| Human populations, globally, discharge wastewater treatment plant (WWTP) effluents into surface waters. Surface waters that receive these effluents have detectable levels of steroidal and non-steroidal endocrine active compounds (EACs) of synthetic and biogenic origin. These molecules interact directly with signaling systems in downstream organisms and can disrupt the regulation of reproduction and development.; The city of Boulder discharges its treated WWTP effluents into Boulder Creek. Stream flow below the WWTP outflow is dominated by WWTP effluent for most of the year. This effluent contains detectable levels of biogenic steroidal estrogens (17beta-estradiol, estone, and estriol), synthetic steroidal estrogens (17alpha-ethinylestradiol), and synthetic non-steroidal estrogens (e.g., alkylphenol surfactants). I conducted field and laboratory investigations to determine the impact of this endocrine-active WWTP effluent on the reproductive potential of fishes.; Free-living white suckers (Catostomus commersoni) were collected by electroshocking in Fall 2003 and Spring 2004 from below the WWTP effluent and from upstream reference sites. White suckers below the WWTP outfall showed evidence of reproductive disruption consistent with exposure to exogenous endocrine-active chemicals at all examined loci. Gonadal intersex was identified in 20% of downstream white suckers but not in reference white suckers. The sex ratio was skewed in favor of females at effluent sites, with males half as abundant than at reference sites. Downstream male white suckers had decreased testicular sperm abundance and significantly elevated plasma vitellogenin. Downstream females had smaller ovary to body mass ratios and an asynchronous pattern of ovarian follicular development.; To determine whether this reproductive disruption was attributable to endocrine-active wastewater contaminants, I exposed adult male fathead minnows (Pimephales promelas) to either Boulder Creek water (Reference), 100% Effluent, or a 50/50 mixture of Reference and 100% Effluent (50% Effluent). Fish were maintained under stimulatory environmental conditions for 4, 7, 14, and 28 days on-site within a mobile flow-through exposure laboratory. Adult male fathead minnow primary and secondary sex characters were rapidly demasculinized upon exposure to 50%- and 100%-effluent. Within 14-days of exposure, males exposed to 50%- and 100%-effluent had significantly fewer and less prominent nuptial tubercles, significantly less prominent dorsal fat pads, and decreased abundance of sperm within the testes. Vitellogenin was maximally elevated in both 50%- and 100%-effluent treatments within 7 days. The steroidal estrogens 17beta-estradiol, 17alpha-ethinylestradiol, and estrogenic alkylphenols have been detected within the effluent treatment and not in the reference treatment. These results are consistent with the hypothesis that the reproductive disruption observed is likely due to endocrine-active wastewater contaminants. |
