PCB accumulation and alterations of lipids in two length classes of the oyster Crassostrea angulata and of the clam Ruditapes decussatus

Polychlorinated biphenyls (PCB) were analysed in two length classes of the oyster Crassostrea angulata and the clam Ruditapes decussatus collected in Sado estuary and Ria Formosa, respectively. Oysters showed no significant differences (p < 0.05) in accumulation with size, while smaller clams presented higher PCB levels than the larger ones. The PCB accumulation in same size classes of the two species, and the effect of PCB-exposure on their lipids were investigated during 60 d under laboratory controlled conditions. Again, no significant differences (p < 0.05) in accumulation with relation to size were observed for oysters, while smaller clams showed PCB levels 10 times higher than the larger ones. Triglycerides in the oysters of both sizes displayed a sharp reduction in the first 30 d of contamination, remaining at very low levels until the end of the experiment. PCB in the larger clams reached 360 ng g−1 and no change on lipid composition was recorded, but in smaller individuals levels went up to 2400 ng g−1 and the lipids were altered. Field and laboratory results showed that small and large individuals of the two bivalve species responded differently in terms of PCB accumulation and, under drastic contamination, lipids of oysters were strongly affected and lipid composition of smaller clams w as modified.