EFECTOS DE LAS ALTERACIONES DEL RÉGIMEN DE CAUDAL EN LA ESTRUCTURA DE ENSAMBLES DE MACROINVERTEBRADOS Y PECES: UN ENFOQUE TAXONÓMICO Y FUNCIONAL

Abstract

Flow variation imposed by hydropeaking may significantly affect macroinvertebrate and fish assemblages within the river network. As such, the responses of macroinvertebrate and fish assemblages to hydropeaking are expected to be complex and vary across spatial and temporal scales as well as ecological organization levels. To unpack this complexity, we assessed the interplay of geomorphic and hydrological variables as drivers of the responses of macroinvertebrate and fish assemblages to hydropeaking. Specifically, we studied different levels of ecological organization of macroinvertebrate and fish assemblages in two functional process zones (FPZs; Sub-Andean and Central Valley Gravel Dominated) subjected to different flow management in two Chilean Andean river networks. Hydropeaking caused significant reduction of macroinvertebrate and fish abundances in both FPZs and at all ecological organization levels. Furthermore, the response of macroinvertebrate and fish assemblage variance was stronger in the Central Valley Gravel Dominated FPZ. Both geomorphic and hydrological variables drove macroinvertebrate assemblage responses. However, the effects of the principal geomorphic variables operated at valley (meso) spatial scale and main hydrological variables operated at sub-daily (micro) temporal scale. Therefore, to minimize the effects of hydropeaking on macroinvertebrate and fish assemblages, flow management should consider reduction of sub-daily variability. Furthermore, placement of new barriers should take into account not only their position within the river network but also their effects downstream that strongly depend on characteristics of river valley.