The Reproductive Effects of Municipal Wastewater Effluents
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There is a growing concern that pharmaceutical chemicals present in the effluents from municipal wastewater treatment affect marine life. Lab experiments were conducted to find out if effluents from wastewater treatment plants in the Grand River Watershed affect the reproduction of zebrafish. The experiments included whole animal reproductive performance based on the numbers of eggs spawned over an exposure period, biomarkers of reproductive function, and the expression of selected genes in the ovary. In two previous studies, a 50% dilution water collected immediately downstream of the treatment plant in Waterloo resulted in a significant reduction in the numbers of eggs spawned. In contrast, effluent collected downstream of two different treatment plants, an upstream reference site, and the laboratory control water had no effects on spawning success. Measurement of ovarian steroid hormone levels or the expression of selected genes involved in steroid hormone synthesis did not reveal site differences in the response to the different effluents. While pharmaceuticals were found in the effluents, their presence was not predictive of effects on spawning success. Rather, high concentrations of ammonia detected in the Waterloo effluent may be responsible for reproduction losses. These studies suggest that the inclusion of endpoints of whole animal performance are a more robust screen of reproductive toxicants than measurements of hormone levels or gene expression, particularly when the underlying mechanisms of reproductive impairment are unknown. These studies also show that some but not all treatment plants in the Grand River Watershed are hazardous to fish reproduction.