Methane Emissions from Estuarine Coastal Wetlands: Implications for Global Change Effect

Abstract

Core Ideas We investigated estuarine environmental factors on CH4 flux from two vegetation communities. Warming significantly affected on CH4 emission from the Phragmites australis community. There was a significant correlation between CH4 flux and water level in both communities. Salinity significantly affects CH4 emissions from the Phragmites australis community. The interaction between temperature and water level was the most important factor controlling CH4 flux. Global warming, rising sea levels, and saltwater intrusion interact to affect carbon cycling, specifically methane (CH4) flux in estuarine coastal wetlands. In the present study, Phragmites australis and Spartina alterniflora communities in the intertidal zone of the Yangtze estuary were selected for investigating CH4 flux under different temperature (natural/warming), water level (high/low), and salinity (0, 5, 15, and 30‰) conditions. The average CH4 flux (from April to October 2016) under natural conditions was 141.0 ± 21.5 and 502.8 ± 65.3 μmol m−2 h−1 for P. australis and S. alterniflora communities, respectively. Warming had a particularly pronounced effect on CH4 emissions from the P. australis community and increased CH4 flux by 130%. There was a significant correlation between CH4 flux and water level; at high water levels, CH4 flux was 2.64‐ and 3.78‐fold higher in P. australis and S. alterniflora communities, respectively. Salinity had a significant pronounced effect on CH4 emissions from the P. australis community, and there was a clear order (5‰ > 15‰ > 0‰ > 30‰) in CH4 flux. The interaction between temperature and water level was the most important factor controlling CH4 flux from wetlands; CH4 emissions were greater at higher temperature and higher water levels. However, at low water level, the effect of salinity was more prominent. The results suggest that CH4 flux from estuarine wetlands could be further enhanced in the future under the influence of rising sea levels due to global warming.