Algae and cyanobacteria on painted surfaces in Southern Brazil

algae and cyanobacteria disfigure the external surfaces of buildings and may cause their physico-chemical deterioration. even though the climate in brazil is humid, there is no published literature on this problem. the objective of this work was to identify the major phototrophs present on brazilian constructions in residential, urban and rural sites. the algal and cyanobacterial types present on discolored surfaces of painted buildings in nine different municipalities in brazil, all lying between latitudes 19° south and 30° south, were examined. a total of 816 different organisms was detected in 58 sites. approximately 63% were single-celled or colonial organisms. the cyanobacterial genus, synechocystis, was the most biodiverse and frequently comprised the major biomass. it was present in 63.4% of sites. second and third most frequently detected were oscillatoria and the algal genus, chlorella, respectively. the latter organism showed the most widespread occurrence (72.4%). cyanobacteria were the most important colonizers, especially at urban sites, where over 62% of the organisms detected belonged to this class. filamentous phototrophs were found in smaller numbers than non-filamentous at all locations.