AQUA seminar: The birth control pill in municipal wastewaters: a whole lake experiment to understand its effects on aquatic food webs
Karen Kidd, Canadian Rivers Institute & Biology Department, University of New Brunswick, Saint John, New Brunswick, Canada
Municipal effluents discharged into rivers contain substances like the synthetic estrogen used in the birth control pill. Male fish living in these waters become feminized and produce eggs in the more severe cases. This feminization of male fish is common in rivers in heavily populated areas of Canada, the U.S. and Europe, but it was not known if it threatens the sustainability of fish populations. A whole lake experiment was done at the Experimental Lakes Area (ELA) in northwestern Ontario, Canada, from 1999-2010 to understand how the estrogen in the birth control pill affects reproduction and numbers of fish and other organisms in the food web. The experiment showed that very low levels of estrogen added to the lake water for 3 years caused the feminization of male fish and the near extinction of a fish species from the lake. When the additions of the estrogen stopped, mimicking improved treatment of municipal wastewaters, the fish recovered completely. However, the declines in fish resulted in indirect effects on other trophic levels including a decline in the lake’s top predator, lake trout, through a loss in their food supply, and an increase in several invertebrate taxa likely due to reduced predation pressure. Reducing inputs of estrogens to freshwaters is needed given their potent effects on fish and their ability to affect the sustainability of fish populations, and their potential to indirectly affect other food web organisms.