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What I Already Know About Coral Bleaching

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What I Already Know About Coral Bleaching

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I know that coral bleaching occurs when the coral reefs lose their vibrant colors and turn white. This can happen due to a variety of factors including climate change and pollution. When the coral reefs are bleached, they become more vulnerable to disease and death. Coral gets its color from algae which lives inside the coral, also providing it with food. If the water is too warm or polluted, these algae leave the coral because they can no longer withstand the unstable conditions. If the coral cannot recover quickly enough, it will die.

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This source has an interesting take on how we can monitor the corals' health and make them more resilient by using sound. We are taken back to the image of what coral looked like 100 years ago, vibrant, healthy, and surrounded by life. The amount of animals surrounding the reef naturally made a racket. This means that a healthy reef will also be louder than a less healthy version. Reefs are compared to a busy neighborhood due to their complex soundscape. This can be used to our advantage because recordings of the coral can give scientists a sense of how healthy/unhealthy it is. Divers will deploy the hydrophone (underwater microphone), then come back in less effort than diving down to the sea floor. This way of data collection has given us more evidence to what we can visually observe on the reefs. We are now able to use this research to compare all around the world and find our baseline of what is healthy again.

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This transcript was prepared by a transcription service. This version may not be in its final form and may be updated.

Danny Lewis: It's a hot summer day in New York City. And inside the Hall of Ocean Life at the American Museum of Natural History, tons of kids and adults are trying to keep cool. There's a lot of racket echoing around the life size sculpture of a blue whale hanging from the ceiling. But we're here to look at a different display.

Dr. Nathalie Goodkin: Almost 100 years ago, this is what the reef looked like.

Danny Lewis: Dr. Nathalie Goodkin is an associate curator in the museum's Earth and planetary sciences department. We're standing in front of a diorama depicting how a barrier reef near Andros Island in The Bahamas looked in June, 1923.

Dr. Nathalie Goodkin: The Elkhorn coral looks almost like tree branches without leaves, sticking up. And corals have microalgae that inhabit their surface, which give them all sorts of different colors. So we see pinks, and browns, and yellows. Sometimes you can see blues and purples as well.

Danny Lewis: The diorama is packed with corals taken from the reef, alongside models of all sorts of undersea creatures, like angel fish, lobsters, and parrot fish. If this was a living reef, Dr. Goodkin says it wouldn't just be pretty to look at. Just like this room we're standing in, it would be loud, a cacophony, even.

Dr. Nathalie Goodkin: The number of animals that are living on that reef are making an enormous racket. Even though you can't always see the life because, of course, the joy of the reef is it provides protection and places to hide.

Danny Lewis: But these days, the Andros Reef isn't nearly so beautiful or noisy, and the same goes for many others like it around the world. Corals struggle to survive. Without them, the other animals that rely on the reef will go elsewhere or die, leaving the once thriving environment, a quiet ruin

Ben Williams: Like a bomb site almost of just destroyed coral much of a time. On a degraded reef, often, these added sounds are missing.

Danny Lewis: This is Ben Williams. He's a PhD student at University College London, where he studies the soundscapes of coral reefs. He thinks one way to save coral reefs from destruction could be by focusing on how they sound. From the Wall Street Journal, this is The Future of Everything. I'm Danny Lewis. Today, we're listening to coral reefs, alongside some of the scientists working to save them, and learning how, in the future, the sounds of these ecosystems could help conservationists monitor their health and maybe even bring degraded reefs back from the brink of collapse. Stick around. It's really easy to talk about corals as if they're plants. Some look like trees, some like ferns, others like weird succulents. In reality, though, they're tiny animals. The babies even look kind of like jellyfish. And when they first spawn the baby corals, the larvae, can even swim around. It's only once they settle down that they start forming the rocklike skeletons that give reefs structure. And because they only have one chance to choose where they'll live for the rest of their lives. They're very picky. One thing that marks a healthy reef is noise.

Ben Williams: On a thriving, diverse reef, we hear loads of different sounds.

