Pin It

Blooming algae: Record numbers of single-cell organisms are producing a neurotoxin that affects shellfish 

There’s something in the water off the Central Coast: It’s a horde billions strong, roaring in numbers not seen in decades, producing a neurotoxin that can cause seizures, memory loss, and death.

It’s not oil. Beaches are reopening after the May pipeline rupture above Refugio State Beach; crude oil is sinking through the water column and out of view; and the Line 901 disaster is fading from the front page.

Instead, the culprit is a kind of algae: pseudo-nitzschia, a spindly little single-cell diatom that looks like a loose bead at the bottom of your grandmother’s jewelry box. Right now, there’s a bloom stretching from Alaska to the Santa Barbara Channel that’s bigger than anything that’s been seen in a decade. 

Michael Milstein, spokesperson for the National Oceanic and Atmospheric Administration (NOAA), called the bloom “unprecedented.” He said it was “higher than anything we’ve seen before, very high concentrations.”

Pseudo-nitzschia makes a neurotoxin called domoic acid. Injest enough of it, according to the California Department of Public Health, and you can get seizures and short-term memory loss. During a bloom, when warm oceans spur algae populations to explode, domoic acid builds up in oysters, mussels, and clams. 

On July 3, the department updated its warning to consumers for certain seafood caught in Monterey, Santa Cruz, and Santa Barbara counties due to high levels of the toxin: Don’t eat recreationally harvested mussels and clams and commercially or recreationally caught anchovy, sardines, or crabs taken from those counties. 

Scientists and government officials in Alaska, Oregon, Washington, and California test twice a year for domoic acid in those fish. In May of this year, researchers detected elevated levels of the neurotoxin, which indicated an algal bloom. 

A summer bloom is normal; the size of this year’s bloom isn’t. Raphael Kundela’s team at UC Santa Cruz tracked the bloom with boats and robotic gliders in Monterey Bay. 

“It appears this will be one of the most toxic and spatially largest events we’ve had in at least a decade,” Kundela, a professor in the ocean sciences department, said in a press release on UCSC’s website. One thousand parts per million is cause for concern, and the samples from Monterey Bay, according to the team’s preliminary findings, were between 15 and 30 times as high as that. 

It’s the biggest bloom researchers have seen since 1998—that’s the last time El Niño came around to warm up the Pacific. And, according to NOAA, it follows 2014, which had record-setting-hot temperatures for oceans.

You can’t get domoic acid poisoning from swimming in the ocean, according to the Department of Public Health. It’s dangerous when it builds up in shellfish or small fish that eat the toxic algae. Sea mammals that eat those poisoned shellfish can be poisoned as well.

Laura Sherr with the Marine Mammal Center told the New Times that domoic poisoning in marine mammals causes “lethargy, disorientation, seizures, and in some cases death.” Her organization rescued 712 California sea lions in 2014. A third had been exposed to the neurotoxin. 

“That’s an 11 percent increase from 2013 and an 18 percent increase from 2012,” Sherr said.

Sherr’s organization has admitted more than 100 animals affected by domoic acid so far in 2015. Some were Guadalupe fur seals, a solitary, isolated species of about 10,000 animals, with San Miguel Island and the Santa Barbara Channel holding the only population left in the United States.

The Northwest Fisheries Science Center reports on its website that domoic acid poisoning is to blame for a few human deaths and hundreds of cases of illness. Most of those cases came from an outbreak of food poisoning traced to shellfish harvested from one area off the coast of Prince Edward Island. Three people died, and roughly 100 were injured. Several survivors had permanent short-term memory loss.

In 1991, seabirds with guts full of anchovies started to litter the surf of the Monterey Bay. Their symptoms were consistent with neurotoxin poisoning, NOAA reported on its website, and the anchovies in their guts were full of domoic acid. Fisheries closed up and down the West Coast, and stringent testing measures were put in place to check different kinds of clams, oysters, and mussels for accumulation of the acid.

Now, in the midst of the biggest bloom anyone’s seen in years, the fisheries are closing again. In Monterey Bay, the Department of Fish and Wildlife has put a stop to shellfish harvesting. Some of Washington’s Dungeness crab fisheries, worth about $20 million a year, are also facing closures. 

Bernard Friedman, founder of Santa Barbara Mariculture, harvests oysters in the Santa Barbara Channel for a living. He told New Times that he shifts production around in anticipation of summer blooms. He was hopeful that the bloom won’t last too long. 

Milstein with NOAA wouldn’t guess how long the bloom will last.

“That’s the million dollar question at the moment,” he said. “There’s some concern that it could hang on through the summer. A storm or high wind could pick up, that tends to mix up the water and disperse the algae. So far, that doesn’t seem to be happening. There’s some sense that it may be around for a while.

“We can’t get rid of the algae,” he continued. “The best thing we can do at this point is to track it and know what areas are affected.”

Contact Staff Writer Sean McNulty from New Times sister paper to the south at

Pin It


Subscribe to this thread:

Add a comment

Search, Find, Enjoy

Submit an event

© 2022 New Times San Luis Obispo
Powered by Foundation