The Southern California coast could be experiencing one of the worst toxic algae blooms in history.
So far, the natural phenomenon has killed hundreds of sea lions, dolphins, pelicans and at least two whales since February.
Now, marine life experts say these blooms are becoming more common and more deadly.
The toxic algae forms when there’s low water circulation during warmer months. The algae produces a neurological toxin known as domoic acid that can accumulate in small fish, which are eaten by marine life, poisoning them.
John Warner is the CEO of the Marine Mammal Care Center Los Angeles and he tells KCRW the toxin affects animals’ brains.
“They have seizures in pretty severe form. The foaming at the mouth that people see is from the seizures,” Warner explains. “This year in particular, they’re showing up on our beaches, just extremely sick, and more sick than we’ve seen in the past. Quite comatose for the sea lions and for the dolphins, it’s a 100% mortality event.”
Read: Toxic algal bloom is making SoCal sea lions sick and aggressive
Typically, these blooms only occur every four to seven years. Yet, Southern California has seen these events the last four years straight. Until now, 2023 was one of the largest-ever recorded domoic acid blooms.
A few factors are making this toxic algae bloom uniquely horrible, Warner says: “We’re seeing more sea lions stranded than ever before, with much higher mortality rates even when they’re brought into care quickly,” he says. “The dolphins are stranding up and down the coast in very high numbers.”
“Lifeguards and the public are watching these animals just suffer and slowly die,” he continues. “So, it just creates this uniquely sad, uniquely traumatic experience.”
The Marine Mammal Care Center Los Angeles says sea lions are not responding as well to treatments during this year’s severe toxic algal bloom. Photo courtesy of the Marine Mammal Care Center Los Angeles.
Warner says thousands of marine birds, sea lions, and dolphins have likely died from this algal bloom, but it’s difficult to determine an exact count.
“That’s always the scary thing to think about in terms of overall populations and what their conservation looks like in a rapidly-changing environment,” he says.
Human exposure to, or poisoning from, domoic acid is possible, Warner says. However, fatalities are rare.
“It’s uncommon only because the warning systems are out there, and it’s a very well-monitored food chain,” Warner notes. Part of that warning system are sea lions, he claims, which are sentinel animals – or species that can detect risks to humans.
“When sea lions start getting sick, that is a proof point that the algae we might be recording in the water is actually starting to show up in the food chain,” Warner says. “That activates a whole host of protections for human food consumption. So we should be thanking sea lions for saving us.”
This year’s algae bloom, he says, is also lasting longer than typical events. Usually, the event fades after three to eight weeks.
“This is week 11,” Warner says. “The epicenter was here in Los Angeles County, which is why we are experiencing so many stranded animals.”
With no end in sight to this event, he says the long-term impacts are still unclear.
“Part of the problem with the environmental changes happening as fast as they are, is they’re outpacing our ability to predict them,” Warner says. “That causes a lot of issues for marine life, animal populations and our ability to be ready for it, especially if we want to respond in a humane way.”
Warner says more research is needed around these toxic blooms to determine why they’re becoming more severe.
“We need to study why this is happening, what contribution the fires and runoff might have, and even our own wastewater,” he says.
“There are many things we could do now in addressing climate change, our ocean temperatures and acidification,” Warner continues. “They’re all things that are solvable, or at least preventable from getting worse. It’s really just about having the will to tackle it and that takes all of us standing up and being very vocal about this being a priority.”