Ocean Rainforests Coral reefs are large societies of small living organisms. They are made up of millions of different creatures including fish, starfish, sea urchins and much more. Despite the fact that coral reefs make up less than 1% of the Earth's surface, coral reefs are still one of the most diverse ecosystems in the world thanks to the creatures that live in and around coral reefs. Coral reefs are found in shallow, warm waters in the tropics around the Bahamas, in the Red Sea and near the Hawaiian Islands. The largest coral reefs are the Great Barrier Reef, the Red Sea Barrier Reef and the New Caledonian Barrier Reef. ("The 10 Largest Coral Reefs in the World") Coral reefs are made up of the skeletons of calcium carbonate polyps. Polyps are soft, tube-shaped bodies that eventually stick together. Their shape is that of a tin can with an open mouth, ringed by long tentacles equipped with stinging cells. Since polyps are unable to move, they use these stinging cells to capture any creature that ventures into their reach. Individual polyps are often very small, but their skeletons accumulate to form the large colonies we are used to seeing. Polyps build hard, external skeletons to protect their bodies. When carbon dioxide mixes with seawater, carbonic acid is formed. Polyps extract calcium ions from the water and form calcium carbonate which is used to build a calcareous skeleton. Although the original skeletons are simply white, corals acquire their famous bright colors over time thanks to other living organisms. These shades are caused by zooxanthellae microalgae. These single-celled organisms contain a symbiotic relationship with coral polyps. Symbiosis is... the center of the paper....... The real problem is human actions. Human wastewater, toxic chemicals, pesticides and more can disrupt the delicate water balance that corals need to survive. Conservation efforts are being made to avoid all these man-made problems. (“Coral Reef Protection: What Problems Exist?”) Coral reefs have great significance in the world. The sensitivity of coral polyps and the many creatures that live inside the coral can show the quality of the ocean water and whether there are significant changes in the temperature, pH, salinity and chemical composition of the water. Coral reefs also protect coastlines and prevent erosion. Furthermore, coral reefs have been shown to improve the economy due to their status as a very popular tourist attraction. In conclusion, coral reefs have a great impact on the world in several ways. (“Coral Reef Protection: Why Coral Communities Matter?”)