Polluted waters of the reclaimed islands of Indian Sundarban promote more greenhouse gas emissions from mangrove ecosystem

The rapid increase in atmospheric greenhouse gas (GHG) emissions in the mangrove ecosystem are causing serious concern. Some of the coastal reclaimed islands of Sundarban mangrove ecosystem in India were studied for environmental variables and soil-atmosphere fluxes mainly, methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). Gas samples were taken from the mangrove bed during three seasons; pre-monsoon, monsoon, and post-monsoon. Monsoonal CH4 fluxes were higher than pre- and post-monsoon, resulting in a rise in the number of pneumatophores, making transpiration easier. CO2 emission was higher in monsoon due to increased microbial soil respiration. Whereas N2O fluxes were higher in pre-monsoon followed by monsoon and post-monsoon period because of a higher denitrifying rates as a function of soil temperature. Considering the importance of GHG fluxes, an ANN (artificial neural networking) model is proposed for forecasting and sensitivity analysis of different environmental variables and GHG emissions. The most sensitive environmental factor was the soil nitrate content affecting the GHG emissions. Principal component analysis showed that the litterfall biomass was strongly correlated with the soil oxygen reduction potential. A GIS (geographic information system) based correlation was done between the site wise GHG emissions and water quality index to determine the relationship between GHG emission and water pollution. Sagar is the most polluted island in Sundarban mangrove ecosystem due to large urbanization. The proposed model would serve as a guide for environmental managers to evaluate the pollution process in various parts of the world.

Automated summary

The study of gas emissions in the mangrove ecosystem reveals seasonal variations in methane, carbon dioxide, and nitrous oxide fluxes, with pneumatophore numbers increasing and making transpiration easier. The most critical environmental factor is the soil nitrate content, which will provide valuable information to environmental managers.