A U.S. study suggests climate change is putting marine mammals in Haida Gwaii waters at greater risk from algae toxins.
Researchers in Alaska showed for the first time that two of the most common neurotoxins associated with harmful algal blooms — demoic acid and saxitoxin — are spreading to the top of the marine food chain.
Kathi Lefebre, a biologist with the U.S. National Oceanic and Atmospheric Administration who led the study, has said the same risk applies to marine mammals along the B.C. coast.
Lefebre and others found detectable levels of algae toxins in 13 species, including whales, walruses, sea lions, seals, porpoises and sea otters.
All the concentrations were well below food-safety guidelines for people who eat meat from the animals.
Demoic acid and saxitoxin are more common in temperate and tropical regions, where the algae that create them bloom more often and in greater numbers.
But parts of the Bering Sea have already warmed nearly 3 C in the last decade, and retreating sea ice has allowed for more ships that may be carrying algae toxins in their ballast.
Published in the journal Harmful Algae, the study looked at samples from 905 marine mammals that were hunted, stranded, or captured between 2004 to 2013.
About a third had detectable levels of one or both of the toxins.
Demoic acid was found in all 13 species, and in about two-thirds of the bowhead whales and harbour seals.
Saxitoxin was found in 10 species, with the highest prevalence in humpback whales — about half of the humpbacks in the sample had the toxin, which is known as the strongest of paralytic shellfish-poisoning toxins.
While the biologists could not measure any clinical signs of illness in the animals, they noted that the neurotoxins may have been a factor in the ship-strike death of a humpback whale.
In marine mammals, such intoxication is associated with a loss of ability to avoid ships and an increase in stranding.