Articles | Volume 23, issue 13
https://doi.org/10.5194/bg-23-4793-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-23-4793-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
10 Jul 2026
Research article |
| 10 Jul 2026
| 10 Jul 2026
New insights into the primary production and the structure of the phytoplankton community in the South Indian Ocean using size fractionation experiments
Valentin Deteix
CORRESPONDING AUTHOR
LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, UMR 7159 (Sorbonne Université-CNRS-MNHN-IRD), 4 Place Jussieu, 75005 Paris, France
Céline Ridame
CORRESPONDING AUTHOR
LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, UMR 7159 (Sorbonne Université-CNRS-MNHN-IRD), 4 Place Jussieu, 75005 Paris, France
Céline Dimier
IMEV, Institut de la Mer de Villefranche, FR 3761 (Sorbonne Université, CNRS), 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France
Claire Lo Monaco
LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, UMR 7159 (Sorbonne Université-CNRS-MNHN-IRD), 4 Place Jussieu, 75005 Paris, France
Aline Tribollet
LOCEAN-IPSL, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, UMR 7159 (Sorbonne Université-CNRS-MNHN-IRD), 4 Place Jussieu, 75005 Paris, France
Frédéric Planchon
LEMAR, Laboratoire des Sciences de l'Environnement Marin, UMR 6539 (Univ. Brest-CNRS-IRD-Ifremer), Institut Universitaire Européen de la Mer, 29280 Plouzané, France
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Flavien Petit, Julia Uitz, Louison Dufour, Collin Roesler, Frédéric Partensky, Laurence Garczarek, Priscillia Gourvil, Céline Dimier, Melek Golbol, Vincenzo Vellucci, David Antoine, Christophe Penkerc'h, Vincent Taillandier, and Hervé Claustre
Biogeosciences, 23, 4561–4582, https://doi.org/10.5194/bg-23-4561-2026, https://doi.org/10.5194/bg-23-4561-2026, 2026
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We studied whether ocean sensors can detect changes in microscopic algae communities that influence marine ecosystems and carbon uptake. We combined laboratory experiments and ocean observations to test sensors that measure how algae emit light at different colors when illuminated. We found that combining these light measurements with other optical signals improves the identification of broad community types. This approach could help future ocean floats better track ecosystem change globally.
Pierre Friedlingstein, Michael O'Sullivan, Matthew W. Jones, Robbie M. Andrew, Dorothee C. E. Bakker, Judith Hauck, Peter Landschützer, Corinne Le Quéré, Hongmei Li, Ingrid T. Luijkx, Glen P. Peters, Wouter Peters, Julia Pongratz, Clemens Schwingshackl, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Kjetil Aas, Simone R. Alin, Peter Anthoni, Leticia Barbero, Nicholas R. Bates, Nicolas Bellouin, Alice Benoit-Cattin, Carla F. Berghoff, Raffaele Bernardello, Laurent Bopp, Ida Bagus Mandhara Brasika, Matthew A. Chamberlain, Naveen Chandra, Frédéric Chevallier, Louise P. Chini, Nathan O. Collier, Thomas H. Colligan, Margot Cronin, Laique M. Djeutchouang, Xinyu Dou, Matt P. Enright, Kazutaka Enyo, Michael Erb, Wiley Evans, Richard A. Feely, Liang Feng, Daniel J. Ford, Adrianna Foster, Filippa Fransner, Thomas Gasser, Marion Gehlen, Thanos Gkritzalis, Jefferson Goncalves De Souza, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Bertrand Guenet, Özgür Gürses, Kirsty Harrington, Ian Harris, Jens Heinke, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Akihiko Ito, Andrew R. Jacobson, Atul K. Jain, Tereza Jarníková, Annika Jersild, Fei Jiang, Steve D. Jones, Etsushi Kato, Ralph F. Keeling, Kees Klein Goldewijk, Jürgen Knauer, Yawen Kong, Jan Ivar Korsbakken, Charles Koven, Taro Kunimitsu, Xin Lan, Junjie Liu, Zhiqiang Liu, Zhu Liu, Claire Lo Monaco, Lei Ma, Gregg Marland, Patrick C. McGuire, Galen A. McKinley, Joe R. Melton, Natalie Monacci, Erwan Monier, Eric J. Morgan, David R. Munro, Jens D. Müller, Shin-Ichiro Nakaoka, Lorna R. Nayagam, Yosuke Niwa, Tobias Nutzel, Are