Trans Internet-Zeitschrift für Kulturwissenschaften 16. Nr. August 2006

14.7. "Ränder der Welt" im Zeitalter transnationaler Prozesse
HerausgeberInnen | Editors | Éditeurs: Knut Ove Arntzen (Bergen) / Gabriele Rampl (Scinews, Innsbruck)

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Ice and Life

Birgit Sattler (University of Innsbruck, Institute of Ecology, Innsbruck, Austria) [BIO],
Paul Sipiera
(Planetary Studies Foundation, Institute for Meteorite and Polar Studies, Algonquin, IL, USA),
Roland Psenner (University of Innsbruck, Institute of Ecology, Innsbruck, Austria


1. Introduction

Life in ice always seemed to be a paradox, but apparently frontiers for microbial life are extended with proceeding elaboration of techniques to detect life. Until now, literally no environment can be declared as vast of life, not even the large ice and snow fields of Polar Regions or the highs of mountains which originally were seen as sterile and harsh environments. They were addressed as hostile and poor in nutrients not being sufficient to sustain life.

Not surprisingly, it was the ancient Greeks who first thought about the possibility of microscopic life forms existing in ice, but it was the observations of “dark snow” by Bauer that first attracted serious scientific consideration [1]. Further descriptions of possible life forms, on and within snow, were obtained over one hundred years ago from the observations of early polar explorers like Nansen [2]. Yet, these early studies did not consider large snow areas to be viable ecosystems for life. Due to extreme climatic conditions such as dramatic oscillations in temperature, high UV radiation and minimal amounts of nutrients, these extremely cold conditions were treated solely as collection sites for accumulated airborne particles and bacteria. In contrast, modern studies have identified cold-loving microbial assemblages in various locations ranging from alpine and high latitude regions to Antarctica. Recent studies examining microbial life in extreme polar conditions have changed the earlier view from a sterile desert wasteland devoid of life to an active ecosystem teaming with life. Over the past thirty years various ice ecosystems such as sea ice, lake ice, glaciers, snow fields, and even the atmosphere have provided evidence for a relatively high degree of biodiversity. Further studies dealing with the adaptation, physiology and metabolism of extremophiles from various terrestrial habitats have raised the question of whether or not these assemblages might serve as possible analogues for life that may exist on other worlds such as Mars or the Jovian moon Europa.

An overview concerning the various ice ecosystems harboring such extremophiles should contribute to that discussion. Other valuable benefits can be gained from the study of microbial ice ecosystems. Due to the presence of cold-shock proteins, microbial ice assemblages have the capability of surviving sub-zero temperatures as well as repeated freeze and thaw cycles. According to [3] gaining an understanding of how this process works could have valuable biotechnological applications.


2. Various Ice Ecosytems – Life Without Frontiers

2.1. Sea Ice

Sea ice is probably the most studied ice ecosystem. The first observations of microbes colonizing sea ice were made over one hundred years ago during Nansen’s incredible arctic drift voyage. A later study by reference [4] discussed the presence of a variety of microbes found in ice associated with brine channels - caves within the ice which are filled with high salinity sea water. Many years later, support for this type of ecosystem was done by the development a cast technique to analyze brine pockets and channel structures [5].

Additional studies [e.g. 6], dealing with the various ice ecosystems of Antarctica confirm microbial psychrophily and biodiversity. They detected a surprisingly high degree of unusual diversity associated with sea-ice organisms which were, for the most part, well adapted to cold temperatures. Sea ice assemblages from Antarctica, also referred to as SIMCO (sea ice microbial communities), provide extremely valuable data to support climatic changes that can be attributed to global warming [7].

2.2. Lake ice

Reference [8] first describes the microbial assemblages present within the winter cover of high mountain lakes (e.g. in the Alps and Pyrenees). These microbes are found colonizing horizontal structures in a slushy matrix which is embedded within layers of opaque white ice and an overlying snow cover. Prior to the present study, only three sources for microbial settlement of the winter cover were described. The main source is the underlying water column which provides the ice cover with viable cells during the growth phases of the ice cover. Secondly, airborne cells are deposited with precipitation and wind on the snow cover. As a third source, especially during snow melt, the surrounding slopes of the catchment area provide the ice cover with terrestrial organic material as well as a highly diverse terrestrial microbial assemblage. Studies conducted on species composition revealed highly diverse assemblages depending upon their source which is derived from either the water column, the atmosphere or the catchment area [9]. In-depth investigations of the biodeversity in these lake ice microbial communities (LIMCOs) showed a relatively low degree in psychotrophs or psychrophiles. Despite the cold temperatures, the slush layers remain relatively stable at the freezing point of water [10]. Throughout the ice covering season these ice assemblages are characterized by even higher carbon production rates and higher carbon contents than in the warmer pelagic zone underneath. Several factors favor the higher growth rates. Firstly, the accumulation effect of nutrients in ice and slush layers which cannot be diluted by wind generated mixing as would be the case in the open lake. Furthermore, unique events like the deposition of Saharan dust which supplies snow microbes with nutrients, or the growth of snow algae releasing dissolved organic carbon. Due to their various origins, lake ice assemblages are not necessarily extremophiles and possess a high potential in surviving seemingly harsh conditions.

