Response to RC2

Abstract

Climate change affects aquatic ecosystems altering temperature and precipitation patterns, and the rear edge of the distribution of cold-water species is especially sensitive to them. The main goal was to predict in detail how change in air temperature and precipitation will affect streamflow, the thermal habitat of a cold-water fish (brown trout, Salmo trutta 15 Linnaeus 1758), and their synergistic relationships at the rear edge of its natural distribution. 31 sites in 14 mountain rivers and streams were studied in Central Spain. Models at several sites were built using regression trees for streamflow, and a non-linear regression method for stream temperature. Nine global climate models simulations for the RCP4.5 and RCP8.5 (Representative Concentration Pathways) scenarios were downscaled to a local level. Significant streamflow reductions were predicted in all basins (max. -49 %) by the year 2099, showing seasonal differences between them. The stream temperatura 20 models showed relationships between models parameters, geology and hydrologic responses. Temperature was sensitive to the streamflow in one set of streams, and summer reductions contributed to additional stream temperature increases (max. 3.6oC), although the most deep-aquifer dependent sites better resisted warming. The predicted increase in water temperatura reached up to 4.0oC. Temperature and streamflow changes will cause a shift of the rear edge of the species distribution. However, geology conditioned the extent of this shift. Approaches like these should be useful in planning the prevention and 25 mitigation of negative effects of climate change by differentiating areas based on the risk level and viability of fish populations.