Mesophotic coral reef

A Mesophotic coral reef or mesophotic coral ecosystem (MCE), originally from the Latin word meso (meaning middle) and photic (meaning light), is characterised by the presence of both light-dependent coral and algae, and organisms that can be found in water with low light penetration. Mesophotic Coral Ecosystem (MCEs) is a new, widely-adopted term used to refer to mesophotic coral reefs, as opposed to other similar terms like "deep coral reef communities" and "twilight zone", since those terms sometimes are confused due to their unclear, interchangeable nature.

They normally grow between 30 and 40 metres (130 ft) and up to 150 metres (490 ft) in tropical and subtropical water. The most common species at the mesophotic level are corals, sponges and algae. The corals ranges can overlap with Deep-water coral but are distinguished by the presence of zooxanthellae and their requirement for light. They can also be thought of as part of shallow water coral ecosystems, and a crossover of coral species between the two is common. It is thought that these corals could be used as sources for reseeding shallow water coral species, but recent analyses show that mesophotic ecosystems are more unique that previously thought and also threatened. The oldest known mesophotic coral ecosystems have been described from the Silurian of Sweden, such ecosystems are also known from Devonian. Oldest scleractinian-dominated mesophotic ecosystems are known from the Triassic.