Domoic acid, the neurotoxin produced by algae blooms along the West Coast, is wreaking havoc for humans and animals alike. It might also be another indicator of climate change impact.
In the summer of 1961, deranged seabirds threw themselves into homes and windows across Monterey Bay, California. The phenomenon was so unusual and unexplainable that it inspired Alfred Hitchcock’s 1963 film, The Birds.
Half a century later, the mystery was solved in 2012. Researchers from Louisiana State University studied the stomachs of turtles and seabirds in 1961 Monterey Bay ship surveys. They found evidence of toxin-producing algae, the nerve-damaging acid that would’ve caused the bizarre reactions from the birds.
It’s very likely that toxic algae were Pseudo-nitzschia (seu-do neat-ze-uh), toxic plankton that commonly bloom along the California coastline and produce the neurotoxin domoic acid (DA). That acid is linked to a host of powerful and sometimes fatal symptoms in humans and animals, including disorientation, seizures, memory loss or death.
A recent study published out of the Dornsife College of Letters, Arts and Sciences at the University of Southern California, found that the Los Angeles coastline has some of the most toxic – if not the most toxic – Pseudo-nitzschia algal blooms on the planet.
Analyzing patterns reported over course of a decade and a half, Smith and her team named domoic acid as the smoking gun between unusually high algae blooms and mass marine mammal mortality events, such as brown pelicans in 1997 and sea lions in 1998 and 2017.
Smith’s research also touched upon the massive algae bloom of 2015, where unusually warm warm water caused the toxic plankton to bloom from Santa Barbara to Alaska. It isn’t unusual to have Pseudo-nitzschia along the Southern California coastline but the fact that warm water allowed the algae to bloom in Alaska was alarming.
That warm water was an anomaly and didn’t repeat itself the next year, but it provides proof that warming waters aid in the spreading of the toxic algae.
The Environmental Protection Agency analyzed data from the National Oceanic and Atmospheric Administration. They found that since 1901, sea surface temperature has risen an average rate of 0.13 degrees Fahrenheit, and has been consistently higher during the past three decades than at any other time since reliable observations began in 1880.
You are what you eat
Through the natural cycle – A eats B, gets eaten by C, which gets eaten by D and so on – the neurotoxin gets into the bodies of marine wildlife and humans. In humans, domoic acid causes a syndrome known as Amnesic Shellfish Poisoning, which results in nausea and vomiting.
“Domoic acid was used to deworm Japanese kids in the ‘50s,” said Jayme Smith, the lead author of the study and a postdoctoral fellow in the Department of Biological Sciences at the University of Southern California. “Before they realized how bad it was.”
Severe intoxication can turn fatal. In 1987, three people on Prince Edward Island, Canada, died of domoic acid-poisoned blue mussels. After those fatalities, the Department of Public Health set a threshold. The limit for protecting human health against overexposure was 20 parts per million of domoic acid per gram of seafood, according to Kathi Lefebvre, a toxicologist and co-author of a research study that examined algae toxin levels in Alaskan marine mammals. To circumvent hard math, she equated it to 15 razor clams a month.
Domoic acid mimics a neurotransmitter in the brain that causes nerves to over-fire. Essentially, the overexcitement causes the nerves to send along information faster and more frequently than they’re supposed to, causing a short-circuit.
“When you want to do something, your nerves will release tightly controlled glutamate into the synaptic cleft, excite the next nerve and send the signal along,” said Lefebvre. “If you have DA exposure, it binds harder and longer to the receptors, so it overexcites the nerves.”
That overstimulates and burns nerve receptors, which are particularly focused in the hippocampus, causing seizures and short- and long-term memory loss.
It isn’t easy being green
Fatalities are more common in marine animals, who can’t test their food like humans. According to Lefebvre’s research, 40 percent of United States marine mammal fatalities over the last two decades “have been attributed to algal toxin exposure.” DA overexposure also affected these animals’ navigation skills and spatial awareness.
In 1998, 81 sea lion deaths were attributed to DA overexposure. Lesser rates of intoxication led to seizures and premature births or abortions for pregnant females. And while sea lions often bear the brunt of intoxication, Smith’s research noted several other marine species – Pacific harbor seals, northern fur seals, southern sea otters, and brown pelicans – are also affected.
In Alaskan waters, Bowhead whales had the greatest prevalence of DA, a near-tie with harbor seals. Other affected animals are humpback and beluga whales, northern sea otters and bearded seals.
“The animal basically looks intoxicated,” said Wendy Leeds, an animal care coordinator at Pacific Marine Mammal Center. She likened their overexaggerated, oversensitive moves to a drunk person. Leeds also noted that while she hadn’t noticed the frequency of blooms increased, “When we have it, the blooms seem to be bigger and affecting more animals.”
PMMC, along with other centers dotting the Southern California coast, respond to reports from lifeguards and passersby of intoxicated animals. They rehabilitate them as much as possible with the potential for release. In 2017, Leeds noted, PMMC took in 70 intoxicated sea lions, including premature pups. Only 11 recovered enough to be released. The other 59 had to be euthanized. Recovery from DA overexposure is rare because beyond rehydration and rest, there isn’t any medical way of treating intoxicated animals.
If you can’t handle the heat
These toxic algae are not new for Southern California. The shape of the coastline from Point Conception to San Diego, warming springtime waters and coastal upwelling provide a perfect place for algae to bloom. But if global warming continues, more oceans would warm and increase the conditions for Pseudo-nitzschia.
“As we get these unprecedented toxic blooms, the food web and seafood products will become more affected, and in new areas where we’re not expecting it,” said Lefebvre.
Ironically, global warming could actually reduce California’s toxic algae problem. Smith defined the “window of opportunity” for Pseudo-nitzchia between 55 and 66 degrees Fahrenheit. The upper four degrees of that window produce a last-ditch mega-effort of algae production before the water becomes too warm. Above 66 degrees, the algae can no longer bloom. Of course, the research cautioned, that would leave room for warm-adapted plankton to enter.
But for Alaska, warming waters means a more hospitable environment for Pseudo-nitzchia. Lefebvre’s study noted that ocean temperatures around Alaska are rising, with the shelf waters of the eastern Bering Sea having increased by almost seven degrees Fahrenheit over the past decade.
Compared to Southern California, with multiple marine mammal centers, wary lifeguards and well-intentioned passersby, Alaska simply doesn’t have the manpower to look out for affected mammals.
“Alaska has an incredibly remote large expansive coastline,” said Lefebvre. “That does not lend itself to being comprehensively monitored.”
With Alaska’s significant, highly diverse marine wildlife populations (particularly its concentration of endangered species like the northern sea otter) and its dearth of marine mammal care centers, any significant amount of domoic acid could wreak ecological havoc.
Danny McCarthy 