Sediment Carbon Storage of Two Main Wetlands in Pondicherry, India

Assessing the carbon storage patterns in the sediments of Oussudu and Kaliveli, considered as potential wetlands for conservation under RAMSAR convention and declared bird sanctuaries by the government was the objective of the study. Dissolved oxygen and CO2 diffusion rates in the 'surface waters' was analyzed and the relationship between the sediment carbon storage and oxygen/carbon dioxide in the waters was presented. The mean dissolved oxygen content for the study period (2009 - 2011) was 17.28 ± 3.25 mg/l for Oussudu and 35.5 ± 7.23 mg/l for Kaliveli respectively. The rate of CO2 diffusion was high (13.31±2.71 mg/l) in Kaliveli than in Oussudu (6.48±1.21 mg/l). High level of CO2 diffusion causes acidification forming carbonic acids which might be the cause of high levels of sediment calcium in Kaliveli. The mean calcium carbonate and organic matter content of sediment was 2.11±0.51% and 1.51±0.59% for Oussudu and 36.21±4.51% and 0.46±0.16% for Kaliveli respectively. The total organic carbon and phosphate content were 0.87±0.34% and 27.38±0.56 (mg/L) for Oussudu and 0.27±0.09% and 4.13±0.67 (mg/L) for Kaliveli respectively. There existed a significant inversely proportional relationship between calcium carbonate and organic matter and a strong positive relationship between organic matter and phosphate in the sediments. Our study reveals that majority of the carbon storage is through organic matter in Oussudu lake and through calcium carbonate in Kaliveli.