Micro-fragmentation of four coral species towards the assembly of modular 3D structures for restoration.

Coral reefs are experiencing severe decline due to anthropogenic stressors and natural disturbances, necessitating innovative restoration strategies. Micro-fragmentation is a method used for accelerating coral growth and enhancing reef rehabilitation. This study investigates the use of micro-fragments to cover an artificial three-dimensional bottomless cube structure designed to increase space efficiency, structural complexity, and scalability for coral restoration. We examined four Hexacorallia species, Cyphastrea microphthalma, Galaxea fascicularis, Pocillopora favosa and Stylophora pistillata to evaluate species-specific and source colony-specific survival and growth rates. Over 204 days, micro-fragments demonstrated both tissue growth and fusion, at varying degrees, with G. fascicularis exhibiting the highest survival and growth rates. Corals grew and fused over the surfaces of the test structures and fused across corners. Our results demonstrate variation in fragment survival and fusion potential among species and colonies, highlighting the importance of source colony and species selection in restoration efforts. Notably, we found that coral fragments could successfully fuse after six months of separation. This approach has broad applications in reef restoration and the ornamental coral trade, offering a scalable solution to lessen the impact of coral harvesting on natural ecosystems. Our findings highlight the potential of designed 3D structures to support efficient coral restoration in degraded reef environments.