Danny Lewis: Ben Williams, the researcher from University College London, says healthy reefs have a rich, complex soundscape, kind of like a busy neighborhood.

Ben Williams: There's this constant backing track of snapping shrimp, which produced this crackling sound like a campfire. We hear these everywhere we go in the world. There's a Ambon Damselfish that makes this whooping noise, like a windshield wiper. There'll be this knocking, like someone's knocking on your door. That could be produced by another kind of clown fish.

Danny Lewis: But if the corals themselves get sick, things fall apart, like a city where all the businesses have shut down. It's almost eerily quiet. Corals can only live in about 1% of the ocean. That's still almost 1.4 million square miles, but they're struggling. Climate change is making oceans warmer and more acidic. There's pollution, overfishing, more frequent heat waves and diseases. In 2021, researchers from the University of British Columbia found that the amount of living coral has decreased by half across the globe since the 1950s. And with about a quarter of all ocean species depending on corals in some way, that's a lot less real estate to go around. Williams believes that studying audio recordings of coral reefs could give scientists a fuller picture of their health without the cost of having to send divers to look at them in person.

Ben Williams: It's really easy to just jump in the water, deploy the hydrophone, and then you can be back in the boat within seconds and going onto the next site.

Danny Lewis: It's like how some scientists monitor forests and woodlands. Microphones and little recorders can listen in on the birds, insects and mammals living there without having to worry about humans disturbing them. Williams wants to use the same techniques underwater.

Ben Williams: It's a really easy way to collect this data, compared to other methods, but that still needs us to go back and retrieve that hydrophone and to put it back out if we need to.

Danny Lewis: But if I can speak here as an audio producer for a second, let me tell you from personal experience that going through hours of recordings still takes a lot of work. And for the most part, I'm listening to people talking. I'm not trying to identify fish. That's like trying to pick out an individual voice from a recording of a crowded party in a big echoing banquet hall while everyone is moving around and talking over each other, and also, they're eating and drinking the whole time.

Ben Williams: Even with your best set of headphones, some of these sounds are really faint and you're squinting your ears going. Is that a fish? What did I just hear?

Danny Lewis: Not to mention that sound travels a lot faster and further through water, which is about 800 times denser than air. That makes it a lot harder to identify specific sounds and their sources.

Ben Williams: And I had a colleague recently who I think, in the space of a week, managed to analyze about four hours of audio.

Danny Lewis: That was just from listening to recordings that were only about a minute long. And William's colleague had over 100 hours of audio to sort through. The tool of choice for dealing with big data sets these days is artificial intelligence. Earlier this year, Williams published a study that he conducted as a student at the University of Exeter, where he trained a machine learning algorithm to do the work he and his colleagues were doing with their ears.

Ben Williams: We took recordings from nearby healthy reefs, nearby degraded reefs, and then also recordings from restored reefs. And these were taken across different times of days, day and night, and around the new and the full moon as we also know that the lunar cycle actually impacts the soundscape on coral reefs as well.

Danny Lewis: And he found that, while the computer program wasn't able to name every fish that bloop or grunted, it was able to identify whether a reef was healthy or degraded about 90% of the time.

Ben Williams: Our model essentially supported what we could visually observe on these reefs. So, those two mature restored sites were classified as healthy by our model. Whereas, that immature younger one that was only nine months old, still apparently sounded degraded.

Danny Lewis: There are limits to this study. The recordings were gathered at just seven sites in Indonesia in 2018. They also only used audio samples made during calm conditions. That means no serious storms and no motorboats. Some coral scientists are skeptical that analyzing audio will beat out traditional survey methods.

Emily Darling: My name is Emily Darling. I'm the director of Coral Reefs at the Wildlife Conservation Society.

Danny Lewis: Dr. Darling has sifted through survey data from reefs around the world to check in on their health over the years. And she spent plenty of time underwater taking notes herself.

