Melting sea ice opens northern passage for marine mammal disease
Melting sea ice on its own presents plenty of challenges for Arctic marine mammals, from loss of habitat, to changing predator prey dynamics.
But now, there's a new challenge.
Biologists recently discovered a link between believe sea ice loss and the spread of disease between previously isolated populations.
Phocine Distemper Virus is known for causing mass mortality in seals in the Atlantic and was discovered in northern sea otters in Alaska in 2004.
"We were collecting sea otter carcasses across the state just to look at patterns of mortality," said Verena Gill, a biologist with NOAA Fisheries. Gill was working for US Fish and Wildlife Service at the time. "While we were investigating sea otter deaths, we discovered that they had been exposed to phocine distemper, and that sort of set off a whole question of how do sea otters contract this phocine distemper, which previously had only been seen in the Atlantic."
The discovery prompted a project with several federal agencies and university researchers that spanned 15 years. Biologists collected samples from more than 2,500 animals including ice seals, Steller sea lions, northern fur seals and northern sea otters.
"There were two sort of outbreaks that seemed to erupt, and they coincided with years of very low sea ice up in the Arctic," Gill said. "And then we looked at satellite tracking and we realized that animals were moving, could potentially move between the Atlantic and the Pacific and then transmit the virus."
The disease can be fatal. It causes animals to have breathing difficulties and may also lower their immune system so they become more prone to other diseases or impacts, Gill said.
Biologists are concerned about potential negative impacts on animals populations that have not been exposed to the virus before.
"There are many things that we may not think about with climate change. We definitely think about low ice and loss of habitat, but do we think about things like disease being transmitted from one previously isolated ecosystem to another? And we don't know how that disease is going to impact animals that have never been exposed to it before. It has the potential to completely wipe out a population," Gill said.
Biologists have vaccinated some of the most endangered populations, such as the Hawaiian monk seal, to protect the herd, but Gill says that approach is not appropriate on a larger scale.
"I think it's quite frightening. We have the potential to really reduce some populations that are already facing a lot of other threats," Gill said. "It's definitely showing us that things are changing and we need to be aware of the many multifaceted impacts that we might not have thought about before."
In September NOAA Fisheries declared an Unusual Mortality Event due to elevated stranding of ice seals in the Arctic. Gill says that event has not been linked to phocine distemper virus.