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Superimposed on a general decline of radiocarbon uptake as a function of depth of origin of the sample (from 0.0044 μg per liter per h at 1,665 m to 0.0002 μg per liter per h at 2,750 m), they found a very low uptake in cells from depths corresponding to cold periods.

Willerslev (10), using PCR amplification of fragments of the eukaryotic 18S r RNA gene, identified a diversity of fungi, plants, algae, and protists extracted from 2,000- and 4,000-year-old ice-core samples from North Greenland. The possibility of finding subglacial sources of microbes is now of great international interest.

Microbial life has been found at depths down to several kilometers in the earth's crust (3), and viable bacterial populations have been discovered at Pacific Ocean sites to depths of 500 m in sediments (4).

Working with filtered (0.2 μm), melted ice from depths down to 2,750 m in the ice core from Vostok Station (east Antarctica), Abyzov and correlated with dust concentration, which suggests that they were deposited in the snow preferentially during glacial periods when the flux of dust and the wind speed were greatest.

In addition, the authors used consumption of a C-labeled protein hydrolysate as a crude measure of cell viability.

The explanation for how foreign ions migrate into veins has to do with the fact that micrometer-size droplets of acids and sea salts deposited as aerosols are essentially insoluble in ice crystals.

Coarsening and recrystallization of deep ice, in response to the shear stress induced by the weight of the overlying ice, take place by migration of grain (crystal) boundaries, which sweep through and scavenge the droplets.

In 1974–1975, airborne radar mapping (11) resulted in the discovery of a huge subglacial lake under nearly 4 km of ice near Vostok Station.

Recently, seismic sounding and radar mapping plus radar altimetry (12) showed that the lake water is ≈650 m deep at the deepest end and has a density consistent with that of fresh water. Petersburg, Russia (13), Washington, DC‡, and Cambridge, England§, were devoted to discussions of prospects for drilling into the lake. Petersburg workshop, Petit (14) reported that the bottom ≈100 m of a 3,623-m-deep Vostok ice core that reached a depth ≈120 m above the lake consists of refrozen lake water, called “accretion ice,” whose crystals range in size from ≈0.1 to 1 m.At the Cambridge workshop, Priscu (15) also reported evidence for microbial life in their sample of melted accretion ice: the presence of dissolved organic carbon (7 μM), including ≈100 pg/liter of lipopolysaccharides, and sluggish uptake of into biomolecules.A small fraction of the microbes in the accretion ice is viable but probably not capable of reproducing.Recently, using a micrometer-size laser beam, Fukazawa Microbial habitat consisting of solid ice grains (approximated by truncated semiregular octahedra) bounded by liquid veins (not to scale).Two microbes are depicted as living in the vein of diameter dvein surrounding a single grain of diameter D.Using a scanning electron microscope equipped with a cold stage and an energy-dispersive x-ray microanalyzer, Wolff and coworkers (18, 19) showed that sulfur was concentrated in veins and was undetectable in the bulk of the ice.

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