Assembly and succession of groundwater microbial communities during sediment colonization

In this project we studied the ecological processes behind the assembly and succession of microbial communities during the colonization of groundwater sediments. We followed the microbial colonization of sterile sediments in in situ microcosms that were exposed to groundwater for almost one year at two hydrologically connected sites of a shallow, porous aquifer. We used spatiotemporally resolved 16S rRNA amplicon sequence data to study changes in alpha and beta diversity over the course of the colonization, and applied null models to address the impacts of stochastic and deterministic forces on the initial community assembly, temporal community turnover, as well as the exchange of OTUs between the sediments and the surrounding groundwater over the successional stages of the colonization. Our study shows that the microbial colonization of groundwater sediments follows similar successional patterns as reported for developing biofilms in non-subsurface habitats, and that deterministic forces have a pronounced effect on this process.