Marine deaths linked to toxin
A particularly virulent outbreak of naturally occurring toxin off the California coast has been linked to the deaths of hundreds of marine mammals and birds in recent weeks, researchers said Thursday.
"I have been doing this work for 35 years and I have never seen anything like this as far as the number of species affected, other than an oil spill," said Jay Holcomb, director of the International Bird Rescue Research Center in San Pedro. Local beaches have been littered with sick and dead pelicans, sea lions and dolphins.
"We have very serious concerns about what is happening to seabirds and how it may affect populations, especially California brown pelicans, who are heading into breeding season," he said.
The toxin, domoic acid, is produced by microscopic algae and has become increasingly prevalent in recent years. Scientists suspect the upsurge has been caused by such things as overfishing, destruction of wetlands and pollution, all of which have harmed fisheries and allowed algae to flourish.
Although the toxin has not been definitively linked to all the recent deaths, many of the dead animals -- including five species of birds -- tested positive for domoic acid poisoning, said scientists at the rescue center and the Caron Laboratory at USC.
Domoic acid, which accumulates in shellfish and fish and is then passed on to the birds and animals that eat them, has occurred each spring over the past decade as ocean water warms and algae bloom. But this year's algae are "especially virulent," according to the rescue center.
The center is working closely with the Caron Laboratory, which is conducting analysis of sick birds found on beaches.
"In five years of study I have not seen a bloom this large at this particular time of year," said Professor Dave A. Caron, the lab's director and a biological oceanographer. "It's having an extraordinary impact on pelicans and many other species."
Dead birds began littering Southland beaches in March. Staffers with the bird rescue center walking the beaches reported seeing "dead birds everywhere," including grebes, gulls, cormorants, American avocets and loons.
Scientists are particularly concerned about the toxin's effect on brown pelicans, which declined precipitously in California after DDT entered their food chain and caused the large seabirds to lay eggs with shells too fragile to support their weight. The birds remain on the endangered species list, although they have made considerable gains in recent years.