Lake ice microbial communities on the Antarctic continent (McMurdo Dry Valleys) are of completely different origin and [11, 12]. Microbial life within the ice of permanent ice covered lakes as described in [13] is literally life on the edge. Mainly cyanobacteria are viable in the austral summer when a microfilm of water is available. Their growth rates which last one complete year are one of the most extreme cases reported in aquatic microbial ecology. Specifically, extreme cold and dry environments, like the unique McMurdo Dry Valleys, are the closest terrestrial analogs to conditions present on Mars making these climatic oases very attractive for astrobiology. Reference [13] proves in a study based on molecular biological means (16S rDNA gene amplification) that the lake ice microbial community appears to be dominated by organisms that are not uniquely adapted to the lake ice ecosystem, but instead are species that originate elsewhere in the surrounding region and opportunistically colonize the unusual habitat provided by the sediments suspended in the lake ice.

2.3. Glaciers

Scientific studies concerning bacterial biodiversity in glaciers are scarce. In a recent study [14] an examination of the meltwater from a Canadian glacier provided evidence of “polyextremophiles”, microbes which can survive in a wide range of harsh conditions. In this particular case the microbes thrive in meltwater created by geothermal heat and the heat generated through friction from movement at the bottom of the glacier. The most surprising finding was the presence of the organism Deinococcus radiodurans in the polar ice sheet of South Pole by [15], a species particularly resistant to high levels of radiation, extremely low temperatures and dryness. Investigations of glacial meltwater done by Sattler et al. (unpublished data) provide evidence for surprisingly high abundances of viruses. In addition to bacteria, diatoms were found in the glacial ice.

In an extreme habitat like glaciers, with hardly any nutrient turn-over except running meltwater from under the base of the glacier, the same effect as described above can be observed: Microbial species originating elsewhere may become trapped in the glacial ice, remaining there in a dormant status and later being revitalized in the presence of liquid water [14, 16]. Using this data glaciers can serve as important long-term DNA archive and may be used to reveal clues for climate research by investigating species compositions present in the ice.

2.4. Atmosphere

Since the 1940’s the term “aeroplankton” frequently appeared in the scientific literature [17]. It was believed that atmospheric conditions such as temperatures down to 40°C below, high doses of radiation and low nutrient availability were too harsh for any cells to survive. It was thought that these microbes could only be present as inactive spores. This idea changed as new data became available concerning the adaptability of microbes to deal with these harsh conditions. Many new scenarios became possible, and even active carbon production could be identified in super cooled cloud droplets collected from Sonnblick Observatory in the Austrian Alps (ca. 3.000m a.s.l.). Bacterial numbers are considerably low in these droplets and it is thought that the cells might protect themselves from freezing by producing alcohol, a side product of alkane degradation derived from the burning coal and oil. This fact leads to the assumption that microbes are even able to degrade, to a certain degree, man made substances in the atmosphere [18, 19] . Microbial cells can be brought up to the atmosphere by wind generated mixing of aqueous surfaces (upward movement of sea spray), by feces of birds or simply by terrestrial material harboring microbes, which is dispersed by the wind. The consequence of this upward movement is that there is more organic material in the atmosphere than just extremophiles. This may be dislocated material from aquatic or terrestrial ecosystems that has adapted to this new environment. These findings prove that the atmosphere is not the sole conveyor of microbial cells, but also a large ecosystem in itself. Considering that the Earth’s surface generally experiences up to 60% cloud coverage, science should not neglect the atmosphere’s ability to transport viable microbial cells to otherwise remote regions of the planet.

