Microbial Living Materials Promote Coral Larval Settlement

This study introduces a photopolymerizable bacterial reef ink (Brink) designed as a living material for enhancing coral larval settlement. Brink combines poly(ethylene glycol) diacrylate (PEGDA) and gelatin methacrylate (GelMA) to create a robust, biocompatible hydrogel matrix encapsulating two settlement-inducing bacterial strains—*Cellulophaga lytica* and *Thalassotalea euphylliae*. Coral settlement assays using *Montipora capitata* and *Pocillopora acuta* showed >5-fold and >4-fold settlement increases, respectively, compared with uncoated controls. The hydrogels exhibited tunable stiffness, high bacterial viability (>80% after 7 days), and optical transparency suitable for coral–bacteria interactions. Brink represents a scalable, sustainable biotechnological tool for accelerating coral recruitment in reef restoration and conservation.