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Outforia Quicktake: Key Takeaways

1. Coral is an essential part of ocean ecosystems, supporting a large percentage of marine life and protecting coastal areas.

2. Coral bleaching occurs when corals become stressed and expel the microorganisms that provide them with nutrients, increasing their risk of death.

3. There are over 6,000 species of coral, classified into two main subclasses: Hexacorallia (stony corals) and Octocorallia (soft corals).

4. Coral reefs are some of the most biodiverse places on Earth, and their loss could have severe consequences for coastal communities and industries such as tourism and fishing.

5. Coral is also a source of natural compounds used in medical treatments, making it an important resource for human health.

Whether you're a keen scuba diver or simply an ocean lover, chances are pretty high that you've marveled at the wonders of the world's colorful coral reefs at some point in your life.

But, how much do you really know about coral?

It turns out that, in addition to looking really cool, coral is also one of the most fascinating creatures on the planet. In fact, there are thousands of species of coral in the world, each of which plays its own role in supporting the greater ocean ecosystem.

If you've ever wanted to learn more about coral, then this article is for you. Up next, we'll introduce you to the 22 most incredible types of coral. That way, you can impress your friends with your knowledge and be a better steward of our world's oceans.

The 22 Out-of-this-World Types Of Coral

There are well over 6,000 different types of coral on this planet, so we couldn't possibly talk about them all here. But, to help you learn more about these fascinating animals, we've created this list of the top 22 coolest types of coral on Earth. Here's what you need to know:

1. Elkhorn Coral (Acropora palmata)

First up on our list is the elkhorn coral, which is one of the most widely distributed corals in the Caribbean Sea. It can grow to be up to 12 feet (3.7 m) long and 6 feet (1.8 m) high, so it's truly a wonder to behold if you get to dive near any elkhorn coral reefs.

The elkhorn coral likes to grow in large groups called thickets, which are normally found in shallow waters. Due to its large size, it often provides an essential habitat for other types of marine animals such as the Caribbean Reef Octopus.

However, the species is currently threatened throughout its range due to a number of factors, including the white band disease.

The white band disease kills the elkhorn coral's tissues. In conjunction with climate change, pollution, and unsustainable fishing pressure, the white band disease has killed about 97% of the world's elkhorn coral population. Thankfully, there are a number of organizations that work to protect elkhorn coral reefs from further damage.

2. Open Brain Coral (Trachyphyllia geoffroyi)

A highly popular coral species for use in home fish tanks, the open brain coral is a type of coral that has an odd-looking figure-eight shape and plenty of superb colors. In fact, as they get older, open brain corals can develop into a slew of different fluorescent colors, which is why they're so popular among home reef aquarists.

These corals are naturally found in a wide range of different locations in the Indo-Pacific oceans, though they tend to prefer sandy and muddy seafloors. In particular, they are mostly found from New Caledonia to the Red Sea and they prefer water that's less than 130 ft (40 m) deep.

Open brain corals are also prone to bleaching in the wild, which is one of the reasons why they're listed as near threatened on a global level. However, over-harvesting for the aquarium trade is easily the coral's biggest threat in the long term.

3. Bubble Coral (Plerogyra sinuosa)

Boasting a spectacular bubble-like pattern, the bubble coral is an instantly recognizable coral that's popular among reef aquarists. It has bubble-shaped tentacles that can actually expand and contract depending on the coral's feeding schedule.

They are naturally found throughout the Indo-Pacific oceans from about the Red Sea to the Line Islands.

Interestingly, these corals live in a symbiotic relationship with some dinoflagellates (single-cell eukaryotes). These tiny dinoflagellates are able to photosynthesize, which provides the bubble coral with most of its necessary nutrition.

Nevertheless, like most corals, even the widely distributed bubble coral is listed as near threatened. Its biggest threat is climate change.

4. Staghorn Coral (Acropora cervicornis)

Similar to the elkhorn coral, staghorn coral is another important species in the Caribbean. The staghorn coral has more of a tubular shape than the elkhorn coral, making it appear more like the horns of an adult male deer.

Staghorn corals also grow in large thickets, which can be important habitats for fish. They tend to have branches that are a few inches thick but a single colony can be up to about 4 feet (1.2 m) high. They are normally found in shallow water in the Caribbean, as well as around the Bahamas and Florida.

Unfortunately, like elkhorn coral, staghorn coral has also been decimated by white band disease over the last few decades. Staghorn coral is less responsive to human interventions like dedicated breeding programs, however, so its populations are still on the decline.

5. Leaf Coral (Pavona decussata)

A rugged-looking type of colonial stony coral, the leaf coral is an animal that's found in the shallow waters of the Indo-Pacific. Aptly named, it usually forms a leaf-like shape that's only about 3 to 10 millimeters thick.

Leaf corals are widely distributed throughout the Indo-Pacific, however, relatively little is known about its overall population. Most leaf corals live no further than about 50 ft (15 m) in depth and they prefer to live on sloping surfaces.

It's believed that the leaf coral is at risk of widespread bleaching, however, and it is listed as vulnerable by the IUCN.

