Antarctica is renowned for its extreme cold; yet liquid water occurs at the base of the Antarctic ice sheet, several kilometers beneath the surface. This discovery was first made in the 1970s by researchers using airborne radio-echo sounding measurements. Using both airborne and surface radar, researchers have now identified more than 145 subglacial lakes (Figure S.1), the largest of which is Lake Vostok with a surface area of 14,000 km2, similar to that of Lake Ontario. In addition, radio-echo sounding data indicate that shallow, swamp-like features the size of several city blocks, as well as water-saturated layers of soils or broken rocks, may exist beneath the ice sheet, giving rise to a wide range of subglacial aquatic environments beyond just the large lakes. All of these subglacial aquatic environments form from meltwater that develops as a result of steady geothermal heat flux from the Earth, the melting point lowering caused by the weight of the overlying ice, and the insulation of the ice sheet. Recent evidence shows that many of the subglacial aquatic environments comprise vast watersheds connected by rivers and streams that flow beneath the ice sheet.
The presence of subglacial lakes on the frozen continent has captured the interest of people, both scientists and nonscientists alike. These lakes and their connected aquatic systems are among the last unexplored places on Earth. Moreover, they have been sealed from free exchange with the atmosphere for millions of years, making it possible for unique microbial communities to exist in these environments. Scientists are excited about the opportunity to observe microbial evolution; to learn about how hydrologic systems below ice sheets are connected, how they function, and how they impact the flow of Antarctic ice; and to discover if sediments in these lakes contain evidence about the climate of the Antarctic over many millions of years, perhaps even before the continent was covered with ice.
Although much can be learned about these environments from remote sensing and ice core data, many of the key questions about these systems require that samples of water, microbial communities, sediments, and underlying rock be obtained. As of early 2007, no one had 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.
Currently, no clear protocols or standards for minimizing contamination have been established for subglacial aquatic environments, although general guidelines are provided in the Antarctic Treaty Protocol. Before sampling should proceed, specific protocols that ensure stewardship of the environment and the scientific integrity of the areas under study need to be developed, including sampling methods that minimize microbial and chemical contamination. It is critical to develop appropriate protocols now because planning for entry into these environments is already proceeding. Preparations for sampling Lake Vostok (Box 1.1 in Chapter 1) are well advanced; plans to explore subglacial Lake Ellsworth (Box 1.2 in Chapter 1) have been circulated through the international community; and two other subglacial aquatic environments are under consideration for exploration.
EFFORTS TO GUIDE SUBGLACIAL LAKE EXPLORATION
The Scientific Committee on Antarctic Research (SCAR)1 is the international body that initiates, develops, and coordinates scientific research in the Antarctic region. In response to growing scientific and public interest over the exploration of subglacial lakes, SCAR established the Subglacial Antarctic Lake Exploration (SALE) group, composed of scientists from SCAR member nations. The SCAR SALE group has provided international organizing and planning for the exploration of subglacial lake environments. The main objectives of the SCAR SALE program are to understand the formation and evolution of subglacial lake processes and environments; determine the origins, evolution, and maintenance of life in subglacial lake environments; and understand the limnology and paleoclimate history recorded in subglacial lake environments.
One of the key scientific questions posed in the SCAR SALE program concerns the origins, evolution, and maintenance of life in subglacial lakes. The SCAR SALE group speculated that life in subglacial lakes could be unique; thus any attempt to sample the water, the sediment, or the organisms directly should ensure that the subglacial aquatic environment is not contaminated, especially by carbon substrates that might perturb the aquatic ecosystem. The SCAR SALE group recommended an integrated science plan to ensure that one type of investigation does not accidentally adversely affect other investigations; that sampling regimes plan for the maximum interdisciplinary use of the samples; and that all information is shared to promote greater understanding. The SCAR SALE group continues to foster international coordination and collaboration; however, the group has not examined stewardship issues in depth.
CHARGE TO THE COMMITTEE
The National Science Foundation (NSF) has requested guidance from the National Academies to suggest a set of environmental and scientific protection standards needed to responsibly explore the subglacial lake environments found under continental-scale ice sheets. In response, the National Research Council of the National Academies created the Committee on the Principles of Environmental and Scientific Stewardship for the Exploration and Study of Subglacial Environments. Specifically, the committee was asked to (see Appendix A for the Statement of Task):
Define levels of “cleanliness” for equipment or devices entering subglacial aquatic environments;
Develop a sound scientific basis for contamination standards recognizing that different stages of exploration may be subject to differing levels of environmental concern; and
Recommend the next steps needed to define an overall exploration strategy.
The committee was also charged to consider existing technology with respect to contamination and to highlight potential needs for technological development; to identify additional scientific studies that are needed to reduce contamination; to assess
whether it is scientifically beneficial to proceed with exploration now versus later; and to identify potential targets among the many Antarctic subglacial aquatic environments. Early in its deliberations, the committee recognized that subglacial lakes are hydrologically connected to other subglacial aquatic environments including shallow, swamp-like features and thin films of water beneath the ice sheet within the same drainage basin and that the tasks assigned to the committee were applicable to other subglacial aquatic environments. The committee, therefore, considers all subglacial aquatic environments, and not just lakes per se, to be within its charge.
