Mercury concentrates in eastern Canada and southern Greenland
The flight movements of 837 birds covered the North Atlantic, the Barents Sea and the Kara Sea, and their feathers indicated the distribution of mercury in the food chain. Levels are of particular concern in the western part of this zone.
Eiders, fulmars and guillemots, Arctic birds change their plumage once or several times a year. During the moult, their bodies eliminate some of the mercury in their brand-new plumage. Ornithologists from the Norwegian Polar Institute, the University of La Rochelle and an international network of researchers are well aware of this. In mid-May, they published the first map of mercury distribution in the Arctic and sub-Arctic zone of the North Atlantic, the Barents and Kara Seas, in the journal PNAS. “Our aim was to get a better idea of where the highest concentrations of mercury are,” explains Céline Albert, ecotoxicologist and principal author of the study.
But how did they manage to cover such a wide area from eastern Canada to the Franz Josef Archipelago? The network of ornithologists collected three feathers per bird from a total of 837 birds belonging to seven species between 2014 and 2018, across 27 colonies in seven countries, all along the coast. The birds were fitted with tracking devices during their winter ocean journeys. Eiders foraged close to the coast, mainly on rocky or muddy bottoms. Kittiwakes pecked at the surface of the open sea. Guillemots and little auks dived down to 150 meters and 50 meters respectively, picking up fish in the case of the former and crustaceans in the case of the latter.
Mercury may take an organic form, methylmercury, which enters the food chain. As a result, the birds in question have been exposed to pollution. Thanks to their over-wintering flights, they have indicated that mercury is concentrated in southern Greenland and eastern Canada. Are the concentrations recorded a cause for concern for human populations? “Yes, they are,” says the researcher. “The map evens out the differences in mercury values between bird species, but the raw values oscillate between 0.25 and 14.60 micrograms per gram of feather.” The hazardous threshold is estimated at five micrograms.
“One of the problems with mercury is that it is easily carried by atmospheric and oceanic currents,” explains Céline Albert. The Arctic Council’s AMAP working group is dedicated to monitoring pollution. In its 2021 report, it recommends that the Council’s member and observer states take action and “reduce mercury emissions and discharges.” The authors of the study, several NGOs such as IPEN (International Pollutants Elimination Network) and intergovernmental bodies like the Arctic Council, are calling out to the international community to take new measures concerning the extraction and use of mercury under the Minamata Convention, which came into force in 2017.
Camille Lin, Polar Journal AG
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