An algae bloom in Southern California coastal waters has produced record levels of a toxic acid, scientists reported Wednesday. The chemical has been blamed in the deaths of numerous marine mammals and seabirds in recent months.
Measurements from four coastal stations last month found the highest domoic acid concentrations at 27 micrograms per liter, said David Caron of the University of Southern California.
"I have never seen these kind of numbers before," Caron said.
Last year, the highest levels stood at 12 micrograms per liter.
Recent measurements taken this month found the toxin levels had substantially declined, suggesting the seasonal algae bloom may have peaked, Caron said.
Domoic acid is a naturally occurring chemical produced by microscopic algae. Birds and sea mammals ingest the acid by eating fish and shellfish that consume the algae. People who eat fish and shellfish tainted with the acid can experience nausea, seizures and even death.
Last month, state health officials warned consumers against eating certain locally harvested shellfish and seafood that may be tainted with domoic acid.
Environmentalists have been concerned by the number and variety of sea lions, dolphins and birds that have washed ashore between Santa Barbara and San Diego. Some believe the dead and sick animals have been exposed to domoic acid poisoning.
NOAA Fisheries, the federal agency that oversees ocean fishing, has deemed the recent deaths of common dolphins and whales in California an "unusual mortality event." This would allow the agency to pour resources into determining what was causing the die-off.
Although the investigation is ongoing, domoic acid is the prime suspect, said Joe Cordaro, a federal wildlife biologist.
Cordaro cautioned that it's too soon to gauge the severity of this season's algae bloom on mammals and birds. The bloom typically starts in the spring and lasts for three months through early summer.
"At this point, we don't know if it's worse than the 2002-2003 event," Cordaro said.
A domoic outbreak in 2002 and 2003 sickened or killed more than a thousand sea lions and 50 dolphins.