The role of substrate materials for the survival and growth of coral micro‐fragment sheets

Biofouling can have a negative impact on the survival and growth of corals in aquaculture. For coral aquaculture to support reef restoration, there needs to be a cost‐effective and efficient method that reduces the reliance on labor for coral maintenance. Here, we tested whether material types including alumina, concrete, glass, polyvinyl chloride, aragonite, and a biopolymer (PHBV/CaCO 3 ) blend, combined with manipulations of porosity and textures of some material classes (totaling 13 material combinations), exhibit innate properties that limit the colonization by competitive macroalgal taxa. Fragments from Acropora millepora , Platygyra daedalea , and Porites lutea were attached to each tile material to assess their survival and growth in aquaria. Acropora millepora did not survive the experiment, with mortality of all fragments by week 24. Material types, their porosity and textures, had a significant impact on the fouling community that developed on the tiles. Nontextured and low porosity materials such as fully sintered alumina (porosity 0–10%, roughness 4–8 μm) and specially manufactured concrete tiles that were smooth (porosity 10–20%, roughness 0–4 μm) had the lowest level of fouling after 12 weeks. This also translated to better growth by P. lutea fragments, doubling in size, to form sheets covering 40% of tiles after 12 weeks. A biopolymer comprising 60% Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and 40% CaCO 3 (porosity 0–10%, roughness 0–4 μm) performed the best in terms of reducing fouling and promoting growth of coral fragment sheets; however, further testing is required to assess the environmental acceptability of this biopolymer composite prior to reef restoration applications.