Abstract
In recent years, glacial surfaces have received much attention as microbial habitats of diverse photoautotrophic and heterotrophic cells. Supraglacial ecosystems are annually covered and uncovered by snow. The aim of this study is to investigate the microbial community response to changing environmental conditions in a transect following the receding snow line on the surface of Ecology Glacier (King George Island, Antarctica). Parameters of surface ice and cryoconite holes included chemical composition of ice and sediment, Bacteria diversity by denaturating gradient gel electrophoresis, microbial functional diversity (Biolog Ecoplates), and microbial counts (epifluorescence microscopy, colony-forming units). Data demonstrated profound differences between surface ice and cryoconite holes. Changing environmental factors along the transect influenced composition and abundance of the microbiocenosis in both habitat types. Several parameters correlated positively with distance from the glacier edge, including the cell morphotype Shannon index, chlorophyll a, nitrogen, and seston concentrations. Suspended solid content positively correlated with microbial abundance and diversity. Nitrogen and phosphorus were limiting factors of microbial growth as amounts of organic nitrogen and phosphorus positively correlated with the cell numbers, fission rates, and photoautotroph contribution. Our findings indicate that microbial community shows a response in terms of abundance and diversity to exposure of the glacial surface as snow-cover melts. To our knowledge, this is the first study to recognize a microbial development pattern on a glacier surface in connection with the receding snow line. This may help better understand variability within supraglacial habitats, correct sampling procedures, and inform biocenotic development models.
Highlights
A significant part of the biosphere is permanently below 5 °C (Anesio and Laybourn-Parry 2012)
Chlorophyll a contents varied in surface ice samples from 0.53 (EDI) to 3.53 lg l-1 at EI4 (Table 2)
The highest amounts of total particulates were measured in the higher elevation points of the ablation zone for surface ice (EI4—769.20 mg dry wt. l-1), and cryoconite holes (EC5—9213 mg dry wt. l-1), comprising in all but one case (i.e., DIE) mostly organic material. pH ranged from 6.10 (EI3) to 7.15 (EI2) for ice samples, and 6.15 (EC2) to 7.00 (EC4) for cryoconite suspension
Summary
A significant part of the biosphere is permanently below 5 °C (Anesio and Laybourn-Parry 2012). This includes glaciers and ice sheets, which occupy 11 % of Earth’s surface, and which comprise *70 % of surface global freshwater (Shiklomanov 1993; Paterson 1994). Glacial systems result from the perennial accumulation of snow. Their subsequent deformation leads to their flow to lower elevations, where they melt, sublimate or calve in the ablation zone. The ablation zone expands as the ‘snow line’ advances up the glacier (Hooke 2005; Anesio and Laybourn-Parry 2012; Edwards et al 2014).
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