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General Session 3: Biological oceanography & global change |
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Biologically-associated Nitrous Oxide (N2O) accumulation in sunlit ocean
GS3-54-S
Xianhui Wan* , State Key Laboratory of Marine Environmental Science, Xiamen University, China
Huaxia Sheng, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Minhan Dai, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Shuh-Ji kao, State Key Laboratory of Marine Environmental Science, Xiamen University, China
Presenter Email: wanxh@xmu.edu.cn
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| The largest uncertainty and inconsistency in global marine N2O emission estimate appear in the euphotic zone, where light and phytoplankton competition may inhibit nitrification, a major contributor to N2O production. The rigorous physical disturbance in the surface ocean prevents N2O accumulation thus potentially masking the role of biological N2O production. Here we presented high vertical resolution N2O profiles in the euphotic zone of the oligotrophic South China Sea. Distinctive N2O peaks, which deviated from the vertical mixing curve, were observed near the nitracline, of which the maximum of Chl-a and nitrite appeared correspondingly. The intimate association between N2O excursion and biological parameters suggests that extra source in the euphotic zone is required to support such N2O offset. By using isotopic labeling technique, we measured rates and explored the potential processes (ammonium oxidation and nitrite reduction) associated with N2O production. Higher vertical resolution observation and process studies are urgently needed to explore the spatial-temporal distribution of euphotic zone N2O production and its controlling mechanisms to fill the knowledge gap. |
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