Benavides M. auteur aut IRD Berthelot H. auteur aut IRD Duhamel S. auteur aut IRD Raimbault P. auteur aut IRD Bonnet Sophie auteur aut IRD text journalArticle eng text/pdf reformatted digital access The globally distributed diazotroph Trichodesmium contributes importantly to nitrogen inputs in the oligotrophic oceans. Sites of dissolved organic matter (DOM) accumulation could promote the mixotrophic nutrition of Trichodesmium when inorganic nutrients are scarce. Nano-scale secondary ion mass spectrometry (nanoSIMS) analyses of individual trichomes sampled in the South Pacific Ocean, showed significant C-13-enrichments after incubation with either C-13-labeled carbohydrates or amino acids. These results suggest that DOM could be directly taken up by Trichodesmium or primarily consumed by heterotrophic epibiont bacteria that ultimately transfer reduced DOM compounds to their host trichomes. Although the addition of carbohydrates or amino acids did not significantly affect bulk N-2 fixation rates, N-2 fixation was enhanced by amino acids in individual colonies of Trichodesmium. We discuss the ecological advantages of DOM use by Trichodesmium as an alternative to autotrophic nutrition in oligotrophic open ocean waters. specialized PACIFIQUE SUD OUEST 036 032 7 art. 41315 [6 p.] 2017 2045-2322 https://www.documentation.ird.fr/hor/fdi:010068922 10.1038/srep41315 2045-2322 [F B010068922] https://www.documentation.ird.fr/hor/fdi:010068922 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-02/010068922.pdf IRD - Base Horizon / Pleins textes 2017-03-02 2023-07-11 fdi:010068922 fre