Fecal samples from bowhead whales link ocean warming to rising algal toxins in Arctic waters
Filter-feeding whales sample the Arctic food web, tracking decades of change.
Woods Hole Oceanographic Institution
image:
Aerial view of six bowhead whales traversing the Beaufort Sea.
view more
Credit: Photo credit: Amelia Brower NOAA Fisheries/AFSC/MML, Seattle, WA, 98125 USA & North Slope Borough. National Marine Fisheries Service (NMFS) Permit No. 14245
Woods Hole, Mass. (July 9, 2025) -- Rising toxins found in bowhead whales, harvested for subsistence purposes by Alaska Native communities, reveal that ocean warming is causing higher concentrations of algal toxins in Arctic food webs, according to new research published today in the journal Nature.
Researchers from the Woods Hole Oceanographic Institution (WHOI), were a part of the multi-institutional, multi-year study that focused on this critical issue, which threatens food security for coastal communities that rely on marine life, including clams, fish, and whales, for food and other resources. Communities in Alaska are now asking researchers to help them understand and monitor the emergence of algal toxins in the Arctic ecosystems that they depend on.
“These are new risks that were previously unknown,” said Kathi Lefebvre, a research scientist at NOAA Fisheries’ Northwest Fisheries Science Center in Seattle and lead author of the new study. “The people in remote communities in northern and western Alaska rely on marine resources for nutritional and cultural well-being. Now we’re finding that these resources are at risk.”
“Native communities know intimately the ecosystems they rely on and were among the first to recognize the effects of warming,” said Raphaela Stimmelmayr, a wildlife veterinarian with the North Slope Borough in Barrow, Alaska, and a coauthor of the new research. She said the communities now need reliable tools such as field tests, so they can test for the presence of algal toxins in traditional foods in real-time. These tests, as well as information from monitoring programs and instruments, also help them make informed decisions on whether the marine mammals or other marine wildlife—such as clams, fish, and birds—are safe to eat.
“It is very difficult to walk away from resources that they need and have relied on since time immemorial,” she said.
WHOI senior scientists Don Anderson and Bob Pickart, as well as Anderson’s graduate student Evie Fachon, are part of this study, as well as other investigations focused on the oceanography and bloom dynamics of the algal species that produce these dangerous toxins.
In addition to running an active research program, Anderson leads the US National Office for Harmful Algal Blooms based at WHOI, whose mission is to facilitate coordination and communication of activities for the U.S HAB community at a national level. One of those activities was assisting with the publication of a national science strategy for the research and response of HABs.
“I have shifted a significant portion of my lab’s research focus to the Alaskan Arctic in recent years,” said Anderson. “It is a new frontier in HAB research given the rapid warming of waters in the region and the massive scale of the Alexandrium populations we have documented”.
That research has revealed that the world’s largest beds of Alexandrium cysts, which are dormant cells of the toxic algae, lie on the seafloor sediments of the Alaskan Arctic. These cysts accumulate over time as blooms that originate in the Bering Sea drift northward and deposit their cysts in cold waters like those of the Chukchi Sea, where frigid bottom temperatures have historically suppressed germination.
“For years, these cysts have remained inactive, essentially preserved by the cold,” explained Anderson. “But as bottom water temperatures periodically warm, we see conditions that allow germination, and that changes the risk landscape dramatically.”
The local cyst germination represents a second source for blooms of this species that augment the episodic transported blooms from the south. These two bloom mechanisms are consistent with studies conducted by Anderson, Pickart, and Fachon documenting massive cyst accumulations (cyst beds) in Alaskan Arctic waters, as well as equally massive blooms of the cells in surface waters.
Warming conditions could trigger local blooms from these long-dormant cysts, increasing the threat to Arctic ecosystems and coastal communities from the potent neurotoxins the algae produce.
In this new study, Pickart and his former postdoc Peigen Lin, now at Shanghai Jao Tong University, analyzed currents and water properties through time, demonstrating a critical linkage between warming temperatures and the bowhead toxicity.
“My Arctic research has become increasingly interdisciplinary over the years, including exploring the role of circulation patterns, atmospheric forcing, and water properties in HAB dynamics,” Pickart explained.
Whales collect samples
NOAA’s Lefebvre leads the Wildlife Algal-toxin Research and Response Network for the U.S. West Coast. This alliance of agencies and institutions collects wildlife tissue samples from as far North as the Beaufort Sea in Alaska to Southern California. Members then send the samples to her Seattle lab to test for the presence of algal toxins. The lab’s early work found that many species in Alaska had evidence of exposure, although not at levels high enough to be considered harmful to the animals sampled.
