Season 5: Episode 3

Emergency Services

Coral reefs are some of our planet’s most beautiful and biodiverse habitats. They’re also rich with sound, a bustling marine metropolis whose future is severely threatened by climate change. In this episode, we discover the important role of listening in coral communities.

Guests

Credits

Transcript

[00:00] INTRODUCTION

AMY: In the beginning, it was quiet.

MUSIC

AMY: There were currents and waves. Downpours. Fractures. Eruptions. Eventually, the burble of oxygen released by communities of microbes in the sea.

But it took almost four billion years for the first complex life forms to emerge on Earth. They were soft-bodied things. Jellies. Sponges. Sea anemones. Corals. None of them were big talkers.

Last time, we met Earth’s first conversationalists: fish. 

UNK BOOP KWA

AMY: But as they began to fill the seas with their croaks and honks and growls, corals were already there, silently building reefs. Places for the fish and now many other animals to call home.

TIM: Coral reefs are some of the world's most diverse and special and beautiful and unique ecosystems.

AMY: Welcome to Threshold, I’m Amy Martin, and this is Dr. Tim Lamont, one of the world's leading experts in coral reef acoustics. 

TIM: I study coral reefs. Their degradation, and more positively, efforts we can make to restore them.

AMY: There are few habitats on our planet more wondrous than coral reefs—or more endangered. They are marine metropolises; underwater fountains of biodiversity. And they’re in big trouble. You’ve probably heard about how rising ocean temperatures are starving and killing the coral, leaving many reefs bleached and broken. But what might be less well-known is how important sound is in the coral reef story. 

TIM: When reefs are degraded, you can hear it happening. They go silent. And when reefs recover, or when reefs are restored, you can hear the noise coming back.

AMY: Even though corals themselves are very quiet beings, through the communities they create, they are speaking. And if we can learn how to listen, we might have a chance of getting them through this time of crisis.

INTRO MUSIC

[02:55] SEGMENT A

AMY: It’s just before sunrise, and I’m standing on a beach in Coral Bay, Western Australia, looking out toward Ningaloo Reef. And even though the reef itself is hidden beneath the waves, I can see its protective power—the way it absorbs the relentless force of the ocean crashing against it, leaving a buffer zone of calmer water close to shore. 

AMY: What you see from shore is a white line where waves are breaking. Pretty much as far as the eye can see out there.

AMY: Ningaloo Reef stretches 260 kilometers—or around 160 miles—end to end, and later, I’m going to take a boat out to it and go snorkeling. I can’t wait to see it up close, because it boggles my mind that something this big and tough could be made by an animal as small and soft as a boiled pea.

TIM: They're an ecosystem that is unique in the sense that it's made by an animal. It's got an animal right at the very base of it that constructs the whole habitat.

AMY: Again, that's marine biologist Tim Lamont, based at Lancaster University in the UK. In our first episode we heard about how some microbes make rocks, called stromatolites. Corals took that technology and leveled it up.

TIM: A coral is a tiny animal that forms these vast colonies, and these colonies create rock. They create and exude limestone skeletons beneath them. And those skeletons grow in tropical shallow waters, and create these wonderful shapes and patterns and structures, around which all sorts of other life congregates and lives and makes a home.

AMY: And corals actually provide housing inside their bodies too. Tiny algae called zooxanthellae live inside coral polyps. In exchange, they provide food and aesthetic services to the corals.

TIM: Corals themselves aren't colorful. It's the algae that lives inside them that gives them their color.

AMY: So corals are kind of animal, vegetable, and mineral all in one. Their lives are defined by togetherness, from the symbiotic relationship that sustains each individual polyp all the way up to the enormous communities they build. Not all reefs are made by coral—they can be made of stone, sand, even the shells of oysters. But tropical coral reefs are the rainforests of the sea—they’re bursting with life. And sound.

TIM: Absolutely, there's loads of different sounds. And that makes sense because underwater sound travels so well. So if you're an animal that lives in the water, sound is a brilliant means by which to communicate, means by which to discover things about your environments around you.

REEF SOUND

AMY: This is the sound of a reef in Indonesia.

TIM: So... so the dominant sound you hear is this, this crackle. And that's actually the sound of snapping shrimp. They make that sound with their claws.

AMY: These claw clicks actually produce miniature shock waves that are strong enough to stun or even kill small fish.

CRACKLE

TIM: What you're hearing is loads and loads and loads of individual claw clicks, which combine to make that static sound. And then punctuated through that at different times of day, you'll hear different types of fish noises, and they're really quite varied as well. So there's buzzes and chatters and grunts and whoops and purrs and some are high pitched and some are low pitched, some are really loud, some are quite quiet.

