Ontario lake minnow population collapsed after synthetic estrogen experiment

A tiny concentration of a synthetic hormone was enough to trigger a dramatic ecological change in a remote Ontario lake. In 2001, scientists began adding the synthetic estrogen 17α-ethynylestradiol (EE2) to Lake 260 in northwestern Ontario, maintaining concentrations of about 5 to 6 nanograms per litre. The experiment continued for seven years, including three years of estrogen additions and two years of observations after they stopped. The results, published in the Proceedings of the National Academy of Sciences (PNAS) in 2007, showed that chronic exposure disrupted reproduction in fathead minnows and eventually brought the species near extinction in the lake. The study, Collapse of a fish population after exposure to a synthetic estrogen, was led by Karen A. Kidd and colleagues.A controlled lake experimentThe experiment was conducted at the Experimental Lakes Area (ELA), a network of freshwater lakes used for ecological research.