Dynamics of the sedimentary bacterial communities in a plain river network: similar coalescence patterns with bacterioplankton communities driven by distinct assembly processes

Abstract

Riverine microorganisms are major players in driving biogeochemical cycling. The dynamics of hydrological conditions have been observed to influence the microbial communities in rivers, but their specific impacts on the coalescence patterns of the bacterial communities remain largely unexplored. In this study, we examined the dynamics of the sedimentary bacterial communities and their coalescence patterns with bacterioplankton communities in a plain river network under dynamic hydrological conditions. Our results revealed significant temporal variations in the diversity, structure, and taxonomic composition of the sedimentary bacterial communities across the wet, normal, and dry seasons ( P < 0.01). Despite the varying hydrological conditions, similar coalescence patterns were observed between the sedimentary bacterial communities and bacterioplankton communities. The bacterial communities from the same habitat type showed higher proportions of overlapped species, and the coalescence was more prominent within the same medium (intra-medium) compared to that between different media (inter-medium). However, the proportions of stochasticity in community assembly were distinct during different hydrological conditions, with evidently increased stochasticity observed in the wet season compared with other seasons. These results implied that the similar coalescence patterns between the sedimentary bacterial communities and bacterioplankton communities were driven by distinct assembly processes. The results of this study expanded our understanding of microbial coalescence in a river network and might shed light on how microbial communities are assembled in river ecosystems. IMPORTANCE Microorganisms play important roles in driving the biogeochemical cycles within river ecosystems. It has been suggested that hydrologic conditions could influence microbial communities in rivers, but their specific effects on the behaviours of microbial coalescence have not been thoroughly investigated. In this study, the dynamics of sedimentary bacterial communities within a plain river network were analyzed by amplicon sequencing followed by several ecological models to uncover the underlying assembly processes. Additionally, a comparative analysis between bacterioplankton communities and sedimentary bacterial communities was performed to unveil their coalescence patterns. The results suggested that similar coalescence patterns between sedimentary bacterial and bacterioplankton communities were driven by distinct assembly processes under dynamic hydrological conditions. These findings enhanced our understanding of microbial diversity features within river ecosystems.