Methane (CH4) is the most frequent organic compound in the atmosphere and its influence on the global climate is subject of currently conducted scientific discussion. One source of atmospheric methane is the release of CH4 from the oceans seafloor. These submarine sources are characterized by rising gas bubbles or diffusive methane flux into the water column. Due to the limited number of samples taken by conventional ex situ methods, an accurate quantification of the methane distribution could hardly be estimated. With the help of an optimized mass spectrometer (UWMS, Inspectr200-200, Applied Microsystems Limited™) it became possible for the first time to obtain distribution patterns of dissolved CH4 and other gases in the water column in high resolution. In this talk I will present the detection, mapping and inventory calculation of submarine released methane by novel in situ mass spectrometry as well as the study of relevant pathways and its potential contribution to the atmospheric methane budget.