California's stranded sea lions suffering from brain damage caused by algal blooms

Lisa M. Krieger, SAN JOSE MERCURY NEWS
Scientists have gleaned fresh insight into the havoc wreaked by a microscopic culprit that has disrupted marine life this year along the Pacific Coast, not only tainting Northern California’s delicious supply of Dungeness crab but also sickening or killing hundreds of sea lions. It’s long been known that a tiny toxin called domoic acid, produced by marine algae known as pseudo-nitzschia, kills brain cells. But new research by a UC Santa Cruz team illuminates the relationship between damage to the brain and sea lions’ profound loss of memory and navigational skills. In recent years, biologists have increasingly observed a high number of California sea lions struggle onto beaches, weak, confused and trembling.
“They have a lot of difficulty navigating and finding food,” said Peter Cook, who presented the findings Monday at the biannual Conference on the Biology of Marine Mammals in San Francisco. “They have no sense of which way to go.”
While harmful algal blooms are not unusual, this year’s phenomenon was the largest ever recorded, lasting through the summer and extending from Santa Barbara to Alaska. Blooms of the toxic algae typically occur in the spring and last just a few weeks.
This year’s bloom caused the unprecedented shutdown of the commercial Dungeness and rock crab fisheries throughout most of California. But the toxin has affected other marine life as well, working its way up the food chain from razor clams to anchovies and other small fish to sea lions, one of the top predators in coastal waters.
For the first time ever, sick sea lions have been documented in Oregon and Washington, not just California, said Kathi Lefebvre, of the Northwest Fisheries Science Center, part of the National Oceanic and Atmospheric Administration.
An estimated one-third of stranded sea lions suffer from domoic acid poisoning, Cook said. The research is published in this week’s issue of the journal Science.
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