Amazing Kids! Magazine

Coral Reefs

By Ryan Traynor, Editor-in-Chief


A coral reef is part of a large ecosystem that includes one of the most diverse communities in the world.  Coral Reefs cover less than one percent of Earth’s Surface but they hold more than 15 percent of all fish species. Corals are tiny animals that stay fixed in one place. They belong to the group cnidarian which include hydras, jellyfish, and sea anemones. However, corals live in colonies called polyps where they reach out their tentacles to catch prey to feed. They secrete a hard calcium carbonate skeleton which provides protection. It is this secretion that builds up and forms a coral reef over time. The living colony secretes the calcium carbonate at its base, creating coral reef structures completely covered by the living polyps. As the living colony continues to secrete, the size of the coral reef grows from .3 to 10 centimeters per year. There are many different species of coral. Different species build structures of different shapes and sizes which brings diversity to the coral reef ecosystem. Various coral species tend to group into specific zones on a reef because of competition from other species and by environmental conditions.

What do coral polyps eat? Almost all reef-dwelling corals have their food made by algae. The algae live inside the coral polyps and perform photosynthesis which produces food that is shared with the coral. This type of relationship is call symbiotic because it is mutually beneficial to both organisms. In exchange the coral provides the algae with protection and access to light, which is necessary for photosynthesis.

Where are coral reefs? Corals are found across the world’s ocean, in both shallow and deep water, but reef-building corals are only found in shallow tropical and subtropical waters. This is because the algae found in their tissues need light for photosynthesis and they prefer water temperatures between 70-85°F (22-29°C). There are also deep-sea corals that grow in cold, dark water at depths of up to 20,000 feet (6,000 m). Deep-sea corals do not have the same algae and do not need sunlight or warm water to survive, but they also grow very slowly. One place to find them is on underwater peaks called seamounts. The largest coral reef is the Great Barrier Reef, which spans 1,600 miles (2,600 km) off the east coast of Australia. It is so large that it can be seen from space!

Reefs are generally classified in three types. Fringing reefs, the most common type, shoot off out to the sea from the shores of islands or continents. Barrier reefs are platforms separated from nearby land by a bay or lagoon. Atolls rest on the tops of submerged volcanoes where parts of the atoll may emerge as an island. They are usually circular or oval with a central lagoon.

Coral reefs provide habitats for a large variety of sea life. The sea life rely on corals as a source of food and shelter. Besides the corals and the algae, the reefs also contain various sponges, mollusks such as sea slugs, oysters, and clams, crustaceans like shrimp and crabs, sea worms, star fish and sea urchins, jellyfish and sea anemones, fungi, sea turtles, and many types of fish such as the triggerfish, butterflyfish, lionfish, and parrotfish.

Coral reefs are disappearing because of changes in the light and warming of the ocean’s temperature that kills off the algae, overfishing, pollution, development and erosion.  These threats could kill 30 percent of the existing reefs in the next 30 years. We must fight to save our coral reefs. Coral reefs are a precious resource in the ocean because of their beauty and biodiversity. Coral reefs provide shelter for a wide variety of marine life, recreation, a valuable source of organisms for potential medicines, sand for beaches, and a buffer for shorelines.