MEPS 728:15-24 (2024)  -  DOI: https://doi.org/10.3354/meps14504

ABSTRACT: The early life history of scleractinian corals is largely unknown. In this study, we compared the settler numbers and post-settlement survival of Acropora aff. tenuis larvae on a square hollow section (SHS) substrate at 10 stations and 2 depths (20 sites in total) from the mouth to the back of a small bay. The number of settlers tended to be lower at the back of the bay. Survival rates 15 mo after settlement were 2.5 times higher in the shallower waters at the back of the bay, and 2.5 times higher in the deeper waters at the middle and mouth of the bay. Water depth and temperature, photon flux, current velocity, sedimentation, water column and interstitial water nutrients, and algal cover were measured at each site, and a significant correlation was found between settler numbers and sedimentation. The best models of physical environmental factors affecting post-settlement survival in each monitoring period showed that daylight intensity on sunny days and algal cover had a negative effect on survival 3 and 15 mo after settlement. It is unlikely that light intensity would have a negative effect on corals, for which symbiosis with zooxanthellae is essential, but it is partly expected that the effects of algal cover and water depth on the light environment in the microhabitats within the SHS would vary with the environmental gradient in the bay. This study suggests that the relationship between environmental factors and juvenile coral survivorship is complex, even within a small bay.

KEY WORDS: Coral reef · Field experiment · Initial mortality · Environmental factors · Restoration