Lake Vida is the largest lake of the McMurdo Dry Valleys, and yet remains one of the least studied. However, it is known that this lake has a ~20 m ice cover overlaying a brine of unknown depth with at least 6 times seawater salinity and temperatures below -10 ºC year-round. It is also known that this brine has been isolated for 2,800 years. Thick sediment layers high in the ice cover fully block light penetration, insuring that any ecosystem in the brine is not currently photosynthetic. Samples of brine collected in November 2005 from 16.5 m down in the ice cover contain 1) the highest nitrous oxide levels of any natural water body on Earth (Dr. Samarkin, personal communication), 2) unusual geochemistry including anomalously high ammonia (nearly 4 mM), and iron concentrations (0.3 mM), 3) high microbial counts (106 to 107 cells per milliliter), 4) active bacteria (evidence of protein production), 5) a population of microbes including an unusual proportion (99%) of ultramicrobacteria, and 6) a microbial community that is unique even compared to other Dry Valley Lakes.
In this study, it is proposed to enter for the first time the main brine body below the thick ice of Lake Vida and perform in situ measurements, collect samples of the brine column, and collect sediment cores from the lake bottom for detailed geochemical, sedimentological, and microbiological analyzes The results will allow the characterization of present and past life in the lake, assessment of modern and past sedimentary processes, and determination of the lake’s history.
This study will have as a guiding premise:
- An ecosystem exists in the main brine body of Lake Vida.
- This ecosystem derives its resources from ancient pools resulting from its prior coupling with the surface (e.g. during times of thinner ice covers through stream input, aeolian deposition and subsequent fallout through the ice, and in situ photoautotrophy).
- Alternatively, if this encapsulated ecosystem did not exploit its resources, it must be receiving energy from an unknown process that geochemical and microbiological analyses will help constrain.
This study gathers a synergistic, multidisciplinary team of scientists, biologists, organic and inorganic geochemists, hydrologist, limnologist and sedimentologist. This team will be able to provide a new understanding of the biogeochemical processes allowing survival of a non-photosynthetic microbial community isolated for a prolonged period of time. This research will address diversity, adaptive mechanisms and evolutionary processes in the context of the physical evolution of the environment of Lake Vida. Sampling and cleanliness procedures, derived from the teams experience in brine sampling, are already being touted as an example of how future field exploration of subglacial lakes may be done.
Society at large will benefit from expanded knowledge of the limits of life on this planet. A thorough understanding of these limits expands our perception of the origin and evolution of life as we know it. Lake Vida may also be a model of what other dry valley lakes were like during climatic deteriorations in the past.