This baseline dataset comprises downcore measurements of pore-water nutrients, cations and DIC for a sediment core (ROV-operated PUC) retrieved in the framework of the European collaborative JPI Oceans MiningImpact project onboard R/V SONNE cruise SO268 in 2019. The scientific work during cruise SO268 was part of the second phase of the MiningImpact project (Environmental impacts and risks of deep-sea mining) and is designed to assess the environmental impacts of deep-sea mining of polymetallic nodules in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean. The pore water was extracted onboard by rhizon sampling. Pore-water nutrient concentrations (nitrate, nitrite, ammonium, silicic acid, phosphate) were analyzed onboard on freshly extracted pore water upon 3-fold dilution or undiluted (ammonium) using a QuAAtro continuous segmented flow analyzer (Seal Analytical). Major and minor elements were determined on acidified samples (25 µL double sub-boiling distilled concentrated HCl per 1 mL sample) using ICP-AES (iCAP 7400, Thermo Scientific) and DIC was determined on HgCl2-treated pore-water samples using a QuAAtro continuous segmented flow analyzer (Seal Analytical) at the Marine Geochemistry Lab, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven.