Mapping of shallow marine habitats using Sentinel-2A satellite imagery with OBIA method in Tanjung Kelayang coastal area, Belitung Island

Tanjung Kelayang is vulnerable to ecosystem change driven by human activities and environmental factors. This study aimed to map and analyze changes in benthic habitats using Sentinel-2A imagery from 2019 and 2024 by applying an Object-Based Image Analysis (OBIA) approach combined with a Support Vector Machine (SVM) classifier. The analysis included water column correction using the depth-invariant index (DII), multiresolution segmentation, habitat classification, accuracy assessment, and post-classification change detection. Six benthic habitat classes were identified, namely coral, seagrass, macroalgae, sand, rocks, and coral rubble. The results show a decrease in coral cover of 87.99 ha (19.96%) and a substantial increase in coral rubble of 80.33 ha (87.77%), indicating reef degradation. The classification achieved an Overall Accuracy of 70.97% with a kappa coefficient of 0.61, reflecting a good classification performance. These findings demonstrate that Sentinel-2A imagery combined with the OBIA method is effective for monitoring changes in shallow marine habitats, and supports spatial-based coastal zone management.