Preserved in an Icy Tomb, a Plant Returns From the Dead
Melting glaciers in Canada have unearthed some rare emerald treasures: moss-like plants known as bryophytes, captured and frozen in time. When the plummeting temperatures of the Little Ice Age that began in AD 1550 and tapered off in 1850 sent glaciers surging across the Canadian landscape, these plants were held captive, along with many others, beneath the ice. By any logic the bryophytes should have withered there, since tests showed the plant samples had been frozen for over 400 years. But when researchers from the University of Alberta, Canada noticed patches of green in spots where recent glacial melt had occurred, they had a hunch that these plants were in fact powerful fighters.
The site of their discovery was the Teardrop Glacier on Ellesmere Island, northern Canada. The glacier has been struck in recent years by warming temperatures, suffering a three to four meter drop each year since 2004. So far, it has declined by 650 feet, and as it has shifted it has exposed swathes of land vegetated by plants that last lived before the Little Ice Age hit. Except, that is, for the bryophyte plants, which were still very much alive.
The researchers released their findings in a paper published in the journal, Proceedings of the Natural Academy of Sciences. Lead researcher Catherine La Farge told BBC News that “We ended up walking along the edge of the glacier margin and we saw these huge populations coming out from underneath the glacier that seemed to have a greenish tint.”
Upon a closer inspection in a laboratory, the researchers found that the brownish, frozen parts of the bryophyte samples (which they also carbon dated to show that they were 400 years old) appeared to be giving rise to fresh green shoots. “When we looked at them in detail and brought them to the lab, I could see some of the stems actually had new growth of green lateral branches, and that said to me that these guys are regenerating in the field, and that blew my mind,” La Farge told the BBC. They were also able to show that the age-old plants could revive themselves in nutrient-rich soil within petri dishes in the lab, the Surprising Science blog at Smithsonian.com reported.
Bryophytes are structured in a way that might have worked to their benefit in this scenario. They lack a vascular system for pumping nutrients and fluids around the plant, meaning they are better suited to resurrection after long, chilly winters that leave the plants dried out. Furthermore, Surprising Science explains that bryophytes
grow clonally, so each of their cells can reproduce and then differentiate into any sort of cell that makes up the organism (a quality called totipotency). Additionally, microscopic analysis of the cells of the blackened, seemingly dead plants showed that their structural integrity had been well preserved by the ice, which in some cases left cell organelles and other tiny structures intact.
Moss is a kind of bryophyte that is renowned for lasting a long time without water or nutrients. “After a hundred years, a moss may look perfectly natural and even retain its green color,” Jonathan Shaw, a scientist at the bryology lab at Duke University told NPR. But surviving beneath ice for 400 years is a different feat.
“If you think of ice sheets covering the landscape, we’ve always thought that plants have to come in from refugia around the margins of an ice system, never considering land plants as coming out from underneath a glacier,” La Farge told the BBC. Certainly, they had never imagined a plant surviving quite as long beneath the ice.
But now their research suggests there are new ways a landscape might regenerate and repopulate itself with vegetation during climate change—especially since bryophytes weren’t actually the only plants discovered in the melting glacier’s wake. There were also green algae, and cyanobacteria, for example. “It’s a whole world of what’s coming out from underneath the glaciers that really needs to be studied,” La Farge said to the BBC. Amid global warming’s general doom and gloom, stories like this might yield some necessarily hopeful clues about how some species could benefit from climate change.