Mechanisms of microbial carbon sequestration in the ocean – future research directions
- 1. State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China
- 2. School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
- 3. Scripps Institution of Oceanography, UCSD, La Jolla, CA 920193, USA
- 4. Dalhousie University, Halifax, Nova Scotia, Canada
- 5. Department of Marine Science, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
- 6. CSIRO Marine and Atmospheric Research, Floreat, WA 6014, Australia
- 7. School of Marine Science and Policy, University of Delaware, DE 19958, USA
- 8. Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany
- 9. Sorbonne Universités, UPMC Univ. Paris 06, UMR7093, Laboratoire d'Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
- 10. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
- 11. Centre for Sustainable Aquatic Research, Swansea University, Swansea, UK
- 12. Dept. of Applied Physics and Applied Math., Columbia University and NASA-Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
- 13. South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
- 14. Tongji University, Shanghai, China
Description
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.