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Microhabitat distribution of benthic fauna in a high altitude andean stream

Abstract:

We studied Piburja stream, located in Ecuador at 3100 masl, in an evergreen Andean forest. Microhabitat distribution of taxa was studied during a period of five weeks in two different hydrological flow conditions. We measure water flow every ten minutes and studied taxa microhabitat distribution to investigate the role refuges during high and low flow conditions. We took surber samples (196 cm 2) in fast flow (rapids) and in areas with reduced hydraulic forces (refuges). We sampled five different times every five to six days for each season. Results show an increase of densities of almost all taxa during the dry season, and regardless of the microhabitat distribution, only few taxa had higher densities during the rainy season, while refuges showed an increase in total abundance. Certain trichopterans and dipterans showed higher densities in refuges than in rapid areas. Most ephemeropterans and the Simuliidae showed higher densities in rapids. The communities were clearly differentiated between rapids and refuges during the dry season. Nevertheless these differences became weaker during the rainy season, due to high hydraulic forces, showing that the use of refuges under high hydrological conditions might not be a significant adaptive trait in this stream.