Over two decades, the lab regularly tested bowhead whales harvested during annual fall subsistence hunts in the Beaufort Sea off the North Slope of Alaska. The whales filter seawater for their food, consuming krill that contain algal toxins acquired from the food web. The research team realized that fecal samples from the whales could reveal toxins in the marine environment the whales depend on.
“Nobody had a data set like this,” Lefebvre said. “Instead of going out every year and collecting samples across the marine environment, the whales did it for us. Their samples give us a snapshot of what is in the food web every year, as sampled by the whales.”
After testing 205 bowhead whales over 19 years from 2004 to 2022, the team decided they had enough data to look for changes over time. In particular, they wanted to track the concentrations of domoic acid, produced by a marine algae called Pseudo-nitzschia, and saxitoxin, produced by Alexandrium.
They found saxitoxin in at least half to 100% of the bowhead whales sampled each year over 19 years. While domoic acid was less prevalent (in some years no DA was detected), this study shows for the first time that domoic acid exposures in Arctic waters are increasing due to warming and loss of sea ice.
Winds, Currents, and Ice Cover Affect Toxins
Scientists used data from a monitoring mooring in the Beaufort Sea, funded by the National Science foundation’s Arctic Observing Network, to compare toxins in the bowhead whales to environmental conditions. “It was fortuitous that we’ve maintained a long-term mooring near the whale feeding site, which provided the opportunity to investigate the role of the changing circulation and water properties over this two-decade period,” said Pickart. The researchers found that periods of increased toxicity in the whales were associated with enhanced northward heat flux, which in turn was driven by specific wind patterns.
These warmer conditions are more favorable for HAB growth and are correlated with higher toxin concentrations in the food web. Atmospheric conditions thus influence the oceanography which in turn influences the HAB dynamics.
They also used climate data to compare the bowhead samples to changes in sea ice. Sea ice historically covered large sections of the Arctic but has radically declined in recent decades. When there is less sea ice, sunlight warms the ocean more quickly and algae grow faster. Years with the largest reductions in sea ice cover in June led to warmer water in July. This boosted the odds of HABs and rising toxin levels in the whales. Warmer ocean conditions and loss of sea ice are all linked to higher toxin levels in the food web.
“As an early career researcher, I never got to see what a “normal” arctic should look like,” said WHOI”s Fachon. “Learning about these blooms alongside scientists who have been working in the region for decades has really impressed upon me the novelty of HABs in this part of the world.”
This extensive research was accomplished through decades of collaboration among researchers from tribal, state, and federal governments, academic institutions, and private organizations. Arctic science is best when there is teamwork amongst Native and western science. The research team included specialists in Arctic traditional ecological knowledge, oceanography, climatology, HABs, food web ecology, and experts in bowhead whale health and ecology. These researchers were able to fill in a piece of the Arctic HAB risk puzzle. This study confirms the need for continued and increased monitoring of HAB risks to food security and food safety of marine subsistence resources used by rural Alaskan communities.
Image shows the harmful algal cells that produce potent neurotoxins described in study: Pseudo-nitzschia (cigar shaped diatoms that produce domoic acid) and Alexandrium (roundish shaped dinoflagellates that produce saxitoxin).
Credit
Photo credit: Brian Bill NOAA Fisheries/Northwest Fisheries Science Center, Seattle, WA, 98112 USA
This work was supported by the NSF Office of Polar Programs (OPP-1823002; OPP-2135537); NOAA's Arctic Research program (through the Cooperative Institute for the North Atlantic Region [NA14OAR4320158 and NA19OAR4320074]); NOAA Centers for Coastal and Ocean Science (NCCOS) Competitive Research Program (NA20NOS4780195; the Woods Hole Center for Oceans and Human Health (National Science Foundation grant OCE-1840381 and National Institutes of Health grant NIEHS-1P01-ES028938-01).
About Woods Hole Oceanographic Institution
Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its mission is to understand the ocean and its interactions with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in fundamental and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of ocean data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge to inform people and policies for a healthier planet. Learn more at whoi.edu.
Journal
Nature
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Bowhead whale feces link increasing algal toxins in the Arctic to ocean warming
Article Publication Date
9-Jul-2025