The issue of environmental stewardship for the exploration of subglacial aquatic environments is important to many stakeholders and interested parties, including those from the international community. This committee did not debate whether the current initiatives to explore subglacial lakes should continue, acknowledging that the scientific investigation of subglacial aquatic environments has previously been assessed internationally through the Antarctic Treaty Protocol and that exploration has been accepted as a legitimate activity. The committee recognized that the fundamental responsibility of all parties subject to the Antarctic Treaty is to maintain the best possible environmental stewardship for all activities, while appreciating, as does the Antarctic Treaty, that some impacts are acceptable in pursuit of scientific understanding and that these should be mitigated to the extent practicable.
The committee sought to develop the scientific rationale for setting standards in a manner credible to this wide range of interests. In managing any future activities it is assumed that parties will recognize, as did the committee, that limiting the science to a few sites, encouraging expert collaboration, organizing a stepwise approach, and using the cleanest available technology will all maximize the scientific outputs and minimize the impacts. The committee anticipates this rationale will provide guidance to balance the value of the scientific information to be gained against the potential for alteration of the sites being studied.
ANTARCTIC SUBGLACIAL AQUATIC ENVIRONMENTS: STEWARDSHIP AND MANAGEMENT
Although no lake has been sampled directly, Lake Vostok has been studied using remote sensing, chemical and microbiological analyses of lake water that has frozen to the bottom of the Antarctic ice sheet (accretion ice), and geochemical modeling (Figure S.2). 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 about whether 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 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).
Many types of microbes, including bacteria, yeasts, and fungal spores, are found in low abundances within the ice sheet above the lakes, and some of these microbes may still be viable as they enter the subglacial aquatic environment. 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.
Methods and protocols to minimize contamination have been developed for other unique environments, however the extreme conditions under which the exploration of subglacial aquatic environments is conducted and the logistical constraints of keeping 4 km of drilling equipment sterile pose significant challenges. For example, it is not possible to follow protocols, such as those defined for planetary protection control associated with space exploration, that virtually eliminate microbes on instruments. It may be possible initially to control the quantity of microbes associated with drilling and sampling operations, but drilling through the ice sheet, which itself contains microbes at every level, will inevitably lead to a build up of microbes on equipment and in drilling fluids.
In light of potential adverse consequences on environmental and scientific stewardship, the committee favored a conservative research approach. Until there is definitive data concerning the absence of microbial populations, it should be assumed that microbial life exists. Our current understanding of the sub-ice habitats and their inhabitants is based entirely on indirect observations that range in scope from theoretical predic-
tions to direct chemical and microbiological analyses of accreted ice samples obtained from Lake Vostok. Consequently, the committee considers the identity and diversity of life, the nature of the electron donors and acceptors that support life (if life exists), and all other related ecological and biogeochemical properties as fundamental, but unanswered, questions.
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.
CONNECTEDNESS OF SUBGLACIAL LAKES
The presence of vast connected watersheds beneath the ice sheet heightens the need for responsible environmental stewardship during the exploration of subglacial aquatic environments. If any single lake or other subglacial environment were to be altered by adding chemical contaminants or live organisms, the environments connected to the altered lake might also be changed. To minimize potential downstream contamination, responsible exploration requires a clear understanding of the subglacial hydrologic system before initial sampling is done.
GUIDELINES FOR STEWARDSHIP, MANAGEMENT, AND PROJECT REVIEW
This report provides an initial framework for the environmental stewardship for the exploration of subglacial aquatic environments. The committee offers both a set of recommendations and a decision tree (Figure S.3 and Box S.1) as a framework and sequence for the environmental management decisions that need to be made at both the international and the national levels in accordance with the Antarctic Treaty Protocol. The framework has the necessary flexibility to be updated and evolve over time as new findings accumulate about drilling and exploration methods, and the biology, and the geology of subglacial regions.
As the science and exploration of subglacial environments grows beyond its infancy, the initial methodologies and protocols recommended in this report will need further development and regular revision. All aspects of management, stewardship, and project review and approval will continue to involve absolute requirements mandated by the Antarctic Treaty, government standards specific to particular parties, and scientific standards such as those recommended by SCAR. The recommendations of the committee are thus intended for integration into this multifaceted framework.
The committee’s recommendations can be tracked in the diagram (Figure S.3). Recommendations 1 and 2 state the committee’s conclusion that carefully managed scientific research on subglacial lakes should begin while preserving the environment for future potential discoveries through a suitably conservative approach. Working through SCAR, it will be important to develop criteria and research specifications that may be incorporated into management plans for subglacial aquatic environments (Recommendations 3, 4, 6, 7, 8, 9, 10, 12). Recommendation 12 suggests an initial protocol for the exploration of subglacial aquatic environments that can be used at the national and international levels.
Recommendations for the Scientific and Environmental Stewardship for the Exploration of Subglacial Aquatic Environments
Direct exploration of subglacial aquatic environments is required if we are to understand these unique systems. Exploration of subglacial aquatic environments should proceed and take a conservative approach to stewardship and management while encouraging field research.
