Phytoplankton associations of a coastal lagoon in south of Brazil

Abstract

The phytoplankton associations were investigated in the Patos lagoon, a subtropical, large, shallow, polimitic system during an annual cycle, in order to use it as a tool to provide information about the spatial-temporal variations pattern of this ecosystem. The study was based on surface water sampling collected monthly on the main N-S axis of the lagoon, from December 1987 to November 1988. Phytoplankton associations were composed mainly of , , and (Bacillariophyceae), , and (Cyanophyceae), (Cryptophyceae) and (Chlorophyceae) species. The distribution pattern of phytoplankton associations indicated that from December to March, north, middle and south areas were characterized by freshwater, brackish and brackish-marine associations respectively, meanwhile, from April to October a freshwater association was not evident, only returning in November. The analysis revealed highspatial and temporal variability in the distribution of the phytoplankton associations in the Patos lagoon during an annual cycle, which was related mainly to variation in salinity of the water in this ecosystem.