Local environmental factors are the main drivers of phytoplankton biovolume in subtropical streams of Brazil.

The ecological attributes of phytoplankton in freshwater environments are strongly influenced by limnological factors and temporal variability. In this study, we investigated the importance of local environmental and regional (spatial and landscape) predictors in structuring stream phytoplankton from the perspective of metacommunity theory. We seasonally sampled phytoplankton and abiotic variables from nine streams in three subtropical basins. Variation partitioning was used to investigate the influence of environmental, landscape, and spatial predictors on phytoplankton biovolume. Independent of the hydrological period (dry and rainy), the phytoplankton communities were predominantly structured by local environmental factors. In addition, the different land uses considered (landscape) showed weak significance during the dry season, with emphasis on the rural category. Biovolume values remained low, and diatoms and green algae were the most representative groups. Our findings are consistent with recognized ecological patterns for potamoplankton and emphasize local environmental filters as a fundamental regulator of phytoplankton biodiversity in lotic environments.