The extensive events, resulting in advisories, have researchers concerned for future populations due to repeated exposure and toxin regeneration.

A toxic algal bloom off the coast of Southern California is poisoning marine animals and while this isn’t a new occurrence, the number of animals affected and focused area surprises some researchers, who are also raising awareness about a second, never-before seen toxin in the area that has dangerous implications for the future and is “not to be ignored.”

The annual culprit of much of the toxicity is domoic acid, a neurotoxin produced by the plankton pseudo-nitzschia, killing sea lions, dolphins, pelicans and more in large numbers.

Several sea lions have shown signs of the domoic acid poisoning in La Jolla; lajolla.ca observed a dead dolphin April 20 at Black’s Beach; and residents have reported dead fish dropped by birds in shoreline neighborhoods.

Domoic acid poisoning details

The algae that produces domoic acid is different from the dinoflagellate Lingulodinium polyedram, which causes bioluminescence and delights viewers from spring into summer and summer into fall.

The current wave of toxic domoic acid from pseudo-nitzschia started slowly at the end of December, according to Clarissa Anderson, a biological oceanographer and the executive director of the Southern California Coastal Ocean Observing System (SCCOOS) at UC San Diego’s Scripps Institution of Oceanography.

SCCOOS collects environmental data on a variety of issues, including for harmful algal blooms, via a network of underwater instruments equipped with microscopes called Imaging FlowCytobots. The work, largely supported by federal funding from NOAA, helps scientists identify the microscopic culprits causing these devastating blooms.

In December, Southern California moved into a La Niña phase, which brings cold water upwelling from the depths of the ocean to the surface, leading to a spike of the algae bloom in January near the Scripps pier, Anderson said.

The spike has remained consistent since February, she said, with continual animal stranding observed from Baja California, Mexico, north to Bodega Bay, California.

“It’s become a pretty extensive event,” Anderson said.

The typical pattern is to have a pseudo-nitzschia bloom annually, she said, with domoic acid poisoning ranging from nonexistent to minor.

The impacts vary from a shellfish advisory or a few seabird deaths in one stretch of the coast to some sea lions only in Santa Barbara, but “rarely all three of those things at once,” she said.

But 2016 saw an “epically large bloom,” Anderson said, “still the most unprecedented in terms of size and duration: five months [from] Santa Barbara to Alaska, thousands of animals killed across the food web.”

2022, however, marked the onset of a “weird” pattern, where every year has brought a major pseudo-nitzschia bloom, she said, usually in the summer.

This current bloom is the fourth annual, and is earlier than usual.

“Having it four years in a row is highly unusual,” Anderson said, as is having the entire food web impacted.

“We are now seeing a shellfish advisory. We’re seeing sea birds come in, dolphins, California sea lions, elephant seals and even larger whales. …

“I haven’t ever seen this,” she said. “And for it to be so focused in Southern California is also a big deal.”

Saxitoxin: a new, larger worry

On top of the domoic acid poisoning, a new toxin has emerged, Anderson said: the saxitoxin, produced by the marine dinoflagellate Alexandrium, which hasn’t been seen in Southern California. 

“The saxitoxin is not to be ignored. It’s one of the most deadly toxins we know of in plankton,” she said.

And with the advent of saxitoxin here, the local marine animals are “getting hit by two really bad neurotoxins simultaneously, which may also explain just how bad it has gotten in the last three weeks,” Anderson said.

While “grotesque and horrible,” the severity doesn’t indicate a population crisis for these animals now, she said.

Long-term vigilance 

What does concern Anderson and her peers, however, is the future effects of long-term vulnerability.

“A lot of these animals are coming in from having been repeatedly exposed for the last four years,” she said, leading to what people might interpret as aggression in sea lions, for example, but “are probably a function of getting hammered year after year with toxins and it’s changing their behavior.”

A further worry: when a high-level Alexandrium bloom ends, a cyst-like, dormant cell is created, Anderson said. 

This “cyst bed” will then regenerate a new bloom the next year.

“We’ve never really had that kind of cyst bed of this organism in Southern California before,” she said. “We could be entering a new era of these blooms [that] perpetuates for many years to come.”

If an animal suspected of poisoning is spotted, staying away is critical, Anderson said. Call SeaWorld San Diego rescue at (800) 541-7325 or send an email to swc.rescue@seaworld.com.

People should also continue to monitor California Department of Public Health advisories for food and water information.

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