International Polar Year 2007–2008 - WMO

supporting an atmospheric source and the hypothesis
that ClO 4 - is globally formed, but can accumulate only
in hyper-arid environments. Also, a new ecosystem was
found in the University Valley. The soil temperatures
are below zero throughout the entire year, preventing
free flowing bulk liquid water. Nonetheless, this
valley, the best Mars analog location on Earth, shows
soil pedogenesis, salt distribution, diurnal variations
in dielectric permittivity, and living microbes, each
requiring water, only available from surface snow and
humidity or as vapor through sublimation of ground
ice. The results from this study move us one step closer
to understanding the potential habitats on Mars.
In contrast to the study in the Dry Valleys, IPY MERGE
investigated Antarctic lakes and ponds that provided
much information relevant to global warming and
associated ecological responses. For example, Holocene
climate changes were reconstructed from lake
sediment cores and palaeo-nests of penguins. Viruses
were shown to be responsible for controlling microbial
food webs and community structures of the lake
ecosystems. Catchment hydrogeology was shown to
influence vegetation of terrestrial vascular plants and
aquatic mosses. Unique aquatic “moss pillars” are
maintained by synergetic biogeochemical processes
of a microbial community, and its species diversity
Fig. 2.9-1. Sulfuroxidizing
species
of the genus
Thiomicrospira
(confocal micrographs
of microbial consortia).
(Photo courtesy Warwick
Vincent)
and functions have been dissected by metagenomic
DNA analyses. In addition, human impacts, specifically
the effect of trampling on soil characteristics and biota
were first evaluated.
MERGE also compared the genetic characteristics
of microbes from the Arctic and Antarctica, such as the
16S rRNA gene sequences of cold-dwelling cyanobacteria
from lakes, streams and ice communities. Several
High Arctic taxa were >99% similar to Antarctic and alpine
sequences, including to the ones previously considered
to be endemic to Antarctica. One High Arctic
sequence was 99.8% similar to Leptolyngbya antarctica
sequenced from the Larsemann Hills, Antarctica, and
many of the Arctic taxa were highly dissimilar to those
from warmer environments. These results imply the
global distribution of low-temperature cyanobacterial
ecotypes, or cold-adaptive endemic species, throughout
the cold terrestrial biosphere.
In addition to “endemic” species, global-wide distribution
of “cosmopolite” species, or cosmopolitans,
has been strongly suggested. Eco-physiological and
molecular characterizations of such cosmopolitans
will compliment our understanding of distribution
and colonization of cold-adaptive endemic species,
and thus help prediction of microbial “sentinel” responses
to Global Warming.
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