What Sound Can Tell Us About The Health Of Our Reefs

Coral reefs are some of the most visually specular sights in the ocean, but did you know they’re also some of the nosiest?

New research has recorded the sounds of a coral reef coming back to life thanks to a reef restoration project, and researchers have been able to capture a choir of sea life that we’ve never heard before.

The coral reef is in Indonesia and it was destroyed by dynamite fishing, that’s where fisherman blow up coral reefs to catch fish. It’s no surprise but the dynamite fishing had a significantly negative impact on the health of the reef.

But a reef restoration project where Mars Inc. (yeah the guys who make Mars bars) worked with local communities to install metal frames underwater. Baby corals were tied onto the frames, and then nature was left to do its magic. As the coral began to grow, fish started coming back into the reef and that turned a silent seascape soon into a cacophony of sound.

With microphones underwater, researchers were able to capture the ecosystem reawakening.  Tim Lamont was one of the researchers on the project who said “most people don’t think of coral reefs as noisy places. But I think maybe that’s because our ears don’t work brilliantly underwater… they’re the loudest ecosystems in the sea. And so we’re constantly being surprised and amazed by the new and different and wacky sounds that we hear when we listen on coral reefs.”

The team captured sounds of a whooping yellow and blue damselfish, as well as loud clown fish making knocking sounds by biting their teeth together, chatting in an anemone.

Sound helps us understand the health of coral ecosystems in a few different ways. It allows us to hear animals we never see, so we’re able to get a better picture of the number of animals on the reef. But reefs operate very differently at night to how they do in the day and using sound, we can also listen at night to figure out what’s happening in the dark.

Sound is also an essential tool for fish, as Tim noted that “fish are making value judgments about which reef to live on based on what it sounds like… So if we can understand reefs in that way through the through the ears of a fish, then we can understand which reefs fish are likely to be attracted to in the future.”

Sound has the potential to become a valuable way for us to understand and measure the health of coral reefs. It’s something we’ve been doing on land for a long time, and it’s played a vital role in capturing the wellbeing of forest ecosystems.

In Australia, a team in 2020 actually recorded sounds of coral on the Great Barrier Reef and that recording will play a vital role in understanding the health of the reef as it continues to experience distress due to climate change.  Sound could even become a tool we use in reef monitoring all over the world, to ensure we have healthy reefs for the next generation.

When asked his favourite sound from the project Tim said his favourite were “the mystery ones where we don’t know what animals are making them.. There’s a sound that we kept calling the foghorn sound because it sort of comes out of nowhere and blares over the reef… we still have no idea what fish makes it. But it’s, it’s amazing when it happens, because you very rarely hear it in isolation, you know whatever fish is making it that they’re talking to each other.”