Mixotrophy, or the ability to acquire carbon from both auto- and heterotrophy, is a widespread ecological trait in marine protists. Using a metabarcoding dataset of marine plankton from the global ocean, 318,054 mixotrophic metabarcodes represented by 89,951,866 sequences and belonging to 133 taxonomic lineages were identified and classified into four mixotrophic functional types: constitutive mixotrophs (CM), generalist non-constitutive mixotrophs (GNCM), endo-symbiotic specialist non-constitutive mixotrophs (eSNCM), and plastidic specialist non-constitutive mixotrophs (pSNCM). Mixotrophy appeared ubiquitous, and the distributions of the four mixotypes were analyzed to identify the abiotic factors shaping their biogeographies. Kleptoplastidic mixotrophs (GNCM and pSNCM) were detected in new zones compared to previous morphological studies. Constitutive and non-constitutive mixotrophs had similar ranges of distributions. Most lineages were evenly found in the samples, yet some of them displayed strongly contrasted distributions, both across and within mixotypes. Particularly divergent biogeographies were found within endo-symbiotic mixotrophs, depending on the ability to form colonies or the mode of symbiosis. We showed how metabarcoding can be used in a complementary way with previous morphological observations to study the biogeography of mixotrophic protists and to identify key drivers of their biogeography.

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We would like to particularly thank Stéphane Pesant and Stéphane Audic for their work on making Tara Oceans datasets available. We also thank John Dolan (CNRS, LOV, Villefranche-sur-mer, France), Miguel Mendez-Sandin (Sorbonne Université, Station Biologique de Roscoff, France), and Wei-Ting Chen (National Taiwan Ocean University, Taiwan) for their essential help during the construction of the mixotrophic lineages set. We also thank Florentin Constancias for his help on the metabarcodes clustering tests conducted. Finally, we thank the three anonymous reviewers for their very constructive comments. This article is contribution number #84 of Tara Oceans. For the Tara Oceans expedition, we thank the commitment of the CNRS (in particular, Groupement de Recherche GDR3280), European Molecular Biology Laboratory (EMBL), Genoscope/CEA, VIB, Stazione Zoologica Anton Dohrn, UNIMIB, Fund for Scientific Research—Flanders, Rega Institute, KU Leuven, The French Ministry of Research. We also thank the support and commitment of Agnès b. and Etienne Bourgois, the Veolia Environment Foundation, Région Bretagne, Lorient Agglomération, World Courier, Illumina, the EDF Foundation, FRB, the Prince Albert II de Monaco Foundation, the Tara schooner and its captains and crew. We are also grateful to the French Ministry of Foreign Affairs for supporting the expedition and to the countries who graciously granted sampling permissions. Tara Oceans would not exist without continuous support from 23 institutes (http://oceans.taraexpeditions.org).


This work was funded by the FunOmics project of the French national program EC2CO-LEFE of CNRS and by the ModelOmics project of the Émergence program of Sorbonne Université, and partly supported byt the project MEGALADOM, part of the MASTODON program from the MITI, CNRS France. Emile Faure acknowledges a 3-year Ph.D. grant from the “Interface Pour le Vivant” (IPV) doctoral program of Sorbonne Université. SD Ayata ackowledges the CNRS for her sabbatical year as visiting researcher at ISYEB.

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  1. These authors contributed equally: Lucie Bittner, Sakina-Dorothée Ayata


  1. Sorbonne Université, CNRS, Laboratoire d’océanographie de Villefranche, LOV, 06230, Villefranche-sur-Mer, France

    • Emile Faure
    •  & Sakina-Dorothée Ayata
  2. Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum national d’Histoire naturelle, CNRS, Sorbonne Université, EPHE, CP 50, 57 rue Cuvier, 75005, Paris, France

    • Emile Faure
    • , Anne-Sophie Benoiston
    • , Lucie Bittner
    •  & Sakina-Dorothée Ayata
  3. Sorbonne Université, CNRS, UMR7144 Adaptation and Diversity in Marine Environment (AD2M) Laboratory, Ecology of Marine Plankton team, Station Biologique de Roscoff, Place Georges Teissier, 29680, Roscoff, France

    • Fabrice Not
  4. Genoscope, Institut de biologie François-Jacob, Commissariat à l’Energie Atomique (CEA), Evry, France, 91057, Evry, France

    • Karine Labadie


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