Mercury in tissues of Dall's porpoise (Phocoenoides dalli) collected off Sanriku coast of Japan

Tissues of Dall's porpoises (Phocoenoides dalli) collected off Sanriku coast of Japan were analyzed for investigation on bioaccumulation of total mercury (Sigma Hg) (n=22; male:11, female:11) and methyl mercury (MeHg) (n=1, adult female) by cold vapor MS. High Sigma Hg level was in the liver and kidney. Moderate levels were observed in cerebrum, muscle, heart, stomach, cerebellum, pancreas, spleen, lung, skin and intestine, and low concentrations in bone and blubber. MeHg level was also highest in the liver, followed by muscle, heart, cerebrum, skin, stomach, spleen, cerebellum, kidney, pancreas, intestine, lung, blubber and bone. Comparing with previous studies, Sigma Hg levels in tissues of present study tended to be similar to those of Dall's porpoise from Pacific areas, but higher than those of individuals from Bering Sea and the Sea of Japan. Hepatic Sigma Hg concentrations suggested that Hg contamination level in this species is relatively lower. MeHg proportion to Sigma Hg implied demethylation might be stronger in some visceral organs, such as liver, kidney, and lung.