Microbial processes in the weathering crust aquifer of a temperate glacier
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Published:2018-11-26
Issue:11
Volume:12
Page:3653-3669
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Christner Brent C.,Lavender Heather F.,Davis Christina L.,Oliver Erin E.,Neuhaus Sarah U.,Myers Krista F.,Hagedorn Birgit,Tulaczyk Slawek M.,Doran Peter T.,Stone William C.
Abstract
Abstract. Incident solar radiation absorbed within the ablation zone of glaciers
generates a shallow perched aquifer and seasonal icebound microbial habitat.
During the melt seasons of 2014 and 2015, borehole investigations were used
to examine the physical, geochemical, and microbiological properties in the
near-surface ice and aquifer of the temperate Matanuska Glacier
(south-central Alaska). Based on temperature, solar forcing, and ice optical
properties, the dissipation of shortwave radiation promoted internal melting
and the formation of a weathering crust with a maximum depth of ∼2 m.
Boreholes into the weathering crust provided access to water percolating
through the porous ice. The water had low ion concentrations
(4–12 µS cm−1), was aerobic
(12 mg O2 L−1), contained 200 to 8300 cells mL−1,
and harbored growing populations with estimated in situ generation times of
11 to 14 days. During the melt season, the upper 2 m of ice experienced at
least 3 % of the surface photosynthetically active radiation flux and
possessed a fractional water content as high as 10 %. Photosynthetic
subsistence of biogeochemical reactions in the weathering crust ecosystem was
supported by ex situ metabolic experiments and the presence of phototrophic
taxa (cyanobacteria, golden and green algae) in the aquifer samples.
Meltwater durations of ∼7.5 months coupled with the growth estimates
imply biomass may increase by 4 orders of magnitude each year. Our results
provide insight into how seasonal dynamics affect habitability of
near-surface ice and microbial processes in a portion of the glacial biome
poised to expand in extent with increasing global temperature and ablation
season duration.
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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