Fate of Kepone and Mirex in a Model Aquatic Environment: Sediment, Fish, and Diet

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Abstract
Laboratory studies of freshwater sediment and a daphnid–bluegill (Daphnia magna–Lepomis macrochirus) food chain indicated that the organochlorine insecticides Kepone and mirex resist microbial degradation, accumulate and resist metabolism in fish, and move through a food chain. We found no direct evidence of degradation of either compound after 56 d of incubation in freshwater sediments under aerobic or anaerobic conditions. Furthermore, we found no metabolism or co-metabolism of 14C-labeled Kepone in sediments that had long-term preexposure to Kepone and by-products nor did we detect a selective process occurring in the sediments that changed the capacity of the autochthonous microbiota to metabolize Kepone. After 28 d of exposure to 14C-labeled Kepone or mirex in water and natural food, bluegills accumulated Kepone and mirex equal to 10 606 and 12 274 times the respective exposure concentrations. Elimination patterns were dissimilar: mirex tended to persist in fish tissue but Kepone did not. Neither Kepone nor mirex was metabolized by bluegills. Retention of mirex introduced into bluegills by daphnids was about 3 times greater than that of Kepone. Accumulation of Kepone and mirex by bluegills was about half that of DDT.Key words: Kepone, mirex, degradation, freshwater sediment, accumulation, elimination, bluegills, daphnids, residue dynamics, food chain, accumulation index

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