Stefania Biolo and Liliana Rodrigues
Periphyton collected from distinct macrophytes in a lake permanently connected to the Paraná River were submitted for analysis of the periphytic algae community structure, quarterly in the years 2008 and 2009. Limnological data were concomitantly measured. Flood pulses, hydrometric levels of the Paraná river and hydrological periods were irregular in 2008. It was found 406 taxa of periphytic algae, with greater richness corresponded mainly to the classes Bacillariophyceae and Zygnemaphyceae. The mean values of richness were not significantly different among substrates (p=0.297; F=1.342), but were for algal density (p=0.037; F=4.390) and diversity on Eichhornia azurea (Sw.) Kunth; Pontederiaceae), probably due to its architecture and morphology being more suitable to the development of periphytic algae, mainly diatoms. Oxycarium cubense, due to its fragile architecture and delicate morphology, favoring mainly metaphytic algae as Zygnemaphyceae. In June and September 2008, Bacillariophyceae was prevalent (predominantly represented by Achnanthidium minutissimum (Kütz.) Czarn. (Bacillariophyceae), which could represent a greater tolerance of these microalgae during unfavorable periods. Mean values of diversity were significantly different after November 2008, with higher average values of the hydrometric levels and temperatures. It concluded that, in an extreme variable environment, such as the floodplain, although significant differences have been found, both the environmental conditions and the type of substrate were essential for structuring the periphytic community.
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