Corals

Alex Re

Hey everyone, before I start the episode, I just wanted to say thank you to every single one of you who has been listening to On Wildlife. I really appreciate your support, and I just want this podcast to be the best it can be for you.

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Hello, welcome to On Wildlife. I'm your host, Alex Re. On this podcast, we bring the wild to you. We take you on a journey into the life of a different animal every week. And I guarantee you you're gonna come out of here knowing more about your favorite animal than you did before.

In this episode, I'm going to be talking about an animal that you might not have even known was an animal. They come in extremely bright colors. They're the homes for many different marine organisms. And they're in some serious trouble, which we're going to talk about later on in the episode. So I hope you can hold your breath because we're heading under the sea to talk about corals.

Coral may look like colorful plants, but they're actually animals critical to the function of the earth. There are approximately 6000 species of coral, and you can find them all over the world in tropical waters.

They grow close to the sea surface to take advantage of the sun's rays, but will never grow above sea level. And we'll talk about why the sun is so important for them later on in the episode.

Corals are classified as polyps and they're related to see and enemies and jellyfish. And they've been on earth for an extremely long time. Scientists have found evidence that they've been around for over 500 million years. And there are two different types of corals, stony corals and soft corals.

The difference as I'm sure you can gather by the name is their structure. stony corals form hard skeletons made of calcium, whereas soft corals are soft and bendable. Another difference is that stony corals have six fold symmetry, and soft corals have eight fold symmetry.

When you think about coral, you're most likely thinking of Elkhorn coral, which is stony. It has large branches extending outward, and it looks a little bit like a tree with no leaves on it.

Another type of coral is fan coral, and it's soft. As the name suggests, it has fan like limbs that are webbed together with a grid like pattern. Now, corals can live on their own, but they really thrive in colonies or as you know them reefs. They're even called the rain forests of the sea. What we see are these huge reefs, but an individual coral polyp is really small. They basically all come together to form a large reef, individual stony corals average about one to three millimeters in size.

But full grown coral colonies are massive, growing up to several tons, and they're dependent on one another for survival. And even though they look colorful, the actual coral polyps are translucent. They get their wonderful and bright colors from a symbiotic relationship with Zooxanthellae algae, billions of these Zooxanthellae live in coral reefs, and the corals need them for survival. But what's so great about them? Well, we're gonna find out right after the break.

The person that I want to recognize on this week's episode of notable figures in science is Dr. Emmett Chapelle, an American scientist and inventor. He got his master's degree in biochemistry from the University of Washington, and he's made multiple discoveries throughout his life. First, he discovered that not only plants, but also some bacteria can use photosynthesis to make food. This was extremely important because it now helps astronauts use algae to produce oxygen in their spaceships. He then worked for NASA in the 60s on finding Extra Terrestrial life and also on technology that could take soil samples from Mars.

Not only that, but he also figured out that you can use chemicals produced by fireflies, to detect something called ATP, which is basically used for energy by every living thing. So his method can be used to detect any kind of life. He was commended for his work by being inducted into the National Inventors Hall of Fame. Emmett Chapelle's work has led to the advancement of society in so many ways. So he deserves to be recognized. If you want to learn more about Dr. Chappelle, or this year In general, check out onwildlife.org.

Okay, welcome back. So why are these Zooxanthellae so important? Well, they get a place to live and in return, the corals get food and energy. This will be important when we're talking about coral bleaching.

Zooxanthellae are autotrophs, meaning that they perform photosynthesis in order to make their own food. And once these algae make their energy, they transfer some of that energy to the corals. And corals can also catch their own prey. They have venomous barbed tentacles that they stick out to capture plankton and even some small fish. And this is really similar to what a jellyfish does for food.

Coral is shaped like a cylinder with a mouth at one end, usually facing the sun and the tentacles that they use to catch their prey surround the mouth. Now you might be wondering how they digest their food. Well, they don't have a complex digestive system like we do with a small intestine, large intestine and stomach.

They just have one big body cavity where all the food is taken in. inside the body cavity are these folds called Mesenteries that helped to digest the food. But where's all that waste come out once it's digested, it leaves the same way and enters they only have one opening so their mouth is also their anus.

Coral reproduce both sexually and asexually. Asexual reproduction occurs when the polyp grows to a certain size and then divides. This happens throughout the corals entire life. They can also go through a process called budding or fragmentation, where a piece of the parent coral falls off, and then that piece becomes a new organism. It's kind of like if we grew a third arm, it fell off of our body and then it became a clone of ourselves.

Sexual reproduction is a little more complicated. Corals release a massive number of eggs and sperm into the water to be able to distribute their offspring all over. And once the egg and the sperm are released, they meet together and become Planula, which is the larval stage, and they're basically plankton.

There are an extremely large amount of these Planula that are produced, and they all swim to the surface of the ocean because they're attracted to the light. And after this, they sink back down to the sea floor where they can develop into adults. The large number of Planula make up for the fact that most of them get eaten before they even become adults.

In many reefs, when the sperm and the egg are released, it occurs as a mass event. And the timing of the release is actually really important. And it has to be all at the exact same time because corals can't move to be in contact with each other. This is called spawning. Spawning can be in response to a variety of different environmental factors like change in temperature or the length of the day.

Lunar cues or cues from the moon control when corals get ready to spawn, and the time of the sunset controls when they actually do spawn. Refielding corals come in a variety of shapes and sizes. Each coral fits some kind of niche in the ecosystem.

