oEPA
United States
Environmental Protection
Agency
New Tools Measure
Chesapeake Bay Health
INTRODUCTION
The areas where the Chesapeake Bay's tributaries meet the
Bay form the shallow-water ecosystems that provide breeding
areas and protection for many of the seafood delicacies and
waterfowl that humans cherish. These areas, called sub-
estuaries, receive and process inputs (sediment, chemicals,
sewage, fertilizer, etc.) from local watersheds that are mixed
and exchanged with material from the Bay. Research has
shown that human activities directly influence these shallow-
water ecosystems. Any degradation of these systems impacts
our quality of life - our health, what we eat, where we swim,
what we observe, and the aesthetic quality of what we view.
Points at which major changes can be measured are
considered thresholds. Based on the percentage of
development/impervious surfaces (e.g., highways, streets,
parking lots and buildings) and distance from the water,
thresholds have been identified to determine how much and
where development can occur before the estuary begins to
severely degrade. Thresholds can also be used to help
identify where management and restoration could reverse
the consequence of previous stress from development.
Marsh bird diversity, polychlorinated biphenyls (PCBs)
in white perch, and abundance of submerged aquatic
vegetation (SAV) are three ecological indicators linked to
land-use that are being investigated by the Smithsonian
Environmental Research Center (SERC) as part of
the Atlantic Slope Consortium (ASC). These studies
provide strong evidence that the environmental and
ecological conditions of estuaries depend on the land use
in their associated watersheds. Scientists suspect that
numerous other responses in estuaries are also related
to development. Future research, combined with the
work done by ASC, will help in better understanding the
impacts of development on these estuaries.
High
A
Low
0 25 50
Percent Development within 500m of a Wetland
Ecofogicaf
Condition
Lanb
Cover
MARSH BIRD DIVERSITY
Development of the land alters the habitat needed for
birds to breed. The types of birds found in an area
indicate both the ecological condition and the type
of land-cover found in that area. As the land-cover of
an area changes, habitat and the types of birds also
change.
Ecological Indicator: The diversity of birds that breed in wetlands is an
ecological indicator of estuarine health.
Ecological Effect/Impact: Researchers from SERC have found that there
is a precipitous drop (threshold) in the diversity of the bird community
that breeds in estuarine wetlands when more than 14% of the land is
developed in the area that is within 500 meters of a wetland boundary.
Environmental Application: Land use planners at the local, state,
and national level; environmental advocacy organizations; fish and
wildlife agencies; restoration agencies and consultants can use this
information when planning for development and restoration activities. By
understanding the implications of placement and pattern in the watershed,
appropriate buffer (riparian) zones can be designed into development and
restoration plans.
DeLuca, W. V., C. E. Studds, L. L. Rockwood, and P. P. Marra. 2004. Influence of land use on the integrity of marsh bird
communities of Chesapeake Bay. USA. Wetlands 24(4):837-847.
Photo of Least Bittern used with permission of photographer, Robert Bennetts
Symbols for diagrams (left: Ecological Condition/Land Cover) courtesy of the Integration and Application Network
(www.ian.umcea.edu/symbols). University of Maryland Center for Environmental Science.
Bird (marsh wren) illustration used with permission of artist, Denis Kania
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PCBs IN WHITE PERCH
Polychlorinated biphenyls (PCBs) are mixtures of chlorinated compounds that have no known natural sources;
they were banned from production in the USA in 1977. Until then, PCBs were used as coolants and lubricants
in electrical equipment because they are good insulators and do not burn easily. PCBs entered the air, water, and
soil during their manufacture, use, and disposal from accidental spills and leaks during transport and from leaks
or fires in products containing them. They do not readily break down in the environment and they remain there for
long periods of time. They are widely distributed in aquatic ecosystems and remain sufficiently high in many water
bodies to contaminate the food web and result in consumption advisories for valuable fish and shellfish species.
White perch are an ideal indicator species because they spend most of their lives within or near specific sub-
estuaries. They are semi-anadromous, moving into freshwater tributaries to spawn and back into sub-estuaries to
feed. This life cycle continuously exposes them to runoff from the watershed.
Ecological Indicator: The level of PCBs in white perch is an ecological indicator of aquatic condition.
no consumption
recommended
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0.5 meal/mo
1 meal/mo
no restrictions
= sample results
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0 20 40 60 80
Percent Developed Land in Watershed
Figure 1. Total PCBs in white perch in relation to percent
developed land in the watershed.
700
0 10 20 30 40 50
Percent Commercial Land in Watershed
Figure 2. Total PCBs in white perch in relation to percent
commercial land weighted by its proximity to the subestuary.
Ecological Effect/Impact: White perch are eaten by
humans as well as larger fish, birds, and mammals. PCB
levels bio-accumulate in animals (such as white perch)
and, therefore, can reach thousands of times higher than
the levels found in water. The health effects associated
with human consumption of PCBs include acne-like
skin conditions and neurobehavioral and immunological
changes in children. PCBs are also known to cause
cancer in animals.
SERC's research demonstrates that levels of PCBs
in white perch are strongly linked to the percent of
development in a watershed, with dangerous PCB levels
attained at a relatively low percent of development
(Fig. 1). PCB levels in these fish begin to exceed EPA
recommended levels for restricting food consumption
before development reaches 20% of the watershed area.
The levels of PCBs in white perch are more highly
influenced by the percent of commercial development
closer to the shoreline than by commercial development
farther away (inverse distance weighted - IDW) (Fig. 2).
