International Polar Year 2007–2008 - WMO

of basal water with the overlying ice sheet dynamics
fundamentally advanced our understanding of
subglacial environments and how they may evolve
and function (Fig. 2.6-2). Geophysical surveys also
detected features that did not fit the definition of
lakes, but nevertheless appeared to contain liquid
water or water-saturated sediments. This led to a
broadening of interests from lakes to subglacial
aquatic environments in general.
Life under the Ice
As discussed above, in parallel with physical science
discoveries, the debate over the existence of life in the
lakes continued unabated. This debate engendered
public interest in what might be living in the lakes
and prompted extensive coverage in the popular
press. This discussion proved valuable in maintaining
a high profile for subglacial research and assisted
in keeping the topic high on the agenda of funding
agencies. While many of the physical attributes of
subglacial environments (temperature, pressure,
salinity, etc.) would not be considered “extreme”,
the general consensus is that the ultra-oligotrophic
conditions (extremely low nutrient levels) that would
most likely prevail in these environments would be
very challenging, even for microbial life. Extreme
nutrition, essential element and energy limitations
were expected to be common in these environments
due to their relative isolation.
Indirect evidence of biological residents and
geochemical conditions in these environments came
from the analysis of accreted lake ice (lake water
frozen onto the base of the ice sheet) recovered
from the Vostok borehole. These samples were not
originally recovered for microbiological analyses
raising questions about possible contamination of
the samples. Partitioning of lake water constituents
into ice under subglacial lake conditions is also poorly
understood making extrapolation of accreted ice
results to lake water compositions difficult at best
(Gabrielli et al., 2009). These circumstances have
resulted in conflicting and ambiguous evidence about
life in the lake, the biogeochemistry of lake water and
the possible influence of hydrothermal effluents in
Lake Vostok. These discrepancies will not be resolved
until water and sediments are collected in situ and
returned to the laboratory for analysis under clean
Fig. 2.6-2. An artist’s
representation of
the aquatic systems
scientists believe are
buried beneath the
Antarctic ice sheets
(Credit: Zina Deretsky/
NSF).
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