According to today's guest, a reef at its peak sounds something like this.

But when a reef falls on hard times, things can go awfully quiet.

I'm joined today by conservation bioacoustics researcher Isla Keesje Davidson, who studies the changing soundscape of the sea.

So, Dr. Davidson, why is it important that we listen to the sound of a coral reef?

It's quite an exciting space, when you think about how far our understanding and learning has come for the ocean in general but then coral reefs in particular.

If you think about how Jacques Cousteau described the oceans as The Silent World in the sort of 1950s, and we're starting to learn more and more about how actually they're hardly silent-you know, they're incredibly acoustically diverse-and coral reefs are a particularly loud and diverse set of sounds that you can hear, but also they're really interesting and important ecosystems to understand.

They don't cover a whole lot of the planet's surface, about 0.1 percent, but a quarter of all marine species that we know depend on coral reefs at some stage in their life, you know, so this is a real hustle and bustle of life that's happening there.

And it's incredibly acoustically diverse.

And so you can think of all these different pops and chirps and grunts and snaps that happen there.

And then you might think, "Okay, so what, what's the interest in that?"

Well, we know that, for example, new generations of larval fish, which are as tiny as a little candy, they are up in the open ocean, and they need to hear the sound of the healthy reef to actually find it-to settle, to start their life on the reef.

And recently research has also shown that the coral actually use sound to find suitable spots for themselves to settle.

So if you think about: coral reefs can be thousands and thousands and thousands of years old, and one coral can be-you know, can grow to 5,000 years old itself, and they grow on the shoulders of their ancestors, and they need to hear that space to actually find it, to be able to continue those generations of growth.

And that's part of what makes these ecosystems so important for the oceans but also for the entire planet.

I didn't realize that hearing was important for coral. I think that's probably surprising to a lot of our listeners. Could you say more about that?

If you think about how us as a species, as an animal, we are using a diversity of our signals to communicate, to interact with each other and to sort of navigate our world.

And underwater they're doing it-the exact same thing; they just have a, a different set of signals and a different use of their different sensory systems to do that.

And coral reefs are-if you think about it, you've got that skeleton of that structure that gives all these different habitats for the diversity of life that lives there.

So the corals themselves are using a diversity of those signals to recognize, "Okay, this is a good spot. This will be safe," or, "I can recognize that there are other corals here, so this is probably a good place to start trying to live."

And they'll adjust their sort of movement behavior, responding to what they hear.

And sound is a really-quite a good signal underwater.

It travels five times faster and therefore much further underwater than it does in air.

So if you think about the complexity of a coral reef space, if you're trying to keep sight of, maybe, a fish that's important to you-it's part of your shoal, or it's your mate-and you suddenly can't see them anymore, that could be pretty dangerous for the life of, for example, a little fish.

But if you can reliably hear each other 'cause that travels so much further, then you've got a really reliable signal to keep you able to survive and thrive in that environment.

That's so interesting.

I feel like most folks, what they know about sound in the water kind of begins and ends with them being told as a kid why they shouldn't tap on an aquarium window.

But how did you get interested in this field of research?

So I started with a fascination of: How are these different species that occupy these underwater worlds, how are they interacting with each other?

And the behaviors that they have to do and that they choose to do in their world, in their lives, what does that mean, and how do we learn from those different interactions and understand what that can mean for the biodiversity in a space?

Because we understand that biodiversity is really important.

You know, it's more than just what's there and what's not there; it's how these different individuals, these different species are interacting with each other and what that means for their sort of capacity to continue to live there.

As I was sort of curious about that and learning more about animal behavior and the impacts of how they use their different senses to communicate with one another, and I focused in on coral reefs.