This image of a coral reef was taken by NOAA photographer David Burdick in the waters off the coast of Micronesia in the Pacific Ocean. Most of the coral species on this reef are acropora. The large, flat structures are known as table coral, a type of acropora coral. Coral reefs are sometimes often referred to as "rainforests of the sea", because rainforests on land, the reefs are home to some of the most diverse ecosystems on Earth. They provide a home for at least 25% of all marine species.