SOMLEY, B.L.*; HORTIN, S.M.; PROPPER, C.R.; Bates College: The Effect of Reclaimed Wastewater on Western Mosquitofish (Gambusia affinis) Survivorship

This study investigated the endocrine disrupting potential of reclaimed wastewater. We hypothesized that the wastewater treatment process may not have sufficiently removed all androgenic xenobiotics. Female western mosquitofish (Gambusia affinis) were utilized as bioindicators because they develop elongated anal fins upon exposure to androgens. The Gambusia were treated with conditioned reverse osmosis water (CRO) or reclaimed wastewater (WW, n=20 per treatment). Prior to and following treatment, each fish was weighed, and the total body length and the anal fin rays� lengths were determined. The study was designed to continue treatment of the fish for 30 days, but 13 days after treatment a significant quantity of the WW-treated fish died (p = 0.0012). Due to this high mortality rate, the remaining fish were sacrificed early. Analysis of the water indicated that the WW had significantly lower dissolved oxygen levels than the CRO water (p < 0.0001). There was a significant decrease in condition factor (p < 0.0445) and in the degree of anal fin elongation in the WW-treated group (p = 0.05) indicating no masculinization effect. Further examination of the WW indicated the presence of several microorganisms. These microorganisms may have originated from the activated sludge used in the wastewater treatment process or may have colonized the wastewater during transport and/or storage at the reclaimed water tank. Two non-mutually exclusive hypotheses may explain the mortality of the WW-treated fish. The microorganisms may have contributed to the depletion in oxygen levels, compromising the health of the fish, or the organisms may have caused infection or the release of plant toxins.