Scientists have linked the decline in Arctic sea ice to the emergence of a deadly virus that could threaten marine mammals in the North Pacific, according to a study from the University of California, Davis.
Phocine distemper virus, or PDV, has long been a threat to seal populations in the northern Atlantic, along with several strains of influenza, but had not previously been identified in the Pacific. It was first recognised in 1988 following a massive epidemic in harbour and grey seals in north-western Europe with a second event of similar magnitude and extent in 2002. The 1988 outbreak killed thousands of Britain’s seals.1
The 15-year study, published in the journal Scientific Reports, highlights how the radical reshaping of historic sea ice may have opened pathways for contact between Arctic and sub-Arctic seals that was previously impossible. This allowed for the virus’ introduction into the Northern Pacific Ocean.2
Researchers sampled marine mammals for phocine distemper virus exposure and infection from 2001 to 2016. Sampled mammals included ice-associated seals, northern fur seals, Steller sea lions and northern sea otters from Southeast Alaska to Russia along the Aleutian Islands and the Bering, Chukchi and Beaufort seas.
Arctic ocean sea ice and open water routes were assessed from the North Atlantic to North Pacific oceans. Satellite telemetry data helped the researchers link animal movement and risk factor data to demonstrate that exposed animals have the potential to carry phocine distemper virus long distances.
The authors identified widespread infection and exposure to the virus across the North Pacific Ocean beginning in 2003, with a second peak of exposure and infection in 2009. These peaks coincided with reductions in Arctic sea ice extent.
“As sea ice continues its melting trend, the opportunities for this virus and other pathogens to cross between North Atlantic and North Pacific marine mammals may become more common,” said first author Elizabeth VanWormer, a postdoctoral researcher at UC Davis during the study and currently an assistant professor at the University of Nebraska, Lincoln. “This study highlights the need to understand PDV transmission and the potential for outbreaks in sensitive species within this rapidly changing environment.”