Total dissolved organic carbon and total dissolved nitrogen in sediment pore water of the central Arctic Ocean collected during POLARSTERN cruise ARK-XXVII/3 from August-September 2012

During the RV Polarstern cruise ARK-XXVII/3 to the Arctic Ocean in summer 2012, when sea ice declined to a record minimum bottom, water and sediment pore water samples were collected with a TV-guided multicorer at stations in the Nansen and Amundsen basin. 50 ml sediment pore water samples were collected from 0-1, 1-5 and 5-10 cm sediment depths from up to 4 parallel sediment cores at each station. Additionally, overlying bottom waters were carefully collected from undisturbed sediment cores. Acidified pore water samples (pH2) were used for analysis of DOC and TDN concentrations. The measurements were performed by hand injection via catalytic oxidation at high temperature on a TOC-V Shimadzu instrument.

Dissolved organic carbon in sediments of the central Arctic Ocean collected during POLARSTERN cruise ARK-XXVII/3 from August-September 2012

Marine organic matter (OM) sinks from surface waters to the seafloor via the biological pump. Benthic communities, which use this sedimented OM as energy and carbon source, produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. We hypothesized that in the oligotrophic deep Arctic basin the molecular signal of freshly deposited primary produced OM is restricted to the surface sediment pore waters which should differ from bottom water and deeper sediment pore water in DOM composition. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether the signal of marine vs. terrigenous DOM is represented by different compounds preserved in the sediment pore waters and 3) whether there is any relation between Arctic Ocean ice cover and DOM composition. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometer, were correlated with environmental parameters by partial least square analysis. The fresher marine detrital OM signal from surface waters was limited to pore waters from < 5 cm sediment depth. The productive ice margin stations showed higher abundances of peptides, unsaturated aliphatics and saturated fatty acids formulae, indicative of fresh OM/pigments deposition, compared to northernmost stations which had stronger aromatic signals. This study contributes to the understanding of the coupling between the Arctic Ocean productivity and its depositional regime, and how it will be altered in response to sea ice retreat and increasing river runoff.

Organic d13C values, kerogen atomic C/N ratios and relative weights of some kerogen pyrolysis products of ODP Hole 112-682A (Table 1)

Carbon isotopic composition of predominantly marine kerogen in latest Oligocene mudstones of the Peru Margin ODP 682A Hole shows an about 3.5? increase with decreasing age. Py-GC and elemental (C=N ratio) analysis of the kerogen plus sulphur isotopic study together with earlier knowledge on geological setting and organic geochemistry results in a better understanding of depositionary environment and allows to separation of the influence of concentration of water dissolved carbon dioxide (ce) on kerogen delta13C from that of other factors (bacterial degradation, sea surface temperature, DIC delta13C, productivity, and admixture of land plant OM). Based on this analysis, the major part of the kerogen shift is considered as a result of the latest Oligocene decrease of marine photosynthetic carbon isotopic fractionation in the Peru Margin photic zone, which in turn possibly reflects a simultaneous drop in atmospheric CO2 level. Uncertainties in the evaluation of the factors affecting the marine photosynthetic carbon isotopic fractionation and the extent of ocean-atmosphere disequilibrium do not permit calculation of the decrease of the atmospheric CO2.

Total organic carbon, bitumen ratio, hopane and sterane parameters of ODP Sites 128-798 and 128-799

Notable compositional changes of organic matter are observed below the silica transition zone in thermally immature sediments. The increase of bitumen ratio, and hopane and sterane isomerization parameters indicate an acceleration of the kinetics of the chemical reactions which transform the organic matter. This phenomenon is probably due to the numerous mineral and textural changes induced by the transformation of amorphous biogenic silica into crystalline authigenic silica.