Sediment core and pore water data for AL557

Sediment cores and pore water cores were taken in the Skagerrak and North Sea with a multicorer on cruise AL557 (June 2021). The sediment cores were sliced onboard into 1 cm slices and frozen directly (-20°C). Pore water samples were taken with rhizon samplers (0.15 µm pore size, CSS; Rhizosphere, Netherlands) from intact sediment cores and frozen directly (-20°C). In the laboratory, the sediments were freeze-dried, sieved (<2mm) and milled. For organic carbon (after acidification) and total carbon and nitrogen contents, the samples were analyzed using an Euro EA 3000 (Euro Vector SPA) Elemental Analyzer, delta 15N was measured with a FlashEA 1112 elemental analyzer coupled to a MAT 252 (Thermo Fisher Scientific) isotope ratio mass spectrometer (https://doi.org/10.1016/j.orggeochem.2009.05.008; lab 3). For trace metal analysis, the sediments were digested with HBF4+HNO3+HCl (https://doi.org/10.1039/D0AY01049A) and the pore water samples were acidified with HNO3 prior to 10-fold dilution with HNO3. Trace elements were measured by ICP-MS/MS (Agilent 8800, Agilent Technologies, Japan).