What Is a Coral Reef?
There are many bumps and ridges in the ocean. When the tops of these ridges are close to the water’s surface, those ridges are called reefs. A coral reef is made up of little animals called corals. A single coral is called a polyp. A polyp has a soft tube-like body with tentacles that surround its mouth. The corals build hard skeletons around their soft bodies. New corals keep growing on top of the dead coral skeletons until a reef is formed.
Corals eat by catching small animals with their tentacles. Each tentacle has thousands of tiny stingers that stun the animals so the coral can eat it. Another way they eat is through the algae that live inside the polyps. The algae take in sunlight and change the sunlight into food. They then give off nutrients for the polyps. The polyps use these nutrients to help build their hard skeleton. Algae are so small that two million of them could live in coral as big as your fingernail.
You can only find coral reefs in warm ocean water. Since algae need sunlight to produce nutrients, corals can only grow in water where there is sunlight.
Why Are the Coral Reefs Important?
The coral reefs are some of the most biodiverse places on Earth. Besides rain forests, coral reefs have more living species than any other ecosystem. Because of that, coral reefs are often called the “rain forest of the ocean.” Some coral reefs are home to hundreds of species of coral, thousands of species of mollusks and two thousand species of fish.
Coral reefs protect coasts from erosion by slowing down or stopping ocean waves. Scientist also think coral reefs might help prevent global warming because coral takes in carbon dioxide (CO2). Too much carbon dioxide in the atmosphere can raise the earth’s temperature.
Doctors use limestone from coral to replace parts of human bones. Scientists are still researching to see if some coral animals may lead to new medicines for humans.
Coral reef animals provide food for people. The reefs also provide exotic fish for people to enjoy. Many island or coastal communities depend on coral reefs to bring in tourists.
What Are the Dangers to Coral Reefs?
Some scientists say that over 70% of the world’s reefs are either dead or dying. There are a number of reasons why coral reefs are threatened. Hurricanes and tropical storms can break off parts of the reefs. The reef might recover from this kind of damage, but it will take a long time.
Agricultural fertilizers and human waste from sewers that get dumped into oceans can cause overgrowth of algae. The algae can cover up the coral, not allowing sunlight to reach the coral polyps. This will eventually kill the coral.
Starfish, especially the crown of thorns, eat coral. One crown of thorns starfish can destroy about 65 square feet of coral reef. There are fish that eat starfish, but overfishing can cause these fish to die out. Without predators, the starfish population will increase. More starfish means more danger to the reefs.
Fishing methods make fish easier to catch, but they also harm coral reefs. Some fishermen spray poison called cyanide (SY-uh-nide) to catch fish. What the fishermen don’t know is that poison kills the coral reefs, too. Fishermen also blast dynamite in the ocean to stun fish. However, the fishermen are also blasting off chunks of coral reef.
Burning fossil fuels can increase the amount of carbon dioxide and cause the earth’s temperature to increase. This leads to global warming. The earth’s higher temperature warms up the water causing corals to bleach and die.
Cutting down forests can cause soil to wash into the ocean. This is called erosion. The dirt in the water stops sunlight from reaching the coral. Then the algae can’t make the nutrients the coral needs to survive.
Increased tourism can lead to trouble for coral reefs. More hotels and seaside homes can bring increased pollution. Careless divers and boaters can damage coral reefs by breaking off chunks of the reef.
Coral reefs in all tropical waters are threatened. Some reefs in Hawaii and other remote island locations are in good condition. However, those in the Florida Keys in the U.S. have been severely damaged.
The Great Barrier Reef along the northeast coast of Australia is the world’s largest system of reefs. In 2004, the Australian Parliament made a law that prohibits commercial activities, except for tourism, in one third of the reef’s area. In the late 1960’s, crown of thorns starfish started to invade the Great Barrier Reef. However, the main threat to the reef today is bleaching caused by global warming.
How You Can Help?
One of the best ways to help the reefs is to conserve energy. Energy is most often made by burning coal or other fossil fuels. This releases carbon dioxide into the air which leads to global warming. This in turn causes the warming of ocean waters and leads to the destruction of coral reefs. Some ways you can help conserve energy are to turn off lights when you are not using them, ride your bike to school instead of driving, recycle, waste less and use less paper.