Research · Ecological Management

Thermal Effects in Surface Waters

Study on the Thermal Ecology of fishes and aquatic systems has a long history at ORNL's Environmental Sciences Division going back to work in the early 1970's when the effects of heated effluents from powerplants was a major environmental issue. Current studies include:

Cold Shock and Episodic Impingement of Fish at Powerplant Intakes -- Recent rulings by EPA have caused a renewed interest in understanding the role that external factors (e.g., temperature and nutritional status) have on impingement at powerplant water intakes. We are performing laboratory studies to evaluate the physiological response of fish exposed to cold shock and depleted energy reserves relative to their susceptibility to impingement. (Sponsored by EPRI)

Fluctuating Temperatures -- Many fish in the wild are regularly exposed to rapid fluctuations in temperatures or intermittent exposure to extreme temperatures. We are performing lab experiments to derive technical information that can be used by the utility industry for recommendations to electricity generators on approaches to Clean Water Act Section 316(a) thermal discharge compliance. Questions we are addressing include: Is a fish's response to fluctuating temperatures different than its response to a daily average? What role do periodic exposures to less stressful temperatures play in recovery (or alleviation of stress) during times when fish are periodically exposed to stressful temperatures? (Sponsored by EPRI)

Indicators of Thermal Stress -- In hydropower systems, the effects of high temperature are often commingled with the effects of other environmental stressors. We have been testing the response of various bioindicators (blood serum compounds and stress protein expression) in fish to stressful temperature regimes relative to the expression of the same indicators in response to other stressors. We are hopeful that these results can be applied to identify the relative importance of multiple stressors in the field. (Sponsored by DOE Hydropower Program)

Bioenergetics Modeling of Thermal Effects Bioenergetics models are a useful tool for assessing effects of temperature on growth and reproductive output under various thermal regimes and climatic scenarios. We have developed and applied models for a variety of species (e.g., white sturgeon, brown trout, kokanee salmon, rainbow trout) to assess the implications of changes to natural thermal regimes. (Sponsored by Idaho Power Company and others)

For more information, contact
Mark Bevelhimer (, 865-576-0266)
Marshall Adams (, 865-574-7316)
Brooks Fost (, 865-574-8780)

Revised: 8/15/05

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