The project aims to restore damaged reef coral communities in the Northern Luzon region of the Philippines using mass coral larval reseeding and to evaluate the socio-economic effects of reef restoration strategies.
Coral reef restoration is a major priority for reef management. ‘Recoverable’ coral reefs that are damaged and degraded but not chronically polluted occur in the Philippines and Australia.
This project builds on the successful ACIAR SRA FIS/2011/031 project, which began coral recovery on degraded reefs in the Philippines. It will expand reef restoration trials, and evaluate the socio-economic effects of reef restoration.
Reef restoration to improve the health status of reseeded reefs will benefit humans and natural communities. Reef restoration will improve reef productivity and food security, access to increased reef resources and potential for local coral mariculture to improve incomes, and water quality, coastal protection and other ecosystem services. As the coral and reef communities develop, the values and benefits of reef restoration for local households and communities will increase beyond the life of this project up to the estimated average coral reef value of about US$350,000/ha/year. Reseeded corals will reproduce sexually after 1-4 years and help reef recovery, thereby promoting local reef resilience.
Substantial progress has been achieved during the first year of this project, which aims to restore damaged coral reefs in the Philippines using innovative mass coral larval settlement.
Detailed information has been obtained on major coral spawning periods in the Bolinao-Anda reef region in northern Luzon, Philippines, enabling access to many millions of spawned gametes for mass larval rearing and reef restoration. Large multispecific coral spawning events were recorded on reef areas during February and March 2016 with additional coral spawning in April 2016. Millions of spawned coral gametes were collected and embryos initially reared in situ in a large floating mesh enclosure on the reef, with millions more larvae reared in the Bolinao Marine Laboratory (BML).
Monitoring of longer-term outcomes from the larval restoration pilot study initiated in 2013 using 1.6 million Acropora tenuis larvae showed extraordinarily high ongoing survival of juvenile corals at the degraded Magsaysay Reef sites. There was 100% survival of coral colonies from age two to three years that had developed from larvae that had settled on reef areas, and similar high survivorship of colonies from larvae that had settled on coral skeleton recruitment tiles. The average number of surviving A. tenuis recruits on the natural reef substrata in each settlement site after three years was 24 colonies, which equates to 3.4 new colonies developing from larvae on each m2 of available reef substrata. The average number of surviving recruits on the 10x10 cm coral skeleton tiles in each settlement site after three years was 3, which equates to 13.4 recruits per m2 of available tile surface. After three years growth colony size ranged up to 33 cm mean diameter, and the majority of colonies were larger than 12.5 cm mean diameter and were sexually reproductive and spawned after the April 2016 full moon. This outcome is globally significant as it is the first time that a breeding population of Acropora reef corals has been re-established on a degraded reef system using mass larval enhancement and with the lifecycle closed within three years.
Larval restoration experiments were scaled up during 2016 using 4.6 million A. tenuis larvae; 1.6 million larvae reared from spawned gametes from the three-year old larval recruit colonies, plus 3 million larvae reared from spawn of other colonies from nearby reefs. Over 1.5 million larvae were added to each of three 5x5 m fine-mesh larval enclosures, with massive settlement rates recorded on coral tiles after the five-day settlement period (average 210 juveniles/tile). Subsequent monitoring showed the expected initial high mortality of juvenile corals with 46.5% survival after 1 month, but the overall rate of recruitment is substantially higher than for the 2013 pilot study, indicating that many hundreds of new colonies are likely to be recorded on the degraded reef sites in coming months. These results confirm that mass larval restoration is a viable and effective active reef restoration option for significantly increasing coral population recovery and initiating reef restoration even on degraded reef systems.
Innovative settlement tile experiments were completed to design larval settlement surfaces that can be used to enhance coral recruitment. Use of 3D printing to experimentally manipulate surface microtopography of plastic 3D printed settlement tiles showed that Montastrea colemani brain coral larval settlement can be significantly increased when cryptic microhabitats are provided, and larval settlement was highest in small 1 mm holes. Monitoring of Acropora gemmifera coral recruits nine months after settlement showed highest growth and survival rates on two types of 3D printed plastic tiles compared with natural coral skeleton tiles, and higher recruitment on tiles conditioned in the BML seawater system compared to tiles initially conditioned on the reef. These results show that the two commonly used 3D printing plastics are not toxic to corals and that 3D printing technology can be used to produce complex settlement surfaces that enhance larval settlement and recruitment rates for reef restoration.
The project has also provided substantial capacity building for PhD students, Research Assistants converting to Masters research, an Honours student, and many staff at BML and research volunteers. The research partner and a Masters student from the University of the Philippines have been confirmed for the socio-economics components to evaluate the socio-economic impacts of alternative reef restoration strategies. Community engagement included meetings with local Municipality representatives who were very supportive of the project and reef restoration plans, and media releases and articles highlighting the project outcomes. Key research outcomes have also been presented at international conferences and publications are being prepared.