Advection and diffusion determine vertical distribution of microbial communities in intertidal sediments as revealed by combined biogeochemical and molecular biological analysis

► Combination of intact polar lipid analysis and molecular biological techniques. ► Burial and advection supply fresh marine organic matter to upper tidal sand flat. ► Algae and cyanobacteria serve as nutrients for heterotrophic microbes. ► Dominance of bacteria, with constant proportion of methanogenic archaea. ► Nutrient limitation due to diffusion causes bacteria to adapt their membranes.