Physical, chemical, and microbial diversity of cryptoendolithic habitats in the Canadian high Arctic.
Published: 2006
Language: eng
Number of pages: 164
ISBN-13: 9780494218716
Description: Sandstone outcrops around Eureka, Ellesmere Island, Nunavut (80&deg;N) are host to a variety of cryptoendolithic microorganisms including cyanobacteria, algae, fungi and heterotrophic bacteria. Continuous measurements over two years (2002-2004) of climate and environmental parameters show that cryptoendolithic habitats experience warmer temperatures and wetter conditions than the exposed rock surface. Subsurface temperature fluctuations are moderated by the thermal capacity of the rock substrate and vary as a function of depth, aspect, and albedo. Rain, snow or snowmelt substantially increases subsurface moisture levels, which persist for significant time periods after initial precipitation events have passed. Variation in the dominance of one microbial community over another occurs between sites, however these differences exist in habitats with similar temperature conditions. Communities grow as biofilms attached to mineral surfaces as well as within the open void spaces between grains and in many cases produce extracellular polysaccharides in response to the extreme environmental conditions. This EPS provides a substrate for accumulation of allochthonous clay particles that enter the system by winds and rain. Analysis of metal ions by sequential extraction and their relationship to microbial diversity using multivariate statistics show that cyanobacteria-dominated communities exist under higher pH conditions with elevated concentrations of calcium and magnesium, whereas communities dominated by fungi and algae are characterized by lower pH conditions and higher concentrations of iron, aluminum, and silica in overlying surfaces. These differences are explained by variations in cryptoendolithic microbial community structure, which control microenvironmental pH conditions, influence substrate dissolution and weathering rates, and perpetuate their dominance within a given cryptoendolithic habitat. Greater diversity of microorganisms at this Arctic location compared to similar habitats in the Antarctic Dry Valleys is explained by warmer temperatures during summer months that lead to longer periods for both active (&sim;3700 hr&middot;yr-1) and ideal (&sim;2500 hr&middot;yr-1 ) calculated metabolic activities as well as abundant moisture in the form of liquid water. The lack of evidence for biomineralization within this habitat contrasts with similar environments in the Antarctic Dry Valleys, a consequence of these warmer temperatures and wetter conditions that increase erosion rates and subsequent habitat destruction.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0156.

Thesis (Ph.D.)--University of Toronto, 2006.

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