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(138) Organic contaminants in marine foodwebs : bioaccumulation versus biotransformation. Abarnou , A.1, Jaouen-Madoulet , A.1,2, Loizeau , V.1, Leboulenger , F.2, 1 2 ABSTRACT- The fate of organic contaminants in biota depends on environmental, biological and chemical factors. PCBs are typical contaminants which are biomagnified through marine food webs and they have been extensively studied so far. The distribution of PCBs and PAHs have been followed in the plankton from the baie de Seine and in estuarine foodwebs from the Seine estuary. Both PCBs and PAHs are bioconcentrated in phytoplankton due to their hydrophobic character. PCB concentrations increase from phytoplankton to largest zooplanktonic species whereas the opposite is observed in the case of PAHs. In the estuarine food webs from a highly contaminated estuary similar results are observed : PCB concentrations increase from the lower trophic level (CB153 10 ng.g-1 dry weight) to the fish (sea bass CB153 : 200 ng.g-1 d.w., or flounder 250 ng.g-1 d. w.) where BaP concentrations decrease marquedly from 200 ng.g-1 d. w. in sediments to about one ng.g-1 d. w. or less in higher fish. The determination of these two large classes of contaminants enlight differently our approach to the study of bioaccumulation. Hydrophobic and very persistent contaminants like PCBs are biomagnified with conservation of the same composition of the various congeners. PAHs are not biomagnified ; they are biotransformed into reactive compounds at different extend depending on their structure and also on the consumers which modify the relative composition of the individual compounds. Future trophic models should account for this difference and should consider the biotransformation processes in order to simulate more correctly the fate Key words: marine food chains, bioaccumulation, biotrans, biomagnification |
