File Download
  Links for fulltext
     (May Require Subscription)
Supplementary

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

TitleMolecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica
Authors
Advisors
Advisor(s):Pointing, SB
Issue Date2012
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Yung, C. [容卓敏]. (2012). Molecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4784999
AbstractThe 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). Nonetheless very clear and statistically supported patterns in the occurrence of phylotypes within chasmolithic communities were related to aspect (which strongly affects temperature and moisture availability in Dry Valleys locations). The bacterial assemblages formed two groups (cold-dry south facing slopes and valley floor moraine). The eukaryal assemblages also formed two groups although here the moraine samples grouped with the warmer wetter north facing slope and the cold-dry south facing slope assemblages formed a separate group. The archaeal assemblages displayed no difference within different valley terrain. Extensive sequence based interrogation of community structure using clone libraries revealed a community dominated by cyanobacteria, Actinobacteria, Deinococci and putative lichens. These phyla are all known for their extreme tolerance to desiccation and occurrence in arid landscapes. Phylogenetic analysis revealed that these abundant taxa shared close affiliation with those from other Antarctic refuge niches such as hypoliths and cryptoendoliths. The cyanobacteria were mainly Oscillatoriales, but other genera such as Chroococcidiopsis and Nostoc commonly recovered in hot desert lithic communities were generally absent. The eukaryal community was dominated by chlorophyte algae, whilst the archaeal phylotypes were a diverse collection spanning both euryachaeal and crenarchaeal lineages. Overall the data revealed the chasmoendolithic community in Miers Valley was widespread and with relatively restricted diversity. The selection pressures related to topology of the valley have resulted in different community structure within the valley.
DegreeMaster of Philosophy
SubjectMicrobial ecology - Antarctica - McMurdo Dry Valleys.
Molecular ecology - Antarctica - McMurdo Dry Valleys.
Rocks - Antarctica - McMurdo Dry Valleys.
Dept/ProgramBiological Sciences

 

DC FieldValueLanguage
dc.contributor.advisorPointing, SB-
dc.contributor.authorYung, Cheuk-man.-
dc.contributor.author容卓敏.-
dc.date.issued2012-
dc.identifier.citationYung, C. [容卓敏]. (2012). Molecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b4784999-
dc.description.abstractThe 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). Nonetheless very clear and statistically supported patterns in the occurrence of phylotypes within chasmolithic communities were related to aspect (which strongly affects temperature and moisture availability in Dry Valleys locations). The bacterial assemblages formed two groups (cold-dry south facing slopes and valley floor moraine). The eukaryal assemblages also formed two groups although here the moraine samples grouped with the warmer wetter north facing slope and the cold-dry south facing slope assemblages formed a separate group. The archaeal assemblages displayed no difference within different valley terrain. Extensive sequence based interrogation of community structure using clone libraries revealed a community dominated by cyanobacteria, Actinobacteria, Deinococci and putative lichens. These phyla are all known for their extreme tolerance to desiccation and occurrence in arid landscapes. Phylogenetic analysis revealed that these abundant taxa shared close affiliation with those from other Antarctic refuge niches such as hypoliths and cryptoendoliths. The cyanobacteria were mainly Oscillatoriales, but other genera such as Chroococcidiopsis and Nostoc commonly recovered in hot desert lithic communities were generally absent. The eukaryal community was dominated by chlorophyte algae, whilst the archaeal phylotypes were a diverse collection spanning both euryachaeal and crenarchaeal lineages. Overall the data revealed the chasmoendolithic community in Miers Valley was widespread and with relatively restricted diversity. The selection pressures related to topology of the valley have resulted in different community structure within the valley.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.source.urihttp://hub.hku.hk/bib/B4784999X-
dc.subject.lcshMicrobial ecology - Antarctica - McMurdo Dry Valleys.-
dc.subject.lcshMolecular ecology - Antarctica - McMurdo Dry Valleys.-
dc.subject.lcshRocks - Antarctica - McMurdo Dry Valleys.-
dc.titleMolecular ecology of chasmoendolithic environments in Miers Valley, McMurdo Dry Valleys, Antarctica-
dc.typePG_Thesis-
dc.identifier.hkulb4784999-
dc.description.thesisnameMaster of Philosophy-
dc.description.thesislevelMaster-
dc.description.thesisdisciplineBiological Sciences-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b4784999-
dc.date.hkucongregation2012-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats