On an island called Signy, amid the rolling waves off Antarctica, lies a moss bank as old as the Roman Empire.
Buried deep within its frozen, brown remains, scientists have revived a spark of life that has endured for well more than a thousand years.
The discovery made by researchers from the British Antarctic Survey and the University of Reading, Berkshire, U.K., pushes back by many centuries the time span over which frozen ancient plants are able survive, to be revived by nothing more complex than exposure to light.
"It's basically the first record of anything regenerating of that sort of age," said the survey's Peter Convey, co-author of the report in Current Biology. "There are records of microbes being pulled out of ice cores and permafrost, but nothing that's multicellular has ever been recorded to do it."
On the island, located about 850 miles southeast of South America's Cape Horn and a few hundred miles northeast of the tip of the Antarctic Peninsula, the researchers excised a 4.5-foot (1.4-meter) core from the moss bank. Though surrounded by icebergs, Signy Island lies at about the same latitude as Stockholm, Sweden, and St. Petersburg, Russia.
Back at the lab, the scientists sliced the core lengthwise into 8-inch (20-centimeter) pieces and then crosswise in half. They placed the halves in sealed containers and exposed them to the light and temperature levels that would be found at the moss's home.
To their delight, the visibly intact remains of mosses deep in the core sprouted new green fuzz at various depths in about three to six weeks. They sampled the brown stems from which the new growth sprang and sent the samples to a carbon-dating lab.
The result? The regenerating stems closest to the core's bottom had last grown during the twilight of Rome, about A.D. 300-450.
Dana Bergstrom of the Australian Antarctic Division, who was not involved in this study, said she was amazed and delighted by the discovery. "Life emerging from the ice is usually confined to animated movies," she said in an email.
Convey said he was fairly certain the growth did not come from contamination by wayward moss spores for several reasons: The team carefully wrapped the cores and cut them only with clean saws in the lab; the species of moss in the core does not produce spores in the Antarctic; and only one species was observed in the regrowth, the same one as in the core.
"Ultimately, it's circumstantial," Convey said, "[but] all the circumstantial evidence points to the regrowth being real, as distinct from some sort of contamination."
This is not the oldest resurrection of a frozen plant in the laboratory, although it is perhaps the simplest. The regrowth of a flowering plant called Silene stenophylla from Siberian permafrost frozen about 31,800 years ago required complex laboratory gymnastics. The scientists cloned tissue from the seed and then grew it on special laboratory food.
And new growth has emerged from moss stems that were released from about 400 years of confinement under the Teardrop Glacier on Canada's Ellesmere Island.
When samples from these defrosted mosses were taken into the lab, ground up, and spread on potting soil on lab plates and watered, new mosses sprouted, radically changing ideas about the supposed tabula rasa left in the wake of retreating glaciers.
The new discovery pushes back the date mosses are known to have survived freezing further still and expands the feat to a new moss species.
"Their study and our study really does talk about the resilience of these primitive land plants and how they are very critical in reviving landscapes," said Catherine La Farge of Canada's University of Alberta, author of last year's Teardrop Glacier study.
"They can be revived. They can regenerate. And I think that's really cool."
She noted, however, that unlike the mosses released from Teardrop, the resurrected moss from Signy Island had been buried deeply in the ground, so this sort of regrowth from long-frozen material would not take place naturally unless it was exposed by catastrophe.
There is no telling how long mosses might ultimately prove able to survive under favorable deep-freeze conditions. La Farge has plans to push moss's regenerative record back even further and challenge S. stenophylla's title. Her team is planning a trip to Canada's Baffin Island to collect and attempt to regrow mosses more than 50,000 years old.
"I would not be surprised if they are able to regenerate," La Farge said. "It's built into their biology."
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