Aboveground biomass growth mapping and CO2 uptake of multispecies seagrass meadow in Menjangan Besar Island, Karimunjawa Islands, using Sentinel-2 imagery

Seagrasses absorb CO₂ for photosynthesis and convert it into new biomass. This study aims to assess the correlation between seagrass aboveground biomass (AGB) growth and percent cover, map and analyse AGB growth using Sentinel-2 imagery and estimate CO₂ uptake by multispecies seagrass meadows on Menjangan Besar Island. Correlation analysis revealed a strong relationship between AGB growth and percent cover at the community level (r = 0.64) and for Enhalus acoroides (r = 0.60), and a very strong relationship for Thalassia hemprichii–Cymodocea rotundata assemblages (r = 0.89). AGB growth mapping was conducted using random forest (RF) regression, resulting in root mean square errors (RMSE) of 60.8, 125.6, 94.2 and 94.9 gDW · m⁻² · year⁻¹ for E. acoroides, T. hemprichii–C. rotundata, E. acoroides–T. hemprichii, and bare substrate (BS) classes, respectively. The corresponding coefficients of determination (R²) were 0.87, 0.67, 0.70, and 0.78. The total seagrass AGB growth on Menjangan Besar Island was estimated at 672.21 MgDW · year⁻¹, with an average of 331.7 gDW · m⁻² · year⁻¹ The estimated total CO₂ uptake by seagrass meadows was 197.85 MgCO₂ · year⁻¹, with an average of 97.6 gCO₂ · m⁻² · year⁻¹.