Macroinvertebrados bentônicos como bioindicadores de qualidade de água para monitoramento de serviços ambientais hídricos na bacia do Arroio Epaminondas, Pelotas (RS)

Abstract

Benthic macroinvertebrates are essential aquatic organisms in the maintenance of some ecosystem services in the rivers, such as nutrient cycling and water quality regulation. They vary in the structure of their community in the face of environmental changes, which allows their use as bioindicators of water quality. This variation can affect the provision of ecosystem services, impairing the purification of the watercourse. Water security policies, such as payments for environmental services schemes, appear in this scenario to financially encourage good conservation practices aimed at maintaining and improving ecosystem services. This work aims to identify bioindicators, from the benthic community, for use in monitoring environmental services in the Epaminondas Stream basin. Four data collections (one for each year season) were made at nine points in the Epaminondas basin, being distributed in different stretches of three streams (A, B and Epaminondas). At each collection, water and benthic organisms were sampled, in addition to the application of a habitat assessment protocol. The physicochemical parameters evaluated were temperature, pH, dissolved oxygen, conductivity, turbidity, total dissolved solids, phosphorus, ammoniacal nitrogen and nitrite. From them, the classification of water use classes established by CONAMA 357/2005 and an index of trophic status were carried out, which together with the dissolved oxygen assessment sought to analyze the stream self-purification. The biological samples were screened, identified, and classified into functional trophic groups, being submitted to the metrics of abundance, richness, and constancy of occurrence, in addition to the application of the BMWP biotic index. The data were processed in the statistical program R through rank order analysis NMDS and IndVal. The Epaminondas stream and stream A showed better self-purification, while a good structure was observed in the benthic community. The upstream section of Epaminondas remained with poor water quality, but the good physical condition of the environment allowed the establishment of filtering organisms which helped in the regulation of water quality for the downstream sections. The families Gomphidae, Leptophlebiidae Policentropodidae Perlidae, Hydropsychidae, Gripopterygidae were identified as indicators of environmental services in the basin. Thus, it is concluded that the structure of the benthic community allows to verify the quality of the water, since the impacts affect its composition, impairing the provision of its ecosystem services.