Effects of multiscale environmental variables on the taxonomic and functional structures of riverine microeukaryotic...

Research on the impact of multiscale complex environmental variables on the structure and function of aquatic communities is currently at the forefront, yet the gene regulatory mechanisms of aquatic communities remain poorly understood. In this study, we investigated the Yongding River watershed, a model system exhibiting pronounced environmental factors across "mountain-plain-coastal" sections and three spatial scales of "basin-reach-site". Through integrated eDNA metabarcoding and metatranscriptomics, we revealed that environmental factors at different scales significantly influence riverine microeukaryotic plankton community composition and functional genes expression profiles, which may be related to basin- and reach-scale variables indirectly influencing site-scale physiochemical conditions. Under multiscale environmental gradients, community composition and functional genes expression differed across mountain-plain-coastal sections, but genes expression demonstrated remarkable spatial stability than community composition. Cross-scale environmental factors similarly impacted community composition, functional genes expression, and biogenic element metabolism, or differently influenced them in varying ways. At each scale of "basin-reach-site", the sensitivity of community composition and functional genes expression varied in their responses to different environmental factors. This decoupling of taxonomic and functional responses highlights the complexity of community-environment interactions across spatial hierarchies. This study develops a novel framework that integrates meta-omics signatures derived from environmental samples with cross-scale environmental drivers in aquatic ecosystems, effectively bridging micro-scale molecular responses with macro-scale ecosystem patterns.