Our view of the marine nitrogen (N) cycle has changed dramatically during the last decade; new processes have been identified, rates had been revised and the occurrence and the role of microbial organisms has been described. The aim of the session is to bring together scientists from the various disciplines working on different aspects of the marine N cycle in order to gain an overview about the most recent developments relevant for global rate estimates and quantification of sources and sinks in the marine N cycle. We welcome presentations on processes and flux estimates of all aspects of the marine nitrogen cycle: Relevant topics include nitrogen processes (e.g. nitrification, denitrification, anammox, N2 fixation etc.), flux estimates of N aerosol input and N2O air-sea exchange as well as molecular genetic approaches to identify the organisms (bacteria, archaea) and quantify their role in the marine N cycle.