Research Interests:
Research Interests:
Research Interests:
We exposed a native endangered species, bonytail chub (Gila elegans), to graded concentrations of secondarily-treated effluent. At the end of each treatment period, we collected water from all raceways and samples were analyzed for the... more
We exposed a native endangered species, bonytail chub (Gila elegans), to graded concentrations of secondarily-treated effluent. At the end of each treatment period, we collected water from all raceways and samples were analyzed for the presence of 83 organic wastewater compounds. We extracted blood plasma from control and treatment fish in each raceway and samples were analyzed for hormones, 17β-estradiol and 11-ketotestosterone, and the egg yolk protein, vitellogenin.17β-estradiol concentrations were consistently lower in treatment females than those detected in control females. The 17β-estradiol and vitellogenin concentrations were always higher in treatment males than those found in control males. Concentrations of 11-ketotestosterone were consistently lower in treatment males than those detected in control males.Endocrine disrupting effects occurred in male and female fish exposed to low concentrations of effluent. Changes in hormone levels suggested a feminizing effect in tr...
In the borderland region of the desert southwest, human health and the ecosystems upon which humans rely largely depend on the quality, quantity, and distribution of water resources. In the Santa Cruz River Watershed (SCW), located in the... more
In the borderland region of the desert southwest, human health and the ecosystems upon which humans rely largely depend on the quality, quantity, and distribution of water resources. In the Santa Cruz River Watershed (SCW), located in the Arizona and Sonora, Mexico border region, surface water is scarce and unreliable, and, during much of the year, is composed of effluent from the local wastewater treatment plant. This makes groundwater the preferred and, consequently, primary source for industrial, agricultural, and domestic use. USGS scientists are using an integrative approach, incorporating the expertise of the Geography, Water, Biology, and Geology disciplines to identify risks to water resources in the SCW, and the potential for impacts to riparian ecosystems and ultimately, human health. This includes tracking organic and inorganic contaminants and their effects from sources to sinks in sediment, water, plants, and animals. Existing ground- and surface-water models will be us...