Tests to probe fish kill cause
Pfiesteria possible in Dagsboro creek
Delaware State News
July 12, 2000By Greg Layton
Associate editorDAGSBORO - The P-word is back.
For the first time since Pfiesteria piscicida was linked to fish kills on Maryland's Eastern Shore in 1996, thousands of lesion-marked fish have washed ashore in Delaware.
"This is a large fish kill," said Roy W. Williams, who monitors fish kills for the Delaware Department of Natural Resources and Environmental Control.
A Monday afternoon kill left 50,000 to 75,000 young menhaden dead on Pepper Creek, a tributary of Indian River, near Dagsboro, Mr. Williams said.
About 5 percent of the fish found were marked with lesions, similar to those associated with Pfiesteria, he added.
DNREC researchers have already determined that a larger fish kill on Rehoboth Bay - last week was not caused by Pfiesteria, Mr. Williams said.
Researchers at the University of Maryland at Baltimore, and the North Carolina State University - including Pfiesteria discoverer Dr. JoAnn Burkholder - have been sent water and tissue samples, he said.
Water samples will be examined within the next 24 hours, he said, and will allow state officials to say with some certainty whether Pfiesteria is in the Indian River and killing fish.
"If tests come back negative within the next day or so, we'll be able to say Pfiesteria didn't cause this fish kill," he said. "However, it will take weeks for Dr. Burkholder to develop cultures from the samples we sent her. So, maybe in eight weeks, we'll have to change our minds."
Pfiesteria isn't the only microorganism in the area known to cause fish kills.
About 30 microorganisms are capable of causing large numbers of fish to die, said Wolfgang von Baumgart, a spokesman for Solutions to Avoid Red Tide Inc., an environmental organization with about 200 members.
Pfiesteria, and so-called red and brown tides, are the most likely to cause kills like Monday's, he said.
Whatever microorganism caused Monday's kill, Mr. von Baumgart believes its toxic outbreak was prompted by poor water quality in the Indian River, a river which the federal Environmental Protection Agency considers "impaired" by nutrients, he said.
"We need to reduce nutrients, particularly nitrogen and phosphorous, to our waterways," he said. "There's not a definitive link between Pfiesteria and nutrient pollution, but reducing nutrients would help control other things, even nuisance algal blooms," he said.
Mr. von Baumgart said the state should use electronic devices to keep up-to-the-minute records of water quality throughout its waterways.
"I believe there's a fairly strong association between Pfiesteria and nutrients," Mr. Williams said.
Monday's fish kill may also have been caused by low dissolved oxygen levels, he added.
While researchers found dissolved oxygen levels near the surface of Pepper Creek to be nearly twice normal, a sign microorganisms are active in the water, the oxygen in water near the creek's bottom was a suffocating 0.6 parts per million, Mr. Williams said.
Fish cannot survive without dissolved oxygen, which is taken from the water by feeding microorganisms. Microorganisms thrive in nutrient-rich water.
The state has tested the water to determine if nutrients played a role in Monday's fish kill, Mr. Williams said. Results are not yet available.
State researchers used nets to collect marine animals, including menhaden, spot, weak fish, anchovies and blue crabs, near Pepper Creek Tuesday morning, he said.
Among the nearly 200 fish caught, only two had healing scars that may have been the result of lesions, he said. All of the fish caught were alive and healthy.
Meanwhile, the state Department of Public Health is asking people to be safe in the water near Pepper Creek.
State Epidemiologist Leroy Hathcart said his department is asking people to avoid contact with the creek's water.
Pfiesteria, he said, has been shown to cause lesions on humans who come into contact with water tainted by its toxin.
The toxin has been shown to cause memory loss and tingling muscles in humans who have breathed air tainted by it, he added.
While the toxin has caused short-term memory loss in affected individuals for up to three months its effects appear to be only temporary, Dr. Hathcart said. There is no evidence that eating Pfiesteria-affected fish causes health problems, he said.
No one in Delaware has ever complained of Pfiesteria-related symptoms, he added.
"Right now, our message is wait and see," Mr. Williams said.