San Francisco Chronicle: Scores of Sea Lions Dying

Scores of sea lions dying

Mammals washing ashore after eating food tainted by toxic algae

Picture

Nicole Boliaux / The Chronicle

Veterinarian Geraldine Lacave uses a wooden board to block a California sea lion during a neuroscore exam to evaluate the cognitive brain function in another sea lion suffering from domoic acid poisoning at the Marine Mammal Center in Sausalito.

Scores of convulsing sea lions are washing up on Central California beaches after eating fish poisoned by a plume of toxic algae that could spread north toward the Bay Area and cause widespread problems, marine biologists said.

Since June, veterinarians at the Marine Mammal Center in the Marin Headlands have treated 89 animals — all but seven of them sea lions —plucked mostly off beaches near San Luis Obispo, where a large algal bloom formed in the ocean.

Of the 82 sea lions brought to the center, 31 have died, and virtually all of them had seizures caused by domoic acid, the dreaded neurotoxin that closed down the Dungeness crab season two years ago and killed off thousands of marine species over the past two decades, said Shawn Johnson, the center’s director of veterinary science.

“We’ve rescued 64 animals just in July,” said Johnson, who coordinates the rehabilitation of injured marine mammals rescued from San Luis Obispo to the Oregon border. “They’ve been coming in huge waves, as many as 10 a day.”

The coming crab season, which typically kicks off in November, is not currently being threatened, but state health officials are monitoring the situation to see if algal blooms begin cropping up farther north as ocean temperatures climb in the late summer and fall.

The stakes are high for the environment and for the fishing industry. More than 21 million pounds of Dungeness worth $66.7 million were pulled in during the 2016-17 season, the best haul in four years and almost double what was taken a year earlier when much of the California coast was blanketed in algae, prompting fishing restrictions and health warnings.

The latest bloom, known as a red tide, appears to be on a northward trajectory. Starting in April, dozens of sick and dying sea lions, dolphins and fur seals were found on beaches in the Los Angeles and San Diego areas.

Over the past two months, most of the poisoned sea lions, fur seals and sea otters have been washing up on beaches around Oceano Dunes State Vehicular Recreation Area in San Luis Obis-po County, Johnson said. Many of the rescued sea lions were lactating females that had been foraging near the Channel Islands for food to feed their pups.

“To have them so concentrated in such a short time period is unusual. That tells us there is a really toxic bloom of algae in that area,” Johnson said. “As the water temperatures increase over the summer, we see this bloom migrating farther north, so it’s possible we could see it reach the Monterey Bay area in the late summer and fall.”

Outbreaks like this one have been sickening increasing numbers of marine mammals since the first toxic bloom was documented on the West Coast in 1998, when 400 sea lions washed ashore in Monterey Bay.

The culprit was a microscopic, single-celled species known as pseudo-nitzschia, which produces domoic acid. The algae grows thicker and faster in warmer, nutrient-rich seawater, and the toxin it produces accumulates in shellfish, mussels, anchovies, sardines and herring, the primary food of sea lions.

When it is sufficiently dense, it attacks the hippo-campus, the brain’s memory center, and can cause memory loss, tremors, convulsions and death. The toxin, which accumulates in the bloodstream, can also sicken people who eat fish, crab or mollusks.

The Marine Mammal Center has picked up an average of about 70 poisoned marine mammals each year since 2009, officials said. Scientists now consider the toxin to be one of the biggest year-round biological threats along the California coast. But the problem isn’t isolated to California, as marine biologists say algal blooms are growing all over the world as oceans warm.

The death toll hit its peak on the West Coast in 2009, 2014 and 2015, when unusual atmospheric conditions heated up coastal waters and created havoc in the ecosystem. The 2015 bloom, the biggest recorded, spread all the way to northern Washington. More than 2,500 animals were stranded on California beaches that year — about 10 times the average rate.

The crisis, which also triggered die-offs of Northern California birds and fish, forced regulators to keep the Dungeness crab season closed until March, when the season is usually winding down. While this year’s conditions are not nearly as dire, the uptick in strandings last month caused alarm among marine biologists.

“This is a little unusual,” said Clarissa Anderson, executive director of the Southern California Coastal Ocean Observing System and a researcher at the Scripps Institution of Oceanography at UC San Diego. “It’s a bigger stranding event than we’ve seen in that area for a long time.”

The California Department of Public Health warned consumers not to eat shellfish caught in the northern Channel Islands after detecting dangerous levels of domoic acid in May.

Despite the increase in toxic algae, only four people are known to have have died following exposure to domoic acid. They were among 250 people who became ill in 1987 after eating contaminated mussels from Canada’s Prince Edward Island.

Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com Twitter: @pfimrite

“We’ve rescued 64 animals just in July. They’ve been coming in huge waves, as many as 10 a day.”
Shawn Johnson, Marine Mammal Center director of veterinary science