Coral reef larva reseeding for reef reforestation
By Dr. Rafael D. Guerrero III
The Great Barrier Reef (GBR) of Australia is the world’s coral reef system with an area of 344,000 square kilometers. Throughout the world, coral reefs provide coastal protection, food, medicine and tourism for millions of people. With the adverse impacts of climate change, more than 50% of the GBR has been damaged due to the rise in water temperature and acidity, according to a report.
Marine scientists of the Southern Cross University in Lismore, Australia led by Dr. Peter Harrison have developed a relatively simple but effective technology for repopulating damaged areas of the GBR.
With initial trials conducted in the Philippines in 2013 by PhD candidate Dexter dela Cruz under the supervision of Dr. Harrison, the eggs and sperms of the stony coral Acropora sp. spawned during the breeding season (March to May) in the wild were gathered and fertilized in the laboratory.
After a week of rearing, the coral larvae known as planulae are released in damaged coral reef areas where they attach to suitable substrates like rocks, become polyps that produce their calcareous skeleton (calcium carbonate), mature and multiply into colonies that form reefs. The stony coral subsists on the food produced by dinoflagellates (zooxanthellae) that are symbiotic with them.
In 2015, the technology was further improved by Dr. Harrison in the GBR. Instead of reseeding lab-reared coral larvae for reef restoration, the larvae were reared in floating pools in the GBR. He found that it takes 15,000 to 20,000 coral larvae to produce a mature coral in five years in Australia. The technology showed that the release of billions of coral larvae in damaged coral areas was effective for reef restoration.
In 2016-2020, a project on Restoring Damaged Coral Reefs Using Mass Coral Larval Reseeding funded by the Australian International Center for Agricultural Research (ACIAR) was implemented in the Philippines by Drs. Peter Harrison and Dexter dela Cruz at the Bolinao-Anda Reef Complex in Pangasinan.
Seven trials in two municipalities were conducted and multiple new breeding populations of the stony coral were established, according to the final report in 2023. It was found that the corals from the reseeded larvae matured in only two years. There was also an increase in the abundance of fish in the reseeded areas indicating a positive contribution to the socioeconomic development of fisherfolk.
Trainings for the transfer of technology to stakeholders of the BARC, including local communities, the private sector and local government units, have been conducted by the project. A follow-up project to bring the technology to other parts of the country is now in the offing.
Photo courtesy of Great Barrier Reef Foundation