Corals are small living organisms found in the oceans around the world. They attach to firm surfaces and then produce a calcium carbonate exoskeleton. They are communal organisms that live in huge colonies such as the Great Barrier Reef off Australia. They are generally considered symbiotic with various types of Algae and best known in the tropics, forming beautiful beaches and amazing diving sites. These though are primarily the shallow water corals, there are deep (or "cold ") water corals found all the way north of Norway!
Deep water corals? Are they something new or recently discovered? Are they the same as Shallow Water Corals in requirements or life cycles? How big do they get? How do they differ from shallow water, tropical corals?
The National Oceanographic and Atmospheric Administration website states that deep water corals do exist and have been on the planet probably longer than their shallow water cousins, but just not as well known. Fishermen brought them up with deep lines and on anchors centuries ago. Some, such as Black Coral was been used for ages for making jewelry, but it is now an endangered species. In 1859, Edward Forbes wrote the book, Natural History of the European Seas. In it he describes the deep sea coral :
"The great tree Alcyonium (now Paragorgia), a branched zoophyte of leathery texture, is a very wonderful and characteristic production of the abysses of the Boreal Seas. The lines of the fishermen, when fishing for the redfish, or ur, become entangled in its branches, and draw up fragments of considerable dimensions, so large, indeed, that the people of the country believe it to grow to the size of forest-trees, an exaggeration in all probability, but nevertheless one founded in unusual magnitude" (p.71).
Some huge individuals have been found, so the size may not be as much of an exaggeration as Forbes thought!
Most known corals grow in warm, clear water at depths of less than 50 meters with temperatures around 20 degrees Celsius. Deep water corals, perhaps better termed Cold Water Corals as they can live in shallow water as well, have been found living at depths of greater than 6300 meters and temperatures of 4 C, as well as in shallow water along the coasts of Canada. So one major difference is that they are more tolerant of lower temperatures as well as a variety of pressures!
Because they generally live at greater depths where light is limited, they are not symbiotic with algas! Deep Water corals are filter feeders, shifting out dead debris as it floats down from above. This means they are more tolerant of silting that tropical coral reefs. The greater depth also means they are not commonly seen by divers!
Do these it mean that Deep Water Corals are less important? No! They harbor life, clean the ocean's waters and are valuable members of the ecosystem. According to the Woods Hole Institute, they provide life and habitat for thousands of other organisms!
All coral is formed of polyps and all is fixed to a surface with a hard exoskeleton and comprised of thousands of creatures. . Deep Water Corals, are different from their tropical cousins. They live at deeper depths, are more temperate tolerant and have different feeding habits, but all corals are valuable. Treasure the differences, they are important!