Despite its name, black coral is rarely black. In fact, this deep-dwelling coral species is most often either white, red, green, yellow or brown; its name refers to the skeleton’s color. Part of the order Anriparharia, there are more than 280 species of black coral worldwide. While abundant at depth, residing between 1,000 and 10,000 feet (300 and 3000 m), recreational divers can nonetheless see a variety of species in shallower water. Harvested for decades between the middle and end of the 20th century, black coral was highly sought after for lucrative jewelry pieces. This industry has unfortunately devastated many shallow black-coral gardens, especially in Hawaii where the coral was once bountiful.
What makes black coral special?
Extremely different from other well-known coral families, black coral is unique due to its skeletal formation. Some species are wispy, resembling coils of DNA. Others look like trees and others are only single stalks. Protein and chitin make up all black coral, and it does not need light to grow, as other corals do. Consequently, this species thrives at depth. In fact, the chitin allows the thinner branches to be flexible while the stem is thicker and provides structural support like a tree trunk. Many species can grow larger than 12 feet (3 m). Others grow to no more than 1.2 inches (3 cm). Although the coral has thousands of polyps, this living tissue is minute. Microscopic thorns protrude from each skeletal branch, thus the common nickname ‘thorn coral.’
Where can you find it?
While black coral is somewhat difficult to study in great detail due to its depth, scientists believe that it flourishes in tropical and subtropical regions, where it feeds on zooplankton blooms. However some species grow even in the frigid Arctic and Antarctic waters. This coral tends to have very few predators except for some gastropods such as sea snails and turtles. Consequently, scientists think one species, ‘Leiopathes glaberrima‘ has lived to 4,265 years of age, making it one of the oldest organisms on earth.
Divers can observe black coral easily on the Baros Atoll in the Maldives, on deeper sites in the Canary Islands, in New Zealand’s Milford Sound, and especially in Hawaii, where black coral is so famous that it is the official state gem of the islands.