Drift de macroinvertebrados em riachos de cabeceira

Abstract

The headwaters covered by riparian often depend on allochthonous input of organic waste as an energy source for the water metabolism. The relationship between the availability of food resources and invertebrate drift in headwaters streams in tropical regions are still poorly known. In general, the density of invertebrates in the drift increases in response to reduced availability of food resources . The aim of this study was to evaluate the relationship between the availability of food resources and the composition and density of invertebrates in the drift. Samplings were done in dry and wet seasons in nine headwater streams at the Espinhaço Cordillera (MG, Brazil). At each stream samples of coarse particulate organic matter (CPOM) and fine (FPOM), periphyton, invertebrates in drift and sediment samples were collected to assess the propensity of macroinvertebrates to drift. There were no significant differences in values between the propensity periods of drought and rain. Gatherers-collectors and filtercollectors occurred in high densities in the two sampling periods. Gatherers-collectors were negatively related FPOM indicating that the streams where the availability of FPOM is low, the densities of organisms gatherers-collectors in the drift is high. However, this relationship was positive with the filter-collectors. These results confirm that the drift of invertebrates is related to the availability of food resources, especially for gatherers-collectors invertebrates that feed on material deposited in the interstices of the substrates. Potentially, changes in the stability of the fund headwaters influences the availability of FPOM as a result of changes in the use and occupation of land in the surrounding areas, stability margins and diversity of physical habitats.