AAAS: “Warming oceans are pushing harmful algal blooms into polar waters.” When I think of saltwater algal blooms, I usually contemplate warming tropical + subtropical waters. This article pushed the envelope for me, extending the reach—and danger—of these microscopic single-celled organisms up into the polar north. In July 2022, Woods Hole Oceanographic Institution (WHOI) Ph.D. student Evie Fachon was aboard the research vessel Norseman, searching for tiny but dangerous creatures lurking off the Alaskan coast. They were “sailing through dense concentrations of a dinoflagellate at the base of the food web that produces toxins that can lead to paralytic shellfish poisoning.” By the end of the cruise, they had documented “the largest toxic bloom of A. catenella ever seen in polar waters, stretching at least 600 kilometers and triggering risk advisories about potentially unsafe marine harvests.”
“The warmer it is, the faster [the cells] can potentially grow and multiply,” says Fachon, lead author of a 2024 paper describing the 2022 bloom, as they found “algal concentrations that were more than 100 times higher than the level needed to trigger public health warnings.” Fachon and colleagues suspect the 2022 bloom germinated somewhere in the Bering Sea, possibly in Russia’s Gulf of Anadyr. Their hypothesis: “As strong winds pushed nutrient-rich western Bering Sea water into warmer Alaskan waters, favorable temperature and nutrient conditions allowed the algae to expand.” Christopher Gobler, an ecologist at Stony Brook University, had previously published a 2017 study showing ocean warming has expanded the range of harmful algal blooms poleward in the North Atlantic and North Pacific oceans.
“Elsewhere in the world, bloom-related warnings have mainly focused on clams and mussels, which are known to accumulate poisonous loads of toxins—but the tribes in the Bering Strait region also rely on seabirds, seals, walruses, and whales.” In the graphic: note the Bering Strait lies between the Chukchi + Seward Peninsulas. The meandering red signal between them represents the dangerous dinoflagellate bloom. Dangerous, but also fascinating.
