A new method of coral reef restoration holds promise for being less labour-intensive and time-consuming.
Current reef restoration methods are extremely labour-intensive, as every coral fragment or 'recruit' needs to be attached to the degraded reef individually.
As a result, restoration efforts usually cover less than a hectare. This is in stark contrast to reef degradation, which occurs at a scale of hundreds and thousands of square kilometres.
Enter coral sowing, a new method of reef restoration that can vastly speed up the recovery process.
The scientists from SECORE, an international non-profit organisation that focuses on coral reef conservation, collected coral larvae released by colonies of golf ball corals on Curaçao and, shortly after, settled them on substrates made of cement. These tetrapod-shaped substrates are specially designed, so as to promote attachment to reefs and to enhance the coral larvae's survival.
After three weeks, the coral larvae had grown into polyps. These “Seeding Units” (as they were now called) were then sown onto the reef in front of the Curaçao Sea Aquarium.
“The specific shape of the tetrapod substrates allowed us to simply wedge the Seeding Units into natural crevices of the reef. Most Seeding Units were stable within few weeks, either secured in crevices or naturally cemented on the reef's framework," said Valérie Chamberland, who led the research for the Curaçao study.
For a year, the Seeding Units were closely monitored. "We settled between 20-30 larvae on each substrate to ideally have one coral established per Seeding Unit in the long term. After one year more than half of the units were recovered and still harboured at least one coral, meeting this target required to eventually yield a successful restoration outcome," said Chamberland.
Now, the next step is to test the method on a larger scale. To do this, SECORE will work with the California Academy of Sciences, The Nature Conservancy, and other partners to overcome the logistical and engineering challenges of processing 50,000 to 100,000 substrates within a single location and spawning season.
At the same time, the scientists will strive to optimise the design of the substrate and Seeding Units to improve coral settler survival and growth.