AMY: All of these sounds tell us things about the health of the whole community. The sheer amount of sound, and the diversity of it, signals a thriving reef. And Tim and his colleagues are frequently stumped by what they hear underwater, just like Lauren Hawkins and Miles Parsons, who we met in our last episode.

TIM: Again and again we find ourselves just shrugging our shoulders, no idea what makes that noise. Sometimes we joke that it's harder to think of anything we do know about coral reef sounds then thinking of stuff we don't know. (laughter) And so it's a really exciting field to be involved with, because the edge of knowledge is so close.

SOUND: boat

AMY: I'm on the boat now with a small group of other tourists, all of us looking pretty awkward in our wetsuits and fins. 

AMY: So I'm heading out to Ningaloo Reef from Coral Bay. The sea is this unbelievable turquoise color.

AMY: The plan for the morning is to do two swims, one on either side of the reef.

AMY: And this is actually the first time I've ever gotten close to a reef. So I'm pretty excited.

AMY: Soon we were there, and it was time for me to stop recording, get my snorkel in my mouth, and jump in.

SPLASH

MUSIC

AMY: Swimming through the coral jungles of Ningaloo was riveting. We started on the inland, protected side, where the water was relatively calm. Schools of brightly colored fish darted around me as I flutter-kicked over a dazzling array of coral fingers, blossoms, plates, and bulbs. It felt like swimming over a city made of flowers, inhabited by fairytale creatures. Sea turtles. Stingrays. Sea stars. I even spotted a small shark darting through the forest of living stone.

TIM: So many of your senses are just buzzing when you're underwater. Like what you can see, the shapes, the colors, the sense of busyness...

AMY: I felt like I had walked through the back of the wardrobe and floated into a magical world. I saw animals that looked like plants and plants that looked like animals. If one of them had swum up to me and started talking I wouldn't have been all that surprised. Anything seemed possible in this secret metropolis, hidden just beneath the surface of my ordinary, land-based existence.

TIM: When you're underwater, all you can do is sort of point and go, “Mmm! Mmm! Mmm!” (laughter) Like there's not that much you can say to each other. I think in some ways that adds to the experience sometimes.

AMY: Later, we swam on the outer side of the reef, where the full force of the ocean crashes in, and everything was loud and wild. I had to work to make sure the waves didn't throw me up against the coral. I could feel each swell growing, lifting me, and the fish, and anything else that wasn't anchored to the sea bed up and up, pushing us toward the reef faster and faster... until the wave broke, and we flowed back in the other direction, all of us utterly at the whim of the water.

MUSIC

AMY: My arms and legs seemed awkward and fragile; I've never felt more admiring of the easy grace of fish. And when an enormous manta ray swam past me, stately and serene… I don't have words to describe how that felt.

MUSIC

TIM: It's staggering, isn't it? When I took my family to show them a coral reef, I took them to Ningaloo.

MUSIC

TIM: It's so overwhelming some of the time. You know, there's all of this life and activity and color and shape and sound all around you, and you're just there, like floating in the middle of it all, like some, you know, big clumsy oaf. (laughter)

AMY: (laughter) Exactly!

MUSIC

AMY: Tropical coral reefs cover a tiny percentage of the sea floor—zero-point-one percent, to be exact—but they support the lives of at least a quarter of ocean species. From microscopic plankton to massive whale sharks, the life-giving power of coral reefs spirals up through the food chain and out in all directions—including up onto land, and into our human lives. Billions of people across the globe depend on reefs for the seafood they nurture, the coastlines they protect, and the medicines they provide. The World Economic Forum estimates coral reefs are providing at least 10 trillion dollars worth of services to humanity. Every year. But so much of what’s precious about a reef can't be translated into money. All around the warm midline of our planet, peoples' lives are bound to reefs through food, language, stories, songs, and spirituality. And as Tim talks, it’s evident how much these places mean to him, too.

TIM: And there's there's still a lot that we have yet to appreciate about these places as well. They're places where we have a very limited understanding, of some aspects of reefs, we're discovering new things about coral reefs all the time. And, and to...yeah, to think of these places as being as vulnerable as they are is...quite sobering. I find it really quite difficult to think about sometimes.

AMY: I find it quite difficult to think about too. But the fact is coral reefs are gravely threatened. And we need to face this reality if we’re going to do anything about it. So I asked Tim to give us a general outline on coral reef health, and he responds a bit like a physician giving a really tough diagnosis to a patient.

