The largest known cold-water coral reef, discovered off Norway in 2002, is the Røst Reef. It lies about 100 kilometres west of Røstlandet in Norway’s Lofoten region, beneath waters far colder and darker than those associated with tropical coral reefs.
The reef is built mainly by Lophelia pertusa, a stony, branching coral that can grow into extensive three-dimensional colonies. Røst Reef stretches for roughly 43 kilometres and reaches a width of up to 6.9 kilometres. Near the seabed, the water temperature is approximately 2°C.
“Cold-water coral reef” is an important part of the clue. These reefs do not depend on sunlight or shallow, warm seas; instead, corals capture food particles from currents. They provide shelter and nursery habitat for many deep-sea organisms, but bottom trawling can break fragile coral structures that took centuries to develop.
A common mix-up is Træna Reef, another major Norwegian coral reef. Træna is notable, but Røst is generally identified as the world’s largest known deep-water coral reef and the largest known Lophelia reef.