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USING STABLE ISOTOPES TO TRACK BIOMAGNIFICATION OF POLYCHLORINATED BIPHENYLS (PCBS) THROUGH STREAM FOOD WEBS
Citation:
WALTERS, D., K. M. FRITZ, B. R. JOHNSON, AND J. M. LAZORCHAK. USING STABLE ISOTOPES TO TRACK BIOMAGNIFICATION OF POLYCHLORINATED BIPHENYLS (PCBS) THROUGH STREAM FOOD WEBS. Presented at SETAC, Baltimore, MD, November 13 - 17, 2005.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Most studies of biomagnification are from lentic systems, which are characterized by organic matter and sediment retention. However, biomagnification studies in streams are rare. This is surprising because PCBs and other persistent organic pollutants are known to biomagnify in aquatic ecosystems, and contaminated sediments are pervasive in stream ecosystems. Because it remains unclear if PCBs biomagnify and persist in streams, particularly in streams which are characterized by sediment and organic matter export, we investigated PCB contamination in Twelvemile Creek (Clemson, SC, USA), a stream that received > 400,000 lbs of PCBs from 1955-1978. Our goals were to determine if PCBs biomagnify in streams and to measure the relative importance of heterotrophic and autotrophic pathways for biomagnification. Sites were sampled during spring and fall 2003-04. Major components of the foodweb were analyzed for total PCBs. Biomagnification was apparent, and PCBs consistently increased with trophic level. We found no consistent patterns related to carbon pathways when the entire foodweb was considered. Analysis of individual trophic groups indicated that carbon source effects PCB concentrations. PCBs in grazing insects were more than double those in leaf shredding insects even though PCB concentrations were similar for periphyton and leaves. These results suggest that greater reliance on algal resources contributes to higher PCB concentrations within trophic levels. Our results show that PCBs biomagnify and persist in streams, but the importance of autotrophic and heterotrophic pathways is unclear.