Scientists identify second deadly Pfiesteria species

A microscopic view of Pfiesteria, a toxic microbe, in its zoospore stage.

By Environmental News Network staff

March 22, 2000
Web posted at: 11:47 a.m. EST (1647 GMT)

Researchers have identified a second species of Pfiesteria, a toxic microbe responsible for killing millions of fish from Chesapeake Bay to the Gulf of Mexico.

"For membership in the toxic Pfiesteria complex, they have to look like Pfiesteria, they have to act like Pfiesteria," said JoAnn Burkholder, a marine scientist at North Carolina State University. "They also have to be capable of producing toxins that cause fish disease and death."

The second member of the complex, dubbed Pfiesteria shumwayae, was first detected during a 1995 fish kill in North Carolina's New River estuary, following a major spill of effluent from a hog-waste lagoon. Several years of testing confirmed that the organism is toxic.

Researchers have identified several other Pfiesteria look-alike organisms, but P. shumwayae is the first Pfiesteria-like organism to be able to attack and kill fish. Burkholder co-discovered P. piscicida in 1989.

"Look-alikes don't mean anything, they are benign species," she said. "There are only a couple that trigger toxins in the presence of fish." Burkholder believes that other Pfiesteria-like species will be found as the ability to detect the organisms grows.

Pollution runoff from farms, especially animal feedlots, is routinely cited as a source of Pfiesteria outbreaks.

Pfiesteria attacks fish and causes lesions on their flesh. The microbe is generally found in closed river systems that do not have the same flushing action as large bodies of water. In such stagnant systems, the organism thrives on high concentrations of nitrogen and phosphorus from various sources of pollution.

The more scientists learn about Pfiesteria, the more insistent they are that the issue of water degradation be addressed.

Pollution runoff from farms, especially concentrated animal feedlots, is routinely cited as a source of Pfiesteria outbreaks. According to anthropologists at the University of Maryland, farmers resent being labeled as polluters and many view themselves as environmentalists.

"These farmers and environmentalists talk the same talk. They are equally passionate about protecting the environment," said Michael Paolisso, one of the anthropologists. "Neither one wants to see the water or the land polluted."

Burkholder supports the call for an alliance between industry, government and the environmental community to fight pollution. Besides, she said, the source of Pfiesteria outbreaks is watershed-specific, and human sewage is as much of a problem as is farm pollution.

"We need to do more to curb both point and non-point pollution," she said. "Pfiesteria is just one sign of us not doing things well enough. The more we do to protect water, the better it will be."

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JoAnn Burkholder
Michael Paolisso
The Environmental Protection Agency's information on Pfiesteria
North Carolina State University

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