Quantifying the Role of Aquatic Ecosystems in Carbon Sequestration and Climate Regulation

Abstract

Aquatic ecosystems are major reservoirs in global carbon cycles, and their potential as climate change mitigation instruments is seriously compromised by substantial data uncertainty and a severe lack of site-specific measurements. This study attempts to fill some of this gap by assessing carbon sequestration in the Pichavaram mangrove ecosystem. By using intensive sediment core sampling coupled with vegetative biomass surveys at 12 permanently marked stations for a 24-month period, it estimates carbon burial flux in the mangroves. Based on geochronology measurements using both^210Pb and ^137Cs, it determined the carbon sequestration rate at 1.85 ± 0.42 Mg C ha⁻¹ yr⁻¹. Results confirm that the efficiency of carbon sequestration is positively related to vegetation density, and high nutrient inputs and water velocities serve as limiting factors that might initiate a threshold response where burial flux decreases non-linearly. This study establishes coastal mangroves as significant long-term carbon storage systems and supplies the first empirical data required to increase the accuracy of carbon budgets at regional scales. It underscores the ability of these ecosystems to be significant nature-based climate mitigation solutions, but confirms that their effectiveness as CO₂ mitigation agents is very susceptible to human perturbation and habitat degradation, making integrated coastal management that emphasizes protection of high-density vegetation areas and prevention of high nutrient runoff necessary to conserve their blue carbon stock. The data should provide an important baseline for policy makers in accounting site-specific potential of aquatic sequestration in the context of national climate mitigation schemes and in maintaining long term sustainability of ecosystem services in a world of changing sea levels.