Macroinvertebrados bentônicos como indicadores de qualidade ambiental de afluentes do Rio Uberabinha, Uberlândia - MG

Abstract

The use of biotic indices and different metrics of benthic macroinvertebrates has been widely used in studies on lotic systems in the context of environmental assessment, as well as the knowledge of the biotic and abiotic relationship and longitudinal dynamics of physico-chemical variables of these aquatic environments. This study aimed to evaluate the water quality of streams in the urban area of Uberlândia - MG, using metrics of benthic macroinvertebrate communities, and to characterize the seasonal and longitudinal dynamics of physico-chemical variables in these streams, evaluate the distribution and seasonal variation of macroinvertebrates and the influence of environmental variables on these communities. Cabeceira of Lageado stream (C1) is situated in a Natural Reserve, and the streams Buritizinho (C2), Lobo (C3) and Bons Olhos (C4) are directly inserted into the urban area. We conducted samplings in wet and dry seasons, evaluating the ecological conditions of the sites and calculating the metrics BMWP, Shannon-Wiener diversity, Pielou evenness, taxa richness, percentage of EPT, Chironomidae and Oligochaeta. The comparison of these metrics among streams in each sampling period was performed by analysis of variance (One Way ANOVA), followed by Tukey test. The comparison of metrics between sampling periods was performed by the paired t test and the relationship between them was evaluated by principal components analysis (PCA). We also evaluated physico-chemical variables of water and sediment. Correspondence analysis (CA) and principal component analysis (PCA) determined the most important patterns in taxa abundance and environmental variables data, respectively. The significance of environmental variables on the fauna was evaluated through Canonical Correspondence Analysis (CCA). In C1 EPTs were more representative, followed by C4 and C2. The Chironomidae abundance was high in all streams and Oligochaeta abundance was high in streams 2 and 3. Stream 2 had significantly lower values of taxa richness and BMWP than the other streams in the dry season. There were no seasonal differences of metrics within each stream. The % EPT, richness and BMWP better reflected the environmental quality of the streams, referring to the good quality of C1, followed by C4, and in worst conditions C2 and C3. The variables BOD, COD, organic matter, turbidity, conductivity and dissolved oxygen were the most important for stream differentiation, indicating a gradient of environmental quality, from C1, with good environmental quality, to C2, which showed very degraded waters, and C3 and C4 in intermediate conditions. Pollution sensitive groups were restricted to C1 and more tolerant groups occurred in higher abundance in C2. Considering the relationship between fauna and environmental variables, the variable dissolved oxygen was more important to Ephemeroptera, Coleoptera (other), Trichoptera (other), Hemiptera, Odonata, Hydropsychidae and Diptera (other), the BOD to Hydrophilidae and Hirudinea and turbidity to Collembola. Measures for recovery of the streams in the urban area of Uberlândia, aiming to improve the water quality are urgent. Moreover, it is clear the importance of the preservation of veredas for the associated lotic systems.