Efeito dos fatores ambientais e das mudanças climáticas sobre a comunidade perifítica em lagos rasos de água doce.

Abstract

The periphyton community structure in freshwater shallow lakes is lake community structure is determined by processes at different spatial and temporal scales, including the hydrodynamics of the system, nutrients, herbivores, light, substrate and temperature, as climate change stressors. The studies presented in this thesis aimed to understand the periphyton and the factors affecting this community in freshwater shallow lakes. Using an observational approach, we evaluated which limnological variables affect the biological traits of periphyton in shallow lakes located in the Upper Paraná River floodplain. The sampling sites were established according to the percentage of macrophyte coverage Eichornia azurea (0-35, 50-75 and 75-100%), and other limnological variables were sampled. Overall the biological traits were influenced mainly by temperature. However, other factors also influenced the community, such as water level, nutrients and more weakly by macrophyte coverage percentage of 0-35%. Using an experimental approach, we tested how biovolume and species composition of periphyton response in environmental conditions and in front of environmental disturbance in form heat wave (+5°C). The results showed that the heat wave stimulated the growth of cyanobacteria and diatoms, green algae have been adversely affected. Furthermore, the heat wave directed the prevalence of some taxons, thus changing the species of composition.