Avaliação da qualidade da água da Bacia do Rio Formiga, utilizando macroinvertebrados bentônicos como bioindicadores.

The tributaries have undergone modifications in several local, regional and spatial scales, due to anthropic interferences. The benthic communities present in aquatic ecosystems respond to environmental impacts, reflecting water quality, so they are excellent bioindicators. Given the context, biomonitoring is an effective tool, since associated with traditional monitoring results in a complete diagnosis of water quality. In this sense, the objective of this work was to carry out a study of the composition and structure of the benthic macroinvertebrate community in the Formiga River basin. To achieve these objectives, the following hypotheses were tested: the community structure of benthic macroinvertebrates differs spatially in the rio Formiga basin as a function of water quality and whether there is a decrease in the taxonomic richness of good water quality in the sampling points close to the city , due to the release of domestic and industrial effluents. Seven collection campaigns were carried out (four in the rainy season and three in the dry season) of macroinvertebrates and physical-chemical parameters of the water for a period of one year (October/2019 to October 2020). The Rapid Assessment Protocol (PAR) was also applied. For data analysis, biotic indices and metrics of diversity, similarity and abundance were applied. A total of 10,076 organisms were collected, distributed in 57 taxa. The Formiga River basin in the sampled section presented water of good quality to bad quality, the chemical parameters that had the greatest variation were dissolved oxygen, nitrogen and electrical conductivity, downstream and upstream of the urban perimeter. The physical parameters divided the sampled section into two areas, a more natural one (points upstream of the urban perimeter) and an impacted area (in the center and downstream of the urban perimeter). The benthic community also presented its structure and composition different in the points that comprised the natural area when compared to the impacted area. The results showed the importance of using macroinvertebrate biomonitoring as bioindicators of environmental quality in aquatic ecosystems such as the Formiga River. Biomonitoring together with the routines carried out by the Autonomous Water and Sewage Service (SAAE), enabling a better diagnosis of the environment as well as the ecosystem's responses to different interventions in the basin. It is also suggested the need to increase efforts for the recovery, preservation and conservation of the Formiga River in the urban perimeter.