FN Archimer Export Format
PT J
TI N2 fixation as a dominant new N source in the western tropical South Pacific Ocean (OUTPACE cruise)
BT 
AF CAFFIN, Mathieu
   MOUTIN, Thierry
   FOSTER, Rachel Ann
   BOURUET-AUBERTOT, Pascale
   DOGLIOLI, Andrea Michelangelo
   BERTHELOT, Hugo
   GUIEU, Cecile
   GROSSO, Olivier
   HELIAS-NUNIGE, Sandra
   LEBLOND, Nathalie
   GIMENEZ, Audrey
   PETRENKO, Anne Alexandra
   DE VERNEIL, Alain
   BONNET, Sophie
AS 1:1;2:1;3:2;4:3;5:1;6:1,4;7:5,6;8:1;9:1;10:7;11:1;12:1;13:1,9;14:8;
FF 1:;2:;3:;4:;5:;6:;7:;8:;9:;10:;11:;12:;13:;14:;
C1 Univ Toulon & Var, Aix Marseille Univ, CNRS, IRD, MIO UM 110, F-13288 Marseille, France.
   Stockholm Univ, Dept Ecol Environm & Plant Sci, Stockholm, Sweden.
   UPMC Univ Paris 06, LOCEAN, Sorbonne Univ, Paris, France.
   Univ Brest, UMR CNRS UBO IRD Ifremer 6539, IUEM, Lab Sci Environm Marin, Plouzane, France.
   UPMC Univ Paris 06, CNRS, LOV, Sorbonne Univ, F-06230 Villefranche Sur Mer, France.
   New York Univ Abu Dhabi, Ctr Prototype Climate Modeling, Abu Dhabi, U Arab Emirates.
   Observ Oceanol Villefranche, Lab Oceanog Villefranche, UMR 7093, Villefranche Sur Mer, France.
   Univ Toulon & Var, Aix Marseille Univ, CNRS, IRD,OSU Pytheas,MIO,UM 110, Noumea 98848, New Caledonia.
   New York Univ Abu Dhabi, Ctr Prototype Climate Modeling, Abu Dhabi, U Arab Emirates.
C2 UNIV TOULON, FRANCE
   UNIV STOCKHOLM, SWEDEN
   UNIV PARIS 06, FRANCE
   UBO, FRANCE
   UNIV PARIS 06, FRANCE
   UNIV ABU DHABI, UNITED ARAB EMIRATES
   UNIV PARIS 06, FRANCE
   CNRS, FRANCE
   UNIV ABU DHABI, UNITED ARAB EMIRATES
UM LEMAR
IN DOAJ
IF 3.951
TC 41
UR https://archimer.ifremer.fr/doc/00439/55074/56503.pdf
   https://archimer.ifremer.fr/doc/00439/55074/56504.pdf
LA English
DT Article
CR MD 188 / KEOPS 2
   OUTPACE
BO Marion Dufresne
   L'Atalante
AB We performed nitrogen (N) budgets in the photic layer of three contrasting stations representing different trophic conditions in the western tropical South Pacific (WTSP) Ocean during austral summer conditions (February–March 2015). Using a Lagrangian strategy, we sampled the same water mass for the entire duration of each long-duration (5 days) station, allowing us to consider only vertical exchanges for the budgets. We quantified all major vertical N fluxes both entering (N2 fixation, nitrate turbulent diffusion, atmospheric deposition) and leaving the photic layer (particulate N export). The three stations were characterized by a strong nitracline and contrasted deep chlorophyll maximum depths, which were lower in the oligotrophic Melanesian archipelago (MA, stations LD A and LD B) than in the ultra-oligotrophic waters of the South Pacific Gyre (SPG, station LD C). N2 fixation rates were extremely high at both LD A (593 ± 51 µmol N m−2 d−1) and LD B (706 ± 302 µmol N m−2 d−1), and the diazotroph community was dominated by Trichodesmium. N2 fixation rates were lower (59 ± 16 µmol N m−2 d−1) at LD C, and the diazotroph community was dominated by unicellular N2-fixing cyanobacteria (UCYN). At all stations, N2 fixation was the major source of new N (> 90 %) before atmospheric deposition and upward nitrate fluxes induced by turbulence. N2 fixation contributed circa 13–18 % of primary production in the MA region and 3 % in the SPG water and sustained nearly all new primary production at all stations. The e ratio (e ratio  =  particulate carbon export ∕ primary production) was maximum at LD A (9.7 %) and was higher than the e ratio in most studied oligotrophic regions (< 5 %), indicating a high efficiency of the WTSP to export carbon relative to primary production. The direct export of diazotrophs assessed by qPCR of the nifH gene in sediment traps represented up to 30.6 % of the PC export at LD A, while their contribution was 5 and < 0.1 % at LD B and LD C, respectively. At the three studied stations, the sum of all N input to the photic layer exceeded the N output through organic matter export. This disequilibrium leading to N accumulation in the upper layer appears as a characteristic of the WTSP during the summer season. 
PY 2018
PD MAY
SO Biogeosciences
SN 1726-4170
PU Copernicus Gesellschaft Mbh
VL 15
IS 8
UT 000431271100001
BP 2565
EP 2585
DI 10.5194/bg-15-2565-2018
ID 55074
ER

EF