Grain size distribution drives microbial communities vertically assemble in nascent lake sediments

Sediment microbes are crucial for maintaining biogeochemical cycles in aquatic ecosystems, yet the influence of sediment geophysical structure on microbial communities remains unclear. In this study, we collected sediment cores from a nascent reservoir in its initial stage of deposition and utilized the multifractal model to comprehensively characterize the heterogeneity of sediment grain size and pore space. Our results demonstrate that both environmental physiochemistry and microbial community structures varied significantly with depth, with the grain size distribution (GSD) being the key driver of sediment microbial diversity, as revealed by the partial least squares path model (PLS-PM) method. GSD can potentially impact microbial communities and biomass by controlling pore space and organic matter. Overall, this study represents the first attempt to apply soil multifractal models into the integrated description of physical structure in sediment. Our findings provide valuable insights into the vertical distribution of microbial communities.