Sensitivity of river organisms to anthropogenic temperature change

Humans increasingly impact stream and river temperatures.  Understanding species response to thermal shifts is therefore critical for environmental protection.  Predicting response requires thermal performance curves, which quantitatively relate organism level biological processes to temperature.  We used a quantitative synthesis of 120 curves from the literature to show that river organisms are highly sensitive to temperature change, particularly warming.  Fish were more sensitive to temperature change than invertebrates, suggesting sensitivity varies with trophic position.  Thermal performance curves were asymmetric and nonlinear, demonstrating that impacts of a given temperature change depend on the current thermal regime.  Many human impacts on river temperature are sufficient to reduce biological processes by 50%, quantifying the profound impact humans have on these critical ecosystems via temperature alone.  Our results highlight the urgent need for thermal mitigation measures, provide quantitative data to prioritize such measures, and inventory input data for models to predict aquatic species response.