What’s wrong with sea lions stranded on California beaches?

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<p><figcaption class=Photo: David Swanson/Reuters

The calls in question began in mid-August. Sea lions — mostly adult females — turned up off the Southern California coast with signs of intoxication: disoriented and agitated, head bobbing and mouth foaming.

Marine wildlife organizations say they’ve been inundated with inquiries from alarmed beachgoers. “We respond to 50 to 100 calls a day,” the Channel Islands Marine and Wildlife Institute, which works in the island region off the coast of Los Angeles, wrote on Instagram.

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The cause was quickly identified as domoic acid poisoning – a naturally occurring neurotoxin produced by a tiny single-celled seaweed. The neurotoxin accumulates in crustaceans, small fish and squid and is then transmitted to larger predators such as sea lions.

While most animals usually recover from the worst symptoms within a few days after excreting the acid through their urine, the Channel Islands Institute said more than 60 sea lions have been stranded in recent weeks. One died after suffering a seizure on a crowded beach near Ventura Pier.

Scientists are now working to figure out exactly what happened and what made this particular algal bloom so bad. They’re also studying how warming oceans are changing the behavior of domoic acid, which is abundant along the California coast.

Clarissa Anderson, a scientist who directs the Southern California Coastal Ocean Observing System, was among those who received reports of sick sea lions. She immediately checked observation stations that take weekly samples from piers along the California coast.

Man holding a crab over a yellow bucket

Neurotoxins from algal blooms can accumulate in animals like Dungeness crabs and have even forced the closure of the fishing season. Photo: Jane Tyska/AP

None of the near-shore samples showed any blooms, she says, suggesting the event appeared to be taking place in the deeper waters near the Channel Islands, where most of the sick sea lions emerged.

Blooms of the algae that make the neurotoxin are a natural seasonal occurrence in California, Anderson says, but having one this late in the summer is unusual. “We expect the peak to be even bigger in April or May,” Anderson says, because the organism is very responsive to coastal upwelling — when strong winds cause deep waters to rise to the surface and bring nutrients to the surface that the algae need to thrive – which usually happens in the spring.

Southern California is emerging as a domoic acid hotspot: the world’s highest waterborne reading of the neurotoxin was in March 2011 near San Pedro in southern LA County. It was 52.3 micrograms per liter – about five times higher than a worrying level.

It really is a crisis in Ventura and Santa Barbara counties for these sentinel species

Clarissa Anderson

The acid can be transmitted from animals to people who eat toxic seafood — within 30 minutes to 24 hours after eating, people may experience vomiting, diarrhea, abdominal cramps, headaches, and dizziness. Crustaceans, fish, and shellfish can all have high levels of domoic acid without showing symptoms, according to the California Department of Health. Also known as the red tide, the threat of the toxin previously ended the razor clam and crab fishing season from Monterey Bay to Alaska, costing the fishing industry millions in lost revenue.

Vera Trainer, a scientist at the Noaa Northwest Fisheries Science Center, says scientists studying the large blooms of the Pacific Northwest have discovered how resilient the organism is. “They can withstand very intense and stressful environments,” she says, as they fall to the bottom of the ocean as sea snow and wait in a hibernating state for the proper nutrients to bounce back and return to the surface.

A group of sea lions swim in the kelp forest surrounding the Channel Islands in California.

A group of sea lions swim in the kelp forest surrounding the Channel Islands in California. Photo: Antonio Busiello/Alamy

That could mean that domoic acid is adapting well to warming ocean waters. “We have evidence that these cells work well when the water is warm, and we have evidence that they work well in nutrient-poor environments followed by rapid nutrient delivery,” says Trainer. “And that’s likely to happen more and more as the climate changes.”

Blooms like these are more likely to be in a future ocean that’s warmer — but the science is complex because the algal species actually does better in colder waters, Anderson says, making it difficult to predict exactly how it will behave. “Temperature is just one of many factors that stimulate these blooms,” she says. “You need nutrients in a certain combination to turn on the venom.”

Researchers are also trying to understand whether new strains of algae that thrive at higher temperatures might be developing. Anderson says some tribes are migrating farther north — to places that were previously too cold for them. But one thing is clear, she says: “In the last 20 years, they have become more common and more toxic.”

Anderson says she’s still trying to investigate and figure out what happened to trigger the bloom. Most of the affected sea lions will recover, but repeated exposure to the toxin can have more serious and longer-lasting effects — and sea lions are particularly at risk because they eat so many sardines and anchovies, which build up the toxin in their bodies.

Channel Islands Institute staff continue to treat sick and stranded sea lions, they say, but are concerned about what lies ahead. “It really is a crisis in Ventura and Santa Barbara counties for this sentinel species.”

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