The Arctic tundra would not appear a welcoming environment for life. But a paper published today in the journal Nature suggests that polar deserts may house photosynthetic organisms in a very unlikely place--under rocks. The discovery of the photosynthetic cyanobacteria could potentially double estimates of the carbon sequestration potential in these extreme environments.

Charles S. Cockell and M. Dale Stokes of the British Antarctic Survey surveyed some 850 rocks on two islands in the Canadian High Arctic, where vegetation covers less than 2 percent of the land. The researchers discovered that more than 90 percent of the rocks were colonized with life. Because the cyanobacteria require light to survive, the finding was surprising. But as Cockell explains, We found that in fact the opaque rocks protect the micro-organisms and the movement of the rocks during the annual freeze-thaw allows crack to form and light to penetrate beneath the surface. When the team searched terrain in the Antarctic that was formed by glaciers freezing and thawing, it found 100 percent colonization near the edges, whereas only 5 percent of the rocks near the center--which receive less light--harbored bacteria.

The scientists also estimated how much carbon the newly discovered bacteria could take up and determined that its productivity was nearly equal to that of the surface plants, including lichens and mosses. This shows us that places we may think of as extreme--for example other planets like Mars--could nurture surprising habitats for life," Cockell remarks.