The deaths of four dolphins and four sea lions found on a Southern California beach are likely linked to a natural neurotoxin called domoic acid.
Volunteers from the Channel Islands Marine and Wildlife Institute found the dead sea creatures Friday on Mandalay Beach in Oxnard.
The institute later confirmed the animals died of natural causes not related to fishing or a nearby power plant.
Marine biologist Tom McCormick told the Ventura County Star that seasonal "red tides" bring plankton species that produce domoic acid. The toxin gets concentrated in smaller fishes, such as anchovies and sardines, which are eaten by larger animals like dolphins and sea lions. The result can be fatal.
“This is a neurotoxin that is picked by the filter feeders in the water," McCormick, who has worked for more than 20 years on the Ventura County shorelines, told the local newspaper. "The smaller fishes, such as anchovies and sardines, eat the filter feeders, and the toxins get concentrated in the animals that eat the smaller fishes. Sometimes, you will see a sea lion on the beach jerking and contorting due to this toxin — it's really heart-wrenching."