ACCUMULATION OF ORGANIC CONTAMINANTS IN 2 SEDIMENT-DWELLING SHELLFISHWITH CONTRASTING FEEDING MODES - DEPOSIT-FEEDING (MACOMONA-LILIANA) AND FILTER-FEEDING (AUSTROVENUS-STUTCHBURYI)

Bioaccumulation of four classes of contaminants (organochlorine pestic ides, polychlorinated biphenyls (PCB), polynuclear aromatic hydrocarbo ns (PAH), and chlorophenols) was determined in two sediment-dwelling b ivalves, the tellinid Macomona liliana and the venerid Austrovenus stu tchburyi at five stations along a contaminant gradient in Manukau Harb our, New Zealand. The species were chosen because they provide contras ting exposure pathways for contaminant uptake: A. sturchburyi is a fil ter-feeder and M. liliana is a deposit feeder. They are also important components of the estuarine ecosystem, and A. stutchburyi are used fo r food. Both shellfish showed marked gradients of contaminant concentr ations from the inner-harbour to the entrance. Concentrations of conta minants were similar in the two species, with generally slightly highe r PCB and PAH levels in M. liliana. On a dry tissue weight basis, the PAHs were the major contaminant class, with the highest concentration measured (203 ng/g DW). Mean bioaccumulation factors (BAF) were simila r for the two species, with mean values in the range 20-30 for most co ntaminants with the exception of PAHs, which were less than 1. Mean ac cumulation factor (AF) values, the lipid normalized concentration in o rganisms divided by the organic carbon normalized sediment concentrati on, were mostly in the range 1-4, except for PAHs, which were 0.002 an d 0.14. M, liliana showed significantly higher accumulation ratios tha n A. stutchburyi. The abundance and condition of M. liliana was reduce d at the more contaminated sites. These results suggest that M. lilian a are sensitive indicators of contaminant stress and may be usefully i ncorporated into chemical contaminant and biological effects monitorin g programs.