msnbc.com staff and news service reports
updated 3/25/2004 10:55:55 AM ET 2004-03-25T15:55:55

The death toll among dolphins in Panhandle bays and beaches has climbed to 90, but the cause of the deaths remains a mystery, officials said Wednesday.

Tissue analyses indicate the dolphins had been exposed to red tide, a toxic algae known to kill sea life. But more tests are pending, said Blair Mase, a coordinator for the National Marine Fisheries Service.

The analyses also detected domoic acid, another naturally occurring toxin, but one common to California waters, Mase said.

Some captive dolphins sick, too
“We don’t know what that means,” she said. “We’re still putting together the pieces of the puzzle.”

Under normal circumstances, 10 to 20 dolphin carcasses wash up each year. From several dozen found earlier this month, the number has since reached 90.

Two captive dolphins were also sick at a marine park where a pair of the mammals died last week. Gulf World Marine Park, in Panama City Beach, is awaiting pathology results to determine whether those dolphin deaths can be linked those in the wild.

The park takes in water from the Gulf of Mexico, said park co-owner Ron Hardy.

Impacts of red tide
Red tide is an above-normal concentration of a microscopic alga. In Florida, the alga that most often causes red tides is  Karenia brevis, which produces a toxin that can kill marine life by affecting their central nervous system. Humans exposed to it may suffer temporary eye and respiratory irritation.

Red tides are not always red, in fact the seawater can retain its normal color or appear greenish, brownish and even purple.

Red tides occur around the globe and while natural they might be affected by variables like  temperature, water salinity, currents, nutrients and competing species.

One recent theory is that blooms in Florida are triggered iron from dust particles blowing over the Atlantic from the Sahara desert.

Additional background on red tides is online at www.redtideonline.com.

The Associated Press contributed to this report.

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