Seasonal variability of the phytoplankton community of a lateral channel (Cortado) of the Upper Paraná River

Abstract

The seasonal variability of the phytoplanktonic community was studied in one lateral channel of the Upper Paraná River. The extensive samplings (monthly) were taken in three stations in the Cortado Channel (22º47‘30”S, 53º24‘37”W) from March of 1993 to February of 1994. Temporal changes in taxonomic composition, density, biomass, diversity and dominance were analyzed in relation to regional climate and hydrology, and to the physical and chemical factors of the water column. The phytoplanktonic community was composed of 95 taxa. The classes Cyanophyceae (Anabaena circinalis) and Bacillariophyceae (Aulacoseira granulata) were the most abundant, being responsible for the biomass peaks that occurred. The temporal variation in density and biomass did not show a clear seasonality, however, the highest biomass occurred in the late low waters (limnophase), with dominance of microplankton. Nanoplanktonic species, C-strategists common in Paraná River, mainly Cryptomonas brasiliensis, were abundant throughout the study period