Why toxic algae is especially dangerous for California sea lions this year
On a beautiful Friday in July, a dehydrated young sea lion was rescued from the Harford Pier by the Marine Mammal Center’s San Luis Obispo County rescue team.
Pier visitors noticed the curious sea lion had been lounging on a floating dock for a suspiciously long time.
This California sea lion, later dubbed “Landing,” represents one of the hundreds the center cares for every year, including a large number suffering poisoning from an algal toxin called domoic acid.
Dr. Cara Field, one of the center’s veterinarians, said this year is especially alarming because the algal blooms responsible for producing domoic acid have started earlier than usual — just in time to target “adult female sea lions making their way to the Channel Islands to give birth” and “a whole second generation” of unborn sea lion pups.
Sea lions harmed by toxic algae
The source of domoic acid — a potent neurotoxin — is a microscopic plant-like organism called phytoplankton.
When one particular species called Pseudo-nitzschia finds just the right sweet spot of conditions, it can rapidly reproduce and form a “ bloom.”
People unfortunate enough to be exposed to domoic acid by eating tainted shellfish can develop amnesic shellfish poisoning. Severe cases of the condition, as described by the California Poison Control Network website, includes “short-term memory loss, seizures, coma or shock” — although these cases are rare thanks to precautions taken by the state Department of Public Health.
Marine mammals are also susceptible to poisoning but don’t have a warning system in place like we do.
Guadalupe fur seals and sea otters are just some species that can be impacted, according to an email from Giancarlo Rulli, marketing and communications associate at the center, but it is primarily the California sea lion that bears the brunt of domoic acid toxicity on the Pacific Coast due to its diet.
Sea lions accrue the toxin in their body because they preferentially eat large amounts of small fish like sardines that have also been exposed, Field explained during a phone call.
Sea lions showing signs of gastrointestinal distress may have been exposed to low doses of toxin. Those with more serious seizures and neurological symptoms have likely been exposed to higher levels of domoic acid, Field said, and can suffer permanent brain damage and end up in an epileptic state.
“It depends on the amount of domoic acid that ends up in their systems,” Field said when asked how these poisoned animals would fare without intervention. “Those animals with neurological symptoms would be much more likely to die.”
Field further explained that when pregnant females are exposed to domoic acid they don’t clear the toxin from their system in one to two days like other sea lions. Instead, the domoic acid is retained in amniotic fluid where it recirculates in the animal’s body for days to weeks, continually exposing mom and unborn fetus to its affects.
The resulting pups may survive the ordeal, but could later starve to death if their mothers succumb to the effects of domoic acid toxicity while out searching for food.
Are more sea lions being poisoned by domoic acid?
The average number of statewide yearly sea lion domoic acid cases is between 65 and 70, according to Rulli, but there’s already been at least 54 poisonings treated as of June — in a season that will continue well into the fall.