Scientists have found dozens of poisoned dolphins, whales and sea lions off the coast of Washington, Oregon and California this year. They tested positive for a toxin caused by a massive algae bloom this summer in the Pacific Ocean.
Toxic domoic acid is produced by algae in the ocean, and this year the algae are thriving in the largest bloom ever recorded here. Marine mammals are poisoned when they eat fish that are contaminated.
"When eating fish that accumulate the toxins from the blooms, it's basically like getting food poisoning," says Kathi Lefebvre of the Northwest Fisheries Science Center.
Poisoned marine mammals and birds began showing up on the Central California Coast 17 years ago. Sea lions were discovered having seizures, a common response to domoic acid poisoning. Animals have shown signs of the toxin since, but largely in California.
But then this May, scientists found a sea lion suffering from a toxin-induced seizure at Long Beach, Washington – the first time this level of poisoning has been documented in the Northwest.
Lefebvre says the algae blooms are associated with warmer water.
“And that’s why I think it’s scary. Are we going to go into a new trend that hasn’t been in the past? And now we’re going to see more contamination of the food web even farther north and affecting more marine mammals,” she said.
Mammals can survive domoic acid exposure, but can be left with chronic health problems if they do. Lefebvre says there's not much that can be done to prevent the animals from being poisoned.
High levels of the toxin prompted shellfish fishery closures in Oregon and Washington this year.