Romeo M. Dizon

Physiological and ecological aspects of coral transplantation

The growth and mortality of transplants of two species of scleractinian corals, Porites cylindrica Dana and P. rus Forskal (1775), were monitored over 16 months in a reef in the northwestern Philippines. Transplants were in two sizes (nubbin, ∼8 cm in length; and fist-sized, ∼8 cm in diameter) and deployed at two depths (1 and 10 m). Specimens at the shallow depth had more rapid growth than the deeper ones. Light had significant effects on coral growth while temperature, salinity, water motion and sedimentation did not. Smaller corals consistently registered greater percentage increases in size as compared to the larger ones. Small transplants of P. cylindrica showed higher percentage growth rates than those of P. rus. Contrary to expectations, there were no differences in transplant mortality due to size. Over the course of the experiment, mortality was generally confined to the shallow depth. It was brought about either by algal competition or by strong water movement.

Multi-species spawning of corals in north-western Philippines

The Philippines has more than 30,000 km of reef area and hosts some of the world’s most diverse and endangered coral communities, however there is little information on patterns of coral reproduction (Bermas et al. 1992) and to date there are no published accounts of direct spawning observations. Sampling to determine the reproductive state of Acropora species and in situ observations of coral spawning was conducted in 2006 and 2007 at sites close to the Bolinao Marine Laboratory (BML) in northwestern Luzon, (16 22¢N 119 54¢E). Prior to the full moon in March 2006, 22 sampled Acropora species (67% of colonies, n = 208) contained white or pigmented oocytes large enough to be visible in branches that were fractured artificially underwater (for methods see Baird et al. 2002) suggesting a seasonal peak in reproduction from March to May. Night dives were carried out during the week following the full moons of 15 March and 14 April 2006; and 2 April, 2 May and 1 June 2007. Multi-species coral spawning was observed during all of the months of observation except in April 2007. Across all months of observation, a total of at least 36 scleractinian species belonging to 14 genera and 7 families (Acroporidae, Mussidae, Agariciidae, Faviidae, Oculinidae, Merulinidae and Poritidae) broadcast spawned (Fig. 1), with a maximum of 13 species observed on the fifth night after full moon in May 2007. Further studies are required to establish the extent of spawning at other times of the year and the reproductive patterns of corals elsewhere in the Philippines.

Successful Transplantation of a Fragmenting Coral, Montipora digitata, for Reef Rehabilitation

The scleractinian coral Montipora digitata (Acroporidae) is a common reef flat species that thrives under high levels of light and water turbulence, and propagates successfully by natural fragmentation. It was used for transplantation experiments in an attempt to restore a degraded lagoon environment in the northwestern Philippines. Branches about 5 cm high from a natural population in the lagoon were transplanted to dead coral outcrops or knolls in two locations (Binlab and Malilnep-Ac) with different environmental characteristics. Growth and survival were significantly better at Malilnep Ac, which resembled the natural habitat of the species more closely. Environmental conditions at this site also favored the establishment of a greater diversity of species around the coral transplants. There was no difference in performance between transplants on vertical and horizontal surfaces, and the transplants showed limited differences due to density within the experimental range. Significant survival of detached, transplanted colonies or fragments thereof around the bases of the experimental bommies at the more successful site was an additional positive outcome. Water motion showed significant effects on survival and growth, possibly enhancing the suitability of the more successful site for transplantation. These results demonstrate the potential of coral transplantation to initiate the establishment of natural communities in degraded reef areas, a concern for coastal managers in developing countries.