Emily Darling: We're incredibly low tech. We've got pencils. We've got slates or clipboards. We have underwater paper. A lot of this is attached to rubber bands because, otherwise, your data sheets fly off into the water and you've got to go swim and hunt them down.

Danny Lewis: While these methods are time and resource intensive, she says they work. And Dr. Darling thinks underwater recordings are still too new to be of much use.

Emily Darling: I think we are starting a little bit at square one with these types of new technologies in the sense that, yeah, it sounds great to build a long term picture, but we've got to start from today. And so, a long term picture is really going to be 20, 30, 40 years from now, whereas backwards, to the Jacques Cousteau days, we have those 30 or 40 years of information, if not longer, on a lot of coral reefs.

Danny Lewis: Dr. Darling doesn't think bioacoustic analysis is practical in remote locations. And she says, even with the help of machine learning software, processing audio files would take too long for that data to be useful to the people whose livelihoods depend on coral reefs.

Emily Darling: And that's exactly why we use pencils, and rubber bands, and slates underwater. They work. We don't have to charge batteries if the power goes or the generator doesn't work. Our whole field trip isn't scrapped

Danny Lewis: Others, though, are excited about the potential of analyzing audio to check on a reef's condition.

Gabby Ahmadia: I know they do it in forests with birds and stuff, but it was really cool to actually try to apply it underwater.

Danny Lewis: Dr. Gabby Ahmadia is a director of Marine Conservation Science at the World Wildlife Fund. She's watched other scientists test out this technology in the field.

Gabby Ahmadia: I remember one of the researchers, she would snorkel out there for hours with her little floaty and her little microphone dropped in the water, and then we'll go and listen to the sound of the reefs. So it's really cool to see how far it's come.

Danny Lewis: She says it's changed the way she thinks about corals.

Gabby Ahmadia: Sometimes I try to take a moment and just... You're not really supposed to hold your breath when you scuba dive, but sometimes you want to hold your breath so you don't hear the bubbles and you can just listen to the reef. And you're like, "Oh, there actually, isn't a lot of noise here."

Danny Lewis: This blend of audio and AI isn't practical yet, but Ben Williams hopes that, within the next decade, it could lead to new tools that capture nuances divers might miss. He's now planning to send recorders to places like Australia's Great Barrier Reef, to Mexico, and the Maldives.

Ben Williams: Hopefully, we'll have enough of these around that we'll be able to get a representation of reefs all around the world to start seeing what's the normal baseline that we should see on these. And then if something starts to change, perhaps there's a bleaching event or another degradation event, we might notice that the soundscape has changed, and that can be a flag to us that something's going on at this reef, or alternatively, that the conservation measures and restoration being put in place at certain sites is starting to work.

Danny Lewis: Coming up, recordings of reef sounds might be able to do more than provide a checkup. Some researchers think they might also help make coral reefs healthier. That's after the break. Remember earlier when we mentioned that corals are animals? Well, one of the first things they do when they spawn is float away on the currents.

Dr. Aran Mooney: They look kind of like a jelly bean swimming around. And you wouldn't think of a baby coral being very mobile, but there's surprising mobile.

Danny Lewis: Dr. Aran Mooney is an associate scientist at the Woods Hole Oceanographic Institution, where he leads its sensory ecology and bioacoustics lab. He got his start studying dolphins and how they're affected by underwater noise made by humans, which led him to ask how those sounds affect the dolphins prey.

Dr. Aran Mooney: We want to know if squid could hear these loud echolocating dolphins coming. And we found out that squid could hear. They're actually pretty sound sensitive. And that just opened up this huge world for us.

Danny Lewis: And if squid can hear, maybe other undersea vertebrates can too, including corals. Dr. Mooney thinks one way young corals decide where to settle down for the rest of their lives is whether the place sounds right. So a few years ago, he tried an experiment, where he and his team placed cups of coral larvae out on a thriving area of a reef in the US Virgin Islands.

Dr. Aran Mooney: There's a lot of fish there, and the fish are crawling back and forth to each other, and it sounds really healthy, essentially.

