Variação espaço-temporal de algas perifíticas em lagos da planície de inundação do alto rio Paraná.

Abstract

We aimed to evaluate the spatial-temporal variation of periphytic algal communities in lentic environments of the Upper Paraná River floodplain. Algae are microorganisms which are sensitive to environmental changes, and their rapid response provides a wide array of information on the ecological status of habitats in which they establish. We found that the variation in the structure of these communities was influenced mainly by the environmental characteristics and hydrological dynamics of the Paraná River over time. In a metacommunity perspective, algae were mainly influenced by the environmental factor (species sorting), and the variation in species composition (beta diversity) was higher during periods of higher water levels of the Upper Paraná River, associated with the increase in species dispersal among lakes. Among periphytic algal classes, Bacillariophyceae and Oedogoniophyceae dominated, with Achnanthidium minutissimum (Kützing) Czarnecki, Fragilaria capucina Desmazières, Gomphonema gracile Ehrenberg, Gomphonema lagenula Kützing, Oedogonium sp1 and Oedogonium sp3 being the most abundant species. Therefore, we confirmed that the environmental factor was predominant in structuring the periphytic algal metacommunity. When evaluating the influence of the seasonal variation in the hydrological regime on the algal community, we found that the change in the water level directly influenced the algal species. Thus, species richness changed with the increase in the water level and concomitantly, the limnological variables were strongly related to this hydrological variation. The dissolved forms of nutrients (nitrate and orthophosphate) and turbidity were the abiotic factors which influenced mainly the structure, organization, and presence of species such as Gomphonema augur var sphaerophorum (Ehrenberg) Grunow, Cymbella tropica Krammer, Gomphonema turris (Bacillariophyceae), Uronema gigas Vischer (Chlorophyceae), and Phormidium sp.1 (Cyanophyceae) in algal communities. Therefore, we demonstrated that the hydrological dynamics constitute an important role and a key factor in structuring periphytic communities in floodplains.