Interactions between planktonic organisms and biogeochemical cycles across trophic and N2 fixation gradients in the western tropical South Pacific Ocean: a multidisciplinary approach (OUTPACE experiment)
Interactions between planktonic organisms and biogeochemical cycles across trophic and N2 fixation gradients in the western tropical South Pacific Ocean: a multidisciplinary approach (OUTPACE experiment)
Editor(s): T. Moutin, S. Bonnet, K. Richards, D. G. Capone, E. Marañón, and L. Mémery
The goal of this special issue is to present the knowledge obtained concerning the functioning of the western tropical South Pacific (WTSP) ecosystems and associated biogeochemical cycles based on the datasets acquired during the OUTPACE experiment. The physical variability and the hydrodynamic context of biogeochemical sampling are described, as well as the impacts of mesoscale circulation and forcing on biogeographic gradients, along with the longitudinal contrast in small- scale turbulence along ~20° S. An optimum multi-parameter analysis of the water mass structure is also provided.

The focus on diazotrophs and dinitrogen fixation concerns the distribution and drivers of symbiotic and free-living diazotrophic cyanobacteria, the contribution of particulate and dissolved (N release) fractions to the hotspot of N2 fixation found during the cruise, zonal gradient in N2 fixation rates, the partition of N2 fixation rates between the particulate and dissolved fractions, the diazotroph-derived N transfer to the planktonic food web, the N2 fixation contribution to export production, and finally the N budget at the long-duration stations studied using a Lagrangian adaptative strategy. Aphotic N2 fixation, heterotrophic diazotrophs and their relationship with labile organic matter, as well as programmed cell death in diazotrophs, are also investigated.

The dynamics of phytoplankton, heterotrophic bacterioplankton, and zooplankton along the gradient of diazotroph diversity and activity are described together with the composition and distribution of dissolved organic carbon and the changes in inorganic carbon content along the longitudinal transect. Net community production, the assimilation of organic carbon and nutrient substrates by unicellular cyanobacteria, and microbial response to the N and P compounds excreted by copepods are quantified. A specific focus on siliceous plankton and Si biogeochemical cycling is also presented.

Optical properties of the WTSP waters are presented, with a focus on the cyanobacterial (diazotroph) impact on bio-optical properties, UV–visible light attenuation and Chl a algorithms for WTSP oligotrophic waters.

Finally, the main processes controlling the biological carbon pump in the WTSP are investigated using a 1DV biogeochemical–physical coupled model, and the new knowledge gained on the interactions between planktonic organisms and the cycle of biogenic elements is used to propose a new scheme for this functioning and role, at the present time and in the near future, in the oligotrophic Pacific Ocean.

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24 Apr 2019
Introduction: OUTPACE – Oligotrophy to Ultraoligotrophy PACific Experiment
Thierry Moutin
Biogeosciences, 16, 1673–1673, https://doi.org/10.5194/bg-16-1673-2019,https://doi.org/10.5194/bg-16-1673-2019, 2019
06 Jul 2017
Preface: The Oligotrophy to the UlTra-oligotrophy PACific Experiment (OUTPACE cruise, 18 February to 3 April 2015)
Thierry Moutin, Andrea Michelangelo Doglioli, Alain de Verneil, and Sophie Bonnet
