Macroinvertebrados bentônicos como indicadores biológicos da qualidade ambiental da bacia hidrográfica do Rio Piranga – MG

Abstract

Aquatic ecosystems have been suffering from impacts of natural and anthropic origins that may imply changes in their functioning. Among the human activities capable of causing such changes, the most expressive are those related to economic development, expansion of urban areas and population growth. Given these circumstances, the environmental monitoring of these ecosystems has proved to be an effective tool for the control and structuring of instruments aimed at their management. Therefore, the objective of the present study was to carry out an environmental diagnosis of the territory with the use of benthic macroinvertebrates in order to evaluate the quality of the Piranga River Watershed, Minas Gerais. The methodological approach comprised the morphometric assessment of the basin, physical and chemical monitoring of water quality, assessment of ecological conditions, analysis of biological and functional metrics of the benthic community, Principal Component Analysis (PCA) and Cluster. For this, analyzes were carried out at five points in the basin, based on the ease of access to the location and relevance of the stretch to the basin. The results of the morphometric evaluation show the fragility of the territory to hydrological and environmental phenomena. The characteristics of land use and cover revealed the predominance of livestock, which enables the expansion of pasture areas and the reduction of native forest. The application of the Rapid Assessment Protocol (PAR) allowed the classification of points P1, P2 and P3 as altered, P4 as natural and P5 as impacted. The results of the analysis of Hydrogenonic Potential (pH), Specific Conductivity, Temperature, Turbidity, Dissolved Oxygen, Total Phosphorus and Total Dissolved Solids and Trophic State Index (TSI) were framed according to the relevant legislation. From this point onwards, Point 5 was the one that presented the greatest environmental degradation and Point 4 as the most complete, a factor later corroborated with the analysis of biological metrics. In all, 505 organisms were collected from the benthic community, which were screened and identified down to the family level. Diagnostic interpreted according to the indices that characterize the water quality of the drainage basin at different levels, from bad to very good, showed results that obtained high correlation with the various physical and chemical parameters of water quality, as well as with the evaluation of physical integrity. at each point. The PCA presented seven variables that together explained 70.75% of the data variation. The cluster analysis made it possible to determine greater similarity between points P1 and P3, followed by points P2 and P4, and greater dissimilarity between P5 and the others.