Environmental drivers of seagrass biomass and carbon stocks in a threatened Indonesian ecosystem

Seagrass meadows play a critical role in coastal blue carbon sequestration, yet they are increasingly threatened by anthropogenic activities, especially in tourism-intensive islands. This study aimed to estimate seagrass biomass, carbon stocks, and assess the influence of environmental parameters on these ecological indicators in Tabuhan Island, Banyuwangi, East Java. Field research was conducted during August-September 2023 at two stations (North and East). Data collection involved 50 × 50 cm quadrat transects for seagrass sampling, in situ measurements of environmental parameters (temperature, salinity, pH, dissolved oxygen, brightness, current velocity, and substrate type), and laboratory analysis of biomass and organic carbon content using the Loss-on-Ignition method. Four seagrass species were identified: Cymodocea rotundata, Halophila ovalis, Enhalus acoroides, and Thalassia hemprichii. The seagrass ecosystem was in poor condition, with very low coverage (0.46% and 0.45%) and density (< 0.02 shoots m-2). The average total biomass was 0.017 g DW m-2, with below-ground biomass dominating. The estimated carbon stock was 0.0035 g C m-2, stored primarily in below-ground tissues. Multivariate analysis revealed patterns among measured variables, with salinity and current velocity loading on one principal component and pH, biomass, and carbon stocks loading on another. This study underscores the urgent need for integrated coastal management and conservation strategies to protect and restore these vulnerable ecosystems, particularly in developing tourist destinations, to maintain their Nature’s Contributions to People (NCP), including climate change mitigation.