New dating finds oldest coral yet

From Boston, at a meeting of the American Association for the Advancement of Science

A black coral collected near the Hawaiian Islands may set a new record for age among coral kind: some 4,200 years.

The meter-plus-tall specimen of Leiopathes glaberrima turns out to be older than corals previously studied by Brendan Roark of Stanford University and his colleagues. The team used submersible vehicles to pluck a few Hawaiian corals from deep water. The researchers determine the coral ages by radiocarbon dating, based on the known decay rate for carbon-14. In 2006, the group reported that a sample of a Gerardia species, one of the gold corals prized for jewelry, had lived around 2,700 years.

Deep-sea corals are often blithely described as long-lived, but there’s little hard evidence, Roark says. His team measured the carbon-14 in the black coral’s distinctive hard skeleton, a flattened branching tree structure created by generations of the hundreds of tiny, soft-bodied polyps that make up a single coral colony.

The ancient L. glaberrima came from a depth of 400 meters, below the reach of sunlight. The skeleton had grown less than 5 micrometers a year. Its polyps, like those of other deep-water corals, snagged food bits from the water instead of relying on the live-in photosynthetic algae that nourish corals in shallow, sunny water.

The black coral’s age fuels Roark’s hopes of using old corals as what he calls an “archive of climate changes.” Also, the age highlights concerns about trawling fisheries that smash through coral beds. “These are not renewable resources,” he says.