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The role of heterotrophs in glacier surface ecosystem productivity

Poniecka, Ewa 2020. The role of heterotrophs in glacier surface ecosystem productivity. PhD Thesis, Cardiff University.
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Abstract

Cryoconite holes are miniature freshwater ecosystems on glacier surfaces worldwide that harbour a diverse microbial community. Microbial isolates from cryoconite holes show exceptional environmental tolerance: they are able to grow in a wide range of pH, high salinities and scavenge a wide range of organic carbon sources. All the isolates tested were facultative anaerobes The community resilience exceeds the ‘normal’ conditions encountered, and enables their functionality in microenvironments, and in transition environments caused by freeze-thaw. This study demonstrates for the first time that environmental conditions, in particular concentrations of oxygen, are spatially heterogenous at the microscale. Anoxic zones develop rapidly following disturbance and can be found inside cryoconite granules and in thick layers of cryoconite sediment. These microhabitats, with limited oxygen, create microniches for anaerobic metabolism. Facultatively anaerobic microorganisms isolated from cryoconite holes are capable of anaerobic biodegradation via fermentation, and anaerobic metabolism in the holes is dominated by fermentation. An excess of fermentation products, especially acetate, can be detected in defrosted cryoconite sediments and in long-term incubations, indicating incomplete metabolic pathways. Analysis of the microbial community structure revealed that terminal oxidisers are present in low abundance in some of the samples, but the terminal metabolic steps such as sulphate reduction or methanogenesis are not coupled with fermentation. This means that fermentation products could be released to downstream environments, but the extent and impact of this process requires further quantification. Anaerobic metabolism and anaerobic microorganisms are therefore important components of cryoconite ecosystem, which degrade organic matter and impact the glacier carbon cycle.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Date of First Compliant Deposit: 8 February 2021
Date of Acceptance: 8 February 2021
Last Modified: 09 Feb 2021 10:53
URI: http://orca.cardiff.ac.uk/id/eprint/138342

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