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WP3 Organic Matter

 
 

SabrinaJohann-1Bulk and molecular organic geochemical characterization will be conducted in order to assess the origin and determine the proportion and state of preservation of the different types of organic matter accumulated in the sediments of the lobe zone. Our aim is to provide a detailed picture of the origins, distribution and diagenetic changes using geo- and bio-chemical methods. This characterization is crucial, as the different sources of organic matter (marine vs terrestrial) and their state of preservation (fresh vs degraded) before burial show different ability to be remineralized by the benthic (micro)fauna and bacteria.
Beside this geochemical and biochemical description of organic matter history, our goal is also to develop a more ecological approach of the functional relationship between sedimentary organic matter and the living benthic compartment in this unique ecosystem where heterotrophy and chemosynthesis co-exist. We will characterize the nutritional quality of the organic matter from the lobes using molecular proxies. The transfer of the sedimentary organic carbon into the micro- and macro-fauna will be further traced using lipidic markers and single compound isotopic analyses. This objective will be realized in close coupling with WP5 and will help unraveling the link between organic matter quality, processes of microbial degradation and macrofaunal assemblages.

Photo1 webstite WP3-1Bulk information on the quantity, type, and preservational state of the organic matter will be obtained by different methods: Rock-Eval pyrolysis, elemental analyses, C and N stable isotopic measurements, radiocarbon measurements (14C) of bulk and molecular compounds.Furthermore, the molecular composition of the lipid and proteic classes will be determined by GC-FID, GC-MS and HPLC. The lipidic biomarkers (fatty acids, alkanes, sterols, alcohols and isoprenoids…) will provide a more precise description of the origin of the organic matter, and will allow assessing the importance of terrestrial and marine organic matter inputs, the contribution of bacterial biomass, as well as the reactivity of recently deposited organic matter. Lignin products and their δ13C isotopic values will be used as complementary biomarkers of both terrigenous organic matter sources and their state of diagenesis. Information on the degree of lability of the proteacinous material, its nutritional quality and its state of degradation will be obtained from total hydrolysable amin aocids (THAA) and enzymatically hydrolysable amino acids (EHAA).

Team:

Coordinator: François BAUDIN

  • UPMC-Univ. Paris 6: François BAUDIN (iSTeP), François CHARLES (CNRS, LECOB), Laurence MEJANELLE (LECOB), Audrey PRUSKI (LECOB), Béatrice RIVIERE (CNRS, LECOB), Florence SAVIGNAC (iSTeP), Johann SCHNYDER (iSTeP), Claire SENYARICH (LECOB), Elsa STETTEN (PhD Student), Gilles VETION (CNRS, LECOB)
  • Univ. Bordeaux 1: Karine CHARLIER, Philippe MARTINEZ, Loïc THIAO-LAYEL
  • LSCE: Nadine TISNERAT-LABORDE
  • Partner: Ming Yi SUN (Univ Georgia, USA)

All these geochemical and biochemical results will be faced up to the ecological results produced by WP5 and the carbon recycling parameters determined by WP4.