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Sea lions and dolphins likely ill from algae
By Terry Rodgers - Staff writer
San Diego Union-Tribune
18th May 2003
Dozens of sea lions and dolphins that have turned up sick and dying along Southern California beaches in recent weeks probably are the victims of a toxic algae eaten by sardines, anchovies and other small fish.
A similar outbreak of marine mammal poisonings occurred last spring, sickening hundreds of dolphins and California sea lions from San Diego to Santa Barbara counties.
The animals became ill after eating small fish that had consumed a phytoplankton, or algae, containing a neurotoxin called domoic acid, said scientists with the National Marine Fisheries Service.
Domoic acid affects brain tissue, triggering seizures and causing the animals to become disoriented.
The toxin is harmful to humans, too, but only to those who consume clams, mussels or small fish that have gorged on the microscopic algae. People who swim in waters containing the algae are not at risk.
SeaWorld officials in San Diego say they're preparing to treat as many as 200 sick marine mammals this year, double the number they originally anticipated. The marine theme park, which participates in the federal government's Marine Mammal Stranding Network, has stocked up on medical supplies and plans to hire additional part-time animal rescue personnel.
"We have plenty of fish in the freezer" to handle the influx of stranded animals, said Tom Goff, SeaWorld's curator of mammals.
SeaWorld took in 170 sick marine mammals affected by the toxin last spring and winter. Sixty percent survived. Last year's outbreak in Southern California killed about 685 California sea lions and 75 common dolphins. Five hundred sea lions and 23 dolphins survived after getting ill and stranding themselves on shore.
SeaWorld veterinarian Judy St. Leger did breakthrough research by conducting brain scans on the sick animals to detect swelling or tissue damage, federal officials said.
Marine mammal rescue centers in Orange and Los Angeles counties are filled with sick animals brought in after beaching themselves.
Officials with the fisheries service said the outbreak this spring has so far killed 20 common dolphins and nine sea lions. Also, 40 sea lions and three common dolphins have become sick and have stranded themselves on Southern California beaches.
Neither of the species being affected are endangered. There are about 300,000 common dolphins living in California waters. California sea lions number about 30,000.
While the algae containing domoic acid were found off the California coast in the early 1980s, scientists suspect it was present in low numbers before that but simply went undetected. On the West Coast, domoic acid poisoning was first linked to illness in sea birds and marine mammals in 1991. Scientists still aren't sure what triggers the growth spurts of the algae each spring.
"We don't have a clue as to what is causing them," said Cordaro. "It appears to be a naturally occurring phenomenon."
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