Comparison of toxaphene congeners levels in five seal species from eastern Canada:: what is the importance of biological factors?

Environmentally relevant chlorobornanes (CHBs) were measured in blubber samples of harbor (Phoca vitulina), gray (Halichoerus grypus), harp (Phoca groenlandica), and hooded seals (Cystophora cristata) sampled in different part of the St. Lawrence marine ecosystem (SLME) and ringed seals (Phoca hispida) sampled in the eastern Canadian Arctic waters. The purpose of this study was to compare the levels of six CHBs (Parlar-26, -40/-41, -44, -50, and -62) among the five seal species. Seal species could be separated into three groups based on their respective Sigma CHB mean concentrations (+/- standard error): gray (49 +/- 3.9 ng/g lipid weight) and harbor (80 +/- 20 ng/g lipid weight) seals were more contaminated than ringed seals (18 +/- 7.6 ng/g lipid weight) but less contaminated than harp (370 +/- 87 ng/g lipid weight) and hooded (680 +/- 310 ng/g lipid weight) seals. These differences are not expected to be related to different sources of toxaphene contamination, since both the SLME and the eastern Canadian Arctic environments are thought to be mainly contaminated via atmospheric transport from the southeastern part of the United States. Thus, biological factors such as sex, age, nutritive condition, metabolism capacity, and diet of the animals collected were considered. Results reported in this study indicated that the diet is likely the main factor accounting for interspecies variations in toxaphene contamination in seals from eastern Canada.