Description: The main objective of the RV Sonne cruise SO270 was to test the hypothesis that Saya de Malha Bank (SMB) is a carbonate platform controlled by water mass boundaries and currents which exert a strong control on sedimentation, ecosystems and biogeochemistry. The proposed project 'Saya de Malha Bank Carbonate Geochemistry – MASCARA Geochemie' contributes to the overarching goal by characterizing the biogeochemical properties of water masses in order to estimate the impact of water masses on the aragonite and calcite saturation state. To achieve the project aims, carbonate chemistry was determined in surface waters by using an underway system (SUNDANS and VINDTA 2C, both instruments are from Marianda, Kiel, Germany). Furthermore, a CTD/Rosette sampler and a multi-corer (MUC ) was used to sample the water column and pore water whereas in addition pore water also the MUC-supernatant was sampled. The underway data include: salinity, sea water temperature, fugacity of CO2 (fCO2) concentrations of dissolved oxygen, chlorophyll (fluorescence) and total alkalinity (TA). Concentrations of nutrients (PO43- and SiOH4-), total dissolved inorganic carbon (DIC) and TA were determined in water samples obtained from CTD/Rosette sampler and within the MUC-supernatant, by using a SKALAR SAN plus System/08529 and a VINDTA 3C system (#29, Marianda, Kiel, Germany). Pore water nutrient concentrations (NOx, NO2-, NH4+, PO43- and SiOH4-) were measured by using a TECANinfiniteF200pro.