Abstract. Ramdhun D, Appadoo C. 2020. A contribution to understanding blue carbon sequestration and forest structure in mangroves of different ages in a small island (Mauritius). Ocean Life 4: 74-81. Mangrove biomes, a blue carbon coastal ecosystem, are considered as the most carbon-rich forest in the tropics, but there is a knowledge gap on their ecosystem services especially in small islands. The purpose of this study was to evaluate the carbon stock in sediment and aboveground biomass of three different ages of Rhizophora mucronata forests along the coastline of Mauritius. Forest structure was assessed, and measurements of diameter at breast height were used to calculate biomass using allometric equation. Corer samples were collected in each site and sectioned into subsamples of 0-10 cm, 10-20 cm and 20-30 cm, to analyze soil bulk density and soil organic carbon. The highest SOC stock (470.08 t haˉ¹) was recorded at Mahebourg and lowest (331.33 t haˉ¹) in the young stand at Le Morne. The total organic carbon contents varied from 931.50±17.06 t haˉ¹ (at Mahebourg) to 350.76±4.058 t haˉ¹ (young forest at Le Morne). There was no significant difference in soil carbon density at different soil depths studied at Le Morne (n=81, p=0.430 (old forest), p=0.875 (young forest)), however, a different scenario was observed at Mahebourg (n=81, p=0.027). This study is the first to report on the potential of carbon storage at these sites in Mauritius and add to the knowledge of the ecosystem services of this ecosystem.