Coral spawning and spawn-slick observation in the Philippines

Knowledge on coral reproduction has implications for the restoration and recovery of degraded coral communities. Few studies on coral spawning timing and extent of synchrony have been recorded in the most biodiverse and disturbed coral reef ecosystems of the Coral Triangle. In the present study, the reproductive timing in 2015 and 2016 is reported of an Acropora assemblage in Magsaysay reef, Bolinao-Anda Reef Complex, northwestern Philippines. Fertile colonies were present in February and March, with highest abundance 6 days after full moon. All sampled colonies of five Acropora species were fertile on 12 March 2015 and 73–100% of six Acropora species on 29 February 2016. Other species had fewer mature colonies (40 and 33% respectively), suggesting that these may spawn in other times of the year. Synchrony in gamete development and mass spawning were exhibited among species. At least eight Acropora species were observed spawning between 9 to 11 days after full moon in March of 2015 and 2016. Mass spawning resulted in spawn slicks, which were dispersed by the current generated by the ebbing tides and winds. This observation suggests that the Magsaysay reef may be an important source of larvae that may recruit unto nearby reefs, which could potentially initiate recovery of degraded coral communities.