Felix Janssen's scientific work focuses on microbially-driven biogeochemical processes in marine sediments with emphasis on organic matter remineralization and oxygen fluxes. He has a strong interest in the application and further development of state of the art technologies for in situ studies of biogeochemical processes in the marine environment. In a number of projects, Felix studied effects of environmental changes relating to global change or direct anthropogenic impacts on microbial activity and biogeochemical processes. Since several years, he is working on observations of environmental consequences of deep sea mining as part of the EU project MIDAS and the JPI-O project MiningImpact. In addition to baseline studies in different manganese nodule ecosystems the work focused on Benthic Impact Experiments in the DISCOL experimental area in the Peru Basin and an independent scientific monitoring of the first industrial pre-prototype nodule collector test in the Clarion Clipperton Fracture Zone.