ABSTRACT Human activities affect the availability and quality of water in many aquatic ecosystems. The Santa Bárbara Dam is an important source of public water supply in the city of Pelotas, Rio Grande do Sul, Brazil, which has been undergoing an accelerated eutrophication process, thus making it important to use environmental monitoring as a control tool for these sources. The aim of this study was to evaluate the community of benthic macroinvertebrates in the roots of floating aquatic macrophytes and their connection with water quality in the Santa Bárbara Dam accumulation basin. Four samples were taken in 2018, in two environments of this ecosystem. Physical-chemical analyses were conducted to correlate with biological analyses. Benthic macroinvertebrates taken from the roots of floating aquatic macrophytes were screened and identified at the lowest possible taxonomic level. For data analysis, multiple regression analysis, ANOVA, and Principal Component Analysis were used. Benthic macroinvertebrates were also analyzed for frequency, richness and abundance, and the Shannon-Wiener diversity index. It was possible to register 13.154 specimens of benthic macroinvertebrates associated with 100 g of dry weight of floating aquatic macrophytes, divided into 35 taxa, and distributed in 09 orders and 27 families. The most abundant groups were Amphipoda, Chironomidae, and Oligochaeta. The diversity index showed an average of H ‘= 1.67, classifying the aquatic ecosystem as moderately polluted. The tools used in this study are useful for managing and preservation of water sources, especially those used for public supply.

ABSTRACT Human activities affect the availability and quality of water in many aquatic ecosystems. The Santa Bárbara Dam is an important source of public water supply in the city of Pelotas, Rio Grande do Sul, Brazil, which has been undergoing an accelerated eutrophication process, thus making it important to use environmental monitoring as a control tool for these sources. The aim of this study was to evaluate the community of benthic macroinvertebrates in the roots of floating aquatic macrophytes and their connection with water quality in the Santa Bárbara Dam accumulation basin. Four samples were taken in 2018, in two environments of this ecosystem. Physical-chemical analyses were conducted to correlate with biological analyses. Benthic macroinvertebrates taken from the roots of floating aquatic macrophytes were screened and identified at the lowest possible taxonomic level. For data analysis, multiple regression analysis, ANOVA, and Principal Component Analysis were used. Benthic macroinvertebrates were also analyzed for frequency, richness and abundance, and the Shannon-Wiener diversity index. It was possible to register 13.154 specimens of benthic macroinvertebrates associated with 100 g of dry weight of floating aquatic macrophytes, divided into 35 taxa, and distributed in 09 orders and 27 families. The most abundant groups were Amphipoda, Chironomidae, and Oligochaeta. The diversity index showed an average of H ‘= 1.67, classifying the aquatic ecosystem as moderately polluted. The tools used in this study are useful for managing and preservation of water sources, especially those used for public supply.