@article{fdi:010068122,
  title = {{B}iogeochemical and biological impacts of diazotroph blooms in a low-nutrient, low-chlorophyll ecosystem : synthesis from the {VAHINE} mesocosm experiment ({N}ew {C}aledonia)},
  author = {{B}onnet, {S}ophie and {B}aklouti, {M}. and {G}imenez, {A}. and {B}erthelot, {H}. and {B}erman-{F}rank, {I}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n marine ecosystems, biological {N}-2 fixation provides the predominant external source of nitrogen ({N}; 140a{E}uro-+/- a{E}uro-50a{E}uro-{T}ga{E}uro-{N}a{E}uro-yr(-1)), contributing more than atmospheric and riverine inputs to the {N} supply. {Y}et the fate and magnitude of the newly fixed {N}, or diazotroph-derived {N} (hereafter named {DDN}) in marine ecosystems is poorly understood. {M}oreover, whether the {DDN} is preferentially and directly exported out of the photic zone, recycled by the microbial loop and/or transferred into larger organisms remains unclear. {T}hese questions were investigated in the framework of the {VAHINE} ({VA}riability of vertical and trop{HI}c transfer of diazotroph derived {N} in the south w{E}st {P}acific) project. {T}riplicate large volume ( similar to a{E}uro parts per thousand a{E}uro-50a{E}uro-m(3)) mesocosms were deployed in the tropical south-west {P}acific coastal ocean ({N}ew {C}aledonia). {T}he mesocosms were intentionally fertilized with similar to a{E}uro parts per thousand a{E}uro-0.8a{E}uro-{A} mu {M} dissolved inorganic phosphorus ({DIP}) at the start of the experiment to stimulate diazotrophy. {A} total of 47 stocks, fluxes, enzymatic activities and diversity parameters were measured daily inside and outside the mesocosms by the 40 scientists involved in the project. {T}he experiment lasted for 23 days and was characterized by two distinct and successive diazotroph blooms: a dominance of diatom-diazotroph associations ({DDA}s) during the first half of the experiment (days 2-14) followed by a bloom of unicellular cyanobacterial lineage {C} ({UCYN}-{C} during the second half of the experiment (days 15-23). {T}hese conditions provided a unique opportunity to compare the {DDN} transfer and export efficiency associated with different diazotrophs. {H}ere we summarize the major experimental and modelling results obtained during the project and described in the {VAHINE} special issue, in particular those regarding the evolution of the main standing stocks, fluxes and biological characteristics over the 23-day experiment, the contribution of {N}-2 fixation to export fluxes, the {DDN} released to dissolved pool and its transfer to the planktonic food web (bacteria, phytoplankton, zooplankton). {W}e then apply our {E}co3{M} modelling platform to further infer the fate of {DDN} in the ecosystem and the role of {N}-2 fixation on productivity, food web structure and carbon export. {R}ecommendations for future work are finally provided in the conclusion section.},
  keywords = {{NOUVELLE} {CALEDONIE} ; {PACIFIQUE} ; {NOUMEA} {LAGON}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {13},
  numero = {15},
  pages = {4461--4479},
  ISSN = {1726-4170},
  year = {2016},
  DOI = {10.5194/bg-13-4461-2016},
  URL = {https://www.documentation.ird.fr/hor/fdi:010068122},
}