The environmental and anthropogenic impact onfreshwater biodiversity in Lajeado, RS, Brazil. : A study of using dragonflies as indicators for theenvironmental status in freshwater biomes

Abstract: Fragmentation of the Atlantic rainforest and alteration of waters due to agricultural expansion hasgreatly affected the species diversity in Brazil. In this study, we investigate how different environmental factors affect dragonfly communities and dragonfly species richness in sixteen different locations in Rio Grande do Sul, Brazil. A total of 328 individuals distributed among 46species and eight families were collected. At each sampling location the water was analyzed andthe surrounding environment recorded and plotted. Our goal was to investigate if we could findspecies for use as bio indicators on water quality and if the fragmentation of the forests in RioGrande do Sul affects the species richness negatively. Our data suggested that the amount offorest, pH level and water temperature have a strong correlation to the number of species. For thenumber of specimens we found that amount of forest, pH level, water temperature, conductivity,amount of dissolved solids in the water and amount of surrounding urban area affects thepopulation. We found that still water holds more species as well as specimens than current water.The species T binotata, M Ocellata, Oxyagrion Sp., L pictus, M stawiarskii, R planaltica, Lauritus and L dichrostigma could possibly be used as indicators for pH level, and that Sreticulata, L bipupillatus, B furcata, R bonariensis, D mincki and T cophysa possibly could beused as indicators for conductivity. Further studies has to be done in order to be certain about theuse of these species as indicators.