Olsen, Abdirahman M. Omar, Naiqing Pan, Sudhanshu Pandey, Denis Pierrot, Zhangcai Qin, Pierre Regnier, Gregor Rehder, Laure Resplandy, Alizée Roobaert, Thais M. Rosan, Christian Rödenbeck, Jörg Schwinger, Ingunn Skjelvan, T. Luke Smallman, Victoria Spada, Mohanan G. Sreeush, Qing Sun, Adrienne J. Sutton, Colm Sweeney, Didier Swingedouw, Roland Séférian, Shintaro Takao, Hiroaki Tatebe, Hanqin Tian, Xiangjun Tian, Bronte Tilbrook, Hiroyuki Tsujino, Francesco Tubiello, Erik van Ooijen, Guido R. van der Werf, Sebastiaan J. van de Velde, Anthony P. Walker, Rik Wanninkhof, Xiaojuan Yang, Wenping Yuan, Xu Yue, and Jiye Zeng
Earth Syst. Sci. Data, 18, 3211–3288, https://doi.org/10.5194/essd-18-3211-2026, https://doi.org/10.5194/essd-18-3211-2026, 2026
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The Global Carbon Budget 2025 describes the methodology, main results, and datasets used to quantify the anthropogenic emissions of carbon dioxide (CO2) and their partitioning among the atmosphere, land ecosystems, and the ocean over the historical period (1750–2025). These living datasets are updated every year to provide the highest transparency and traceability in the reporting of CO2, the key driver of climate change.
Nicolas Metzl, Bronte Tilbrook, John Akl, Craig Neill, Alexandra Aymard, Claire Lo Monaco, Gilles Reverdin, Jean-Baptiste Sallée, Aude Barton, Frédéric Chevallier, and Marion Gehlen
EGUsphere, https://doi.org/10.5194/egusphere-2026-1664, https://doi.org/10.5194/egusphere-2026-1664, 2026
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Ocean acidification is explored in the Adélie Land coastal region in East Antarctica. The region is a permanent CO2 sink leading to a positive increase of total CO2 concentrations and to a progressive decrease of pH and aragonite Ωar. The lowest surface Ωar of 1.2 was observed in winter 2024, a critical limit for some marine species such as pteropod. A projection in the future suggests that aragonite saturation state will occur as soon as 2055 in the Adélie Land region.
Li-Qing Jiang, Amanda Fay, Jens Daniel Müller, Luke Gregor, Alizée Roobaert, Lydia Keppler, Dustin Carroll, Siv K. Lauvset, Tim DeVries, Judith Hauck, Christian Rödenbeck, Nicolas Metzl, Andrea J. Fassbender, Jean-Pierre Gattuso, Peter Landschützer, Rik Wanninkhof, Christopher Sabine, Simone R. Alin, Mario Hoppema, Are Olsen, Matthew P. Humphreys, Kunal Chakraborty, Ana C. Franco, Kumiko Azetsu-Scott, Dorothee C. E. Bakker, Leticia Barbero, Nicholas R. Bates, Nicole Besemer, Henry C. Bittig, Albert E. Boyd, Daniel Broullón, Wei-Jun Cai, Brendan R. Carter, Thi-Tuyet-Trang Chau, Chen-Tung Arthur Chen, Frédéric Cyr, John E. Dore, Ian Enochs, Richard A. Feely, Hernan E. Garcia, Marion Gehlen, Prasanna Kanti Ghoshal, Lucas Gloege, Melchor González-Dávila, Nicolas Gruber, Debby Ianson, Yosuke Iida, Masao Ishii, Apurva Padamnabh Joshi, Esther Kennedy, Alex Kozyr, Nico Lange, Claire Lo Monaco, Derek P. Manzello, Galen A. McKinley, Natalie M. Monacci, Xose A. Padin, Ana M. Palacio-Castro, Fiz F. Pérez, J. Magdalena Santana-Casiano, Jonathan Sharp, Adrienne Sutton, Jim Swift, Toste Tanhua, Maciej Telszewski, Jens Terhaar, Ruben van Hooidonk, Anton Velo, Andrew J. Watson, Angelicque E. White, Zelun Wu, Liang Xue, Hyelim Yoo, Jiye Zeng, and Guorong Zhong
Earth Syst. Sci. Data, 18, 1405–1462, https://doi.org/10.5194/essd-18-1405-2026, https://doi.org/10.5194/essd-18-1405-2026, 2026
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This review article provides an overview of 68 existing ocean carbonate chemistry data products and data product sets, encompassing a broad range of types, including compilations of cruise datasets, gap-filled observational products, model simulations, and more. It is designed to help researchers identify and access the data products that best support their scientific objectives, thereby facilitating progress in understanding the ocean's changing carbonate chemistry.
