The biogeochemistry of marine dissolved organic carbon, -nitrogen and –phosphorus (DOC, DON or DOP) were extensively studied in the recent past. In contrast, our knowledge on the quantity, distribution and biogeochemical role of DOS in the ocean is very limited. The predominance of sulfate in the ocean, which exceeds the concentration of DOS by five orders of magnitudes, is the major analytical challenge. Our research aim was to quantify and chemically characterize marine DOS. We studied dissolved organic matter in the upper water column of the East Atlantic and the Atlantic sector of the Southern Ocean. DOS was quantified in solid phase extracts using inductively coupled plasma mass spectrometry (ICP-MS). Based on extraction efficiencies of 5-15% (as determined for peat water samples) we calculated DOS concentrations of 0.82-2.01 µM in the East Atlantic and 0.60-1.11 µM in the Southern Ocean. DOC/DOS ratios in the extracts ranged between 157-272 in the East Atlantic and 235-297 in the Southern Ocean. For the molecular characterization of DOS, the DOS concentration was linked to the compositional information derived from ultrahigh resolution mass spectrometry (FT-ICR-MS).