Tag Archive for: biologic carbon pump

Carbon fate in the deep ocean

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The biological carbon pump can be broken down into three stages: the formation of biogenic carbon at the surface (production), the transfer below the mixed layer (export) and the attenuation of the flux in the mesopelagic zone (200-2000 m), towards long-term storage (> 1000 years) in the deep ocean and sediments. For operational reasons, the years 1980-2000 were strongly focused on the first two components of the biological pump (international JGOFS programme). The depth of carbon flux attenuation with depth, which imposes strong constraints on the time scales of carbon storage in the deep ocean, is constrained by ocean dynamics (turbulence, small scales, etc.), dissolution processes, biological activity (heterotrophic activity, respiration) and particle behaviour (sedimentation, aggregation/desaggregation). The evolution of observation means (autonomous platforms, high frequency measurements, acoustics, imaging, molecular biology, etc.), as well as progress in modelling (computer power, taking complexity into account, Artificial Intelligence), now make it possible to tackle this question head-on. LEMAR is fully involved in this new dynamic and relies on its expertise in the description of the fate of dissolved organic matter, the silicon, iron and carbon cycles, the role of zooplankton, remineralisation processes, particle dynamics, the study of the small scale in the mesopelagic zone (see AR2. 1 CHIBIDO), modelling (in connection with the ITM Atlantic teams developing approaches in Artificial Intelligence), microbiology or ecology to get involved and carry out international projects on this topic. In addition, the laboratory actively participated in the creation of the international consortium JETZON (Joint Exploration of the Twilight Zone Ocean Network: https://jetzon.org/) coordinating programmes on the mesopelagic zone.

Influence of diatom diversity on the ocean biological carbon pump

Abstract

Diatoms sustain the marine food web and contribute to the export of carbon from the surface ocean to depth. They account for about 40% of marine primary productivity and particulate carbon exported to depth as part of the biological pump. Diatoms have long been known to be abundant in turbulent, nutrient-rich waters, but observations and simulations indicate that they are dominant also in meso- and submesoscale structures such as fronts and filaments, and in the deep chlorophyll maximum. Diatoms vary widely in size, morphology and elemental composition, all of which control the quality, quantity and sinking speed of biogenic matter to depth. In particular, their silica shells provide ballast to marine snow and faecal pellets, and can help transport carbon to both the mesopelagic layer and deep ocean. Herein we show that the extent to which diatoms contribute to the export of carbon varies by diatom type, with carbon transfer modulated by the Si/C ratio of diatom cells, the thickness of the shells and their life strategies; for instance, the tendency to form aggregates or resting spores. Model simulations project a decline in the contribution of diatoms to primary production everywhere outside of the Southern Ocean. We argue that we need to understand changes in diatom diversity, life cycle and plankton interactions in a warmer and more acidic ocean in much more detail to fully assess any changes in their contribution to the biological pump.

 

Graphical abstract

Reference

Tréguer, P., Bowler, C., Moriceau, B., Dutkiewicz, S., Gehlen, M., Aumont, O., Bittner,L., Dugdale, R., Finkel, Z., Ludicone, D., Jahn,O., Guidi, L., Lasbleiz, M., Leblanc, K., Levy, M. & Pondaven, P. (2017). Influence of diatom diversity on the ocean biological carbon pump. Nature Geoscience 11, 27–37 (2017). doi:10.1038/s41561-017-0028-x

Tag Archive for: biologic carbon pump

Frédéric LE MOIGNE

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Tag Archive for: biologic carbon pump

APERO

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Frigo

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