Biogeosciences, 14, 3207–3220, https://doi.org/10.5194/bg-14-3207-2017,https://doi.org/10.5194/bg-14-3207-2017, 2017
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10 Apr 2018
OUTPACE long duration stations: physical variability, context of biogeochemical sampling, and evaluation of sampling strategy
Alain de Verneil, Louise Rousselet, Andrea M. Doglioli, Anne A. Petrenko, Christophe Maes, Pascale Bouruet-Aubertot, and Thierry Moutin
Biogeosciences, 15, 2125–2147, https://doi.org/10.5194/bg-15-2125-2018,https://doi.org/10.5194/bg-15-2125-2018, 2018
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15 Mar 2018
Distribution and drivers of symbiotic and free-living diazotrophic cyanobacteria in the western tropical South Pacific
Marcus Stenegren, Andrea Caputo, Carlo Berg, Sophie Bonnet, and Rachel A. Foster
Biogeosciences, 15, 1559–1578, https://doi.org/10.5194/bg-15-1559-2018,https://doi.org/10.5194/bg-15-1559-2018, 2018
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24 Jul 2017
The fate of a southwest Pacific bloom: gauging the impact of submesoscale vs. mesoscale circulation on biological gradients in the subtropics
Alain de Verneil, Louise Rousselet, Andrea M. Doglioli, Anne A. Petrenko, and Thierry Moutin
Biogeosciences, 14, 3471–3486, https://doi.org/10.5194/bg-14-3471-2017,https://doi.org/10.5194/bg-14-3471-2017, 2017
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20 Apr 2018
Large- to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (southwest Pacific)
Louise Rousselet, Alain de Verneil, Andrea M. Doglioli, Anne A. Petrenko, Solange Duhamel, Christophe Maes, and Bruno Blanke
Biogeosciences, 15, 2411–2431, https://doi.org/10.5194/bg-15-2411-2018,https://doi.org/10.5194/bg-15-2411-2018, 2018
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02 May 2018
N2 fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise)
Mathieu Caffin, Thierry Moutin, Rachel Ann Foster, Pascale Bouruet-Aubertot, Andrea Michelangelo Doglioli, Hugo Berthelot, Cécile Guieu, Olivier Grosso, Sandra Helias-Nunige, Nathalie Leblond, Audrey Gimenez, Anne Alexandra Petrenko, Alain de Verneil, and Sophie Bonnet
Biogeosciences, 15, 2565–2585, https://doi.org/10.5194/bg-15-2565-2018,https://doi.org/10.5194/bg-15-2565-2018, 2018
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04 May 2018
Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets
Angela N. Knapp, Kelly M. McCabe, Olivier Grosso, Nathalie Leblond, Thierry Moutin, and Sophie Bonnet
Biogeosciences, 15, 2619–2628, https://doi.org/10.5194/bg-15-2619-2018,https://doi.org/10.5194/bg-15-2619-2018, 2018
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04 May 2018
Dynamics and controls of heterotrophic prokaryotic production in the western tropical South Pacific Ocean: links with diazotrophic and photosynthetic activity
France Van Wambeke, Audrey Gimenez, Solange Duhamel, Cécile Dupouy, Dominique Lefevre, Mireille Pujo-Pay, and Thierry Moutin
Biogeosciences, 15, 2669–2689, https://doi.org/10.5194/bg-15-2669-2018,https://doi.org/10.5194/bg-15-2669-2018, 2018
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16 May 2018
Nutrient availability and the ultimate control of the biological carbon pump in the western tropical South Pacific Ocean
Thierry Moutin, Thibaut Wagener, Mathieu Caffin, Alain Fumenia, Audrey Gimenez, Melika Baklouti, Pascale Bouruet-Aubertot, Mireille Pujo-Pay, Karine Leblanc, Dominique Lefevre, Sandra Helias Nunige, Nathalie Leblond, Olivier Grosso, and Alain de Verneil
Biogeosciences, 15, 2961–2989, https://doi.org/10.5194/bg-15-2961-2018,https://doi.org/10.5194/bg-15-2961-2018, 2018
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22 May 2018
