Ecological niches of Antarctic phototrophic communities during global glaciation

Abstract

According to paleontological data, large scale, global glaciations occurred repeatedly over the history of Earth. Such glaciations unavoidably resulted in a sharp decrease in the number of habitats suitable for development of phototrophic microorganisms, which mostly require sunlight. Molecular data indicate that some groups of Antarctic phototrophic microorganisms emerged before formation of the Antarctic ice sheet (30-45 Ma) and probably survived the subsequent glaciation maxima. Analysis of the data on the present day occurrence of phototrophs in Antarctica revealed the presence of liquid water in a habitat to be the key factor for survival of phototrophic communities. At negative air temperatures, this requirement may be met either in warmer microniches (0 to 30°C and higher) or in brines with freezing temperatures below zero (to -52°C). Development of phototrophic communities in such habitats may indicate the theoretical possibility of existence of the niches favoring growth of phototrophic microorganisms during Precambrian global glaciations. This possibility should be considered in paleontological reconstructions of development of life on Earth.