Factors influencing activities of biotransformation enzymes, concentrations and compositional patterns of organochlorine contaminants in members of a marine food web.

The accumulation of polychlorinated biphenyls (PCBs; 34 congeners), sigmaDDT (p,p'-DDT, o,p'-DDT, p,p'-DDD, o,p'-DDD and p,p'-DDE), chlordanes (sigmaCHL; trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and oxychlordane), hexachlorocyclohexanes (sigmaHCH; alpha-, beta- and gamma-isomers), hexachlorobenzene (HCB) and mirex was investigated in members of a marine food web from the Hvaler and Torbjørnskaer archipelago, south-eastern Norway. The species studied were bullrout (Myoxocephalus scorpius), cod (Gadus morhua), herring gull (Larus argentatus) and harbour seal (Phoca vitulina). Furthermore, hepatic biotransformation enzyme activities (ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-depentylase (PROD) and glutathione S-transferase (GST)) were measured in all species. The objectives of the study were to investigate factors causing intraspecies variation in activities of biotransformation enzymes, as well as in concentrations and compositional patterns of the organochlorines (OCs). High correlations between EROD and PROD activities were found in all species, suggesting a single, common catalyst, CYP1A, and render the PROD assay questionable as biomarker for CYP2B inducers in marine wildlife. Furthermore, GST activities are shown to be dependent on biological factors, such as age (in harbour seal) and sex (in bullrout). In fish, the OC concentrations vary between the sexes, likely due to differences in fat deposition strategies and possibly sex dimorphism. In seals, concentrations and compositional patterns of the OCs vary with age, owing to selective transfer from mother to pup in utero and mainly through lactation, but likely also due to age specific xenobiotic metabolising capacity.