Over the past few weeks, Santa Barbara County’s typically serene shoreline has transformed into a scene of gruesome marine mammal suffering due to a widespread toxic algal bloom sweeping the coastal waters of Southern California.

The algae is Pseudo-nitzschia and it produces domoic acid, a compound that is neurotoxic to mammalian systems. Since late March, beachgoers have encountered hundreds of washed-up animals suffering from domoic acid poisoning with symptoms that include seizures, erratic and dangerous behavior and comas.

Alyson Santoro is an oceanographer and marine microbiologist, as well as a professor in the Department of Ecology, Evolution, and Marine Biology. She heads UC Santa Barbara’s Santoro Lab, which concentrates on the study of microbiology in the deep ocean and oversees the Southern California Coastal Ocean Observing System’s (SCCOOS) Santa Barbara shoreline monitoring station for Harmful Algal Blooms (HABs).

Santoro described how domoic acid infiltrates marine mammals’ organs through a process called bioaccumulation in the food chain. The process begins when small marine species called zooplankton consume the algae, causing domoic acid to accumulate in their tissues. Then, small fish, such as anchovies and sardines, eat the zooplankton, further concentrating the toxin. Next, larger fish eat the smaller fish, compounding the concentration even further. Although domoic acid is relatively innocuous to the phytoplankton and the animals on the lower rungs of the food chain, it wreaks havoc on the function of neural and extra-neural tissues in mammals.

“When a marine mammal like a dolphin or a sea lion eats those bigger fish, by that point, it becomes very, very concentrated and starts to have really horrible neurotoxic effects,” Santoro explained.

Since domoic acid has a similar biochemical structure to the neurotransmitter L-glutamate, once inside the mammal it is able to mimic the molecule and bind to glutamate receptors (GluRs). Domoic acid can have up to a 100 times greater potency than L-glutamate, eliciting an over-excitatory effect due to unregulated stimulation of the ionotropic GluRs, or fast-acting, gated cation channels called iGluRs. The excessive opening of the iGluRs can cause calcium ions to flood the cell, leading to cell damage or death. 

Exposure to domoic acid is particularly harmful to the brain and can induce severe neurobehavioral deficits, according to Samuel Dover who is the co-founder (alongside his wife Ruth Dover) and director of Veterinary Medicine, Research and Conservation for the Channel Islands Marine & Wildlife Institute (CIMWI).

“The ultimate thing it does cause is atrophy of the hypothalamus which controls the part of the brain involved with location,” Dover said. “These animals lose their mental map. They know where to go when it’s breeding season; they know where to go when it’s feeding season … This affects their ability to navigate in their environment.”

A typical rescue for CIMWI begins with a call to its hotline. After receiving the report, they’ll send a volunteer to the site to evaluate the animal. If it seems like the animal is suffering from domoic acid poisoning, they’ll establish a boundary around them with signs explaining to the public what is occurring and instructing them to give the animal space.

“We’ll recheck [the animal] later in the day; if it’s clear it needs rescuing we’ll rescue it, if it’s questionable we’ll wait. With DA [domoic acid], because we know sometimes they’ll snap out of it and sometimes they won’t, we’ll give them a chance,” Dover said.

Once the CIMWI volunteers determine that the animal is in need of rescue, they’ll bring it to their hospital in Gaviota, where they undergo the rehabilitation process. This includes administering anti-seizure medication and anti-inflammatory medications, flushing the animal’s body of the toxin with fluids and feeding them domoic acid-free fish. It’s possible that the animal may die throughout any part of the rescue and rehabilitation process; if the poisoning is deemed too severe for the animal to survive in the wild, it may be humanely euthanized. As the animal progresses through treatment, however, CIMWI volunteers reevaluate for potential release. 

Courtesy of Channel Islands Marine & Wildlife Institute

Even if the animal is released, they may still suffer from lasting brain damage. Additionally, Dover explained that the severity of poisoning and the possibility of recovery depend on how large of a dose of domoic acid the animal has ingested. This makes defining a clear measure of success challenging for the marine mammal stranding community. 

“Sometimes the success rate is pretty good, sometimes it’s not … You’ll see different reports on success rates and this year is really bad,” he said. “With repeated events — like I said three or four in the last year — these animals are being affected significantly more.”

