Distúrbios antrópicos locais causam danos a assembleias de bioindicadores bentônicos em uma bacia hidrográfica protegida

Abstract

The increasing changes in aquatic ecosystems caused by human interventions are the reason for the rapid and irreversible transformation of global ecosystems. These not only cause a decrease in water availability for human uses, but also cause hydrological changes in aquatic ecosystems, loss of habitat for aquatic species and, consequently, a decline in biodiversity. That is why it is necessary to study, develop and consolidate effective methodologies for environmental assessment and to subsidize the actions of conservation of aquatic ecosystems in watersheds. Aquatic invertebrate assemblages have often been used as water quality bioindicators, in multiple perspectives: (i) application of multimetric indices in biotic integrity assessments that integrate multiple biological and ecological attributes of assemblies; (ii) application of models that assess the probability of anthropogenic stressors to impact aquatic biota; (iii) as ecological indicators through the analysis of especific groups. The objective of this thesis was to assess the ecological condition in the Pandeiros River basin (MG / Brazil), answering the following questions: a) Can benthic multimetric indices be used regardless of where they were developed? b) Is the biological condition affected by human disturbances in protected and priority areas for the conservation of biodiversity? c) Are the genera of the organisms of the Chironomidae and its functional characteristics effective to assess the ecological status in Neotropical streams? We found that ten multimetric indices were effective in assessing the ecological condition in a basin with moderately altered environmental conditions and only local stressors. The evaluated disorders (% pasture, IDI (Integrated Disturbance Index), W1_hall (impact index in the riparian zone), LRBS (Low Relative Bed Stability), % fines) occurred in 20-40% of the basin extension, with the presence of thin substrates and integrated anthropogenic disturbances (IDI and W1_hall) being the most important threats to low MMI scores of biological condition. We found strong relationships between environmental variables (% sand, immersion, %pastures, % agriculture, % fines, W1_hall, and canopy cover) and characteristics of the Chironomidae assembly (predators, herbivores, miners, engulfers and body size). This study enabled the standardization of effective methodologies and tools for ecological assessments, even in places with low disturbance, in addition to identifying the main stressors and pressures associated with the poor biological conditions present in the watershed of the Pandeiros River Basin and assessing the magnitude of these stressors and pressures. This study provided evidence that even in protected areas, local disturbances degrade the biological condition, indicating the importance of local actions for the conservation and rehabilitation of a balanced ecological condition in tropical watersheds.