6. Vase Coral (Montipora capricornis)

Also called Monti, after its Latin name, vase coral is a highly popular type of coral among home aquarists.

It is naturally found throughout the Indo-Pacific, especially in the Red Sea. For the most part, it prefers to live in the upper portion of the reef where the water is warmer.

Vase coral is a common sight in aquariums because it tends to tolerate captivity quite well. In fact, while it has multiple polyps, like all other corals, vase coral has a symbiotic relationship with zooxanthellae, which are single-celled dinoflagellates that perform photosynthesis.

So, when given enough sunlight, most vase coral can survive off the zooxanthellae's photosynthesis alone.

7. Venus Sea Fan Coral (Gorgonia flabellum)

One of the best-known types of soft coral, the Venus sea fan tends to form massive fan-like structures that grow vertically upward from the ocean floor.

As a soft coral, it does not produce a hard shell of calcium carbonate. However, the Venus sea fan coral can hold itself upright in the current, growing to a height of about 6.6 ft (2 m) with relative ease.

The Venus sea fan coral is found throughout the Caribbean, though it is also very common in the Bahamas. They have a number of coral polyps on their tentacles that can filter feed for plankton that float through the current. However, the Venus sea fan's symbiotic relationship with dinoflagellates provides it with much of its photosynthesized nutrition.

8. Sun Corals (Tubastraea)

Sun corals are not one, but a whole genus of different cup corals that are found throughout the Caribbean. They are known to inhabit waters as far north as the Florida Keys, but they prefer deep waters, particularly around shipwrecks.

Since sun corals don't rely on photosynthetic microorganisms for their sustenance, they're actually one of the easier corals to care for in captivity.

They can eat surprisingly large food, such as mysis shrimp. However, since their polyps only open at night, they have to be fed during the nighttime hours. Who knew?

9. Lettuce Coral (Agaricia agaricites)

One of the more common corals of the Atlantic Ocean and the Caribbean, lettuce coral is, as you might've guessed, a type of coral with a distinctive lettuce-like appearance.

Lettuce coral can be found throughout the Gulf of Mexico and the Caribbean as well as near a number of atolls off the coast of Brazil. It prefers seagrass meadows, lagoons, and other fairly deep depths of down to 245 ft (75 m).

As it is the dominant species of coral in much of its range, the lettuce coral is one of the few coral species in the world that's listed as a species of least concern. However, it is susceptible to bleaching, especially when El Niño events cause rising ocean temperatures in the region.

10. Organ Pipe Coral (Tubipora musica)

Organ pipe coral is a type of soft coral that's found throughout the central and western Pacific.

Interestingly, despite being classified as a soft coral, organ pipe coral does have a hard skeleton of calcium carbonate. It is known for its long polyps, which tend to look a lot like organ pipes.

When organ pipe coral dies, it often leaves behind a skeleton of calcium carbonate. This skeleton can be bright red, which makes it particularly attractive to scuba divers who come across it.

That being said, the organ pipe coral can be quite difficult to care for, so it's not a great species to keep in an aquarium. But, if you come across it while diving, it's sure to be an awesome experience.

11. Grooved Brain Coral (Diploria labrynthiformis)

Aptly named, the grooved brain coral looks strikingly like a human brain. It boasts a set of deep grooves that look a whole lot like the folds of the human brain and it often has a grey coloration which only adds to its brain-like appearance.

Groove brain corals can grow to be about 6 feet (1.8 m) in diameter. They usually take on a circular shape but, while it might look like there is just one giant groove brain coral, these animals like to grow in groups of multiple individuals. So, what you see as a single specimen is often a small colony.

Thankfully, while the grooved brain coral is susceptible to bleaching and disease, it seems to be fairly resilient. Furthermore, it is still somewhat common throughout its range and the IUCN lists the grooved brain coral as a species of least concern.

12. Boulder Star Coral (Monstastrea annularis/Orbicella annularis)

Most commonly known as the boulder star coral, this species of coral is found in the western Atlantic, particularly around the Caribbean. It is one of the more abundant reef-building corals within its range and it can be found throughout the region down to a depth of about 260 ft (80 m).

The boulder star coral tends to form small boulder-shape structures with dozens of individual polyps. They are often found in colonies that look like piles of green or yellowish rocks, which can help with identification while diving.

That being said, the boulder star coral is currently listed as endangered due to the effects of climate change.

13. Great Star Coral (Montastraea cavernosa)

Similar to the boulder star coral, the great star coral is another animal that tends to form large, rock-shaped colonies. It is a type of stony coral that has a symbiotic relationship with zooxanthellae that provide it with the majority of its nutrition.

Most great star corals will form massive domes that look green, red, or brown in color. However, there are actually two morphs of this species, diurnal and nocturnal. So, the diurnal morphs, which tend to be brown, have polyps that expand and feed during the day and night. The nocturnal morph is usually brightly colored and it expands only at night to feed.

