Considering the scarcity of studies focusing on stream macroalgal communities in subtropical regions, the present study was conducted to investigate the environmental and temporal distribution patterns of these communities in a well-preserved region of ombrophilous dense forest. Eight samplings sites were sampled twice (Summer and Winter) in the Serra da Prata (Saint-Hilaire/Lange National Park), located in eastern portion of the Parana State, southern Brazil. The Principal Components Analysis (PCA) showed that the environmental variables of the investigated streams had a clear temporal pattern, with an evident distinction between winter and summer conditions. In contrast, the Detrended Correspondence Analysis (DCA), based on the presence/absence of macroalgae, did not reveal any temporal pattern, without evident differences between winter and summer floristic compositions. One pattern showed by the DCA was the separation of sampling sites by the intensity of riparian vegetation shading. Overall, the study region showed low values of richness and abundance, and the occurrence of majority of taxa were restricted to a single sampling site. Thus, the results suggested that the structure of the macroalgal communities studied seem to respond to a combination of environmental variables that change continuously in time and space, emphasizing the importance, among others, of variations on a small scale (microhabitat). Moreover, the results also showed that, on a global scale, the distribution of lotic macroalgae in the study region can, apparently, be limited by the degree of shading imposed by riparian vegetation.
local variation; ombrophilous dense forest; Saint-Hilaire/Lange National Park; shading; subtropical region
