Characterisation of microbial Mat communities in meltwater ponds of the McMurdo ice shelf, Antarctica

• Main Author: Jungblut, Anne Dorothee
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UNSW, Sydney 2007
• Subjects: Microbial mat communities; Cyanobacteria; Diversity; Antarctica; Nitrogen fixation; Cyanobacterial toxins; Microcystin; Lipid biomarkers; Microorganisms > Antarctica; Microbial populations > Antarctica; Melt ponds > Ecology > Antarctica; Bratina Island; McMurdo Ice Shelf; Antarc*; Ice Shelf
• Online Access: http://hdl.handle.net/1959.4/40496; https://unsworks.unsw.edu.au/bitstreams/0145ffb0-1e41-49d9-a3ce-3432e7d971af/download; https://doi.org/10.26190/unsworks/17418

The investigation presented in this thesis examined the microbial and functional diversity of the meltwater ponds Fresh, Orange and Salt Ponds on the McMurdo Ice Shelf, near Bratina Island, Antarctica. These sites were chosen because of the ecological importance and absence of detailed characterisations of their diversity and function as part of Antarctica's largest wetland. Particular focus was on cyanobacterial diversity, nitrogen fixation and secondary metabolite production. Using 16S rRNA gene and morphological analysis a large diversity of cyanobacteria (more than 22 phylotypes) was identified with high phylogenetic similarities (up to 99% sequence identity) to cyanobacteria from mats in other regions of Antarctica. In addition biogeographical distributions were identified including potentially endemic and cosmopolitan cyanobacteria. High salinities were also connected to the change and reduction of diversity. Lipid marker analyses were performed targeting hydrocarbons, ether-linked hydrocarbons, methylated fatty acid esters (FAME), wax esters, hopanols and sterols. Lipid biomarker profiles were similar to typical cyanobacteria dominated mats with major input from microorganisms including oxygenic and anoxygenic phototrophs, obligate aerobic and anaerobic heterotrophs that conduct the metabolic processes of fermentation, sulphate reduction, sulphate and iron-oxidation, methanogeneses. Signature lipids indicative of Chloroflexus and archaea, as well as branched aliphatic alkanes with quaternary substituted carbon atoms (BAQCs), were identified for the first time in Fresh, Orange and Salt Ponds. Based on nifH gene analysis, the nitrogen fixing diversity characterised in Orange Pond consisted of cyanobacterial Nostoc sp. as well as firmicutes, beta-, gamma- and delta-proteobacteria. Acetylene reduction assays and nifH gene RNA transcript diversity identified Nostoc sp. as a main contributor of nitrogenase activity in these ponds. Furthermore, analytical methods were used to identify the cyanobacterial ...