Mercury Accumulation in fishes from North-East and North-West Barents Sea during the polar night

Anjali Gopakumar

In this study, we quantified total mercury (Hg) concentrations and dietary descriptors in three Arctic and sub-Arctic fishes sampled during the polar night, to study their interspecific and spatial bioaccumulation patterns in the Barents Sea food web. Hg and carbon and nitrogen stable isotope ratios (δ13C and δ15N) were analyzed in the muscle tissue of polar cod (Boreogadus saida), Atlantic cod (Gadus morhua) and capelin (Mallotus villosus), sampled from the North-West and North-East parts of the Barents Sea.

Hg concentrations varied greatly among individual fish, but were in general, well below the EU-accepted threshold of fishes for human consumption of 0.5 µg/g (wet weight).  Hg concentration was found to significantly increase along δ15N and from pelagic to benthic fishes. In the North-East Barents Sea, Atlantic cod had the highest Hg concentrations, reflecting its high trophic position and benthopelagic feeding. When spatially comparing polar cod between the two locations, individuals from the North-East had higher Hg concentrations. These variations were partly explained by the larger size of polar cod from the North-East bioaccumulating more Hg, and partly by local influences. Atlantic cod were not spatially compared, owing to the considerable difference in sizes and trophic positions between the locations.