A deadly virus affecting seals, seal lions could spread as sea ice levels decline, scientists say

Scientists say that a deadly virus that has already spread from one ocean to another has the potential of circulating further as sea ice levels continue to decline.

Phocine distemper virus (PDV) affects fin- and flipper-footed mammals such as seals, sea lions and otters.

Using satellite imagery, researchers documented its spread over 15 years. The results were published Thursday in the journal Scientific Reports.

The researchers gathered samples from 2,500 marine mammals from 2001 to 2016. They found that as water routes began to periodically open up between the North Atlantic and the North Pacific, infections of the virus spiked.

“The loss of sea ice is leading marine wildlife to seek and forage in new habitats and removing that physical barrier, allowing for new pathways for them to move,” Dr. Tracey Goldstein, one of the authors of the study, told BBC News.

“As animals move and come in contact with other species, they carry opportunities to introduce and transmit new infectious disease, with potentially devastating impacts.”

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PDV was observed to have caused extensive deaths to harbour seals in both 1988 and 2002 in the North Atlantic.

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According to the study, PDV was confirmed to have spread to the North Pacific in 2004 to Stellar sea lions, most likely due to a record ice melt in 2002. Over 30 per cent of sea lions tested were found to carry the virus.

The virus declined in the years that followed but would peak again in 2009 after another record ice melt in 2007 opened up water routes, facilitating the spread of the virus.

Arctic sea ice has declined at an average rate of 12.8 per cent each decade between 1979 and 2018, according to the Intergovernmental Panel on Climate Change (IPCC).

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“It is very likely that Arctic sea ice extent continues to decline in all months of the year; the strongest reductions in September are likely unprecedented in at least 1,000 years,” the IPCC said in their Ocean and Cryosphere policy report, published in September.

“It is virtually certain that Arctic sea ice has thinned, concurrent with a shift to younger ice: since 1979, the areal proportion of thick ice at least five years old has declined by approximately 90 per cent.”