Why It Matters
Alaska’s marine food web — the foundation of the state’s fishing industry, Indigenous subsistence culture, and coastal economies — is facing a growing threat from toxic algal blooms spreading into waters where they were rarely, if ever, recorded before. The emergence of saxitoxin, the algal toxin responsible for paralytic shellfish poisoning, in remote Bering Sea ecosystems signals a potentially irreversible shift driven by ocean warming that could affect human health, wildlife populations, and the livelihoods of communities across Alaska.
For Alaska Native communities that depend on marine mammals and shellfish as dietary staples, the risk is not abstract. It is appearing on their own beaches, in animals their ancestors harvested for generations.
What Happened
Over the past two summers, mass die-off events on the Pribilof Islands — a remote four-island archipelago in the eastern Bering Sea, roughly 750 miles west of Anchorage — have produced the first conclusive evidence that saxitoxin is killing marine mammals in Alaska’s sub-Arctic waters.
In August 2024, tribal employees monitoring beaches on St. Paul Island discovered 10 dead northern fur seals lying among piles of dead fish and birds. The animals appeared well-fed, showing no signs of starvation or injury. Laboratory testing confirmed the seals had been killed by saxitoxin, marking the first documented case in history of marine mammals conclusively killed by the paralytic shellfish poisoning toxin.
The following summer, in August 2025, residents on St. George Island — St. Paul’s sister island — found 21 dead fur seals on a beach. The scene also included two dead fin whales, a dead sea lion, and several dead seabirds, indicating that the toxic bloom had spread across multiple species and a wider geographic area than the year before.
Aaron Lestenkof, a member of St. Paul’s Indigenous Sentinels Network, said the events caught local residents off guard. The community of approximately 400 people, most of them Unangax̂, was aware that paralytic shellfish poisoning posed dangers in Southeast Alaska, but saxitoxin killing marine mammals on their own shores had never been part of their experience. “It never occurred to us that it may happen to our marine mammals here,” Lestenkof said. “I guess it was just a matter of time.”
By the Numbers
- 10 northern fur seals found dead on St. Paul Island in August 2024 — the first confirmed saxitoxin kill of marine mammals on record.
- 21 dead fur seals discovered on St. George Island in August 2025, along with two fin whales, one sea lion, and multiple seabirds.
- ~400 residents live on St. Paul Island, the majority of whom are Unangax̂ and rely heavily on the marine environment for subsistence food.
- 750 miles west of Anchorage — the approximate distance of the Pribilof Islands from Alaska’s largest city, underscoring the remoteness of the affected communities.
- 2 consecutive summers of mass marine mortality events linked to algal toxins in the same island chain, suggesting the phenomenon is not an isolated occurrence.
Zoom Out
Paralytic shellfish poisoning from saxitoxin has long been a recognized hazard in Southeast Alaska’s warmer, more temperate coastal waters. Its appearance in the Bering Sea — historically colder and considered less hospitable to harmful algal blooms — reflects a broader national and global pattern of toxic blooms expanding their range as ocean temperatures rise.
Across the United States, harmful algal bloom events have increased in frequency, duration, and geographic spread over the past two decades, according to federal environmental assessments. Warming surface waters create more favorable conditions for the cyanobacteria and marine algae that produce these toxins, allowing blooms to establish in regions with no prior history of the phenomenon.
In Alaska specifically, sea surface temperatures in the Bering Sea have risen sharply since the late 2010s, and record-low sea ice extent has been recorded multiple times in recent years. Scientists studying Arctic and sub-Arctic ecosystems have warned that these changes are reshaping the food web from the base upward, with algal toxin expansion representing one of the more immediate public health consequences.
What’s Next
Tribal monitoring networks like the Indigenous Sentinels Network on St. Paul Island are expected to continue beach surveys and carcass testing in the summers ahead, providing data critical to understanding how far the toxin is spreading and which species are most affected.
Federal agencies, including the National Oceanic and Atmospheric Administration’s Fisheries Service, are involved in testing and documentation. Researchers are likely to expand water sampling and shellfish monitoring programs across western Alaska communities that rely on subsistence harvesting.
For Alaska’s Indigenous coastal communities, the immediate priority will be determining whether saxitoxin levels in local subsistence species — including shellfish and marine mammals — have reached thresholds that pose direct risks to human consumers. Public health guidance and harvest advisories may follow as monitoring data accumulates through the 2026 season.