Pfiesteria return awaited in state N. Carolina fish kill raises concerns here

July 28, 1998|By Heather Dewar | Heather Dewar,SUN STAFF

While North Carolinians scrambled to cope with their first major fish kill of the year, Maryland officials wondered how much time they have before Pfiesteria piscicida reappears here. A week? All summer, or longer?

There's no way to predict Pfiesteria's behavior, said David Goshorn of the Maryland Department of Natural Resources, but most of the conditions are right for a return of the toxic microbe to the waters of the Lower Eastern Shore.

One crucial factor is lacking: abundant schools of menhaden, the oily, algae-eating fish that seem to transform Pfiesteria from a harmless algae to a toxin that can kill bay creatures and make people sick.

Thousands of menhaden turned up dead yesterday along a five-mile stretch of North Carolina's Neuse River, the place where Pfiesteria first appeared in the wild in 1992, and where fish kills have recurred almost yearly. Scientists are testing to determine whether Pfiesteria was to blame.

"The majority of the fish have Pfiesteria-like sores," Don Reuter, a spokesman for the North Carolina Department of the Environment and Natural Resources, told the Associated Press. "It's the first big fish kill of the summer."

The waters of Maryland's Pocomoke River remain surprisingly free of fish with the bloody lesions that were common in the fall of 1996 and spring of 1997. Maryland's first big fish kill occurred Aug. 6.

Scientists are busy weighing this year's data against what little is known about Pfiesteria and trying to figure out what to expect.

"We've been sampling the daylights out of both the fish and the water quality," Goshorn said.

Between early June and July 15, DNR workers caught 10,680 fish in the Pocomoke and found 52 with abnormalities -- well below 1 percent, a rate considered normal in wild fish, said agency spokesman John Surrick.

Others are seeing the same pattern. The University of Maryland Eastern Shore sampled commercial catches and found fewer than 1 percent with problems, Surrick said.

Observers for the Chesapeake Bay Foundation are tallying fish caught in Pocomoke River bank traps. Fish in the netted enclosures are particularly vulnerable to Pfiesteria because they can't swim away from it, experts say. But even there, the environmental group is finding "a much lower level of fish with problems, about 3 [percent] or 4 percent," compared to 43 percent at this time last year, said Bay Foundation Vice President Michael Shultz.

"We're not seeing anything like we saw last year, nothing at all," said Shelltown fisherman Fred Maddox, whose family was the first to report outbreaks of lesioned fish last year. "I don't think anybody really knows what the story is."

Ecologist Donald Boesch, director of the University of Maryland's Center for Environmental Science, agreed that scientists know only the broadest outlines of Pfiesteria's behavior. "The more we learn about this, the more we realize the only thing you can predict is that something unexpected will happen," he said.

Based on research in North Carolina, experts think Pfiesteria is probably always present in some waterways, and only becomes harmful under certain conditions. Goshorn said those conditions include water temperatures of about 77 degrees or higher; brackish waters containing about six parts per thousand of salt, or about one-fifth the salt in seawater; high levels of nutrients such as nitrogen and phosphorus; stagnant conditions that concentrate nutrients; and plenty of fish like menhaden, which feed on algae and secrete oily chemicals that apparently trigger lethal changes in Pfiesteria.

Goshorn said that on July 16, when DNR workers last checked the Pocomoke, conditions there nearly matched the profile for Pfiesteria outbreaks. The water was warm and brackish enough and the tidal patterns were the same as the year before. While results of July's nutrient tests were not complete, earlier samples showed the amounts of nitrogen and phosphorus were about the same this year as last year.

"The last piece of the puzzle, of course, is the fish," Goshorn said. "The menhaden are just now starting to school up."

Other factors in Pfiesteria's life cycle are still unknown, other subtle differences in weather that might affect its behavior. Most experts agree with Shultz that no reason exists to expect the current respite to hold.

"Even if we don't see Pfiesteria come back this year, the rivers are still polluted with nutrients," Shultz said. "There haven't been any really broad changes. If our experience is like North Carolina's, we can expect it to be back -- if not this year, then next year."

Pub Date: 7/28/98

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