The implementation of coral nurseries is a highly prevalent method of coral restoration in the Philippines. These nurseries primarily focus on fast-growing branching corals and do not typically include massive corals. This is due to the slow growth rate and morphology of these corals. , which are not conducive to traditional coral nursery methods. Microfragmentation is a relatively new technique that has displayed positive results for massive coral propagation. This method utilizes small fragments of corals (≈1-3cm), which are mounted on discs and placed in nurseries. Once the fragments reach appropriate size, the fragments of a single coral (i.e., genotype) are transplanted to a restoration site and placed in groups 2-4cm apart. Over time the fragments fuse into larger corals. This enables the corals to share resources and reach size of sexual maturity sooner in comparison to traditional nursery methods. Though microfragmentation is becoming more practiced, there is no scientific literature specifically focused on this method in the Philippines. This study aimed to determine if: 1) genotype significantly influences growth, 2) the individual fragment of each genotype accounts for differences in growth, and 3) this method is viable in a fisherfolk community with minimal technology in the Western Visayas of the Philippines.
A total of five coral heads (genotypes) of the lobe coral Porites lobata were fragmented with hammer and chisel by several volunteer fisherfolk. The fragments were cultured from April-August 2018 in an in-situ fixed-leg nursery at a depth of approximately 2m. Maintenance was performed approximately weekly and measurements of growth (i.e., volume change) were conducted monthly utilizing an Olympus Tough TG-870 camera and ruler while freediving. The fragments were then transplanted to a selected restoration site and monitored for one month.
A hierarchical Bayesian log-linear regression model indicated that 71.5% of growth (volume change) variation was attributed to coral genotype and 18.1% of growth variation was attributed to the individual fragment, with some individual fragments growing particularly slower or quicker. Overall, the average monthly increase in coral fragment volume was 30.1% per month (95% CI 21.7-38.7%/month) with the greatest monthly increase for a genotype at 50.8% per month (95% CI 23.5-66.1%/month).
It is not surprising that coral genotype had significant influence on growth rate. The growth variation among fragments of the same genotype could be attributed to individual differences and the fragmentation method used, which could have caused more stress to some fragments than others. Though high growth rates were documented for the lobe coral, the location and shallow depth of the nursery required significant maintenance, which may not be feasible in a remote fisherfolk community.