Abstract
AbstractSnowmelt in the Antarctic Peninsula region has increased significantly in recent decades, leading to greater liquid water availability across a more expansive area. As a consequence, changes in the biological activity within wet Antarctic snow require consideration if we are to better understand terrestrial carbon cycling on Earth's coldest continent. This paper therefore examines the relationship between microbial communities and the chemical and physical environment of wet snow habitats on Livingston Island of the maritime Antarctic. In so doing, we reveal a strong reduction in bacterial diversity and autotrophic biomass within a short (<1 km) distance from the coast. Coastal snowpacks, fertilized by greater amounts of nutrients from rock debris and marine fauna, develop obvious, pigmented snow algal communities that control the absorption of visible light to a far greater extent than with the inland glacial snowpacks. Absorption by carotenoid pigments is most influential at the surface, while chlorophyll is most influential beneath it. The coastal snowpacks also indicate higher concentrations of dissolved inorganic carbon and CO2 in interstitial air, as well as a close relationship between chlorophyll and dissolved organic carbon (DOC). As a consequence, the DOC resource available in coastal snow can support a more diverse bacterial community that includes microorganisms from a range of nearby terrestrial and marine habitats. Therefore, since further expansion of the melt zone will influence glacial snowpacks more than coastal ones, care must be taken when considering the types of communities that may be expected to evolve there.
Highlights
Snow is the most expansive terrestrial habitat in Antarctica, yet we know almost nothing about the resident ecosystem within it
The results described above reveal an active snowpack microbial ecosystem which is notable for an autotrophic biomass dominated by the snow algae and a bacterial community dominated by Proteobacteria and Bacteroidetes
Our work has shown that the biogeochemical and optical properties of Antarctic snow are directly influenced by the presence of a microbial community, especially near the coast
Summary
Snow is the most expansive terrestrial habitat in Antarctica, yet we know almost nothing about the resident ecosystem within it. We are unable to quantify the consequences that increased melting of Antarctic snow will have for downstream ecosystems. Since viable microorganisms have been reported in Antarctic snow as far inland as the South Pole (Carpenter et al, 2000), it seems reasonable to expect snowpack microbial processes to potentially influence snow biogeochemistry anywhere on the ice sheet that is subject to melting. Using a solute mass balance approach, Hodson (2006) showed how 66% of NH4+ and 74% of PO43- in a Signy Island (South Orkney Island Group) snowpack were assimilated in snow, slush and ice marginal habitats following the onset of melt
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