02787nas a2200241 4500008004100000245002300041210002300064250000600087300001000093490000700103520220500110653001102315653001702326100001402343700002602357700002002383700002402403700001402427700002102441700002802462700001502490856004002505 2008 eng d00aGlacial ecosystems0 aGlacial ecosystems a1 a41-670 v783 a
There is now compelling evidence that microbially mediated reactions impart a significant effect upon the dynamics, composition, and abundance of nutrients in glacial melt water. Consequently, we must now consider ice masses as ecosystem habitats in their own right and address their diversity, functional potential, and activity as part of alpine and polar environments. Although such research is already underway, its fragmentary nature provides little basis for developing modern concepts of glacier ecology. This paper therefore provides a much-needed framework for development by reviewing the physical, biogeochemical, and microbiological characteristics of microbial habitats that have been identified within glaciers and ice sheets. Two key glacial ecosystems emerge, one inhabiting the glacier surface (the supraglacial ecosystem) and one at the ice-bed interface (the subglacial ecosystem). The supraglacial ecosystem is characterized by a diverse consortium of microbes (usually bacteria, algae, phytoflagellates, fungi, viruses and occasional rotifers, tardigrades, and diatoms) within the snowpack, supraglacial streams, and melt pools (cryoconite holes). The subglacial system is dominated by aerobic/anaerobic bacteria and most probably viruses in basal ice/till mixtures and subglacial lakes. A third, so-called englacial ecosystem is also described, but it is demonstrated that conditions within glacier ice are sufficient to make metabolic activity and its impact upon nutrient dynamics negligible at the glacier scale.
 
Consideration of the surface and internal heat balances of the glacier show that all glacial ecosystems are sensitive to climate change, although at different timescales. Thus, while rapid, melt-driven habitat changes lead to melt-out, resuscitation, and redistribution of microorganisms in many supraglacial ecosystems, much slower climatic and glacial mass-balance processes effect such changes in the subglacial ecosystem. Paradoxically, it is shown that these forces have brought about net refreezing and the onset of cryostasis in the subglacial ecosystems of many Arctic glaciers subject to thinning in recent decades.
10aBiggie10asnow ecology1 aHodson, A1 aAnesio, Alexandre, M.1 aTranter, Martyn1 aFountain, Andrew, G1 aOsborn, M1 aPriscu, John, C.1 aLaybourn-Parry, Johanna1 aSattler, B uhttp://dx.doi.org/10.1890/07-0187.100609nas a2200181 4500008004100000245009000041210006900131260001200200300001200212490000700224653001100231653001300242100002300255700002800278700002400306700001600330856008100346 2000 eng d00aStratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica0 aStratification and dynamics of microbial loop communities in Lak c12/2001 a649-6610 v4410aBiggie10aprotozoa1 aRoberts, Emily, C.1 aLaybourn-Parry, Johanna1 aMcKnight, Diane, M.1 aNovarino, G uhttp://onlinelibrary.wiley.com/doi/10.1046/j.1365-2427.2000.00612.x/abstract