Welcome to our blog series, Research Highlights! On the second Monday of each month, we debut newly published fisheries research by our women of fisheries colleagues. If you have research you would like to highlight and share with our readers, please contact us at women.of.fisheries@gmail.com.
Our January’s Research Highlight:
Jackson, L. and P. Klerks. 2020. Effects of the synthetic estrogen 17α-ethinylestradiol on Heterandria formosa populations: Does matrotrophy circumvent population collapse? Aquatic Toxicology 229.
As we begin a new year, many of us are eager to flush the challenges and uncertainties of 2020 down the toilet and start anew. I’m figuratively speaking, of course. As we’ve seen in the first few days of 2021, however, sometimes what we flush down the proverbial toilet doesn’t actually go away. Many things in life are like that; there really is no “away.” Much of what we and others around us do will have an impact on the world beyond our limited scope.
Dr. Latonya Jackson, an assistant professor at the University of Cincinnati, makes this point in a recently published study on the influence of contraceptives on Least Killifish Heterandria formosa. And yes, we’re still talking about flushing toilets, this time in the literal sense.
Let me take a quick detour here for those unfamiliar with Least Killifish, because it is a pretty interesting species. It is one of the smallest freshwater species in North America. I’ve seen reports of it being the smallest and others that dispute that title. Its maximum size has been reported as a whopping 3.6 cm (or about 1.4 in), so regardless of the title, it’s tiny. It is also part of the Poeciliidae family which consists of livebearers. This puts them in a club to which only 2% of fish species belong! It is native to the deep southeastern part of the United States, but due to its short generation time, high fecundity, ease to maintain in aquariums, and small size, it is commonly used in laboratory studies like this one.
Now back to our study.
Synthetic estrogen, 17α-ethinylestradiol (abbreviated EE2), is commonly used in oral contraceptives and hormone replacement therapy. Because wastewater treatment plants do not remove these types of chemicals from the water, any amount that is released by being flushed purposely or by what is released when women go to the bathroom remains in the water. This water eventually makes its way to local waterways and ultimately into the bodies of fish.
In the study recently published by Dr. Jackson and her colleague Dr. Paul Klerks, Least Killifish were exposed to 5 ng/L EE2, from newborn to seven months old. Although growth appears not to be affected, results suggested chronic exposure at this level can result in smaller numbers of fish in all life-history stages and the skewing of sex ratios towards females. With estrogen levels up to 16 times this concentration observed in waters adjacent to sewage treatment plants, there is reason for concern. What this means for wild populations of Least Killifish, however, remain unknown, although previous work suggests that short-lived species may be particularly prone to population collapse in long-term exposure situations.
Obviously fish are not the only ones reliant on clean water. Aside from ecological effects, these compounds may also find their way into some tap water supplies at sufficient levels to be of concern to human health. It is imperative to learn more about the health and environmental effects of these chemicals and engineering solutions to filter them out. In the words of Dr. Jackson, “Our drinking water is not a renewable resource. When we run out of clean drinking water, it’s gone.”
So, let’s not flush it away.
The full manuscript can be found and downloaded here:
https://doi.org/10.1016/j.aquatox.2020.105659
University of Cincinnati News Release:
https://www.uc.edu/news/articles/2020/10/uc-study-finds-fish-exposed-to-estrogen-produce-fewer-males.html