TIM: Coral reefs are facing more threats now than they have at any other points in human history. And we generally split them into what we call global threats and what we call local threats. And so global threats, to do with climate change. And so they, coral bleaching, which is caused by extremes in temperature. More often than not, it's marine heat waves that that cause the temperature of the water to rise, that causes a breakdown in the relationship between the algae that lives inside the coral and the coral itself. The algae is expelled and the coral can no longer photosynthesize. And often it will then starve and die a few weeks after that.

MUSIC

TIM: Some marine heatwaves are so intense that it's not the bleaching mechanism that kills the coral, it's it's just akin to heat exhaustion. The coral basically just cooks instantly. So heat is a big problem.

MUSIC

TIM: Climate change is also causing a worsening of these tropical storms and cyclones that are becoming more intense and more frequent. And so we're seeing storm damage go up.

MUSIC

TIM: And then outside of climate change, in these local threats as well. We're seeing around the world increasing amounts of overfishing, of destructive fishing practices, of pollution.

MUSIC

TIM: So there is a mixture of these big global climate change threats combined with these more localized threats from fishing and from pollution and from habitat destruction, and together that they paint a very bleak future for coral reefs. And it's not a future that is distant or is, you know, something that we have a lot of time to work out how to deal with. It's a future that is becoming a grim reality very quickly.

AMY: Our oceans are heating up at an alarming rate. 2023 was the hottest year in the ocean on record—until this year, when they got even hotter. As we release this episode at the end of 2024, we’re in the middle of the largest coral bleaching event ever documented. Every light on the ocean temperature dashboard is flashing red. The latest science indicates that if average global temperatures rise to one-point-five degrees Celsius, more than 90 percent of coral reefs will be lost. And if we go past that, to two degrees of warming, almost all of them will likely die. We’re currently on track for three degrees of warming by the end of this century.

TIM: A reef has some natural resilience and is able to bounce back from some disturbance. And that's part of what a reef should be. It can't deal with the amount of disturbance we're throwing at it, and the acceleration of the pressures that we're throwing at it as humanity at the moment.

MUSIC

AMY: These pressures change the soundscape of a reef like a sonic fingerprint left at the scene of a crime. This is a healthy reef, full of color and bustling with the sounds of life.

SOUND: HEALTHY REEF 

AMY: And here’s a reef in peril, going pale and very quiet.

 SOUND: DYING REEF 

AMY: How do you keep yourself sane? Like you're obviously a person who cares about all of this, and you're right in the water watching really hard things happen. And as you said, it's not, it's not in the future. It's now. How are you managing just the emotional impact of dealing with all of this?

TIM: Sometimes it's difficult that that's the first thing to say is that I wouldn't say that I manage it particularly well all of the time. Sometimes I do find it very hard and and I find it a particular challenge of my job. But that said, you know, lots of people have jobs where they work in difficult circumstances. People who work in health care, people who work in emergency services. Fields of work where you have to learn how to face difficult stuff in your job and then come home and not let it ruin your life.

AMY: I think Tim does work in emergency services. Just not in the way we typically define that term.  And like any health care worker, he doesn't just want to document decline. He wants to try to keep coral reefs alive.

TIM: Personally, I try and work on solutions. So whether that's working to try and improve the feasibility of restoration, whether that's trying to work with people in power in businesses or in politics or in powerful social movements. So I think it's a mixture of learning to deal with work in tough circumstances, which is something that a lot of people do, and also trying to alter the course of our work such that it is moving towards positive solutions rather than just describing depressing trends.

AMY: After seeing too many reefs go ghostly white and hearing them turn deadly quiet, Tim was determined to find ways to help. He knew reefs were incredibly dynamic places that can sometimes respond quickly to positive impacts, just like they do to negative ones.

TIM: The propensity these ecosystems have to change I find is really amazing. 

AMY: And he began to wonder if he could sound to help reefs ward off decline, or even come back from the dead.

TIM: It's this idea that by playing the right sounds, you can make places sound attractive to animals, and they'll then, you know, alter their behavior. You'll get increased settlement, increased immigration, if you like.

AMY: We’ll have more after this short break.

Break

[19:34] SEGMENT B

WATER

AMY: Welcome back to Threshold, I'm Amy Martin, and it's a November night. The moon is just past full. And the corals are spawning.

TIM: It's this amazing night to be out in the water, swimming around.

AMY: Marine biologist Tim Lamont has an idea for how sound could be used to help coral push back against all the threats they’re facing. And to understand how it works, we have to start here, during a spawning event, when millions of tiny corals release their eggs and sperm into the water.

