Abstract:
The study of high temperature extreme environments continues to challenge our understanding of the upper tolerances of microbial life and how life may have originated on earth and possibly other planets. The Tramway Ridge geothermal site on Mt. Erebus, an active volcano in Antarctica, is the most geographically isolated geothermal site on earth providing an excellent system for studies of ... microbial speciation, biogeography, and evolution of thermal adaptation. Recent advances in high throughput DNA sequencing and bioinformatics allow us to acquire and decipher the genetic capabilities and structure of entire microbial communities without the necessity of cultivation. Employing a combination of these advanced genetic methods coupled with culture dependant approaches a gene-centric analysis of the Tramway Ridge microflora and other Antarctic geothermal sites was undertaken to address questions focused on endemism, biogeography, evolution, and adaptation. Soil samples and bacterial isolates were collected from high temperature soils (maximum temperature sites) at Tramway Ridge and western crater locations at Mt Erebus. These temperatures averaged 65°C and were dominated by steam emissions. Samples have been obtained both for DNA/RNA genetic analysis and for cultivation. Cultivation efforts were undertaken on site and have been continued successfully in the lab. Ice core samples were also collected from walls of several ice chimneys. Temperature probes were installed in the high temperature soils at Tramway Ridge. The temperature probes and data loggers were left in situ to obtain temperature data over a one year period at each site. Temperature, Depth, Water Activity and Oxygen saturation was measured in field. Salinity, pH, moisture content, nutrients and elemental analysis were determined post-field.
In the 2010-2011 field season, we expanded our set of study sites to include several ice caves, ice chimneys and ice hummocks found on the slopes of Mt. Erebus. In addition to the expansion of sites on Erebus, we also travelled to Mt. Melbourne and Mt. Rittman (Terra Nova Bay) to identify sampling sites within these features for comparison to Tramway Ridge.
On Mt. Erebus we deployed 19 temperature loggers, distributed around the main crater and flanking ice chimney fields to remain in the field overwinter, effectively constituting a volcano-wide temperature experiment. This will determine whether temperature fluctuations in different areas of the volcano are correlated to one another.
Soil samples from 21 different sites were successfully sampled with 12 from Tramway and 9 from other locations around Erebus. All sites from Tramway had been depth profiled with 9 new samples collected and 3 old sites re-sampled. Having collected a significant number of samples from wide ranging locations allows for a robust bio geographical study to be carried out and identification of more interesting site for potential sampling to focus on in future studies. Offsite soil collection included samples from within the western crater, ice chimneys, ice caves and Mt. Melbourne and Mt. Rittman. We now have samples collected from each of the three known geothermal features of Antarctica during the same field season. These samples will be utilised for biological and geochemical comparative analysis. Ice cores were aseptically collected by drilling into the side of an ice chimney with an ethanol-sterilized corer. Cores were immediately placed into ethanol-sterilized plastic bags and placed in cold storage. The cores will be kept frozen until they are sampled aseptically. Portions of the core will be melted and used for DNA extraction. Other portions will be used for geochemical characterization. Together these data will provide a detailed history of the biology and chemistry of the ice chimney over time.
The primary objective for 2012 was to recover temperature loggers deployed last season. We also collected hot soil samples at Tramway and from the sites of temperature logger recovery for comparative analysis. In the field, we measured temperature of soil, water content and Oxygen concentration of subsurface gasses. We also collected ice cores from the side of ice chimneys to study bacteria associated with ice chimney formation.
Soil samples were collected from the temperature logger sites using sterile spatulas and containers. Temperature and water content data were collected using Hand-held CheckTemp1 temperature and Hydrosense probes, respectively. Oxygen was measured by drawing subsurface gasses into a chamber containing an oxygen sensor. The ice cores were collected using an ice drill. Temperature loggers deployed in 2010-2011 were collected.
This season we repeated oxygen measurements to establish whether the levels observed last year are constant or whether they fluctuate. Since oxygen concentrations are expected to have a profound impact on structuring microbial communities, our oxygen data provides a clue as to why the community structure differs at depth.
