Data on richness, density, diversity and distribution of dinoflagellates in aquatic habitats (open and closed lagoons, channels, reservoirs and wetlands) during high and low water periods are presented. The study was based on 23 point samples, located on the eastern (Lagoa do Casamento area) and western (Butiazal de Tapes area) shores of Laguna dos Patos, in 2003. Eleven taxa were identified; taxon distribution was more homogeneous during the high-water period. Durinskia baltica (Levander) Carty & Cox was the only taxon whose distribution was the same for both hydroperiods. Peridinium gatunense Nygaard was a high-water indicator species and P. umbonatum Stein was an indicator of habitats associated with the Butiazal de Tapes area. This area had higher Dinophyceae diversity than the Lagoa do Casamento area, regardless of hydroperiod, due to the higher diversity and specificity of aquatic habitats. Habitat type significantly (p <0.01) influenced richness, density and diversity of dinoflagellates, and density was significantly influenced (p <0.01) by hydroperiod. Cluster analysis showed that pH and water temperature were the abiotic variables that had greater influence on the dinoflagellate populations in this study.
Dinophyceae, ecology; freshwater; subtropical zone
