Kategorie: News
How to Entice Coral Larvae to Stay
Saving a reef often starts on a very small scale - namely, with a single coral settling on the ocean floor. Researchers at the Scripps Institution of Oceanography in California tested two tools for this purpose off the coast of Hawaii: the sounds of a healthy reef and a coating of living bacteria.
The study was published on October 8, 2026, in the journal Communications Biology. It focuses solely on this first step - the settlement of the larvae - and does not yet address a fully regrown reef.
Why Colonization Is So Important
Corals begin their lives as tiny, free-swimming larvae. Once they find a suitable spot, they settle and grow into a colony. On damaged reefs, both the larvae and the signals that tell them this is a good place to stay are often missing. That’s exactly where this experiment comes in.
A healthy reef is not silent. Fish, mantis shrimp, and other crustaceans create a dense soundscape that is significantly thinner on damaged reefs. The researchers wanted to know whether larvae could be attracted by this sound.
Speakers, Sound Modules, and Bacterial Film
For the field experiment, the researchers first recorded the sounds of a healthy reef off Oʻahu over the course of an entire lunar cycle. In July 2024, they played these recordings in Kāneʻohe Bay at a depth of 4.5 meters through an underwater speaker for two weeks, from sunset to sunrise each day. Thirty-seven artificial structures were placed around the speaker, at distances ranging from 1 to 42 meters. Among them were 19 coral settlement modules.
The second ingredient is called BRINK (“Bacterial Reef Ink”), or reef ink made from bacteria. It is a light-cured gel containing two bacterial species designed to encourage coral larvae to colonize the structures. It was developed by Natalie Levy and Daniel Wangpraseurt, among others. According to an earlier study in PNAS Nexus, BRINK increased the colonization rate of the species Montipora capitata by more than fivefold in the laboratory. This had not yet been demonstrated in the ocean. Some of the structures in the field trial were coated with BRINK, while others were not.
The researchers counted the offspring of Montipora capitata, a stony coral common in Hawaii. Divers inspected the structures one and two weeks after the new moon, during the species’ spawning season. They used blue light and a yellow filter for the count.
Most larvae settled on the structures near the speaker. The structures coated with BRINK performed the best. The design of the modules also played a role. The authors consider the combination of these three approaches promising enough to justify larger follow-up experiments.
However, the authors remain cautious. Proximity to the speaker does not prove that the sound attracted the larvae. The distribution could just as easily be explained by chance, fish that eat young corals, or the location of the structures on the seafloor. The experiment was conducted with a single speaker at one location during a single spawning season. It remains to be seen how the system would perform under stronger currents, during other seasons, or with other coral species.
Furthermore, the 3D-printed structures were tested only with sound, not with BRINK. For future experiments, the researchers recommend combining both.
Fish larvae also responded
A second study by the team led by Ph.D. candidate Océane Boulais was published simultaneously in Scientific Reports. Homemade cameras counted fish larvae at a site exposed to sound and at a control site. At the site with reef sounds, up to fourteen times more fish larvae arrived. The result held true even when the speakers were swapped.
A Reef of Technology and Nature
Both studies are supported by a funding program from the U.S. research agency DARPA called R3D, short for “Rapid Resilient Reefs for Coastal Defense.” The goal, then, is to use reefs to protect the coast. As a next step, the program plans to create a 50-meter-long hybrid reef off the coast of Oʻahu, consisting of artificial structures and corals. According to Scripps, it is expected to cost around 22 million U.S. dollars. The corals are scheduled to be deployed in late 2026 or early 2027.
Whether reefs actually recover faster with sound and biomaterials will only become clear after several years of observation. The Hawaii experiment provides a starting point for this. Further experiments with appropriate control groups are needed to determine how robust the effect of the sounds is.
Further information:
Press release from UC San Diego / Scripps Institution of Oceanography
Original study in *Communications Biology*, DOI 10.1038/s42003-026-10932-3