CORVALLIS - After the first year of a two-year study, Oregon State University scientists have found about three times as many juvenile minnows with backbone deformities in the Newberg Pool of the Willamette River than at a site 80 miles upstream near Corvallis.
Larry R. Curtis, an OSU professor of environmental toxicology, will present preliminary results of a Oregon Watershed Enhancement Board-funded study on pike minnow fish deformities in the Willamette River to the Oregon Legislative Emergency Board in Salem this Thursday (Jan. 9).
For years, the Newberg Pool of the Willamette, just south of Portland, has been a notorious place for finding a high percentage of young fish with skeletal deformities.
"There's significant public concern over deformed fish in the Newberg Pool of the Willamette River, but little scientific basis for explaining the deformities," said Curtis, head of the OSU Department of Environmental and Molecular Toxicology. "These fish are sentinels for environmental contamination. People want to know what's causing the deformities and whether they have any implications for human health."
As the lead investigator of OSU's interdisciplinary study of the Willamette River and its deformed fish, Curtis has gathered together OSU's Agricultural Experiment Station toxicologists, chemists, microbiologists and fisheries biologists in an effort to determine the prevalence of skeletal deformities in juvenile fish in stretches of the Willamette River near Newberg and Corvallis.
The OSU researchers also are trying to determine what causes these deformities. They are comparing the physical and chemical conditions and the accumulated toxicants in ovaries of fish from adult northern pike minnows at Corvallis and Newberg and conducting laboratory studies that might show a link between physical or chemical conditions in the river and the incidence of deformities.
OSU researchers in the Department of Fisheries and Wildlife and the Department of Microbiology have examined the deformities and found tiny parasites associated with some of the deformed fish. The suspected parasite is a microscopic myxozoan in the genus Myxobolus, a relative of the microorganism that causes whirling disease in salmon.
There are no human health threats associated with this fish parasite, said Curtis.
So far, the researchers have found most of the physical and chemical characteristics of the water at Newberg and Corvallis to be similar. Temperature, pH, dissolved oxygen and nitrate levels did not vary significantly between the two sites.
The investigators detected similar low concentrations of heavy metals cadmium, copper, lead and zinc at both sites, although they found one high zinc sample measured in the Newberg Pool. They found concentrations of persistent organic contaminants including dieldrin, DDT, DDD and DDE to be two to four times higher in Newberg Pool than Corvallis, but all detections were extremely low, below one part per trillion, said Curtis.
They haven't yet completed analyses for other chemical classes, including currently used pesticides. The researchers are now measuring persistent bioaccumulative toxicants in ovaries collected from adult pike minnows in both sites on the river. Results are not yet available.
In recent experiments, newly fertilized eggs were exposed to river water from each site for 15 to 47 days. They didn't detect any differences in development between fish reared in water from either location.
The scientists have another field season, spring through the fall of 2003, to collect data and fish and study both sites on the Willamette. They will also conduct more laboratory experiments on zebrafish with various concentrations and fractionations of toxic materials from the river water from each site. The final report will come out in 2004.