2.5. Snow areas

In the past, vast snow regions were looked upon in the same manner as ice sheets: sterile and inhospitable. Now days high mountain and polar snow fields are recognized as highly diverse microbial community habitats, especially when associated with cryoconites. Cryoconites, by the fact that they accumulate high amounts of nutrients, are the so called hot spots for microbial activity. These nutrients are deposited by the wind or animals and therefore provide these microbial assemblages with an abundant supply of carbon and nitrogen [20]. According to [21] cryoconite holes are considered as eutrophic microhabitats in an oligotrophic habitat such as ice and meltwater with a low nutrient level. Such an environment is enhanced by increased light absorbancy and a resulting increase in temperature. A novel study [22] examined snow fields on top of and around a high mountain lake revealed a highly active microbial assemblage which can be characterized by their different origins (terrestrial, airborne or meltwater).

The presence of microbial communities in snow and ice fields is also important to the field of astrobiology. Meteorites, which have been collected on the vast ice sheet of Antarctica, have long been thought to be contamination-free from the presence of terrestrial microbes. It was hoped that any organic material found in these meteorites would be representative of extraterrestrial sources. It is obvious as shown in reference [23] that these meteorites can easily be contaminated by microbes entrapped in the ice. Once a meteorite lands in Antarctica it becomes incorporated into a moving ice sheet that will transport it far from its original landing site. A meteorite can remain entrapped in ice for thousands of years before it emerges at the surface. This can happen when the moving ice sheet comes in contact with an obstruction such as a mountain range which impedes the movement of the ice creating a stranding surface. Meteorites, along with any other rock material, will eventually emerge from the ice as wind ablation erodes the surface where the meteorites may lie exposed to surface conditions for thousands of years. Contact with the atmosphere and even minimal seasonal melting of surface ice can create an environment suitable for microbial life. Ice, which was directly in contact with a meteorite, was sampled to a depth of one meter in order to assess the presence of any microbial life. This sampling revealed a considerable amount of heterotrophic bacteria (Sattler et al., unpublished data). However, even in this harsh environment the dominating species are not extremophiles.



This overview about various ice ecosystems on earth lead to the assumption that coldness, dryness, high radiation or low nutrients are not restricting factors for the presence of viable microbial assemblages. Even in permanently cold environments at least 50% of the bacteria [24] or even a greater portion [25] are not psychrophilic.

Nowadays, discussions concerning extremophiles serve as analogues to possible extraterrestrial life forms such as those envisioned for an early Mars. These theories are based upon to the ability of various microbial strains not only to survive in harsh conditions but also to be able to sustain a functioning metabolism, carbon production and cellular growth. With this discussion we should not neglect other dislocated microbial species which “happen” to exist in an extreme environment and establish themselves in spite of the inhospitable conditions which is breaking up frontiers of life.

© Birgit Sattler (University of Innsbruck, Institute of Ecology, Innsbruck, Austria),
Paul Sipiera
(Planetary Studies Foundation, Institute for Meteorite and Polar Studies, Algonquin, IL, USA),
Roland Psenner (University of Innsbruck, Institute of Ecology, Innsbruck, Austria


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[2] Nansen, F., Farthest North, Harper and Brothers Publishers, New York

[3] Margesin R., and Schinner F., Properties of cold-adapted microorganisms and their potential role in biotechnology, J. Biotechn. 33, pp.1-4 (1994)

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[5] Weissenberger J., Die Lebensbedingungen in den Solekanälchen des antarktischen Meereises. Ber. Polarforsch. 111, pp. 159 (1992)

[6] Bowman J.P., Rea S.M., Brown M.V., McCammon S.A., Smith .C., and McMeekin T.A., Community structure and psychrophily in Antarctic microbial ecosystems, Microbial Biosystems: New Frontiers, Proceedings of the 8 th International Symposium on Microbial Ecology, Bell C.R., Brylinsky M. Johnson-Green P (ed), Atlantic Canada Society for Microbial Ecology, Halifax, Canada (1999)

[7] Palmisano A.C. and Sullivan C.W., Sea ice microbial communities (SIMCO). 1. Distribution, abundance, and primary production of ice microalgae in McMurdo Sound, Antarctica in 1980. Polar Biol. 2, p. 171-177 (1983)

[8] Felip M., Sattler B. Psenner R. and Catalan J. Highly active microbial communities in the ice and snow cover of high mountain lakes. Appl. Environ. Microbiol. 61:2394-2401 (1995)