These corals are found mostly around Trinidad and Tobago, though you can find them around the Caribbean and the Gulf of Mexico. It is also occasionally spotted along the coast of western Africa.

14. Clubbed Finger Coral (Porites porites)

One of the smaller species of coral in our list, the clubbed finger coral is found in the Caribbean and in some parts of western Africa.

As you can guess from its name, the clubbed finger coral has small lobes that look a lot like thick fingers. These lobes usually aren't more than about 1 inch (2.5 cm) wide and they tend to be white or blueish-grey in color.

Some clubbed finger corals can live impressively long lives. Although more research is being done to learn more about this species, it's possible that an individual can live for many centuries.

Furthermore, the clubbed finger coral is one of the few corals that's not currently at risk of extinction. It has a fairly widespread distribution, though some populations, particularly around the US Virgin Islands have been damaged by bleaching and disease in recent years.

15. Smooth Cauliflower Coral (Stylophora pistillata)

Thought that corals spend their lives in one place? Think again!

The smooth cauliflower coral actually likes to travel around quite a bit, thanks to its tendency to attach itself to floating objects, like shipwreck debris. Then, as these objects drift around in the ocean, the smooth cauliflower coral goes along for the ride. Who would've known?

However, the smooth cauliflower coral isn't only known for its globetrotting tendencies. It also grows into a cauliflower-like shape with colorful, rounded branches. They're usually found in the Indo-Pacific and you can find them at a wide range of depths in the ocean.

16. Massive Starlet Coral (Siderastrea siderea)

Massive starlet corals tend to grow into large dome-shaped structures that are composed of dozens of smaller individual corals. These corals often have a dimpled surface that makes them look a bit like an oversized golf ball.

They are usually found in the western hemisphere, particularly near Bermuda, the Bahamas, and other parts of the Caribbean.

These corals can be found at depths of up to about 230 ft (70 m). In fact, they really don't like living in high-silt environments, like tide pools, so they'll either grow in well-lit shallow waters or in the depths of the ocean.

17. Honeycomb Coral (Diploastrea heliopora)

Forming beautiful honeycomb-esque colonies, the honeycomb coral is a widespread type of coral that's found throughout the Indo-Pacific. It is particularly common around the Red Sea where it can be found at depths of up to 100 ft (30 m).

These corals like to form large colonies which can be up to 16 ft (5 m) wide. Sometimes, they can form dome shapes, but they often turn into large sphere-like boulders.

Honeycomb corals are unfortunately listed as near threatened by the IUCN. Their major threats include pollution and climate change, though trampling by visitors to coral reefs is also a major issue for the honeycomb coral's survival.

18. Finger Coral (Montipora digitata)

Although it shares a similar common name to the clubbed finger coral, the finger coral is a completely separate species. It is a type of stony coral that's mostly found in eastern Africa, particularly around Mozambique.

This coral forms small bush-like structures with large, finger-esque branches. Nevertheless, unlike many of its neighboring corals, the finger coral seems relatively unaffected by bleaching. While climate change is an issue, the finger coral seems to resist bleaching damage and it is considered a species of least concern.

19. Common Mushroom Coral (Fungia fungites)

One of the more recognizable stony corals, the common mushroom coral is a relatively small animal found in the coral reefs of Hawai'i.

The common mushroom coral forms small oval shapes that look a whole lot like your standard wild mushroom. They prefer to live in mostly quiet reefs with relatively little activity. In fact, they don't form colonies like many of the other corals in Hawai'i.

Furthermore, the common mushroom coral will only attach itself to a reef for the early part of its life. When it gets larger, it will break free from the reef and live on its own on the seafloor.

20. Precious Coral (Corallium)

A popular source of coral material for jewelry and other manufactured goods, precious coral refers to the species within the genus Corallium.

There are about 31 species of precious coral on Earth, most of which like on rocky seafloors. They can actually be found in the Mediterranean, too, which isn't common. In fact, you can find them around Sardinia and the Strait of Gibraltar, though they are also found near Japan and Taiwan.

What makes these corals special, however, is that they leave behind a hard skeleton of calcium carbonate when they die. These skeletons are often red in color, which makes them popular as a raw material among jewelry makers.

21. Carnation Coral (Dendronephthya)

Often known as the carnation corals, all of the species within the genus Dendronephthya feature funky tree-like structures that make them a popular choice for home aquarists.

The carnation corals come in many different shapes and colors as there are dozens of species within the genus. They are mostly found in the tropical waters of the Indo-Pacific, especially in the Red Sea.

That being said, while carnation corals are popular among home aquarists, they are not easy to care for. Unlike most other corals, the carnation coral feeds only on phytoplankton so it needs a constant source of food in order to survive.

22. Colorful Sea Whip (Leptogorgia virgulata)

Last but not least, the colorful sea whip is a type of colonial soft coral that lives along the western coast of the Atlantic Ocean. In fact, it can be found as far north as the Chesapeake Bay and as far south as Brazil.

These corals have long, branch-like arms that can grow into massive structures, though the majority of colorful sea whips are no more than about 24 inches (60 cm) tall.