Algae blooms in the coastal zone are not uncommon; in fact, they’re pretty much an annual springtime occurrence in Santa Barbara.

“You might associate spring quarter with a lot of wind,” Santoro said. “The wind along the coast has the effect of pushing the surface layer of water offshore, allowing deep water to come to the surface. Deep water has a lot of nutrients in it and the nutrients brought up by this upwelling are what feed the phytoplankton.”

Not all algae blooms are toxic, but events like these are becoming increasingly frequent. According to Dover, prior to this decade, scientists expected a HAB event to occur every four to seven years. One has occurred every year for the last four years, and three have occurred in the last 12 months alone. As Dover puts it, “we’re in a new cycle of the oceans.”

As for why blooms like this have been particularly devastating, Santoro said that “it’s still too early to tell.”

She discussed multiple hypotheses circulating in the marine science community, including a potential correlation with the Los Angeles wildfires that occurred in January.

“There is the direct impact on the ocean of the ash from the fires which introduces nutrients, and that can be really hard to measure and determine,” she said.

According to Santoro, algae require two essential nutrients to flourish: nitrogen and phosphorus, both of which are naturally brought to the surface due to upwelling. A 2023 study by UCSB graduate students found that the large plume of ash that loomed over the Santa Barbara Channel in the aftermath of the 2017 Thomas Fire supplied significant nitrogen to fuel marine algal growth.

In the case of the Los Angeles fires, Santoro said that most scientists are looking to the phosphorus-rich chemical fire retardant, Phos-Chek, which was used to extinguish the flames and was subsequently swept out to sea as storm runoff. Santoro, however, is skeptical of this theory due to the extent of the bloom, which stretches from San Diego to Monterey Bay. Additionally, she noted that the coastal ocean is typically limited in nitrogen as opposed to phosphorus.

Another force could be at play here, as well: climate change. 

“Because we have these really long-term data sets monitoring these algae, people have tried to go back in time to look and see what was going on in the ocean in the years with more harmful algae bloom events,” Santoro said. “When El Niño, or another really big climate index called the Pacific Decadal Oscillation, or PDO, are in their warm phases, algal blooms tend to be more frequent. That’s one strong piece of evidence that warming water can be leading to increased blooms. But it’s not a simple, straight-forward relationship.”

Most likely, algal blooms are the result of multiple compounding factors which can be difficult to study on the oceanic scale — particularly due to the anthropogenic, or human-caused, pressures impacting these systems.

“When you do a science experiment, you need to have a control where you don’t change anything,” Santoro said. “But we don’t have a control for the ocean, and we’re changing lots of things at once. We’re changing the temperature, we’re changing the pH, we’re changing the oxygen concentration, we’re starting to change circulation patterns because of the way heat is distributed in the ocean.”

Therein lies the importance of long-term ecological monitoring, which involves regularly and repeatedly collecting data in a specific location over multiple years to determine how a site has changed over time.

“Imagine if we didn’t have ocean monitoring and we just had lots of sea lions and dolphins washing up and we had no idea what was going on,” Santoro said. “But because we have these monitoring programs, even though we might not be able to prevent it, we at least have an idea of what’s going on and the more data we have, the more we can start to figure out why this is happening.”

“These kinds of monitoring programs are the things that are always on the chopping block when it comes time for funding because just going out once a week to take a sample is a lot of work and it’s not always clear what the outcome will be,” Santoro added.

By and large, programs like SCCOOS are supported by the National Oceanic and Atmospheric Association (NOAA), which has recently been the subject of large cuts to federal funding by the Trump Administration.

“That’s really hard to see while this is happening,” Santoro said. 

Additionally, CIMWI also operates within NOAA through its Marine Mammal Health and Stranding Response Program. Dover echoes Santoro’s sentiment.

“We’re at the point of saying, ‘Okay, what’s next?’ The problems are only getting bigger, the funding is only getting smaller. We started this 20 years ago, things are not good right now,” Dover said.

Those interested in contributing to CIMWI’s mission can do so by volunteering or making a financial donation. If you encounter a marine mammal that may be suffering from domoic acid poisoning, call the CIMWI hotline at (805) 567-1505.

A version of this article appeared on p.13 of the Apr. 24, 2025 edition of the Daily Nexus.