Under Water Sounds Encourage Coral Settlement

Coral reefs are magnificent and magical places. They are called the rain forests of the sea because despite covering only 1% of the sea floor, 25% of all marine life depend on reefs at some point in their life. The building blocks for these vital reefs are tiny coral polyps – invertebrate animals that are part of the same group as jellyfish and anemones. The corals colonize, build on one another, and create a reef that works as one organism.

As we know, corals and the reefs they build are in trouble. Answering that call are scientists and volunteers worldwide. Their restoration efforts include research and coral farming, and now…playing healthy coral reef sounds under water.

It sounds crazy, but recent research has revealed that playing healthy coral reef sounds under water promoted recolonization on damaged reefs. The resettlement rate was 7 to 8 times higher on degraded reefs where the sounds were played.

Scientists from the Woods Hole Oceanographic Institution in Massachusetts have recorded healthy reef sounds for almost a decade, and have discovered that healthy reefs have complex, unique soundscapes. These sounds include fish calls as well as shrimp snapping and crackling. These sounds are important to drifting coral larvae (the size of a grain of rice) and provide clues about whether to settle on a reef and metamorphose into adults. Once they settle, coral cannot move, so they literally have a once in a lifetime choice about where to select a good home.

The results are encouraging. Underwater speakers can broadcast sounds over a wide area, and can be used both in coral nurseries and on reefs to heal and regrow coral reefs worldwide.