Submerged macrophytes enhance carbon emission (CO2 and CH4) from the freshwater wetland in Keibul Lamjao National Park, Manipur, India

Worldwide, the exacerbation of global warming has accelerated the growth of submerged macrophytes in wetlands, thereby substantiating the supply of labile substrates for carbon (CH₄ and CO₂) emissions. Nevertheless, limited studies have been conducted on carbon emission from tropical wetlands with submerged macrophytes. In the current study an attempt has been made to reveal the role of submerged macrophytes in influencing carbon flux from a natural wetland in the Indo-Burma Biodiversity hotspots. The submerged macrophytes colonising the shallow freshwater wetland of Keibul Lamjao comprise of Hydrilla verticillata, Ceratophyllum demersum, and Potamogeton crispus, with primary productivity at community level ranging between 20.72 and 152.53 g m^-2 d^-1 (mean, 95.6 ± 54.66 g m^-2 d^-1). This study gives a comparative analysis of the carbon gases (CH₄ and CO₂) emission in two distinct zones of the wetland: areas with profuse submerged macrophytic growth and water free of macrophytes. The mean CO₂ and CH₄ emissions from the zone with submerged macrophytes were 8362.64 ± 2935.57 and 227.90 ± 73.50 mg m^-2 d^-1, respectively, compared to 5558.07 ± 1222.05 and 149.72 ± 20.44 mg m^-2 d^-1 from those without macrophytes. The CO₂ and CH₄ emissions peak during the summer and wane in the following seasons, with minimum emissions occurring during the winter. It is apparent from the results that the generation of the gases in the wetland was temperature dependent, plus the macrophytic detritus availability. The carbon emissions were significantly correlated with the physicochemical properties of the water and the lake bottom sediment. A significantly positive correlation between carbon emission and dissolved organic carbon (DOC) and organic matter (OM) was established in the zone with macrophytes, thereby revealing that the growth of submerged macrophytes in the wetland enhances atmospheric carbon emissions.