Microbial communities, or consortia of microorganisms including bacteria, archaea and fungi, inhabit a wide range of freshwater niches and drive, or contribute to, many important ecosystem processes such as river metabolism, pollutant fate and transport, nutrient cycling and geomorphology. Changes to the river microbiome could thus alter function with consequences for resilience of the system (in the context of climate change) or provision of ecosystem services. With the advent of sequencing techniques there has been an upsurge in the number of articles, largely in the biological literature, that investigate spatio-temporal patterns in river microbiomes and posit possible reasons for observed patterns. Some catchment-scale longitudinal studies have revealed shifts in composition and diversity from headwaters to estuary for both bacteria and fungi, and factors such as water and sediment chemistry, land use and season have been reported to shape the river microbiome. Hydrological and geomorphological drivers are highly pertinent: geology, water depth, residence time, mixing of water bodies with different chemical signatures and hydrological regime and connectivity have all been found to correlate with riverine microbial community structure.

The aim of the session is to provide a forum for researchers to present and discuss river microbiome research and consequences for ecosystem function, with a focus on using current and emerging, innovative interdisciplinary techniques and frameworks. We aim to foster links between scientists from different disciplines, particularly microbial ecology, hydrology and geomorphology. We invite contributions from researchers working in riverine systems and across the aquatic-terrestrial interface, who are investigating patterns of microbial structure and function, and their hydrological and geomorphological drivers.Thus particularly welcome are cross-disciplinary contributions (for example, utilizing residence time techniques, source apportionment or hydrograph separation in parallel with biological data) and ecology-focused contributions applying emerging frameworks (such as dendritic network perspectives or community coalescence).