Nicolas Metzl, Claire Lo Monaco, Aline Tribollet, Jean-François Ternon, Frédéric Chevallier, and Marion Gehlen
Biogeosciences, 22, 7187–7204, https://doi.org/10.5194/bg-22-7187-2025, https://doi.org/10.5194/bg-22-7187-2025, 2025
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In the Mozambique Channel, observed acceleration of the ocean acidification in the recent decades is mainly driven by anthropogenic CO2 uptake. In this region the aragonite saturation state reached 3.2 in 2025 and could be as low as 3 in the next 10 years with potential impact on marine ecosystem including corals reefs areas.
Yannick Bras, Evelyn Freney, Mar Benavides, Estelle Bigeard, Gabriel Dulaquais, Céline Dimier, Laetitia Bouvier, Mickaël Ribeiro, Cécile Guieu, Sophie Bonnet, and Karine Sellegri
EGUsphere, https://doi.org/10.5194/egusphere-2025-3580, https://doi.org/10.5194/egusphere-2025-3580, 2025
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In marine regions, sea spray aerosols may act as ice nucleating particles to promote the formation of ice crystals in the atmosphere. Here, we study the ice nucleating properties of the seawater and of generated sea spray measured during a ship campaign in contrasted waters, including hydrothermal-influenced waters. We report that the majority of particles were of biological origin, and that their variability closely followed the local biological activity.
Nicolas Metzl, Jonathan Fin, Claire Lo Monaco, Claude Mignon, Samir Alliouane, Bruno Bombled, Jacqueline Boutin, Yann Bozec, Steeve Comeau, Pascal Conan, Laurent Coppola, Pascale Cuet, Eva Ferreira, Jean-Pierre Gattuso, Frédéric Gazeau, Catherine Goyet, Emilie Grossteffan, Bruno Lansard, Dominique Lefèvre, Nathalie Lefèvre, Coraline Leseurre, Sébastien Petton, Mireille Pujo-Pay, Christophe Rabouille, Gilles Reverdin, Céline Ridame, Peggy Rimmelin-Maury, Jean-François Ternon, Franck Touratier, Aline Tribollet, Thibaut Wagener, and Cathy Wimart-Rousseau
Earth Syst. Sci. Data, 17, 1075–1100, https://doi.org/10.5194/essd-17-1075-2025, https://doi.org/10.5194/essd-17-1075-2025, 2025
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This work presents a new synthesis of 67 000 total alkalinity and total dissolved inorganic carbon observations obtained between 1993 and 2023 in the global ocean, coastal zones, and the Mediterranean Sea. We describe the data assemblage and associated quality control and discuss some potential uses of this dataset. The dataset is provided in a single format and includes the quality flag for each sample.
Nicolas Metzl, Claire Lo Monaco, Coraline Leseurre, Céline Ridame, Gilles Reverdin, Thi Tuyet Trang Chau, Frédéric Chevallier, and Marion Gehlen
Ocean Sci., 20, 725–758, https://doi.org/10.5194/os-20-725-2024, https://doi.org/10.5194/os-20-725-2024, 2024
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In the southern Indian Ocean, south of the polar front, an observed increase of sea surface fCO2 and a decrease of pH over 1985–2021 are mainly driven by anthropogenic CO2 uptake, but in the last decade (2010–2020) fCO2 and pH were stable in summer, highlighting the competitive balance between anthropogenic CO2 and primary production. In the water column the increase of anthropogenic CO2 concentrations leads to migration of the aragonite saturation state from 600 m in 1985 up to 400 m in 2021.
