Status: this preprint was under review for the journal BG but the revision was not accepted.
Reviews and syntheses: Methane biogeochemistry in Sundarbans mangrove ecosystem, NE coast of India; a box modeling approach
Manab Kumar Duttaand Sandip Kumar Mukhopadhyay
Abstract. Biogeochemical cycling of CH4 was studied in Sundarbans mangrove system during June 2010 to December 2012. The sediment was CH4 supersaturated with mean production potential of 3547 and 48.88 µmol m−3 d−1, respectively in case of intertidal (0–25 cm depth) and sub-tidal sediments (first 5 cm depth). This induces significant CH4 out-flux from sediment to estuary via advective and diffusive transports. Mean advective (from intertidal sediment) and diffusive (from sub-tidal sediment) CH4 fluxes were 159.52 μmol m−2 d−1 and 8.45 μmol m−2 d−1, respectively. Intertidal sediment CH4 emission rate was about 4 times higher than surface layer CH4 oxidation rate; indicating petite methanotrophic activity in mangrove sediment. Mean CH4 concentration in estuarine surface and bottom waters were 69.90 and 56.17 nM, respectively. CH4 oxidation in estuarine water column being 14 times higher than water–atmosphere exchange is considered as principal CH4 removal mechanism in this estuary. Mean CH4 mixing ratio over the mangrove forest atmosphere was 2.013 ppmv. The ecosystem acts a source of CH4 to the upper atmosphere having mean biosphere–atmosphere exchange flux of 0.086 mg m−2 d−1. Mean CH4 photo-oxidation rate in the mangrove forest atmosphere was 3.25 × 10-9 mg cm−3 d−1 and is considered as principal CH4 removal mechanism in the forest atmosphere. Finally, a box model presenting CH4 biogeochemistry in Sundarbans biosphere reserve has been drafted and was used to demonstrate CH4 budget in this ecosystem.
Received: 18 Feb 2016 – Discussion started: 25 Feb 2016
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This study made an detailed understanding on production, consumption and fluxes of methane from different sub-ecosystems of Sundarbans mangrove forest. The mangrove environment was found to be rich in organic carbon content as well as methane concentration. A most of the produced methane transported to the atmosphere where 85 % of total supply undergoes photo-oxidation. Like sediment estuaries are also methane supersatuarated and about 70 % of methane within estuary undergoes microbial oxidation.
This study made an detailed understanding on production, consumption and fluxes of methane from...
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