Sediment sample return

Sediment-water interface samples and shallow-depth sediment cores will be taken for information on biological and biochemical conditions, processes, and cycling. Longer cores from deeper horizons will be taken to establish the history of the lake and for paleoclimate studies. If coring is done from the surface, a cased coring system will be used to decrease contamination due to redistribution of materials within the lake. Temperature and pressure changes as a result of raising the cores from the bottom of the lake to the ice sheet surface also have to be taken into account. Analyses of DNA, culture microbes, metabolic activity measures, and a full suite of microscopy and chemical analyses will be completed on the cores. Experience gained from the Ocean Drilling Project, as well as retrieving sea bottom sediment cores through the 415 m thick ice of the Ross Ice Shelf is valuable for application to the Lake Vostok project (Kennicut, 2001, 2002a,b, 2003a,b).

The group of specialists determined the following priorities:

• To determine the identity and diversity of life forms. Answers to the major question of whether the biology of Lake Vostok is viable or fossil can be found here. This study includes determination of the amount of biomass and density of each type of life; determination of progenitors of subglacial life in the lake water, including hydrothermal sites, ice, hydrate crystals, determination of the types of organisms that are metabolically active, and determination of the spatial location of diversity.

• To define the redox couples that support life. Included here is the elucidation of any unique biochemical or physiological processes; determination of in situ growth and metabolic rates of organisms; determination of the minimum amount of energy required for growth; determination of energy sources and how energy is extracted from the environment; determine the carbon sources that support life in the lake; and investigation of connections between living organisms in the lake and gas hydrates. • To determine the evolutionary history of Lake Vostok and its biota through the study of bottom sediment cores.

All the above need to be done with critical testing, verification, and monitoring for potential possibilities of contamination during the drilling and penetration of the lake, work within the lake, and return of equipment, samples, and cores from the lake to the surface through about 4,000 m of ice sheet. Stewardship issues include the protection of Lake Vostok environments by ensuring minimal alteration or change due to scientific studies. From a scientific point of view it is important that samples be available for study in pristine condition and remain unchanged from their sites of sampling, and that the presence of manufactured devices does not influence the results of measurements and observations. The present debate and controversy on the origin of microbes in the accreted lake ice are examples of the potential problems that must be dealt with during the lake's exploration. Another area of concern is that previously unknown microbes and other microbiological material be properly secured and stored to avoid unwanted contact with our environment. Redistribution of lake water and sediments during in situ measurements and observations should be kept to a minimum because of the oligotrophic nature of the lake (Kennicut, 2001).

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