Nicolas Metzl, Jonathan Fin, Claire Lo Monaco, Claude Mignon, Samir Alliouane, David Antoine, Guillaume Bourdin, Jacqueline Boutin, Yann Bozec, Pascal Conan, Laurent Coppola, Frédéric Diaz, Eric Douville, Xavier Durrieu de Madron, Jean-Pierre Gattuso, Frédéric Gazeau, Melek Golbol, Bruno Lansard, Dominique Lefèvre, Nathalie Lefèvre, Fabien Lombard, Férial Louanchi, Liliane Merlivat, Léa Olivier, Anne Petrenko, Sébastien Petton, Mireille Pujo-Pay, Christophe Rabouille, Gilles Reverdin, Céline Ridame, Aline Tribollet, Vincenzo Vellucci, Thibaut Wagener, and Cathy Wimart-Rousseau
Earth Syst. Sci. Data, 16, 89–120, https://doi.org/10.5194/essd-16-89-2024, https://doi.org/10.5194/essd-16-89-2024, 2024
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This work presents a synthesis of 44 000 total alkalinity and dissolved inorganic carbon observations obtained between 1993 and 2022 in the Global Ocean and the Mediterranean Sea at the surface and in the water column. Seawater samples were measured using the same method and calibrated with international Certified Reference Material. We describe the data assemblage, quality control and some potential uses of this dataset.
Gilles Reverdin, Claire Waelbroeck, Catherine Pierre, Camille Akhoudas, Giovanni Aloisi, Marion Benetti, Bernard Bourlès, Magnus Danielsen, Jérôme Demange, Denis Diverrès, Jean-Claude Gascard, Marie-Noëlle Houssais, Hervé Le Goff, Pascale Lherminier, Claire Lo Monaco, Herlé Mercier, Nicolas Metzl, Simon Morisset, Aïcha Naamar, Thierry Reynaud, Jean-Baptiste Sallée, Virginie Thierry, Susan E. Hartman, Edward W. Mawji, Solveig Olafsdottir, Torsten Kanzow, Anton Velo, Antje Voelker, Igor Yashayaev, F. Alexander Haumann, Melanie J. Leng, Carol Arrowsmith, and Michael Meredith
Earth Syst. Sci. Data, 14, 2721–2735, https://doi.org/10.5194/essd-14-2721-2022, https://doi.org/10.5194/essd-14-2721-2022, 2022
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The CISE-LOCEAN seawater stable isotope dataset has close to 8000 data entries. The δ18O and δD isotopic data measured at LOCEAN have uncertainties of at most 0.05 ‰ and 0.25 ‰, respectively. Some data were adjusted to correct for evaporation. The internal consistency indicates that the data can be used to investigate time and space variability to within 0.03 ‰ and 0.15 ‰ in δ18O–δD17; comparisons with data analyzed in other institutions suggest larger differences with other datasets.
Coraline Leseurre, Claire Lo Monaco, Gilles Reverdin, Nicolas Metzl, Jonathan Fin, Claude Mignon, and Léa Benito
Biogeosciences, 19, 2599–2625, https://doi.org/10.5194/bg-19-2599-2022, https://doi.org/10.5194/bg-19-2599-2022, 2022
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Decadal trends of fugacity of CO2 (fCO2), total alkalinity (AT), total carbon (CT) and pH in surface waters are investigated in different domains of the southern Indian Ocean (45°S–57°S) from ongoing and station observations regularly conducted in summer over the period 1998–2019. The fCO2 increase and pH decrease are mainly driven by anthropogenic CO2 estimated just below the summer mixed layer, as well as by a warming south of the polar front or in the fertilized waters near Kerguelen Island.
Nicolas Metzl, Claire Lo Monaco, Coraline Leseurre, Céline Ridame, Jonathan Fin, Claude Mignon, Marion Gehlen, and Thi Tuyet Trang Chau
Biogeosciences, 19, 1451–1468, https://doi.org/10.5194/bg-19-1451-2022, https://doi.org/10.5194/bg-19-1451-2022, 2022
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During an oceanographic cruise conducted in January 2020 in the south-western Indian Ocean, we observed very low CO2 concentrations associated with a strong phytoplankton bloom that occurred south-east of Madagascar. This biological event led to a strong regional CO2 ocean sink not previously observed.
Julie Dinasquet, Estelle Bigeard, Frédéric Gazeau, Farooq Azam, Cécile Guieu, Emilio Marañón, Céline Ridame, France Van Wambeke, Ingrid Obernosterer, and Anne-Claire Baudoux
Biogeosciences, 19, 1303–1319, https://doi.org/10.5194/bg-19-1303-2022, https://doi.org/10.5194/bg-19-1303-2022, 2022
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Saharan dust deposition of nutrients and trace metals is crucial to microbes in the Mediterranean Sea. Here, we tested the response of microbial and viral communities to simulated dust deposition under present and future conditions of temperature and pH. Overall, the effect of the deposition was dependent on the initial microbial assemblage, and future conditions will intensify microbial responses. We observed effects on trophic interactions, cascading all the way down to viral processes.
