Interactions between planktonic organisms and biogeochemical cycles across trophic and N2 fixation gradients in the western tropical South Pacific Ocean: a multidisciplinary approach


Principal investigators

Thierry Moutin et Sophie Bonnet

The overall goal of OUTPACE (Oligotrophy to UlTra-oligotrophy PACific Experiment) was to obtain a successful representation of the interactions between planktonic organisms and the cycle of biogenic elements in the western tropical South Pacific Ocean across trophic and N2 fixation gradients. Within the context of climate change, it is necessary to better quantify the ability of the oligotrophic ocean to sequester carbon through biological processes. OUTPACE was organized around three main objectives, which were :


To perform a zonal characterization of the biogeochemistry and biological diversity of the western tropical South Pacific during austral summer conditions,


To study the production and fate of organic matter (including carbon export) in three contrasting trophic regimes (increasing oligotrophy) with a particular emphasis on the role of dinitrogen fixation,


To obtain a representation of the main biogeochemical fluxes and dynamics of the planktonic trophic network.

The international Outpace cruise took place between 18 February and 3 April 2015 aboard the RV L'Atalante and involved 60 scientists (30 onboard).

The major experimental and modelling results obtained during the project are described in the Outpace special issue and other publications from the project.

OUTPACE Publications

Accepted publications

FEMS Microbiology Letters, Volume 369, 2022
Anomalously high abundance of Crocosphaera in the South Pacific Gyre

Benavides, M. Caffin, M., Duhamel, S., Foster, R., Grosso, O., Guieu, C., Van Wambeke, F., Bonnet, S.

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Biogeosciences, 16, 105–116, 2019
The composition and distribution of semi-labile dissolved organic matter across the southwest Pacific

Christos Panagiotopoulos, Mireille Pujo-Pay, Mar Benavides, France Van Wambeke, and Richard Sempéré

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Biogeosciences, 15, 2565–2585, 2018
N₂ fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise)

Caffin, M., Moutin, T., Foster, R. A., Bouruet-Aubertot, P., Doglioli, A. M., Berthelot, H., Guieu, C., Grosso, O., Helias-Nunige, S., Leblond, N., Gimenez, A., Petrenko, A. A., de Verneil, A., and Bonnet, S.

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Biogeosciences, 15, 1559-1578, 2018
Distribution and drivers of symbiotic and free-living diazotrophic cyanobacteria in the western tropical South Pacific

Stenegren, M., Caputo, A., Berg, C., Bonnet, S., and Foster, R. A.

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Biogeosciences, Volume 15, 3107–3119, 2018
Aphotic N₂ fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean

Benavides, M., Shoemaker, K. M., Moisander, P. H., Niggemann, J., Dittmar, T., Duhamel, S., Grosso, O., Pujo-Pay, M., Hélias-Nunige, S., Fumenia, A., and Bonnet, S.

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Funding and partners

OUTPACE was funded by ANR, INSU LEFE-CYBER, LEFE-GMMC, CNES, the TGIR ‘Flotte Océanographique Française’ and IRD. OUTPACE has been endorsed as an IMBER project.​The OUTPACE consortium involves 65 scientists from 14 international institutions among which physical oceanographers, biogeochemist, molecular ecologists, trace metals chemists and modelers.

  • M.I.O Mediterranean Institute of Oceanography (Marseille, France)
  • LOV Laboratoire d’Océanographie de Villefranche, (Villefranche/mer, France)
  • LEMAR Laboratoire des Sciences de l’Environnement Marin (Brest, France)
  • EIO Ecosystèmes Insulaires Océaniens (Papeete, French Polynesia)
  • IRD Nouméa (New Caledonia)
  • LOPS Laboratoire d’Océanographie Physique et Spatiale (Brest, France)
  • LOCEAN Laboratoire d’Océanographie et du Climat (Paris, France)
  • LEGOS Laboratoire d’Etudes en Géophysique et Océano. spatiales (Toulouse, France)
  • Woods Hole Oceanographic Institution (USA)
  • University of South Pacific (Fij)
  • University of Stockholm (Sweden)
  • Bar Ilan University (Israel)
  • Florida State University (USA)
  • Columbia University (USA)