Molecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica

• Main Authors: Yung, Cheuk-man., 容卓敏.
• Other Authors: Pointing, SB
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Hong Kong (Pokfulam, Hong Kong)
• Subjects: Molecular ecology - Antarctica - McMurdo Dry Valleys; Microbial ecology - Antarctica - McMurdo Dry Valleys; Rocks - Antarctica - McMurdo Dry Valleys; Antarctic; East Antarctica; McMurdo Dry Valleys; Miers; Miers Valley; Antarc*; Antarctica
• Online Access: https://doi.org/10.5353/th_b4784999; http://hdl.handle.net/10722/174557

The McMurdo Dry Valleys comprise some 4,800km2 of ice-free terrain in east Antarctica and this constitutes the coldest and most arid desert on Earth. The ecosystem of the Dry Valleys is characterized by microbial processes since environmental extremes severely limit higher plant and animal life. A major international collaborative research effort co-ordinated by the International Center for Terrestrial Antarctic Research (ICTAR), identified long-term study sites representative of maritime and inland Dry Valleys environments. The maritime site, Miers Valley, has been the subject of intensive multi-disciplinary study in recent years, of which the work in this thesis is a part. Previous studies have identified soil microbial communities and their putative functional roles, but lithic communities have not been previously appreciated. This thesis reports aspects on the biodiversity and ecology of lithic microbial communities in Miers Valley. A survey of terrain revealed extensive weathered granite, but no porous sandstone or limestone rocks more commonly associated with cryptoendolithic communities (those colonizing pore spaces within rock substrates). Granite was extensively colonized (30-100% of available substrate) by chasmoendolithic microorganisms (colonizing cracks and fissures in weathered rock). Visual examination of colonized rocks revealed a distinct zone of biomass 2-5mm below the rock surface, and this was overlain by a weathered and friable matrix of rock. Microscopy revealed a community dominated by diverse cyanobacterial morphotypes, plus other unidentifiable microbes of varied morphology. A quantitative approach to broad-scale community fingerprinting was adopted, utilizing terminal restriction fragment length polymorphism (TRFLP) and sequence based identifications of restriction fragments. The multi-domain approach encompassed Archaea, Bacteria and Eukarya. The results revealed relatively low species richness (0.6-1.8) for each domain with community richness estimates also relatively low (<3). ...