Glacial Ecosystems

• Published in: Ecological Monographs
• Main Authors: Hodson, A, Anesio, AM, Tranter, M, Fountain, A, Osborn, M, Priscu, J, Laybourn-Parry, J, Sattler, B
• Format: Article in Journal/Newspaper
• Language: English
• Published: Ecological Society of America 2008
• Subjects: Biological Sciences; Microbiology; Microbial Ecology; Arctic; Climate change
• Online Access: https://doi.org/10.1890/07-0187.1; http://ecite.utas.edu.au/52305

There is now compelling evidence that microbially mediated reactions impart asignificant effect upon the dynamics, composition, and abundance of nutrients in glacial meltwater. Consequently, we must now consider ice masses as ecosystem habitats in their own rightand address their diversity, functional potential, and activity as part of alpine and polarenvironments. Although such research is already underway, its fragmentary nature provideslittle basis for developing modern concepts of glacier ecology. This paper therefore provides amuch-needed framework for development by reviewing the physical, biogeochemical, andmicrobiological characteristics of microbial habitats that have been identified within glaciersand ice sheets. Two key glacial ecosystems emerge, one inhabiting the glacier surface (thesupraglacial ecosystem) and one at the ice-bed interface (the subglacial ecosystem). Thesupraglacial ecosystem is characterized by a diverse consortium of microbes (usually bacteria,algae, phytoflagellates, fungi, viruses and occasional rotifers, tardigrades, and diatoms) withinthe snowpack, supraglacial streams, and melt pools (cryoconite holes). The subglacial systemis dominated by aerobic/anaerobic bacteria and most probably viruses in basal ice/till mixturesand subglacial lakes. A third, so-called englacial ecosystem is also described, but it isdemonstrated that conditions within glacier ice are sufficient to make metabolic activity and itsimpact upon nutrient dynamics negligible at the glacier scale. Consideration of the surface and internal heat balances of the glacier show that all glacialecosystems are sensitive to climate change, although at different timescales. Thus, while rapid,melt-driven habitat changes lead to melt-out, resuscitation, and redistribution of microorganismsin many supraglacial ecosystems, much slower climatic and glacial mass-balanceprocesses effect such changes in the subglacial ecosystem. Paradoxically, it is shown that theseforces have brought about net refreezing and the onset of cryostasis in the subglacialecosystems of many Arctic glaciers subject to thinning in recent decades.