Molecular level studies on the distribution and fate of organic matter at continental margins

Abstract

Continental margins are the dominant reservoir for organic matter (OM) burial in the oceans. However, OM preservation and remineralization is complex due to the variability in OM sources and sedimentation processes. This study combines several geochemical approaches to provide insights into the distribution and fate of recently deposited OM. A rich lipid biomarker and lignin phenol inventory at the NW Iberian margin indicates contributions from various terrestrial and marine sources subjected to different transport mechanisms which result in three different OM provinces on the shelf: (I) the inner shelf region with fresh marine OM, (II) the mid-shelf mudbelt as major sink for terrestrial OM, and (III) the outer shelf with a low OM accumulation. Dissolved organic matter (DOM) in the sediment pore waters was molecularly characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and reflected source variations and early diagenetic processes; e.g., in the Black Sea the DOM composition suggests distinct reaction pathways depending on the redox conditions.