| Summary: | This is the first study to report on concentrations of perfluorinated organochemicals (FOCs) in marine mammalsstranded along the southern North Sea coast in relation to stable nitrogen and carbon isotope ratios ( 15 N and 13 C). The presence of FOCs in top predators such as marine mammals would indicate a potential biomagnification of these compounds and their widespread occurrence. Liver and kidney tissues of nine marine mammal species have been sampled. Among all the measured FOCs compounds, PFOS (perfluorooctane sulfonate) was predominant in terms of concentration. The highest PFOS concentrations were found in the liver of harbor seal compared to white-beaked dolphin, harbor porpoise, gray seal, sperm whale, white-sided dolphin, striped dolphin, fin whale, and hooded seal. PFOS concentrations differedsignificantly between sexes and age classes in harbor porpoises. Stable isotope measurements ( 13 C and 15 N) were used in this study to describe the behavior of contaminants in food webs. We found a significant ( p < 0.05) linear relationship between PFOS concentrations inlivers of harbor porpoises and both muscle 13 C and 15 N measurements. Harbor and gray seals and white-beaked dolphin, which displayed the highest trophic position,contained the highest PFOS levels, while offshore feeders such as sperm whales, fin whales, striped dolphin, and white-sided dolphin showed lower PFOS concentrations than inshore species.
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