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Carbon Dioxide Supersaturation in Lakes – Causes, Consequences and Sensitivity to Climate Change
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The global carbon cycle is intimately linked with the earth’s climate system. Knowledge about carbon cycling in the biosphere is therefore crucial for predictions of climate change. This thesis investigates the carbon dioxide balance of Swedish boreal lakes, its regulation, significance to the carbon budget of the boreal landscape, and sensitivity to climate change.

Swedish boreal lakes were almost exclusively supersaturated in CO2 with respect to the atmosphere, resulting in an emission of CO2 from lakes to the atmosphere. Lake pCO2 was closely related to the concentration of terrigenous dissolved organic carbon (DOC), indicating that the utilization of terrigenous DOC by lake bacteria is a major source of CO2. This conclusion is supported by independent field studies, showing that net plankton respiration accounts for most of the CO2 emitted from Swedish boreal lakes, while photochemical mineralization and sediment respiration were less important.

Mineralization of terrigenous DOC and subsequent emission of CO2 from lakes to the atmosphere was a major carbon loss factor in 21 major Swedish boreal catchments, removing 30-80% of the organic carbon exported from terrestrial soils to surface waters. Lake CO2 emission is in the same order of magnitude as organic carbon accumulation in boreal forest soils, and should therefore be included in the carbon budget of the boreal landscape.

In a set of nearly 5000 global lakes, DOC concentration was a much more important regulator of lake pCO2 than temperature. Climate change will therefore affect the carbon balance of lakes primarily via alterations in terrestrial DOC export, rather than via changes in temperature per se. Both current observations and models of future climate suggest an increasing export of terrigenous DOC from many Scandinavian catchments. Hence, there probably is a current trend towards higher CO2 emission from Swedish boreal lakes, which is likely to continue in the future.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2005. , p. 42
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 90
Keywords [en]
Biology, carbon dioxide, boreal lakes, respiration, dissolved organic carbon, climate change
Keywords [sv]
Biologi
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-5920ISBN: 91-554-6329-0 (print)OAI: oai:DiVA.org:uu-5920DiVA, id: diva2:166911
Public defence
2005-10-14, Ekmansalen, Kärnhuset, EBC, Norbyvägen 14, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2009-03-30Bibliographically approved
List of papers
1. The catchment and climate regulation of pCO2 in boreal lakes
Open this publication in new window or tab >>The catchment and climate regulation of pCO2 in boreal lakes
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2003 (English)In: Global Change Biology, Vol. 9, p. 630-641Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-93433 (URN)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2018-05-21
2. Microbial and photochemical mineralization in the water-column of two boreal lakes during mid-summer conditions
Open this publication in new window or tab >>Microbial and photochemical mineralization in the water-column of two boreal lakes during mid-summer conditions
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(English)In: Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-93434 (URN)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2018-05-21
3. Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
Open this publication in new window or tab >>Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
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2005 (English)In: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 50, no 4, p. 529-535Article in journal (Refereed) Published
Abstract [en]

We measured sediment production of carbon dioxide (CO2) and methane (CH4) and the net flux of CO2 across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were made in situ under ambient light conditions. The flux of CO2 between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m−2 day−1 from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated to dissolved organic carbon (DOC) concentration in the water (r 2 = 0.61). The net flux of CO2 across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed layer (r 2 = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration. Lakes with DOC concentrations <5.6 mg L−1 had net consumption of CO2 in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic (<2.6 mg L−1) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-93435 (URN)10.1007/s00248-005-5007-x (DOI)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2018-05-21Bibliographically approved
4. Role of lakes for organic carbon cycling in the boreal zone
Open this publication in new window or tab >>Role of lakes for organic carbon cycling in the boreal zone
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2004 (English)In: Global Change Biology, Vol. 10, p. 141-147Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-93436 (URN)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2018-05-21
5. Temperature independence of carbon dioxide supersaturation in global lakes
Open this publication in new window or tab >>Temperature independence of carbon dioxide supersaturation in global lakes
2005 (English)In: Global Biogeochemical Cycles, Vol. 19, no GB2003, p. doi:10.1029/2004GB002264-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-93437 (URN)
Available from: 2005-09-21 Created: 2005-09-21 Last updated: 2018-05-21

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