Macroinvertebrados bentônicos em lagoas do médio rio Doce, MG: estrutura e composição taxonômica e funcional das comunidades

Abstract

In Ecology it is usual to describe a community through its species composition, which allows determining spatial and temporal patterns and their possible correlations with environmental factors. Functional classifications of organisms have been proposed as a complement or alternative to taxonomic descriptors, based on their biological and ecological characteristics, which are essential to understand and predict the consequences of changes in communities and ecosystems. In this study, four lakes with distinct trophy levels and under different anthropogenic impact were selected within the boundaries of the Rio Doce State Park (Carioca, Dom Helvécio and Gambazinho) and its surrounding region (Jacaré), aiming to analyze their benthic macroinvertebrate communities using taxonomic and functional approaches. The zoobenthic communities and physical and chemical parameters of water and sediment were sampled seasonally between 2011 and 2013. Taxa richness (71) and abundance of individuals (25.367) showed seasonal variation, and reflected a pattern associated with the level of environmental conservation of the lakes, where the best preserved environments showed higher numbers of taxa and individuals. The composition and structure of communities also differed between lakes, with dominance of the introduced aquatic snail Melanoides tuberculatus in lakes Dom Helvécio and Jacaré (the most impacted), and the dominance of Diptera Chironomidae in lakes Carioca and Gambazinho (the most preserved ones). The different taxonomic groups were related to abiotic environmental parameters, confirming the influence of habitat conditions in the distribution of organisms. Functional analysis resulted in groups of organisms with similar traits, giving rise to eight Functional Types (FT), which were correlated with environmental variables. The composition of Functional Types did not differ much between the lakes, but the structure of each community is distinct, with the dominant FT in lakes Dom Helvécio and Jacaré presenting characteristics as expected for impacted sites (such as fast populational growth, presence of hemoglobin, among others). Unlikely, in lakes Carioca e Gambazinho, not all characteristics of the dominant type fit into the expected. The sites inside lakes Dom Helvécio and Jacaré showed higher variation in the composition of Functional Types amongst each other than amongst points of the other lakes, probably because of the greater environmental heterogeneity in those locations.