Title
A Study of the 2010 Coral Bleaching Event on Coral Communities in Wakatobi National Park
Author(s)
Joanne R. Wilson; Rizya L. Ardiwijaya; Rian Prasetia
Published
2012
Abstract
Wakatobi archipelago is located on the south east tip of Sulawesi Island, central Indonesia in the heart of the Coral Triangle. Wakatobi is an acronym for the four major islands of Wangi-Wangi, Kaledupa, Tomia and Binongko although this region contains a total of 39 islands and several large atolls. In 1996, the government of Indonesia declared Wakatobi National Park (Wakatobi NP) protecting 1.39 million hectares of the islands and surrounding waters. Wakatobi NP encompasses a diverse range of marine habitats. The main islands are surrounded by fringing coral reefs. Parallel to the archipelago of main islands are three large atoll reefs. A number of smaller reefs are located in open waters in the southeastern part of Wakatobi. Wakatobi NP is also surrounded by major sea straits that function as migratory corridors for large marine species such as sea turtles and whales – many of which are listed as endangered.
The main threats to Wakatobi NP are over-fishing and over-exploitation of coral reef resources. However, elevated sea temperatures associated with La Nina/ El Nino climatic events which cause coral bleaching are emerging as an important threat. Coral bleaching was observed at all survey sites during annual reef health surveys in April 2010. Quantitative surveys of bleaching incidence could only be done at 8 sites in April 2010 but were followed by post-bleaching and resilience surveys in September 2010 and January 2011 at 24 sites.
On average, 65% of corals were affected by the bleaching but mortality was estimated at less than 5%. The most bleaching susceptible genera were found to be Pocillopora, Stylophora, Montipora plates and tabular and branching Acropora. Karang Otiolo, at the southern end of the park suffered the highest coral bleaching during April 2010 with 70% affected at deeper reef. Corals at Table Coral City which is dominated by bleaching susceptible Acropora species were still bleached in September 2010 with 35% of colonies recorded as pale.
There are many factors which indicate this bleaching event was caused by elevated seawater temperatures and/or high light intensity including:
the extensive nature of the bleaching throughout the National Park
elevated sea surface temperatures from February to May 2010
the fact that many of the fully bleached corals were still alive and recovered after temperatures dropped.
Therefore, it is important to develop a bleaching response plan for WNP. This should include using web-based products which show regional temperature stress, preparing a team capable of conducting bleaching surveys and reporting bleaching condition, building and strengthening stakeholder network in order to share bleaching information, and most importantly to identify management actions to ensure the health of reefs so they have the best chance of surviving climate change impacts.
Full Citation
Wilson, J.R., R.L. Ardiwijaya, and R. Prasetia. 2012. A Study of the Impact of the 2010 Coral Bleaching Event on Coral Communities in Wakatobi National Park. The Nature Conservancy, Indo-Pacific Division, Indonesia. Report No. 7/12. 25 pp.
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