Phytoplanktonic diversity in aquatic ecosystems along São Francisco river: sobradinho reservoir and marginal ponds, northeast region, Brasil - Moura, Ariadne do Nascimento; Severi, William; Dantas, Ênio Wocyli; Nascimento, Emanuel Cardoso do; Jaude, Paulo; Santos, Viviane Piccin dos; Bittencourt-Oliveira, Maria do Carmo (Plankton Symposium, 2007)