The NEXUS-MONARC project proposes a set of capacity building actions targeting to advance the profile of staff at the department of geology and geoenvironment and collaborating groups at the National and Kapodistrian University of Athens. Through these actions, a holistic approach to environmental monitoring will be developed for the marine environment of the Hellenic Volcanic Arc in the Mediterranean Sea, an environment that is influenced by multiple stressors of anthropogenic and natural origin, such as maritime transport, fisheries, industrial tourism, volcanic activity, hydrothermal venting, and others. The project objectives will be achieved through transferring knowledge and best practices based on the extensive expertise of partner institutions and by orchestrating citizen science activities. Short scientific missions synchronized to citizen science activities will lead to the development of novel collaborative research projects for the coordinating and partner institutions. Furthermore, twinning activities will incite local and international stakeholders from public, policy, and industry to participate and contribute to educational and scientific actions, thus actively improving the marine environment and protecting its inhabitants. Owing to training and collaborative actions, the improved administrative and management practices of the NEXUS-MONARC will be readily applicable to other multi-stressor marine environments in the world.