MUSIC

TIM: In many species they all align, which is quite a magical thing. So on, on one night of the year, many of these broadcast spawners will all release their gametes all at the same time, and of course that maximizes the chance that they meet in the water.

AMY: Tim says nobody knows for sure how the corals manage to coordinate this way. They just know that it happens.

TIM: You can see the tiny little egg bundles floating up into the water, and you can see the sperm being released. That creates such a buzz in activity around the reef, because there's so many other animals that then also come out to feed on these eggs and the sperm, and it's chaos in the water. It's really loud. It's really busy. There's all sorts of stuff swimming around. It's going in your ears, it's going in your mask, it's going down your wetsuit. It's like, yeah, busiest night on the reef. It's like Saturday night, city center, you know?

AMY: Amidst all of this ruckus, some of the eggs manage to get fertilized and survive, and eventually, a baby coral is born. Small as a grain of sand. Bobbing around in the open ocean.

TIM: And they come back to the reef, swept on ocean currents and settle. So these free swimming coral planulae as we call them settle and become an adult coral polyp. And that's how you create a coral reef with millions and millions of those coral polyps.

AMY: It's called a biphasic life cycle. Birth and early development spent out in the open ocean; adulthood spent on the reef.

TIM: Corals have it in, other invertebrates have it. Even the fish have it. As an egg or as a very young juvenile, they'll be out at sea and then there'll be this sort of journey back to the reef when the organism is ready to start its adult life. Animals arrive, carried on ocean currents, and settle in new places. Corals will settle and start to create habitat. Different types of algae will settle. Fishes will arrive. And you can get a community developing, based on new arrivals from the open ocean, if you like.

AMY: Creating a healthy reef is a cooperative process, with interdependencies radiating out in all directions. The coral structures provide great hiding places for fish that are trying to hunt or avoid being hunted. The fish return the favor by peeing and pooping on the reef, providing nutrients that are crucial for the coral and the zooxanthellae inside of them. The fish also eat some other kinds of algae that would otherwise smother the coral—they kind of mow the lawn, clearing space for new coral polyps looking to settle. So healthy coral make for healthier fish populations which makes for healthier algae which makes for healthier coral and on and on. The fates of all the plants and animals here are tangled up together. So that’s why listening to fish can help us understand what’s happening with corals.

Tim knew that sound was a part of this community-building process—that young fish listen out for the symphony of pops, whoops, and gurgles of a thriving reef in deciding where to settle. But he wanted to know if that process could be hacked. When a reef was in decline, could he intervene, acoustically, and prevent them from going silent? Finding out meant he had to become a reef DJ, pumping out tunes designed to get the party started.

MUSIC

TIM: When we first tried this, I was doing my PhD, and, so it was very low budget science. It was a lot of fun putting it all together.

MUSIC

TIM: So the first experiment we did, we had these loudspeakers about the size of a dinner plate. They're sold as the loudspeakers that you would use to put in a swimming pool, for synchronized swimming so that the, the swimmers can hear the music, right?

AMY: I just instantly saw fish in a line…

TIM: It's all very Little Mermaid, isn't it?

MUSIC

AMY: These speakers were connected to little floating barrels that held mp3 players.

TIM: Which played one of our recordings of a really healthy sounding reef out to the loudspeaker.

AMY: The next step was to tie the speakers to little artificial patches of habitat made by Tim and his team.

TIM: Piles of rocks underwater, basically.

AMY: Then they pushed play and waited for someone to show up.

TIM: Repeatedly, repeatedly each day we'd go back and visit these reefs and count the number of fish that had arrived, that had settled. You know, I'd go down with a clipboard and it was fun, it was like watching the establishment of a tiny little, settlement underwater. Yeah. You know? You'd put your dive gear on, roll off the boat and go down, and wonder, you know, who's moved in today? (laughter) We found that on the reefs where we were playing the healthy sounds, twice as many fish would move in. You know, the community developed at twice the speed. And after 40 days, there was twice the abundance of fish.

AMY: In other words, it worked.

MUSIC

AMY: Hearing the buzz of a party made more fish want to come in and hang out.

TIM: So if we play the sound of a healthy ecosystem, then that is a very attractive sound. And that literally calls in animals looking for somewhere to live.

AMY: Tim's research gave us a new tool in the reef restoration toolbox.

TIM: What we have is a short term proof of concept experiment. In that location at that time, we were able to double fish abundance. There are a lot of other questions about whether that would work in different geographical contexts, on different reefs over longer periods of time, over larger spatial scales. And we don't know the answers to that yet. There are exciting experiments and studies going on around the world to try and get those answers. And time will tell what the results of those experiments will be.

