Jenny Fong1, Blake Ramsby2, Florita Flores2, Elsa Antunes3, Ateeq Rehman3, Muhammad Azmi Abdul Wahab2, Andrea Severati2, Andrew Negri2, Guillermo Diaz-Pulido1
1Griffith School of Environment, Coastal and Marine Research Centre, and Australian Rivers Institute – Coast and Estuaries, Nathan Campus, Griffith University, Brisbane 4111, Queensland, Australia
2Australian Institute of Marine Science, Townsville 4810, Queensland, Australia
3College of Science and Engineering, James Cook University, Townsville 4811, Queensland, Australia
To accelerate the recovery of coral reef systems, restoration efforts are being undertaken globally, including the use of sexually propagated corals. One of the main bottlenecks in upscaling the propagation of sexually derived corals is the high mortality of newly settled coral larvae on settlement tiles in marine aquaculture systems due to competitive interactions with macroalgae. While some macroalgal species, particularly crustose coralline algae (CCA), are known to positively influence coral larval settlement success, other macroalgal species have been shown to cause high recruit mortality. However, there is a limited understanding on how different substrate materials and their physical properties can influence the composition of macroalgal communities colonising the substratum and consequently coral recruitment success. Herein, we performed a mesocosm experiment using three substrate material types (i.e., 99.8% partially sintered alumina, concrete, calcium carbonate) with five surface texture classes ranging from 0 to 600 µm and assessed how macroalgal community composition varied across 10 weeks. Following six weeks of tile conditioning, a choice experiment using Acropora tenuis coral larvae was conducted to determine coral settlement success. Newly settled larvae were monitored for four weeks to examine their survivorship and interactions with macroalgal taxa. Overall, results from this study provide insights on the synergistic roles of macroalgae, substrate material type, and surface topography on the recruitment success of coral larvae, which contribute to improving the cost-effectiveness and scalability in using sexually propagated corals for restoration projects.