Abstract
The aim of this study was to analyze the effects of flood pulses (intensity) on the richness and composition of periphytic algae in lentic environments of the Upper Paraná River floodplain, over a six-year period. Other factors, such as connectivity of the environments with the main channel of the river and the availability of substrate for the periphyton, were also evaluated. For qualitative analyses, periphyton community was sampled from adult petioles of Eichhornia azurea Kunth taken from the littoral regions of the lakes studied. A total of 457 taxa of periphytic algae, distributed within 141 genera and 10 classes, were registered in the four environments. The greatest richness of periphytic algae was observed in connected floodplain lakes, especially in 2007 and during high water periods. In both connected and disconnected lakes, richness correlated positively with water levels of the Paraná River. Richness was also positively correlated with the number of taxa of aquatic macrophytes. The specific composition of periphytic algae differed between high and low water periods, and between connected and disconnected lakes. Therefore, among the considered variables, it is evident that flood pulse constitutes the principal force acting on periphytic algae communities of the floodplain, followed by the degree of connectivity and the presence of aquatic macrophytes.
Highlights
The Upper Paraná River floodplain displays a great heterogeneity of aquatic habitats, which promotes high biological diversity (Thomaz et al, 2007)
A total of 457 taxa of periphytic algae distributed within 141 genera and 10 classes were recorded in all lakes and periods
Richness of periphytic algae in the lakes studied was greater during high water periods than low water periods, as shown by the positive significant correlation between periphytic algae richness and the level of the Paraná River, and by the analyses of variance
Summary
The Upper Paraná River floodplain displays a great heterogeneity of aquatic habitats, which promotes high biological diversity (Thomaz et al, 2007). Lentic environments from the floodplain (lakes and backwaters) are predominantly shallow and present extensive communities of aquatic macrophytes. These plants increase the heterogeneity of littoral zones, providing space for colonization and supporting specific biota (Junk, 1970; Wetzel, 1983), in particular, the periphyton (Fonseca and Rodrigues, 2005; Leandrini et al, 2008), a complex community either firmly or loosely fixed to submersed substrata (Wetzel, 1983)
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