A survey of the genus Phacus Duj. (pigmented Euglenophyceae) undertaken in two areas located in the northern portion of Patos Lagoon - Lake Casamento and associated ecosystems (30º03' - 30º34'S; 50º25' - 50º47'W) and ecosystems near Butiazal de Tapes (30º23' - 30º38'S; 51º16' - 51º29'W), revealed 37 specific and infra-specific taxa for this genus. The study aim was to increase knowledge of this genus in Rio Grande do Sul's coastal zone. The local climate is humid subtropical. The qualitative samples were collected in autumn and winter spring of 2003, on the banks of ponds, lakes, and marshes. Of the taxa identified, nine are new citations for the state while Phacus agilis Skuja var. inversa Bour., Phacus asymetricus Sokoloff, Phacus elegans Pochm., Phacus orbicularis Hübner f. communis Pop. and Phacus rostafinskii Drez. were reported for the first time in Brazil. All taxa are accompanied by maximum and minimum variations in air and water temperature, pH, and conductivity at the site where each taxon occurred.
Euglenophyceae; Phacus; taxonomy; southern Brazil
