Seabed sediment data (upper 6 cm) on grain size, water content, total nitrogen, total carbon, total organic carbon, total inorganic carbon, carbon and nitrogen isotopic composition from the Nansen Legacy seasonal cruise 2019706 (Q3).

This dataset includes contents of water content, total nitrogen (TN), total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), and carbon and nitrogen isotopic composition (d13C, d15N) in marine sediments. Samples were collected during the Nansen Legacy cruises in March as part of cruise 2019706 (Q3) in the northern Barents Sea. Sediment material was subsampled from three replicate deployments of a giant box corer at six stations (P1 to SICE4). The samples were immediately sliced into 1 cm layers (0 - 6 cm) and placed into plastic jars, and frozen on board. All samples were freeze-dried under vacuum in the laboratory and homogenized. Elemental analysis of carbon and nitrogen concentrations was undertaken with an Elemental Analyser - Isotope Ratio Mass Spectrometry (EA - IRMS; Iso-Analytical Ltd., UK). Before d13C analysis, samples were acidified with 1M HCl and left overnight to allow the inorganic carbon to be liberated as CO2. The samples were then neutralized by repetitively washing with distilled water and oven drying at 60 degrees Celsius. The standards d13CV-PDB (Vienna PeeDee Belemnite) and d15NAIR (atmospheric N2) were used as references for the carbon and nitrogen isotope values, respectively. The measured TOC content was corrected for weight loss upon acid washing, TIC content was calculated by subtracting TOC from TC. Grain size distribution of non-acidified samples was assessed with a Beckman Coulter LS 13 320 Particle Size Analyser. The organic matter was removed with 10 % H2O2, and deflocculated with a 5 % Calgon solution (sodium hexametaphosphate and sodium carbonate) in an ultrasonic bath prior to analysis. The particle diameter within the 0.04–2000 μm range was measured at 0.004 μm resolution.