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An Antarctic Ecosystem Shows Signs of Trouble as a Tiny Worm Turns
In the freeze-dried landscape of the Antarctic Dry Valleys, ridges and rocks chiseled by the scouring winds seem frozen in time, with little evidence of change from one season to the next. But to the researchers who return there year after year, much is changing, and the change is alarming. ...The polar desert of the Dry Valleys was once thought to be sterile and lifeless. But now the valleys are known to be home to three species of nematodes, spongy mats of moss and algae in the nearby streams and frozen lakes, and an abundance of bacteria. ...Dr. Wall and her team of “worm herders” — as they are called by the helicopter pilots who ferry them to their remote field camps — study the process of carbon turnover, how carbon travels through the ecosystem.
In soil, turnover works this way: molecules containing carbon provide fuel for organisms; as the organisms die and decay, the carbon is released back into the soil in the form of nutrients. Eventually, it is exhaled out of the soil by the respiration of microbes and soil invertebrates. ...“The cycling of carbon is the basis of life,” said Ed Ayres, a postdoctoral researcher working with Dr. Wall. ...Scientists still know little about how these soil organisms function. But by digging around in what some might consider just plain dirt, the researchers are finding that one very small worm is playing a critical role in the Dry Valleys ecosystem — and that its survival may be in jeopardy.
...in the past 10 years, Dr. Wall and her colleagues have documented some striking changes in the natural laboratory of the Dry Valleys. While the temperature across much of Antarctica is rising, the Dry Valleys experienced a regional cooling period, which in turn led to cooler and drier soils. As a result, the Scottnema population has shrunk by 65 percent since 1993. This drop translates to a loss of a third of the total carbon cycling in the ecosystem. “People have said, ‘Oh well, it’s a desert, who cares?’ ” Dr. Wall said. “What we’re seeing is that the beast that has the most to do, or a disproportionate amount to do, is one species that is crashing and burning.” ...Because so little research has been done, scientists have no way of knowing whether similar disturbances are taking place worldwide. ...soils hold more carbon than trees and the atmosphere combined. Along with James Heath, a plant physiologist at Lancaster University in Britain, Dr. Wall’s colleague Dr. Ayres reported last year in the journal Science that heightened levels of carbon dioxide in the atmosphere hindered the soil’s ability to store carbon and led to increased levels of soil respiration by microbes. ... “People say: ‘What, soils? Who cares?’ But then we explain to them that engineers were counseled many times by soil scientists at L.S.U. about the unusual chemical characteristics of the soils in New Orleans and that they needed to be taken into account when they built the levees. And they didn’t.”