Sea Life in Santa Monica Bay Suffering From Demoic Acid Toxicosis, Caused by Algae

We found a seal suffering on Santa Monica beach Saturday. Her stomch was undulating, and she was apparently unable to move away from the waves. We called a rescue organization, and also a marine biologist. "I’d be happy to explain what’s happening to that poor seal in simple terms," he said.

"Domoic Acid Toxicosis is a condition caused by a natural toxin called domoic acid, which is produced by certain types of microscopic algae (specifically, a group called diatoms). These algae are part of the ocean’s food chain and get eaten by small fish or shellfish, like sardines, anchovies, or clams. Seals, being higher up the food chain, eat these fish or shellfish. If the algae have been producing domoic acid, the toxin builds up in the prey and then gets concentrated in the seal’s body when it eats them. This is called bioaccumulation.

Once the domoic acid is in the seal’s system, it acts like a neurotoxin—meaning it messes with the brain and nervous system. It overexcites the nerve cells, kind of like pressing the gas pedal on a car way too hard, which can cause all sorts of problems. For the seal you found, this might show up as confusion, seizures, tremors, or even just lying there looking weak and disoriented. In bad cases, it can damage the brain permanently or even be fatal if the seal can’t recover.

This usually happens when there’s an algae bloom—a big explosion of these toxin-making algae in the water, often triggered by warm ocean temperatures or nutrient-rich runoff from land. Sadly, seals don’t know their food’s gone toxic, so they keep eating and end up suffering.

"I'm glad to hear wildlife rescue is on the way-that's the best shot this seal has! Whether they can save her depends on a few things, but there's definitely hope," said our expert.

"The key factors are how much domoic acid she's been exposed to and how long it's been affecting her. If she's still alive and showing signs like tremors or confusion, but hasn't gone into a coma or stopped breathing, there's a decent chance they can help. Rescue teams usually focus on supportive care-things like flushing the toxin out with fluids, controlling seizures with medication, and keeping her hydrated and stable. They'll probably take her to a rehab facility where vets can monitor her closely.

"Her odds also depend on how quickly they get to her and how bad the brain damage is. If she's caught early, before the toxin does permanent harm, she might recover fully and even be released back into the wild. Studies show some seals bounce back surprisingly well with treatment-sometimes in a few weeks if the dose wasn't too high. But if she's been suffering for a while or the exposure was massive, it could be tougher, and in the worst cases, they might have to make the call to euthanize if she's in too much pain or can't recover.

"Since you got help on the way fast, that's a big plus. The pros will know what to do when they see her condition up close. Fingers crossed for her-let me know how it turns out if you hear back!"