Exploration protocols should assume that all subglacial aquatic environments contain or may support living organisms and are potentially linked components of a subglacial drainage basin.
As soon as adequate survey data have been gathered to provide a sound basis for description, all subglacial aquatic environments intended for research should be designated Antarctic Specially Protected Areas to ensure that all scientific activities are managed within an agreed international plan and are fully documented.
As soon as adequate survey data have been gathered to provide a sound basis for description, actions should be taken to designate certain exemplar pristine subglacial environments as Antarctic Specially Protected Areas for long-term conservation purposes.
Multinational projects should be encouraged in the study of subglacial aquatic environments, and all projects aiming to penetrate into a lake should be required to undertake a Comprehensive Environmental Evaluation.
The National Science Foundation should work in conjunction with the U.S. representatives to the Scientific Committee on Antarctic Research and to the Committee on Environmental Protection to involve all Antarctic Treaty nations in developing a consensus-based management plan for the exploration of subglacial aquatic environments. This plan should seek to develop scientific understanding and ensure that the environmental management of subglacial aquatic environments is held to the highest standards.
Drilling in conjunction with sampling procedures will inevitably introduce microorganisms into subglacial aquatic environments. The numbers of microbial cells contained in or on the volume of any material or instruments added to or placed in these environments should not exceed the minimum concentration of microbes in the basal glacial ice being passed through. Based on research to date, a concentration of 102 cells/ml should not be exceeded, until more data are available.
Drilling in conjunction with sampling procedures will inevitably introduce chemical contaminants into lakes and associated subglacial aquatic environments. Toxic and biodegradable materials should be avoided, as should the introduction of non-miscible substances. At a minimum, the concentrations of chemical contaminants should be documented and the total amount added to these aquatic environments should not be expected to change the measurable chemical properties of the environment. The amount added would be expected to have a minor and/or transitory impact on the environment.
Notwithstanding their compliance with Recommendations 7 and 8, investigators should continue to make every effort practicable to maintain the integrity of lake chemical and physical structure during exploration and sampling of water and sediments.
Allowances should be made for certain objects and materials to be placed into experimental subglacial aquatic environments for scientific purposes—for example, for monitoring or tracing dynamics. These additions should follow the microbiological constraints in Recommendation 7 and include discussion of environmental risk versus scientific benefit analysis as required by the Comprehensive Environmental Evaluation.
As the initial step to define an overall exploration strategy, the United States, together with other interested parties, should begin immediately to obtain remote sensing data to characterize a wide range of subglacial aquatic environments. As a second step, preliminary data and samples should be obtained from subglacial aquatic environments as soon as practicable to guide future environmental stewardship, scientific investigations, and technological developments.
Remote sensing of the potential aquatic environments beneath the Antarctic ice sheet is underway but is far from complete. The following actions should proceed in order to make a decision about which subglacial aquatic environments should be studied in the future:
Once potential research sites are identified, the likelihood of attaining scientific goals should be evaluated based on the representativeness for other lakes and settings, for accessibility, and for the constraints of logistics and cost. The committee recognizes that plans are underway to sample Lake Vostok, and in the longer term Lake Ellsworth and Lake Concordia. The data collected from these endeavors should be used to assess whether the levels of cleanliness suggested in Recommendation 7 are appropriate.
Research and development should be conducted on methods to reduce microbial contamination throughout the drilling, sampling, and monitoring processes, on methods to determine the background levels of microbes in glacial ice and lake water, and on development of miniaturized sampling and monitoring instruments to fit through the drilling hole. The following methods and technologies need to be improved or developed:
The committee recognizes that plans are underway to sample Lake Vostok, and in the longer term, Lake Ellsworth and Lake Concordia. The data collected from these endeavors should be used to better assess the requirements of future methodologies and technologies.
Exploration will continue to be subject to formal peer review through the Antarctic Treaty protocols (notably the Comprehensive Environmental Evaluation process), as soon as adequate survey data have been gathered to provide a sound basis for description, and to include comment by SCAR where appropriate. Stewardship for the future is best addressed by establishing a dynamic multinational approach and specific scientific archive that preserves and quantifies pertinent information associated with current scientific research, nationally and internationally (Recommendations 5, 11, 12, 13). Data archiving should include detailed information about drilling components, such as the microbial content of drilling fluids and any material components that may influence future research. The establishment of a microbial archive may become an important new initiative as surface and core microbial populations are sequenced and where possible, identified.
The exploration of subglacial aquatic environments is in its initial stages, with fundamental questions remaining to be answered about these unique environments. Much debate and speculation have occurred based on the limited data available; no definitive answers will be forthcoming until these environments are sampled directly. The existence of these environments on the Antarctic continent makes them a part of the common heritage of all humankind. Accordingly, the management of subglacial aquatic environments requires responsible environmental stewardship while allowing field research in accordance with the Antarctic Treaty. Although this study is being produced by a U.S. scientific advisory body and the National Science Foundation requested the study to guide scientific programs originating in the United States, the committee hopes that its multinational makeup will be recognized and that the recommendations in this report will serve as a basis for broad international discussion about environmental stewardship for the exploration of subglacial aquatic environments.