Aphotic N2 fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean
Mar Benavides, Katyanne M. Shoemaker, Pia H. Moisander, Jutta Niggemann, Thorsten Dittmar, Solange Duhamel, Olivier Grosso, Mireille Pujo-Pay, Sandra Hélias-Nunige, Alain Fumenia, and Sophie Bonnet
Biogeosciences, 15, 3107–3119, https://doi.org/10.5194/bg-15-3107-2018,https://doi.org/10.5194/bg-15-3107-2018, 2018
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21 Jun 2018
Transfer of diazotroph-derived nitrogen to the planktonic food web across gradients of N2 fixation activity and diversity in the western tropical South Pacific Ocean
Mathieu Caffin, Hugo Berthelot, Véronique Cornet-Barthaux, Aude Barani, and Sophie Bonnet
Biogeosciences, 15, 3795–3810, https://doi.org/10.5194/bg-15-3795-2018,https://doi.org/10.5194/bg-15-3795-2018, 2018
28 Jun 2018
Programmed cell death in diazotrophs and the fate of organic matter in the western tropical South Pacific Ocean during the OUTPACE cruise
Dina Spungin, Natalia Belkin, Rachel A. Foster, Marcus Stenegren, Andrea Caputo, Mireille Pujo-Pay, Nathalie Leblond, Cécile Dupouy, Sophie Bonnet, and Ilana Berman-Frank
Biogeosciences, 15, 3893–3908, https://doi.org/10.5194/bg-15-3893-2018,https://doi.org/10.5194/bg-15-3893-2018, 2018
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29 Jun 2018
Microbial community structure in the western tropical South Pacific
Nicholas Bock, France Van Wambeke, Moïra Dion, and Solange Duhamel
Biogeosciences, 15, 3909–3925, https://doi.org/10.5194/bg-15-3909-2018,https://doi.org/10.5194/bg-15-3909-2018, 2018
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05 Jul 2018
Intermediate water flows in the western South Pacific: as revealed by individual Argo floats trajectories and a model re-analysis
Simon Barbot, Anne Petrenko, and Christophe Maes
Biogeosciences, 15, 4103–4124, https://doi.org/10.5194/bg-15-4103-2018,https://doi.org/10.5194/bg-15-4103-2018, 2018
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12 Jul 2018
In-depth characterization of diazotroph activity across the western tropical South Pacific hotspot of N2 fixation (OUTPACE cruise)
Sophie Bonnet, Mathieu Caffin, Hugo Berthelot, Olivier Grosso, Mar Benavides, Sandra Helias-Nunige, Cécile Guieu, Marcus Stenegren, and Rachel Ann Foster
Biogeosciences, 15, 4215–4232, https://doi.org/10.5194/bg-15-4215-2018,https://doi.org/10.5194/bg-15-4215-2018, 2018
18 Jul 2018
Modelling N2 fixation related to Trichodesmium sp.: driving processes and impacts on primary production in the tropical Pacific Ocean
Cyril Dutheil, Olivier Aumont, Thomas Gorguès, Anne Lorrain, Sophie Bonnet, Martine Rodier, Cécile Dupouy, Takuhei Shiozaki, and Christophe Menkes
Biogeosciences, 15, 4333–4352, https://doi.org/10.5194/bg-15-4333-2018,https://doi.org/10.5194/bg-15-4333-2018, 2018
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29 Aug 2018
Remote sensing of Trichodesmium spp. mats in the western tropical South Pacific
Guillaume Rousset, Florian De Boissieu, Christophe E. Menkes, Jérôme Lefèvre, Robert Frouin, Martine Rodier, Vincent Ridoux, Sophie Laran, Sophie Bonnet, and Cécile Dupouy
Biogeosciences, 15, 5203–5219, https://doi.org/10.5194/bg-15-5203-2018,https://doi.org/10.5194/bg-15-5203-2018, 2018
29 Aug 2018
Carbonate system distribution, anthropogenic carbon and acidification in the western tropical South Pacific (OUTPACE 2015 transect)
Thibaut Wagener, Nicolas Metzl, Mathieu Caffin, Jonathan Fin, Sandra Helias Nunige, Dominique Lefevre, Claire Lo Monaco, Gilles Rougier, and Thierry Moutin
