<b>Community structure of periphytic algae in a floodplain lake: a long-term study

This is a study with temporal approach on the community of periphytic algae in the upper Paraná riverfloodplain, inserted in the Long-Term Ecological Research/CNPq, site 6. We sought to evaluate the community structure of periphytic algae, analyze the influence of abiotic factors on this structuring, and determine a model for the density of the phycoperiphyton community in 11 years of study. Samples were taken in two periods of the year (February/March and August/September) at PatosLake, lentic environment between 1999 and 2009, using as substrate the petiole of Eichhornia azurea Kunth. The highest density was found in February 2002, after a long dry period. The lowest density was observed in March 2005, period with the highest richness in the study (165 taxa), when the water level of theParaná river reached its highest value. During the study, the community density has responded to local environmental variables and the model generated has summarized 45% of the first NMDS axis, indicating the structure of the community by the intensity of flood pulse or even by the absence in determinate years.