Document Type

Report

Publication Date

4-2002

Pages

85 pp.

Abstract

Benthic macrofauna are an important component of estuarine ecosystems. These organisms are a food source for higher trophic levels including fishes and crabs (Virnstein 1977, 1979; Holland et al. 1980; Dauer et al. 1982) and birds (Botton 1984; Quammen 1984). Benthic macrofauna affect both the physical and chemical properties of the sediment and the overlying water column (e.g., Rhoads and Young 1970; Rhoads 1973; Aller 1978, 1980), influence nutrient cycling (Rowe et al 1975; Zeiteschel 1980; Flint and Kamykowski 1984), and are capable of directly controlling phytoplankton biomass in the water column (Cleorn 1982; Officer et al 1982; Cohen et al. 1984; Nichols 1985). Because of these characteristics, monitoring of the benthos provides important information for making management decisions in marine systems (Bilyard 1987). Also, the relativelylong life span and sedentary nature of these organisms make them good indicators of water quality and the effects of man-made disturbances on aquatic systems (Reish 1973; Pearson and Rosenberg 1978; Bilyard 1987).

Numerous studies have documented the effects of pollution and other anthropogenic activities on macrofaunal communities within estuaries (e.g., Boesch 1972; Brown et al. 1987; Beukema 1991; Gaston and Young 1992; Dauer et al. 1992, 1993; Dauer 1993, 1997; Dauer and Alden 1995). Investigators attempting to describe the effects of pollution on benthic macrofaunal communities have often experienced the problem of distinguishing the natural variation in these communities due to habitat type (i.e., salinity regime, sediment type, depth, etc.) from the effects caused by pollution. These problems have resulted in the development of multi-metric indices that allow for the characterization of benthic biological condition within and between habitat types. This approach has been used primarily in freshwater ecosystems and is typically referred to as the index of biotic integrity (IBI) approach (see reviews by Davis and Simon 1995; Karr and Chu 1999). Recently, a benthic index of biotic integrity (B-IBI) was developed for the Chesapeake Bay and its major tributaries (Weisberg et al. 1997). This index compares the deviation of community metrics from values at reference sites that are assumed to be minimally impacted byanthropogenic activities. This index has been successfully used to describe the status of and long-term trends in benthic community conditions within the Chesapeake Bay and its tributaries in relation to water quality characteristics (Dauer et al. 1998; 1999) and is correlated to measures of land use and nutrient loads within the Chesapeake Bay watershed (Dauer et al. 2000). However, one of the major limitations of this index is its inability to directly identify the source of stress that is the cause of degraded benthic community condition.

The objective of this study was to develop analytical tools that are capable of classifying regions in Chesapeake Bay identified as having degraded benthic communities into categories distinguished by the type of stress experienced by those communities. Sediment contaminants and bottom low dissolved oxygen concentrations were identified as the primary sources of anthropogenic stress on benthic communities and an attempt was made to develop multivariate statistical tools that could distinguish between these sources of stress. Ultimately, environmental managers could use these tools to make recommendations for analytical chemistry studies to confirm the sources and levels of contaminants in predetermined regions of concern and to develop management plans for controlling contaminant effects.

Rights

Included with kind permission from the author(s).

Comments

Addendum to the Report: Development of Diagnostic Approaches to Determine Sources of Anthropogenic Stress Affecting Benthic Community Condition in the Chesapeake Bay, added June 2005.

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