Ecosystem Carbon Stock and Stable Isotopic Signatures of Soil Organic Carbon Sources Across the Mangrove Ecosystems of Kerala, Southern India

Mangrove ecosystems have high carbon storage and sequestration rates and become substantial sources of greenhouse gases when disturbed by land-use change. Thus, they are extremely valuable for inclusion in climate change mitigation and adaptation strategies. However in Kerala, a west coast state of India, has lost 95% of its mangroves in the last three decades, posing a serious threat to global climate. The regional carbon stock data of mangroves that are at risk of depletion are rarely reported, despite the fact that they are crucial for mitigating and managing climate change impacts. In response, the study estimated the ecosystem carbon stocks and soil organic carbon sources of three different estuarine mangrove habitats of Kerala. The mean total ecosystem carbon stock of Kerala mangroves was estimated to be 218.98 ± 169.86 Mg C ha− 1 which is equivalent to 803.66 ± 621.47 Mg CO2 ha− 1, contributing a substantial amount of carbon to the global ecosystem carbon. Further 88% of the estimated ecosystem carbon stock was represented by vegetation biomass and 22% by the soil carbon stock. The stable isotopic signatures revealed that the accumulated autochthonous mangrove source attributed to the organic carbon in the soils of site 1 (Munroe island) and site 3 (Vypin) while the suspended organic matter in tidal water contributed to the soil organic carbon of site 2 (Ayiramthengu) mangroves. Mangrove structure, salinity, soil pH and bulk density were found to be the correlating factors for the carbon stock variations across the study sites. Hence, the understanding of the amount of carbon stocks in the mangroves of Kerala coupled with other ecosystem services they offer highlights their importance in the creation of conservation, restoration and climate change mitigation plans in the country.