Diffuse sources of pollution, associated primarily with groundwater discharge and surface water runoff, are responsible for most of the deterioration of water-quality in United States 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 key functional attributes of aquatic ecosystems is not known.
The overall objective of this project was to couple the B-IBI approach with detailed investigations of benthic community structure and function to better understand relationships between military activities, integrity of benthic communities, and ecosystem function within the shallow waters of the Chesapeake Bay estuarine system. Specific objectives were to: (1) use the B-IBI to assess benthic community health at military installations spanning a range of salinities and stressor types and (2) identify relationships between B-IBI metrics, food web structure, primary production, respiration, and nitrogen cycling along gradients of impairment in the Chesapeake Bay at both military and non-military sites.
Field data were collected in shallow water habitats adjacent to selected military installations or other areas influenced by human activities in the watershed and at paired control sites in relatively undeveloped areas. The primary military installation study sites included: Aberdeen Proving Ground, Quantico Marine Corps Base, Patuxent Naval Air Station, Langley Air Force Base, and Fort Eustis. These sites span a range from the tidal freshwater upper Chesapeake Bay and Potomac River estuary to nearly marine regimes of the lower Chesapeake Bay. Sampling stations were within pre-determined strata delineated on the basis of potential impacts from adjacent watershed activities and at paired control sites of comparable habitat type. Macrofaunal invertebrate community composition and abundance were used to compute B-IBIs for each station sampled as well as average values for stations at each study site. For comparison with the B-IBI results, other measures of ecosystem structure and function were made at the same stations.
The results of this project showed that although Department of Defense (DoD) activities along the shorelines of the Chesapeake Bay create some unique stressors for nearshore habitats, the DoD sites generally had intermediate environmental conditions relative to the range observed within representative Chesapeake Bay shallow water habitats. The major patterns observed in community structure, benthic condition, and ecosystem processes were concordant with a priori classifications of sites based on position along the estuarine gradient, historic regional water quality and land use, and major habitat type.
To access end-user products developed through this research, please visit the Ecosystem-Based Management section on the RC Tools and Training page.
The benefits of this study include improved and expanded tools to help scientists and DoD installation managers better understand how to manage and restore estuarine ecosystems. Ultimately, biocriteria-based approaches will increasingly play a central role in water-quality management.