<![CDATA[Background: Indonesia, as a maritime nation with 40% of global maritime trade passing through its waters, faces high risks of marine oil pollution. Balikpapan Bay, located in East Kalimantan, has suffered recurring oil spill disasters, notably the large-scale spill in 2018 caused by a ruptured Pertamina pipeline. These spills have severely impacted the marine ecosystem, local biodiversity, and the socio-economic conditions of coastal communities. Methods: This study employed a qualitative descriptive approach through case study analysis. Primary data were collected from government documents, field reports, and previous academic studies, particularly focusing on ecological damage assessments conducted by the Ministry of Environment and Forestry, NGOs, and local communities. Spatial data from satellite monitoring were used to assess the extent of the oil spill. The data analysis included categorization of ecological impacts on key ecosystems such as mangroves, coral reefs, seagrasses, marine fauna, and bird species. Findings: The oil spill in Balikpapan Bay contaminated nearly 13,000 hectares of marine waters and 60 km of coastline, causing substantial damage to 34 hectares of mangrove forest, 4 coral reef areas, 5 seagrass beds, and seaweed cultivation zones. It led to mass deaths of crabs, plankton, and endangered marine mammals. Bird populations were also severely affected due to loss of insulation and ingestion of toxic substances. The spill had a cascading effect on the local marine food web, reduced biodiversity, and caused economic losses for traditional fishing communities. Conclusion: The Balikpapan Bay oil spill has led to a multidimensional ecological crisis. This study underscores the urgent need for proactive oil spill prevention and ecosystem protection strategies. Conservation zoning, enforcement of environmental regulations, and community-based monitoring are essential to prevent future disasters. Novelty/Originality of this article: This study presents a comprehensive ecological assessment of the Balikpapan Bay oil spill by combining field data, satellite imagery, and governmental reports. It adopts an integrative approach to map ecological damages and propose policy recommendations grounded in ecological science and conservation planning.]]>