Danny Lewis: He also placed baby corals on a reef that wasn't doing so well.

Dr. Aran Mooney: So it's missing the fish, and it just looks brown, and it looks like a little wasteland, right? There are some coral there, but there's not a ton. And it's just avoided those really nice sound cues.

Danny Lewis: After a few days wait, Dr. Mooney checked back. Lots of the corals placed in the healthy reef had settled down, but the ones on the degraded reef were still adrift.

Dr. Aran Mooney: There's a positive feedback loop. So if you have big three dimensional structures, essentially lots of coral heads, you're going to attract a lot of fish, and those fish are going to be chatting to each other, and that's going to sound really nice. And then that's going to attract more coral larva and keep rebuilding the reef.

Danny Lewis: Now, Dr. Mooney is trying to see how important that sound is by placing underwater speakers at depleted reefs and playing recordings of healthy ones. If the experiment works, he thinks the sounds could encourage corals to settle in reefs that need a little TLC. And it could tilt the scales just enough to help the reef bounce back.

Dr. Aran Mooney: There are some other questions that we need to do. Do we beat a little sound specific, or something for different species, or habitat, or geographic areas? I think we're at a stage where, if we get some really good results this summer, which we're hoping fingers crossed that we can start to integrate this in other restoration projects.

Danny Lewis: Restoring damaged coral reefs is hard and takes time, but it's possible. Scientists studying Australia's Great Barrier Reef recently found that some parts have more coral coverage now than they did when monitoring began 36 years ago. It's good news. And while experts warn that the recovery is fragile, there's hope that restoration efforts can work under the right conditions.

Gabby Ahmadia: There's a lot of different tactics around this. And, of course, there's not consensus around it because scientists like to take all these different approaches.

Danny Lewis: Dr. Gabby Ahmadia from the World Wildlife Fund says years of study in coral reefs has shown her the importance of trying new methods. And lately, she's been considering integrating reef sounds into her own work with corals.

Gabby Ahmadia: It's hard to do it at scale. The technology is not there yet. It doesn't mean we shouldn't do it. I think there's a lot of research going to how we can do this bigger and better and more cost-effective, but we're just not there yet.

Danny Lewis: But Dr. Ahmadia believes that tools like those Ben Williams and Dr. Mooney are working on, can be helpful to identify and protect those reefs that are most likely to survive in the coming decades.

Gabby Ahmadia: I think it's really important to give people hope. In conservation of coral reefs. We can't focus on the doom and gloom. We have to be pragmatic, but we need to start thinking about solutions and options instead of thinking that everything's just going to go away because then we really have no solutions for the future.

Danny Lewis: That hope can come from keeping these underwater communities healthy and thriving. And in the case of corals, that means noisy. The Future of Everything is production of the Wall Street Journal. Coral reef recordings were provided by Ben Williams, Ila Davidson, and Tim Lamont. Thanks also to Aran Mooney and the Woods Hole Oceanographic Institution for sharing audio. Stephanie Ilgenfritz is the editorial director of The Future of Everything. This episode was reported and produced by me, Danny Lewis. Our fact checker is Aparna Nathan. Jessica Fenton is our sound designer. Scott Saloway is our supervising producer. And Kateri Jochum is the Wall Street Journal's executive producer of audio. Thanks for listening.

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Why Sound Could be Key to the Future of Coral Reefs - WSJ's The Future of Everything - WSJ Podcasts

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With climate change warming the oceans, coral reefs remain some of the most vulnerable ecosystems. Keeping an eye on them can be time-consuming and expensive, since it requires divers to do spot-checks to see if the reefs are bustling, lively environments or if they are degrading into abandoned neighborhoods.

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This source talks about the rapid decrease of coral reefs due to warming ocean waters, ocean acidity, and pollution. Recent research has focused on transporting lab-grown corals into suffering ecosystems. We have had short term promising results, but still no promise for the future. Scientists have predicted that by the year 2100 ocean conditions will no longer be fit for corals' survival. The article also states that ocean acidification has led to the breakdown of coral. This issue along with warming are direct results of our carbon dioxide emissions, primarily from expanding agricultural land and the use of fertilizers.

