Articles | Volume 11, issue 19
Biogeosciences, 11, 5285–5306, 2014

Special issue: The impact of anthropogenic perturbations on open ocean carbon...

Biogeosciences, 11, 5285–5306, 2014

Reviews and syntheses 01 Oct 2014

Reviews and syntheses | 01 Oct 2014

Mechanisms of microbial carbon sequestration in the ocean – future research directions

N. Jiao1, C. Robinson2, F. Azam3, H. Thomas4, F. Baltar5, H. Dang1, N. J. Hardman-Mountford6, M. Johnson2, D. L. Kirchman7, B. P. Koch8, L. Legendre10,9, C. Li11, J. Liu1, T. Luo1, Y.-W. Luo1, A. Mitra12, A. Romanou13, K. Tang1, X. Wang14, C. Zhang15, and R. Zhang1 N. Jiao et al.
  • 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China
  • 2School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
  • 3Scripps Institution of Oceanography, UCSD, La Jolla, CA 920193, USA
  • 4Dalhousie University, Halifax, Nova Scotia, Canada
  • 5Department of Marine Science, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
  • 6CSIRO Marine and Atmospheric Research, Floreat, WA 6014, Australia
  • 7School of Marine Science and Policy, University of Delaware, DE 19958, USA
  • 8Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany
  • 9Sorbonne Universités, UPMC Univ. Paris 06, UMR7093, Laboratoire d'Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
  • 10CNRS, UMR7093, Laboratoire d'Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
  • 11State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
  • 12Centre for Sustainable Aquatic Research, Swansea University, Swansea, UK
  • 13Dept. of Applied Physics and Applied Math., Columbia University and NASA-Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
  • 14South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
  • 15Tongji University, Shanghai, China

Abstract. This paper reviews progress on understanding biological carbon sequestration in the ocean with special reference to the microbial formation and transformation of recalcitrant dissolved organic carbon (RDOC), the microbial carbon pump (MCP). We propose that RDOC is a concept with a wide continuum of recalcitrance. Most RDOC compounds maintain their levels of recalcitrance only in a specific environmental context (RDOCt). The ocean RDOC pool also contains compounds that may be inaccessible to microbes due to their extremely low concentration (RDOCc). This differentiation allows us to appreciate the linkage between microbial source and RDOC composition on a range of temporal and spatial scales.

Analyses of biomarkers and isotopic records show intensive MCP processes in the Proterozoic oceans when the MCP could have played a significant role in regulating climate. Understanding the dynamics of the MCP in conjunction with the better constrained biological pump (BP) over geological timescales could help to predict future climate trends. Integration of the MCP and the BP will require new research approaches and opportunities. Major goals include understanding the interactions between particulate organic carbon (POC) and RDOC that contribute to sequestration efficiency, and the concurrent determination of the chemical composition of organic carbon, microbial community composition and enzymatic activity. Molecular biomarkers and isotopic tracers should be employed to link water column processes to sediment records, as well as to link present-day observations to paleo-evolution. Ecosystem models need to be developed based on empirical relationships derived from bioassay experiments and field investigations in order to predict the dynamics of carbon cycling along the stability continuum of POC and RDOC under potential global change scenarios. We propose that inorganic nutrient input to coastal waters may reduce the capacity for carbon sequestration as RDOC. The nutrient regime enabling maximum carbon storage from combined POC flux and RDOC formation should therefore be sought.

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