CORAL REEF RESTORATION IN SINGAPORE - PAST, PRESENT AND FUTURE

Abstract

The decline of coral reefs has necessitated the implementation of management strategies such as reef restoration to maintain and enhance the resiliency of these ecosystems. As Singapore’s reefs have been impacted by chronic sedimentation and unstable substrate since the 1960s, it is critical that effective strategies be applied to assist in their recovery. This dissertation aimed to assess the reef restoration strategies used and evaluate their contribution to coral reef conservation in Singapore. I first reviewed the restoration techniques employed since the 1990s, and classified them as four main thrusts: 1) substrate modification to enhance coral settlement and survivorship, 2) artificial reef deployment, 3) coral nursery establishment, and 4) coral transplantation. These efforts had varied successes and only spanned short terms (< 4 years). Detailed information on their outcomes over long terms would benefit the management and conservation of Singapore’s reefs. The effectiveness of Reef Enhancement Units (REUs) and coral transplants was thus examined in the current study. The REUs are modular fibreglass artificial reefs that were deployed at St John’s, Kusu, Sisters’, Lazarus and Satumu. Monitoring had ceased in 2004. Field surveys in 2014 revealed that the REUs functioned as a habitat and food source for at least 106 sessile and mobile reef taxa, including hard corals, soft corals, fishes and crustaceans. The REUs in 2004 were less diverse, and were dominated by turf and coralline algae. The sessile communities were also dissimilar among sites in 2014, with those in Satumu (>40% hard corals) and Lazarus (>70% turf algae) being the most dissimilar. Scleractinian communities were fairly homogeneous among sites, with 29 genera (12 families) recorded from all REUs. Gravid colonies were also documented at three plots before the 2014 mass coral spawning event. It was apparent that the REUs complemented Singapore’s habitat rehabilitation efforts in the long term by augmenting reef diversity and restoring ecosystem services. Three types of coral material were transplanted on reefs and seawalls at Singapore’s offshore islands since 2007. This comprised coral nubbins transplanted at Semakau and Hantu (2007), coral fragments at Tekong and St John’s (2010), and juvenile corals at Kusu (2013). While the results varied in 2014, transplants with massive or submassive growthforms (e.g. Porites, Psammocora, Diploastrea, Goniastrea) generally had better survivorship and growth than those with branching growthforms (e.g. Acropora, Pocillopora, Hydnophora). Transplants attached securely to the substrate also fared better, as did those sited in areas with less environmental disturbances. The results demonstrated the feasibility of transplantation as an approach for increasing hard coral cover in Singapore over time. In light of further reef loss predicted in the coming decades, my findings underscored the importance of enhancing current restoration strategies to achieve the best outcomes for Singapore’s reefs. I recommend implementing long-term monitoring regimes, incorporating novel techniques, mitigating climate change effects, engaging and educating stakeholders, and re-assessing the legal protection of corals. The cooperation and commitment of all stakeholders (policy makers, scientists, civil society) is critical to ensure that the future of Singapore’s reefs is not a blighted one.