Caracterização ecológica de nascentes sob diferentes pressões antrópicas e sua relação com a comunidade bentônica na Zona da Mata Mineira, Brasil

Abstract

Spring ecosystems are complex, unique, highly interactive and heterogeneous, comprising a wide variety of microhabitats. However, they are becoming increasingly vulnerable to the expansion of human activities. The biological communities that colonize headwaters reflect prevailing environmental conditions, integrating the effects of multiple pressures and providing an aggregate measure of human impacts on these aquatic systems. Against this backdrop, this study characterized twelve perennial springs under different anthropogenic pressures (secondary forest, forest restoration, pasture and urban area) and assessed the relationship between these impacts and the structure of the benthic macroinvertebrate community, which included the taxa Acari and Copepoda, which may share size characteristics with the meiofauna. The study is structured into two chapters. The first presents an environmental assessment of springs based on macroscopic evaluations and analyses of microbiological, nutritional and physico-chemical variables in the water and sediment, across two hydrological periods. In this chapter, results show that springs with preserved native vegetation were in an optimal or good condition (>35 points), whilst those affected by human activity exhibited varying degrees of degradation (<32 points). Statistical analyses indicated that the conversion of forest into urban and pasture areas alters the sediment parameters and the physical, chemical and nutritional parameters of the water from the springs assessed. In contrast, forest restoration processes in degraded areas promote environmental conditions closer to those observed in secondary forests. Furthermore, total coliforms and Escherichia coli were detected in all springs, with higher contamination associated with the rainy season, indicating the influence of surface runoff. The second chapter assessed the effect of different land uses and land cover on benthic macroinvertebrate communities and their functional organization in the studied springs during the period of lowest water availability. The results show that the categories assessed exhibited distinct environmental signatures, with springs in secondary forest displaying greater stability and structural complexity. Although univariate tests did not indicate significant differences in richness and abundance due to the sample size per category (n=3), the springs in secondary forest exhibited higher numerical values for richness and diversity, as well as a unique biotic composition. The analysis of indicator species (Indval) corroborated this distinction, identifying specialist taxa associated only with springs with preserved riparian vegetation. In contrast, springs in urban areas exhibited high hydrodynamic instability (flashiness) and simplified communities. It was therefore concluded that the restoration of spring ecosystems is a long-term process that requires the stabilization of the substrate as well as the restoration of the surrounding vegetation, with a multivariate approach and diversity indices serving as robust tools for assessing the health of these aquatic systems. Furthermore, the need for integrated strategies that combine immediate protection-through fencing and the maintenance of riparian vegetation-with long-term sustainable interventions is emphasized, with the aim of ensuring water quality and biodiversity in springs within the Atlantic Forest of the Zona da Mata region in Minas Gerais.