The colorful sea whip serves as a very important habitat for a number of other species, including the Atlantic wing oyster and a few different types of shrimp. Despite this, it is often damaged by shrimp trawling nets, which can wipe out large portions of the population.

How Corals Are Classified

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With over 6,000 species of coral in the world, scientists have had a tricky time trying to categorize and classify all the different coral species.

All corals belong to the kingdom Animalia (yep, corals are animals!), the phylum Cnidaria, and the class Anthozoa. Beyond the class Anthozoa, however, things get a little hectic.

The class Anthozoa is technically subdivided into 3 subclasses. This includes:

Subclass Hexacorallia - The subclass Hexacorallia includes the order Scleractinia, which is all of the stony corals.

Subclass Octocorallia - The Subclass Octocorallia is home to the order Alcyonacea, which contains the soft corals.

Subclass Ceriantharia - The subclass Ceriantharia is actually not a type of coral. This subclass includes the sea anemones, which, while related to coral, do not have a skeleton-type structure. Rather, anemones are filled with fluid while corals have an exoskeleton on each polyp.

Since sea anemones aren't technically corals, we won't focus on them here. But, in this section, we'll give you a quick look at the world of coral taxonomy to help you better understand these fascinating creatures.

1. Subclass Hexacorallia (Stony Corals)

The first subclass of coral that we'll discuss is the subclass Hexacorallia. This subclass is also known as the stony corals because many of them have a calcite exoskeleton that makes them appear hard and stone-like.

The real difference between the stony corals and the soft corals, however, is their shape.

Stony corals have body segments with fewer than 6 axes of symmetry. This might seem like a pretty arbitrary distinction, but that's what the taxonomists decided, so we all simply have to follow suit. That being said, soft corals usually have simple, unbranched body structures with more than 8 tentacles. So, they're often easy to distinguish from stony corals.

Within the subclass Hexacorallia, there are 35 families. However, there are thousands of species and not all have actually been classified in a species so there are many stony corals that scientists don't know much about.

Stony corals are also very difficult to classify due to their great diversity. Some of the major families in this subclass include:

Acroporidae

Agariciidae

Astrocoeniidae

Caryophylliidae

Dendrophylliidae

Euphylliidae

Faviidae

Flabellidae

Fungiidae

Merulinidae

Micrabaciidae

Montastraeidae

Oculinidae

Pocilloporidae

Poritidae

Rhizangiidae

Turbinoliidae

Mussidae

2. Subclass Octocorallia (Soft Corals)

The subclass Octocorallia contains some 3,000 different species of soft corals. These corals usually have at least an 8-fold symmetry, so they include species that are commonly referred to as the gorgonians, the sea pens, and the blue coral.

As we've mentioned, the soft corals usually don't have a very well-developed exoskeleton like the stony coral. Though, the real defining feature is that they tend to have longer, unbranched tentacles.

Like with all things coral-related, though, the taxonomy of the soft corals below the subclass level is complex. There are 6 orders and more than 40 families of soft corals, but, like the stony corals, some species have not yet been classified. Some of the major families include:

Alcyoniidae

Nephtheidae

Xeniidae

Chrysogorgiidae

Ellisellidae

Isididae

Primnoidae

Gorgoniidae

Plexauridae

Taiaroidae

Anthothelidae

Coralliidae

Melithaeidae

Paragorgiidae

Parisididae

Subergorgiidae

Clavulariidae

Tubiporidae

What Is Coral Bleaching?

If you're interested in corals, at some point, you've probably heard people talking about coral bleaching. But, what is coral bleaching, you might ask?

Essentially, coral bleaching is a process that happens when coral gets stressed out. Of course, coral doesn't get stressed out by its math homework like we humans might, but it does become stressed out when there are major changes in its environment.

For example, when a coral's habitat starts to get much warmer or much colder than it normally is, the coral starts to get a bit nervous. Eventually, if these extreme temperatures continue for too long, the coral will physically expel the microorganisms that live on its surface in a process known as bleaching.

This might not seem like a big deal, but these microorganisms provide most coral species with vital nutrients through photosynthesis. So, when the coral expels these microorganisms, it has less access to sustenance that it needs to survive.

The process of bleaching usually turns coral white due to its lack of food and the lack of algae living in their tissues. While bleaching on its own won't kill coral, it does greatly increase the coral's risk of death.

If the conditions that led to the bleaching (e.g., warm water, lots of pollution, or extreme low tides) continue, the coral is at a much higher risk of death. As a result, long-term bleaching events can completely wipe out sections of a coral reef.

Coral Fun Facts

Fancy yourself as a veritable coral expert? Here are some coral fun facts that you ought to know:

1|Coral is the Medicine Cabinet of the Ocean

While most people think of medicine as something that's artificially created in a lab somewhere, most medicine is actually derived from natural compounds.

In fact, many medicines are derived from various coral species.

How? Well, some coral species have unique compounds that aren't found in any other life form. That's because corals have had to develop their own chemical defense systems over the millennia to protect them from predators.

