The threat of a dangerous microorganism in the bay is real, but headlines have created an unhealthy level of ... Pfiesteria Hysteria We are left with a boatload of questions, but scientific -- evidence allows some conclusions

October 12, 1997|By JACK GREER AND MERRILL LEFFLER

All along the waterfront of the Chesapeake Bay - and far inland to our city streets and dinner tables - Pfiesteria piscicida has traveled like a rumor, picking up momentum along the way. (( In May, a Sun article ran under the headline "Fish-killing organism found in the Pocomoke." Two weeks later, the headline read: "Has microscopic monster moved into bay?" A week after that, the Washington Post led with "The Feeding Frenzy of a Morphing 'Cell from Hell.' "

What exactly is this one-celled creature? Where did it come from? What do we have to fear from it? And what does its appearance mean for the future of the Chesapeake Bay?

By now the story, in one form or another, is familiar. A million menhaden die in a North Carolina river. And then a million more. And a million more. Soon more than a billion fish have died in that state, many with ugly lesions.

In 1988, JoAnn Burkholder, an aquatic botanist at North Carolina State University, began to detail the life cycle of a peculiar marine microorganism, one that she and Karen Steidinger at the Florida Marine Research Institute named Pfiesteria piscicida.

Pfiesteria is not a bacterium or a virus but a dinoflagellate, a tiny single-celled organism that scientists call a "protist" because it is neither plant nor animal.

Burkholder found that Pfiesteria has many stages - as many as 24 - and that several of these forms can kill fish. Its tool is apparently a powerful pair of toxins - toxins that caught North Carolina researchers off-guard, sickening them before they realized they needed to improve their laboratories and equip them for a "Biohazard 3."

In a paper first published in the scientific journal Nature, Burkholder wrote that Pfiesteria may be a "widespread but undetected source of fish mortality in nutrient-enrichment estuaries."

And in 1992, a team of scientists led by Allen Lewitus, then at the University of Maryland Center for Environmental Science, found dormant Pfiesteria cysts in the sediment near the mouth of the Choptank River on Maryland's Eastern Shore.

When fish with lesions appeared in the Pocomoke River, about 30 miles south of the Choptank, Pfiesteria became a prime suspect. But there are many things that can cause lesions and so scientists and resource managers remained cautious, looking a range of possibilities. Then human symptoms appeared as well, and Pfiesteria was isolated in at least one of the water samples.

By the time more than 10,000 fish died in the Pocomoke, the story was picking up steam. Lesions on fish are not uncommon at certain times of the year or in pound nets where fish are trapped and can damage each other; but such lesions had not been associated with large fish kills in the Chesapeake. They were now seen as a sign of serious environmental problems.

Human symptoms found near the Pocomoke, at first puzzling, seemed to fit a pattern ascribed to neurotoxins such as those attributed to Pfiesteria.

Gov. Parris N. Glendening and his Cabinet conferred and closed the rivers - the story became national news.

Where are we now?

With the weather cooling and Pfiesteria settling down for the winter, we are left with a boatload of questions. Will the lesions come back? Will fish die in large numbers next year? Is seafood safe? Will those who work or play in parts of the Chesapeake run the risk of becoming sick?

Though we are far from having all the answers, a preponderance of scientific and technical information leads to the following conclusions:

* Pfiesteria has not contaminated Chesapeake Bay seafood. There have been no reported cases of seafood being tainted by Pfiesteria or of consumers becoming ill from eating seafood associated with Pfiesteria or Pfiesteria-like organisms.

* Pfiesteria is not the first toxic dinoflagellate to appear in the bay. Harold Marshall, a scientist at Old Dominion University in Norfolk, Va., has been studying algae in the Chesapeake for 30 years. He, with other researchers, has cataloged more than 700 species. Of these, he has identified nine dinoflagellates and three diatoms that have turned toxic in other parts of the world. Add another two dinoflagellates and one diatom from previous reports, and that adds up to 15 known species that could produce toxic blooms in the bay.

What is puzzling, and fortunate, is that so far none appear to have done so. In fact, the Chesapeake, the largest estuary in North America, has been remarkably free - so far - of the toxic blooms that have erupted in waters throughout the nation, in Atlantic coastal waters from Florida to North Carolina, along the coast of Maine, the Gulf of Mexico, and the Pacific Northwest. Outbreaks of paralytic shellfish poisoning, amnesiac shellfish poisoning, and other health threats related to toxic algae have led agencies to periodically close fisheries in those regions.

Pfiesteria is the first dinoflagellate to emerge as a prime suspect in a large Chesapeake fish kill, and this puts it in a unique position for the bay.

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