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Two Old Dominion University biologists have waded back into the turbulent waters of the pfiesteria debate.

This microscopic single-celled algae was blamed for fish kills along the East Coast during the 1990s, and two of its most persistent accusers have been Andrew S. Gordon, professor of biological sciences, and Harold G. Marshall, Morgan Professor Emeritus of biological sciences.

They, together with lead researcher JoAnn M. Burkholder of North Carolina State University, and 10 other scientists, published a new indictment of pfiesteria on Feb. 14 in the online Proceedings of the National Academy of Sciences. The findings show that if the right study methods are used and if appropriate strains of pfiesteria are analyzed, the algae will be found guilty of fish predation. In other words, the single-celled algae can produce toxins that will kill fish and harm humans.

But another set of scientists, which had offered previous evidence contradicting the findings of the Burkholder team, published a study last month that raised the stakes of the conflict. This latest study by scientists from George Mason University and the University of Maryland finds no direct correlation between the pfiesteria and fish death. The study was done with funding from the Environmental Protection Agency.

A GMU scientist said in a news release that the techniques of researchers on the other side of the conflict had been indefensible: "Experiments to investigate the Pfiesteria toxicity were set up in fish tanks full of other contaminating organisms. Clearly, it was not rigorous science." Another scientist involved in the GMU/Maryland study suggested that biology textbooks and other literature that set forth pfiesteria toxicity must be rewritten. "Scientists have an obligation to clarify the literature when what they publish is incorrect. Otherwise, a disservice is done to all of science," he said.

Neither ODU's Gordon and Marshall, nor N.C. State's Burkholder, were as contentious in statements supporting their research.

Gordon said criticism of pfiesteria toxicity findings seems directed at early research, and not at the Burkholder team's latest study. He also said he hoped the controversy does not have unwanted implications for clean water legislation that may be needed to prevent more pfiesteria poisoning.

Gordon asserted that lack of fish death in competing research does not necessarily mean pfiesteria toxin is not present. "Unless the water was tested to see if (the) toxin was present, all that can be said from such a study is that there wasn't enough toxin present to cause the fish to die," Gordon said.

Explained Burkholder, who is director of the Center for Applied Aquatic Ecology at N.C. State: "If a person drinks a glass of water from a well that sometimes contains arsenic, and the person doesn't suddenly become very sick or die, would it be correct to say that the water didn't contain any arsenic? Surely not."
The Burkholder team's study demonstrates for the first time the presence of toxin in pfiesteria cultures that are free of contamination from bacteria or fungi, and this counters criticism of the GMU/Maryland scientists.

However, as Marshall explained, "When bacteria were present, pfiesteria made more toxin, and a lot more toxin was produced when the toxic strains were given live fish."

The Burkholder-team study reaffirmed that some strains of the two known pfiesteria species are toxic, including a strain used by other researchers who had asserted that pfiesteria could not produce toxin. It also showed that toxin from pfiesteria can cause fish disease and death without pfiesteria cells having to be present.

A kill of more than 1 billion Atlantic menhaden in North Carolina's Pamlico River estuary in 1991 led to Pfiesteria research that was begun at N.C. State and joined in 1997 by Gordon and Marshall. The two ODU scientists have identified at least 19 algal species in the Chesapeake Bay that can produce toxins and are potentially threatening to regional fish and shellfish populations.

Pfiesteria can be amoebae and cysts at different stages in a complicated life cycle, and the cycle itself can be a factor in toxicity, according to the findings of the Burkholder team.

Gordon was second author of the latest paper, whose co-authors are from four universities, the National Oceanographic and Atmospheric Administration-National Ocean Service and the South Carolina Department of Natural Resources.

This article was posted on: February 16, 2005

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