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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 5
Biogeosciences, 8, 1351–1366, 2011
https://doi.org/10.5194/bg-8-1351-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Biogeochemical fluxes in River-dominated Ocean Margins (RiOMars):...

Biogeosciences, 8, 1351–1366, 2011
https://doi.org/10.5194/bg-8-1351-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 27 May 2011

Research article | 27 May 2011

Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

L. Pastor1,*, C. Cathalot2,*, B. Deflandre1,3, E. Viollier1, K. Soetaert4, F. J. R. Meysman4, C. Ulses5, E. Metzger6, and C. Rabouille2 L. Pastor et al.
  • 1Univ. Paris Diderot, Sorbonne Paris Cité, Institut de Physique du Globe de Paris, UMR7154 CNRS, 75013 Paris, France
  • 2Lab. des Sciences du Climat et de l'Environ., CEA-CNRS UMR 1572, Av. de la Terrasse, 91198 Gif sur Yvette, France
  • 3UMR5805 EPOC – OASU, Université Bordeaux 1 – CNRS, Avenue des Facultés, 33405 Talence cedex, France
  • 4NIOO-KNAW, Centre for Estuarine and Marine Ecology, Korringaweg 7, 4401 NT Yerseke, The Netherlands
  • 5Laboratoire d'Aérologie, CNRS et Université de Toulouse, 14 avenue Edouard Belin, 31400 Toulouse, France
  • 6Laboratoire des Bio-Indicateurs Actuels et Fossiles, UPRES EA 2644, UFR Sciences 2 bd Lavoisier, 49045 Angers Cedex 01, France
  • *These authors contributed equally to this work.

Abstract. In situ oxygen microprofiles, sediment organic carbon content, and pore-water concentrations of nitrate, ammonium, iron, manganese, and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) the organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11–33 yr−1); (2) the burial efficiency (burial/input ratio) in the Rhône prodelta (within 3 km of the river outlet) can be up to 80 %, and decreases to ~20 % on the adjacent continental shelf 10–15 km further offshore; (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates; (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (>97 %) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River-dominated Ocean Margins (RiOMar) environments.

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