AMY: But what about the animals at the base of all this—the corals themselves. Is it possible that they could be encouraged to settle by playing the sounds of a healthy reef? On the face of it, this seems improbable. Corals have no ears or even brains. But Tim has learned not to make assumptions.

TIM: Corals—especially in their little larval stage—are constantly surprising us with what they can do.

AMY: Tim says one of the intriguing things about the coral planulae—the free-floating newborn corals—is that they're covered in microscopic hairs.

TIM: And when you look at those hairs, they're actually relatively similar in structure to the hairs that are on the inside of our ears as mammals.

AMY: They're called cilia, and in humans, they play an essential role in hearing. They grow deep inside the ear, swaying and bending as sound waves hit them, and translating that mechanical energy into chemical and electrical signals that can be processed by our brains. And the cilia on the bodies of baby corals seem to behave in very similar ways.

TIM: These hairs will vibrate in response to a passing sound wave. And when we've studied these coral planulae in labs, people have discovered that they will change their shape in response to the sound of a healthy reef. They'll change their shape to one that sinks in the water.

AMY: The research on this is still emerging, but it seems that when the sound of a lively reef is nearby, the planulae will morph into a shape that helps them sink down into the water...where they're more likely to find a good place to call home.

TIM: And if you put them in a tube and you play the sound of a healthy reef from one end to that tube, they'll even start to swim down that tube towards the loudspeaker.

MUSIC

AMY: These tiny infant corals are somehow cueing into the hubbub of a reef. It's like their bodies become ears, bobbing along in the ocean. Half a billion years ago, long before anything was calling, or crying, or singing, these little beings may have been learning to listen.

MUSIC

AMY: So just to be clear about what we know and what we have yet to find out here: we know that baby corals definitely respond to reef sounds in the lab, and inside containers anchored to the sea floor. Whether or not those planulae are using sound to find and settle on reefs when swimming freely in the wilds of the ocean is still an open question. But again, these ancient creatures are full of surprises.

TIM: So there's some, some really quite amazing abilities of these, you know, animals that initially appear to be very simple but are able to respond to these complex acoustic cues in their environments around them.

MUSIC

AMY: New research on coral reef acoustics is coming out all the time, but so are new reports of dying reefs. We need legions of scientists like Tim, who are willing to commit their lives to finding out everything we can about coral reefs, and acting on that knowledge as quickly as possible. But scientists can only do so much. We're in a race against time—or more accurately, against ourselves.

AMY: You are nurturing this extremely important habitat in this absolute time of crisis and that maybe if we can get some version of them through the next 30, 60, 150 years then maybe there's a chance for them to get through this bottleneck. And do you see yourself that way, as like a coral shepherd moving them through a bottleneck?

TIM: That, I guess, is where…where this comes to roost as a story that involves everybody. The local efforts that we have can only really work within the parameters of the direction of global change. And, you know, t he climate story will be one that writes the narrative in the long term for all of this.

MUSIC

AMY: So we need all of these efforts, all at once. Hands-on, long-term, science-driven restoration projects, adapted to specific needs of different ecosystems. But those things won't be enough on their own. We also have to decide, as a global community, if we want to keep burning fossil fuels or if we want to have coral reefs in the future. Because we can't have both.

TIM: Reefs are valuable even outside of what they provide to humanity. They're fantastically beautiful, diverse and unique living structures. I think it would be a terrible, terrible indictment on humanity if we didn't do everything in our power to protect them.

AMY: Corals are survivors. For hundreds of millions of years, they’ve created a vital habitat that helped our planet transition from desolate silence to cacophonous life. But this wild flourishing didn't have to happen. And there's no guarantee that it will continue.

Life on Earth is resilient. But it's not inevitable and it's not indestructible.

REEF SOUND

CREDITS

AMY: This episode of Threshold was written, reported, and produced by me, Amy Martin, with help from Erika Janik and Sam Moore. Music by Todd Sickafoose.  Post-production by Alan Douches. Fact checking by Sam Moore. The sounds of coral reefs and fish you heard in this episode were generously provided by Tim Lamont and the following scientists: Ben Williams, Emma Weschke, Eric Parmentier, Isla Keesje Davidson, and Steve Simpson. Big thanks to all of them. This show is made by Auricle Productions, a non-profit organization powered by listener donations. Deneen Wiske is our executive director. You can find more about our show at thresholdpodcast.org