Seasonal Variation of Methane Fluxes in a Mangrove Ecosystem in South India: An Eddy Covariance-Based Approach

The atmospheric methane (CH 4 ) concentration has increased in recent years due to natural and anthropogenic causes. Hence, it is essential to quantify the potential sources of CH 4 to understand the factors responsible for its fluxes on a local to regional scale through in situ observations. Coastal wetlands, particularly the mangrove ecosystems in the tropical and subtropical coasts, are significant sources of CH 4 . In this study, we used an eddy covariance-based technique to measure the CH 4 fluxes in a mangrove ecosystem in Pichavaram, South India. The daily mean CH 4 flux ranged from 12 to 26 nmol m −2 s −1 during the wet season and from 6 to 20 nmol m –2 s –1 during the dry season. The monthly mean flux during the wet period was between 0.8 and 1.8 g CH 4 m −2 month −1 , and in the dry season, it was between 0.4 and 0.6 g CH 4 m −2 month −1 . The visual correlogram and structural equation modelling technique revealed that air temperature, creek water dissolved oxygen, soil organic carbon, and redox potential are important factors that control the CH 4 fluxes. The results suggest that the Pichavaram mangrove wetland acts as a source for CH 4 . Our results also indicate that tidal inundation and seasonal variations in atmospheric temperature and water salinity are key factors affecting the CH 4 flux in the Pichavaram mangrove ecosystem.