Mercury and cadmium in common cormorants (Phalacrocorax carbo)

Mercury (Hg) and cadmium (Cd) in common cormorants (Phalacrocorax carbo) collected in Lake Biwa, Japan and Tokyo, Japan, were investigated to elucidate the biological behaviors of these elements, and to assess exposure to these pollutants of wild, fish-eating birds. Hg and Cd concentrations were highest in the liver and kidneys, respectively. The lowest levels of both elements were observed in chicks. Hg concentrations in all tissues except brain increased significantly with growth from chicks to juveniles (p<0.05, U-test). Cd concentrations in the kidneys and liver also increased significantly during growth from juvenile to adult (p<0.005, U-test). When comparing hepatic Hg and Cd in adult birds between 10 samples from Lake Biwa and nine samples from Tokyo, the Cd concentrations in the Lake Biwa samples (1.4+/-0.37 microg/g dry wt) (mean+/-SD) were significantly higher than those from Tokyo (0.32+/-0.16 microg/g dry wt) (p<0.005, U-test), while no statistically significant difference was found in the Hg concentrations. Possible causes of these differences were discussed in relation to their prey.