Avaliação ecológica da sub-bacia do Alto Ribeirão Graipu(MG)

Abstract

The environmental degradation in the Graipu stream sub-basin (Guanhães, Minas Gerais) due to disturbances by human activities has been increasing and intense. The improper management of land use due to the conversion of native vegetation cover into pastures, deforestation of riparian forests, beyond the bushfires, have resulted in erosion processes in cropped areas and/or abandoned after mining, contamination of soil and water sources by domestic effluents. The aim of this study was to evaluate the ecological quality of freshwater ecosystems in the upper Graipu stream using a Rapid Ecological Assessment approach, which encompasses physical, chemical and biological parameters. The hypothesis that one-off and diffuse pollution negatively affects water quality and diversity of benthic macroinvertebrates was tested. It was predicted that: (a) stream sites minimally altered by human disturbances have greater diversity of habitats and greater abundance of pollution-sensitive and pollution-tolerant benthic bioindicator groups (e.g., Ephemeroptera, Plecoptera, Trichoptera); (b) stream sites heavily degraded by human disturbances have worse water quality, and low habitats’ diversity, where high abundance of pollution-resistant benthic bioindicators are found (e.g., Chironomidae and Oligochaeta). A Rapid Ecological Assessment Protocol for Habitat Diversity, benthic bioindicators, physical and chemical parameters were assessed in seven stream sites. Benthic samples were processed at the Laboratory Ecology of Benthos of Federal University of Minas Gerais. The taxonomic identification of macroinvertebrates resulted in the classification of 41 different taxa comprising a total of 1.441. The results showed a cause-effect relationship of anthropic activities on the benthic community. The diagnosis showed that stream sites in altered and degraded conditions had reduced water quality, contributing to lower habitat diversity and higher abundance of pollution-resistant benthic bioindicators. This information is essential to subsidize the water quality and benthic bioindicators monitoring in the Graipú stream sub-basin, in addition to implement environmental education activities, and support of water resources management measures.