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Mineralization of organic carbon in lake sediments: temperature sensitivity and a comparison to soils
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
The Department of Thematic Studies - Water and Environmental Studies Linköping university.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Temperature alone can explain a great amount of variation in sediment organic carbon (OC) mineralization. Studies on decomposition of soil OC suggest that the temperature sensitivity is different for the decomposition of labile and recalcitrant OC, but lake sediments with different contributions of labile and recalcitrant components have been reported to show similar temperature sensitivities. Sediment mineralization is typically measured in short-term incubations. However, whether the mineralization of OC in sediments dominated by recalcitrant and labile OC have different temperature sensitivities at the longer term is not clear. Here we show that during 5 months of continuous incubation of contrasting boreal lake sediments, sediment mineralization was strongly dependent on temperature and OC quality/origin but temperature sensitivity was similar across lakes and over time. Sediment mineralization showed low overall rates in spite of low apparent activation energy (Ea) compared to published rates of soil and litter mineralization. The fraction of the total OC pool that was lost during 5 months varied between 0.4 and 14%. The non-buried sediment OC pool was lost slowly, with apparent turnover times between 2.5 and 32 years. At a large scale, lake sediments, by showing lower mineralization rates than soils are more effective as carbon sinks.

 

Keyword [en]
lake sediment, mineralization, temperature sensitivity, organic carbon, turnover time
National Category
Ecology
Research subject
Limnology
Identifiers
URN: urn:nbn:se:uu:diva-150714OAI: oai:DiVA.org:uu-150714DiVA: diva2:408446
Available from: 2011-04-04 Created: 2011-04-04 Last updated: 2017-11-30
In thesis
1. Boreal Lake Sediments as Sources and Sinks of Carbon
Open this publication in new window or tab >>Boreal Lake Sediments as Sources and Sinks of Carbon
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Inland waters process large amounts of organic carbon, contributing to CO2 and CH4 emissions, as well as storing organic carbon (OC) over geological timescales. Recently, it has been shown that the magnitude of these processes is of global significance. It is therefore important to understand what regulates OC cycling in inland waters and how is that affected by climate change. This thesis investigates the constraints on microbial processing of sediment OC, as a key factor of the carbon cycling in boreal lakes.

Sediment bacterial metabolism was primarily controlled by temperature but also regulated by OC quality/origin. Temperature sensitivity of sediment OC mineralization was similar in contrasting lakes and over long-term. Allochthonous OC had a strong constraining effect on sediment bacterial metabolism and biomass, with increasingly allochthonous sediments supporting decreasing bacterial metabolism and biomass. The bacterial biomass followed the same pattern as bacterial activity and was largely regulated by similar factors. The rapid turnover of bacterial biomass as well as the positive correlation between sediment mineralization and bacterial biomass suggest a limited effect of bacterial grazing. Regardless of the OC source, the sediment microbial community was more similar within season than within lakes.

A comparison of data from numerous soils as well as sediments on the temperature response of OC mineralization showed higher temperature sensitivity of the sediment mineralization. Furthermore, the low rates of areal OC mineralization in sediments compared to soils suggest that lakes sediments are hotspots of OC sequestration.

Increased sediment mineralization due to increase in temperature in epilimnetic sediments can significantly reduce OC burial in boreal lakes. An increase of temperature, as predicted for Northern latitudes, under different climate warming scenarios by the end of the twenty-first century, resulted in 4–27% decrease in lake sediment OC burial for the entire boreal zone.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 39 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 823
Keyword
boreal lakes, allochthonous, lake sediments, sediment mineralization, bacterial production, bacterial biomass, carbon cycle
National Category
Ecology
Research subject
Limnology
Identifiers
urn:nbn:se:uu:diva-150709 (URN)978-91-554-8072-1 (ISBN)
Public defence
2011-05-31, Friessalen, Evolutionary Biology Centre (EBC), Norbyvägen 18, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2011-05-10 Created: 2011-04-04 Last updated: 2011-07-01Bibliographically approved

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Sobek, SebastianTranvik, Lars J.

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