A blue-ice ecosystem on the margins of the East Antarctic ice sheet

Freezing temperatures, desiccation and high levels of solar radiation make the surface of the Antarctic ice sheet one of Earth's harshest habitats. However, our study in the Vestfold Hills area of East Antarctica shows that favourable conditions for microbial production become established just beneath the surface of blue-ice areas, which collectively cover about 2% of the ice-sheet periphery. Their translucent, wind-polished surface allows solar heating to create meltwater in a greenhouse-type environment at depths of up to 1m. Melting is intensified around dark debris particles, or cryoconite, where we found microbiological activity to be greatest. Rates of photosynthesis (average 2060 ngC (g cryoconite)-1 d-1) were adapted to low light intensities (~10% of surface irradiance values) and most likely dominated by cyanobacteria and Chloroplastida. A heterotrophic bacterial community was also found to be active within the cryoconite, although average bacterial growth rates (5.7 ngC(g cryoconite)- 1 d-1) were far lower than average community respiration (1870 ng C(g cryoconite)-1 d-1). The majority of the respired carbon was most likely associated with the autotrophs and several protists. Therefore, blue-ice areas constitute oases for microbial life around the periphery of Earth's coldest ice sheet.