Algal toxins detected in Alaska marine mammal species

Researchers with the National Oceanographic and Atmospheric Administration have released a report documenting for the first time detectable levels of harmful algal toxins in marine mammals from all Alaskan regions, ranging from southeast Alaska to the Arctic Ocean. According to a NOAA press release “toxins from harmful algae are present in Alaskan marine food webs in high enough concentrations to be detected in marine mammals such as whales, walruses, sea lions, seals, porpoises and sea otters.” Dr. Kathi Lefebvre, with NOAA Fisheries and founder of the Wildlife Algal-toxin Research and Response Network for the West Coast, WARRN-West for short, led the study. She said that she examined samples from 905 animals either harvested or stranded from 2004 through 2013. In an interview with the Nome Nugget, Lefebvre said that the data shows the detectable presence of harmful algal toxins – both domoic acid or saxitoxin -  in all 13 Alaska marine mammal species tested. However, at this point, she said the levels are low. “What really surprised us was finding these toxins so widespread in Alaska, far north of where they have been previously documented in marine mammals,” said Lefebvre. “However, we do not know whether the toxin concentrations found in marine mammals in Alaska were high enough to cause health impacts to those animals. It’s difficult to confirm the cause of death of stranded animals. But we do know that warming trends are likely to expand blooms, making it more likely that marine mammals could be affected in the future.” Bowhead whales harvested in Barrow, as well as humpback whales, belugas, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses and northern sea otters showed detectable levels of algal toxins. A stranded minke whale found near Cape Nome last summer also tested positive for domoic acid. Lefebvre said that out of the 886 marine mammal samples that she analyzed for domoic acid, 188, or 21 percent, tested positive. She analyzed 25 bowhead samples and 17, or 68 percent, tested positive for domoic acid. These toxins are not a new occurrence and have been widely documented in sea lions in California. Domoic acid is a neurotoxin produced by single-celled algae. Certain types of algae called Psuedo-nitzschia produce the toxin that can cause severe seizures and even death to those animals that feed on them. The blooms of these algae occur when the water conditions are favorable for algal growth like warm water and appropriate light and nutrient levels. Algae blooms have in the past triggered the closures of shellfish fisheries in Washington, Oregon and California. Sea lions in California that had fed on fish, which in turn had ingested the algal toxins contorted their bodies in seizures. Many sea lions each year are affected by domoic acid poisoning in Central California. Crab fisheries were closed in Oregon due to domoic acid last year. Another toxin produced by warmer water algae is called saxitoxin and is known to cause paralytic shellfish poisoning, or PSP. Most of the marine mammals that Lefebvre examined are subsistence species and as such a food security concern arises. Lefebvre explained that the toxins are mostly found in stomach contents and the feces, not in the muscle or meat of the animals tested. Gay Sheffield with the UAF Marine Advisory Program in Nome and coauthor of the study warned that clams found in the stomachs of harvested walruses and bearded seals are often eaten in several coastal communities throughout western and northern Alaska and may contain algal toxins. “Commonly eaten animal parts like muscle and blubber are not likely to accumulate these toxins in levels of concern for human consumption, and there is no change in the current guidance from the Alaska Department of Health regarding seafood safety,” said the NOAA press release. Dr. Louisa Castrodale, State Veterinarian with the Alaska Dept. of Health’s section of Epidemiology said that the levels found by the study were below levels that would warrant any action. Consuming shellfish either directly gathered from the beach or out of a walrus stomach, she said, carries always the inherent risk of ingesting algal toxins. Since subsistence users cannot cook the toxins out of the shellfish, caution is advised. Castrodale called the study’s findings “remarkable.” The report titled “The prevalence of algal toxins in Alaskan marine mammals foraging in a changing Arctic and subarctic environment” was published in the journal “Harmful Algae” on Wednesday. Since 1998, algal toxin poisoning has been a common occurrence in California sea lions, but this report is the first documentation of algal toxins in northern ranging marine mammals. Lefebvre has been studying harmful algal toxins for more than 17 years. In 1998, hundreds of sea lions had seizures or washed up dead on central Californian shores and Lefebvre, then a first year grad student at the University of California Santa Cruz, helped discover that the sea lions died as a result of the consumption of anchovies that fed on toxic algae. Lefebvre said algae blooms are still not very well understood as sometimes they produce more toxins than at other times. She also said the report suggests that warming waters and the decrease of sea ice, which allows more sunlight that spurs algal blooms, contributes to the northward spread of algal toxins in marine mammals. She said she plans to continue sampling now that she has established baseline data. Further sampling and results could be linked to environmental changes as the warming trend continues. Also, it is unknown what the long-term effects of low-level exposure to algal toxins are. Lefebvre said she is researching this question with mouse experiments in the laboratory, but has so far no findings to report. In sea lions, she said, it is known that survivors of a meal filled with algal toxins suffer from spatial disorientation and memory loss, meaning that they cannot migrate as well or feed efficiently. The study is published online at

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