Massive corals, which is the actual name of the species could be as small as an egg, or as large as a house and are round and ball shaped. But then there are other corals like table corals, which form a table like structure and brain corals, which you guessed it look like a brain. There are even some corals like fire coral that exhibit some traits of its cousin, the jellyfish. They have stinging cells called Nomad assists that inject venom into you if you touch them, causing a burning sensation.

Reefs begin to grow as the Planula settle onto a hard surface on the edge of islands or continents. The corals then grow and expand into three major structures fringing barrier or atoll. Fringing reefs are the most common. They formed directly offshore along shorelines like off the southern coast of Florida.

Barrier reefs are similar to fringing, but they grow further away from the shore. They're separated from land typically by deeper waters. An example of this is the most famous and largest coral reef in the world, the Great Barrier Reef, these reef spans over 130,000 square miles. That's more square miles than the entire state of New Mexico.

The final reef, an atoll, is the most uncommon kind of reef. This happens when a fringe reef forms around a volcanic island, which then completely sinks below sea level, but the coral continues to grow upward.

Atolls are usually circular or oval with a lagoon in the middle barrier and atoll reefs are some of the oldest reefs on the planet. And depending on their size, they can take 100,000 to 300,000 years to fully form. Okay, we're gonna take a break for the trivia question, but when we get back, I'm going to talk about coral bleaching One of the largest issues that corals are facing today.

Time for the trivia question, how many different beetle species are there in the world?

A: 35, B: 350, C: 35,000, or D: 350,000?

The answer is D. There are 350,000 different species of beetles in the world.

Alright, welcome back. So there is one extreme issue that corals are facing. And it's due to the fact that we're putting massive amounts of carbon dioxide into the atmosphere. The first problem with this is that it's causing a greenhouse effect, where the carbon dioxide that's in the atmosphere is trapping heat from the sun in the earth. This is not only causing the overall climate to start being warmer, but it's also warming our oceans.

The other problem for corals specifically is that a lot of the carbon dioxide that we release into the atmosphere actually gets absorbed by the ocean. And this is making the ocean more and more acidic.

So what are the problems with these things? Corals under these conditions, release and evict, their Zooxanthellae that live inside of them, causing the coral to turn white. And this process is called coral bleaching. And as you'll remember, corals get the majority of their food and energy from these Zooxanthellae. So now they're not getting what they need to survive.

The coral doesn't die from this instantly, and it can even survive a bleaching event, but only if the stress is alleviated. If it's not relieved, coral bleaching will kill entire colonies.

And when I took a research trip to Panama, I saw this bleaching firsthand in the oceans. Some of the coral was still colorful, but in a lot of other areas, all I could see was white dead coral lying on the sea floor. It's really not a great sight to see.

In 2005, a massive bleaching event occurred in the Caribbean, where half of the corals died. What caused this was warmer waters around the northern Antilles, which is near the Virgin Islands flowing south, this stress was greater than the previous 20 years combined.

And since the 90s, about half of the Great Barrier Reef has been lost to coral bleaching. However, not all bleaching events are caused by warm water in 2010. Cold water in the Florida Keys cause bleaching that made corals die. The water temperature dropped about 12 degrees Fahrenheit from the average.

Currently, there are two ways that scientists are trying to save coral. The first way is to do what's called assisted evolution. They take genes from different coral that are able to survive bleaching events, and in the lab ensure they're breeding with each other.

This increases the likelihood that they'll survive the bleaching events. After the polyps are settled onto portable surfaces. Scientists then take them into the ocean to see how they do outside of a laboratory setting.

The second way is to change the algae in which the coral has a symbiotic relationship with Zooxanthellae are expelled when the environment becomes stressful. But what if there's an algae that's able to handle more stress? Well, there is scientists have found that some corals switch algae for more heat resistant ones that would allow the coral to live until 2100.

Even though corals cover less than 1% of the ocean floor, they hold 25% of all biodiversity and are one of the most biodiverse ecosystems on the planet. The reefs provide shelter, spawning grounds, protection and support for all types of organisms. And millions of people rely on coral reefs for fishing. Removing corals is almost like removing trees from a land ecosystem because so many organisms call coral reefs their home.

Reefs also draw a lot of tourism which helps local economies. And not only that, but these reefs protects humans as well. About 40% of the world's population lives 60 miles or less from a coast. So these coral reefs provide a barrier for storm surges, hurricanes and tsunamis that keep coastal communities safe. And without them, we would have to rely on manmade storm walls, which are expensive, less effective and damage the environment.

So what can we do to help? Well, there's a lot of small daily actions that will really help coral reefs if we do them. First of all, we can reduce our fertilizer use. We can also avoid herbicides and pesticides, and we can reduce the amount of energy that we use. But we must address climate change in order to truly solve coral bleaching, scientists can delay the extinction, but we need to greatly reduce our carbon emissions.

And aside from all this, you can also check out some awesome organizations that are helping corals right now, like the Coral Reef Alliance, the Coral Restoration Foundation and Save the Reef.

Thank you so much for coming on this adventure with me. As we explored the world of corals. You can find the sources that we use for this podcast and links to organizations that we reference at on wildlife.org. You can also email us with any questions at onwildlife.podcast@gmail.com.

And you can also follow us on Instagram @on_wildlife or on TikTok @onwildlife. And I would really appreciate it if you could go fill out that survey that I told you about at the beginning of the episode. Don't forget to tune in next Wednesday to hear about another awesome animal and that's On Wildlife.

Jess Avellino

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Transcribed by https://otter.ai