The Department of Earth Sciences at Utrecht University, Utrecht, and the Department of Microbiology at Radboud University, Nijmegen, in the Netherlands have an opening for two fully funded PhD projects to work on the ERC Synergy project MARIX for 4 years. MARIX stands for 'Methane and Ammonium Removal In redoX transition zones'. The project focuses on the discovery of new microbial and geochemical pathways of removal of methane and ammonium in sediments and the water column of coastal marine systems.