Bowhead whales are ingesting toxins driven by warming in Arctic, study finds

Whales’ bowel samples include algal toxin that causes a condition that can be fatal to human beings

A long-term study of bowhead whales in Alaska published this week points to a direct correlation between ocean warming and threats to the Arctic food web.

An interdisciplinary team of scientists, collaborating with Alaska Native whale hunters and other North Slope residents, studied bowel samples taken over nearly two decades from 205 subsistence-harvested bowheads, looking for evidence of toxins from algae.

Produced by algal blooms, saxitoxin can cause paralytic shellfish poisoning, an often agonizing and untreatable condition that can be fatal in humans. They also found varying levels of domoic acid, another neurotoxin produced by algal blooms, a phenomenon increasingly common in northern waters.

Warming Arctic conditions resulting from climate change are increasing the prevalence and concentration of neurotoxins in the whales’ poop, researchers found. These conditions include shrinking sea ice, expanding tracts of open water and more sunlight penetrating the ocean’s depths.

“We have a direct relationship between higher toxin concentrations and warmer ocean conditions,” said Kathi Lefebvre, the paper’s lead author and a research biologist with the National Oceanic and Atmospheric Administration in Seattle. “There is a very strong mechanistic link.”

Marine biologists consider whales a sentinel species because they feed throughout the water column by scooping up tiny crustaceans, namely krill and copepods.

“They’re going through the ocean basically with their mouths open,” said Rick Thoman, a climate scientist at the University of Alaska Fairbanks and co-author on the paper. “They’re not selective. What’s ever in that water, what’s ever in that krill, they’re ingesting into their bodies.”

Understanding what’s inside these filter feeders unlocks knowledge about what’s happening in the ocean and food web.

“They’re a good proxy for what’s in the environment,” Thoman said.

Through prior research, scientists already knew that melting sea ice and growing tracts of open water spur proliferation of two marine algal species, Pseudo-nitzschia and Alexandrium catenella. These algae produce domoic acid and saxitoxin respectively, nerve toxins that accumulate in creatures like clams, krill, plankton-eating fish and zooplankton.

These organisms, in turn, pass the poisons on to larger marine wildlife or humans who eat them.

There’s no evidence that the levels of neurotoxins found inside the bowheads pose any human health risk, Lefebvre noted.

But because the whales are a sentinel species, the results from 19 years of fecal samples are worrisome, especially in a remote region where residents heavily depend on ocean animals for a huge portion of their diet and in a place where temperatures are accelerating nearly four times faster than the rest of the world.

The 10th-warmest set of ocean temperatures in northern Alaska waters since 1900 have been recorded since 2000. As the ice melts, warmer waters are pushing northward, leading to cascading effects on marine ecosystems, according to previous research. Given those trends, scientists expect the prevalence and concentration of neurotoxins in whales and other species to increase over time.

Some of the world’s largest beds of Alexandrium cysts already exist in northern Alaska waters, according to the study. Until recently, cold ocean temperatures prevented algal cysts, or seeds, from germinating. But that’s radically changed in the last 10 or so years as ocean warming has accelerated.

To understand the dynamics of how ocean temperatures influence toxin levels, scientists used a mooring in the Beaufort Sea, about 93 miles east of Point Barrow, that’s been maintained since 2002. Researchers outfitted the mooring with an array of instruments to monitor water temperature, velocity and other metrics.

The data showed that whales feeding in warmer spots had higher concentrations of algal toxins. And in places with big stretches of open water with sunlight penetrating, algae grow more quickly, boosting the odds of whales ingesting toxin-laden krill and other food.

Besides finding that anywhere between 44% and 100% of fecal samples contained saxitoxin, the scientists also found between zero and 100% of samples had domoic acid present. Domoic acid can cause amnesic shellfish poisoning, a condition that can cause seizures and coma.

Given the overall direction of where conditions seem to be headed, there’s an urgent need for greater surveillance of algal blooms, marine mammals and other ocean species, said Gay Sheffield, a marine biologist and extension agent with Alaska Sea Grant, a partnership between NOAA and the University of Alaska Fairbanks.

A study co-author, Sheffield said there’s been too many deaths and close calls already with people eating clams, crab and other ocean foods containing dangerous levels of neurotoxins.

Five people in Alaska died of paralytic shellfish poisoning in 1994, 1997, 2010 and 2020, according to a bulletin from the state epidemiologist. During the time period from 1993 to 2021, the epidemiology section reported 79 total incidents.

Paralytic shellfish poisoning is a condition to be avoided at all costs. Mild symptoms can include tingling, difficulty swallowing, dizziness and muscle weakness. If the condition worsens, it can lead to brainstem dysfunction, respiratory failure and death.

“There is no antidote for people. You just have to ride this out. It’s palliative care. You have to ride it out. You get IVs, you’re throwing up and you’re pooping. You’re peeing it out. But it’s a strain on your intestine, liver and kidneys,” Sheffield said.

Of the patients for whom race was recorded, more than half were Alaska Native, according to the bulletin.

While changing conditions in Alaska’s Arctic are stressful and cause for concern, one positive trend Sheffield points to is that diverse communities are now actively working together, sharing data and traditional ecological knowledge, and otherwise collaborating to find solutions and to protect public health and the food web.

The whales in the study were harvested by subsistence hunters from the Beaufort Sea region between 2004 and 2022. Eleven bowhead whaling communities participated, along with the Alaska Eskimo Whaling Commission and the North Slope Borough, through its bowhead harvesting management program.

“Through the Alaska Eskimo Whaling Commission, the North Slope Borough Department of Wildlife Management, and the (whaling) captains’ associations for the Beaufort Sea, we have access to the whales,” for study purposes, said Sheffield. “It’s like giant teamwork.”

Lefebvre and others on the research team are gearing up for their next research project, which she said will expand the search for algal toxins in other marine species used for food, including walrus.

Although government downsizing and funding cuts have thrown many federally funded research projects into doubt, Lefebvre is crossing her fingers that algal toxin work in Alaska’s Arctic will continue.

“I know it’s of great importance to lots of people,” she said.

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