@article{fdi:010088690,
  title = {{Q}uantifying {N}2 fixation and its contribution to export production near the {T}onga-{K}ermadec {A}rc using nitrogen isotope budgets},
  author = {{F}orrer, {H}. {J}. and {B}onnet, {S}ophie and {T}homas, {R}. {K}. and {G}rosso, {O}. and {G}uieu, {C}. and {K}napp, {A}. {N}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he spatial distribution of marine di-nitrogen ({N}-2) fixation informs our understanding of the sensitivities of this process as well as the potential for this new nitrogen ({N}) source to drive export production, influencing the global carbon ({C}) cycle and climate. {U}sing geochemically-derived delta {N}-15 budgets, we quantified rates of {N}-2 fixation and its importance for supporting export production at stations sampled near the southwest {P}acific {T}onga-{K}ermadec {A}rc. {R}ecent observations indicate that shallow (<300 m) hydrothermal vents located along the arc provide significant dissolved iron to the euphotic zone, stimulating {N}-2 fixation. {H}ere we compare measurements of water column delta {N}-15({NO}3+{NO}2) with sinking particulate delta {N}-15 collected by short-term sediment traps deployed at 170 m and 270 m at stations in close proximity to subsurface hydrothermal activity, and the delta {N}-15 of {N}-2 fixation. {R}esults from the delta {N}-15 budgets yield high geochemically-based {N}-2 fixation rates (282 to 638 <mu>mol {N} m(-2) d(-1)) at stations impacted by hydrothermal activity, supporting 64 to 92% of export production in late spring. {T}hese results are consistent with contemporaneous {N}-15(2) uptake rate estimates and molecular work describing high {T}richodesmium spp. and other diazotroph abundances associated with elevated {N}-2 fixation rates. {F}urther, the delta {N}-15 of sinking particulate {N} collected at 1000 m over an annual cycle revealed sinking fluxes peaked in the summer and coincided with the lowest delta {N}-15, while lower winter sinking fluxes had the highest delta {N}-15, indicating isotopically distinct {N} sources supporting export seasonally, and aligning with observations from most other delta {N}-15 budgets in oligotrophic regions. {C}onsequently, the significant regional {N}-2 fixation input to the late spring/summer {W}estern {T}ropical {S}outh {P}acific results in the accumulation of low-delta {N}-15({NO}3+{NO}2) in the upper thermocline that works to lower the elevated delta {N}-15({NO}3+{NO}2) generated in the oxygen deficient zones in the {E}astern {T}ropical {S}outh {P}acific.},
  keywords = {{N}-2 fixation ; nitrate d15{N} ; {T}onga {A}rc ; {S}outh {P}acific ; hydrothermal vents ; d15{N} budget ; {PACIFIQUE} ; {ZONE} {TROPICALE} ; {TONGA} ; {PACIFIQUE} {SUD}},
  booktitle = {},
  journal = {{F}rontiers in {M}arine {S}cience},
  volume = {10},
  numero = {},
  pages = {1249115 [14 p.]},
  year = {2023},
  DOI = {10.3389/fmars.2023.1249115},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088690},
}