An ecohydrological typology for thermal refuges in streams and rivers

Abstract

Thermal refuges are thermally distinct riverscape features used by aquatic organisms during unfavourable thermal events, facilitating resilience in marginal environments. However, the thermal refuge concept is nebulous, and the often interchangeable use of the term ‘thermal refugia’ creates additional ambiguity. We argue that lexical differences resulting from divergent scholarly trainings hinder holistic understanding of thermal refuges; thus, existing studies would benefit from a structured framework for thermal refuge conceptualization. Herein, we articulate an ecohydrological typology for defining and characterizing thermal refuges in streams and rivers by identifying key hydrological and thermal characteristics and variations in ecological function described in the literature. We use concepts that are easily definable, measurable and transferable across disciplines, riverscapes and species to discriminate among thermal refuge types. Future work can use our typology as a basis for more informed interdisciplinary discussion and interpretation of thermal refuges' role in riverscapes through more hypothesis-driven research and conservation-focused management.