Composition and temporal variations of diatoms (Bacillariophyta) in the plankton of the Canastra reservoir, south of Brazil

Abstract

This study aimed at evaluating the diatom community composition found in the Canastra reservoir plankton and the temporal variation of the species from October 1997 to August 1998 and from January to December 2000, during the four seasons. The reservoir is located in Canela, in the state of Rio Grande do Sul at an altitude of 900 m in a sub-basin of the Sinos River The study was based on samplings carried out on the water sub-surface in the pelagic zone and in the litoral zone up the reservoir.The diatom community was composed of 51 specific and infraespecific taxa, including 24 genera and 19 families. About 70% of the taxa were only sporadicaly and occasionally present in different seasons of the year. Only Asterionella formosa and Urosolenia eriensis var. morsa were constant during the four seasons of the year. Among the taxa found, Achnanthes acares, Aulacoseira tenella, Brachysira inamoena, Encyonopsis subcapitata, Luticola undulata, Navicula insulsa, Nitzschia brevissima var. terricola, Pinnularia microstauron var. angusta, P. subcapitata var. subrostrata e P. viridiformis e Placoneis paraelginensis are first time reports for the State.