Summertime sadness? Not for diatoms

In the context of ongoing climate change and global warming, drought events have occurred more frequently, especially in mountain ecosystems, representing an important and alarming factor shaping ecosystems and biotic communities. Here we investigated the seasonal fluctuations in physical and chemical factors and the effects of summer drought on diatom α and β diversity in temporary ponds of a mountain plateau. Overall, no significant differences emerged for taxonomic α diversity indices. Similarly, functional diversity showed no significant seasonal fluctuations. Functional evenness was significantly higher in autumn compared to summer (W = 69, p = 0.0018). RDA analysis explained a substantial portion (90%) of the variation in taxonomic α diversity in autumn (F = 9.27, p = 0.025; Temperature, F = 19.68, p = 0.015; Resistivity, F = 8.02, p = 0.049). PERMANOVA analysis showed no significant differences in taxonomic (R² = 0.039, p = 0.774) and functional (R² = 0.104, p = 0.159) β diversity among seasons. Multilevel pattern analysis highlighted significant differences for intermediate cell volume trait (BioVol_c2) (p = 0.004), being more represented in summer than in autumn. This study highlighted diatom communities resilience to droughts in high elevation ponds, with seasonality emerging as an important factor.