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Pelagic and benthic net production of dissolved inorganic carbon in an unproductive subarctic lake
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
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2007 (English)In: Freshwater Biology, Vol. 52, no 3, 549-560 p.Article in journal (Refereed) Published
Abstract [en]

1. Both the pelagic and benthic net dissolved inorganic carbon (DIC) productions were measured in situ on four occasions from June to September 2004, in the unproductive Lake Diktar-Erik in subarctic Sweden. The stable isotopic signal (δ13C) of respired organic material was estimated from hypolimnion water data and data from a laboratory incubation using epilimnion water.

2. Both pelagic and benthic habitats were net heterotrophic during the study period, with a total net DIC production of 416 mg C m-2 day-1, of which the pelagic habitat contributed approximately 85%. The net DIC production decreased with depth both in the pelagic water and in the sediments, and most of the net DIC production occurred in the upper water column.

3. Temporal variations in both pelagic and benthic DIC production were small, although we observed a significant decrease in pelagic net DIC production after the autumn turnover. Water temperature was the single most important factor explaining temporal and vertical variations in pelagic DIC production. No single factor explained more than 10% of the benthic net DIC production, which probably was regulated by several interacting factors.

4. Pelagic DIC production, and thus most of the whole-lake net production of DIC, was mainly due to the respiration of allochthonous organic carbon. Stable isotope data inferred that nearly 100% of accumulated DIC in the hypolimnion water had an allochthonous carbon source. Similarly, in the laboratory incubation using epilimnion water, c. 85% of accumulated DIC was indicated to have an allochthonous organic carbon source.

Place, publisher, year, edition, pages
2007. Vol. 52, no 3, 549-560 p.
URN: urn:nbn:se:umu:diva-11879DOI: 10.1111/j.1365-2427.2007.01725.xOAI: diva2:151550
Available from: 2007-03-15 Created: 2007-03-15 Last updated: 2009-11-10Bibliographically approved
In thesis
1. Production and emission of CO2 in two unproductive lakes in northern Sweden
Open this publication in new window or tab >>Production and emission of CO2 in two unproductive lakes in northern Sweden
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Unproductive lakes are one of few natural landscape compartments with net release of carbon to the atmosphere. Lakes also generally decrease the net terrestrial carbon uptake, since most of the CO2 production in unproductive lakes are derived from organic carbon produced on land (e.g. in forests). High latitude lakes are predicted to be particularly affected by the global climate change. The carbon cycling in these lakes and their role in the landscape are therefore important to study.

In this thesis, carbon turnover processes were studied in two lakes above the arctic circle (Lake Diktar-Erik and Lake Merasjärvi) in year 2004 and 2005. Both lakes were net heterotrophic, with large variations in CO2 concentrations both on shorter (30min) and longer (24h) time-scales. The pelagic habitat supported a major part of the net production of CO2, with larger dynamics in the CO2 production than the sediments. The CO2 variations of the surface water were related to respiration of allochthonous organic carbon, and were affected by the concentration and quality of the DOC, as well as the whole lake water temperatures, and vertical water movements.

The emission of CO2 from Lake Merasjärvi was measured with the eddy covariance tech­nique. The results showed that the gas transfer rate during moderate winds were higher than expected, causing the two most commonly used models to underestimate the long term fluxes of CO2 from the lake.

Taken together, the results of the thesis show that the studied lakes contributed to bring terrestrial organic carbon back into the atmosphere, driven by a substantial internal CO2 production based on mineralization of allochthonous organic carbon. Major results are that the eddy covariance technique indicated that commonly used models tend to underestimate the net release rate of CO2 from lakes to the atmosphere, and that the lake CO2 dynamics can be the results of interactions between biogeochemical and physical processes in the lake water.

Place, publisher, year, edition, pages
Umeå: Institutionen för Ekologi, miljö och geovetenskap, Umeå universitet, 2009. 28 p.
lake, carbon dioxide, organic carbon, inorganic carbon, boreal, arctic, DOC, DIC, CO2, emission, thermal stratification, allochthonous organic carbon
National Category
Ecology Physical Geography
Research subject
Physical Geography
urn:nbn:se:umu:diva-26967 (URN)978-91-7264-878-4 (ISBN)
Public defence
2009-12-03, Naturvetarhuset hörsal N450, Johan Bures Väg, Umeå universitet, Umeå, 10:00 (Swedish)
Available from: 2009-11-12 Created: 2009-11-04 Last updated: 2009-11-13Bibliographically approved

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