Levels and patterns of PCBs and OC pesticides in harbour and grey seals from the St Lawrence Estuary, Canada

Abstract

Blubber samples from harbour ( Phoca vitulina) and grey seals ( Halichoerus grypus) captured in the St Lawrence Estuary were analysed for PCBs and OC pesticides. Concentrations of ∑PCB, ∑DDT, ∑CHLOR and mirex were higher in harbour than in grey seals, while ∑HCH and HCB were similar in the two species. Age vs. concentration plots showed that ∑PCB, ∑DDT and ∑CHLOR concentrations increased with age in males, but plateaued at sexual maturity in females. Concentrations of ∑HCH decreased and mirex increased with age for post-weaning animals, regardless of gender. HCB did not show age-related trends. PCB congener and OC pesticide patterns varied within harbour seals (based on gender and maturity) and between harbour and grey seals. PCB and OC concentrations in harbour seals were lower than those seen in a sample of significantly older beluga whales. Both species remain in the Estuary year-round. PCB and OC pesticide concentrations were higher in resident harbour seals than in either grey or harp seals that visit the Estuary seasonally. PCB and OC pesticide concentrations in harbour seals from the Estuary were generally higher than in harbour seals from other regions of North America. They were comparable to, or higher than those from the NE Atlantic Ocean and the North Sea, and lower than those from the Wadden and Baltic Seas.