Mesophotic coral ecosystems exist in low light—"meso" means middle and "photic" refers to light.
Mesophotic coral ecosystems are found in tropical and subtropical regions at depths ranging from almost 100 feet to over 490 feet below the ocean’s surface. The dominant communities providing structural habitat in the mesophotic zone are corals, sponges, and algae.
Little is known or understood about these ecosystems because until recently, studies were hampered by lack of technology. The upper limit of mesophotic coral ecosystems coincides with the diving limit for conventional scuba diving (130 feet), but is too shallow and costly for most deep-diving technologies, such as remotely operated vehicles and submersibles, to operate in. However, advances in undersea technologies in the past decade now make it possible to investigate these ecosystems.
In an era of significant changes occurring on shallow coral reefs, it is important for scientists to understand the role of mesophotic coral ecosystems in tropical and subtropical regions. These ecosystems are regarded as extensions of shallow coral ecosystems and share common species. As a result, scientists hypothesize that mesophotic corals may serve as potential sources to reseed or replenish degraded shallow-water reef species.
Mesophotic coral ecosystems also serve as essential fish habitat for some economically and ecologically important fish species, which use these areas for spawning, breeding, feeding, and growth to maturity. Similar to shallower coral ecosystems, mesophotic coral ecosystems contain organisms with specialized defenses to ward off predators and microbial infections. These specialized defenses often yield compounds that can be used to develop natural products that benefit human health.