When biologists cut open male fish pulled from Pennsylvania’s waterways, they found substances that belong in female fish — egg cells and a protein present in egg yolks.
According to a recent U.S. Geological Survey study published in mid-June, scientists found male fish with signs of female development in the Ohio, Susquehanna and Delaware river basins, most severely in the Susquehanna.
In the Susquehanna, with its many farms, dairies and poultry operations, they found more of the hormones likely to cause intersex smallmouth bass than in the less agricultural Ohio and Delaware.
The researchers, which included the state Department of Environmental Protection and the Fish and Boat Commission, sampled smallmouth bass, white sucker and redhorse sucker out of the three basins in 2007 and 2008. They were searching for signs of exposure to estrogen-like chemicals that can disrupt endocrine systems.
Endocrine disruptors interfere with the body’s hormonal systems, causing developmental, reproductive, neurological and immune changes, according to the National Institutes of Health. The term describes natural and man-made chemicals, including hormones, pharmaceuticals, pesticides and plastic additives.
All of these molecules are considered contaminants of emerging concern, with little regulation and or regular monitoring, the paper states. They pose a challenge to water quality researchers all over the world, and the U.S. Environmental Protection Agency is looking into how to study and control them.
Researchers chose smallmouth bass and white sucker because of their sensitivity to endocrine disruptors, USGS fish biologist Vicki Blazer, Ph.D., said. Blazer was the paper’s lead author.
Blazer and her team found testicular oocytes, or egg cells, where sperm cells should be, in male smallmouth bass. These were most prevalent and severe in the Susquehanna.
In all three basins, they found male bass with vitellogenin, a precursor protein to egg yolks, in their blood plasma.
They found no testicular oocytes in male white sucker or redhorse sucker. Some white sucker males had vitellogenin; red sucker males had none.
The researchers put forth some evidence that the hormone estrone, which they suspect could be causing intersex fish, largely comes from animal waste.
Among the three river basins, researchers found that the more agricultural Susquehanna had a higher rate and severity of eggs and vitellogenin in male bass.
Estrone is common in wastewater treatment plant effluent and runoff from cattle, chicken and swine manure, as well as fish hatcheries. Other estrogen hormones also break down into estrone, the paper states.
Over the past 60 years, livestock and poultry production in the U.S. has more than doubled, but the number of farms has decreased by 80 percent, according to a 2013 EPA paper on manure contaminants.
This means the industry is becoming more and more concentrated. Manure flows into surface waters via rain runoff, spills, storage lagoon and equipment failure and poor manure application practices, the EPA stated.
Past research on manure in surface waters has mostly focused on nitrogen and phosphorus nutrients. Researchers have only recently shifted to hormones, in part because of new laboratory techniques that can detect them at miniscule concentrations.
Estrogen hormones estrone, estradiol and estriol are common constituents of diluted dairy manure, according to a 2006 paper in Journal of Environmental Quality by dairy researchers at the University of Florida. They can disrupt the reproductive systems of fish, reptiles and amphibians at levels as low as 10 to 100 parts per trillion.
Out of the five hormones measured in water and seven hormones and plant sterols measured at fish sampling sites in Pennsylvania, USGS researchers found estrone most often. They found it in water at all of the Delaware and all but one of the Susquehanna sampling sites and in the sediment at nearly every site in the three basins.
The highest concentration in water was a little less than 3 parts per trillion. Sediment concentrations were higher — almost three parts per billion.
In 2010, researchers went back to the Juniata River in the Susquehanna basin and the Allegheny River in the Ohio, sampling for pesticides, flame retardants and hormones, using a passive sampler to catch molecules floating downstream.
Unlike the natural hormones, pesticides were found in greater concentrations in the Juniata than in the Allegheny.
As a result of the smallmouth bass problems documented in the study, the DEP now conducts sampling in state waterways for a broad array of emerging contaminants, spokeswoman Lisa Kasianowitz said in an email.
Samples collected in 2013 show no definitive patterns, Kasianowitz said, but the agency is still evaluating them. Sampling will continue this summer, and results should be available this winter, she said.
“DEP’s plan is to continue the sampling until we have an understanding of how these compounds may or may not impact the aquatic life in all streams and rivers,” Kasianowitz said.