Seagrass ecosystem adjacent to mangroves store higher amount of organic carbon of Andaman and Nicobar Islands, Andaman Sea

This study quantified the organic carbon (Corg) stocks in Thalassia hemprichii meadows that are (i) adjacent to mangroves (MG), and (ii) without mangroves (WMG), in tropical Andaman and Nicobar Islands (ANI) of India. In the top 10 cm of the sediment, Corg content was 1.8-fold higher at the MG sites than the WMG sites. The total Corg stocks (sediment + biomass) in the 144 ha of seagrass meadows at MG sites (988.74 ± 138.77 Mg C) was 1.9-fold higher than in 148 ha of WMG sites. Protection and management of T. hemprichii meadows of ANI can lead to emission avoidance of around 5447.33 (MG; 3595.12 + WMG: 1852.21) tons of CO2. The social cost of the carbon stocks in these T. hemprichii meadows is around US$ 0.30 and 0.16 million at the MG and WMG sites, respectively, showcasing the importance of ANI's seagrass ecosystems as nature-based solutions for climate change mitigation. •Thalassia hemprichii meadows adjacent to mangroves had higher carbon stocks.•External nutrient input is higher in T. hemprichii meadows adjacent to mangroves.•T. hemprichii biomass increased 2-fold when present adjacent to mangroves.•T. hemprichii meadows adjacent to mangroves have 1.9-fold higher carbon stocks.•Andaman seagrass ecosystems have potential to mitigate climate change.