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Carbon Dioxide Supersaturation in Lakes – Causes, Consequences and Sensitivity to Climate Change
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och evolution, Limnologi.
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis , 2005. , s. 42
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 90
Nyckelord [en]
Biology, carbon dioxide, boreal lakes, respiration, dissolved organic carbon, climate change
Nyckelord [sv]
Biologi
Nationell ämneskategori
Biologiska vetenskaper
Identifikatorer
URN: urn:nbn:se:uu:diva-5920ISBN: 91-554-6329-0 (tryckt)OAI: oai:DiVA.org:uu-5920DiVA, id: diva2:166911
Disputation
2005-10-14, Ekmansalen, Kärnhuset, EBC, Norbyvägen 14, Uppsala, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2009-03-30Bibliografiskt granskad
Delarbeten
1. The catchment and climate regulation of pCO2 in boreal lakes
Öppna denna publikation i ny flik eller fönster >>The catchment and climate regulation of pCO2 in boreal lakes
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2003 (Engelska)Ingår i: Global Change Biology, Vol. 9, s. 630-641Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93433 (URN)
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2018-05-21
2. Microbial and photochemical mineralization in the water-column of two boreal lakes during mid-summer conditions
Öppna denna publikation i ny flik eller fönster >>Microbial and photochemical mineralization in the water-column of two boreal lakes during mid-summer conditions
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(Engelska)Ingår i: Artikel i tidskrift (Refereegranskat) Submitted
Identifikatorer
urn:nbn:se:uu:diva-93434 (URN)
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2018-05-21
3. Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
Öppna denna publikation i ny flik eller fönster >>Contribution of sediment respiration to summer CO2 emission from low productive boreal and subarctic lakes
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2005 (Engelska)Ingår i: Microbial Ecology, ISSN 0095-3628, E-ISSN 1432-184X, Vol. 50, nr 4, s. 529-535Artikel i tidskrift (Refereegranskat) 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.

Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:uu:diva-93435 (URN)10.1007/s00248-005-5007-x (DOI)
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2018-05-21Bibliografiskt granskad
4. Role of lakes for organic carbon cycling in the boreal zone
Öppna denna publikation i ny flik eller fönster >>Role of lakes for organic carbon cycling in the boreal zone
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2004 (Engelska)Ingår i: Global Change Biology, Vol. 10, s. 141-147Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93436 (URN)
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2018-05-21
5. Temperature independence of carbon dioxide supersaturation in global lakes
Öppna denna publikation i ny flik eller fönster >>Temperature independence of carbon dioxide supersaturation in global lakes
2005 (Engelska)Ingår i: Global Biogeochemical Cycles, Vol. 19, nr GB2003, s. doi:10.1029/2004GB002264-Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:uu:diva-93437 (URN)
Tillgänglig från: 2005-09-21 Skapad: 2005-09-21 Senast uppdaterad: 2018-05-21

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