As a result, we humans can often use these chemicals to create medication for a wide range of diseases. So, if you ever do have to take medication when you're feeling ill, you likely have coral to thank.

2|25% of the World's Marine Life Depends on Coral

While most marine species don't live in coral reefs, about one-fourth of all marine life does live in a coral reef for some part of its life cycle. Indeed, the secure, sheltered environment created by coral reefs makes it the perfect place for small organisms to grow before they're ready to swim into the great blue beyond.

3|The Great Barrier Reef is Visible From Space

Yep, that's right-astronauts can see the Great Barrier Reef from space!

Okay, they can't see the individual corals in the reef, but there are some superb images of the outline of the Great Barrier Reef that have been taken by satellites. Some of the best photos of the reef were taken back in 2004 by the Envisat satellite, which used a spatial resolution of 980 ft (300 m) to create the images we see today. That's pretty darn cool, if you ask us!

Coral FAQs

Here are our answers to some of your most commonly asked questions about coral:

You may also like:

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A Colorful Exploration: 22 Types of Coral and Their Beauty

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Outforia Quicktake: Key Takeaways Coral is an essential part of ocean ecosystems, supporting a large percentage of marine life and protecting coastal areas. Coral bleaching occurs when corals become stressed and expel the microorganisms that provide them with nutrients, increasing their risk of death.

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There were startling colours here just a year ago, a dazzling array of life beneath the waves. Now this Maldivian reef is dead, killed by the stress of rising ocean temperatures. What's left is a haunting expanse of grey, a scene repeated in reefs across the globe in what has fast become a full-blown ecological catastrophe.

The world has lost roughly half its coral reefs in the last 30 years. Scientists are now scrambling to ensure that at least a fraction of these unique ecosystems survives beyond the next three decades. The health of the planet depends on it: Coral reefs support a quarter of all marine species, as well as half a billion people around the world.

"This isn't something that's going to happen 100 years from now. We're losing them right now," said marine biologist Julia Baum of Canada's University of Victoria. "We're losing them really quickly, much more quickly than I think any of us ever could have imagined."

Even if the world could halt global warming now, scientists still expect that more than 90 percent of corals will die by 2050. Without drastic intervention, we risk losing them all.

"To lose coral reefs is to fundamentally undermine the health of a very large proportion of the human race," said Ruth Gates, director of the Hawaii Institute of Marine Biology.

Coral reefs produce some of the oxygen we breathe. Often described as underwater rainforests, they populate a tiny fraction of the ocean but provide habitats for one in four marine species. Reefs also form crucial barriers protecting coastlines from the full force of storms.

They provide billions of dollars in revenue from tourism, fishing and other commerce, and are used in medical research for cures to diseases including cancer, arthritis and bacterial or viral infections.

"Whether you're living in North America or Europe or Australia, you should be concerned," said biologist Ove Hoegh-Guldberg, director of the Global Change Institute at Australia's University of Queensland. "This is not just some distant dive destination, a holiday destination. This is the fabric of the ecosystem that supports us."

And that fabric is being torn apart.

"You couldn't be more dumb... to erode the very thing that life depends on - the ecosystem - and hope that you'll get away with it," Hoegh-Guldberg said.

Corals are invertebrates, living mostly in tropical waters. They secrete calcium carbonate to build protective skeletons that grow and take on impressive colours, thanks to a symbiotic relationship with algae that live in their tissues and provide them with energy.

But corals are sensitive to temperature fluctuations, and are suffering from rising ocean temperatures and acidification, as well as from over-fishing, pollution, coastal development and agricultural runoff.

A temperature change of just 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit) can force coral to expel the algae, leaving their white skeletons visible in a process known as " bleaching."

Bleached coral can recover if the water cools, but if high temperatures persist for months, the coral will die. Eventually the reef will degrade, leaving fish without habitats and coastlines less protected from storm surges.

The first global bleaching event occurred in 1998, when 16 percent of corals died. The problem spiralled dramatically in 2015-2016 amid an extended El Nino natural weather phenomenon that warmed Pacific waters near the equator and triggered the most widespread bleaching ever documented. This third global bleaching event, as it is known, continues today even after El Nino ended.

Headlines have focused on damage to Australia's famed Great Barrier Reef, but other reefs have fared just as badly or worse across the world, from Japan to Hawaii to Florida.

Around the islands of the Maldives, an idyllic Indian Ocean tourism destination, some 73 percent of surveyed reefs suffered bleaching between March and May 2016, according to the country's Marine Research Center.

"This bleaching episode seems to have impacted the entire Maldives, but the severity of bleaching varies" between reefs, according to local conditions, said Nizam Ibrahim, the centre's senior research officer.

Worst hit have been areas in the central Pacific, where the University of Victoria's Baum has been conducting research on Kiritimati, or Christmas Island, in the Republic of Kiribati. Warmer water temperatures lasted there for 10 months in 2015-2016, killing a staggering 90 percent of the reef.

Baum had never seen anything like it.

"As scientists, we were all on brand new territory," Baum said, "as were the corals in terms of the thermal stress they were subjected to."

