|Dynamics of an estuarine ecosystem: long-term trend in the macrobenthic communities of Chesapeake Bay, (1985-1993)|
Dauer, D.M. (1997). Dynamics of an estuarine ecosystem: long-term trend in the macrobenthic communities of Chesapeake Bay, (1985-1993). Oceanol. Acta 20(1): 291-298
In: Oceanologica Acta. Elsevier/Gauthier-Villars: Montreuil. ISSN 0399-1784; e-ISSN 1878-4143
Chesapeake Bay; benthos; trends; estuary; eutrophication
Long-term trends in subtidal macrobenthic communities of the lower Chesapeake Bay, USA, were examined using data collected quarterly (March, June, September and December) fr om 1985 through 1993 at 16 stations along a salinity gradient from tidal freshwater regions of the major tributaries (James, York and Rappahannock rivers) to the polyhaline region of the mainstem of Chesapeake Bay. In March 1989 two stations were added to the program in the mesohaline region of the Southern Branch of the Elizabeth River, a region characterized by contaminated sediments. A non-parametric trend analysis procedure was applied to five parameters characterizing macrobenthic community structure: community biomass, species richness, abundance of individuals, proportion of biomass composed of opportunistic species (opportunistic biomass composition) and proportion of biomass composed of equilibrium species (equilibrium biomass composition). A total of 48 trends were detected. No trends were found at stations subjected to hypoxic/anoxic conditions ol at stations with contaminated sediments. Trends in benthic community parameters affected by eutrophication may be difficult to interpret at moderate levels of organic enrichment or sediment contamination. Therefore, trends in functional groups (e.g. opportunistic and equilibrium species) of the benthic community may be the best indicators of the ecological significance of changes in community structure.