title: Dissolved organic matter uptake by Trichodesmium in the Southwest Pacific.
abstract: 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 significant13C-enrichments after incubation with either13C-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 N2fixation rates, N2fixation 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.
authors.affiliation: Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 98848, Noumea, New Caledonia.|Marine Biological Section, Department of Biology, University of Copenhagen, 3000 Helsingør, Denmark.
authors.forename: Mar
authors.initials: M
authors.lastname: Benavides
authors.affiliation: Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France.
authors.forename: Hugo
authors.initials: H
authors.lastname: Berthelot
authors.affiliation: Lamont-Doherty Earth Observatory, Division of Biology and Paleo Environment, Columbia University, PO Box 1000, 61 Route 9W, Palisades, New York 10964, USA.
authors.forename: Solange
authors.initials: S
authors.lastname: Duhamel
authors.affiliation: Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Raimbault
authors.affiliation: Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 98848, Noumea, New Caledonia.
authors.forename: Sophie
authors.initials: S
authors.lastname: Bonnet
mesh_terms: D002247:Carbon Isotopes; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes; D009930:Organic Chemicals / Q000378:metabolism*; D010140:Pacific Ocean; D012623:Seawater / Q000737:chemistry; D012995:Solubility; D000072359:Trichodesmium / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D009930:Organic Chemicals