Assessing coral reef conservation planning in Wakatobi National Park (Indonesia) from larval connectivity networks

Wakatobi National Park (WNP), located in the heart of the Coral Triangle in Indonesia, is one of the most biodiverse marine habitats on Earth. Coral ecosystems within the park, however, are threatened by anthropogenic stressors such as coral diseases, coral mining, blast fishing, invasive species and pollution. This led the Government of Indonesia to establish marine protected zones (MPZs) over 2% of the WNP, but the efficiency of these MPZs to support coral reef resilience against anthropogenic disturbances remains poorly documented. Here this gap was filled by evaluating coral connectivity within the WNP at the sub-reef scale and assessing how the MPZs contribute to coral resilience on other reefs within the WNP. The larval dispersal of the coral species Acropora millepora and Acropora gemmifera were simulated during eight spawning seasons in 2014-2021 using a multi-scale ocean model that achieves a local resolution finer than 100 m. The coral connectivity matrices were then analysed using Google's PageRank algorithm to identify the sub-reefs that act as major sources and sinks, as well as sub-reefs best suited for protection and restoration planning. The interannual and interspecific variability of these indicators were assessed and identified sub-reefs that were consistently ranked high for all eight years and for both species. Both El Nino and La Nina events were found leading to a significant increase in larval exchanges across the WNP for both species. Overall, the results suggest that, under the current WNP zoning, there is limited overlap between MPZs and the reefs identified as best candidates for reef protection and restoration based on acroporid larval connectivity. The current restoration site of Ou Tooge was unlikely found to be a significant larval supplier to adjacent reefs in the WNP. Based on the high-resolution coral connectivity analysis, a list of reefs that were proposed should be prioritised for maximising the broad-scale impact of coral reef conservation and restoration planning in the WNP.

Automated summary

Wakatobi National Park is one of the most biodiverse marine habitats on Earth, but the coral ecosystems within the park are threatened by various anthropogenic stressors. This study evaluated coral connectivity and the contribution of marine protected zones (MPZs) to coral resilience within the park. The results showed limited overlap between MPZs and the reefs identified as best candidates for protection and restoration, suggesting the need for prioritization in coral reef conservation and restoration planning in the park.