Influência de alterações de vazão sobre o drift de macroinvertebrados a jusante de uma barragem hidrelétrica

Abstract

Successive daily flood pulses from hydropower plants can disrupt aquatic ecosystems and alter the composition and structure of macroinvertebrates downstream. We evaluated the influence of flow changes on the drift of macroinvertebrates downstream of a hydroelectric plant as a basis for developing tools for the calculation of environmental flows that might lesser disturb aquatic biota. The aim of this study was to assess the influence of flow fluctuations on the drift of macroinvertebrates in seasonal and daily patterns. We collected macroinvertebrates at moments of fixed flow rate (380 m³.s-1 in the rainy season and 100 m³.s-1 in the dry season) and when flows fluctuated (380 to 430 m³.s-1 in the rainy season, and 100 to 180 m³.s-1 in the dry season) in 2010. We collected 31,924 organisms belonging to 46 taxa in the two sampling events. The taxonomic composition of invertebrates in the drift was differed during changes of flow, in both the rainy and the dry season. Macroinvertebrate densities differed between periods of fixed and fluctuating flows in the rainy season. We conclude that macroinvertebrate communities downstream of dams are influenced by daily flow fluctuations, especially during the rainy season. And thus, drift macroinvertebrates must be considered in environmental flow calculations because they clearly reflect the ecological changes in downstream biological communities.