Environmental Hazards, Nature

California Sea Lions Dying Due to Poisonous Algae Blooms

California sea lions are being killed by toxic algae blooms.
California sea lions are being killed by toxic algae blooms.

In the first two weeks of April, the Pacific Marine Mammal Center in Laguna Beach, California, recorded 14 sea lion deaths due to poisoning by domoic acid. Another nine are in various stages of recovery.

Domoic acid poisoning occurs when animals eat fish that have been feeding on toxic algae.

Marine Mammal Center spokeswoman Krysta Higuchi told the Los Angeles Times that 10 years ago, the last time the problem was this severe in southern California, 79 sea lions died due to domoic acid poisoning.

“Other rescue facilities are also seeing the same animals,” Higuchi said. They’re “all over the place.”

How does domoic acid poisoning happen? Normally, blooms of single-celled algae occur for about a week in the spring. However, the heavy rains California has been receiving have intensified the blooms by flushing nutrients from fertilizers and other sources into the Pacific Ocean, and this has intensified the blooms. Small sea animals like anchovies, clams, and mussels feed on the algae, and the sea lions then feed on those animals.

“When the sea lions eat these toxic anchovies, they have serious neurological problems,” said Kathi Lefebvre of the National Oceanic and Atmospheric Administration Fisheries in Seattle. “The sea lions will have seizures, in some cases they’ll die, in some cases they’ll recover but have permanent brain damage.” In addition, many pregnant sea lions miscarry. The pups that do survive until birth often suffer from the effects of domoic acid poisoning.

The Marine Mammal Center in the northern California city of Sausalito has also treated two sea lions it suspects were poisoned by domoic acid.

Dr. Shawn Johnson, director of veterinary science at the Sausalito center, said that it’s possible more sea lions in northern California may be affected as the water temperatures rise in the summer and fall.

“There’s still a lot of unknowns about what triggers these blooms of algae and what triggers them to become toxic, because not all the blooms are toxic,” Johnson told SFgate. “There’s a lot of research going on to better understand [the causes] so we can better predict when these blooms will happen so that fisheries can be monitored, and for us, so we can be prepared for increased stranding [of sea lions].

California officials have warned consumers not to eat mussels, clams, or whole scallops harvested recreationally in Santa Barbara County. Commercially harvested seafood is typically tested for safety before being distributed.

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