We were so pleased to receive this guest post by Geoffrey Giller, who is a Master’s of Environmental Science candidate, 2013, at the Yale School of Forestry and Environmental Sciences. At Frogs Are Green, we have explored the issue of endocrine disruptors and their possible effects on frogs, as well as on humans. We look forward to learning the results of his research.
Geoff Giller readying nets for sampling at a golf course (Photo credit: Susan Bolden)
Frogs are threatened globally by a host of stressors, from habitat loss to climate change to infectious diseases. One threat receiving increased scientific attention is endocrine-disrupting chemicals (EDCs). These chemicals interfere with normal hormonal function. In 2002, Dr. Tyrone Hayes published a paper in Nature detailing the feminizing effects of the widely-used pesticide atrazine on male African clawed frogs. Since then, there has been increasing research showing similar effects of other EDCs on frogs and fish. There is also more and more evidence that endocrine disruptors are widely prevalent pollutants in the water bodies of the United States.
As a Master’s student at Yale’s School of Forestry and Environmental Studies, I want to further investigate the presence and effects of these EDCs. My advisor, Dr. David Skelly, recently published a paper showing that green frog hermaphrodites are most prevalent in suburban areas. While most research since Dr. Hayes’ paper has focused on agricultural areas, Dr. Skelly’s work indicated that there may be a significant source of EDCs causing these high rates of hermaphroditism (as demonstrated by the presence of egg cells in the gonads of male green frogs) in suburban areas.
Testicular oocytes (egg cells in male gonads) from Skelly et al. 2010
This topic has implications both for frog conservation, as such sexual deformities likely inhibit frogs’ abilities to reproduce, and for human health, since suburban areas are much more densely populated than agricultural ones. But while the presence of these deformities has been confirmed, their cause has not. Dr. Skelly has hypothesized that the cause may be certain EDCs called synthetic estrogenic compounds; these chemicals are found in medications such as birth control pills as well as in some cosmetic products. The source of these chemicals would likely be septic tanks that leach chemicals into the groundwater; this contaminated groundwater then flows into nearby ponds, streams, and wetlands where frogs breed and live.
I am working with my fellow Master’s student, Max Lambert, to identify exactly what chemicals are present in the groundwater and pond water in suburban areas and what effect these chemicals are having on frogs. In collaboration with scientists at USGS, we will be installing sampling devices at 9 suburban sites, as well as three agricultural and three forested sites as comparisons. We will sample the groundwater and the pond water for a large range of chemicals including medications, synthetic estrogens, pesticides, and a host of other man-made compounds. This study will provide a list of the chemicals that may be responsible for the deformities in the frogs that we are observing.
Max Lambert with a peeper (Photo credit: Hannah Erin Bement)
In addition to the water testing, we will be surveying three types of frogs—American toads, gray tree frogs, and pickerel frogs—for similar sexual deformities. By combining the data from our water testing with the rates of deformities in frogs at these same ponds, we will be able to say which chemicals are likely causing deformities, and which are not. This information will be crucial for the future regulation of these chemicals.
The main stumbling block of this project is the cost. EDCs can have significant biological effects when present at very low concentrations; however, doing water testing for such low concentrations of chemicals requires highly specialized equipment. While some of our costs are covered by our collaboration with USGS, we still need to raise some funds. For more information on our project, and for a chance to help us out with this research, please go here: http://www.petridish.org/projects/estrogens-in-your-backyard-the-chemical-ecology-of-suburbia. This website allows researchers to raise necessary resources through “crowdfunding,” or multiple small donations from a large number of people. We are close to our target funding amount, but could use a little more help. Take a look at our page (as well as the various rewards for different donation amounts), and we would be incredibly grateful for your support!