Monday, October 13, 2008

Precious corals millenia old

Hawai'i's precious deep-water corals are not only precious, but they are among the oldest living things in the Islands.

(Image: Black Coral growing, this one in the Gulf of Mexico. It's the skeleton that's black. NOAA Credit: NURC/UNCW and NOAA/FGBNMS)

The oldest corals were growing in Island waters long before the first humans arrived.

Some black corals--in this case the species Antipathes glaberrima--may be as much as 4,000 years old.

Some gold corals may date back 2,700 years.

Hawai'i ocean researcher Rick Grigg said these corals, which grow more than 1,000 feet deep, have not been a part of the Hawaiian black coral harvest.

"The sample is NOT the black coral used in the Hawaii coral industry. Those black corals are Antipathes dichotoma and Antipathes grandis. They grow 5-6 cm/yr (about two inches) and are found between 30-100 m (100 to 300 feet) depth and are harvested by SCUBA divers. This fishery has been going since 1958. The divers take about 3% per year and the population appears to have been sustainable over this long period (50 yrs)," Grigg said in an email.

Some early coral age estimates were based on the assumption that growth rings on corals are produced annually, like those of trees, but new radiocarbon research suggests that's not the case.

Early estimates were that gold corals could grow more than two inches a year, according to an amendment to the precious corals fishery management plan produced this year for the Western Pacific Regional Fishery Management Council. In fact, the growth rate may be a small fraction of a hundredth of an inch per year. Or, viewed another way, something like an inch of growth every 700 years or so.

The upshot is that if you harvest it, it doesn't grow back anytime soon, according to researchers from Stanford University and the Laurence Livermore National Laboratory. They used submersibles to collect deep-sea corals and used radiocarbon dating to determine their venerability.

This can only be seen as bad news for Hawai'i's precious coral industry, which has been troubled for some time by a range of things.

Regulators have placed increasingly strict rules on the harvesting of corals. Divers have been reporting that coral beds recently have been overgrown by an aggressive invader called snowflake coral. Additionally, research shows that coral beds may be significant forage areas for endangered monk seals.

The researchers, led by Stanford's Brendan Roark, argue for a local and federal ban on the harvesting of the oldest corals, on the grounds that they can't replace themselves on any reasonable time scale and any level of harvesting is unsustainable.

From a scientific standpoint, Roark said the corals can be extremely valuable, since their hard skeletons may contain information about the changes in the world's oceans over the past four millenia.

They could, in fact, be the archives of the ocean, he said.

“These organisms are the equivalent of the bristlecone pine in the deep ocean,” Roark said in a press release from Stanford.

©2008 Jan TenBruggencate

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