Organochlorine residue concentrations and burdens in grey seal (Halichoerus grypus) blubber during the first year of life

Abstract

Between 1988 and 1991 grey seal (Halichoerus grypus) pups at various developmental stages were sampled at Sable Is., NS, and blubber samples were analysed for lipid content and organochlorine (OC) residue concentrations. Blubber lipid content increased significantly between birth and 12 d, and then stayed relatively constant. Blubber OC residue concentrations were fairly constant during the first 12–16 d of life. From weaning (approx. 16 d) until four months, the pups are learning to feed but are relying on blubber fat reserves; thus, during this period blubber weight declined to minimum levels, and OC residue concentrations in blubber lipid increased significantly. Blubber lipid OC concentrations then declined slightly as the pups gained weight, until at the end of one year they were about twice those immediately post‐weaning. Blubber lipid residue burdens calculated from these data showed that at weaning, about 98% of the seal's residues were accumulated from maternal milk. After weaning, there were no significant changes in the burdens of any residue until the end of the first year of the pup's life, and the organochlorine concentration changes reflected a fairly constant organochlorine burden around which lipid contents varied. These data suggest that the capacity of the seal to degrade the residue inherited from its mother is very limited. Furthermore, the absence of any significant accumulation of organochlorines during the second six months of the seal's life suggests that the juvenile seal must feed at a low trophic level which is not highly contaminated with organochlorines.