Seasonal variation of core sediment biochemistry in the Kaikhali mangrove region of West Bengal

Sediments of mangrove ecosystem is a blue carbon resource in the form of geochemical composition, which is essential in influencing the climate change globally by sequestering carbon dioxide from the atmosphere and oceans at significantly high rates, per unit area than terrestrial forests. When these coastal ecosystems are degraded or converted to other land uses, these large stores of blue carbon resources are exposed and released as CO2 into the atmosphere leading to green-house effect and hence, global warming (2-6% of degradation of coastal ecosystems generates 3-19% of carbon emissions). Thus, characterization of Labile Organic Compounds (LOC) from mangrove surface and core sediments will help in source characterization of organic carbon compounds sequestration capacity of mangroves as a blue carbon resource. A retrospective study in mangrove sediments in West Bengal had been carried out in the year 2017 during pre-monsoon, monsoon and post-monsoon seasons which revealed the changes in composition of various biogeochemical compounds (LOC) with respect to seasons. The relative distribution of labile organic compounds (LOC in mg/g) on an average in mangrove sediments in West Bengal during pre-monsoon, the order is: total tannin and lignin (TT&L) (3.86±0.96) > total carbohydrates (CHO) (0.70±0.22) > total lipids (LPD) (0.66±0.39) > total proteins (PRT) (0.59±0.09); in monsoon: total tannin and lignin (TT&L) (4.02±0.69)> total lipids (LPD) (1.03±0.87) > total carbohydrates (CHO) (0.72±0.21) > total proteins (PRT) (0.07±0.04); and in post-monsoon: total tannin and lignin (TT&L) (3.41± 1.10) > total carbohydrates (CHO) (1.55±0.55) > total lipids (LPD) (0.25±0.14) > total proteins (PRT) (0.06±0.09). The selected area had been continuously degrading and emitting considerable fraction of free CO2 and other GHGs in atmosphere, thus, leading mother earth to stress condition due to increase in the adverse effect of global warming.