Dr. V. RaniDr. P. PadmavathyMr. T. AnandMr. Picko Sanggrik W Sangma2022-08-102022-08-102021https://krishikosh.egranth.ac.in/handle/1/5810186167The present study was conducted to assess the carbon sequestration potential of Avicennia marina and Salicornia brachiata in coastal regions of Nagapattinam and Thoothukudi for the period of three different monsoon seasons in a year. The leaves, stem and root of mangrove A. marina and salt marsh plant S. brachiata were collected from the two locations, Thoothukudi and Nagapattinam. The physicochemical parameters were of plants such as carbon (C), hydrogen (H), nitrogen (N) and sulfur (S) were analyzed using Carbon Hydrogen Nitrogen and Sulfur (CHNS) elemental analyzer. Sediments of both plants were also collected for analysis soil properties such as pH, bulk density (BD), sediment organic matter (SOM), microbial loads, sediment organic carbon (SOC), and interstitial water salinity and identify the presence of functional groups in the sediments. The carbon concentration in the root, stem and leaves of A. marina and S. brachiata were analyzed for different seasons and compared for both the locations. During observation, the mean value of C was 35.786% in A. marina with the maximum value of 44.726% found in leaves during the pre-monsoon season (February) at Nagapattinam and the minimum value of 26.957% in root during the month of November in post-monsoon season at Thoothukudi. The mean C value of S. brachiata was 29.786% with the maximum value of 51.408% found in leaves during post-monsoon in the month of December at Nagapattinam and the minimum value of 17.938% in leaves during pre-monsoon in the month of February at Nagapattinam. The concentration of carbon were significantly differ between the stations (p˂0.05) but not between the seasons (p˃0.05). The average concentration of hydrogen, nitrogen and sulfur were 5.406%, 3.974% and 0.292% in A. marina and 4.776%, 3.128% and 0.409% in S. brachiata respectively. There was no significant difference between the seasons and stations (p˃0.05). The physicochemical parameters such as pH, bulk density (BD), sediment organic matter (SOM), and sediment organic carbon (SOC), microbial loads were also analyzed. The pH of both the plant sediments were found in the range of 6-6.9 which is slightly acidic in nature and bulk density were ranged from 3.161 g cm-3 to 13.624 g cm-3 in A. marina and 1.976 g cm-3 to 9.565 g cm-3 in S. brachiata. The BD was found more on the top surface 0-10 cm depth than the 10-20 cm and A. marina sediment content more BD than S. brachiata sediments which could be due to accumulation of sediment and plant litters from tidal exchange. The mean value of SOM and SOC were 3.99% and 2.492% in both A. marina and S. brachiata respectively. The relationship of SOM and SOC showed that with the increased value of SOM, SOC also increased which is already 50% of organic matter. Microbial loads found in S. brachiata sediments was 9.65 x 104 which was more than the 7.75 x 104 of A. marina sediment. Micro-organisms fed on plant tissue and transfer the carbon to fine root and sediments. In the present study, the salinity found in the interstitial water was range from 20 to 22 ppt in A. marina sediments and 12 to 14 ppt in S. brachiata sediments. The salinity served as nutrient to plant which helps in plant growth and reproduction. Slight changes in salinity could affects the plant mechanism. The main functional groups identified in the sediments of A. marina and S. brachiata were O-H group of alcohols and phenols, N-H groups of amines and amides and aliphatic CH3 and CH2. The O-H groups of alcohols and phenols (3630-3600 cm-1) and aliphatic CH3 and CH2 (2930-2810 cm-1) were observed in all depths of samples except in A. marina depth (0-10 cm). Other Functional groups were detected around 1650-1620 cm-1, 1500-1400 cm-1, 1060-1000 cm-1 with the N-H bending vibration (amide II band), C-C ringing stretch with the aromatic ring, C-H bending vibration in alkenes and C-O stretching vibration (esters, ethers or carboxylic acids). C-N stretching in amines, respectively.EnglishThesis