Levels of non-essential elements in muscle from harp seal ( Phagophilus groenlandicus) and hooded seal ( Cystophora cristata) caught in the Greenland Sea area

Abstract

The non-essential elements, arsenic, cadmium, mercury and lead, inevitably accumulate in marine top predators such as seals. The concentration of these elements and the essential element selenium, due to its proposed protective properties against mercury toxicity in marine mammals, were measured in muscle, liver and kidney from reproductive active females of harp seal ( Phagophilus groenlandicus) and hooded seal ( Cystophora cristata) caught in the drift ice between Iceland and East Greenland. Arsenic levels were below 1 μg/g w.w. in all analysed samples, and were therefore low compared to other seafood products. The concentrations of arsenic found in the present study were comparable to the results reported in a similar study from 1985. Mean concentrations of total mercury in muscle from the present study were higher than levels in other seafood products. The levels of total mercury from the present study showed a tendency of lower levels in all tissue samples compared to the study from 1985. Methyl mercury displayed a trend of a lower ratio of methyl mercury to total mercury as the concentration of total mercury increased, indicating a demethylation of methyl mercury at high total mercury concentrations (e.g. mercury in liver of hooded seal). The concentration ratio of methyl mercury to total mercury in muscle samples was more than 75%, with total mercury concentration less than 0.5 μg/g w.w., whereas the ratio for liver was as low as 0.2% with a total mercury concentration of 128 μg/g w.w. The molar concentration ratios of selenium to mercury showed that selenium was present in a molar surplus to mercury in all tissues with low mercury concentration. However, there seemed to be a general mobilisation of selenium in liver and kidney tissues of harp seal and hooded seal, whereas an extraordinary mobilisation seemed to take place at hepatic mercury concentrations exceeding 50 μg/g w.w. The mean concentrations of lead in muscles in the present study were higher than in fish and other seafood products from the Barents Sea. The lead concentrations from the present study were lower than levels reported in the 1985 study. However, the levels of the non-essential elements analysed in muscle from the two seal species in the present study should not prevent the use of seal meat in human nutrition.