Comparação da diversidade da comunidade zooplanctônica ativa e dos ovos de resistência presentes no sedimento do reservatório da UHE de Furnas-MG

Abstract

The operation of the dam reservoirs is result of large fluctuations of the water level determined by seasonal variations and by human action. These alterations cause changes in the structure and functioning of zooplanktonic community. The objectives of this study were to compare the composition and species richness of the zooplanktonic community both active and present in the sediment, and verify the possible influence of limnological variables in the structuring of the active zooplanktonic community in the Furnas reservoir (MG). The samples were collected monthly from July 2013 to February 2014. The zooplankton samples were collected along the water column with a suction motor pump (400 liters) and plankton net of 68 μm and the limnological variables were measured with a multisensor Horiba U-50. The samples of sediment (Kajak) occurred from December 2013 to February 2014. Hatching tests of resting eggs were performed in the laboratory maintaining the temperature at 25 ± 2 ° C and photoperiod of 12/12 hours in germination chambers. There was a reduction in the volume of water Furnas reservoir due to lower rainfall in the study area in recent years. This reduction of water volume and the increase in human activities resulted in an increase of the trophic level in the reservoir (mesotrophic), which may have contributed to the formation of resting eggs by zooplankton. On site with higher trophic level, the greater amount of weeds and where it was previously launched the domestic and industrial sewage in the city of Alfenas, there was a higher number of eggs in the reservoir sediment and richest in species of zooplanktonic community. Comparing the active zooplankton community and resting eggs observed richest in species in the water column, but some species were recorded only in the sediment which reinforces the importance of dormancy strategy for the maintenance of species richness of active zooplanktonic community of the reservoir, the sediment being considered a repository of organisms.