Detection of Massive Harmful Algal Bloom in the Arctic Prompts Real-Time Advisories

In the summer of 2022, a research cruise detected a massive harmful algal bloom (HAB) in the Bering Strait region of western Alaska. This expedition provided a dramatic example of science utilizing new technology to track a neurotoxic HAB and effectively communicate information that protects remote coastal communities in real time.

The large spatial scale, high cell density, long duration, and potent toxicity of the 2022 HAB event “posed an unprecedented risk to human and ecosystem health as well as maritime subsistence harvest activities in the Bering Strait region and beyond,” according to the journal article “Tracking a large-scale and highly toxic Arctic algal bloom: rapid detection and risk communication,” published in Limnology and Oceanography Letters.

Researchers from the Woods Hole Oceanographic Institution (WHOI) and its partners noted that, to their knowledge, the 2022 event was the largest HAB event documented in polar waters to be caused by the single-celled organism Alexandrium catenella, which produces neurotoxins called paralytic shellfish toxins (PSTs). Toxins produced by this organism as it proliferates or “blooms” can accumulate in organisms that consume the algae, and the toxins can then be transferred through the food web, causing illness or mortality of marine animals and potentially fatal Paralytic Shellfish Poisoning (PSP) in people who eat contaminated seafood.

The bloom of Alexandrium stretched at least 600 kilometers (~370 miles) from the northern Bering Sea to the southern Chukchi Sea at its peak. While concentrations of A. catenella in excess of 1,000 cells per liter are considered dangerous, the measured maximum concentrations in this bloom exceeded 174,000 cells per liter—a record breaker for Arctic waters. In addition, the high toxicity of the Alexandrium cells compounded the poisoning risk from the bloom, according to the researchers.