Heavy metals in tissues of Atlantic (Odobenus rosmarus rosmarus) and Pacific (Odobenus rosmarus divergens) walruses

Walrus occupy a high trophic level in the Arctic ecosystem, while being an important source of food for the native population of the Arctic coast. The concentrations of six heavy metals—mercury, cadmium, lead, copper, manganese, and nickel in the skin of Atlantic walrus (Odobenus rosmarus rosmarus) and in the skin, heart, lungs, liver, kidneys, and muscles of Pacific walrus (Odobenus rosmarus divergens) was measured. Animals of different ages and both sexes were studied, including mother–calf pairs. Samples from O. r. divergens (n = 29) were collected in 2019 in the area of Lorino village (Chukotka) during the aboriginal hunt and from O. r. rosmarus (n = 27) from Oransky Islands and Franz Josef Archipelago. Concentration of all six metals was 1.8–7.5 times higher in the skin of O. r. rosmarus animals relative to the O. r. divergens. Studies of organ tissues of O. r. divergens have shown increase in the level of Hg in the liver and kidneys. In the mother–embryo and mother–calf pairs, embryo and calf had higher concentrations of cadmium, lead, copper, and manganese than their mothers. Since a higher amount of mercury and cadmium was found in the liver and kidneys of adult O. r. divergens, it is not recommended for indigenous people to consume these organs from older animals.