Mediation of growth by conspecific neighbors and the effect of site in transplanted fragments of the coral Porites attenuata Nemenzo in the central Philippines

Abstract.

To investigate facilitative and competitive effects of conspecific neighbors on coral growth, fragments of Porites attenuata were reciprocally transplanted between two reefs. Transplants were interspersed with dead coral fragments or live conspecifics and monitored for growth. Over 13 months, transplant performance differed between sites. Those from degraded Bais Bay grew significantly slower in all treatments compared with those from more pristine Apo Island, and Bais fragments branched less (Bais: 1.5±0.16/transplant; Apo: 8.1±0.66/transplant). Treatment effects were observed in Apo; fragments with live conspecifics branched less but grew taller, adding significantly more surface area than those with dead neighbors. Clonal fragments differed significantly in their responses, indicating environmentally induced effects. These interactions affected growth and morphology prior to physical contact between fragments. This illustrates a benefit of manipulating the biotic environment of early transplants: dense stocking in ocean nurseries could stimulate early growth, and subsequent spacing would allow lateral branching and reduce competition.