For ex situ total oxygen uptake (TOU) measurements, sediment cores recovered by a MUC were used. The sediment cores were closed airtight with no air bubbles in the overlying water. The distance between the SWI and the edge of the lid was measured for volume calculations of the overlying water. An optical oxygen microsensor (Pyroscience, Aachen, Germany) with a tip size diameter of 50 µm was installed in the lid, allowing a continuous measurement of the oxygen concentration in the overlying water. The sediment cores were incubated in darkness for >40 h and the overlying water was kept homogenised by rotating magnets over that period. For in situ TOU measurements, benthic chambers (K/MT 110, KUM, Kiel, Germany) with an inner dimension of 20x20 cm were used. These chambers were attached at autonomous benthic lander and were pushed into the sediment and thereby enclosed a sediment volume of approximately 8 L and an overlying water volume of approximately 2-3 L. The oxygen concentration was measured in the overlying water continuously with an Aanderaa optode (4330, Aanderaa Instruments, Norway, two-point calibrated as described in the upper section) over an incubation period of 20-48 h. During the measurement, the overlying water was kept homogenised by a stirring cross at the inner top of the chamber. TOU from both ex situ sediment core and in situ benthic chamber incubations were calculated using TOU = dO2 x V/ dt x A, in which dO2, dt, V and A represent the difference in oxygen concentration, the difference in time, the volume of the overlying water and the enclosed surface area, respectively.