Sunday, March 22, 2009

Deadly Nerve Toxins Affecting Deep Ocean Creatures

By Julie Steenhuysen

CHICAGO (Reuters) - A nerve toxin produced by marine algae off California appears to affect creatures in the deep ocean, posing a greater threat that previously thought, U.S. researchers said on Sunday.

Surface blooms of the algae known as Pseudo-nitzschia can generate dangerously high levels of domoic acid, a neurotoxin blamed for bizarre bird attacks dramatized in Alfred Hitchcock's 1963 film "The Birds."

"It's a natural neurotoxin. It is produced by a diatom, which is a phytoplankton. As other animals eat this phytoplankton, like sardines or anchovies, this toxin can be transferred up the food chain," said Emily Sekula-Wood, a doctoral student at the University of South Carolina whose study appears in the journal Nature Geoscience.

Domoic acid has been linked to deaths of sea lions, whales and other marine animals and people who eat large quantities of shellfish.

"If you consume enough of it, you can get brain damage. In humans it's called amnesic shellfish poisoning. You experience short-term memory loss," Sekula-Wood said.

Large toxic blooms of Pseudo-nitzschia have closed beaches and disrupted the shellfish industry in the western United States. They have been implicated in toxic blooms throughout the coastal waters of Europe and Asia and North America.

Monitoring programs test the surface blooms for the toxin.

Sekula-Wood and colleagues looked to see whether the toxin was reaching the ocean floor.

"We used a sediment trap. It is like a rain gauge that you put out in a water," she said.

The trap, set 500 meters (1,600 feet) and 800 meters (2,600 feet) below the surface of the ocean, filtered out toxins that sank after an algal bloom.

They found that large quantities of domoic acid were sinking to the ocean floor, invading the deep-sea food chain.

And the toxin appears to linger.

"Our data further confirm that domoic acid-laced sinking particulates are incorporated into underlying sediments, where they are available for consumption and incorporation into bottom feeders," the researchers wrote.

"It can make us think about the longevity of these toxins," Sekula-Wood said.

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