Less mer­cu­ry in polar bears – due to cli­ma­te chan­ge?

If sea ice is gra­du­al­ly with­dra­wing as a result of cli­ma­te chan­ge, the level of mer­cu­ry in polar bears could decrease.

In an US-Ame­ri­can stu­dy, hair samples of polar bears were inves­ti­ga­ted in the Beau­fort Sea north of Alas­ka from 2004 to 2011. The result: In male ani­mals, the levels of mer­cu­ry decli­ned by about 13% per year, but not in fema­les. This is pro­ba­b­ly due to dif­fe­rent fora­ging habits of the sexes. Fema­le polar bears cha­se main­ly rin­ged seals from the ice, which in turn feed on mer­cu­ry-con­ta­mi­na­ted fish. Male polar bears also feed from land on beard­ed seals and stran­ded bowhead wha­les, which are only slight­ly con­ta­mi­na­ted with mer­cu­ry.

If the ice in the polar regi­ons is now more and more decli­ning due to cli­ma­te chan­ge, polar bears could incre­asing­ly shift their fora­ging habits to prey which can be found on land, e.g. stran­ded bowhead wha­les.

Accor­ding to the stu­dy, the lower con­cen­tra­ti­on of mer­cu­ry in the polar bears is not a con­se­quence of a redu­ced mer­cu­ry con­cen­tra­ti­on in the envi­ron­ment.

Source: ACS Publi­ca­ti­ons

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