[9] Alfreider A., Pernthaler J., R. Amann, B. Sattler, F.-O. Glöckner, A. Wille and R. Psenner, Community analysis of the bacterial assemblages in the winter cover and pelagic layers of a high mountain lake using in situ hybridization. Appl. Environ. Microbiol. 62 (6):2138-2144 (1996)

[10] Haslwanter, A., Messung eines vertikalen Temperaturprofils über einen Jahreszyklus und der Einfluß der Winterdecke auf den Energieinhalt des Gossenköllesees (Dipl.Arb.), p. 147 (2000)

[11] Psenner R. and Sattler B, Life at the freezing point. Science 280, p.2073-2074 (1998)

[12] Priscu, J.C. (ed.). The McMurdo Dry Valleys, Antarctica: a cold desert ecosystem, Antarctic Research Series 72. American Geophysical Union, Washington pp. 129-140. (1998)

[13] Gordon D.A., Priscu J., and Giovannoni S., Distribution and phylogeny of bacterial communities associated with mineral particles in Antarctic lake ice. Microbial Ecology. 39:197-202 (2000)

[14] Catranis, C. & W.T. Starmer. Microorganisms entrapped in glacial ice. Antarctic Journal of the United States 25, p. 234-236 (1991)

[15] Carpenter E.J., S. Lin and D.G. Capone. Bacterial activity in South Pole snow. Appl. Environ. Microbiol. 66: 4514-4517 (2000)

[16] Sharp, M., Parkes J., Cragg B., Fairchild I.J., Lamb H., and Tranter M.. Widespread bacterial populations at glacier beds and their relationship to rock weathering and carbon cycling. Geology 27, p. 107-110 (1999)

[17] Gislén, T., Aerial plankton and its conditions of life, Biological Reviews, 23, 109-126 (1948)

[18] Sattler B., Puxbaum H. and Psenner R., Bacterial growth in supercooled cloud droplets. Geophys. Res. Letters 28(2), p. 239-242 (2001)

[19] Sattler B. Puxbaum H., Limbeck A. and Psenner R, Clouds as habitat and seeders of active bacteria. Instruments, Methods and Missions for Astrobiology IV, Hoover R., Levin G.V., Paepe R.R., and Rozanov A.Y (Ed.). Proceedings of SPIE Vol. 4495, p. 211- 222 (2002)

[20] Jones, H.G., Duchesneau M., and Handfield M.. Nutrient cycling on the surface of an arctic ice cap: Snow-atmosphere exchange of N species and microbiological activity. In: H.G. Jones et al. (eds.), Snow and ice covers: Interactions with the Atmosphere and Ecosystems (Proceedings of Yokohama Symposia J2 and J5, July 1993. IAHS Publ. no. 223. (1994)

[21] Margesin, R., Zacke, G., Schinner, F., Characterization of heterotrophic microorganisms in alpine glacier cryoconite. Arctic Antarctic Alpine Research 34: 88-93 (2002)

[22] Bichteler A. Sukzession der mikrobiellen Gemsceinschaft der Schneedecke über ein Catchment-Lake-Continuum des Gossenköllesee. Dipl. Thesiss University of Innsbruck, 117pp. (2000)

[23] Sipiera, Paul P., R.B. Hoover, and G.A. Jerman, 2000. “Meteorite and Microbes: Meteorite Collection and Ice Sampling at Patriot Hills, Thiel Mountains, and South Pole, Antarctica”. Proc. of SPIE Vol. 4137, pp. 13-21 (2000)

[24] Delille D. and Perret E., Influence of temperature on the growth potential of southern polar marine bacteria. Microb. Ecol. 18, p. 117-123 (1989)

[25] Herbert R.A., The ecology and physiology of psychrophilic microorganisms. In Herbert R.A. and Codd G.A. (eds.). Microbes in Extreme Environments. London: Academic Press, p. 1-23 (1986)


A grant provided by the Planetary Studies Foundation for the participation of B. Sattler on their Antarctica 2002 Expedition. Further financial support was given by the Austrian Science Foundation FWF P14201-BIO.

14.7. "Ränder der Welt" im Zeitalter transnationaler Prozesse

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For quotation purposes:
Birgit Sattler (University of Innsbruck, Institute of Ecology, Innsbruck, Austria), Paul Sipiera (Planetary Studies Foundation, Institute for Meteorite and Polar Studies, Algonquin, IL, USA), Roland Psenner (University of Innsbruck, Institute of Ecology, Innsbruck, Austria): Ice and Life. In: TRANS. Internet-Zeitschrift für Kulturwissenschaften. No. 16/2005. WWW:

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