TY - JOUR T1 - Carbon-Based Estimate of Nitrogen Fixation-Derived Net Community Production in N-Depleted Ocean Gyres A1 - Ko,Young Ho A1 - Lee,Kitack A1 - Takahashi,Taro A1 - Karl,David M. A1 - Kang,Sung-Ho A1 - Lee,Eunil AD - Pohang Univ Sci & Technol, Div Environm Sci & Engn, Pohang, South Korea. AD - Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY USA. AD - Univ Hawaii Manoa, Daniel K Inouye Ctr Microbial Oceanog Res & Educ, Honolulu, HI 96822 USA. AD - KIOST, Korea Polar Res Inst, Div Polar Ocean Sci, Incheon, South Korea. AD - Korea Hydrog & Oceanog Agcy, Ocean Res Div, Busan, South Korea. UR - https://archimer.ifremer.fr/doc/00675/78683/ DO - 10.1029/2017GB005634 KW - net community production KW - nitrogen fixation KW - seasonal carbon drawdown KW - oligotrophic ocean gyre N2 - Accurate estimation of net community production (NCP) in the ocean is important for determining the future trend for carbon dioxide concentrations in the atmosphere and thus for understanding the global carbon cycle and climate change. Most methods for measuring NCP rely on analysis of dissolved fixed inorganic nitrogen species (N), which are believed to be limiting factors for NCP. However, in the vast areas of the ocean gyres only low levels of N are available for phytoplankton during much of the year. In this study the NCP was estimated by summing the seasonal reduction in the concentration of dissolved inorganic carbon (C-T) in the surface mixed layer, corrected for changes associated with salinity variation, net air-sea CO2 flux, horizontal C advection, non-Redfield diffusive C and N fluxes (deviations from the C:N ratio of 7), and anthropogenic nitrogen deposition. The mixed layer reduction in C-T was calculated from an annual C-T cycle, deduced from comprehensive records of surface pCO(2) and total alkalinity, using an established thermodynamic model. This method yielded a value of 0.6 +/- 0.2Pg of C, which represents the NCP that occurred during the warming period (approximately 8 months) in the nitrate-depleted (<0.2 mu mol/kg) ocean. Our estimate is broadly consistent with the global N-2 fixation rate estimated using the N-15-based method and suggests that N-2 fixation by microorganisms is a major driver for this NCP. Y1 - 2018/08 PB - Amer Geophysical Union JF - Global Biogeochemical Cycles SN - 0886-6236 VL - 32 IS - 8 SP - 1241 EP - 1252 ID - 78683 ER -