The purpose of this study was the taxonomy of dominant periphytic algae (except Bacillariophyceae) of three natural substrates, Eichhornia azurea Kunth, Nymphaea amazonum Mart. & Zucc. and Oxycaryum cubense (Poepp. & Kunth) Lye in a semi-lotic environment (the Pau Véio backwater) at the Paraná River floodplain. Only those taxa with a frequency of occurrence over 75% of all samples were considered, except diatoms. Thirty-one taxa were illustrated, measured and identified at species level, a total of 31 taxa were described, distributed in classes: Chlorophyceae (3), Cryptophyceae (1), Cyanobacteria (14 taxa), Zygnemaphyceae (7), Euglenophyceae (2) and Xanthophyceae (4). Twenty-three taxa are first taxonomic reports for the Upper Paraná River floodplain: Chamaesiphon investiens Skuja, Geitleribactron subaequale (Geitler) Komárek, Chroococcus limneticus Lemmerm., C. minimus (Keissler) Lemmerm., C. minor (Kütz.) Nägeli, Aphanothece microscopica Nägeli, Phormidium molle (Kütz.) Gomont, Leptolyngbya angustissima (West & G.S. West) Anagn. & Komárek, L. foveolarum (Rabenhorst ex Gomont) Anagn. & Komárek and Pseudanabaena frigida (Fritsch) Anagn. (Cyanobacteria); Characium ensiforme Hermann, C. ornithocephalum A. Braun and Desmodesmus brasiliensis (Bohlin) E. Hegewald (Chlorophyceae); Cosmarium abbreviatum Racib., C. bireme Nordst., C. pseudopyramidatum Lundell, C. subadoxum Grönblad, C. trilobulatum Reinsch, Gonatozygon pilosum Wolle and Staurastrum forficulatum Lundell (Zygnemaphyceae); Trachelomonas hispida (Perty) Stein emend. Deflandre (Euglenophyceae); Cryptomonas tenuis Pascher (Cryptophyceae) and Characiopsis sphagnicola Pascher (Xanthophyceae).
connected pond; floodplain; periphyton; taxonomy
