Throughout the world, cold-water corals appear to be adapted for particular environments. They are exclusively marine, found in areas away from the influence of coastal seawater either in the deep-sea or the deeper waters of fjords, with the highest aggregations appearing to be related to the presence of oceanic water masses.
They are usually found below the photic zone, between 200 and 400 metres, but the shallowest found so far was at 40 metres and the deepest at well over 1,000 metres. Corals are found in areas with a topographically enhanced bottom current, which serves several purposes. Firstly, the current will have scoured mobile sediments from the area, revealing areas of hard substrate suitable for coral settlement. Secondly, the fast currents limit the amount of sediment deposition on existing reefs. Thirdly, the currents deliver a constant food supply to the waiting corals.
The upper depth limit of corals may be restricted by the level of the seasonal storm wave base. These heavy surges occur as storms develop on the surface and can cause damage to the slow growing reef.
Lophelia pertusa (after Freiwald et al, 2004)
Madrepora oculata (after Freiwald et al, 2004)
Paragorgia arborea (after Tendal, 1992)