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Uncovering a “sleeping giant” Arctic cyst bed

Don Anderson gave a virtual presentation at the University of Alaska Fairbanks on 10/13/21 focusing on the potential for a significant increase in Alexandrium catenella harmful algal blooms due to warming Arctic waters. During annual blooms, the cells produce saxitoxins, potent neurotoxins, which accumulate in the food web and can lead to paralytic shellfish poisoning (PSP), a potentially fatal human poisoning syndrome. Recent data shows that most forage and predatory fish in Southeast Alaska have trace or low levels of saxitoxin that are not considered harmful, and levels of toxin measured thus far in Arctic fish have also been low. However, saxitoxins in shellfish consumed by walruses and other marine animals raise concerns for food security for Native Alaskan communities that rely on wild harvests.

Data from 2018 and 2019 Arctic research cruises showed extensive beds of Alexandrium cysts, a dormant stage of the algae, in seafloor sediments north of the Bering Strait, in the Chukchi Sea, and in the western Beaufort Sea near Pt. Barrow. In the Chukchi sea, cyst counts show a massive and persistent cyst distribution extending at least 200 km offshore and up to 600 km alongshore. This Alexandrium catenella cyst seedbed was found to have 17,000 cysts per cubic centimeter, among the highest ever reported for this species globally. Describing this as a “sleeping giant” Arctic cyst bed, Anderson explained that Alexandrium cysts in bottom sediments can survive from decades to a century, so this would “represent a significant and dangerous site for in situ bloom inoculation as waters warm.”  In addition, warming Arctic waters support earlier and faster germination of cysts as well as longer periods during which blooms can occur. In his concluding remarks, Anderson emphasized: “Everything described here speaks to the potential for significant and increasing HAB impacts on human and ecosystem health in the Alaskan Arctic. Recognize that many regions of the world face similar risks, and yet are able to maintain healthy communities and ecosystems.”

Satellite image of Bering Sea algal bloom. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Here is a link to a recording of the “Strait Science” lecture presentation, which was sponsored by the UAF Northwest campus and UAF Alaska Sea Grant: