Arctic's Big Thaw opens the way for hazardous microbial migration

The direct impact of climate change on Arctic marine mammal health is still unclear, but there are signs that warmer temperatures are producing a “new normal” in the region.

In the middle of the Arctic’s big thaw, marine mammals and micro-organisms that sicken them are both on the move.

Beluga whales now carry a cat parasite that wasn’t seen in the Arctic before 2006, and Atlantic gray seals are being killed by a new parasite that they may have caught from their northern neighbors, the ringed seals, researchers said at the AAAS Annual Meeting.

The scientists acknowledged that climate change’s role in both of these events is still unclear. But they suggested that the findings indicate a “new normal” for Arctic environments.

Michael Grigg, chief of the molecular parasitology unit at the National Institutes of Health, said that a new parasite related to the Sarcocystis canis parasite found in dogs may have been “liberated from the Arctic to move south” with the disappearance of ice barriers.

The parasite doesn’t affect the health of its Arctic ringed seal hosts. But it has been deadly for some Atlantic gray seals that recently chased their fish food into more northern waters, putting them in contact with the ringed seals. In March 2012, Grigg said, 406 gray seals died of a tissue-wasting hepatitis caused by the new parasite.

Since then, a Steller sea lion and a few endangered Hawaiian monk seals have also been killed by the new parasite. “Will we continue to see more mortality events as we see marine mammals from the south Arctic moving to these polar waters?’” Grigg asked, comparing the possibility to the spread of the Black Death into Europe in the 14th century.

Grigg and others have also discovered Toxoplasma gondii, a parasite shed in cat feces, in Arctic beluga whales. He said an increase in the cat and dog population in the Arctic may have brought the parasite north. But T. gondii is also notoriously difficult to kill—Grigg’s lab stores the parasite in sulfuric acid—and one of the only ways to keep it in check is to freeze it.

“With increasing temperatures, there’s going to be an increased potential for exposure because you’ve got longer times in which these infectious oocysts will remain viable,” Grigg said.

Grigg and Stephen Raverty, a veterinary pathologist at the British Columbia Ministry of Agriculture and Lands, said they are keeping an eye on beluga populations to discover whether other infectious agents may pose a risk to the whales and to the Inuit populations that eat them.

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