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Whole-lake estimates of carbon flux through algae and bacteria in benthic and pelagic habitats of clear-water lakes
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
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2009 (Engelska)Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, nr 7, s. 1923-1932Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This study quantified new biomass production of algae and bacteria in both benthic and pelagic habitats of clear-water lakes to contrast how carbon from the atmosphere and terrestrial sources regulates whole-lake metabolism. We studied four small unproductive lakes in subarctic northern Sweden during one summer season. The production of new biomass in both benthic and pelagic habitats was calculated as the sum of autotrophic production by algae and heterotrophic production by bacteria using allochthonous organic carbon (OC). Whole-lake production of new biomass was dominated by the benthic habitat (86% +/- 4% [mean +/- SD]) and by primary production (77% +/- 9%). Still, heterotrophic bacteria fueled by allochthonous OC constituted a significant portion of the new biomass production in both benthic (19% +/- 11%) and pelagic habitats (51% +/- 24%). In addition, overall net production (primary production minus respiration) was close to zero in the benthic habitats but highly negative (-163 +/- 81 mg C.m(-2).d(-1)) in pelagic regions of all lakes. We conclude (1) that allochthonous OC supported a significant part of total production of new biomass in both pelagic and benthic habitats, (2) that benthic habitats dominated the whole-lake production of new biomass, and (3) that respiration and net CO2 production dominated the carbon flux of the pelagic habitats and biomass production dominated the benthic carbon flux. Taken together, these findings suggest that previous investigations have greatly underestimated the productivity of clear-water lakes when benthic autotrophic production and metabolism of allochthonous OC have not been measured.

Ort, förlag, år, upplaga, sidor
Washington, DC, USA: Ecological Society of America , 2009. Vol. 90, nr 7, s. 1923-1932
Identifikatorer
URN: urn:nbn:se:umu:diva-25554DOI: 10.1890/07-1855.1OAI: oai:DiVA.org:umu-25554DiVA, id: diva2:232093
Tillgänglig från: 2009-08-19 Skapad: 2009-08-19 Senast uppdaterad: 2018-06-08Bibliografiskt granskad
Ingår i avhandling
1. Carbon metabolism in clear-water and brown-water lakes
Öppna denna publikation i ny flik eller fönster >>Carbon metabolism in clear-water and brown-water lakes
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The trophic state of lakes is commonly defined by the concentration of nutrients in the water column. High nutrient concentrations generate high phytoplankton production, and lakes with low nutrient concentrations are considered low-productive. This simplified view of lake productivity ignores the fact that benthic primary producers and heterotrophic bacteria can be important basal producers in lake ecosystems.

In this thesis I have studied clear-water and brown-water lakes with respect to primary production, respiration and bacterial production based on allochthonous organic carbon. These processes were quantified in pelagic and benthic habitats on temporal and spatial scales. I also calculated the net ecosystem production of the lakes, defined as the difference between gross primary production (GPP) and respiration (R). The net ecosystem production indicates whether a lake is net heterotrophic (GPP < R), net autotrophic (GPP > R) or in metabolic balance (GPP = R). Net heterotrophic lakes are sources of carbon dioxide (CO2) to the atmosphere since respiration in these lakes, by definition, is subsidized by an external organic carbon source. External organic carbon is transported to lakes from the terrestrial environment via inlets, and can serve as a carbon source for bacteria but it also limits light availability for primary producers by absorbing light.

On a seasonal scale, four of the clear-water lakes studied in this thesis were dominated by primary production in the soft-bottom benthic habitat and by respiration in the pelagic habitat. Concentrations of dissolved organic carbon (DOC) were low in the lakes, but still high enough to cause the lakes to be net heterotrophic. However, the lakes were not low-productive due to the high production in the benthic habitat. One of the clear-water lakes was studied also during the winter and much of the respiration under ice was supported by the benthic primary production from the previous summer. This is in contrast to brown-water lakes where winter respiration is suggested to be supported by allochthonous organic carbon.

By studying lakes in a DOC gradient (i.e. from clear-water to brown-water lakes) I could draw two major conclusions. The lakes became less productive since benthic primary production decreased with increasing light extinction, and the lakes became larger sources of CO2 to the atmosphere since pelagic respiration was subsidized by allochthonous organic carbon. Thus, lake carbon metabolism can have an important role in the global carbon cycle due to their processing of terrestrial organic carbon and to their possible feedback effects on the climate system.

Ort, förlag, år, upplaga, sidor
Umeå: Institutionen för ekologi, miljö och geovetenskap, Department of Ecology and Environmental Sciences, 2010. s. 31
Nyckelord
clear-water lakes, brown-water lakes, primary production, bacterial production, benthic, pelagic, net ecosystem production, allochthonous organic carbon, CO2, DOC
Nationell ämneskategori
Naturgeografi Ekologi
Forskningsämne
limnologi; naturgeografi
Identifikatorer
urn:nbn:se:umu:diva-33488 (URN)978-91-7264-954-5 (ISBN)
Disputation
2010-05-21, KBC, Stora Hörsalen (KB3B1), Umeå Universitet, Umeå, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2010-04-29 Skapad: 2010-04-26 Senast uppdaterad: 2018-06-08Bibliografiskt granskad

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