Environmental variability drives the spatial and temporal beta diversity of phytoplankton in a tropical reservoir

Aim The aim of this study was to evaluate the local contribution of phytoplankton to beta diversity across space and time in a reservoir in central-western Brazil, and its relationship with environmental filters. Methods We sampled phytoplankton and environmental variables over three months of drought and three months of rainfall at seven sampling sites along the main axis of the João Leite Reservoir, Goiás, Brazil. We used Euclidean distance to calculate spatial and temporal environmental heterogeneity. We applied the Local Contribution to Beta Diversity (LCBD) index and the Temporal Beta Diversity (TBI) index. Results Principal Component Analysis revealed a clear separation between lotic and lentic environments. A longitudinal gradient of environmental heterogeneity was formed in the reservoir. The local contribution to beta diversity was primarily structured by species turnover rather than richness differences. Through TBI values, we observed the influence of seasonality, leading to a trend of declining species diversity from the dry to the rainy period. Using Beta Regression, we found a significant relationship between environmental heterogeneity and LCBD values, particularly in the species turnover component. For TBI, we identified a significant relationship with temporal environmental heterogeneity between the last month of drought and the first month of rainfall. Conclusions Therefore, it is essential to consider different spatial and temporal scales when monitoring diversity in reservoirs, as ecosystems may encompass varying characteristics that influence the provided ecosystem functions and services.