Hidden consequence of climate change: Deadly virus is killing key marine species

(Photo By Brice Laine/CNN)

Climate change means melting ice and habitat loss for animals in the Arctic. But there’s an invisible side effect of warming temperatures and rising tides, and it’s killing key marine species.

Melting Arctic sea ice has opened new pathways for Arctic and sub-Arctic species to interact, and that contact has introduced a potentially deadly virus to mammals in the Northern Pacific Ocean, according to a new study in Scientific Reports.

Over 15 years, researchers identified two new channels linking the Atlantic and Pacific oceans between Russia and Alaska. Animals who live there are interacting for the first time, creating a reservoir of the deadly pathogen Phocine distemper virus.

The virus, also called PDV, was first identified in European harbor seals, killing thousands in 1988 and again in 2002. It reemerged in 2004, but this time in northern sea otters in Alaska.

It was surprising that the disease jumped to a different species in a different ocean, said study author Tracey Goldstein, associate director of One Health Institute at UC Davis School of Veterinary Medicine. It’s what led scientists to believe that melting ice was to blame for the infection’s spread.

“Animal health and human health and environmental health are so linked, if one deteriorates then the rest do, too,” she told CNN.

Infection peaked when ice was at its lowest

To evaluate the extent of the infection, researchers took nasal swabs and blood samples from more than 2,500 ice-dwelling seals, Steller sea lions and northern sea otters from Alaska to Russia living in its marginal seas and oceans.

Widespread exposure to the infection peaked twice, in 2003 and 2009. Both outbreaks were preceded by record-low sea ice, Goldstein said.

Ice is essential for marine mammals, she said. It’s where they breed, rest and give birth. When water temperatures warm, their food likely travels deeper into the ocean, so animals are traveling further to catch them, spreading the pathogen across large swaths of northern seas.

Animals can’t keep up with the rate of their rapidly changing environments, Goldstein said, and that makes them more susceptible to disease.

PDV has already impacted people

Goldstein compared PDV to measles in humans — both are highly contagious respiratory diseases that spreads easily through contact (though PDV doesn’t infect humans).

But it’s already indirectly impacted humans who rely on the animals. It’s harder for Alaskans to hunt and maintain their livelihood as seals and fish move further off-shore, she said.

Because the Arctic is so remote, it’s difficult to discern how many species have died from the virus since the start of the study, she said. Some, particularly European harbor seals, are more vulnerable than others — up to 50% of the harbor seal population died in the first two outbreaks, she said.

Outbreaks occur every five to 10 years, typically when ice is at its lowest. Sea ice cover in the Arctic hit its second-lowest level in 2019, according to NASA — and that could mean new paths opened up, linking animals in both oceans and increasing the likelihood of the virus’s reintroduction.

Eliminating the virus may be impossible, but humans can at least stall its spread, Goldstein said. Reducing the global carbon footprint can slow the effects of climate change and give animals a chance to catch up and adapt.

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