Ecological Vulnerability of Coral Reef Ecosystem in Wakatobi National Park During Indian Ocean Dipole Event Hawis H. Madduppa 1, 3* , Alan F. Koropitan 1 , Ario Damar 2, 3 , Beginer Subhan 1 , Muhammad Taufik 4 , La Ode Alam Minsaris 2 , AM Azbas Taurusman 3, 5 , Agus Ramli 3 , Arif Budi Purwanto 3† 1 Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, Bogor Agricultural University (IPB University), Bogor, Indonesia 2 Department of Aquatic Resources Management, Faculty of Fisheries and Marine Science, Bogor Agricultural University (IPB University), Bogor, Indonesia 3 Center for Coastal and Marine Resources Studies, Bogor Agricultural University (IPB University), Bogor, Indonesia 4 Thematic Mapping and Integration Center, Geospatial Information Agency, Bogor, Indonesia 5 Department Fisheries Resources Utilization, Faculty of Fisheries and Marine Science, Bogor Agricultural University (IPB University), Bogor, Indonesia 1. Introduction Coral reefs form a complex habitat, and it provides important environmental services such as food, shelter and coastal protection (Cesar 2002). Disturbances on coral reefs habitat can result in several impacts on coral reef ecosystems and dependent communities, for example, coral bleaching and mortality from increasing sea temperatures can alter the goods and services created by coral reefs, such as the productivity of coral reef fisheries (Graham et al. 2007). The impact of increasing temperature is affecting many species, when there has been a lot of coral bleaching events (Berumen and Pratchett 2006) and the coral invasion diseases such as sponges (Madduppa et al. 2015). Glynn (1993) indicates that 70% of coral bleaching reports associated with the report that waters become warmer than normal conditions. In addition to coral bleaching, the increase in sea surface temperatures also makes coral reefs susceptible to disease. The important existence of coral reefs is threatened by two common factors, human (high and destructive fishing, pollution) and nature (sedimentation and climate change) (McClanahan 2002; Hughes et al. 2003). The exact potential impacts of these threats are still unclear in many cases, making effective conservation difficult. Climate change as the major issue becomes fully evident in 1997-1998 when elevated sea surface temperature (SST) was linked to global warming and a strong El Nino which caused widespread coral bleaching and mortality ABSTRACT This research examines coral reefs vulnerability which threatening its existences and functions by climate change. The ecological vulnerability in Wakatobi (Wangi- wangi, Kaledupa, Tomia, and Binongko) was assessed during Indian Ocean Dipole (IOD) event in 2016. Climate exposure was determined using sea surface temperature, chlorophyll-a concentration, and wind speed magnitude; sensitivity was determined using coral susceptibility, fsh susceptibility, and macroalgae primary productivity rate; then adaptive capacity was developed by hard coral cover, coral size distribution, coral richness, fsh biomass, herbivore diversity, and herbivore grazing relative to algal production. The values of Exposure, Sensitivity, and Adaptive capacity in Wakatobi were 0.93±0.02, 0.42±0.18, and 0.44±0.10, respectively. Site specifc vulnerability scores ranged from 0.52 to 1.60 (mean 0.92±0.26). Binongko was the least vulnerable than other islands. Tomia was observed as the least adaptive capacity and Wangi-wangi was the most bleaching incidents. These results could help coral reefs monitoring priority during the event and then when the event is gone by focusing on the marked islands and sites. Sites that were observed as more vulnerable is urgently need a management strategy to overcome the vulnerability status in the future, such as increasing site adaptability. ARTICLE INFO Article history: Received October 13, 2017 Received in revised form September 10, 2019 Accepted September 12, 2019 KEYWORDS: Adaptive capacity, ecological vulnerability, IOD event, coral triangle, coral bleaching * Corresponding Author E-mail Address: hawis@apps.ipb.ac.id Copyright ©2020 Institut Pertanian Bogor Vol. 27 No. 1, January 2020 57-70 DOI:10.4308/hjb.27.1.57 ISSN: 1978-3019 EISSN: 2086-4094 H A Y AT I Journal of Biosciences