The Sundarbans represent the largest mangrove system on Earth, covering >10,000 km2. These mangroves can export a vast amount of aquatic carbon that can be potentially sequestered for millennia. Dr Kousik Das, Assistant Professor at the Department of Environmental Science and Engineering, collaborates with Southern Cross University, Australia and IIT Kharagpur to conduct breakthrough research to analyse and estimate the carbon flux between the Sunderbans and the Bay of Bengal. He has published a research paper titled “Groundwater discharge and bank overtopping drive large carbon exports from Indian Sundarban mangroves” in the Q1 journal Science of The Total Environment, having an impact factor of 8.2.
Abstract
We estimate porewater-driven carbon exchange between the Sundarbans and the Bay of Bengal using high-resolution time series and a radon groundwater mass balance approach spanning a neap-spring tidal cycle. Submarine groundwater discharge (SGD) increased from neap to spring tides by 352 % up to a maximum of 65.6 cm d−1 largely driven by creek bank overtopping after the mid-tide. Exports of dissolved organic and inorganic carbon and alkalinity doubled between neap and spring, likely due to the ‘first flush’ of older porewater in the mangrove flats. Groundwater discharge was a significant driver of the net carbon export, contributing up to 86.7 % of DIC and 74.0 % of alkalinity during the spring tide while contributing a lower proportion of DOC (4 %–23 %). If these results are representative of the Sundarbans more broadly, carbon fluxes from the Sundarbans would be more than an order of magnitude higher than some of the world’s largest rivers on an areal basis, highlighting the importance of Sundarbans mangroves to global oceanic carbon budgets.
Practical Implementation/Social Implications of the Research
This study shows the global importance of the Sundarbans mangrove system, with significant dissolved inorganic carbon and total alkalinity fluxes to the Bay of Bengal. It also shows that mangrove SGD is an important driver of dissolved inorganic carbon, dissolved inorganic carbon (DIC) and total alkalinity (TAlk) exports and that bank overtopping during mid and spring tides drives a ‘first flush’ of carbon from groundwater. When carbon fluxes from the study site were upscaled to the entire inundated area of the Sundarbans, DIC and TAlk exports were smaller than some of the world’s largest rivers, however when adjusted to the catchment size (assuming the Sundarbans mangrove catchment area is the extent of the mangroves; 10,200 km2), the areal carbon fluxes from the mangroves are more than an order of magnitude higher than these river systems
Dr Das aims to continue his research and further explore the large flux of carbon export due to tropical cyclones from the Indian Sundarbans to the Bay of Bengal.
