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

Department of Marine Science and Technology, IPB University, Bogor 16680, Indonesia

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Abstract

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.