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10 Coral Facts About This Mysterious Marine Animal

While terrestrial ecosystems like rainforests get more attention, coral reefs are equally essential ecosystems that support 25% of marine life. These top coral facts will reveal their impact on the earth's biodiversity and survival.

One fun fact about corals–often mistaken for rocks or plants–is that they are marine animals and colonies of tiny polyps. Furthermore, they are highly diverse, with over 600 coral species living in the Coral Triangle, located in Southeast Asia.

Another fact is that their symbiotic relationship with zooxanthellae, a type of algae, gives them nutrients to help them grow. Understanding these facts about coral reefs will show us how important they are to our world's ecology.

If the survival of corals concerns you, learn about why coral reefs are dying and how to take action.

10 Coral Facts

brown coral
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1. Corals are animals.

Let's begin this list of coral reef facts by dispelling the misconception that corals are plants. Even though they look like underwater gardens, corals are not plants. Instead, they are relatives of sea anemones and jellyfish. Moreover, each coral structure comprises thousands of tiny polyps with tentacles. 

Also, corals show animal-like behavior and don't depend on sunlight for food. They are carnivorous animals that sting their prey like jellyfish. Moreover, corals have a symbiotic relationship with the zooxanthellae algae. They live within the coral's tissues and use photosynthesis to produce food for both organisms

In addition, the corals' nocturnal feeding habits suggest they are more animal than plant.

2. Corals are thousands of years old.

assorted color coral
Photo by David Clode on Unsplash

Next on our coral facts list: Some of the planet's coral reefs have existed for over 5,000 years. They are some of the world's oldest and largest living things. Hard and soft corals can live together on a single reef. (Hard corals form reefs.) Moreover, their slow growth–only a few centimeters a year–helps them withstand climate and sea-level changes, increasing their lifespan.

Various marine animals live in these tropical coral reefs, an underwater cradle of biodiversity. The number of fish species and other animals living in a coral reef also indicates its age.

3. Corals eat at night.

When night falls, corals reach out their tentacles to eat their favorite food, zooplankton. These organisms also become active at night, presenting a dinner buffet for the corals1. They capture prey using their tentacles, equipped with tiny venomous cells to capture and immobilize zooplankton.

With prey in their grasp, the corals pull them into their mouths. This nocturnal feast feeds every individual coral polyp in the coral colonies. 

4. Corals and algae help each other.

purple and green coral
Photo by David Clode on Unsplash

Zooxanthellae algae live in the corals' bodies, enjoying their protection while they photosynthesize food. During the day, zooxanthellae provide their host with sugars, like energy drinks, fueling coral growth and reproduction. However, deep-sea corals don't need algae to create food; they can live on food particles floating in the water. 

Besides, the algae produce pigments during photosynthesis, painting the corals in various shades to create an underwater masterpiece. Coral reefs thrive thanks to this relationship.

5. Coral reefs support marine life.

A coral reef is like a bustling underwater city, supporting many marine life. Tiny parrotfish, clownfish, sea turtles, larger sharks, marine mammals, and other marine species live within the reefs, along with crabs and shrimp on the reef floors.

The reefs' intricate architecture provides hiding spots and habitats for sea creatures, resulting in a complex food web. Sharks visit the reefs due to the abundance of prey. Scientists also consider coral reefs living libraries containing valuable insights into the earth's history. 

6. Corals might have medicinal properties.

coral with fishes
Photo by Francesco Ungaro on Unsplash

One fascinating coral fact is that corals also contain various chemical compounds with potential medicinal properties. These compounds have intrigued researchers due to their potential use in modern medicine.

These coral compounds might help develop cancer-fighting drugs. In addition, the calcium carbonate skeletons of hard corals have attracted scientists studying bone grafts. 

However, extracting these valuable compounds must be sustainable and not damage the coral reef. 

7. Corals can lessen the impact of storms.

Besides supporting various animals, corals are also natural protectors during hurricanes and storms, reducing wave energy by up to 97%. Their ability to dissipate wave energy mitigates the devastation of tsunamis and hurricanes. Moreover, their effectiveness as breakwater embankments rivals the artificial ones that protect coastlines from the ocean2.

Hurricanes battered the Eastern coastline of North America and the Caribbean in the 2000s. Those areas with abundant coral reefs suffered dramatically less damage than those without. Moreover, scientific evidence connects the health of coral reefs to safeguarding coastlines.

Corals extending for a few meters can protect countries that suffer frequent storms. Studies have shown that corals reduce storm damage by almost 30%. If the coral extends for a few hundred meters, it can reduce damage by 57%. 

You can also find coral reefs in a lagoon with shallow water, which protects them from storms. The waters in the lagoon are noticeably calmer than the seas beyond.

8. Corals reproduce in many ways.

Corals can reproduce asexually and sexually. First, a parent coral polyp can grow a 'bud,' which grows into a full-fledged polyp carrying the parent's genetic makeup. Likewise, pieces of the coral colony can break free and form a new colony somewhere else after surviving ocean currents. 

On the other hand, corals also undergo mass spawning. Depending on lunar phases and water temperature, colonies release eggs and sperm into the water. After fertilization, the eggs transform into larvae called 'planulae.' The planulae travel across the ocean currents, avoiding predators and settling on a suitable substrate. Eventually, the coral larvae grow into a brand new coral colony.

9. The Great Barrier Reef is visible from space.

coral close up
Photo by David Clode on Unsplash

Stretching over 2,300 kilometers off the coast of Australia, the Great Barrier Reef holds the title of the world's largest coral reef system. You can see it from outer space due to its vastness of nearly 350,000 square kilometers. It is also one of three coral reefs: atolls, fringing reefs, and barrier reefs.

Over 900 islands and around 3,000 individual coral reefs form the Great Barrier Reef, providing a diverse habitat for many marine species. Millions of unique species like whales, tortoises, snakes, and countless varieties of fish live there, enjoying support from billions of tiny coral polyps working together. 

10. Corals are endangered species.

The International Union for Conservation of Nature (IUCN) reports that human activities and climate change put nearly a third of coral species on the brink of extinction.

As global temperatures continue to rise, oceans also get warmer, causing increased coral bleaching. This phenomenon involves corals expelling their zooxanthellae due to the high water temperature.

Furthermore, commercial fishing has driven up carbon dioxide levels in the ocean, leading to rising ocean acidity. Acidification threatens corals because they cannot build protective shells when the ocean becomes too acidic. 

Some fishing methods and pollution from fertilizers, sewage, and oil spills, also damage the reefs. Finally, overfishing removes essential species that regulate populations of animals that eat coral.

Related read: Environmental impact of fishing, read more ocean facts, and check our World Oceans Day to explore initiatives working to protect our oceans. To further explore the animal kingdom, check out some of the other animals that start with C.

What is your favorite coral fact? Remember to share it with your friends!


Sebens, K. P., Vandersall, K. S., Savina, L. A., & Graham, K. R. (1996). Zooplankton capture by two scleractinian corals, Madracis mirabilis and Montastrea cavernosa, in a field enclosure. Marine Biology, 127(2), 303-317.


Ferrario, F., Beck, M. W., Storlazzi, C. D., Micheli, F., Shepard, C. C., & Airoldi, L. (2014). The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nature Communications, 5, 3794.

Mike is a degree-qualified researcher and writer passionate about increasing global awareness about climate change and encouraging people to act collectively in resolving these issues.

Fact Checked By:
Chinny Verana, BSc.

Photo by Francesco Ungaro on Unsplash
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