Spatial Variability in Carbon Storage Among Dominant Mangrove Species in the Indian Sundarbans

Mangroves thrive on wetlands at land-sea interface and river mouths with significant capacity to store carbon because of their high productivity and low organic matter decomposition rates. The Indian Sundarban Biosphere Reserve (ISBR), with an area of 9630 km2. is in the lower stretch of the Gangetic delta and is a conglomeration of some 105 islands of varying sizes, each covered with mangroves. This study area is one of the World Heritage sites sustaining 34 species of true mangroves. We present here the carbon storage variability of five dominant mangrove species in 24 ISBR stations with varying salinity profiles. The Above Ground Biomass (AGB) was estimated for 110–125 trees per species in 120 plots (10 m × 10 m) from the intertidal mudflats of these 24 stations in low tide conditions during July 2023. The estimated mean AGB and the carbon stock were of the order Avicennia alba (AGB = 26.53 tonnes/ha; AGC = 12.78 tonnes/ha) > Avicennia marina (AGB = 20.88 tonnes/ha; AGC = 10.00 tonnes/ha) > Avicennia officinalis (AGB = 14.90 tonnes/ha; AGC = 7.10 tonnes/ha) > Sonneratia spp. (AGB = 6.52 tonnes/ha; AGC = 3.07 tonnes/ha) > Excoecaria agallocha (AGB = 5.56 tonnes/ha; AGC = 2.60 tonnes/ha) at stations with high salinity, but the order is Sonneratia spp. (AGB = 22.97 tonnes/ha; AGC = 10.98 tonnes/ha) > Avicennia alba (AGB = 17.75 tonnes/ha; AGC = 8.43 tonnes/ha) > Avicennia marina (AGB = 13.90 tonnes/ha; AGC = 6.56 tonnes/ha) > Avicennia officinalis (AGB = 9.73 tonnes/ha; AGC = 4.57 tonnes/ha) > Excoecaria agallocha (AGB = 5.41 tonnes/ha; AGC = 2.53 tonnes/ha) at stations exposed to relatively low saline water. The present mangrove system registered a significant oscillation in carbon storage potential with variation in aquatic salinity, which is the critical moderator of mangrove diversity, growth, and carbon storage potential in coastal and estuarine regions of the tropics.