Organochlorine pesticides and polychlorinated biphenyls in the Arctic Ocean food web

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Abstract

Polychlorinated biphenyls (PCBs), polychlorinated camphenes (PCCs) and isomers of DDT and DDE were the predominant organochlorine (OC) hydrocarbons measured in epontic particulate matter, zooplankton, pelagic and benthic amphipods and liver tissue from an abyssal fish collected in the Arctic Ocean. Chlordane, dieldrin and other cyclodienes and hexachlorocyclohexane (HCH) isomers were present at lower concentrations. Levels on a dry weight basis in plankton of various sizes <63 μm to 2 mm were similar to those in epontic particulate matter, but on a lipid weight basis, concentrations in smaller plankton were two to five times higher. Organochlorines in amphipods and liver from the glacial eelpout Lycodes frigidus exceeded levels in zooplankton by up to an order of magnitude. Large benthic lysianassid amphipods (Tmetonyx cicada, Anonyx nugax and Eurythenes gryllus) accumulated higher concentrations on a dry and lipid weight basis than small species (Onisimus spp. and Andaniexis spp.) or the under-ice gammaridean amphipod (Gammarus wilkitzkii).

No significant differences in OC levels were measured in benthic amphipods collected at different times. However, concentrations in large zooplankton (>500 μm) collected in August, dominated by adult copepods and ctenophores, contained concentrations of α-HCH, chlordane isomers and other cyclodienes that were two to four times higher than levels in May. Ratios of α-HCH:γ-HCH (5 to 10) were similar to those in seawater collected simultaneously but there was no difference in ratios in various size categories of planktonic and benthic crustaceans indicating no selective accumulation or metabolic alteration of these isomers. Ratios of cis-chlordane:trans-chlordane concentrations were lower in all sizes of zooplankton (2 to 3) than in shelf amphipods (3 to 6) which corresponded to an increase in the ratio with depth. Higher ratios of DDT:DDE in plankton (2 to 6) than in amphipods (1 to 2) reflects the metabolism of DDT to the more stable DDE isomers in amphipods. Metabolites of trans-chlordane were also measured in plankton and benthic amphipods. Although some OCs are degraded or metabolically transformed, accumulation in lipid-rich tissues results in the highest total concentrations in long-lived large-bodied arctic marine organisms.