Introduction to the project VAHINE : VAriability of vertical and tropHlc transfer of diazotroph derived N in the south wEst Pacific

Introduction to the project VAHINE : VAriability of vertical and tropHlc transfer of diazotroph derived N in the south wEst Pacific Bonnet Sophie auteur aut IRD Moutin T. auteur aut IRD Rodier Martine auteur aut IRD Grisoni J. M. auteur aut IRD Louis F. auteur aut IRD Folcher Eric auteur aut IRD Bourgeois Bertrand auteur aut IRD Boré Jean-Michel auteur aut IRD Renaud Armelle auteur aut IRD text journalArticle eng text/pdf reformatted digital access On the global scale, N-2 fixation provides the major external source of reactive nitrogen to the surface ocean, surpassing atmospheric and riverine inputs, and sustains similar to 50 % of new primary production in oligotrophic environments. The main goal of the VAriability of vertical and tropHlc transfer of diazotroph derived N in the south wEst Pacific (VAHINE) project was to study the fate of nitrogen newly fixed by diazotrophs (or diazotroph-derived nitrogen) in oceanic food webs, and how it impacts heterotrophic bacteria, phytoplankton and zooplankton dynamics, stocks and fluxes of biogenic elements and particle export. Three large volume (similar to 50 m(3)) mesocosms were deployed in a tropical oligotrophic ecosystem (the New Caledonia lagoon, southeastern Pacific) and intentionally fertilized with similar to 0.8 mu M of dissolved inorganic phosphorus (DIP) to stimulate diazotrophy and follow subsequent ecosystem changes. VAHINE was a multidisciplinary project involving close collaborations between biogeochemists, molecular ecologist, chemists, marine opticians and modellers. This introductory paper describes in detail the scientific objectives of the project as well as the implementation plan: the mesocosm description and deployment, the selection of the study site (New Caledonian lagoon), and the logistical and sampling strategy. The main hydrological and biogeochemical conditions of the study site before the mesocosm deployment and during the experiment itself are described, and a general overview of the papers published in this special issue is presented. specialized NOUVELLE CALEDONIE PACIFIQUE 036 021 Biogeosciences 13 9 2803-2814 2016 1726-4170 https://www.documentation.ird.fr/hor/fdi:010066985 10.5194/bg-13-2803-2016 1726-4170 [F B010066985] https://www.documentation.ird.fr/hor/fdi:010066985 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers16-07/010066985.pdf IRD - Base Horizon / Pleins textes 2016-08-01 2020-11-09 fdi:010066985 fre