Nitrate-dependent anaerobic methane oxidation in subtropical mangrove soils and the environmental and ecological implication

Abstract Nitrate-dependent anaerobic methane oxidation (N-DAMO) links the oxidation of greenhouse gases with the removal of nitrogen oxide, and such a linkage constitutes distinctive carbon-nitrogen coupling. This study utilizes a laboratory slurry incubation, carbon isotope tracing, and metagenomic techniques to explore the N-DAMO process in mangrove soils and measure its reaction rate. In addition, review on the N-DAMO processes in fifty-two different ecosystems around the world is conducted to further reveal the environmental and ecological impact of the N-DAMO process in mangrove soils. The results indicated that the N-DAMO rate in mangrove soil was 63.62 ± 0.39 nmol CO2-C g− 1 d− 1, and the N-DAMO process converted over 60% of the CH4 generated by mangrove soils to CO2. Without the N-DAMO process, the CH4 emissions of mangrove soils would increase by 2.5 folds. Moreover, the nitrogen removal rate of this process was 169.66 ± 1.04 nmol N g− 1 d− 1, which demonstrated an obvious purification effect. Hence, the N-DAMO process is critical to balance C/N values in mangrove soils. Existing studies have shown that high-levels of N-DAMO exist in rivers/lakes, peatlands, and wetland ecosystems. Among the wetland ecosystems, the rate of the N-DAMO process in mangrove soils is higher. This study deepens the understanding of coupling biogeochemical cycle of carbon and nitrogen and provides a scientific basis for an accurate assessment of blue carbon sink functionality in mangrove soils.