Microbial living materials promote coral larval settlement

The global decline of coral reefs calls for new strategies to rapidly restock coral populations and maintain ecosystem functions and services. Low recruitment success on degraded reefs hampers coral sexual propagation and leads to reduced genetic diversity and impaired reef resilience. Here, we introduce a Bacterial Reef Ink (Brink) to assist in coral larval settlement. Brink is a photopolymerized living material that can be rapidly applied to restoration substrates and has been formulated to cultivate two settlement-inducing bacterial strains (Cellulophaga lytica and Thalassotalea euphylliae). Settlement assays performed with broadcast spawning (Montipora capitata) and brooding (Pocillopora acuta) Indo-Pacific corals showed that Brink-coated substrates increased settlement >5-fold compared with uncoated control substrates. Brink can be applied as a flat coating or patterned using light-assisted 3D bioprinting, enabling diverse applications in reef restoration and engineering. This approach demonstrates the potential of functional living materials to enhance coral ecosystem engineering and support coral reef rehabilitation.