By Maddie White
Click here for updates on this story
SAN FRANCISCO (KPIX) — They’re loud, playful and one of San Francisco’s most recognizable icons. But this summer, sea lions along the Central California coast are also signaling a troubling change in the ocean.
Rescuers are responding to a surge in sea lions sickened by domoic acid, a neurotoxin produced by naturally occurring harmful algal blooms. The Marine Mammal Center says it has already rescued more than 150 sea lions with domoic acid poisoning this year — more than twice its typical annual total.
At San Francisco’s Pier 39, where sea lions have become a tourist attraction, the animals appear healthy and energetic.
But elsewhere along the coast, many are struggling. That includes the animals that are brought into Sausalito’s Marine Mammal Center, the world’s largest marine mammal hospital and a non-profit organization dedicated to rescuing, rehabilitating, and releasing sick, injured, or abandoned marine mammals.
“They’re telling a story,” said Giancarlo Rulli, who has worked at the Marine Mammal Center for 22 years.
That story, he said, is about a severe outbreak of domoic acid poisoning — and potentially about changes taking place in the ocean.
“We’re in the midst of a severe outbreak of domoic acid poisoning,” Rulli said. “And how, in turn, that can also have implications for us as humans as well.”
One sea lion found at San Francisco’s Crissy Field this week was displaying symptoms including head weaving and bobbing before it eventually died from domoic acid poisoning.
The toxin is produced by certain algae and enters the food chain when fish consume the algae. Sea lions then ingest the toxin when they eat contaminated fish.
“It can cause lesions on the brain,” Rulli said.
The effects can include lethargy, twitching and seizures.
Researchers are studying what may be contributing to the current outbreak.
Dan Costa, a distinguished professor of ecology at UC Santa Cruz, has been tracking sea lions and their movements. He said warming associated with El Niño may help create conditions favorable for harmful algal blooms.
“Because of the El Niño you have warming, which probably helps the harmful bloom,” Costa said. “And then that domoic acid gets released, fish eat it, and then it biomagnifies in the fish.”
Costa has also found sea lions moving farther north, where colder waters can provide more favorable conditions for the fish they depend on.
“The conditions are more favorable up here for fish,” he said.
But that movement can create another problem: when mothers travel north to feed, their pups can be left behind in Southern California.
“Then so you’ve got these poor little pups sitting on the beach starving to death,” Costa said.
He said the larger lesson extends beyond the animals themselves.
“The best thing we can do is to reduce human activities that put pollutants in the water,” Costa said.
The California Department of Public Health told CBS News Bay Area that an increase in sick or stranded marine mammals can be one indicator that a harmful algal bloom producing domoic acid may be present, though it is not the only measure the state uses. The agency monitors seafood for the toxin year-round and increases testing when risk indicators are present.
The health department spokesperson added that serious illness or death can result if contaminated seafood is consumed by humans. They advise consumers to check current seafood advisories and fishery closures before eating locally caught seafood.
Meanwhile, the influx of sick sea lions is putting enormous pressure on the people trying to rescue them. At the Marine Mammal Center’s call center in Sausalito, staff are fielding hundreds of reports.
Justin Hodges said the number of calls involving sick sea lions has increased three to six times in recent weeks.
“Last year was about 60 to 100 calls a day and now we’re looking at 300 to 600 calls per day,” Hodges said.
Each rescue can require a team of four to six people, sometimes moving an animal weighing more than 300 pounds.
“It’s extremely labor intensive and physical,” Rulli said.
With more calls than responders can immediately handle, the center has been forced to triage cases based on the animal’s condition, location and available personnel.
For sea lions suffering from domoic acid poisoning, treatment can include anti-seizure medication and fluids to help the body process the toxin. But many animals do not survive.
“It always hits home. It’s disturbing. It’s highly emotional,” Rulli said. “You can feel quite helpless, especially when there’s an outbreak happening of this magnitude.”
Still, there are moments of hope.
On Thursday, the center released three rescued sea lions back into the wild.
For Hodges and the volunteers who clean carriers, care for animals and answer the seemingly endless calls, those releases are reminders of why they keep showing up.
“This work can be challenging yet incredibly rewarding,” Hodges said.
For rescuers, each successful release is a small victory during an overwhelming season — and one more sea lion given the chance to return home.
Please note: This story was provided to CNN Wire by an affiliate and does not contain original CNN reporting. This content carries a strict local market embargo. If you share the same market as the contributor of this article, you may not use it on any platform.