Céline Ridame, Julie Dinasquet, Søren Hallstrøm, Estelle Bigeard, Lasse Riemann, France Van Wambeke, Matthieu Bressac, Elvira Pulido-Villena, Vincent Taillandier, Fréderic Gazeau, Antonio Tovar-Sanchez, Anne-Claire Baudoux, and Cécile Guieu
Biogeosciences, 19, 415–435, https://doi.org/10.5194/bg-19-415-2022, https://doi.org/10.5194/bg-19-415-2022, 2022
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We show that in the Mediterranean Sea spatial variability in N2 fixation is related to the diazotrophic community composition reflecting different nutrient requirements among species. Nutrient supply by Saharan dust is of great importance to diazotrophs, as shown by the strong stimulation of N2 fixation after a simulated dust event under present and future climate conditions; the magnitude of stimulation depends on the degree of limitation related to the diazotrophic community composition.
Matthieu Bressac, Thibaut Wagener, Nathalie Leblond, Antonio Tovar-Sánchez, Céline Ridame, Vincent Taillandier, Samuel Albani, Sophie Guasco, Aurélie Dufour, Stéphanie H. M. Jacquet, François Dulac, Karine Desboeufs, and Cécile Guieu
Biogeosciences, 18, 6435–6453, https://doi.org/10.5194/bg-18-6435-2021, https://doi.org/10.5194/bg-18-6435-2021, 2021
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Phytoplankton growth is limited by the availability of iron in about 50 % of the ocean. Atmospheric deposition of desert dust represents a key source of iron. Here, we present direct observations of dust deposition in the Mediterranean Sea. A key finding is that the input of iron from dust primarily occurred in the deep ocean, while previous studies mainly focused on the ocean surface. This new insight will enable us to better represent controls on global marine productivity in models.
France Van Wambeke, Vincent Taillandier, Karine Desboeufs, Elvira Pulido-Villena, Julie Dinasquet, Anja Engel, Emilio Marañón, Céline Ridame, and Cécile Guieu
Biogeosciences, 18, 5699–5717, https://doi.org/10.5194/bg-18-5699-2021, https://doi.org/10.5194/bg-18-5699-2021, 2021
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Simultaneous in situ measurements of (dry and wet) atmospheric deposition and biogeochemical stocks and fluxes in the sunlit waters of the open Mediterranean Sea revealed complex physical and biological processes occurring within the mixed layer. Nitrogen (N) budgets were computed to compare the sources and sinks of N in the mixed layer. The transitory effect observed after a wet dust deposition impacted the microbial food web down to the deep chlorophyll maximum.
Frédéric Gazeau, Céline Ridame, France Van Wambeke, Samir Alliouane, Christian Stolpe, Jean-Olivier Irisson, Sophie Marro, Jean-Michel Grisoni, Guillaume De Liège, Sandra Nunige, Kahina Djaoudi, Elvira Pulido-Villena, Julie Dinasquet, Ingrid Obernosterer, Philippe Catala, and Cécile Guieu
Biogeosciences, 18, 5011–5034, https://doi.org/10.5194/bg-18-5011-2021, https://doi.org/10.5194/bg-18-5011-2021, 2021
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This paper shows that the impacts of Saharan dust deposition in different Mediterranean basins are as strong as those observed in coastal waters but differed substantially between the three tested stations, differences attributed to variable initial metabolic states. A stronger impact of warming and acidification on mineralization suggests a decreased capacity of Mediterranean surface communities to sequester CO2 following the deposition of atmospheric particles in the coming decades.
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Short summary
From in situ measurements, we characterized the size structure of both phytoplankton productivity and phytoplankton chemotaxonomic groups biomass in contrasting biogeochemical areas of the South Indian Ocean. We highlighted pronounced inter- and intra-zonal variability in these size structures. Across the study area, primary production and biomass was mainly driven by medium- and large-sized diatoms, haptophytes and dinoflagellates.
From in situ measurements, we characterized the size structure of both phytoplankton...
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