Coastal wetlands play an important role in nitrogen removal and are a vital blue carbon sink. The produced methane (CH4) in coastal wetlands has been recently identified as a possible carbon source for denitrification process, providing a significant contribution to coastal nitrogen cycling. However, the in-situ correlation between CH4 emissions and denitrification rate, as well as their coupling mechanism is still unclear. Here, we investigated the nitrogen removal pattern throughout a complete tidal cycle, quantified the in-situ linkage between CH4 emissions and denitrification rate, and explored the associated microbial mechanisms in the eutrophic coastal wetland. The results showed that (1) the removal of nitrogen was driven by the tidal cycle (marsh flooding and
drying), which involved two processes - physical interception and microbial denitrification; (2) the denitrification rate was linearly positively correlated to the CH4 emission (R2 = 0.87, p < 0.0001); (3) nitrite- and nitratedependent denitrifying anaerobic methane oxidation (DAMO) coexisted in the wetland sediment, and promoted nitrogen removal by utilizing CH4 as the carbon source for denitrification. Our findings suggested that CH4 emission could enhance denitrification via DAMO in the field, and deepened the understanding of the dynamic nitrogen removal process within eutrophic coastal wetlands, and further indicated a strong interaction between coastal carbon and nitrogen cycling.
a State Key Laboratory of Estuarine and Coastal Research, Institute of Eco-Chongming, Center for Blue Carbon Science and Technology, East China Normal University, 3663 N. Zhongshan Road, Shanghai, 200062, PR China
b Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, 500 Dong Chuan Road, Shanghai, 200241, PR China
c The Massachusetts Audubon Society, Lincoln, MA, 01773, USA
d Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station, Ministry of Education & Shanghai Science and Technology Committee, Shanghai, 202162, PR China