| Summary: | Ex situ nutrient fluxes at the sediment water interface were assessed on the Northeast Greenland shelf with R/V Polarstern during PS109 between September and October 2017 using a camera-equipped multiple corer (TV-MUC; core area 0.007 m²). Upon arrival on deck, part of the overlying water of three MUC cores was collected and stored separately at in situ temperature. The remaining overlying water was adjusted to 10 cm above the sediment by gently pushing the sediment upwards while avoiding a disturbance of the surface sediment. The cores were then placed in a temperature-controlled water bath in the ship-board laboratory which had been adjusted to the in-situ temperature at the seafloor (information was retrieved from ship-board sensors). A magnetic stirrer was deployed in order to homogenise the overlying water, and a small air pump gently aerated the water. After the assessment of diffusive oxygen uptake (DOU) by microprofiling (see abstract on DOU data), total nutrient fluxes were measured. The air pump was removed to ensure no air bubbles in the overlying water, and the cores were closed air tight. The overlying water was sampled at start and end of the incubation that lasted approx. 48hours (at least 36h). The incubation was terminated at ≤ 80 % initial [O{~}2{~}]. Water samples of 10 ml were filtered over a GF/F filter and stored at -20°C until analysis in the home laboratory using Continuous Segmented Flow Analyser, SEAL Analytical, QuAAtro39. Total sediment nutrient flux was determined as the change in nutrient concentration in the water phase.
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