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Over the next 20 years, scientists estimate about 70 to 90% of all coral reefs will disappear primarily as a result of warming ocean waters, ocean acidity, and pollution.

Expand that out to 2100 and it's "looking quite grim," says Renee Setter, a marine scientist at the University of Hawaii in Manoa. By 2100 there will be nearly zero suitable coral habitats remaining, eliminating nearly all living coral reef habitats.

Recent research, presented at the Ocean Sciences Meeting 2020, is focused on transplanting lab-grown corals into dying reef ecosystems in hopes that it will revive the reefs. While there have been promising results in the short term, by 2100 ocean environment will be too harsh for corals to survive.

In recent decades scientists have become increasingly alarmed at what looks like the inevitable fate of coral reefs. Scientists have tried to use underwater speakers to play continuous sounds of healthy coral reefs in hopes this entices marine life to return. While this, along with other artificial means to encourage coral reef growth has been successful to some degree, the increasingly harsh environment will lead to coral reef die-off.

Corals live in a mutually symbiotic relationship with photosynthetic algae, called zooxanthellae. Corals make up the hard calcium carbonate structure of coral reefs and provide protection and a home for zooxanthellae. In return, the zooxanthellae provide nutrients to the coral.

When surface ocean temperatures warm beyond a narrow livable range, the coral kicks out the zooxanthellae, causing "coral bleaching" and often times the eventual death of the coral. A similar process occurs when corals are exposed to pollutants running off of the nearby land.

Ocean acidification also plays a role in the death of corals. The more CO2 in the atmosphere, the more CO2 is absorbed into the oceans, causing the oceans to become slightly more acidic. This increased acidity makes it harder for corals to build their calcium carbonate skeleton and makes their skeletons more fragile and susceptible to breaking.

Warming ocean temperatures and ocean acidification are both a direct result of the increased CO2 emitted by humans, while the increased pollution runoff is primarily a result of expanding agricultural land and the use of fertilizers.

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Nearly All Coral Reefs Will Disappear Over The Next 20 Years, Scientists Say

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Over the next 20 years, scientists estimate about 70 to 90% of all coral reefs will disappear primarily as a result of warming ocean waters, ocean acidity, and pollution. Expand that out to 2100 and it's "looking quite grim," says Renee Setter, a marine scientist at the University of Hawaii in Manoa.

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This source states that healthy reefs can still be found, but they are surrounded by bleached corals. Scientists have recently found extensive patches of dead coral around the Great Barrier Reef. Australia is now in its third bleaching event in just five years. Researchers have used this devastation as a reason to find more solutions to this pandemic. Going back to the idea of lab-grown corals, scientists have found a way to make microalgae that are more tolerant to heat. This was created in hopes of restoring some of our lost coral reefs due to ocean warming. The algae were increasingly exposed to warmer temperatures, allowing the new coral-algae symbiosis to be heat tolerant. The next steps are now to allow testing on a range of coral species.

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Coral bleaching: Scientists ‘find way to make coral more heat-resistant’

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Researchers say they have developed a lab-grown strain of microalgae which is more tolerant to heat.

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In conclusion, if we don't stop coral bleaching, coral reefs will continue to die off at an alarming rate. This will have devastating effects on the marine ecosystem, as coral reefs are home to a vast array of marine life. Additionally, many communities around the world rely on coral reefs for their livelihoods, so the economic impact of coral reef loss could be significant. In said sources, several solutions have been found, and proven to be effective. The most effective way for the community to help would be to reduce our carbon emissions. This can be acheived by using less energy, driving less, and eating less meat. This will slow the effects of global warming. We can also expose of any trash to prevent excess waste. Overall, preventing coral bleaching requires a collective effort from the community. By taking action now, we can help ensure that coral reefs continue to thrive for generations to come.