Effects of Hyporheic Water Exchange on Microbial Community Structure and Function: A Case Study in the Beiluo River, Loess Plateau, China

ABSTRACT Microbial communities in riverine hyporheic zones provide essential ecosystem services. However, the mechanisms whereby they respond to hyporheic water exchange under different habitat stress conditions remain poorly understood. Therefore, investigating the impact of riverine hyporheic exchange on the microbial community composition and its potential ecological function is essential, particularly in the seasonal rivers of northern China. To elucidate the structure and function of hyporheic zone sediment microbial communities in response hyporheic exchange and environmental fluctuations, we examined associations by performing in situ falling‐head permeameter tests and eDNA techniques. The primary findings were as follows: (1) We detected variations in the spatial distribution patterns of streambed hydraulic conductivity (range, 0.055–3.490 m/day) and vertical fluxes (range, 1.886–342.0 mm/day) among different monitoring stations. (2) Microbial communities displayed compositional similarities and spatial heterogeneity. Stations with limited vertical exchange were characterised by reduced species diversity. (3) Prokaryotes showed better modularity characteristics with higher stability and functional diversity than eukaryotic communities. (4) Differences in the abundance of microbial metabolism and genetic functions were observed among different habitats. This study emphasises the significance of local hydrological patterns (such as downwelling) in maintaining riverine environmental elements and acting as hotspots for microbial diversity within the hyporheic zone. The heterogeneity of the hydrological patterns governing hyporheic water exchange can explain the abundance, species diversity and biogeochemical processes of microorganisms within this zone.