Abstract
The Antarctica Dry Valleys are regarded as the coldest hyperarid desert system on Earth. While a wide variety of environmental stressors including very low minimum temperatures, frequent freeze-thaw cycles and low water availability impose severe limitations to life, suitable niches for abundant microbial colonization exist. Antarctic desert soils contain much higher levels of microbial diversity than previously thought. Edaphic niches, including cryptic and refuge habitats, microbial mats and permafrost soils all harbor microbial communities which drive key biogeochemical cycling processes. For example, lithobionts (hypoliths and endoliths) possess a genetic capacity for nitrogen and carbon cycling, polymer degradation, and other system processes. Nitrogen fixation rates of hypoliths, as assessed through acetylene reduction assays, suggest that these communities are a significant input source for nitrogen into these oligotrophic soils. Here we review aspects of microbial diversity in Antarctic soils with an emphasis on functionality and capacity. We assess current knowledge regarding adaptations to Antarctic soil environments and highlight the current threats to Antarctic desert soil communities.
Highlights
ANTARCTIC DESERT SOILS Despite the fact that the ice-free areas of the Antarctic continent represent less than 0.3% of the total land area, the continent offers a wide range of different soil types, chemistries and microenvironments
The physicochemical parameters and environmental conditions of these diverse soils are wide-ranging (Bockheim and Ugolini, 1990; Bockheim and McLeod, 2008). While part of this definition is distinctly phyllocentric, it broadly encompasses the diverse range of Antarctic terrestrial “soil” habitats, despite the complete absence of higher plants in all areas other than the Antarctic Peninsula
Even the most extreme and apparently depauperate ice-free zones of the Antarctic continent can reasonably be considered as soil habitats, given that all contain microbial populations and detectable, if low, levels of organic carbon
Summary
ANTARCTIC DESERT SOILS Despite the fact that the ice-free areas of the Antarctic continent represent less than 0.3% of the total land area, the continent offers a wide range of different soil types, chemistries and microenvironments. Even the most extreme and apparently depauperate ice-free zones of the Antarctic continent can reasonably be considered as soil habitats, given that all contain microbial populations and detectable, if low, levels of organic carbon.
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