Biogeosciences, 15, 5221–5236, https://doi.org/10.5194/bg-15-5221-2018,https://doi.org/10.5194/bg-15-5221-2018, 2018
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30 Aug 2018
Diazotrophic Trichodesmium impact on UV–Vis radiance and pigment composition in the western tropical South Pacific
Cécile Dupouy, Robert Frouin, Marc Tedetti, Morgane Maillard, Martine Rodier, Fabien Lombard, Lionel Guidi, Marc Picheral, Jacques Neveux, Solange Duhamel, Bruno Charrière, and Richard Sempéré
Biogeosciences, 15, 5249–5269, https://doi.org/10.5194/bg-15-5249-2018,https://doi.org/10.5194/bg-15-5249-2018, 2018
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20 Sep 2018
Silicon cycle in the tropical South Pacific: contribution to the global Si cycle and evidence for an active pico-sized siliceous plankton
Karine Leblanc, Véronique Cornet, Peggy Rimmelin-Maury, Olivier Grosso, Sandra Hélias-Nunige, Camille Brunet, Hervé Claustre, Joséphine Ras, Nathalie Leblond, and Bernard Quéguiner
Biogeosciences, 15, 5595–5620, https://doi.org/10.5194/bg-15-5595-2018,https://doi.org/10.5194/bg-15-5595-2018, 2018
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02 Oct 2018
Trichodesmium physiological ecology and phosphate reduction in the western tropical South Pacific
Kyle R. Frischkorn, Andreas Krupke, Cécile Guieu, Justine Louis, Mónica Rouco, Andrés E. Salazar Estrada, Benjamin A. S. Van Mooy, and Sonya T. Dyhrman
Biogeosciences, 15, 5761–5778, https://doi.org/10.5194/bg-15-5761-2018,https://doi.org/10.5194/bg-15-5761-2018, 2018
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15 Oct 2018
Nitrogen and phosphorus recycling mediated by copepods and response of bacterioplankton community from three contrasting areas in the western tropical South Pacific (20° S)
Valentina Valdés, François Carlotti, Ruben Escribano, Katty Donoso, Marc Pagano, Verónica Molina, and Camila Fernandez
Biogeosciences, 15, 6019–6032, https://doi.org/10.5194/bg-15-6019-2018,https://doi.org/10.5194/bg-15-6019-2018, 2018
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07 Nov 2018
Diazotrophy as the main driver of the oligotrophy gradient in the western tropical South Pacific Ocean: results from a one-dimensional biogeochemical–physical coupled model
Audrey Gimenez, Melika Baklouti, Thibaut Wagener, and Thierry Moutin
Biogeosciences, 15, 6573–6589, https://doi.org/10.5194/bg-15-6573-2018,https://doi.org/10.5194/bg-15-6573-2018, 2018
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10 Dec 2018
Meso-zooplankton structure and functioning in the western tropical South Pacific along the 20th parallel south during the OUTPACE survey (February–April 2015)
François Carlotti, Marc Pagano, Loïc Guilloux, Katty Donoso, Valentina Valdés, Olivier Grosso, and Brian P. V. Hunt
Biogeosciences, 15, 7273–7297, https://doi.org/10.5194/bg-15-7273-2018,https://doi.org/10.5194/bg-15-7273-2018, 2018
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15 Jan 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
Biogeosciences, 16, 105–116, https://doi.org/10.5194/bg-16-105-2019,https://doi.org/10.5194/bg-16-105-2019, 2019
21 Dec 2018
Longitudinal contrast in turbulence along a  ∼ 19° S section in the Pacific and its consequences for biogeochemical fluxes
Pascale Bouruet-Aubertot, Yannis Cuypers, Andrea Doglioli, Mathieu Caffin, Christophe Yohia, Alain de Verneil, Anne Petrenko, Dominique Lefèvre, Hervé Le Goff, Gilles Rougier, Marc Picheral, and Thierry Moutin
Biogeosciences, 15, 7485–7504, https://doi.org/10.5194/bg-15-7485-2018,https://doi.org/10.5194/bg-15-7485-2018, 2018
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