Beluga whale pod in the Chukchi Sea | Laura Morse (NOAA)
CHICAGO—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.
Stephen Raverty and Michael Grigg discuss the health of beluga whales in the Arctic. | AAAS/Carla Schaffer
Although the physics behind climate change are becoming increasingly clear, the science behind how climate change impacts ecosystems is still very complicated, said Chris Field, director of the department of global ecology at Carnegie Institution for Science.
“You can think about the rate of climate change in terms of degrees per decade, but if you’re an organism or an individual that needs to adapt, then you really want to think about it in miles per hour,” Field noted. “How fast do you need to move your activities in order to stay in a zone of acceptable climate?”
At the high rates of climate change that have been predicted for the 21st century, species may need to move on the order of a few kilometers per year, and in some cases up to 20 or 30 kilometers per year. But data suggest that plants and animals historically have only been able to shift at a rate of a few hundred meters per year, Field said.
For some marine mammals, there are fewer places to move. “We’ve lost roughly 75 percent of multiyear ice” that doesn’t melt through at least two summers, said Sue Moore, a biological oceanographer with the U.S. National Oceanic and Atmospheric Administration. “Essentially, since 2007 in the Pacific Arctic region, if you’re a marine mammal that requires ice like the polar bear or walrus, it’s gone. Your platform has left and you have to change.”
“The animals themselves are telling us what’s going on in this system. They’re sending us that message. We have to get better at interpreting it and bringing together the science of marine mammal health and marine mammal ecology,” Moore said.