Spatial distribution of persistent organochlorines in ringed seal (Phoca hispida) blubber

Blubber samples, taken through the entire blubber column, were collected from three different anatomical locations on ringed seals (Phoca hispida). The outer and inner layers of these samples were analysed for concentrations of sigma PCBs (sum of the analysed congeners, polychlorinated biphenyls) and p,p'-DDE (4,4'-dichlorodiphenyldichloroethylene). No significant differences were found in blubber thickness or in per cent extractable lipid when comparing age- and sex-groups, or in extractable lipid content when comparing anatomical locations of the blubber or blubber depth. No significant differences were found between the three different anatomical locations with respect to the concentrations of sigma PCBs or p,p'-DDE. However, the concentrations of both sigma PCB and p,p'-DDE were significantly higher in the outer blubber layer compared to the inner. Higher levels of both sigma PCB and p,p'-DDE were found in males compared to females and juveniles in both the inner and outer parts of the blubber column. The most commonly used blubber sampling devices are biopsy tools that penetrate only the outer layer of the blubber. Analyses of such samples will not reflect the real body burden of organochlorines. Standard methods for sampling blubber of marine mammals should be developed so that comparative studies and longitudinal monitoring programs of pollutants in marine mammals can be conducted in a meaningful way.