Samples were collected during three expeditions with RV SONNE between 2014 and 2018 (cruises SO219, SO251 and SO261). Sediment cores were taken by using multicorer and gravity corer.Alkalinity has been analyzed by gran titration of known quantities of pore water sample by addition of HCl on a micro stirring device. The accuracy of this method was better than 0.2 mM (data not shown). Dissolved iron (Fe2+) concentrations were analyzed photometrically at wavelength of 565 nm with a Hach Lange DR 2800 Photometer. Dissolved ammonium (NH4+) was detected using the PTFE tape gas separator technique. Dissolved Manganese concentrations were analyzed in acidified samples with an inductively coupled plasma optical emission spectrometer (ICP-OES; Varian Vista PRO). The precision was better than 3 % with a detection limit of 0.04 µM. Sulfate (SO42-) concentrations were determined by ion chromatography (Metrohm 861 Advanced Compact IC, Metrohm A Supp 5 column, 0.8 mL min‑1, conductivity detection after chemical suppression) in samples diluted 1:40 with Milli-Q-grade H2O. Dissolved methane (CH4) concentrations were analysed following the headspace method. For samples from the Japan Trench we used an Agilent Technologies 6890N gas chromatograph equipped with a flame ionization detector, while samples from Atacama Trench site GeoB22908 a ThermoFinnigan Trace gas chromatograph equipped with a flame ionization detector and a Carboxen-1006 PLOT fused-silica capillary column (0.32 mm by 30 m; Supelco, Inc., USA) was used. The stable carbon isotopic composition of methane in four samples from the Atacama trench was determined by duplicate analysis using a Trace GC Ultra coupled to a Delta Plus XP isotope ratio mass spectrometer via a GC Combustion III interface (all ThermoFinnigan). Information on the calculation of flux rates are given in the supplements.Solid phase iron and manganese concentrations is sediments of core GeoB22908-2 were measured using the high-resolution (1 cm) semi-quantitative XRF (X-ray fluorescence) Avaatech at MARUM, performed with an excitation potential of 10 kV, a current of 250 mA and 30 s counting time. Scans were calibrated with quantitative XRF measurements on discrete samples using a PANalytical Epsilon3-XL XRF spectrometer equipped with a rhodium tube, several filters and an SSD5 detector and certified standard materials (e.g., GBW07309, GBW07316 and MAG-1). Scans of the bulk (Gamma Ray) density were conducted with a Multi-Sensor Core Logger (MSCL; GEOTEK®) at MARUM. The MSCL was equipped with a line scan camera for high-resolution core image acquisition.Accelerator Mass Spectrometry measurements (AMS) of radiocarbon (14C) ages on TOC of samples from core GeoB22908-1 were carried out in the MICADAS radiocarbon laboratory at Alfred-Wegener Institute (AWI), Germany. 14C bulk ages are uncalibrated.A programmed pyrolysis method (Hawk instrument, Wildcat Technologies, USA) at the Lithospheric Organic Carbon Lab (LOC) of the Department of Geoscience, Aarhus University, was used to measure TOC and the reactive organic carbon content in freeze-dried sediment samples. The Rock-Eval 6 heating method was applied, in which 50 mg dry sample is subject to a two-step, programmed pyrolysis (heating in an inert atmosphere) and oxidation heating cycle. During the pyrolysis step, the sample is heated to an iso-temperature of 300°C for 3 minutes and then ramped up (25°C min-1) to 650°C. The total concentration of the hydrocarbons and organic-derived fractions of CO, and CO2 that are released during the pyrolysis step (pyrolysable organic carbon wt% released from 300-650°C) are believed to constitute the “reactive organic carbon” content of the organic matter in a sample. The sample is then automatically transferred to the oxidation oven in which both the residual organic matter and mineral carbon are combusted between 400°C to 850°C. The “residual organic carbon” (RC wt.%) is the content of the residual organically-derived CO and CO2 during the oxidation heating stage. The reactive organic carbon represents the fraction of carbon that is released due to thermal decomposition kinetics of organic matter and hence is considered chemically reactive compared to the refractory “residual organic carbon”. The sum of the reactive organic carbon and residual organic carbon is equivalent to TOC.TOC/N values in the Atacama trench core GeoB22908-2 were analyzed from freeze-dried homogenized sediment of each sampling interval. In brief, 3 g of the sediment was decalcified by the addition of 10 % HCl followed by repetitive washing steps with ultrapure water. For TOC/N determination, 10–30 mg of the dried sediment was weighed into tin capsules and analyzed via a Thermo Scientific Flash 2000 elemental analyzer connected to a Thermo Scientific Delta V Plus IRMS.