Marine biologists finally know how many candles to put on the birthday cakes for deep water black coral in the Caribbean Sea. And it seems they’ll need a very large cake, since some of the black corals are 2000 years-old.

“The fact that the animals live continuously for thousands of years amazes me,” said Dr. Nancy Prouty of the U.S. Geological Survey Pacific Coastal and Marine Science Center in a press release by the USGS.

Prouty analyzed coral samples collected by the USGS and colleagues between 2003 and 2009 to figure out the age of the ancient corals.

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Black corals usually only live in very deep water, starting at around 1000 feet and going down to nearly 2 miles beneath the waves.

“We used a manned submersible, the Johnson-Sea-Link, to go to the sea floor and specifically collect certain samples using the sub’s manipulator arms,” Prouty said.

Like Yoda from Star Wars, the Caribbean deep water black coral is very old, but also very small. Even the 2000 year-olds are only a few feet tall.

The corals grow 8 to 22 micrometers per year, that’s .0003 to .0008 inches per year. Compared to black coral, shallow-water reef-building coral are speedy. They grows about 10 millimeters per year, 600 times as fast as black coral. Human fingernails seem like sprinters next to black coral. Fingernails grow about 36 mm per year, more than 2000 times faster than black coral.

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The outer, growing portion is actually brightly colored. The inner skeleton of the black coral gives it its name. Unlike the hard skeletons of shallow-water reef-building coral, the black coral have flexible skeletons made of proteins and chitin, the same material as insect shells.

As they grow they lay down new layers, which helps scientists determine their age.

Over the centuries the growth layers of those skeletons record interactions between the surface and the deep sea. Chemicals trapped in the layers give scientists clues about the conditions in the oceans over the years.

“Despite living at 300 meters and deeper, these animals are sensitive to what is going on in the surface ocean because they are feeding on organic matter that rapidly sinks to the sea floor,” Prouty said.

“Deep-sea black corals are a perfect example of ecosystems linked between the surface and the deep ocean. They can potentially record this link in their skeleton for hundreds to thousands of years,” Prouty said.

But growing for 2000 years has it’s disadvantages.

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“Since longevity is a key factor for population maintenance, recovery from a disturbance to these ecosystems, natural or man made, may take decades to centuries,” Prouty said.

Coral can be damaged easily by certain oil exploration and fishing practices. It is also a valuable commodity for jewelry makers. It’s even Hawaii’s state gem.

“The flexibility and shiny luster of black coral have made it a precious commodity in the coral jewelry trade and international trade is regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora,” said Prouty.

“In fact, black corals have been harvested for centuries to create charms; the scientific name of the order to which black corals belong, ‘Antipatharia,’ comes from Greek roots meaning ‘against suffering,’” said Prouty.


IMAGE 1: Cirripathes sp. Spiral wire coral – Black coral (Wikimedia Commons)

IMAGE 2: A black coral colony showing its namesake black skeleton (Wikimedia Commons)

IMAGE 3: Begleri made of Black Coral and red coral with sterling beads. (Wikimedia Commons)