In 2009, a team led by Brendan Roark dated by radiocarbon corals collected around 400 meters deep off the coast of Hawaii, and one of them, a black coral of the genus Leiopathes, was about 4,265 years old. Its trunk grew by a few micrometers per year.
This figure changes the way we look at these shrub-shaped colonies. A branch broken by a poorly placed anchor or a fin strike can represent centuries of growth. And most divers pass by without recognizing them, because black coral almost never looks black.
We review what is verified. The rest has been removed.
How to recognize a black coral?
Black coral is recognized by its polyps rather than its color. Its colonies form shrubs, feathers, or long whips, and each polyp has six simple tentacles that do not retract. The black refers to the internal skeleton, made of chitin and proteins, which the living tissues almost always hide.
The living tissues themselves take on very varied hues.
Depending on the species, they appear white, yellow, orange, red, green, or brown. The name thus comes from the axis, which jewelers have long cut and polished to make beads and pendants. The order name, Antipatharia, comes from Greek and evokes a remedy against suffering, a reminder of the virtues once attributed to this coral, which scientists today classify among the hexacorallians, alongside anemones and stony corals. But the most useful thing in diving remains counting the tentacles. Six simple tentacles means antipatharian. Eight fringed tentacles: gorgonian.
Photos of dark colonies circulating on jewelry sites show the cleaned and polished axis (the living animal does not look like that).
Where does black coral live and at what depth?
Black corals are found in all oceans, from tropical waters to cold seas. The CITES dossier dedicated to Hawaiian black coral lists more than 200 described species, present from about 20 meters down to 8,000 meters, with a majority between 30 and 80 meters. Most do without light.
This independence explains their presence on deep slopes, seamounts, and canyons. They filter plankton brought by currents, thanks to polyps that remain extended day and night. In the Mediterranean, the most studied species is called Antipathella subpinnata. It forms small forests in places on rocky offshore bottoms, generally beyond about fifty meters (indicative order of magnitude, varying by studied area). These forests shelter fish and invertebrates.
However, in Hawaii, the exploited species live much closer to the surface.
The two major commercial deposits discovered in 1958 off the archipelago were located between 30 and 75 meters deep. If you want to compare with reef-building corals, our complete coral guide details the symbiosis with microalgae that most black corals do without, allowing them to colonize bottoms where light is scarce.
| Species | Where | Depth | Verified fact |
|---|---|---|---|
| Leiopathes sp. | Hawaii | About 400 m | Colony dated to about 4,265 years (PNAS, 2009) |
| Antipathes dichotoma | Hawaii | 30 to 75 m | About 6.4 cm height per year, harvested species |
| Antipathes grandis | Hawaii | 30 to 75 m | Harvested species, minimum size imposed |
| Antipathella subpinnata | Mediterranean | Beyond about 50 m (indicative) | Forms forests on rocky bottoms |
| Antipathella fiordensis | New Zealand fjords | Shallow depth (indicative) | White colonies visible in recreational diving |
How long does a black coral live?
Some colonies live several millennia. The study by Roark and colleagues, published in PNAS in 2009, dated a Hawaiian Leiopathes at about 4,265 years, with radial growths measured between 4 and 35 micrometers per year for the deep corals analyzed.
To give you scale, 35 micrometers is less than the thickness of a hair.
However, not all black corals grow at this rate. The CITES file indicates that Antipathes dichotoma, harvested in Hawaii, grows about 6.4 centimeters in height per year. The two measurements do not contradict each other. One concerns the thickness of the trunk of a deep species, the other the height of a species that lives much closer to the surface and in warmer water. In short, beware of pages that give a single growth rate for the entire group, like the “a few millimeters per year” often read.
Researchers read these skeletons like archives. Each layer retains a chemical trace of the water that saw it form, allowing reconstruction of ocean variations over centuries. This record earns Leiopathes a place in our ranking of marine animals that live the longest, with the same source and figures.
Why is black coral protected by CITES?
All black corals have been listed in Appendix II of CITES since 1981. This classification regulates international trade: each export must be covered by a permit, granted if the harvesting does not threaten the species’ survival. The demand mainly comes from jewelry.
In Hawaii, where black coral is the official emblem of the state, harvesting began in the late 1950s. It is still done by diving, by hand, colony by colony, with axes and saws, down to about 75 meters according to the CITES file, which limits harvesting to accessible areas. Rules impose a minimum size of 1 inch diameter at the base, or 122 centimeters in height. This threshold aims to allow each colony to reproduce before being cut, maturity arriving around 10 to 12 years according to the CITES file. However, another threat weighs more heavily.
The invasive coral Carijoa riisei has killed 70% of black coral colonies between 68 and 114 meters in a harvesting area of the archipelago.
Elsewhere, bottom trawling and lost fishing gear break colonies that no one will see regrow. Warming adds to the list of threats facing corals, even if deep species are exposed differently than surface reefs. For the black market, no reliable figures are available. The previous version of this page cited a seizure in Madagascar and a price per kilo, two data points that could not be verified.
If a black coral jewelry piece tempts you while traveling, ask the seller for origin documents. Also check with customs before returning. Without the proper paperwork, the item can be held at the border, and the purchase money goes with it.
Can you see black coral while recreational diving?
Yes, in a few places where species grow at shallow depth. In the Red Sea, whip corals and small antipatharian bushes are found on some walls accessible to recreational diving. In New Zealand fjords, a layer of tinted fresh water cuts the light and allows deep-sea species to live near the surface.
The New Zealand case is the best known. In Fiordland, heavy rains deposit brown water on the surface, rich in tannins, which recreates at a few meters the darkness usually found much deeper. The white colonies of Antipathella fiordensis therefore live at unusual depths. Thus, they can be observed without aiming for a deep dive. None of this informs about the current, temperature, or supervision on the day of your outing.
For what level? Impossible to decide from here.
The required level depends on the site and the club, and it is at the briefing that the depth and fallback plan are set. On the Red Sea side, our article on Red Sea corals facing warming gives the context of shallow reefs. And a black coral colony must not be touched, even with the tip of a glove, for the reasons detailed on our page about why you should never touch marine life.
Searching for these colonies requires a dedicated dive and guide time, with no guarantee of finding them.
FAQ
Is black coral really black?
Only its skeleton is. The living tissues can be white, yellow, orange, red, green, or brown depending on the species. The black appears once the tissues are removed and the axis polished.
How old can a black coral get?
A Leiopathes collected off the coast of Hawaii was dated to about 4,265 years old (Roark et al., PNAS, 2009). Its radial growth is measured in micrometers per year. Other species, found in shallower waters, grow much faster in height.
Can you buy a black coral jewelry?
International trade is still possible with a permit, as all black corals have been listed in Appendix II of CITES since 1981. Ask the seller for the origin documents. Before bringing back jewelry from a trip, check with customs what is required.
Where to see black coral without deep diving?
The fjords of Fiordland, in New Zealand, and some Red Sea drop-offs host colonies at shallow depths. Their presence at a given site is never guaranteed. The local guide remains the best source for their location.
Does black coral need light?
Most species do not depend on it. They feed on plankton captured by their polyps, which allows them to live in darkness, down to several thousand meters.
Sources
- Extreme longevity in proteinaceous deep-sea corals (Roark, Guilderson, Dunbar, Fallon, Mucciarone, PNAS, 2009)
- Case study for black coral from Hawaii (Bruckner, De Angelis, Montgomery, CITES, NDF workshop, 2008)
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