Study links whale feces to algae, climate change

• New paper links bowhead whale feces to climate change
• More than 200 bowhead were sampled over 18 years
• Study is a partnership with the Alaska Eskimo Whaling Commission

From a small office tucked in the University of Alaska Fairbanks Northwest Campus, Gay Sheffield pointed toward a graph updated just that morning. It showed sea surface temperatures in the Bering Sea over the course of the year, with a dark blue line for 2025 consistently outpacing annual averages.

Unlike humpbacks, Sheffield said bowhead whales are more like cattle. They graze the ocean, constantly consuming tiny organisms like krill.

“They don’t have any fancy gulp, they just sieve the water, daah-dum,” she said. “Very calm, more like cattle mowing, constantly feeding quietly. And those krill are full of algae.”

For the most part, the ocean is full of good algae. But there’s also bad algae, which can produce harmful neurotoxins like saxitoxin or domoic acid. Saxitoxin can cause potentially fatal human illnesses like paralytic shellfish poisoning. Five people have died from the illness in Alaska.

Although saxitoxin is a natural part of the ecosystem, it’s becoming a growing concern in Alaska. The reason for that boils down to ocean temperatures. Algae, like other photosynthetic organisms, rely on sunlight, carbon dioxide, and nutrients to survive. But they also need heat.

A graph showing sea surface temperatures observed in the Beaufort Sea. The top ten warmest years are highlighted in red. Rick Thoman graphic.

Rick Thoman, a Climate Specialist with the Alaska Center for Climate Assessment and Policy, said one species of concern, Alexandrium catenella, thrives at ocean temperatures around 46 degrees fahrenheit.

“Once you get ocean temperatures up to that, then things can get going. And as the temperatures get warmer than that, then the rate that these Alexandrium are growing increases very rapidly,” Thoman said.

Thoman is a co-author of the paper and helped chart the sudden uptick in sea surface temperatures across the northern Bering, Chukchi and Beaufort seas. His work revealed that almost all of the top ten hottest years on record came since the turn of the century.

“That’s no surprise to folks that live in the region, and that is being driven in large part by the loss of sea ice,” Thoman said. “Let’s say the first two thirds of the 20th century, ice dominated both seas in most seasons. Not every season, but most seasons.”

The sampling was just part of routine health assessments — but as harmful algal blooms became more frequent, the climate link started to become more and more clear. In 2022, the Bering Sea was home to the largest and most toxic harmful algal bloom event nationwide.

“The 2022 bloom provided a lot of validation for why we should do this. Let’s really look at what we can see and see if we can find this relationship, to be able to share it and know what’s happening and understand the mechanisms,” Lefebvre said.

Every year they ran the study, the researchers found the same thing: the vast majority of whales had saxitoxin in their systems. The toxins are not believed to be harming the bowhead whales themselves, but their growing presence in the food web poses a risk to other wildlife — and to human health.

The study was completed as part of a five-year project through the National Centers for Coastal Ocean Science called ECOHAB. Collaborators from around the world were assembled to complete the study. Sheffield said it truly was a team effort, including the bowhead whales.

“Actually, the whale is telling us something here. And that’s through their relationship with the whaling community. There’s not one person that could have pulled this paper off. It took everyone working together,” Sheffield said.