Maria Vanessa Baria, PhD
University of Ryukyus
Active restoration is an option to restore degraded reef areas which have insufficient larval supply and high post-settlement mortality. The primary considerations in active restoration approach are increase in live coral cover and its effort cost. Two materials used in actively restoring degraded coral reefs are asexually- and sexually-derived corals. This study was conducted to determine and compare growth and survivorship of asexually- and sexually-derived corals of Acropora granulosa in the in situ nursery and subsequently on degraded reef areas in northwestern Philippines. For sexual propagation, gametes spawned from gravid colonies of A. granulosa were collected and reared until settlement (200 days) at an outdoor hatchery facility. After 6 months, coral juveniles were reared at the in situ nursery along with coral fragments (asexual propagation) then outplanted to a degraded reef (referred to “coral bommies”). Cumulative survival of sexually-derived corals was significantly higher than asexually-derived corals reared at the in situ nursery (100% and 83%) for 200 days and coral bommies (27% and 21%) for 382 days. Growth of sexually-derived corals was also significantly higher than asexually-derived corals at in situ nursery (4.65 ± 0.77 and 2.65 ± 1.51cm3, mean ± sd, respectively) and on coral bommies (25.1 ± 11.57 and 10.25 ± 4.04 cm3, respectively). Production cost is more expensive in sexual (3.96 USD) than asexual (3.20 USD) mode of propagation. However, 14 months post-outplantation showed that individual cost of sexually derived corals is cheaper than asexual counterpart, 14.17 and 18.74 USD, respectively. Size advantage and or the genetic variability of sexually derived corals could have enhanced its survival both in in situ and on the reef. Hence, it is recommended that sexually-derived corals be used in restoration of degraded reefs in order to attain higher success rate.
Keywords: Coral restoration; Coral degradation; Sexual propagation; Asexual propagation; Acropora granulosa