Potencial Uso De Los Macroinvertebrados Como Indicadores De La Calidad Del Agua en Cuencas Altas De Bajo Impacto: Caso De La Cuenca Del Arroyo San Francisco, Uruguay

Abstract

Stream macroinvertebrate communities are modulated by different ecological processes that occur from the watershed to reaches and local sites, which can be directly or indirectly affected by human activities and changes in land use. This study evaluated the effects of water quality on macroinvertebrate structure in a low-impacted highland watershed, the San Francisco stream drainage basin, Lavalleja, Uruguay. We measured in situ physico-chemical water variables and collected a total of 50 macroinvertebrate samples using a Surber sampler in 10 reaches in different stream's order and basin size. Macroinvertebrate community structure was analyzed using density, richness, and two common bioindicator indexes: percentage of number of Ephemeroptera, Plecoptera and Trichoptera (%EPT) and percentage of Oligochaeta (%Oligochaeta). Although we did not find a significant relationship between physico-chemical st water variables and stream order, the 1 order streams had comparatively higher water nutrient concentration and higher conductivity. The %EPT and %Oligochaeta indexes could largely be explained (positive and negatively, respectively) by stream order, but in general st not by water quality per se. However, in 1 stream order reaches a connection with local water quality arose. Moreover, no patterns were found for density and taxonomic richness with stream order or water quality. Altogether, our evidence suggests the potential for using macroinvertebrate indexes as water quality indicators, even in well preserved drainage basins.