INTRASPECIFIC VARIATION IN PHENOTYPE AMONG NURSERY-REARED STAGHORN CORAL Acropora cervicornis

Staghorn coral Acropora cervicornis once dominated south Florida and Caribbean reefs, but has declined up to 98% throughout its range in recent decades due to a variety of stressors. One of only two branching coral species in the Caribbean, A. cervicornis builds important reef structure and provides habitat for ecologically and economically important fishes and invertebrates. A. cervicornis became one of the first corals listed under the U.S. Endangered Species Act in 2006, resulting in an impetus to develop effective methods to aquaculture this species for use in active restoration. Selection of genotypes for use in culture generally relies on proximity and availability of healthy wild colonies rather than an evaluation of performance. However, genotype is important to consider as it may affect growth rates and susceptibility to bleaching and disease in nurseries.

To quantify differences in phenotype, ten known genotypes from the Coral Restoration Foundation nursery in Tavernier, FL were selected for study. Three source colonies per genotype were used to control for any intercolonial variation in phenotype. Four 5-cm fragments were clipped from each of the three source colonies and suspended from four identical PVC tree structures for grow-out. Total linear extension (TLE) and number of branches were measured at 45-day intervals for a period of six months. These measurements will be continued for an additional five months. Buoyant weight was determined for each fragment initially and again after five months in order to assess calcification.  

After six months, significant differences in growth parameters, including rate of TLE (Fig. 1), calcification, and branch formation were detected between genotypes at a significance level of α=0.05. Phenotypic variation documented in this study has implications for nursery management and may play a role in future outplant success and gamete compatibility in spat stocking efforts.