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1J - Bioaccumulation (WEP/74) Cadmium bioavailability and accumulation in the presence of humic acid to the zebra mussel, Dreissena polymorpha. Voets, Judith1, Bervoets, Lieven1, Blust, Ronny1, 1 University of Antwerp (RUCA), Antwerp, Antwerp, Belgium ABSTRACT- In aquatic systems part of the metals are complexed by different types of ligands and this usually results in a lowered bioavailability and toxicity to biota. A very important group of complexing agents in aquatic ecosystems is dissolved organic matter (DOM), e.g. humic and fulvic acids, which are often present at concentrations orders of magnitude higher than that of the trace metals. Conflicting evidence exists concerning the bioavailability of metal complexes of dissolved organic matter and they have been reported to both decrease and increase metal uptake. In this work the effect of Aldrich humic acid on cadmium accumulation by the zebra mussel, Dreissena polymorpha was studied under laboratory conditions. Mussels, collected in a drinking water reservoir were exposed to varying, environmentally relevant, concentrations of cadmium in the presence and absence of humic acid. During a period of 31 days, water and mussel samples were taken every 3 to 4 days and the cadmium concentrations in the water and tissue determined. Measurements with a cadmium ion selective electrode were performed to determine the free cadmium ion activity in the exposure waters and the level of organic carbon was determined with a total organic carbon analyser. The accumulation of cadmium in the soft tissues of the zebra mussels did not reach a plateau during the exposure period and was significantly lowered in the presence of humic acid. However, cadmium accumulation was higher than predicted on the basis of the free cadmium ion activity in the water, indicating that cadmium complexed to humic acid is partly available to zebra mussels. Key words: accumulation, humic acid, cadmium, zebra mussel |
