Coral Reefs are considered to be some of the most beautiful natural features around the globe. They’re home to an incredibly biodiverse population of plants and animals, but none is more important than the coral itself. When looking at the organism, you may be wondering “is coral a plant or an animal?”, and you aren’t alone. Let’s explore exactly what coral is, and see why it’s so important to our world as we know it.
Is coral a plant or animal?
Coral may be attached, or “rooted” to the seafloor, hence why it’s often misidentified as a plant, but coral itself is an animal, as they don’t synthesize their own food like plants do.
What exactly is coral?
The entire structure that we generally refer to as “coral” is actually thousands of tiny coral creatures called “polyps”. These polyps are invertebrates that range from no bigger than a pinhead to up to a foot in diameter with a saclike body and a mouth that’s encircled by stinging tentacles.
They have a symbiotic relationship with plant-like algae called zooxanthellae that reside in the coral’s tissues. These algae benefit from this relationship by making use of the coral’s metabolic waste products during photosynthesis. In turn, the coral has access to the byproducts of photosynthesis, such as oxygen and organic products that the coral requires to thrive. This relationship is the reason why coral reefs are the largest structures of biological origin on Earth, rivaling even old-growth forests in longevity and size.
How is coral formed?
Coral polyps arrive at the spot for the future coral reef as free-swimming larvae that will attach themselves to submerged rocks or other hard surfaces at the edges of islands or continents. The magnificent structures formed by corals are created by each soft-bodied polyp secreting a hard outer skeleton of limestone that attaches either to that rock or the dead skeletons of other polyps.
This limestone comes from the seawater, and serves to protect the soft, delicate body of the polyp. These conglomerates grow, die, and endlessly repeat the cycle while laying the limestone foundation for the reefs.
Where are coral reefs found?
Coral reefs are most commonly found along the rocky edges of continents, primarily in warm, clear, and shallow water to ensure lots of sunlight for their symbiotic algae. They’re found in more than 100 countries around the world, mostly between the tropics of Cancer and Capricorn. Worldwide, they cover an estimated 110,000 square miles.
Corals need saltwater to survive, meaning they grow poorly near river openings or coastal areas with excessive runoff. They’re especially sensitive to pollution and sediments, as they can create cloudy water and end up deposited on corals, blocking out the sun and harming the polyps. Wastewater discharged into the ocean can also be a problem for them, as it can lead to overcrowding of seaweeds that can outcompete coral. This makes it even more difficult for their zooxanthellae to photosynthesize and further harms the coral by depriving it of oxygen.
Biggest coral reefs in the world
1. Great Barrier Reef
The Great Barrier Reef is the world’s largest coral reef system – but it isn’t really just one reef. Rather, it’s over 2,900 individual reefs and 900 islands that stretch over 1,400 miles. It’s located in the Coral Sea off the coast of Queensland, Australia, and is well known for being so large that it can be seen from outer space.
It supports an extraordinary diversity of life, including many vulnerable or endangered species that are endemic to the area, such as the drastically endangered Dugong that has fewer than 10,000 left in the wild.
2. New Caledonian Barrier Reef
As the name suggests, this reef is located in New Caledonia in the South Pacific, and is the longest continuous barrier reef in the world, stretching over 930 miles. It’s believed to surpass the Great Barrier Reef in both fish and coral diversity, as it’s an important breeding ground for the endangered dugong and green sea turtles. It’s also well known for an area known as the “Shark Pit” that’s popular among divers for the presence of Barracuda and Gray Reef Sharks.
3. Mesoamerican Barrier Reef System
The Mesoamerican Barrier Reef System, also known as the Great Mayan Reef, is a system that stretches over 620 miles from the tip of the Yucatan Peninsula down to the Bay Islands of Honduras. It has over 65 species of Stony Coral, and is home to two species of drastically endangered coral – Elkhorn Coral and Black Coral.
The biggest threat to this reef is the invasive species of Red Lionfish that eat nearly every reef-tending species, such as Cleaner Shrimp and other species that eat algae. These animals keep the corals clean, alive, and disease-free. This system is well known for having the world’s largest populations of manatees, and some northern areas of the reef system are home to the largest fish on the planet – the Whale Shark.
4. Florida Reef
The Great Florida Reef is the only living coral barrier reef in the continental United States, and is the third-largest coral barrier reef system in the world, stretching for 170 miles. There are more than 6,000 individual reefs in the system, some dated at nearly 7,000 years old.
It contains more than 40 species of stony corals, including Smooth Starlet Coral and Elliptical Star Coral that make a perfect habitat for anemones, seastars, and spiny lobsters. These corals comprise over 80% of all the coral reef species in the Tropical Western Atlantic.
5. Apo Reef
The beautiful Apo Reef is the largest coral reef in the Philippines, spreading over an area of 20 miles and is the second-largest connecting coral reef in the world. It’s located at the northern tip of the Coral Triangle and is home to over 2,000 species of reef fish and 600 reef-building coral species.
The Apo Reef best known for its incredible water quality, and is a popular spot among divers for its Reef Sharks in the shallows, and Hammerhead Sharks that swim in the deeper portions. It’s also home to many species of sea turtles that rely on the ecosystem for food and for breeding grounds.
6. Red Sea Coral Reef
There are multiple individual coral reefs within the Red Sea, but they’re all referred to as a large grouping in these warmer waters that spans around 150 miles of coastline. These corals have been notably resilient concerning global warming, as it’s the only grouping of reefs that hasn’t experienced a mass bleaching event as of this year.
As it turns out, those corals in the Gulf of Aqaba and throughout the sea are unaffected by ocean acidification and the steadily warming waters. This is great news for the 300 species of coral that make their home there, 10% of which are found nowhere else in the world. Common residents there are spinner dolphins, dugongs, turtles, mantas, and many species of shark.
Why are coral reefs important?
Coral reefs are the equivalent of underwater forests, and play a huge role in ocean ecosystems.
1. They provide habitats and shelter for nearly 25% of all life on Earth
Coral reefs support more species per unit area than any other marine environment, housing about 4,000 species of fish and 800 species of hard corals. Scientists estimate there may still be millions of undiscovered organisms living in and around reefs.
2. They protect coastlines from the damaging effects of wave action and tropical storms.
Coral reef structures buffer shorelines against 97% of the energy from waves, storms, and floods. When reefs are damaged or destroyed, the absence of this natural barrier can increase the damage to coastal communities.
3. They’re the source of nitrogen and other essential nutrients for marine food chains.
Corals are home to many nitrogen-fixing bacteria, which is helpful because the surrounding marine waters are often low in this essential element. Nitrogen gases are abundant in the area, but most organisms aren’t able to use it in that form, necessitating these bacteria for a reef to flourish.
4. They help with nutrient recycling
Those zooxanthellae algae that reside in corals play an important role in transforming inorganic carbon, like carbon dioxide, into organic carbon through photosynthesis. The bacteria mentioned above do help with this recycling effort, but the majority of it falls to the corals. The reef goes through extremely high levels of carbon, nitrogen, and phosphorous recycling to make a magnificent, self-sustaining ecosystem.
5. Their residents are integral to human health
The extreme biodiversity of coral reefs has led to huge breakthroughs in new medicines. Many drugs are developed from coral reef animals and plants, some of which proving to be potential cures for cancer, arthritis, human bacterial infections, and even viruses.
6. They’re even important for the economy
The National Marine Fisheries Service estimates the commercial value of US fisheries from coral reefs is over $100 million. Many local economies are based around tourist money that’s drawn there by their natural wonders.