New research is proving what scientists long suspected: that the toxic microorganism Pfiesteria piscicida lives in many Maryland rivers and streams, even though it doesn't always kill fish or make people sick.
Pfiesteria expert Dr. JoAnn Burkholder has found the dangerous dinoflagellates in samples taken from the bottom muck of five Maryland waterways, including two where it had not been found before. One of those waterways, the St. Martin River, flows into the state's coastal bays west of Ocean City.
It was the first time the toxic microorganism had turned up in a river that flows toward the Atlantic Coast tourist mecca, though it has not caused any known fish kills or human illnesses there, said David Goshorn of the Maryland Department of Natural Resources.
"We have suspected all along that Pfiesteria is pretty widespread," Goshorn said, "and what she has done is to confirm our suspicion."
A spokesman for the Maryland Coastal Bays Program said the finding of Pfiesteria cells in local waters was "not surprising, but it is worrisome at the very least."
"My guess is that Pfiesteria being there, as long as it isn't toxic in the real world, is not that harmful," said Dave Wilson Jr., a spokesman for the coastal bays conservation effort. " Hopefully, people will understand that Pfiesteria is not running rampant in the coastal bays, but it does have the potential to do so."
The aquatic organism has been found in coastal waters from New Jersey to Georgia, but it causes fish kills or human illnesses only when conditions are just right or just wrong, Burkholder said.
Pfiesteria "is probably all over the bay," said Burkholder, who presented preliminary findings to Maryland officials at a two-day scientific meeting of Pfiesteria experts near Baltimore-Washington International Airport yesterday. "It's just that most of the time it's going to be pretty benign."
Weather as a factor
Experts say Pfiesteria seems most likely to multiply, attack fish and sicken people in warm, shallow, still waters that are a mix of fresh and salt, are rich in nutrients -- like the pollutants that come from human sewage, animal manure or farm fertilizer -- and also rich in fish, especially oily fish like menhaden. Weather also plays a role, but scientists aren't certain what it is.
Maryland experts think unusual weather patterns, combined with high nutrient levels, helped trigger significant Pfiesteria outbreaks in the Pocomoke River and two other Eastern Shore waterways in 1997. The three waterways were closed, and 13 people were diagnosed with memory loss and confusion after being on the water during the outbreaks.
Researchers think a different set of weather quirks helped limit Pfiesteria to three small incidents last year, none of which killed fish or caused confirmed cases of human illness.
A spokesman for Gov. Parris N. Glendening, who pushed for controversial controls on farm runoff after the 1997 incidents, said Burkholder's latest findings show that action was justified.
"What they point to is that this is not a one-time phenomenon," said Ray Feldmann of the governor's office. "We cannot take a bury-our-heads-in-the-sand approach to the phenomenon we saw in the summer of 1997. We still need to be concerned about this.
"We're encouraged that we've got a plan in place that has the potential for helping to hold off future outbreaks."
Burkholder, a North Carolina State University researcher who helped discover Pfiesteria in the late 1980s, said Maryland waters do not seem to be as prone to toxic outbreaks as the waters of North Carolina, which has experienced 88 Pfiesteria-related fish kills in the past eight years.
The latest finding "tells me that Chesapeake Bay is not ideal for toxic Pfiesteria, but you have the potential to go a lot more toxic unless you take appropriate precautions," Burkholder said. "Do you want to be a center for toxic outbreaks, or do you not?"
The preliminary results are part of a study for the DNR, which is trying to map the extent of Pfiesteria in Maryland waters.
In October and November, when the dinoflagellate is usually burrowed into bottom mud, DNR workers took 100 sediment samples from 12 rivers. They were the Patuxent and Potomac on the Western Shore; the Chester, Choptank, Chicamacomico, Nanticoke, Wicomico, Manokin, Big Annemessex and Pocomoke, all flowing into the Chesapeake Bay on the Eastern Shore; and the St. Martin, which flows into Assawoman Bay near Ocean City, and Trappe Creek, which enters Chincoteague Bay near Assateague Island National Seashore.
In the first 30 samples, Burkholder found Pfiesteria piscicida in concentrations high enough to kill fish in the Big Annemessex, Chicamacomico, Pocomoke and St. Martin. She found the same organism on the Wicomico, but the cells did not kill fish in her laboratory. In Trappe Creek, she found a dinoflagellate that did not kill fish and has not been identified.
Burkholder and other experts stressed that there have been no recent fish kills or signs that people have gotten sick at the sites where DNR workers took the Pfiesteria-infested samples in October and November.
The Patuxent, Potomac, Chester and Choptank turned up no traces of Pfiesteria, but Burkholder said she has about 70 more sediment samples waiting to be analyzed, and expects to find signs of the microorganism in at least some of them.
Rhode River discovery
Another marine scientist discovered Pfiesteria almost by accident in the Rhode River south of Annapolis this fall.
Park Roblee of the University of North Carolina has developed a test that can spot Pfiesteria in the water, but he cannot tell whether the organism is in its toxic stage. He told scientists at this week's meeting that he got samples from the Rhode River expecting them to be Pfiesteria-free, but to his surprise they came up positive. Again, there were no signs of a fish kill in the area.
Roblee said workers from his laboratory traveled the coast from New Jersey to Florida, taking water samples "basically wherever I-95 crossed a river or stream that flowed into an estuary." The samples showed signs of Pfiesteria at eight out of 100 sites, he said.
In other findings reported yesterday, University of Maryland researcher David Oldach said no signs of serious illness were found in 1998, the first year of a five-year study of people who might come in contact with Pfiesteria. Oldach said 90 Eastern Shore watermen and 25 people who don't work near the water have volunteered for the study and undergone testing.
Pub Date: 2/25/99