Marine sediments contain abundant and diverse microbial communities critical to the functioning of marine ecosystems. This high diversity can be as an adaptive strategy for survival microbial as a response to dynamic environmental conditions in sediments. Amplicon sequencing studies based on single-gene surveys allow us to address the phylogenetic diversity of sediment microbial communities, but only with metagenomic analyses can we couple diversity to the functional potential encoded within sedimentary communities. This functional potential is particularly important in regards to carbon and nitrogen cycling, where benthic microbes play an essential role. In ecosystem heavily affected by eutrophication, like the Baltic Sea, microbial-driven processes like nitrate reduction and carbon sequestration are critical to mitigate anthropogenic pressures. How the metabolic potential of microbes to perform this functions is determined by the strong environmental gradients present in the Baltic Sea and associated filtering is not known. This project will take advantage of large spatial scale time series of Baltic Sea samples to address these questions.