Effects of natural banks of free-floating plants on zooplankton community in a shallow subtropical lake in Southern Brazil

the aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. first, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankton biomass and zooplankton community was tested. second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. three microhabitats were selected: free-floating plants, littoral area and open water. results demonstrated that the effects of different microhabitats on phytoplankton biomass and physico-chemicals were not significant, indicating a weak influence of the plants. zooplankton densities were higher in free-floating plants and littoral area, although the effect of microhabitats was weak for most of the predominant genera. the absence of free-floating plant effects on phytoplankton and physico-chemicals showed that it was not a factor influencing the microcrustacean distribution in the microhabitats. low differences in densities of zooplankton among microhabitats and low abundance of large-bodied cladocerans led to reject the hypothesis that free-floating plants act as a refuge for zooplankton.