Trophic transfer of persistent organochlorine contaminants (OCs) within an Arctic marine food web from the southern Beaufort–Chukchi Seas

Abstract

Stable isotope values (δ 13C, δ 15N) and concentrations of persistent organochlorine contaminants (OCs) were determined to evaluate the near-shore marine trophic status of biota and biomagnification of OCs from the southern Beaufort–Chukchi Seas (1999–2000) near Barrow, AK. The biota examined included zooplankton ( Calanus spp.), fish species such as arctic cod ( Boreogadus saida), arctic char ( Salvelinus alpinus), pink salmon ( Oncorhynchus gorbuscha), and fourhorn sculpin ( Myoxocephalus quadricornis), along with marine mammals, including bowhead whales ( Balaena mysticetus), beluga whales ( Delphinapterus leucas), ringed seals ( Phoca hispida) and bearded seals ( Erignathus barbatus). The isotopically derived trophic position of biota from the Beaufort–Chukchi Seas marine food web, avian fauna excluded, is similar to other coastal food webs in the Arctic. Concentrations of OCs in marine mammals were significantly greater than in fish and corresponded with determined trophic level. In general, OCs with the greatest food web magnification factors (FWMFs) were those either formed due to biotransformation (e.g. p,p′-DDE, oxychlordane) or considered recalcitrant (e.g. β-HCH, 2,4,5-Cl substituted PCBs) in most biota, whereas concentrations of OCs that are considered to be readily eliminated (e.g. γ-HCH) did not correlate with trophic level. Differences in physical–chemical properties of OCs, feeding strategy and possible biotransformation were reflected in the variable biomagnification between fish and marine mammals. The FWMFs in the Beaufort–Chukchi Seas region were consistent with reported values in the Canadian Arctic and temperate food webs, but were statistically different than FWMFs from the Barents and White Seas, indicating that the spatial variability of OC contamination in top-level marine Arctic predators is attributed to differences in regional sources of contamination rather than trophic position.