Global mapping of flux and microbial sources for oceanic N<sub>2</sub>O.

Wang, Shuo; Huang, Jilin; Wu, Zhen; Li, Shengjie; Zhu, Xianfang; Liu, Yong; Ji, Guodong · Nat Commun · 2025

basic_science · Level V

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Abstract

The ocean is the largest source of N<sub>2</sub>O emissions from global aquatic ecosystems. However, the N<sub>2</sub>O production-consumption mechanism and microbial spatial distribution are still unclear. Our study established a bottom-up model based on the source‒sink boundary and the microbial sources of N<sub>2</sub>O. A high-resolution (0.1°) global distribution of oceanic N<sub>2</sub>O was depicted, confirmed by approximately 150,000 surface measurements. The microbial N<sub>2</sub>O flux is 2.9 Tg/yr N-N<sub>2</sub>O, with the oxygen-deficient zones (ODZs) disproportionately accounting for more than half of the total emission. High primary productivity, sharp oxyclines, and shallow emission depths caused the ODZs to be N<sub>2</sub>O hotspots. Geographically, ammonia-oxidizing archaea (AOA, 1.0 Tg) are the most widely distributed contributors to N<sub>2</sub>O emissions in the ocean, completely overtaking ammonia-oxidizing bacteria (AOB). Heterotrophic denitrification, mainly occurring in ODZs, contributes the most (1.6 Tg) to N<sub>2</sub>O emissions. Overall, this study offers a bottom-up framework for understanding microbial source-sink mechanism in the ocean.

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