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<br />will be obtained weekly from localities in the 16- and I8-mile reaches on the Colorado <br />River and from the Gunnison River so that a gradient of selenium concentrations ranging <br />from 2 to 20 J.1glL are studied. Site waters will be brought into the laboratory where they <br />will be used to culture food organisms (rotifers) for larval razorback sucker. For each site, <br />razorback sucker larvae will be exposed to site water and uncontaminated rotifers, or site <br />. water and rotifers reared in site water. Growth and survival of larvae will be monitored <br />over a 28-day period and the resulting data will be compared to predictions. Agreement <br />between observed and predicted toxicity will suggest that the predictive equations provide <br />accurate estimates of toxic effects of ambient selenium and that they can be used to assess <br />nursery habitats (Figure 2). Disagreement between observed and predicted toxicity will <br />suggest that the equations are inaccurate, or that other trace contaminants in water at the <br />sites influence the toxicity of selenium. Analysis and integration of other selenium <br />research will be used to investigate which alternative is most likely if observations and <br />predictions disagree. <br /> <br />IV. Study Goals, Objectives, End Product: <br /> <br />Goal: <br />To evaluate the accuracy of concentration-response equations that predict adverse <br />effects of exposure to ambient selenium on razorback sucker larvae in the Colorado <br />River Basin. <br /> <br />Objectives: <br />1. Use 28-day early life-stage toxicity tests to expose larval razorback sucker to <br />five test waters (four site waters and control water), and to food organisms that <br />have been reared in test waters. <br /> <br />2. Use equations that predict razorback sucker survival and growth as functions <br />of dissolved selenium concentration to estimate the response of study fish to <br />site waters, and compare predicted and observed responses. <br /> <br />End Products: <br />A final report that presents the experimental design, experimental conditions, results, <br />assumptions, and discussion of the utility of using the concentration-response <br />equations for predicting potential adverse effects in selenium-contaminated nursery <br />habitats. <br /> <br />V. Study Areas: <br /> <br />Laboratory: Aquatic Research Laboratory, Department of Fishery and Wildlife Biology, <br />Colorado State University, Fort Collins, CO 80523. <br /> <br />Selenium 3 <br />