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Canada's Arctic Ocean: a complex and changing ecosystem

by Mark Sabourin
EcoLog, 5/1/2020 10:10:00 AM

Scientists are just starting to figure out Arctic ecosystems. The first status report on Arctic Ocean ecosystems, “Canada’s Oceans Now: Arctic Ecosystems 2019”, the second of three to examine the ecosystems of Canada’s three bordering oceans, was released on Earth Day (April 22, 2020) and paints a fascinating, if somewhat confused, picture. (The report on Atlantic Ocean ecosystems came out in June 2019.)

There’s more open water. Seasonal ice is showing up later and melting earlier. Ice is thinning, but not evenly.

The availability and stability of sea ice as a platform is decreasing. This is linked to skinnier polar bears and ringed seals in Hudson Bay. As a result, polar bear populations are declining in Hudson Bay, but there are no evident declines in ringed seal populations.

The changing ice conditions are having an impact on the food web. Arctic Char are migrating to ocean waters in the Western Arctic earlier in the year. This allows them to feed longer in ocean waters, and there is evidence of improvement in Arctic Char growth in some coastal areas of the Beaufort Sea. Belugas have also been able to migrate earlier to Hudson Bay and to leave later. However, the early ice breakup has meant that ringed seals have not been able to complete their moult, leaving them more susceptible to disease.

One of the clearest examples of the complex interaction between climate and species is illustrated by the Common Eider. The longer open water feeding season has supported Common Eider breeding in Hudson Bay. More eggs are being laid. That, in turn, is helping support polar bears, which have turned to nest predation as an alternative to seals, their preferred prey, which are no longer as readily available.

The report also demonstrates how little we truly know about the Arctic Ocean ecosystems. It says that large differences occur naturally from year to year and from decade to decade. To identify trends, at least 20 years of data are needed. This report is a start.

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