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.
A squat lobster and blackbelly rosefish find shelter on a Lophelia pertusa coral reef off the southeastern United States.
World Phenomenon
Because they don’t depend on warm water or sunlight, deep-sea corals are able to live in many different places around the world. They are far more extensive than scientists previously imagined—living even in waters as cold as -1ºC (30.2ºF).
For example, deep-sea corals occur in the waters of the United Kingdom, Australia, New Zealand, Canada, Ecuador, Japan, Norway, and the United States. Scientists have even found deep-sea corals off the coast of Antarctica. They grow in all the world’s ocean basins, where they form deep-water havens on continental shelves and slopes, in ocean canyons, and on tall seamounts.
Stunning Diversity
Deep-sea corals come in a virtual paint box of colors—yellow, orange, red, purple, and more. Their shapes are equally varied and include branching, fan-shaped, and feather-shaped forms, to name a few.
When it comes to size, the range among deep-sea corals is tremendous. Scientists have discovered single polyps as small as a grain of rice, tree-like coral colonies that tower as tall as 10 m (35 ft), and massive coral reefs that stretch for 40 km (25 mi). But the ocean is a vast realm. There may be even bigger deep-sea corals out there still to be discovered.
Meet Ocean Explorer J. Murray Roberts
Title: Honorary Research Fellow, Scottish Association for Marine Science
Specialty: Basic biology and ecology of deep-sea corals
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