Exploration of Antarctic Subglacial Aquatic Environments: Environmental and Scientific Stewardship (2007)Polar Research Board
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Antarctica is renowned for its extreme cold; yet surprisingly, radar measurements have revealed a vast network of lakes, rivers, and streams several kilometers beneath the Antarctic ice sheet. Sealed from Earth's atmosphere for millions of years, they may provide vital information about microbial evolution, the past climate of the Antarctic, and the formation of ice sheets, among other things. The next stage of exploration requires direct sampling of these aquatic systems. However, if sampling is not done cautiously, the environmental integrity and scientific value of these environments could be compromised. At the request of the National Science Foundation, this National Research Council assesses what is needed to responsibly explore subglacial lakes. The report concludes that it is time for research on subglacial lakes to begin, and this research should be guided by internationally agreed upon protocols. The report suggests an initial protocol, which includes full characterization of the lakes by remote sensing, and minimum standards for biological and other types of contamination.
- Although no lake has been sampled directly, Lake Vostok has been studied using remote sensing, chemical analyses of ice accreted to the bottom of the Antarctic ice sheet, and geochemical modeling.
- Another problem is that the accreted ice excludes all gases, most of the dissolved material, and many of the particles when it froze. We do not know the partition coefficients for ice forming under these conditions.
- Because it is possible that the concentration and type of microbial cells and organic nutrients may differ from sample to sample, the absence of viable microbes cannot be excluded until adequate sampling is done. It will be necessary to collect samples from several different locations not only within a lake but also within different lake systems. Even when freshly collected samples are available, it will be important to verify all measurements by analyses at several independent laboratories.
- Currently, no clear protocols for environmental stewardship or standards for minimizing contamination have been established for subglacial aquatic environments beyond the general guidelines of the Antarctic Treaty.
- Despite the initial investigations of Lake Vostok, great uncertainty remains about many basic physiochemical parameters, such as salinity and concentration of dissolved gases, especially in the deeper waters of the lake.
- In addition, questions about the presence of microbial populations and about their growth, diversity, and uniqueness cannot be answered until the subglacial waters and sediments are sampled directly.
- In light of potential, adverse consequences for environmental stewardship, the committee favors a conservative approach where it is assumed that actively growing microbial populations in the subglacial environments are present until proven otherwise.
- Many types of microbes, including bacteria, yeasts, and fungal spores, are found in low abundances within the ice sheet and some of these microbes may still be viable as they enter the subglacial aquatic environment. These liquid-water systems may also contain low levels of microbial nutrients.
- No one has yet drilled into a lake; thus, the next challenge in the exploration of subglacial aquatic environments is to determine the best way of drilling into, sampling, and monitoring these environments.
- Results of these analyses suggest that the upper waters in the lake have a low salinity and possibly extremely high concentration of gases such as oxygen.
- We cannot yet determine the chemical and microbial concentrations of the lake water by analyzing chemical and microbial concentrations in the ice accreted above the lake surface.