VOA常速英语:Researchers Find Deep-Sea Corals More Than 4,000 Years Old

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A research team led by Texas A&M University has discovered corals off the coast of Hawaii that are more than 4,000 years old, making them among the oldest living creatures on earth.

During a series of recent deep-ocean dives in a submersible craft, Texas A&M oceanographer Brendan Roark and his colleagues discovered the oldest examples ever found of two species of shrub-like corals called Leiopathes and Gerardia, commonly known as black and gold coral, respectively.  

Roark says the species are the largest structures in the deep-sea coral bed.

"They certainly are an aggregation point for other invertebrates and potentially fish," he explains.

Reporting this week in the Proceedings of the National Academy of Sciences, Roark says he and colleagues from the University of California-Santa Cruz and Australian National University in Canberra collected samples of the coral from depths of nearly 400 meters. Then, using radio-carbon dating, they determined their age, which Roark says was much older than reported in previous estimates.

The Leiopathes is now confirmed to be about 4,265 years, he says, and the Gerardia believed to be about 2,742. The age of the coral would rank them among the oldest living creatures in existence. Scientists know that some of the Bristlecone pines in Northern California are also more than 4,000 years old.

Roark says the age of the corals would determine how quickly the ecosystem could recover. And, he adds, "It's going to play a role in ecology and biology, both the ecology of that ecosystem and the biology of those individual organisms."

Deep sea corals face a multitude of threats, including illegal harvesting, drag-net style commercial fishing, climate change, human pollution and acidification from accumulated carbon dioxide in the atmosphere. Roark says the long-lived corals are important not only because they support many other forms of marine life, but because they also open a window on the ocean's ancient history.

"With such long life there exists the potential to reconstruct past ocean conditions, in particular with these species, to reconstruct the past ocean surface productivity."

The discovery adds to what we know about the changing climate, he says, "and how fast and how much CO2 can be cycled out of the surface ocean into the deep ocean."   

Roark hopes further study of the ancient coral will shed new light on complex ocean dynamics and help to guide new policies to protect these fragile marine organisms.