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Exploration of Antarctic Subglacial Aquatic Environments: Environmental and Scientific Stewardship
Both Russian-led and U.K.-led consortia have followed the current protocols for scientific research on these lakes and have addressed issues brought forth through the Antarctic Treaty Protocol. These groups have had discussions with SCAR SALE and have satisfied their respective national science protocols. The purpose of this study is to provide independent guidance on how to minimize contamination of subglacial lake environments during exploration and how to provide responsible stewardship of these unique and possibly connected environments.
NEXT STEPS IN SUBGLACIAL EXPLORATION
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. 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. Lake Vostok has been isolated from the atmosphere for more than 15 million years (Christner et al. 2006); the water, which flows very slowly through the system, is estimated to reside in the lake on the order of tens of thousands of years.
There is some controversy in the peer-reviewed literature whether or not there are microorganisms living in Antarctica’s subglacial lakes. The controversy is due mainly to the fact that there are currently no samples of lake water, only accreted ice. Based on published reports, the number of microbial cells in the accreted ice of Lake Vostok may be as high as 10,000 or as low as a few recognizable cells per milliliter. The water may also contain low levels of microbial nutrients, necessary to support microbial communities; estimates of dissolved organic carbon (DOC) concentrations range from undetectable to 250 µmol L−1, the latter being well above concentrations in the open ocean (typically about 70 µmol L−1).
It should be noted that 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. As a result, despite the pressure and temperature regime of the subglacial environment, there is a possibility of microbial metabolism and growth. Rates of both growth and evolution are expected to be slow in these environments.
Microbial cells and organic nutrients may be heterogeneous from sample to sample, but until a fresh sample of water is collected using precautions to avoid chemical and microbiological contamination, we will not know for sure. Even when freshly collected samples are available, it will be important to certify all measurements preferably by cross-calibrated measurements from several independent laboratories. Chemically, subglacial aquatic environments can be expected to vary widely from site to site, and the complete absence of viable microbes cannot be excluded until adequate sampling is done. However, from a scientific perspective, extreme oligotrophic environments are themselves unusual, interesting, and worthy of study.
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. Current understanding of the sub-ice habitat and its inhabitants is based entirely on indirect observations that range in scope from theoretical predictions to direct chemical and microbiological analyses of accreted ice samples obtained from Lake