Toxic bloom continues to ravage sea lions in Southern California

Eight female sea lions lay silently on the deck at the Pacific Marine Mammal Center in Laguna Beach on a recent afternoon.

“Most of them don’t survive,” said Lindsey Vanschoick, the rescue center’s animal care supervisor. 

“We try to get them interested in eating, but right now we’re just giving them fluids.”

The adult sea lions, some of them pregnant or recently pregnant, are all suspected of suffering from domoic acid, a powerful neurotoxin associated with marine algae blooms.

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It accumulates in shellfish, crabs and fish, and then infects feeding sea lions — especially hungry, pregnant ones — causing them to suffer seizures, miscarriages and death. 

Humans can also become sickened by eating infected shellfish and crab. 

The Pacific Marine Mammal Center has brought in at least 32 sick female sea lions since early April. Twenty-one of them died. 

Scientists say they haven't seen evidence of this kind of toxic bloom in years. 

A combination of ocean and weather conditions and human inputs, like storm water runoff, cause algal blooms, said David Caron, a marine biologist at the University of Southern California. But scientists are less clear what leads to toxic blooms.

“We do want to get to the point where we have enough fundamental understanding that we can even mitigate some of the things when they take place or perhaps prevent those conditions from forming,” Caron said. "But we’re not quite at that point yet.”

The California Department of Public Health routinely tests shellfish for the toxin and posts warnings on its website.