Ringed seals are among the most common marine mammals in the Canadian Arctic. They strongly rely on sea ice as a habitat, breathing through holes they maintain in the frozen surface, giving birth in snow lairs and diving beneath the ice to hunt Arctic cod and small crustaceans.

They are also a key prey for polar bears and an integral part of Inuit culture, providing nutrition, cultural continuity and a generations-long connection to land and sea.

However, our new study shows these seals are being affected by chemical pollution in the Arctic food web and rapid climate-driven warming that is transforming their sea ice habitat. Each of these pressures is serious on its own, but together they are undermining seal health in ways now detectable at the molecular level.

Our research focused on ringed seals along the northern Labrador coast of Canada, near Saglek Bay, a site with a long industrial legacy. A former military radar station operating since the 1950s left behind a hotspot of polychlorinated biphenyls (PCBs) that has impacted the ringed seal.

A chemical legacy stored in fat

PCBs are 209 chlorine-based chemical compounds that are highly toxic. They were produced in large quantities worldwide from the 1920s to late 1970s for use in industrial electrical equipment and commercial products.

Despite being banned for decades, they still remain highly persistent in the environment. PCBs do not break down easily. They bind to fat, move through food webs and accumulate in animals like seals, whales, and ultimately, people who rely on marine mammals for food.

When we sampled seals near Saglek Bay between 2009 and 2011, PCB concentrations remained high, averaging over 700 nanograms per gram of blubber fat. Alongside PCBs, we also detected........

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