Soil functional microbial pathways related to GHGs emissions of coastal degraded mangroves-rice ecologies in Sundarban, India: A soil metagenomic approach.

چکیده اصلی

Mangroves and their adjacent rice ecologies play a critical role in regulating greenhouse gas (GHGs) emissions, particularly in tropical coastal wetlands. This study assessed the impact of mangrove degradation on methane (CH4) and nitrous oxide (N2O) emissions by comparing two distinct ecosystems; degraded mangroves, and adjacent rice system in the Sundarban, India. Annual CH4 and N2O emissions were quantified and linked to soil microbial energy metabolism pathways; methanogenesis, methanotrophy, sulphur (S), and nitrogen (N) metabolism by using whole-genome metagenomic analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologs was used for functional microbial pathway analysis. Acetoclastic pathway was found to be the dominant CH4 production pathway in rice, where relatively low soil salinity favored CO2 to CH4 conversion. Methane oxidation was higher in degraded mangroves, driven by the serine and xylulose monophosphate pathways, reflecting microbial adaptation to saline and alkaline conditions. The assimilatory pathway (AMP) dominated S metabolism, with adenosine phosphosulfate kinase more abundant in degraded mangroves and adenosine triphosphate sulfurylase in rice ecology. Denitrification was the primary N pathway in degraded mangroves and adjacent rice systems, while dissimilatory nitrate reduction to ammonium (DNRA) prevailed in rice. A higher abundance of enzymes involved in acetate to methane production pathway was observed in rice systems, indicating greater CH4 production potential, whereas a higher abundance of phosphoserine aminotransferase in serine pathways in degraded mangroves suggested relatively higher potential for CH4 oxidation. These results demonstrate that targeted microbial management in mangrove-rice ecologies could serve as a promising strategy for climate change mitigation in coastal ecology.

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