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Estrogen has surprising effects on freshwater wildlife


Saint John, NB – The International Institute for Sustainable Development-Experimental Lakes Area (IISD-ELA) and the University of New Brunswick have released the findings of a study that show that the birth control pill has unexpected effects on aquatic ecosystems.

The study, entitled Direct and indirect responses of a freshwater foodweb to a potent synthetic oestrogen, was published in the most recent issue of Philosophical Transactions of the Royal Society B.

The study found that introducing synthetic estrogen, found in the birth control pill, into a lake negatively affected the reproductive cycles of fathead minnow and led to a near extinction of the population. The estrogen interfered with the minnow’s ability to reproduce.

Once minnow numbers dropped, other aquatic species responded to the loss in food supply or predation. This cascading response in the lake was unexpected and suggests the risks of estrogens in the surface waters may be underestimated.

Estrogens can enter our rivers and lakes via municipal effluents and can originate from various sources, such as urine from females and feedlots. They cause male fish to develop eggs, in the more severe cases, and feminized male fish have been found in rivers across North America.

“The results of this study are significant, as it is one of the examples of whole-ecosystem experimentation that is possible at IISD-ELA, a research facility in Northwestern Ontario, Canada that comprises 58 small lakes and their watersheds” said Michael Paterson, chief research scientist at IISD-ELA and a co-author on the study.

“Thanks to the benefits of whole lake experimentation, we were able to manipulate these small lakes and examine how all aspects of the ecosystem—from nutrients to fish populations—respond. Small-scale studies would never have revealed the true environmental impacts, such as impacts on population sizes, of estrogen in municipal waterways.”

“First we were surprised when the population of fathead minnow collapsed shortly after the whole lake study started. The minnows were very sensitive to low concentrations of this synthetic estrogen” said Karen Kidd, University of New Brunswick Saint John and the study’s lead author.

“The big drop in minnow numbers affected other aquatic life in the lake because the main food supply had disappeared for the bigger fish, and aquatic insects were no longer being eaten by the minnows. This was another surprise and suggests greater impacts of estrogen discharges to surface waters than we previously thought.”