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Microbial Methane Production in Oxic Lake Waters / MARCO GUNTHEL

Swansea University Author: MARCO GUNTHEL

DOI (Published version): 10.23889/Suthesis.53897

Abstract

Microbial methane production is commonly believed to be an exclusively anaerobic process performed by methanogenic Archaea, but the recent discovery of methane production in oxygenated waters challenges this paradigm and demands re-assessments of the global methane cycle. There are important questio...

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Published: Swansea 2019
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Tang, Kam W. ; Flynn, Kevin
URI: https://cronfa.swan.ac.uk/Record/cronfa53897
first_indexed 2020-04-03T22:08:23Z
last_indexed 2025-03-27T06:40:27Z
id cronfa53897
recordtype RisThesis
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spelling 2025-03-26T13:16:13.8955709 v2 53897 2020-04-03 Microbial Methane Production in Oxic Lake Waters 53b95404bdc1d2930447f9e6ee4d06ca MARCO GUNTHEL MARCO GUNTHEL true false 2020-04-03 Microbial methane production is commonly believed to be an exclusively anaerobic process performed by methanogenic Archaea, but the recent discovery of methane production in oxygenated waters challenges this paradigm and demands re-assessments of the global methane cycle. There are important questions regarding this newly recognized methane source: What are the environmental controls? Who are the responsible organisms? What are the underlying pathways? Is this phenomenon of global relevance? This thesis shows that oxic methane production was a recurring phenomenon in the seasonally stratified oxic water column of Lake Stechlin. Sunlight exposure and phosphorus limitation promoted oxic-water methane accumulations in situ. Bacteria (Cyanobacteria) and Algae (Diatoms, Green Algae, Cryptophytes) produced methane from 13C-labelled bicarbonate in incubation experiments, indicating that oxic methane production was associated with autotrophic carbon fixation. Further, correlations between water column methane concentrations and phytoplankton pigments were observed on the diurnal and seasonal scales. Together, these findings suggest that oxic methane production is a common feature of phytoplankton and likely relevant for limnic systems in general. Balancing the system-wide methane sources and sinks of Lake Stechlin’s surface mixed layer shows the oxic methane source was a substantial contributor to atmospheric methane emission with pronounced short-term dynamics. In addition, empirical modelling based on results presented here and available literature data reveals that oxic methane production in lake waters has global implications: The oxic methane source is predicted to be the primary source of atmospheric methane emission from the mid-water column in lakes larger than 1 km2. Furthermore, the explanatory power of the widely used wind-based models for estimating water-to-air gas emission was much improved by incorporating water- and air temperatures as additional proxy parameters. This thesis shows that oxic methane production is important to lake methane cycling, and global assessments like the upcoming IPCC report should acknowledge the oxic methane source. E-Thesis Swansea oxic methane source, oxygenated water, lake CH4 budget, phytoplankton, photosynthesis, methane emission, surface flux parameterisation, Lake Stech/in 1 9 2019 2019-09-01 10.23889/Suthesis.53897 Chapters 2 and 4 of the Ph.D. thesis have been radacted. They already have been published by various scientific journals or are in the process of being published. COLLEGE NANME COLLEGE CODE Swansea University Tang, Kam W. ; Flynn, Kevin Doctoral Ph.D Not Required 2025-03-26T13:16:13.8955709 2020-04-03T15:35:47.8943111 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Biosciences MARCO GUNTHEL 1 53897__17008__18d4794992c04ceabe3cc238e398207d.pdf PhDThesis_Günthel_2020_RedactedVersion.pdf 2020-04-03T15:47:56.7999863 Output 6813904 application/pdf Redacted version - open access true 2023-03-31T00:00:00.0000000 true eng
title Microbial Methane Production in Oxic Lake Waters
spellingShingle Microbial Methane Production in Oxic Lake Waters
MARCO GUNTHEL
title_short Microbial Methane Production in Oxic Lake Waters
title_full Microbial Methane Production in Oxic Lake Waters
title_fullStr Microbial Methane Production in Oxic Lake Waters
title_full_unstemmed Microbial Methane Production in Oxic Lake Waters
title_sort Microbial Methane Production in Oxic Lake Waters
author_id_str_mv 53b95404bdc1d2930447f9e6ee4d06ca
author_id_fullname_str_mv 53b95404bdc1d2930447f9e6ee4d06ca_***_MARCO GUNTHEL
author MARCO GUNTHEL
author2 MARCO GUNTHEL
format E-Thesis
publishDate 2019
institution Swansea University
doi_str_mv 10.23889/Suthesis.53897
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Biosciences{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Biosciences
document_store_str 1
active_str 0
description Microbial methane production is commonly believed to be an exclusively anaerobic process performed by methanogenic Archaea, but the recent discovery of methane production in oxygenated waters challenges this paradigm and demands re-assessments of the global methane cycle. There are important questions regarding this newly recognized methane source: What are the environmental controls? Who are the responsible organisms? What are the underlying pathways? Is this phenomenon of global relevance? This thesis shows that oxic methane production was a recurring phenomenon in the seasonally stratified oxic water column of Lake Stechlin. Sunlight exposure and phosphorus limitation promoted oxic-water methane accumulations in situ. Bacteria (Cyanobacteria) and Algae (Diatoms, Green Algae, Cryptophytes) produced methane from 13C-labelled bicarbonate in incubation experiments, indicating that oxic methane production was associated with autotrophic carbon fixation. Further, correlations between water column methane concentrations and phytoplankton pigments were observed on the diurnal and seasonal scales. Together, these findings suggest that oxic methane production is a common feature of phytoplankton and likely relevant for limnic systems in general. Balancing the system-wide methane sources and sinks of Lake Stechlin’s surface mixed layer shows the oxic methane source was a substantial contributor to atmospheric methane emission with pronounced short-term dynamics. In addition, empirical modelling based on results presented here and available literature data reveals that oxic methane production in lake waters has global implications: The oxic methane source is predicted to be the primary source of atmospheric methane emission from the mid-water column in lakes larger than 1 km2. Furthermore, the explanatory power of the widely used wind-based models for estimating water-to-air gas emission was much improved by incorporating water- and air temperatures as additional proxy parameters. This thesis shows that oxic methane production is important to lake methane cycling, and global assessments like the upcoming IPCC report should acknowledge the oxic methane source.
published_date 2019-09-01T07:38:15Z
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score 11.056659

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