Resumo. AIM: Models of phytoplankton functional classification based on functional (FGs) and morphological (MBFGs) traits can be an important tool in aquatic monitoring. In this long-term study on phytoplankton, the goal was to use these two approaches to explain the changes in this community in an active channel of the Upper Paraná River floodplain, depending on the environmental conditions imposed by the hydrosedimentological regime. METHODS: Samples were taken between 2000 and 2013. RESULTS: 196 taxa were identified. Bacillariophyceae and Cyanobacteria showed higher contribution to biovolume. Were recorded 11 FGs (A, C, E, H1, J, Lo, M, MP, N, P and X1). The FGs C, Lo, M, MP, P and X1 were common to both periods. Already the FGs A, E, H1 and J occurred only in limnophase, while the FG N occurred only in potamophase. Were recorded seven MBFGs (I, II, III, IV, V, VI e VII). All seven MBFGs occurred in both hydrological periods, however the MBFGs III, VI and VII contributed with high biovolume values mainly in the limnophase. The FG P and MBFG VI were indicator of eutrophic status, while the FG M and MBFG VII were indicators of mesotrophic status. Only FGs reflected the environmental variability. CONCLUSION: The classification of phytoplankton in FGs and MBFGs represented an important tool for understanding of the behavior and dynamics of the species in relation to environmental conditions. However, the FGs appear to be more related to environmental variation this lotic channel than MBFGs. Probably this is related to the refinement of this classification, which reflected the changes in the community, in long-term scale, influenced by local and regional characteristics imposed by the hydrosedimentological regime of the Paraná River.