Composição e estrutura da comunidade de macroinvertebrados associados a macrófitas aquáticas em um córrego da cadeia do espinhaço (MG)

Abstract

The distribution pattern of aquatic organisms in lotic ecosystems can be determined by several factors like the current velocity, temperature of the water, substrate, dissolved oxygen and interaction with other organisms. With the aim to evaluate the composition and structure of community macroinvertebrate associated with macrophytes, in a stretch of Córrego das Éguas, (MG), were sampled monthly for 12 months. Selected five stands heterogeneous composed of two aquatic macrophytes with different architectural patterns, Diamantina lombardii (Podostemaceae) and Eriocaulon aquatile (Eriocaulaceae). In each of these stands was removed 1 square in the center of 100cm2 and 1 on the edge with the aid of the collector type "Surber". Measures depth and current velocity at the center and at the edge of each stand were carried. Macrophytes were washed, identified and dried in greenhouse at 70°. After washing the macrophytes, the associated macroinvertebrates were separated and identified the lowest possible taxonomic level and classified as trophic functional group (TFG) according to appropriate literature. Sampled 57.535 macroinvertebrates, distributed into 68 taxa and in five trophic functional group. Of these 34.237 were found in the center of stands and 23.298 on the edge. When compared the density of macroinvertebrates between the center and edge, was observed significant difference, well as taxa richness. As to TFG, just density of filterers collectors was different. Between the dry and rainy seasons, both taxa richness, as the abundance of macroinvertebrates were higher in the dry. When compared length (cm) of larvaes between the center and the edge, it was observed that there is a significant difference in size for all instars. The larvae located in the center of the stand are larger than those found on the edge. The biomass of macroinvertebrates was also significantly different between the center and the edge of stands. When evaluating the influence of the current can be observed that the taxa richness and density of macroinvertebrates were negatively influenced. However only the taxa richness of scrapers and gathering collectors were influenced, and this influence was negative. The occurrence and abundance of taxa varied among the months sampled, but no difference was found between the center and edge of the stands. The present study showed that the edge effects have a large influence on macroinvertebrates associated with aquatic macrophytes, as well as the type of substrate showed large importance on the structuring of macroinvertebrate community. The current velocity influences negatively the abundance and richness of macroinvertebrates. Inside stands of aquatic macrophytes there is larger abundance, size and biomass of macroinvertebrates than the edges. However, the composition and richness of rate did not differ between center and edge. Furthermore, the composition, richness and abundance of macroinvertebrates vary according to seasonal changes. Among the factors analyzed, edge effects were the factors most influenced.