Norris is focusing on white suckers, a species of fish not known for exhibiting intersex characteristics under normal conditions.
"Our impression is that they are males that are being feminized [because] of the nature of the chemicals that are in the water, and most of them are estrogenic [meaning they stimulate development of female sex characteristics]," he said. "Some of [the estrogenic chemicals] are natural urinary estrogenic products from humans, and some of them are pharmaceuticalsbirth control pills."
Norris has also found large concentrations of compounds called alkylphenolscommon substances often associated with household detergents and personal-care products.
"They're the same sort of compounds that have been associated with fishes in England and Europe," he said. "The main difference here is the source is domestic sewage, as opposed to industrial sewage. This is one of the first observations, certainly in the U.S., of a domestic sewage factor alone being connected with this [intersex phenomenon]."
Indicator Species and Water Quality
As for the South Branch of the Potomac River, Norris, like the USGS team, is unsure of the source of the pollution. "It's hard to say what the specific source might be [in the South Branch]. But I think the effect is very clear, that they're getting feminization," he said.
Currently USGS scientist Blazer said, the focus has shifted to analyzing water-quality data. "The water resources division of USGS out of Charleston put what are called passive samplers at a number of the sites," she said. "Basically they accumulate contaminants what fish tissue would accumulate over time. They expect to have the analyses of those back in November. We're hoping with that and some of the other water-quality things we're doing, we'll at least begin to get an idea of what we should be looking at."
Blazer added that her team would soon be conducting its fall collection, adding largemouth bass to the mix to test against a nationwide USGS largemouth-monitoring database. "Are we seeing the same thing in largemouth bass, or is there something about smallmouth, whether it's their food habits or when they spawn, that makes them more susceptible to exposure," she said.
Blazer said fish are good indicators of subtle changes in water qualitychanges perhaps caused by the introduction of natural and synthetic hormones. Still, the exact cause of the sex-changed South Branch smallmouths remains unclear.
"Hopefully, when we get our data back, we can all sit down and really look at it and come up with some thoughts," she said.
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