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Circulation, biogeochemistry and carbon cycling in ocean margins
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Using triple oxygen isotopes to constrain organic carbon production rates and nutrient regeneration in the marginal sea
Monday 7th @ 1130-1150, Concert Hall
Zhuoyi Zhu* , State Key Lab of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, PR China
Daniel A. Stopler, Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
Jun Wang, State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, 310012, PR China
Su-Mei Liu, Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, Ocean University of China/ Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266100, PR China
Shan Zheng, Jiaozhou Bay Marine Ecosystem Research Station, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Gui-Ling Zhang, Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, Ocean University of China/ Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266100, PR China
Xiao-Xia Sun, Jiaozhou Bay Marine Ecosystem Research Station, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Dong-Feng Xu, State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, 310012, PR China
Meng Zhou, Institute of Oceanography, Shanghai Jiao Tong University, Shanghai, 200030, PR China
Presenter Email: zyzhu@sklec.ecnu.edu.cn |
| On two cruises in the slope regions of northern South China Sea, in October, 2014 (autumn) and June, 2015 (spring), we measured gross oxygen production (GOP) and net oxygen production (NOP) in the mixed layer (ML) of station L07 (mean: 115.34E, 19.72N). We also constrained the effect of respiration effect on nutrient regeneration in the nitracline. GOP was estimated using triple oxygen isotopes of the dissolved O2, and the ML depth history was achieved by modeling to improve the precision of gas exchange term in GOP calculation process. GOP for October and June were 169 mmol O2/m2/day and 189 mmol O2/m2/day, respectively. Compared with the measurements of carbon fixation using 14C incubations (114C-P), we found a GOP/14C-P ratio of 6.1 for spring and 4.9 for autumn, respectively. Based on O2/Ar ratio, NOP at station L07 was 1.4 mmol O2/m2/day (autumn) and 8.0 mmol O2/m2/day (spring). In June, 2015, we encountered a warm eddy event which promoted downwelling whereas in Oct., 2014 there were no clear meso-scale features. Further, given the higher NOP/GOP ratio in Jun., the efficiency of organic carbon export out of ML is proposed to have been higher in June, 2015 relative to that in October, 2014. Beneath the ML, respiration discriminates against 18O. The apparent fractionation factor, deduced from a Rayleigh plot, is 0.988±0.001. Nutrient regeneration was related to water column respiration, reflected in covariation between nutrient concentration and AOU or 18O. |
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