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.

There may have been more than 54, said Field, as they're still trying to confirm the diagnosis for some of the animals they've treated.

She indicated this is more challenging in the case of younger sea lions that come in for care with “reasonable body condition” but don't seem quite right. These animals might appear to improve, and then “boom, they get a seizure.”

While these events are regularly occurring, and there's some annual variability, Field also said she believes there has been an increase in incidents of domoic acid toxicity in sea lions over the past 20 years, since the center first diagnosed a case in 1998.

A 2012 overview of trends in toxic algae along the West Coast - published in the journal Harmful Algae - notes a body of evidence suggesting toxic blooms off of California have been worsening in the past 10 to 15 years. A 2018 study published in the same journal further identifies Southern California as a domoic acid hotspot.

Blooms could worsen by showing up earlier than they have in the past, persisting longer or covering more geographic area.

For example, David Caron, a USC biological sciences professor and co-author on the 2018 Harmful Algae study, talked about 2015 as the “year of the blob,” with a Pseudo-nitzschia bloom extending along the entire West Coast, making “everything red hot from Santa Barbara to Alaska.”

Caron cautioned that it can be difficult to understand long-term factors that affect where Pseudo-nitzschia will turn up.

Further clouding the waters is the fact that more toxic algae doesn't always equal more toxin. As Caron explained, even though Pseudo-nitzschia can produce domoic acid, it doesn't always.

According to Caron, some algae might produce toxins to poison their competitors.

“There is scientific information to suggest that if Pseudo-nitzschia run out of elements they need to grow, they may induce this response,” Caron said.

However, domoic acid's effects on marine mammals remain a conspicuous symbol of conditions in nearby coastal waters, and as Rulli noted, an important marker of ocean health - especially important when we are eating the same food as sea lions.

How do you treat a sea lion?

The Marine Mammal Center operates out of multiple locations across California - the main headquarters in Sausalito, along with field operations in five different counties.

San Luis Obispo County's facility in Morro Bay acts as a triage center and has two full-time staff members - including head of operations Diana Kramer - and a brigade of local volunteers essential for supporting day-to-day operations, including animal care and transport.

When team members respond to public calls about sea lions and other marine mammals, they use the pictures and video that often accompany them to determine the condition and size of the animal, along with the difficulty of rescue conditions.

Kramer said trained responders can then go see the animal and ask, “What are we seeing? Are we seeing signs that might indicate domoic acid toxicosis to us? Are we seeing injuries? Are we seeing thinness?”

“We have to weigh all the time how much stress are we going to put on the animal versus the assistance we can provide. And if the balance of assistance outweighs the stress, then we go ahead and rescue,” Kramer said.

After bringing in a sea lion, staff make the animal comfortable, assess their general health and then confer with the Sausalito headquarters' veterinarians about future treatment, which sometimes includes giving animals “sea lion Gatorade” and fish milkshakes.

Rescues are given a name, like “Landing,” to help staff distinguish triage patients during care. Kramer said it's really useful in instances when the center has multiple patients and “we're trying to make sure we that give each patient the correct medication, and the correct feed, and all of that.”

Kramer said the rescue team also doesn't want their patients to become accustomed to humans, as this can hurt their chances of survival after treatment and release.

For example, the herding boards used to safely corral patients have holes drilled into them, so if staff need to watch animals during feedings, they can curtail associating food with people. Kramer described this as “one extra step to keep patients wild, as they should be.”

Sick sea lions are cared for at the triage center for about a day to a week before either being released or relocated to a facility with additional resources.

What you can do to help marine mammals

Field said one thing the public can do for marine mammals in general is to keep from crowding them.

“Humans getting too close can cause more stress to already physically stressed animals who are stranding with health conditions,” Field said.

She suggests people use zoom lenses to take photos and videos as a possible solution.

People can also struggle with identifying an animal in distress. For instance, though some pups are assumed abandoned, it can be common for sea lions and seals to leave young on shore while off foraging.

This is why Rulli says, “We want to make sure people feel they have proper tools (and understand) that we are experts in the area when it comes to this, and they have our number in their back pocket.”

It can then be determined if an animal needs attention in the form of observation or care from the center or one of its partners.

Members of the public can report sightings of marine mammals they think might need assistance to the Marine Mammal Center's 24-hour hotline at 415-289-SEAL (7325).