).
SAV - See submerged aquatic vegetation.
Sediment - Matter that settles and accumulates on the bot-
tom of a body of water or waterway.
Shellfish -An aquatic animal, such as a mollusk (e.g., clams,
oysters and snails) or crustacean (e.g., crabs and shrimp),
having a shell or shell-like external skeleton (exoskeleton).
Spat - Juvenile, newly attached oysters (i.e., oyster spat).
Glossary of Terms 33
-------
Spawn - To release eggs and/or sperm into water.
Species - A population or group of populations that are in
reproductive contact but are reproductively isolated from all
other populations.
Submerged Aquatic Vegetation (SAV) - Rooted vegetation
that grows under water in shallow zones where light pene-
trates. Also known as 'bay grasses'.
Suspended Sediments - Particles of soil, sediment, living
material, or detritus suspended in the water column.
Stratification - The formation, accumulation or deposition
of materials in layers, such as layers of freshwater overlying
higher salinity water (saltwater) in estuaries.
Thermocline - A specific depth at which there is a layer of
water where the temperature changes dramatically. Warmer
surface water is separated from the cooler deep water. This
temperature gradient results in the formation of a density
barrier.
Threatened - A species that is likely to become endangered
if not protected.
Tides - The periodic movement of water resulting from grav-
itational attraction between the earth, sun and moon.
Tributary - A body of water flowing into a larger body of
water. For example, the James River is a tributary of the
Chesapeake Bay.
Trophic Level - The layer in the food chain in which one
group of organisms serves as the source of nutrition of
another group of animals.
Turbidity - The decreased clarity in a body of water due to
the suspension of silt or sedimentary material.
Waterfowl - Any of various birds that swim on water, such
as ducks, geese and swans or any bird species that is ecolog-
ically dependent on aquatic environments such as wetlands.
Watershed - A region bounded at the periphery by physical
barriers that cause water to part and ultimately drain to a par-
ticular body of water.
Wetland - Low areas, such as swamps, tidal flats and
marshes, which retain moisture.
Zooplankton - A community of floating, often microscopic
animals that inhabit aquatic environments. Unlike phyto-
plankton, zooplankton cannot produce their own food and so
are consumers.
34
Chesapeake Bay: Introduction to an Ecosystem
-------
Chesapeake Bay Progran
A Watershed Partnership
THE CHESAPEAKE BAY PROGRAM
A Watershed Partnership
What is the Chesapeake Bay Program?
The Chesapeake Bay Program is a unique,
regional partnership leading and directing
Bay restoration and protection issues.
Formed in 1983, the Bay Program brings
together the states of Maryland, Virginia, and
Pennsylvania; the District of Columbia; the
Chesapeake Bay Commission, a tri-state
legislative body; and the U.S. Environmental
Protection Agency, representing the federal
government. The Bay Program partners
work together alongside researchers, policy-
makers and resource managers from local,
state and federal governments universities,
conservation organizations and business and
industry from throughout the Bay watershed.
The Bay Program partners also have recently
enlisted the help of the Bay's headwater
states, West Virginia, New York and
Delaware, in the restoration efforts.
The Chesapeake Bay Program has become a
model for other estuary restoration programs
across the nation and throughout the world.
A great deal of the Bay Program's success is
the result of efforts to reach across state
boundaries to work cooperatively on restor-
ing the Chesapeake Bay.
What's the Bay Program doing to
help the Chesapeake?
The most recent Chesapeake Bay agreement,
Chesapeake 2000, is guiding Bay restoration
through the next decade. The Bay Program
partners are working with researchers, policy
makers, and conservation organizations are
to address the many issues affecting the Bay.
The commitments in Chesapeake 2000, as
well as our programs, are focused on five
issue areas:
1. protecting living resources
2. restoring vital habitat
3. improving water quality
4. encouraging sound land use
5. expanding community engagement.
The Renewed Agreement
CHESAPEAKE BAY PROGRAM
410 Severn Avenue, #109, Annapolis, MD 21403
1-800-YOUR BAY • www.chesapeakebay.net
-------
Striped Bass
Potamogeton perfoliatus
------- |