Conditions right for toxic Pfiesteria in area waterways

Organism could appear by summer if drought continues, scientist says

March 02, 2002|By Heather Dewar | Heather Dewar,SUN STAFF

Conditions are right for toxic Pfiesteria to appear in Middle River and some upper Chesapeake Bay creeks later this summer if the region's deep drought doesn't break, said a top Department of Natural Resources scientist.

Robert E. Magnien, who supervises the state's study of the harmful microorganism, said scientists have consistently found it, apparently in a dormant stage, in Middle River since they began looking in 1999.

That summer, fish with the bloody sores associated with Pfiesteria turned up in the river, one of the Baltimore area's most popular boating and fishing spots.

The bay region has been on guard for Pfiesteria since 1997, when the first known outbreak killed fish and sickened people on three Eastern Shore waterways.

There has not been a major outbreak in Maryland since then. Water samples from dozens of bay sites have turned up signs of apparently dormant Pfiesteria, but it rarely appears over and over again in the same place.

Middle River is the exception -- "our problem child," Magnien said during an annual meeting of Pfiesteria scientists in Baltimore yesterday.

There have been no reports of people getting sick from Pfiesteria on the river, but the organism is widespread there.

"Almost every sample we took in Middle River [in 2000 and 2001] came back positive for Pfiesteria," Magnien said. "It is just loaded with Pfiesteria in the sediments, unlike any other system in Chesapeake Bay."

The toxic dinoflagellate has a complicated life history, with the ability to change among some 28 known forms. Scientists believe it can linger in bottom sediments, dormant for years, before being triggered by a combination of environmental conditions to change into a toxic form.

In dry conditions, spring and summer algae blooms can form in the rivers and stay there for weeks, instead of being washed into the bay. The algae provide Pfiesteria with food and attract schools of menhaden, the favorite prey for the organism's toxic form.

Most scientists believe the meeting of algae blooms and menhaden in warm, brackish, slow-moving water creates the right conditions for Pfiesteria to attack fish.

Scientists think that's what happened on Middle River in 1999. At the time, there were no known fish kills on the waterway. "But we subsequently found out some people had reported small fish kills in Middle River a few weeks before," Magnien said.

"We think it was just missed -- just by a little bit," said North Carolina scientist JoAnn Burkholder, Pfiesteria's co-discoverer.

The 1999 Pfiesteria bloom covered a large area and left a "reservoir" of cells in the river's sediments, Magnien said.

Burkholder said DNR biologists may soon have a sure way to know when Pfiesteria is in its toxic state. Right now, the only tests for the organism can't tell when it's harmless and when it poses a danger to people.

That leaves state officials with a troublesome problem: They have no reliable way to know when a waterway is unsafe and should be declared off-limits. Fish kills, or large schools of injured, distressed fish, are the major warning signs, but they can have other causes.

For years, scientists have been trying to develop a test for Pfiesteria's toxic stage. The technology is ready, but researchers need large amounts of toxin from the organism -- and the volatile substance has been hard to get.

But Burkholder said scientists from the National Oceanic and Atmospheric Administration working on the test have produced nearly 700 gallons of toxin.

Barring unexpected problems, researchers are "months, maybe weeks" from developing the test, said Howard Glasgow Jr., one of Burkholder's co-workers.

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