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An Integrated Approach to Understand Relationships Between Shallow Water Benthic Community Structure and Ecosystem Function in the Chesapeake Bay |
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Background
Shallow water estuarine habitats are highly productive, of significant
socioeconomic, recreational and aesthetic value, and sensitive to human-induced
disturbances. Diffuse sources of pollution, associated primarily with groundwater
discharge and surface water runoff, are now responsible for most deterioration
of water-quality in U.S. coastal regions. Section 101 of the Clean Water
Act requires federal and state agencies to restore and maintain the chemical,
physical, and biological integrity of these coastal areas. Biocriteria-based
methods, such as the multimetric Benthic Index of Biotic Integrity (B-IBI),
have been successfully applied to elucidate regional and local water and
sediment quality impairments and physical habitat disturbance in the Chesapeake
Bay. Although such methods serve as good indicators of anthropogenic disturbance,
their relationship to important functional attributes of aquatic ecosystems,
such as primary production and respiration, nutrient cycling, and food
web structure, is not known.
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Hypothesized relationships between B-IBI and other
measures of community structure and function.
(click on image to enlarge)  |
ObjectivesThe overall objective of this project is to couple
the B-IBI approach with detailed investigations of benthic community structure
and function in order to better understand relationships among military
activities, integrity of benthic communities, and ecosystem functions within
the shallow waters of the Chesapeake Bay estuarine system. Our specific
objectives are to (1) use the Benthic Index of Biotic Integrity (B-IBI)
to assess benthic community health in shallow water habitats at military
installations spanning a range of salinities and stressor types, and (2)
elucidate relationships among B-IBI metrics, food web structure, primary
production, respiration, nitrogen cycling along gradients of impairment
in the Chesapeake Bay, using both military and non-military sites. Our
major hypothesis is that the B-IBI approach, which uses metrics based solely
on aspects of macrobenthic community structure, will predict significant
changes in estuarine food web structure and ecosystem functional processes
that are important for ecosystem sustainability.
In this study, we are: (1) Using the B-IBI approach to determine the “average” health of shallow water benthic communities in regions immediately adjacent to selected military installations. We have stratified the study sites to account for major types of environments found at each installation, for example, protected, muddy tidal marsh creeks in relative close proximity to sources of pollutants in surface runoff and groundwater base flow (near-field stratum); and open water areas, which are expected to have coarser sediments, higher tidal flushing, more potential for wave exposure and less potential for direct impacts of pollutants in surface runoff and groundwater (far-field stratum). Random sampling within each stratum allows us to address two questions: (a) what is the “average” health of the shallow water benthic communities in the region adjacent to each facility and (b) how do the strata compare? (2) Assessing benthic community structure and function along an expected gradient of impairment for comparison of results obtained using the B-IBI approach with other measures. These measurements represent key features or processes of benthic systems that are important to understanding contaminant effects on food web structure and water/sediment quality. |
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ApproachField data are collected in shallow water habitats
adjacent to selected military installations, non-military sites that are
expected to be highly impacted by anthropogenic activities, and at paired
control sites in relatively pristine areas. The military installations
that have been proposed for this study are: Aberdeen Proving Ground, Marine
Corps Combat Development Command (Quantico), Dahlgren (NSWC), Patuxent
River Naval Air Station, Langley Air Force Base/NASA Langley Research Center,
and Fort Eustis (US Army). These sites span a range from the tidal freshwater/oligohaline
upper Chesapeake Bay and Potomac River estuary, to the meso- to polyhaline
regimes of the lower Chesapeake Bay. Candidate control sites are identified
using the Chesapeake Bay Program (CBP) Monitoring Program, U.S. Environmental
Protection Agency’s (U.S. EPA) Environmental Monitoring and Assessment
Program (EMAP) and Middle Atlantic Integrated Assessment Program (MAIA)
databases. Control sites are in areas that are not greatly influenced by
point source or concentrated non-point loadings.
Sampling stations are randomly selected within pre-determined strata delineated on the basis of potential impacts from the adjacent watershed activities, and at paired control sites of comparable habitat type. Macrofaunal invertebrate community composition and abundance will be used to compute B-IBIs for each station sampled and average values for stations at each study site. For comparison with the B-IBI results, other measures of structure and function will be made at the same stations. The results of the study will be modeled using univariate and multivariate statistical methods to relate B-IBIs and component metrics (e.g. species diversity) with measures of ecosystem function. The proposed study is designed to elucidate relationships among important living resources and key ecosystem processes in estuarine ecosystems. This project will improve and expand existing tools to help scientists and Department of Defense installation managers better understand how to manage and restore estuarine ecosystems. Biocriteria-based approaches increasingly will play a central role in water-quality management. |
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Study SitesDuring mid-summer 2003, year one of this study, sampling
was conducted at four high mesohaline/polyhaline sites in the southern
Chesapeake Bay: Langley Air Force Base (LAFB), relatively pristine control
sites located in Thorntons Creek and the Goodwin Islands, and a highly
impacted site in the Elizabeth River. Fort Eustis, Patuxent, and their
respective paired control sites in the southern and mid-Chesapeake Bay
will be sampled during year two (2004), while Dahlgren, Quantico, Aberdeen,
and their paired control sites will be visited in year three (2005).
SERDP -Study Site Maps
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PeopleContact Information:
Dr.
Linda Schaffner
Dr.
Iris Anderson
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LinksSERDP |
