660 Pg of carbon is globally stored in marine dissolved organic matter (DOM). This refractory DOM (RDOM) is stable on millennial timescales and contributes to oceanic carbon storage. Dissolved organic sulfur (DOS), as part of the marine DOM, is mainly derived from primary production with contributions of DOS through pore water discharge from abiotic sulfurization in sulfidic environments such as intertidal flat sediments. However, questions remain about the stability of DOS from sulfidic environments once discharged into the water column and how different DOS sources can contribute to the long-term carbon storage as oceanic RDOM. In this project, we use the North Sea as an ideal system for studying DOS formation and fate from various sources, including phytoplankton, porewater as well as riverine outflow, and ultimately, DOS export to the North Atlantic Ocean. Water column and porewater samples were acquired during a research cruise in addition to seasonal intertidal flat, and river sampling (Weser, Ems, and Elbe Rivers). Our quantitative stoichiometric and molecular composition (FT-ICR-MS) analyses of solid-phase extracted DOM revealed non-conservative mixing behavior of carbon-to-sulfur ratios with salinity in the North Sea suggesting export of DOS-enriched porewater from the sulfidic intertidal flats. Our ongoing analyses aims at identifying characteristic DOM molecular fingerprints to trace the different riverine and porewater sources and to constrain the export of DOS to the North Atlantic Ocean.

Primary Presenter: Wiebke Freund, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany (wiebke.freund@uol.de)

Authors:

Wiebke Freund, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany  (wiebke.freund@uol.de)

Thorsten Dittmar, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany  (thorsten.dittmar@uni-oldenburg.de)

Tina Sanders, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany   (tina.sanders@hereon.de)

Philipp Böning, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany  (p.boening@uni-oldenburg.de)

Michael Seidel, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany  (m.seidel@uni-oldenburg.de)