UW Aquatic & Fishery Sciences Quantitative Seminar

Ashley Steel

PNW Research Station, USDA Forest Service

Human impacts to riverine thermal regimes and biological consequences: From landscapes to experiments

Water temperature is a key regulator of aquatic communities. Human activities, such as dams, land-use, and climate change, impact the variability and complexity of water temperature regimes; yet, biological responses to these altered thermal regimes are just beginning to be understood. Alterations in thermal regimes may include not only increases or decreases to means, minimums, and maximums but reductions or increases in variability at multiple temporal scales. Understanding the impacts of altered thermal regimes is essential for effective management of freshwater habitats and will require attention to the complexities of natural thermal regimes, a better understanding of how humans impact thermal regimes, and research on the biological and physiological implications of human alterations to natural thermal regimes. We summarize 4 complementary approaches to understanding the relationships between human actions, thermal regimes, and biological response. First, we summarize data from a relatively undisturbed floodplain on the Sauk River, WA, to examine natural temporal and spatial variation in water temperature regimes. Next, we demonstrate how dams can reduce temporal variability at multiple temporal scales, an often overlooked regulator of riverine communities. Third, we introduce research to investigate the impacts of large-scale land-use patterns on variability in water temperature and flow regimes. Finally, we report exciting results from a laboratory experiment on how altered thermal regimes impact the egg to fry lifestage.