To make matters worse, scientists are predicting another wave of elevated ocean temperatures starting next month.

"The models indicate that we will see the return of bleaching in the South Pacific soon, along with a possibility of bleaching in both the eastern and western parts of the Indian Ocean," said Mark Eakin, coral reef specialist and coordinator of the National Oceanic and Atmospheric Administration's Coral Reef Watch, which uses satellites to monitor environmental conditions around reefs. It may not be as bad as last year, but could further stress "reefs that are still hurting from the last two years."

The speed of the destruction is what alarms scientists and conservationists, as damaged coral might not have time to recover before it is hit again by warmer temperatures.

But some may have a chance.

Last month, Hoegh-Guldberg helped launch an initiative called 50 Reefs, aiming to identify those reefs with the best chance of survival in warming oceans and raise public awareness. His project partner is Richard Vevers, who heads the XL Caitlin Seaview Survey, which has been documenting coral reefs worldwide.

"For the reefs that are least vulnerable to climate change, the key will be to protect them from all the other issues they are facing - pollution, over-fishing, coastal development," said Vevers, who founded The Ocean Agency, an Australian organisation seeking new technologies to help mitigate some of the ocean's greatest challenges. If the reefs remain healthy and resilient, "they can hopefully become the vital seed-centres that can repopulate surrounding reefs."

Nature itself is providing small glimmers of hope. Some of Kiritimati's corals, for example, are showing tentative signs of a comeback.

But scientists don't want to leave it to chance, and are racing ahead with experiments they hope might stave off extinction.

"We've lost 50 percent of the reefs, but that means we still have 50 percent left," said Gates, who is working in Hawaii to breed corals that can better withstand increasing temperatures. "We definitely don't want to get to the point where we don't intervene until we have 2 percent left."

Going a step further, she is also trying to "train" corals to survive rising temperatures, exposing them to sub-lethal heat stress in the hope they can "somehow fix that in their memory" and survive similar stress in the future.

"It's probably time that we start thinking outside the box," Gates said. "It's sort of a no-win game if we do nothing."

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More than 90 percent of coral reefs will die out by 2050

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Earth has already lost half of its 'underwater rainforests' over last 30 years

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- Soft corals: These corals have flexible skeletons and often form large colonies with branching shapes. They include leather corals, sea fans, and sea whips.

- Stony corals: These corals have hard, calcium carbonate skeletons and are the main builders of coral reefs. They include brain corals, star corals, and elkhorn corals.

- Gorgonians: These corals are a subgroup of soft corals that have a central axis of support. They are often fan-shaped or tree-like and sway with the water currents. They include sea fans, sea whips, and sea rods.

- Zoanthids: These corals are small, colorful polyps that form mats or clusters on rocks or other surfaces. They have a symbiotic relationship with algae that provide them with nutrients and color.

- Mushrooms: These corals are soft-bodied polyps that resemble mushrooms or anemones. They can be solitary or colonial and come in various colors and patterns. They can reproduce by budding or splitting.

- Deep-sea corals: These corals live in cold, dark waters below the reach of sunlight. They do not have symbiotic algae and rely on capturing food from the water. They include black corals, bamboo corals, and bubblegum corals.

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Tropical Snorkeling - Destinations, Equipment & Safety Tips

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This page will help you tell the difference between what live vs dead coral looks like. With rising ocean temperatures, damage from tourism, and overfishing, it's estimated that 25%-50% of the world's corals reefs are already dead, up to 75% have suffered bleaching events, with the remainder at risk. Finding a live healthy coral reef is actually becoming rare.

Many people have their first snorkeling experience at popular tourist locations like Hanauma Bay, Oahu in Hawaii, or Trunk Bay in St. John. Since most of the coral at these locations is dead many new snorkelers may not realize what they are missing, or what live vs dead coral looks like.

Coral Looks Like a Stone or Plant, But It Is a Colony of Animals

Coral is like the forest of the sea, except it is not a plant, it is a colony of animals (called polyps).

These little animals live in a symbiotic relationship with algae, and they build tiny calcium stone houses for themselves. And all of these houses get stacked on top of each other and form larger structures like apartment buildings or termite hills. These can take many different shapes that might look like hard rock boulders, or branches. They can also form flexible structures that can move with the currents of water. In the closeup picture you can see the structure of their calcium houses. The animals are withdrawn inside. Many corals only come out at night to feed, although there are some exceptions.

For example the first picture below is a leather coral (partially bleached), and the animals are mostly retracted. The next picture shows the animals out feeding.

Here is an excellent article that explains coral animals.

It's sometimes hard to think of corals as animals, but they are. They often feed on zooplankton that they pull inside and digest in stomachs. Aquarium owners often feed their corals with brine shrimp.

What Live Vs Dead Coral Looks Like

Check out the pictures below. These are just a few samples of some common corals that can be seen in the Pacific and Atlantic Oceans.

Compare what live vs dead coral looks like. Look at the color and shape. Old dead corals will be broken down, and lack a healthy color, and are sometimes covered in algae.

