3 new Pfiesteria-like microbes found in Shore waters

October 30, 1997|By Douglas M. Birch | Douglas M. Birch,SUN STAFF

Pfiesteria piscicida isn't the only potentially toxic microbe lurking in Chesapeake Bay tributaries, a Florida scientist said yesterday.

At least three similar organisms might have played a role in the fish kills that have closed three waterways on the lower Eastern Shore in recent months.

Karen Steidinger of the Florida Department of Environmental Protection told a meeting of scientists at the Columbus Center yesterday that she has identified Pfiesteria in water samples from the Chicamacomico River in Dorchester County.

A six-mile stretch of that river was closed Sept. 14, a day after the waters churned with dead and dying fish. It is expected to reopen tomorrow.

Seven Department of Natural Resources employees who took water samples and monitored the kill later reported suffering short-term memory loss and other symptoms similar to those produced by Pfiesteria's toxins.

But Steidinger couldn't find Pfiesteria in the Pocomoke River or Kings Creek, Somerset County waterways that also were closed.

Instead, she found three previously unknown Pfiesteria-like organisms. All three turned up in the Pocomoke River, the site of this summer's biggest fish kills.

One of the new species showed up in Kings Creek, and another was found along with Pfiesteria in the Chicamacomico.

Pfiesteria piscicida, one of a group of organisms known as dinoflagellates, was first considered the prime suspect in each of the incidents. Closer scrutiny showed that the picture was more complicated than had been anticipated.

"Once you go into a new habitat nobody's ever looked at, you're going to find new stuff," said Steidinger. "We're finding tons of new dinoflagellates."

Ironclad identification took so long, Steidinger said, because Pfiesteria and the new species are so tiny, so difficult to raise in a laboratory and look so much alike. She identified them with a scanning electron microscope.

JoAnn Burkholder of North Carolina State University had tentatively identified microbes found in the same lower Eastern Shore water samples as "Pfiesteria-like." But Burkholder, considered the leader in Pfiesteria research, always warns that she uses crude techniques to quickly spot suspect organisms.

Steidinger, her collaborator, makes a more careful microscopic examination to positively identify the microbes.

Yesterday, Burkholder hailed Steidinger's discovery of Pfiesteria in the Chicamacomico, saying it helps build the case against Pfiesteria as a public health threat.

Since 1991, Pfiesteria piscicida has been linked to toxic blooms that have killed more than a billion fish in North Carolina. But health officials there have not been able to connect those incidents to cases of human illness.

Some of those officials, Burkholder said, have suggested that people who got sick in Maryland might have come in contact with a different, more toxic organism than Pfiesteria piscicida.

The discovery of Pfiesteria in the Chicamacomico suggests that Maryland and North Carolina residents face the same peril, she said.

Steidinger said she had found three new organisms in the Pocomoke. She has nicknamed one Shepherd's Crook, another she calls a peridiniopsid, and a third is a previously unknown species of an organism, of the genus Gyrodinium, that has caused fish kills in Europe.

The new Gyrodinium species also has been found in Kings Creek, near Princess Anne, she said.

Pfiesteria is a tough, elusive organism able to survive acid baths and transform itself into at least 24 shapes.

Maryland scientists will have to study at least three other Pfiesteria-like species to learn how big a threat they pose.

In all, scientists have discovered at least 10 Pfiesteria-like species in Maryland and other states, Steidinger said.

Pub Date: 10/30/97

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