Nineteen stream segments of the Pedras River basin, (25º13'-25º26'S and 51º13'-51º28'W) were examined for the presence of macroalgae, of which 16 were visited once during the period of July 26 to August 21 2004 and three monthly from April 2004 to May 2005. Twenty nine infrageneric taxa and five "vegetative groups" were found. Cyanobacteria and Chlorophyta were the best represented divisions, followed by Rhodophyta and Heterokontophyta. Despite predominance of blue-green and green algae has been previously reported in several studies, the macroalgal flora of the Pedras River Basin showed, in general way, significant differences to other Brazilian regions. These results suggest that macroalgal communities are still little known, reflecting, basically, the scarcity of studies focusing these important primary producers in lotic ecosystem from Southern Brazil, particularly in Paraná State.
biodiversity; macroalgae; stream; Paraná state