Corals that have been bleached from rising ocean temperatures turn white when the symbiotic algae leaves the coral. In some rare circumstances these may recover if the algae returns.

Are you finding this live vs dead coral page educational? We share lots of tips like this in our free monthly newsletter.

Dead or Dying Elkhorn Coral

Live Elkhorn Coral

Dead, Unhealthy, or Damaged Brain Coral

Live Brain Coral

Unhealthy Sea Fan Corals

Only the center purple fan looks relatively healthy in the picture below. Soft corals like these also have tiny polyps that feed on microorganisms in the water.

Live Sea Fan Coral

Dead Staghorn Coral

Live Staghorn Coral

Bleached Table Coral, Soon to Be Dead

Mix of Live and Bleaching Table Corals

Bleaching Boulder Coral

Live Boulder Coral

Live vs Dead Coral - Cauliflower Side by Side

Algae Sometimes Takes Over a Dead Reef

When you are trying to see if something is live vs dead coral, one way to tell is that dead coral often becomes covered in algae like in the picture below.

Corals Are Critical for Healthy Oceans

Corals clean the oceans, provide habitat, and are food to countless other species. And we are seeing a global mass extinction on a scale that is terrifying for not only ocean health, but human fisheries. Without coral reefs, human jobs and food sources are rapidly declining.

So the next time you are out snorkeling, and see some beautiful fish, like in the pictures below, make sure and look behind at the coral, and take note of its condition. The corals are 95% dead in the two pictures below. Without corals, you can expect the ocean's entire ecosystem to be stressed and declining.

What Can You Do?

Helping prevent the continued destruction of coral reefs is pretty easy, on a personal level at least.

1. Learn to recognize the live vs dead coral on the reef.

2. Only use sunscreens that don't kill reefs, or wear a full body rash guard.

3. Don't touch or kick coral, use good reef etiquette.

4. Fight the human causes of global warming any way you feel you can. Support an ocean charity and vote for good policies.

More Snorkeling Tips

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Live Vs Dead Coral - Useful Pictures And Descriptions

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Learn how to identify live vs dead corals. See pictures and descriptions, including what coral bleaching looks like.

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What is the current status of coral?(yimeng)

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What is the current status of coral?(yimeng)

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/ Posted in CORAL Updates

We recently held our annual State of the Reef Address, which highlighted the urgent need for action to protect coral reefs. Heather Starck, the Executive Director of the Coral Reef Alliance, emphasized the devastating impact of climate change, overfishing, pollution, and other human activities on coral reefs around the world. Coral reefs are critical ecosystems that provide food and livelihoods for millions of people; their preservation is vital.

State of Our Reefs

Heather stressed that coral reefs are still in decline. This means that nearly 1 trillion dollars annually in food, tourism, and coastal protection are in jeopardy. Our science is telling us that 75% of reefs are currently threatened and this figure is anticipated to climb to 90% by 2030. "We're also seeing that Stony Coral Tissue Loss Disease in the Western Caribbean is spreading at 155 meters per day" according to Heather and the CORAL team scientists. This is a highly lethal disease that started in 2014 and continues to spread rapidly across the Caribbean.

While there's urgency to act, the team at CORAL has reason for hope. Starck shared with us that, "for example, 341 commitments worth nearly $20 billion were recently made at the Our Ocean conference this month in Panama including funding for expanding and improving marine protected areas and biodiversity corridors." We find hope in the fact that 193 countries within the UN agreed to the first of its kind high seas treaty to protect 30 percent of our lands and Oceans by 2030.

Our Approach

Starck described CORAL's science-based approach for addressing the needs of the world's coral reefs. This includes supporting resilient coastal communities, reducing water pollution, and promoting sustainable fisheries - all of which we believe will allow coral reefs to adapt and survive as they face global climate change.

Next Dr. Helen Fox, CORAL's Conservation Science Director, shared exciting updates on the progress made by her team in advancing the science around coral adaptation and evolution. This is in hopes that reefs to adapt to the environmental changes brought on by climate change. Dr. Fox's team has been working with the Allen Coral Atlas, a new resource that maps the world's coral reefs and monitors their threats to provide actionable data and a shared understanding of coral ecosystems. CORAL is part of the Atlas partnership and is leading the coordination of the field component of coral bleaching monitoring program. One day, we hope to that helps to improve the detection of bleaching events from space.

A Visit to CORAL's Field Sites

The most engaging addition to the State of the Reef Address this year was live video streaming to field sites in both the Western Caribbean and Hawaii.

Jennifer Myton, CORAL's Conservation Program Director, and Francis Lam, Executive Director of the Roatan Marine Park in Honduras, spoke about their work in the region. One of the main programs at the Roatan Marine Park is the patrol program, which has five boats of rangers who survey this protected marine zone and deter illegal fishing and other activities that counteract local community efforts to improve the environment. CORAL's holistic approach to supporting local organizations has made a real difference in coral reef health in the Western Caribbean, as evidenced by the growth and impact of the Roatan Marine Park.

