Duas Bocas is a small water supply reservoir (0.51 km²) located in a forested area (Duas Bocas Biological Reserve) (20º18'S and 40º28'W). Phytoplankton community was investigated by samplings weekly taken in the dry (July, 1998) and rainy (March 1999) seasons, at surface, euphotic/afotic boundary, and at the bottom of the water column. A total of 76 taxa was identified with the majority of Chlorophyceae (Chlorococcales) (37.3 %), Conjugatophyceae (Desmidiales) (26.7 %), and Cyanobacteria (Chroococcales, Nostocales e Oscillatoriales) (22.7 %). In addition, Euglenophyceae, Dinophyceae, Cryptophyceae, and Chrysophyceae totalized 13.3 %. The predominant genera were Staurastrum, Staurodesmus, Cosmarium, Desmodesmus, Ankistrodesmus, and Monoraphidium. Regarding to the frequency of occurrence, most of the rare and constant species were belong to Chlorophyceae (Chlorococcales) and Conjugatophyceae (Desmidiales) and Cyanobacteria, respectively. According to the literature, most of the species presented cosmopolitan distribution. Among the identified taxa, 44 species (57.9 %) are the first citation for the State of Espírito Santo.
floristic survey; vertical distribution; water supply reservoir
