Algae bloom kills hundreds of sea lions off California

Hundreds of sea lions off the coast of California have been poisoned this year amid a “highly unusual” algae bloom that has persisted in southern and central parts of the state into October.

Experts believe the blooms, which are becoming more common, may be linked to warming and changing ocean conditions. They harm sea life when algae produce a neurotoxic chemical that can be taken up by fish and crustaceans and absorbed by the larger animals that eat them.

Off the US west coast, the proliferations of algae, sometimes called “red tides”, usually peak in the late spring. For the last three years, however, harmful blooms have come on strong in the summer and, this year, lasted into autumn before mostly petering out.

That is “highly unusual,” according to Clarissa Anderson, a researcher with the Scripps Institution of Oceanography, who is also the director of the Southern California Coastal Ocean Observing System, which tracks harmful algal blooms.

“It’s catching us all off guard,” Anderson said.