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

Abstract

Polychlonnated biphenyl (PCB) accumulation by the 2 brittle stars Amphiura filiformis and A . chjajei was studied in a laboratory experiment and in the field. In the laboratory study. the fate of '4C-2,2',4,4'-tetrachlorobiphenyl (TCB) was determined in benthic microcosn~s, with and without the addition of phytoplankton (Phaeodactylum tricornutum) Added phytoplankton was rapidly mineralised and stimulated an increased dissolved organic carbon content 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 equilibnum partitioning was the cause of the increased TCB burden. Treatment effects were more apparent in body (disk) tissue, than in the arm fraction of the bnttle stars, in agreement with the lipid content of the tissues. No difference in total organic carbon, total nitrogen or TCB concentrations of the sediment surface was detected. In the field, ophuroids and sediment cores were collected at a coastal urban estuary off the city of Gteborg, Sweden, and at an offshore station in the Kattegat Sea. Surn-PCBs of sediment and brittle stars were ca 3 times higher at the coastal station than at the offshore station. Biota sediment accumulation factors, 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 the accurnulation of organic pollutants in benthic sediment-ingesting fauna. The significance of A. fjliformjs in the transfer of PCBs to higher trophic levels is also discussed based on data of sublethal predation by the demersal flat fish Limanda Dmanda and from production estimates of an A. filiforrnis population.