Marine sediments, like terrestrial soils, are sites of rapid recycling of organic matter and are home to diverse and active microbial communities. The microbially-mediated processes that occur in sediment recycle critical elements like carbon, nitrogen, and phosphorus and in the process, produce climate-active trace gases like carbon dioxide, methane, and nitrous oxide. Microbial processes occurring in sediments act as filters, removing pollution-derived components from the surface waters flowing over them and from the ground water flowing through them. Sediment microbial communities are strongly regulated by the physical and geochemical conditions characterizing the habitat. Our work aims to understand the interactive feedbacks between physical, geochemical, and microbial processes that ultimately regulate elemental cycling in sedimentary habitats.