This article was originally published by LAist on May 28, 2025.
The severe toxic algae bloom that sickened or killed hundreds of marine animals in Los Angeles County — including sea lions and dolphins — appears to be subsiding.
That’s according to the Marine Mammal Care Center in San Pedro, which is reporting that there have been no new patients over the past week or so showing signs of domoic acid toxicosis. The acid occurs naturally in some types of algae and is a dangerous neurotoxin that can make animals very sick and sometimes more aggressive.
David Bader, a marine biologist with the center, told LAist they’ve seen more than 250 dolphin strandings and have rescued over 400 animals to date. That’s compared with the 300 rescues they budget for in a typical year.
In a post on Instagram, the center said that this months-long event was “the longest, most toxic, and deadliest bloom” it’s ever experienced.
“While we see the light at the end of the tunnel and we’re happy that this particular bloom is over, it’s not time to relax,” Bader said.
While toxic algae blooms of this type typically happen every four to seven years, Bader said we’re on the fourth consecutive year of the harmful phenomenon.
The root causes
Experts say climate change is causing our oceans to become more acidic as they absorb more carbon dioxide from the atmosphere.
Research has shown that many algae may thrive under more acidic conditions. And some of those algae, like Pseudo-nitzschia, produce the toxic domoic acid.
“We’re seeing these types of events happening year after year after year. And they’re increasing in their intensity and their frequency,” Bader said.
There needs to be a concerted effort toward changes that make events like these less deadly in the future, Bader added.
“That means everybody really taking climate change seriously, doing the things we need to do to mitigate against it,” he said.