Scripps Oceanography scientist studies toxic algae bloom with plans to create prediction model

Sea lions, which can become poisoned by domoic acid, haul out on Point La Jolla.
(Ashley Mackin-Solomon)

Professor Bradley Moore wants to provide fishermen, governments and others a heads up when toxic algae may impact marine animals.


As an algae bloom off the California coast creates a neurotoxin called domoic acid that has killed hundreds of sea lions and about 60 dolphins, a scientist at UC San Diego’s Scripps Institution of Oceanography in La Jolla is studying the process so others can be better prepared for future blooms.

As part of a study funded by the National Oceanic and Atmospheric Administration, Bradley Moore, a professor of marine biology, marine chemistry and geochemistry at Scripps Oceanography, is examining how domoic acid is produced and working to create a predictive model.

According to NOAA, the rapid growth of an algae called pseudo-nitzschia causes the production of domoic acid.

William Gerwick, a fellow professor at Scripps who is not connected to Moore’s work, said harmful algae blooms occur when the right combination of ocean conditions and “a bit of randomness” cause micro-algae to accumulate, or “bloom.”

Sea lions sickened by the algae also have bitten beach-goers in Southern California recently.

June 30, 2023

“They bloom ... when the temperature goes up, nutrient availability goes up and currents create the right conditions,” Gerwick said. “Sometimes currents mix the water and cause the algae to disperse, and other times it allows them to reach high density. But there is a bit of randomness in that sometimes the conditions are perfect and they don’t bloom and other times the conditions are less than perfect and they bloom.”

Harmful algae blooms also have occurred in Southern California in 2002, 2006, 2007, 2017 and 2022, according to the Channel Islands Marine & Wildlife Institute.

Moore is looking to better understand what causes the bloom switch to be flipped.

“At this stage, which is the data collection stage, we are looking to understand how this [algae] ticks, why it makes the toxin [sometimes] and why it doesn’t, and whether we can use this information to predict what is going to happen in the future,” Moore said.

With algae blooms like this one, the domoic acid is transferred to fish, which are then eaten by sea lions.

“The toxins work their way through the food web,” Gerwick said. “There are different toxins produced by different species [of algae] that can affect neurotransmission and can cause aberrations in behavior.”

In this case, animals have been stranding themselves on land or experiencing disorientation and the inability to move, leading to their deaths.

“If you are a fisherman, knowing whether there will be a toxic algae bloom can be helpful,” Moore said. “The largest bloom on Earth [was in 2015] and it had consequences in the hundreds of millions in lost revenue for fisheries. So there are big consequences to these blooms. If a tornado is coming, I’d want to know if it is coming to my town and make informed decisions.”

If a municipality can expect sick, stranded or dead animals, it can better prepare, he said.

In early June, NOAA Fisheries reported that the Channel Islands institute fielded more than 1,000 reports of sick and dead marine mammals between June 8 and 14 that were thought to have been exposed to the algae bloom.

“Responders believe domoic acid is behind the deaths, given the neurological symptoms exhibited by the animals. They have collected tissue samples for testing to confirm,” NOAA wrote.

“We are looking to understand how this [algae] ticks, why it makes the toxin [sometimes] and why it doesn’t, and whether we can use this information to predict what is going to happen in the future.”

— Bradley Moore, Scripps Institution of Oceanography

The effort Moore is part of, in concert with other scientists up the coast, is using technology to understand how the toxin is made and then testing their findings in the ocean.

“We know the genes and enzymes that make this toxin, but we need to understand the physiology … and connect that to the environment,” Moore said.

In lab studies, scientists have learned that when nutrient-rich water from the bottom of the ocean rises through upwelling, it can stimulate algae production and that ocean acidification can contribute to domoic acid production.

“We’re still at the stage of understanding in a lab how these genes are turned on and matching that in the ocean,” he said. “That understanding gives us a little bit of a window that we can use to get information out there, so that is what we are hoping to see. There is no easy way to mitigate [algae blooms] when they happen, but we can have information to better prepare. No one likes to be surprised when there are such huge consequences.”

Going forward, when environmental conditions are conducive to the production of algae, or diatoms, that create domoic acid, scientists will put autonomous rovers in the water to test for the diatoms and then for the neurotoxin to see if their prediction models are correct.

“This is a multi-year program we are making great progress on,” Moore said.

Dr. Alissa Deming of the Pacific Marine Mammal Center in Laguna Beach told the Los Angeles Times that in addition to causing animal deaths, domoic acid may cause sickened sea lions to experience seizures, disorientation and hyper-reactivity and may bite as a result.

Sea lions sickened by the algae bit and injured at least two people recently at beaches in Orange County, and the Channel Islands institute, which serves Santa Barbara and Ventura counties, recorded five recent incidents of animals biting beach-goers both in the water and on the beach.

Marine mammals aren’t the only ones affected. Because the neurotoxin can reach fish that are eaten as part of the food chain, seabirds also can be intoxicated.

Moore and Gerwick said some in the scientific community believe Alfred Hitchcock’s 1963 horror film “The Birds” was inspired by a 1961 incident in which birds in central California were exposed to domoic acid during an algae bloom and experienced the kind of neurological effects now impacting California sea lions. ◆