Cold-water coral reefs

Scleractinian hard corals in deep, cold waters have been known since the eighteenth century. However, advances in deep-ocean exploration are now revealing the true scale and distribution of cold-water coral reefs. This prompted a resurgence of interest with dramatic discoveries of deep-water reef and coral carbonate mound provinces rapidly followed by improved understanding of coral reproduction, feeding, and molecular genetics. Hundreds of tropical coral species build shallow reefs, but less than 10 cold-water species form deep reef frameworks. Of these, the best characterized is Lophelia pertusa, which dominates in the Northeast Atlantic. Assemblages of octocorals and hydrocorals are found in other parts of the world's oceans, such as the North Pacific. Cold-water coral skeletons provide well-preserved, high-resolution paleoclimatic archives and recent advances have been made in interpreting geochemical proxies for seawater temperature and ocean ventilation history. The reefs form structurally complex habitats supporting many other species. This complexity makes them vulnerable to mechanical damage from deep-water bottom trawling and modeled scenarios suggest that cold-water coral reefs may be threatened by ocean acidification. Integrated basin-scale studies are needed to understand linkages between reef provinces as a critical step toward developing meaningful systems of protected areas for their conservation.