It may be the last place you’d expect to find corals—up to 6,000 m (20,000 ft) below the ocean’s surface, where the water is icy cold and the light dim or absent. Yet believe it or not, lush coral gardens thrive here. In fact, scientists have discovered nearly as many species of deep-sea corals (also known as cold-water corals) as shallow-water species.
Like shallow-water corals, deep-sea corals may exist as individual coral polyps, as diversely-shaped colonies containing many polyps of the same species, and as reefs with many colonies made up of one or more species. Unlike shallow-water corals, however, deep-sea corals don’t need sunlight. They obtain the energy and nutrients they need to survive by trapping tiny organisms in passing currents.
Within the last 20 years scientists, aided by technological advances, have uncovered one surprise after another about deep-sea corals.