The mystery surrounding the death of the sperm whale that washed up in Isla Vista last month may have been solved.

Local scientists have determined that a bloom of algae has been producing a poisonous, fatal acid that infected local shellfish, and resulted in the death of a number of fish and birds. According to local marine biologist Gregg Langlois, domoic acid is a toxin found in algae, more specifically a strand called -nitzschia, which blooms in high concentration during the spring and summer months every year.

However, Langlois said the toxin has been more aggressive in the county over the past few years.

“The algae has been blooming early, and during that time, Santa Barbara has had the highest count of domoic acid,” Langlois said. “Santa Barbara is a hotspot.”

Half a dozen dead fish and birds have been found in Santa Barbara because of the poisonous acid, said Scott Simon, manager of the Marine Science Institute at UCSB.

The growth of the algae is due in part to upwelling – a wind-driven natural phenomenon that drives the cooler, commonly nutrient-rich water, to the surface of the ocean, replacing the warmer water. As a result, the phytoplankton the algae grow on have the nutrients necessary to flourish.

Langlois said domoic acid is bioaccumulating; the shellfish that feast on the plankton and get infected with algae are then eaten by other sea creatures, passing the toxin on.

This can result in the death of mammals as high in the food chain as whales. In fact, the 29-foot sperm whale that washed ashore on April 9 may have died from consuming the poisonous algae.

Investigators have tested the tissue samples of the sperm whale to detect its cause of death, but the carcass may be too decomposed to elicit a definite answer.

The California Department of Health Services issued a news release on April 20 to warn the public of paralytic shellfish poisoning (PSP) and domoic acid poisoning (DAP). The chemicals can infect humans if toxic mussels are consumed. A second news release sent out last Friday provided a list of seafood to avoid eating and included the Southern California counties that may be affected.

The news release listed Los Angeles, Orange, San Luis Obispo, Santa Barbara and Ventura counties as having “elevated levels of domoic acid in sardines and mussels.” It also stated that, “other seafood, including bivalve shellfish such as oysters, clams and scallops and the viscera of anchovies, crab and lobster, have not been tested, but could also contain dangerous levels of toxin.”

In humans, domoic acid poisoning can cause vomiting, abdominal cramps, diarrhea, headache, disorientation, seizures and loss of short-term memory. Severe cases may lead to death or result in permanent short-term memory loss, according to the Department of Health Services.