Domoic Acid

By Becca

This summer, there was an extremely dangerous domoic acid outbreak that occurred in southern California. At Camp Emerald Bay, we heard a lot of reports about the outbreak, and then sea lions started to swim in waters only 5 feet deep, or sleeping on our docks for weeks straight. This was obviously quite odd behavior. The staff would have to move the poor animals off the docks so we could proceed with swim checks on Sundays. The domoic acid outbreak thankfully began to slow down, and less seals and sea lions were affected, but we are here to tell you what domoic acid is, how it affects animals, and why this whole thing began anyway. 

What is domoic acid?

Domoic acid is a neurotoxin that is produced by the algae Pseudo-nitzschia australis. When small fish like sardines, anchovies, and shellfish consume this algae, they are not affected by domoic acid, but when sea lions, otters, cetaceans, humans, and other predators the neurotoxin is able to take effect. For the seals and sea lions that consume these fish, domoic acid toxicosis and poisoning can occur. 

Domoic acid toxicosis/poisoning

For seals and sea lions, domoic acid can cause omiting, unusual behaviors, including aggression, seizures, loss of pregnancy, and death. Domoic acid affects the brain and the heart causing these seizures and potential heart failure. For the many pinnipeds that are not treated, it can cause permanent brain damage. The toxin will naturally flush from an animal’s system over time, but sea lions repeatedly exposed to the toxin will suffer longer-lasting and more serious effects. Humans can also be affected by domoic acid if they consume any of the fish that have eaten the algae. In humans, amnesic shellfish poisoning occurs, which takes effect within a day of consuming the affected fish. 

Why was it so bad this year?

This summer, there was a particuularly bad outbreak of domoic acid. In southern California, there were reports of sea lions attacking beach-goers, which is extremely abnormal behavior. Rehabilitation centers were overcapacity with reported cases. Here at camp, we had an injured pelican one week and called for someone to come out andd help the bird, but everyone we called said all their cars and boats were used up dealing with domoic acid cases. In a normal year, domoic acid is present in the water, but it becomes a problem when there is an excess of the algae in the water. A recent study found that due to climate change and ocean acidification, domoic acid increases during a spring to summer succession of coastal phytoplankton. Professors at UCSC have also been researching what triggers the actual production of domoic acid in the algae Pseudo-nitzschia australis.

Moving Forward

If the study is correct, domoic acid is a problem that will continue to persist in summers to come. That leaves it up to us to make sure we are prepared, and that we respect wildlife. Many of the attacks and bites from sea lions this summer could have been prevented if people would have given the animals some distance. It is recommended that humans give seals and sea lions at least six feet of space, to protect everyone.