From "valley of the dead" to "vibrant ecosystem" - the evolution of our understanding of life at the edge

Discovered by RF Scott's expedition team in 1909, the McMurdo Dry Valleys (MDVs) of Antarctica were thought to be lifeless. A decade later, a team of geologists noted "laminae of algae" in water bodies. In the 1960s, several science groups initiated biological studies of the MDV ice-covered lakes and ponds, and subsequently the streams. In the late 1980s, microinvertebrates in the MDV soils were discovered and since the 1990s, life in the MDV glaciers has been explored such that an understanding of the biotic and abiotic connections between each of these landforms is beginning to emerge. This harsh environment, with mean annual air temperatures of -18^oC and less than 10 cm snow water equivalent per year, defined what most expected to be the edge of livable conditions on Earth. However, the biota of the MDVs polar desert ecosystem have adapted to survive the extreme cold and dry conditions. Streams flow for 8-12 weeks per year, and yet benthic algal mats persist, in place, through the winter waiting for water the following season. Soil invertebrates tolerate intracellular freezing or go through anhydrobiosis to survive the harsh winters. Life in the ice-covered, closed basin lakes, however, continues without pause through the summer and winter. The evolutionary and ecological responses of this ecosystem to extremes in environmental variation have re-shaped our understanding and expectations of life on Earth and beyond.