Growth and survivorship of juvenile corals outplanted to degraded reef areas in Bolinao-Anda Reef Complex, Philippines

Abstract

The worldwide decline of coral reefs due to natural and anthropogenic disturbances necessitates the development of techniques to restore damaged reefs. The potential use of sexually derived coral propagules as a tool in coral reef restoration has recently been actively investigated. This study was conducted to determine growth and survivorship of juveniles of the reef-building coral Acropora valida, outplanted at a degraded reef. These juveniles were products of sexual propagation, i.e. involving coral spawning, gamete fertilization, larval rearing and settlement, and juvenile rearing, at an outdoor hatchery facility. Six-month-old juvenile corals attached to rubble inserted into plastic masonry wall plugs (‘tox’) were outplanted to three experimental bommies at the Bolinao-Anda Reef Complex, northwestern Philippines. Cumulative survival of outplants was 67.5±7.6% during a study period of 183–190 days, with no apparent difference among bommies. The juveniles grew with a 37-fold increase in ecological volume – from 1.25±0.97 cm3 (1.1±0.3 cm mean diameter) at outplantation to 46.19±35.49 cm3 (3.8±1.1 cm mean diameter) at approximately 6 months. The results of this study substantiate the use of sexually derived coral propagules for reef restoration. Cost analysis revealed sexually produced corals to be more expensive than asexual counterparts. Further developments or refinements in the culture technology for sexually derived corals for reef restoration are needed to enhance cost-effectiveness.