• Atolls require warm tropical or subtropical temperatures so corals can develop. Most atolls are located in the Pacific Ocean.

• The lagoon in an atoll can reach depths up to 50 meters or more, but the islands are not very elevated, averaging less than 5 meters.

• An atoll develops with underwater volcanoes (seamounts). When the volcano erupts, lava is piled up on the seafloor, and slowly its elevation grows higher until the top of the volcano becomes an island or reef.

• Corals provide vital shelter for fish and other marine animals.

Food Production

• Plants, algae, and bacteria living in coral reef systems create their own food through photosynthesis.

Nutrients

• Seagrasses form meadows between coral reefs and provide nutrients for sea turtles, urchins, and other species.

Protection

• Mangrove trees can grow on the coast near coral reefs. They stabilize the coast with their roots, protecting it from erosion, wind, waves, and floods.

• Mangroves also function as nursery grounds for juvenile and larval coral reef organisms, who then migrate to the actual reefs once grown.