Research examines toxins in arctic food webs and marine mammals

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Walrus in the northern Bering Sea. Photo credit: Liz Labunski, courtesy of the US Fish and Wildlife Service.

A new bulletin published by Alaska Sea Grant summarizes the research to inform and help the public understand the risk of paralytic shellfish toxins in the food webs and marine mammals of Arctic Alaska.

Paralytic shellfish toxins — also called saxitoxins — are produced by microscopic seaweed and can cause paralytic shellfish poisoning (PSP) when humans consume shellfish or marine mammals that eat shellfish. Ocean warming trends have increased the risk of toxic algal blooms and PSP for marine life and coastal communities in western and northern Alaska.

During the unusually warm summer of 2019, scientists measured toxin concentrations of paralytic shellfish in different layers of the food web, examining phytoplankton, zooplankton, benthic mussels, benthic worms and pelagic fish. They also examined samples of walrus and bowhead whales caught for subsistence in the Bering, Chukchi and Beaufort Seas.

The results of the study include:

  • Mussels had higher levels of toxins than other layers of the food web, and some mussels collected in the Beaufort, Chukchi, and Bering Seas contained toxin levels above the legal limits for commercial seafood safety.
  • Walruses feed on bivalves and have higher doses of toxins than bowhead whales, which feed on zooplankton.
  • Estimated daily toxin doses for walruses in the summer of 2019 were in the range of doses known to have health effects on other mammals. More studies are underway to determine if walruses have any health effects.
  • Marine mammal muscle and blubber are unlikely to accumulate saxitoxin at levels that pose a hazard to human health. However, ongoing studies are being conducted to determine if other walrus tissues or organs can accumulate saxitoxins.

The Bulletin Saxitoxin in the food webs of western and northern Alaska + estimated doses for walruses and bowhead whales in warm sea conditions in 2019 is available now as a free download from the Alaska Sea Grant bookstore.

Gay Sheffield, Alaska Sea Grant Marine Advisory Program agent for the Bering Strait region, contributed to the bulletin. This work is part of a larger, multi-year effort (Trophic transmission and effects of HAB toxins in Alaskan marine food webs) lead by dr Kathi A. Lefebvre of the NOAA Northwest Fisheries Science Center. Other cooperation partners are the Woods Hole Oceanographic Institute, the North Slope Borough Department of Wildlife Management and the US Fish and Wildlife Service. Funded by the National Centers for Coastal Ocean Science’s Ecology and Oceanography of Harmful Algal Bloom program, the project aims to better understand harmful algal blooms in Alaskan waters and the potential risks to human health.

Learn more about the project in these journal publications:

Paralytic shellfish toxins in the Alaskan Arctic food webs during the unusually warm sea conditions of 2019 and estimated toxin doses for Pacific walruses and bowhead whales (Harmful algae)

Harmful algal blooms in Arctic Alaska: An emerging threat as the ocean warms (oceanography)

Source: Alaska Sea Grant

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