A systematic typology and synthesis of aquatic refuges in freshwater ecosystems

Aquatic refuges play a crucial role in ecosystem resilience because they can provide suitable conditions for species during periods of environmental stress. This is particularly important as freshwater ecosystems are highly vulnerable to global change drivers, including extreme hydraulic and thermal variations, pollution and the fragmentation of species ranges. Despite their importance, the identification and characterization of refuges remain limited by the lack of a unified conceptual framework and clear operational definitions. To provide a reproducible framework for understanding aquatic refuges, we conducted a literature review using the Web of Science databases and the PECO framework aligned with systematic review standards. From 208 papers, we extracted 530 records describing refuge characteristics in freshwater ecosystems, including hydrosystem type, terminology used, qualitative definitions, mitigated threats, protected biota, and key biotic and abiotic factors involved. The analysis highlighted two major conceptual gradients shaping how refuges are interpreted in literature. The first spans refuges defined as context-dependent habitat patches to refuges defined by biotic persistence and functional roles. The second extends from refuges linked to dynamic hydrology and short-term or seasonal survival to those providing thermal stability and supporting long-term persistence. Within this conceptual space, we identified seven types of aquatic refuges -hydrological, climatic, anthropic, biological, thermal, hydromorphological and water quality- each associated with a distinct mitigated threat. Together, these results provide a unified basis for characterizing aquatic refuges and support their integration into freshwater biodiversity management under global change.