ECOTOXICITY OF CONTAMINATED SEDIMENTS, A MATTER OF BIOAVAILABILITY

Marine and freshwater mesocosm-scale experiments with contaminated sed iments have shown that there is a direct relationship between the accu mulated contaminant levels and the feeding habits of the organisms use d. The highest levels of PAHs and PCBs were found in the sediment feed ing lugworm Arenicola marina and in Tubifex worms. The levels of conta minants in the suspension feeding mussels Mytilus edulis and the zebra mussels, Dreissena polymorpha, were not influenced by the contaminant content of the sediments, but were related instead to the level of co ntaminants in the sea water above. Intermediate levels were found in t he baltic tellin, Macoma balthica, which is a filter feeder as well as a deposit feeder, depending on the availability of food. These result s show that there is no simple relationship between contaminant concen tration in the sediments and bioavailability. Higher levels of contami nants do not necessarily lead to higher levels of these contaminants i n Arenicola, due to differences in the sediment structure and the agei ng of the contamination. On the other hand, toxic effects are related to the internal concentrations of certain chemicals. The internal conc entrations observed in Arenicola may provide a good estimation of the true bioavailability of sedimentary contaminants and can also be used as an indicator for potential environmental effects. (C) 1998 IAWQ. Pu blished by Elsevier Science Ltd.