Species Matter: Aquatic Fungal Richness and Identity Enhances Recovery From Drying Events

ABSTRACT The increasing human population growth raises water demand, while global change brings additional challenges, such as higher temperatures, nutrient enrichment and altered precipitation patterns. These shifts can lead to stream flow interruptions and eutrophication, which can affect biodiversity and disrupt stream ecosystem functioning. Aquatic fungi are key players in freshwater ecosystems, mainly due to their role in organic matter decomposition, nutrient cycling and energy transfer to higher trophic levels. Despite their importance, little is known about how aquatic fungal communities recover from environmental stress. This study aims to investigate the role of fungal diversity (species richness and identity) in the recovery of aquatic fungal communities following drying events, both alone and in combination with other abiotic stressors. We used a microcosm approach to simulate drying events and assess the recovery of aquatic fungal communities under four stress scenarios. Microcosms were exposed to increased temperature and/or nutrient levels throughout the entire experiment, including colonisation, drying and recovery phases. This resulted in four treatments: drying alone, drying with increased temperature, drying with increased nutrient levels and drying with both increased temperatures and nutrients. We also tested whether the presence of other fungal species affected recovery dynamics. Fungal species exhibited different recovery capabilities, suggesting species‐specific tolerance to a range of stress conditions. Across all treatments, overall recovery measured by their reproductive ability was delayed under abiotic stress. This delay indicates potential shifts in community composition, which could impair ecosystem functioning and reduce the potential for natural recovery. Our results showed that abiotic stress not only slows fungal recovery but also alters community dynamics, potentially reducing ecological stability. Moreover, the presence of certain fungal species facilitated the recovery of others, emphasising the role of fungal interactions in enhancing community resilience. This study is among the first to highlight the importance of aquatic fungal biodiversity and species complementarity in buffering freshwater ecosystems against abiotic stress. By demonstrating that higher fungal diversity enhances recovery and supports ecosystem functioning under stress, it reinforces the importance of biodiversity conservation and the management of freshwater ecosystems in a changing world.