This relationship exists for watersheds with less-intensive
residential/suburban development as well as watersheds
with highly polluting urban/commercial development.
SERC's models show that type of land use, particularly
development, and its proximity to the estuary's tributaries
have important impacts on the PCB levels in white perch.
Environmental Application: The field sampling and
laboratory testing offish currently used to prepare
consumption advisories is very costly. The SERC models
can predict PCB concentrations in white perch at a
significantly reduced cost. PCB consumption advisories
have been developed for several Chesapeake sub-
estuaries, but there is great interest in using this method
to assess others. Other contaminants frequently co-occur
with PCBs and SERC's models will also be useful for
identifying and predicting them.
King, R.S., J.R. Beaman, D.F. Whigham, A.H. Mines, M.E. Baker, and D.E. Welter. 2004.
Watershed land use is strongly linked to PCBs in white perch in Chesapeake Bay subestuaries.
Environmental Science and Technology 38:6546-6552. DOI 10.1021 /es049059m.
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SUBMERGED AQUATIC VEGETATION
A healthy community of underwater plants known as
submerged aquatic vegetation (SAV) or seagrass is essential for
a healthy Chesapeake Bay. These plant communities provide
food for waterfowl and shelter for shellfish, invertebrates,
and fish. Ecosystem services provided by SAV abound.
Microscopic algae living on the grass blades are the base of a
food chain that leads up to blue crabs, shrimp, bay barnacles,
white perch, croaker, and a myriad of other species we care
about. SAV helps stabilize bottom sediments, provides a
protective nursery for many aquatic organisms and is a
valuable food source for waterfowl.
www.ian.umces.edu/symbols
Ecological Indicator:
Researchers at SERC have
developed a bio-optical
model based on total
suspended solids (TSS)
and algal chlorophyll (Chi)
for monitoring the optical
properties of the water
column in the Chesapeake
Bay. The new procedures
have produced a diagnostic
tool for setting water
clarity targets for seagrass
protection.
Ecological Effect/Impact:
Seagrasses need relatively
high amounts of light to grow
and survive. Decreased light
penetration limits the growth
and distribution of seagrasses.
Turbidity, chlorophyll, and
color naturally decrease light
with greater depth. Increases
in sediment and nutrients
from development on the land
can lead to algal blooms and
coatings on seagrass leaves,
which block light and can
ultimately kill the SAV.
Figure 3. Target minimum
water clarity requirements
for seagrass survival are
found along the red line on
this graph. To assess a site,
the median concentrations
for Chi and TSS are plotted
on the graph. This example
shows three TSS and Chi
reduction strategies (blue
dotted lines) that could
meet the minimum light
requirements at this site.
Minimum-light water
"" clarity requirement
m Median concentration
Management strategies
Chlorophyll only
! TSS only
Chi
Algal Bloom-dominated
20 40 60 80 100 120 140 160 180 200
Chi (ug/L)
Figure 4. Stresses
related to water-clarity
conditions fall into
sediment-dominated, or
algal bloom-dominated
regions. Acceptable
water clarity conditions
for SAV occur below the
red line of minimum light
requirement.
Environmental Application: State and federal watershed managers in the
Chesapeake Bay region are using this tool to make management decisions
on reducing suspended solids and chlorophyll to obtain minimum water
clarity for seagrass survival.
Gallegos, C.L., 2001. Calculating optical water clarity targets to restore and protect
submersed aquatic vegetation: Overcoming problems in partitioning the diffuse attenuation
coefficient for photosynthetically active radiation. Estuaries 24. 381-397.
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U.S. EPA Office of Research
and Development
Washington DC
EPA/600/F-04/203
December 2004
US EPA Office of Research and Development
EPA's Science to Achieve Results (STAR)
Estuarine and Great Lakes (EaGLe) Program
GLEI
Great Lakes Environmental Indicators Project
University of
innesota-Duluth
PEEIR
Pacific Estuarine
Ecosystem Indicator
Research Consortium
University of California-Davis
CEER GOM
Consortium for Estuarine
Ecoindicator Research for the Gulf of Mexico
University of Southern Mississippi
ASC
Atlantic Slope Consortium
Pennsylvania State University
Smithsonian Environmental Research Center
Virginia Institute of Marine Sciences
East Carolina University
Environmental Law Institute
EaGLe Program HQ
Washington DC
ACE INC
Atlantic Coast Environmental
Indicators Consortium
University of North Carolina-Chapel Hill
Direct and indirect effects of
human activities have taken a
toll on the nation's estuaries,
yet few direct linkages have been
identified between human activities
on land and responses in estuarine
ecosystems. The Atlantic Slope
Consortium is one of five national
projects funded by EPA's EaGLe
program. The goal of the EaGLe
program is to develop the next
generation of ecological indicators
that can be used in a comprehensive
coastal monitoring program.
U.S. EPA
Office of Research and Development
National Center for Environmental Research
Barbara Levinson
202-343-9720
Levinson.Barbara@epa.gov
http://es.epa.gov/ncer/centers/eagles
Atlantic Slope Consortium
Pennsylvania State University
Robert Brooks
814-863-1596
rpb2@psu.edu
www.asc.psu.edu
Smithsonian Environmental
Research Center
SERC
Dennis Whigham
443-482-2226
whighamd@si.edu
www.serc.si.edu
U.S. EPA
Mid-Atlantic Integrated Assessment
Patricia Bradley
410-305-2744
bradley.patricia@epa.gov
www.epa.gov/maia
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