Summary1. Increased need for water and projected declines in precipitation due to climate change could leave waterways increasingly dominated by wastewater effluent. Understanding how components of wastewater influence fish populations is necessary for effective conservation and management. Despite research demonstrating effects of oestrogens, such as 17a-ethynylestradiol (EE2), on fish physiology and population failure, the generality of population responses is uncertain and the underlying mechanisms affecting population declines are unknown. EE2 is the steroid oestrogen in human contraceptive pills and has been measured up to 11 ng L À1 in the environment. 2.We identify disrupted population dynamics due to direct and transgenerational effects on survival and fecundity. We conducted a year-long study on three generations of fathead minnows Pimephales promelas Rafinesque in aquatic mesocosms and laboratory aquaria. We added environmentally relevant concentrations of EE2 daily using a static renewal, which approximates a pulsed exposure that fish experience in natural systems. 3. EE2 (3Á2 ng L À1 ) reduced F0 male survival to 17% (48% lower than controls) and juvenile production by 40% compared to controls. F1 fish continuously exposed to EE2 failed to reproduce, and reproduction of the F1 transferred to clean water was 70-99% less than controls. 4. F2 larval survival, exposed only as germ cells in their parents, was reduced by 51-97% compared to controls. The indirect effect on F2 survival suggests the possibility of transgenerational effects of EE2. 5. Synthesis and applications. Our results suggest that fish populations exposed to environmentally relevant 17a-ethynylestradiol (EE2) concentrations may not recover from exposure. Management of short-lived highly fecund fishes should be prioritized to protect fish from the embryo through gonadal differentiation. Reducing effluent will not be possible in many situations; hence, conservation of breeding and rearing habitat in unpolluted tributaries or reaches is needed. Additionally, resource managers could enhance habitat connectivity in rivers to facilitate immigration. Finally, investment in advanced wastewater processing technology should improve removal of bioactive chemicals such as EE2. Our results provide a baseline for regulatory agencies to consider when assessing the ecological effects of environmental oestrogens, and our approach to evaluating population-level effects could be widely applied to other contaminants.

The widespread occurrence of natural and synthetic organic chemicals in surface waters can cause ecological risks and human health concerns. This study measured a suite of contaminants of emerging concern (CECs) in water samples collected by the U.S. Environmental Protection Agency Region 8 around the Denver, Colorado, metropolitan area. The results showed that 109 of 144 analyzed pharmaceutical compounds, 42 of 55 analyzed waste-indicator compounds (e.g., flame retardants, hormones, and personal care products), and 39 of 72 analyzed pesticides were detected in the water samples collected monthly between April and November in both 2014 and 2015. Pharmaceutical compounds were most abundant in the surface waters and their median concentrations were measured up to a few hundred nanograms per liter. The CEC concentrations varied depending on sampling locations and seasons. The primary source of CECs was speculated to be wastewater effluent. The CEC concentrations were correlated to streamflow volume and showed significant seasonal effects. The CECs were less persistent during spring runoff season compared with baseflow season at most sampling sites. These results are useful for providing baseline data for surface CEC monitoring and assessing the environmental risks and potential human exposure to CECs.

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Rivers in the arid Western United States face increasing influences from anthropogenic contaminants due to population growth, urbanization, and drought. To better understand and more effectively track the impacts of these contaminants, biologically-based monitoring tools are increasingly being used to complement routine chemical monitoring. This study was initiated to assess the ability of both targeted and untargeted biologically-based monitoring tools to discriminate impacts of two adjacent wastewater treatment plants (WWTPs) on Colorado's South Platte River. A cell-based estrogen assay (in vitro, targeted) determined that water samples collected downstream of the larger of the two WWTPs displayed considerable estrogenic activity in its two separate effluent streams. Hepatic vitellogenin mRNA expression (in vivo, targeted) and NMR-based metabolomic analyses (in vivo, untargeted) from caged male fathead minnows also suggested estrogenic activity downstream of the larger WWTP, but detected significant differences in responses from its two effluent streams. The metabolomic results suggested that these differences were associated with oxidative stress levels. Finally, partial least squares regression was used to explore linkages between the metabolomics responses and the chemical contaminants that were detected at the sites. This analysis, along with univariate statistical approaches, identified significant covariance between the biological endpoints and estrone concentrations, suggesting the importance of this contaminant and recommending increased focus on its presence in the environment. These results underscore the benefits of a combined targeted and untargeted biologically-based monitoring strategy when used alongside contaminant monitoring to more effectively assess ecological impacts of exposures to complex mixtures in surface waters.