Guieu C. auteur aut IRD Bonnet Sophie auteur aut IRD Petrenko A. auteur aut IRD Menkès Christophe auteur aut IRD Chavagnac V. auteur aut IRD Desboeufs K. auteur aut IRD Maes Christophe auteur aut IRD Moutin T. auteur aut IRD text journalArticle eng text/pdf reformatted digital access In the Western Tropical South Pacific, patches of high chlorophyll concentrations linked to the occurrence of N-2-fixing organisms are found in the vicinity of volcanic islands. The survival of these organisms relies on a high bioavailable iron supply whose origin and fluxes remain unknown. Here, we measured high dissolved iron (DFe) concentrations (up to 66 nM) in the euphotic layer, extending zonally over 10 degrees longitude (174 E-175 W) at similar to 20 degrees S latitude. DFe atmospheric fluxes were at the lower end of reported values of the remote ocean and could not explain the high DFe concentrations measured in the water column in the vicinity of Tonga. We argue that the high DFe concentrations may be sustained by a submarine source, also characterized by freshwater input and recorded as salinity anomalies by Argo float in situ measurements and atlas data. The observed negative salinity anomalies are reproduced by simulations from a general ocean circulation model. Submarine iron sources reaching the euphotic layer may impact nitrogen fixation across the whole region. specialized PACIFIQUE ZONE TROPICALE 032 8 art. 9075 [9 p.] 2018 2045-2322 https://www.documentation.ird.fr/hor/fdi:010073162 10.1038/s41598-018-27407-z 2045-2322 [F B010073162] https://www.documentation.ird.fr/hor/fdi:010073162 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers18-08/010073162.pdf IRD - Base Horizon / Pleins textes 2018-09-03 2023-07-11 fdi:010073162 fre