Over the first several months of this year, hundreds of sea lions, dolphins, and seabirds have fallen ill or died after eating sardines or anchovies that had been feeding on an algal bloom along the California coast since winter. The biotoxin in the algae accumulates in the feeder fish.
Two cases of whales dying from the biotoxin have been confirmed by two nonprofit organizations tasked with testing dead mammals. These were a humpback that washed ashore in Huntington Beach in January and a minke whale found dead in Long Beach in April.
This is the fourth year a row that California has experienced major algal blooms. Warmer waters are causing blooms to be bigger and more damaging than they have been before. They enter into new areas and contaminate the food web for longer. The warmer waters accelerate algae growth that is further fueled by nutrients that rise to the surface from deeper colder waters driven by winds that blow parallel to the coast. This year’s algae event started earlier than usual and is lasting longer than normal.
More than a dozen animal rescue and rehabilitation groups that form NOAA’s West Coast Marine Mammal Stranding Network are providing resources to try to respond to the situation. At the Marine Mammal Care Center in Los Angeles, more than 80 sea lions and seals were being treated for domoic acid poisoning, the result of ingesting algae neurotoxin. Since February, it has cared for more than 300 poisoned animals.
Marine mammals are sentinel species for humans who also consume seafood. The West Coast ocean ecosystem is currently filled with toxins.
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California Toxic Algal Bloom Blamed for Months-long Marine Life Poisoning
Photo, posted March 26, 2025, courtesy of Marnee Jill via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio
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