Geographical distribution of metals in livers of polar bears from the Northwest Territories, Canada.

Levels of Ag, Ca, Cd, cu, Fe, Hg, K, Mg, Mn, Na, P, Se and Zn were determined in livers of polar bears collected in 1984 in six zones in the Lancaster Sound. Baffin Bay and Hudson Bay areas of the Northwest Territories of Canada and compared with data collected in 1982 for the western part of the Canadian Arctic. Only levels of Cu, K and Zn were found to have no statistically significant differences among zones. The lowest levels of Ca, Fe, Mg, Mn, Na and P were found in the western Arctic, but geographical differences were probably inconsequential. Cadmium levels were significantly lower in the western Arctic zones than in the other areas, and reverse was true for levels of Hg and Se. Levels of Cd, Hg and Se in polar bear liver were positively correlated with age, whereas K, Mn, Mg and P were negatively correlated with age. Iron was significantly higher in females than males. Rates of accumulation of Cd with age were 2 3 times lower in polar bears from zones west of approximately 95 degrees W than the other areas, whereas Hg and Se rates of accumulation were about 7 and 10 times higher in bears from the zones near the Beaufort Sea than from Hudson Bay. The Hg/Se molar ratios averaged 1.10 +/- 0.19 for most of the surveyed zones excluding Hudson Bay, where the average ratio was almost two-fold higher (2.13 +/- 1.58). It is probable that natural variation in Hg levels in the marine environment due to geological or atmospheric deposition factors, and differences in polar bear feeding ecology among zones, account for the differences in the geographical distribution of Hg. The distribution of Cd is more likely to be related to differences in feeding ecology of the bear's principal prey, the ringed seal.