Coll. Res.: Geochemistry and Microbiology of the Extreme Aquatic Environment in Lake Vida, East Antarctica

Affiliation(s)PIProject periodFunded by
DEES Murray, Alison E 08/15/2009 - 07/31/2013 National Science Foundation

Project Summary

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 7 times seawater salinity and temperatures below -10 ?C 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, 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 and microbiological analyses. 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). Within the context of this premise, five hypotheses will be tested:

H1: Brine in Lake Vida is highly stratified

H2: Microbial life is active, at some level, throughout the brine

H3: The microorganisms in the brine and surface sediments currently employ cold-adapted biogeochemical strategies to maximize the resources available in this isolated, extremely cold and saline ecosystem

H4: The water column and sediments of Lake Vida contain physical and geochemical signatures of past microbiological activity and ecosystem shifts (e.g. from a photosynthetic ecosystem in contact with the atmosphere during periods of thinner ice cover)

H5: The subsurface brine of Lake Vida was derived from seawater/local weathering products with subsequent cryogenic modification of salt concentrations.

Intellectual Merit

This proposal gathers a truly multidisciplinary team to bring a new understanding to 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.

Broader Impacts

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. Results will be widely disseminated through publications, presentations at national and international meetings, and through the internet at the Subglacial Antarctic Lake Exploration (SALE) web site as an affiliated International Polar Year initiative, and the McMurdo LTER web site. This research proposal will fund a minimum of three graduate students and three undergraduate research assistants. The investigators have a strong history of training women in the sciences, collectively 6 of their last 8 graduate students being female; four of those women have been involved in field research in Antarctica and one has worked on laboratory-based Antarctic projects. The results will be incorporated into a new undergraduate biogeosciences course at the University of Illinois at Chicago which has an extremely diverse student body, dominated by minorities.

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