The Coral Larval Box “ <scp>CoLaB</scp> ”: a novel and low‐cost method for delivering competent coral larvae onto degraded reefs for restoration

Abstract Introduction Coral reef restoration strategies are rapidly evolving to restore corals and reef functions in response to accelerating disturbances worldwide. One active restoration technique that is rapidly gaining momentum is the larval enhancement method which involves the introduction of cultured coral larvae directly onto degraded reefs. Objective In this study we developed the Coral Larval Box (CoLaB) as a novel low‐cost method for delivering millions of competent coral larvae onto degraded reef areas, serving as a complementary restoration tool to reef‐based coral larval culture. The efficacy of the CoLaB to release larvae and facilitate coral settlement was tested. Methods Thirty‐nine million eggs were collected and reared from spawn during a mass coral spawning event in March 2023 in the Bolinao‐Anda Reef Complex, northwestern Philippines. Six days later 1 million larvae were transferred into each CoLaB device for dispersal onto degraded reef sites. Results High larval settlement was recorded on limestone tiles in larval‐enhanced plots within 2 days post‐release, while no settlers were recorded on tiles in control plots. Most of the settlement tiles in larval plots hosted at least one coral settler, with the highest densities observed on tiles placed closest to the CoLaB. Conclusion These results demonstrate that the CoLaB is an effective larval delivery system for reef restoration at a very low cost. Coral larval release close to the reef substrata using CoLaB enhances larval settlement that may catalyze recruitment and faster coral population recovery.