Coral is created from layers of bone-like deposits made of calcium carbonate. The calcium deposits of coral accumulate over time to form coral reefs. The upper layers of these deposits provide homes for the living, colorful part of the coral called "polyps."
Algae (zooxanthellae) has adapted to survival on the coral reef by living inside the polyps of the coral. The algae provides the coral with nourishment and oxygen. In exchange, the coral provides a home for the algae.
Seagrass has adapted to living in habitats behind the coral reefs (back reefs) where they trap sediments from overloading coral reefs. Seagrass provides transferable food and oxygen to the coral reefs.
Mangroves have adapted by growing behind the beds of seagrass and coral reefs. Mangroves line shores and grow above sea water while their roots trap and prevent heavier sediments from overpowering the seagrass and coral reefs. Mangroves also provide a nourishing habitat for marine life.
Coral reefs are found in warm, tropical ocean waters (68 to 82 degrees Fahrenheit is required for reef survival). Since ample sunlight is required for warmth, coral reefs are typically found in the shallower ocean waters closer to shore.