Accumulation of polychlorinated biphenyls by the infaunal brittle stars Amphiura filiformis and A-chiajei: effects of eutrophication and selective feeding

Polychlorinated biphenyl (PCB) accumulation by the 2 brittle stars Amphiura filiformis and A. chiajei was studied in a laboratory experiment and in th e field. In the laboratory study, the fate of C-14-2,2',4,4'-tetrachlorobip henyl (TCB) was determined in benthic microcosms, with and without the addi tion of phytoplankton (Phaeodactylum tricornutum). Added phytoplankton was rapidly mineralised and stimulated an increased dissolved organic carbon co ntent in the water-column and bacterial production on the sediment surface. TCB uptake by the brittle stars was significantly higher in the microcosms enriched with phytoplankton. Differences in TCB concentrations were still significant after normalisation to lipid content, suggesting that selective feeding rather than equilibrium partitioning was the cause of the increase d TCB burden. Treatment effects were more apparent in body (disk) tissue, t han in the arm fraction of the brittle stars, in agreement with the lipid c ontent of the tissues. No difference in total organic carbon, total nitroge n or TCB concentrations of the sediment surface was detected. In the field, ophiuroids and sediment cores were collected at a coastal urban estuary of f the city of Goteborg, Sweden, and at an offshore station in the Kattegat Sea. Sum-PCBs of sediment and brittle stars were ca 3 times higher at the c oastal station than at the offshore station. Biota sediment accumulation fa ctors, determined from the laboratory and field exposures, ranged from 1.5 to 5.9. The results from this study suggest that eutrophication processes, such as increased phytoplankton production, may contribute to increasing th e accumulation of organic pollutants in benthic sediment-ingesting fauna. T he significance of A. filiformis in the transfer of PCBs to higher trophic levels is also discussed based on data of sublethal predation by the demers al flat fish Limanda limanda and from production estimates of an A. filifor mis population.