Integrating alpha, beta and zeta diversity to explore phytoplankton community stability in Mediterranean lakes

Biodiversity is often associated with ecological stability, yet how biodiversity relates to changes in community dynamics and long-term stability remains unclear, especially for microbial communities. Understanding community dynamics requires metrics that capture both compositional change and long-term persistence. Here, we analysed phytoplankton dynamics in 14 Greek lakes over an eight-year period (2016–2023) using an integrated framework combining alpha, beta, and zeta diversity metrics. Taxonomic richness varied widely among lakes, with shallow polymictic systems supporting significantly higher taxa richness and variability than deep monomictic lakes. Temporal beta diversity revealed moderate to high community dissimilarity across all lakes, driven primarily by species turnover rather than nestedness, indicating that compositional shifts were dominated by species replacement. Lakes with low taxa richness exhibited lower temporal community stability, suggesting reduced buffering capacity against environmental variability. Zeta diversity analysis provided novel insights into long-term persistence, showing a consistent decline in shared taxa with increasing temporal order across all systems. Despite differences in morphology, the rate of zeta decline did not differ significantly between lake types, indicating similar underlying dynamics. However, shallow lakes maintained proportionately larger core communities, reflecting higher annual richness and greater ecological redundancy. Among phytoplankton groups, Chlorophyta and Cyanobacteria were the main components of community structure, turnover, and persistence, whereas Dinophyta exhibited low persistence and high variability, indicating greater sensitivity to environmental fluctuations. These findings demonstrate that integrating alpha, beta, and zeta diversity provides a robust framework for assessing phytoplankton community stability and identifies biodiversity as a sensitive indicator of temporal persistence.