ABSTRACT
Spread across the Arctic, Antarctic, and Alpine regions of our world, the cryosphere lakes of our planet are most likely an ancient and vital key for the persistence of life on Earth. Strong evidence continues to accumulate indicating that the Earth has been completely covered with ice for 10 million years or more on at least two occasions in a process now known as “Snowball Earth” (Kirschvink et al., 2000). During these periods of massive global glaciation, icy microbial ecosystems would have served as the central reservoir for life, including the photosynthetic primary producers such as the cold-tolerant cyanobacteria (Vincent and Howard-Williams, 2000; Priscu and Christner, 2004). The microbial communities inhabiting this cryosphere would have already adapted and evolved in the annual miniature version of the global Snowball Earth. To survive in one of the most hostile, extreme environments on Earth, to deal with high ultraviolet radiation loads, freeze-thaw cycles, and organic resources dependent over the long term on photosynthetic primary production, these communities would contain the elite specimens of terrestrial evolution (Tranter et al., 2004).
