Marine life care centers across Southern California are experiencing an increase in stranded dolphins and sick seals, thought to be linked to a expanding toxic algal bloom off the coast.

The Marine Mammal Care Center, located in the greater Los Angeles area, and SeaWorld San Diego have both noted a rise in the number of stranded animals they are tending to, with many believed to be affected by the algae Pseudo-nitzschia.

NOAA states that if marine mammals consume shellfish that have been tainted by the algae, they can build up toxins, which can result in seizures, brain damage, and potentially, fatality.

“This week, we saw more stranded dolphins (both alive and deceased) than we saw during the major domoic acid (DA) bloom in 2023,” staff at the MMCC stated. “Recent testing in SoCal shows increased levels of the algae that produces DA, and we anticipate that it will only get worse in the coming weeks.”

During previous significant outbreaks, the neurotoxin did not appear to harm fish or pose a risk to swimmers. However, the public has been warned not to approach any stranded mammals.

The California Department of Public Health has issued an alert for residents not to eat sport-harvested mussels, clams, or scallops from Santa Barbara County. 

The agency warned that cooking does not destroy the toxin, and human symptoms include loss of balance, lack of muscular coordination, slurred speech, and difficulty swallowing.

The warning does not apply to commercially harvested shellfish, which are subject to frequent testing for potential toxins.

According to NOAA, significant upwelling of water helps the algae bloom grow along the immediate coastline. 

The phenomenon is common during the spring and summer, as winds mix colder waters with warmer surface waters.

While agencies were concerned about the potential health impacts of runoff from recent fires, they believe the current event is directly tied to the Pseudo-nitzschia bloom.

Locals say that significant blooms typically occur every 4-7 years, but they have noticed an uptick in activity in recent years, which could be due to various factors.

“Domoic acid is a naturally occurring toxin that has existed for centuries and was first identified in Japan in the late 1950s. Although domoic acid wasn’t detected in California until 1991, the prevalence of toxic algal blooms along the Pacific coast has increased dramatically in recent years. Researchers say human activities like increased fertilizer use, sewage runoff, and warming waters due to climate change create the types of conditions in which algal blooms like these thrive,” the center stated.

If you spot a stranded animal, the MMCC advises there are several steps you can take to help.

First, keep at least 50 feet away from the animal to minimize stress and call the stranding hotline at 1-800-399-4253 to report your location.

The worst thing you can do, experts say, is try to interfere with the animal or push it back into the water.

Finally, marine experts suggest keeping noise to a minimum and ensuring dogs and large crowds.