Persistence and Dynamics of Shallow Water Benthic Habitats by Multi-Temporal Sentinel-2 Observations in Mapur Island Indonesia

Shallow-water benthic habitats are important to tropical coastal ecosystems, yet spatial transitions and persistence in Indonesia’s small islands remain insufficiently documented. This study mapped benthic habitats around Mapur Island, Riau Islands, Indonesia, and assessed changes between 2020 and 2025. Results: Sentinel-2 imagery was classified using Random Forest in Google Earth Engine, supported by field observations collected in July 2025 using 1 × 1 m photo-transects. Four classes were mapped: dead coral with algae, mixed substrate, sand, and seagrass. The 2025 classification achieved 76.9% overall accuracy and a Kappa coefficient of 0.69. Between 2020 and 2025, sand increased by 75.43 ha (11.5%) and dead coral with algae increased by 68.01 ha (10.5%), while seagrass declined by 41.8%, from 308.97 ha to 179.76 ha. Approximately 24% of the initial seagrass area persisted over the study period. Conclusions: The results indicate substantial changes in the composition of shallow-water benthic habitats around Mapur Island, with seagrass showing the largest net decline. The maps provide a temporal baseline for coastal habitat monitoring and conservation planning, while the transferred classification for 2020 should be interpreted in light of the lack of independent field validation for that year.