Efeito de barramento e de eventos hidrológicos extremos sobre os padrões de diversidade beta funcional do fitoplâncton de planície de inundação.

Abstract

Dams and predicted future extreme weather events can affect the structure of aquatic communities, both at a local and regional scale. They can influence, for example, the importance of sites and species for regional diversity as they promote local processes of extinction and colonization, as well as processes of biotic homogenization on a regional scale. It was investigated how damming and prolonged flood and drought periods influenced the local contribution to beta diversity (LCBD) based on phytoplankton functional groups (GFR), as well as the contribution of each GFR to beta diversity (SCBD). The relationship between the number of GFR (Functional richness - RF) on the LCBD was also evaluated. For this, it was analyzed data collected in years with extreme drought (2000-2001) and flood (2010-2011) from three sub-basins of the upper Paraná River floodplain were used, which have different damming effects (presence, indirect influence, and absence). Nutrient concentrations and pH influenced the beta diversity in the three sub-basins in the two periods. Extreme drought periods and the presence of a dam were related to higher values of LCBD and RF. High LCBD values were related to low RF values. Environments with the absence and indirect influence of the dam had higher RF values in the flood and higher LCBD values in the drought. GFR H1 (N-fixing cyanobacteria), Lo (large mucilaginous cyanobacteria), and P (filamentous diatoms) presented the greatest contribution to beta diversity. The damming region was related to filamentous cyanobacteria in the drought. The results showed that both damming and climatic periods influenced the contribution of sites to regional diversity. However, they also suggested that the greatest biotic uniqueness observed in the damming region and in the dry period was related to organisms that can affect water diversity and quality, such as cyanobacteria. It appears that these environments have unique environmental and biotic conditions that require greater attention in terms of monitoring to prevent the proliferation of organisms with toxigenic potential. The construction of dams in search of energy security, associated with the predicted scenario of an increase in extreme events, favors biotic uniqueness. Understanding how communities respond to these changes is crucial for the ecology of aquatic environments.