Diversidade de macroinvertebrados aquáticos associados ao folhiço e ao processo de decomposição em córregos de cabeceira na região central do Brasil

Abstract

The use of aquatic macroinvertebrate communities for the indication of biological indices is na effective tools for the evaluation of water quality, and reveals the conditions of ecological integrity based on composition and distribution. Those organisms are active participants in the nutrient cycling in aquatic ecosystems of low order. Decomposition process constitutes one of the most important in the nutrient cycling and energy transformation in aquatic ecosystems and it is initiated by forces of lixiviation and by macroinvertebrate shredders that transform detritus to organic matter. The genus Phylloicus is being considered the most common shredder among those that constitute this trophic guild because it is an exclusive shredder of foliar detritus and uses this resource as food and also as shelter material. Its shredding activity may contribute extensively to the decomposition of foliar debris. This study aimed to acknowledge and evaluate the diversity of aquatic macroinvertebrates in hydrographic basins in the Cerrado biome in central Brazil using biological metrics based on the macroinvertebrate fauna. Study sites comprised 19 streams in three sub-basins of the Medium Tocantins River region. Streams were selected for perenniality. Macroinvertebrates were collected in stretches of 200 m in each stream and samplings at ten points 20 m afar, resulting in ten samples per stream during the transition period between dry and rainy season (September – October). All substrates present at the sampling point (leaves, stems, roots and sediment in both riffles and pools) were collected with a type "D" mesh (0.500 mm mesh size and area of 0.155 m2) device. Samples were mixed to form a composite sample per stream. At laboratory, the samples were washed with tap water on 0.25 mm mesh sieve. The macroinvertebrates retained in the sieves were fixed and preserved in ethanol 90%. Identification to family level and counting were carried out using a stereomicroscope (Leica model L2 and specialized literature. Metrics for richness, abundance, dominance, diversity and equity were calculated using Past 2.16. Abiotic data were submitted to analysis of variance using Assistat 7.7. after being tested normality by Shapiro-Wilk ). Anova testing was applied for regional and local data and Biostat 5.0 was used for the calculations of correlation, multiple regression and canonic correspondence. The macroinvertebrate fauna of low order streams in Cerrado presents high regional diversity and inter-region differences are less clear than local variations. Taquaruçu basin present a lower disturbance as compared to other basins. The metrics for ecological integrity and diversity indices revealed that the macroinvertebrate fauna suffers from impact of urban areas and sensitive taxa are reduced. In a general view, the study showed tendencies to be considered in future works aiming to explain the dynamics and functionality of streams in the Northern Cerrado of Brazil.