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High spatial variability in stream k600 revealed by turbulence measurements – implications for scaling GHG emissions
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.ORCID iD: 0000-0002-8763-3139
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences Ecology Environmental Sciences
Research subject
Biology with specialization in Limnology
Identifiers
URN: urn:nbn:se:uu:diva-307785OAI: oai:DiVA.org:uu-307785DiVA: diva2:1049318
Available from: 2016-11-24 Created: 2016-11-21 Last updated: 2016-11-24
In thesis
1. Gas Exchange over Aquatic Interfaces and its Importance for Greenhouse Gas Emission
Open this publication in new window or tab >>Gas Exchange over Aquatic Interfaces and its Importance for Greenhouse Gas Emission
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aquatic ecosystems play a substantial role in global cycling of carbon (C), despite covering only about 4% of the earth surface. They emit large amounts of greenhouse gases (GHG) to the atmosphere, comparable to the amount of C stored annually in terrestrial ecosystems. In addition, C can be buried in lake sediments. Headwater systems are located at the interface of the terrestrial and aquatic environment, and are first in line to process terrestrial C and throughout its journey through the aquatic continuum. The uncertainties in global estimates of aquatic GHG emissions are largely related to these headwater systems, as they are highly variable in time and space, and underrepresented in global assessments. The overall aim of this thesis was therefore to study GHG exchange between sediment, water and air in headwater systems, from both an ecosystem perspective and at the small scale of physical drivers of gas exchange.

This thesis demonstrates that carbon dioxide (CO2) emission from headwater systems, especially streams, was the main pathway of C loss from surface waters from a lake catchment. Of the total aquatic CO2-emission of the catchment, 65% originated from stream systems that covered only 0.1% of the total catchment area. The gas transfer velocity (k) was the main driver of stream CO2-emission, but there was a high variability in k on small spatial scales (meters). This variability may have implications for upscaling GHG emissions, especially when using scaled k estimates. Lake sediments only contributed 16% to total lake C emission, but in reality, sediment C emission is probably even lower because experimentally determined sediment C flux returns high estimates that are biased since artificially induced turbulence enhances C flux rates beyond in-situ conditions. When sediment C flux is estimated in-situ, in natural bottom water turbulence conditions, flux rates were lower than those estimated experimentally.

Conclusively, this thesis shows that GHG emissions from small aquatic ecosystems are dominant over other aquatic C fluxes and that our current knowledge regarding the physical processes controlling gas exchange from different small aquatic systems is limited, implying an inherent uncertainty of GHG emission estimates from small aquatic ecosystems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1457
Keyword
gas exchange, lake, stream, lake sediment, headwaters, carbon dioxide, methane, greenhouse gas emission, carbon, turbulence
National Category
Natural Sciences Ecology Environmental Sciences
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-307792 (URN)978-91-554-9764-4 (ISBN)
Public defence
2017-01-20, Ekmansalen, EBC, Norbyvägen 14, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-12-21 Created: 2016-11-21 Last updated: 2016-12-28

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CiteExportLink to record
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Citation style
  • apa
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