Identifying Estrogenic Effects of Wastewater on Receiving Stream Trout
Perhaps the microconstituents of greatest concern in the aquatic environment are those that mimic or interfere with natural hormones and have the potential to disrupt the endocrine system of aquatic organisms. The most potent of these endocrine disrupting compounds (EDCs) may be the natural and synthetic forms of estrogen, estradiol and ethinyl estradiol respectively, that have been shown to induce measurable effects in fish at environmentally relevant concentrations (1–4 ng/L). Reported effects include vitellogenin synthesis in males, intersex characteristics at the cellular level in gonad tissues, and population level effects such as skewed ratios of female to male fish. Municipal wastewater has been identified as a primary source of these EDCs to the environment. Snyderville Basin Water Reclamation District (SBWRD) in Park City, Utah, is concerned about the potential estrogenic effects of their effluent on brown trout (Salmo trutta) and Bonneville cutthroat (Oncorhynchus clarki) in the receiving stream, especially during late summer months each year when low flows upstream of the discharge point cause the lower reaches of the stream to become effluent dominated. Carollo Engineers (Carollo) assisted SBWRD with a project designed to investigate the estrogenic potential of the effluent. This project consisted of two major components: a sentinel study of trout held in the effluent in a pen to observe whether vitellogenesis occurred in male fish, and a field survey of females to males in the brown trout population downstream of the treatment facility to observe whether there was a skewed sex ratio towards a greater number of female fish. For the sentinel study 100 rainbow trout (Oncorhynchus mykiss) were individually tagged, measured for length and weight, and blood plasma samples (0.5 mL) collected before and after a three week exposure period. Fifty fish were placed in a pen in the final effluent, and the other 50 fish were held as a negative control at a hatchery. Blood plasma was treated with an anticoagulant and a protease inhibitor and then assayed for vitellogenin using an ELISA kit. At the end of the exposure period, fish were anesthetized and subsequently measured for total weight, length, gonad weight, and examined by necropsy to determine gender. Results for vitellogenin, gonadosomatic indices, and general health were compared for the two test groups of sentinel fish. For the field study, 70 brown trout were collected by electrofishing and gender was determined by partial stripping of gametes or necropsy. This paper will present the results of both the sentinel and field studies, and describe the methods used to investigate the impacts of effluent on trout.
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Document Type: Research Article
Publication date: 2009-01-01
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