Temperature modulates estrone degradation and biological effects of exposure in fathead minnows.

Environmental pollutants, including estrogens, are widespread in aquatic environments frequently as a result of treated wastewater effluent discharged. Exposure to estrogens has been correlated with disruption of the normal physiological and reproductive function in aquatic organisms, which could impair the sustainability of exposed populations. However, assessing the effects of estrogen exposure on individuals is complicated by the fact that rates of chemical uptake and environmental degradation are temperature dependent. Because annual temperature regimes often coincide with critical periods of biological activity, temperature-dependent changes in estrogen degradation efficacy during wastewater treatment could modulate biological effects. We examined the interactions between ambient water temperature and degradation of estrone (E1) during wastewater treatment. In addition, we exposed mature fathead minnows (Pimephales promelas) to three environmentally relevant concentrations of E1 at four different water temperatures (15°C, 18°C, 21°C, and 24°C) to reflect natural seasonal variation. E1 degradation occurred with and without the support of robust nitrification at all temperatures; however, the onset of E1 degradation was delayed at cooler water temperatures. In addition, we observed significant interactive effects between temperature and E1 exposure. Female morphometric endpoints were more susceptible to temperature-modulating effects while physiological endpoints were more strongly affected in males. Collectively, the data demonstrate that natural seasonal fluctuations in temperature are sufficient to affect E1 degradation during wastewater treatment and induce sex-dependent physiological and anatomical changes in exposed fish.