PS 62-43
Differences among zooplankton communities from small reservoirs and marginal lakes
The homogenization of habitats can decrease the richness of aquatic species, as zooplankton species. Marginal lakes in wetlands, different from artificial reservoirs, are subjected to river floods and can provide a high diversity of zooplankton fauna. This work aims at verifying if in small artificial reservoirs and marginal lakes, cladocerans and copepods communities differ in richness, density and functional groups. Samples were taken from a set of thirteen small artificial reservoirs in the northwestern region of the São Paulo State (Brazil) and in six marginal lakes of Paranapanema River wetland in the southeastern region of São Paulo State (Brazil), during dry and rainy seasons. It is known that different from the reservoirs, the marginal lakes are influenced by the floods of the river. Zooplankton samples were taken from both littoral and limnetic zones with a bilge pump and a 45 µm mesh net. Cladocerans and copepods species were identified and counted. Food preferences were identified for each species, and they were classified as filter feeding, scrapers phytophylous, omnivorous or predators. Differences in communities were analyzed by ASONIM and NMDS, and population densities and functional groups in both ecosystems were compared by ANOVA.
Results/Conclusions:
It was found that marginal lakes were more diverse than reservoirs. Species composition was statistically different in both ecosystems and only cladocerans were more abundant in the lakes. Filter feedings were the most abundant group in marginal lakes, and omnivorous densities were higher in reservoirs, suggesting that the zooplankton plays different functions in each environment. We then can conclude that marginal lakes and reservoirs provide different conditions for microcrustacean fauna. As a natural environment in wetlands, marginal lakes should be preserved for zooplankton species conservation.