Legacies of temperature fluctuations promote stability in marine biofilm communities

The climate crisis entails more frequent and intense extreme events, driving major changes of biodiversity in many ecosystems. However, to what extent such climate legacies will determine the response of ecological systems to future perturbations remains poorly investigated. Here, we tracked taxon and trait dynamics of a rocky intertidal biofilm community under contrasting experimental regimes of warming (constant vs. fluctuating) and assessed how such modifications affected multiple stability dimensions - resistance, resilience, and temporal stability - in response to subsequent extreme temperatures. Contrary to prevailing expectations, exposure to relatively constant warming enhanced the resistance of biofilm to extreme temperatures by promoting the diversity and functional redundancy of stress-tolerance traits. In contrast, high warming variability boosted resilience via selection of fast-growing taxa at the expense of functional redundancy. Anticipating the challenges posed by future extreme events, our study provides a forward-looking perspective, shedding light on the stability and adaptability of microbial communities in the face of ongoing climatic change.