Next we went to the Mauka (mountains) of Maui where our Hawaiian Islands Program Coordinator, Makayla Richmond, and team are working on sedimentation, a critical issue in the Waikoli watershed of West Maui. They are decommissioning agricultural roads that run parallel to stream gulches and installing plants to trap the sediment. Our approach is intended to be a long-term, nature-based solution to the problem of stormwater run-off depositing tons of sediment suffocating the corals.

What's Next for CORAL?

The Coral Reef Alliance plans to scale up its work to meet the growing needs of coral reefs, and the organization depends on the support of its community to succeed. The Chair of the Board, Kirby Ryan, expressed gratitude to everyone for their ongoing support and involvement in the Alliance's work despite the challenges of the pandemic. Looking forward, we plan to continue urgent and important work to protect and restore coral reefs globally, with the hope of gaining more support from people who are interested in preserving this critical natural wonder that supports 25% of ocean life and hundreds of millions of people.

CORAL's 2023 State of the Reef Address has emphasized the pressing need for action to protect coral reefs. Through the work of scientists, conservationists, and local communities, we hope to preserve these critical ecosystems for future generations.

Interested in attending State of the Reef next year? Sign up for CORAL's newsletter, the e-current.

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State of the Reef Address 2023: Urgent Need for Action to Protect Coral Reefs - Coral Reef Alliance

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The Coral Reef Alliance State of the Reef Address 2023 emphasized the urgent need for action to protect coral reefs. Through the work of scientists, conservationists, and local communities, we can hope to preserve these critical ecosystems and the services they provide for future generations. Join us in protecting and restoring coral reefs globally!

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Beneath the ocean surface, an expansive network of dynamic skeletal-like invertebrates harbours at least 25 per cent of all known marine species. Both hard and soft corals provide the basis for functioning coral reefs, which are some of the planet's most biologically diverse and valuable ecosystems. They provide important cultural, economic, recreational and social benefits to hundreds of millions of people. They buffer shorelines against damage from storms and provide a source of medicine. And they are dying.

Coral reefs are under relentless stress from myriad global and local issues, including climate change, declining water quality, overfishing, pollution and unsustainable coastal development.

"Coral reefs are one of the most sensitive ecosystems globally to the ravages of human activities," says Gabriel Grimsditch, United Nations Environment Programme (UNEP) marine ecosystems expert. "They are especially vulnerable to climate change and warming ocean temperatures, and mass coral bleaching and mortality events are predicted to increase in frequency and intensity as temperatures continue to rise."
How do coral reefs die?
When corals are impacted by these environmental stressors, they expel the microscopic symbiotic algae zooxanthellae from their tissues. Because this is their primary food source, corals become more sensitive to environmental stressors and turn pale or white, hence the term 'coral bleaching'. To recover from bleaching, corals need to re-absorb the zooxanthellae, which is only possible when the effects of environmental stressors are mitigated.

"The loss of foundational species like corals that provide important habitat can have devastating consequences and knock-on effects on the thousands of unique and wonderful species that call coral reefs their home," says Grimsditch.
How healthy are the world's coral reefs?
According to the " Status of Coral Reefs of the World 2020 " report, a quantitative analysis of a global dataset spanning from 1978 to 2019 co-produced by UNEP, the International Coral Reef Initiative (ICRI), the Global Coral Reef Monitoring Network (GCRMN) and various international partners, 14 per cent of the world's corals was lost between 2009 and 2018.

A 70-90 per cent decrease in live coral on reefs by 2050 may occur without drastic action to limit global warming to 1.5°C. Even with urgent reductions to greenhouse gas emissions, global ocean temperatures could still take decades to stabilize.

However, the report notes that "high coral cover and diversity" means that coral reefs are resilient and can recover if we safeguard the marine environment and create the right conditions.
What can we do to save coral reefs?
Decision-makers must be decisive in leading urgent climate action to ensure coral reefs survive. For one, including coral reefs as a priority ecosystem in the UN Convention on Biological Diversity Post-2020 Biodiversity Framework would hold governments, businesses and other stakeholders accountable for safeguarding their health. Beyond the UN Climate Change Conference in Glasgow, decision-makers must go beyond the goals of the Paris Agreement to secure a future for coral reefs.

Meanwhile, reducing local anthropogenic pressures through legislation, education and other means would promote reef resilience. "Climate action and reduction of localized threats must go hand-in-hand if we want coral reefs to survive for future generations to enjoy and benefit from them," says Grimsditch.

Coral reef monitoring and restoration can supplement global efforts to address climate change and other stressors. Photo: UNEP

How is UNEP addressing coral reef health?
UNEP sets the environmental agenda and serves as an authoritative advocate for the global environment. It addresses coral reef health through the lenses of science, management, policy and funding.

In association with its partners, UNEP releases important reports on coral reef topics such as restoration, bleaching projections, international policy, economic value and more to provide decision-makers and the public with reliable information and recommendations.

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Coral reefs are under relentless stress from issues such as climate change, declining water quality, overfishing, pollution and unsustainable coastal development.