Polychlorinated Biphenyl- and Mercury-Associated Alterations on Benthic Invertebrate Community Structure in a Contaminated Salt Marsh in Southeast Georgia |
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Authors: | M T Horne N J Finley M D Sprenger |
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Institution: | (1) U.S. Fish and Wildlife Service, 2890 Woodbridge Ave., Edison, New Jersey 08837, USA , US;(2) National Park Service, Cape Cod National Seashore, 99 Marconi Site Road, Wellfleet, Massachusetts 02667, USA , US;(3) U.S. Environmental Protection Agency, 2890 Woodbridge Ave., Edison, New Jersey 08837, USA , US |
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Abstract: | The community structure of a benthic macroinvertebrate assemblage in a contaminated salt marsh was evaluated as part of
an ecological characterization of a former chloralkali production facility in Georgia. Sample locations were chosen based
on a gradient of the primary contaminants of concern, total mercury and polychlorinated biphenyls (PCBs), primarily Aroclor
1268. Sediment concentrations of Aroclor 1268 ranged from 2.3 to 150 mg/kg dry weight, while mercury concentrations ranged
from 15 to 170 mg/kg dry weight in the study area. Mercury and PCBs were determined to be co-located in the sediments. Total
organic carbon composition of the sediments was negatively associated with PCB and mercury concentrations. A total of 29 benthic
taxa was identified in 49 samples; replicate samples were taken at each of five sampling locations. Mean infaunal density
across all sampling locations was estimated at approximately 61,000 to 234,000 organisms m−2. Overall, polychaetes comprised 57% of the infaunal community with Manayunkia aestuarina as the dominant species. Oligochaetes, nematodes, crustacea, insects, and gastropods comprised 23.0, 18.0, 1.0, 0.7, and
0.2% of the overall benthic community, respectively. Density estimates of individual species between sampling locations showed
no consistent patterns in response to pollutants. However, an analysis of higher taxonomic levels revealed some general trends.
In uncontaminated areas, the benthic community was dominated by nematodes and oligochaetes, whereas moderate to highly contaminated
areas were dominated by polychaetes and a smaller percentage of oligochaetes and nematodes. A trophic analysis of the same
data set revealed that the community shifted from an evenly distributed percentage of surface and subsurface feeders in the
uncontaminated areas to a community dominated by surface feeders in the more contaminated locations. Carnivores comprised
from 0.13 to 0.90% of the trophic structure, with the percentage of carnivores generally decreasing with increasing contamination.
Mercury and PCBs were bioaccumulating in representative marsh benthic invertebrates, presenting a potential source of contaminants
to marsh consumers. Tissue PCB and tissue mercury concentrations were positively related to sediment PCB and mercury concentrations,
respectively. A standard 14-day toxicity test using the amphipod Leptocheirus plumulosus showed no acute toxicity across the sampling locations.
Received: 29 October 1998/Accepted: 3 May 1999 |
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