Reviews and syntheses: Methane biogeochemistry in Sundarbans mangrove ecosystem, NE coast of India; a box modeling approach

Other literature type English OPEN
Dutta, Manab Kumar ; Mukhopadhyay, Sandip Kumar (2016)

Biogeochemical cycling of CH<sub>4</sub> was studied in Sundarbans mangrove system during June 2010 to December 2012. The sediment was CH<sub>4</sub> supersaturated with mean production potential of 3547 and 48.88 ┬Ámol m<sup>&minus;3</sup> d<sup>&minus;1</sup>, respectively in case of intertidal (0&ndash;25 cm depth) and sub-tidal sediments (first 5 cm depth). This induces significant CH<sub>4</sub> out-flux from sediment to estuary via advective and diffusive transports. Mean advective (from intertidal sediment) and diffusive (from sub-tidal sediment) CH<sub>4</sub> fluxes were 159.52 &mu;mol m<sup>&minus;2</sup> d<sup>&minus;1</sup> and 8.45 &mu;mol m<sup>&minus;2</sup> d<sup>&minus;1</sup>, respectively. Intertidal sediment CH<sub>4</sub> emission rate was about 4 times higher than surface layer CH<sub>4</sub> oxidation rate; indicating petite methanotrophic activity in mangrove sediment. Mean CH<sub>4</sub> concentration in estuarine surface and bottom waters were 69.90 and 56.17 nM, respectively. CH<sub>4</sub> oxidation in estuarine water column being 14 times higher than water&ndash;atmosphere exchange is considered as principal CH<sub>4</sub> removal mechanism in this estuary. Mean CH<sub>4</sub> mixing ratio over the mangrove forest atmosphere was 2.013 ppmv. The ecosystem acts a source of CH<sub>4</sub> to the upper atmosphere having mean biosphere&ndash;atmosphere exchange flux of 0.086 mg m<sup>&minus;2</sup> d<sup>&minus;1</sup>. Mean CH<sub>4</sub> photo-oxidation rate in the mangrove forest atmosphere was 3.25 &times; 10<sup>-9</sup> mg cm<sup>&minus;3</sup> d<sup>&minus;1</sup> and is considered as principal CH<sub>4</sub> removal mechanism in the forest atmosphere. Finally, a box model presenting CH<sub>4</sub> biogeochemistry in Sundarbans biosphere reserve has been drafted and was used to demonstrate CH<sub>4</sub> budget in this ecosystem.
Share - Bookmark