Efeitos dos processos locais e regionais na estrutura das comunidades fitoplanctônicas de áreas úmidas subtropicais

Abstract

One of the main questions that challenges community ecology is to know how the different local and regional factors, and the dispersion capacity of species determine the structure and dynamics of biological communities. Traditionally, local processes are used to describe community structures, however, in recent years the ecology of metacommunities seeks to integrate local factors with regional factors, emphasizing the importance of the spatial dimension in ecology studies. Through the exploration of local and regional factors influence on aquatic ecosystems, it is possible to indicate the consequences of human impacts and work on the conservation of aquatic ecosystems, with efficient conservation policies. Based on these assumptions, the main objective of this thesis was to analyze the phytoplankton structure in a spatial gradient of wetlands at the coastal plain of southern Brazil taking into account the distribution patterns of the communities, its functional structure based on functional morphological groups (MBFG), and the influence of local and regional variables. The sampling was carried out between the months of May and June 2017 in 15 wetlands of the coastal plain of Rio Grande do Sul, covering an extension of 560 km. In relation to the main results obtained, 114 phytoplankton species were identified, distributed in nine phytoplankton classes. There was a community distribution pattern opposed to the nested pattern (antinested), which was correlated mainly with the variable TDS (total dissolved solids), which tends to promote light limitation by interfering with photosynthetic ability of microalgae. The Zygnematophyceae class presented the highest total species richness and the highest total biomass value. The functional morpho group IV (small nonflagellated organisms) was the most representative in number of species, and the functional morpho group VII (large mucilaginous colonies) had the highest biomass values. Regarding the metacommunity approach, it was observed that there was an influence of local and regional factors. The decay of similarity with distance and antinested pattern, are influenced by the the effect of space, evidencing a limitation of species dispersion. The local and regional factors tend to contribute to the observed patterns and show a spatial structure of phytoplankton communities in the studied wetlands, influenced mainly by species that dominate shallow environments with dominance of macrophytes. Considering the total species composition, turbidity was the only variable that was associated with the community structure. Regarding the taxonomic classes, different groups were formed according to the analyzed class, where the better adjustments contained urbanization, nitrite, area, dissolved oxygen and total dissolved solids. The results of the present study highlight how dynamic and complex the phytoplankton communities are, with a significant increase in knowledge about the factors that influence microalgae communities in natural subtropical wetlands.