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Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Naturgeografi)
Skogens ekologi och skötsel, SLU, Umeå.
Skogens ekologi och skötsel, SLU, Umeå.
Naturgeografi och Ekosystemanalys, Lunds universitet, Lund.
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2010 (English)In: The ISME Journal, ISSN 1751-7362, Vol. 4, no 3, 408-416 p.Article in journal (Refereed) Published
Abstract [en]

Carboxylic acids (CAs), amino acids (AAs) and carbohydrates (CHs) in dissolved free forms can be readily assimilated by aquatic bacteria and metabolized at high growth efficiencies. Previous studies have shown that these low-molecular-weight (LMW) substrates are released by phytoplankton but also that unidentified LMW compounds of terrestrial origin is a subsidy for bacterial metabolism in unproductive freshwater systems. We tested the hypothesis that different terrestrially derived CA, AA and CH compounds can offer substantial support for aquatic bacterial metabolism in fresh waters that are dominated by allochthonous dissolved organic matter (DOM). Drainage water from three catchments of different characters in the Krycklan experimental area in Northern Sweden were studied at the rising and falling limb of the spring flood, using a 2-week bioassay approach. A variety of CA, AA and CH compounds were significantly assimilated by bacteria, meeting 15–100% of the bacterial carbon demand and explaining most of the observed variation in bacterial growth efficiency (BGE; R2=0.66). Of the 29 chemical species that was detected, acetate was the most important, representing 45% of the total bacterial consumption of all LMW compounds. We suggest that LMW organic compounds in boreal spring flood drainage could potentially support all in situ bacterial production in receiving lake waters during periods of weeks to months after the spring flood.

Place, publisher, year, edition, pages
London: Nature Publishing Group , 2010. Vol. 4, no 3, 408-416 p.
Keyword [en]
freshwater, growth efficiency, heterotrophic bacteria, low-molecular-weight DOM
National Category
Ecology
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:umu:diva-30050DOI: 10.1038/ismej.2009.120ISI: 000274800100010OAI: oai:DiVA.org:umu-30050DiVA: diva2:279148
Available from: 2009-12-01 Created: 2009-12-01 Last updated: 2011-04-26Bibliographically approved
In thesis
1. Bacterial use of allochthonous organic carbon for respiration and growth in boreal freshwater systems
Open this publication in new window or tab >>Bacterial use of allochthonous organic carbon for respiration and growth in boreal freshwater systems
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aquatic systems worldwide receive large amounts of organic carbon from terrestrial sources. This ‘allochthonous’ organic carbon (AlloOC) affects critical physical and chemical properties of freshwater ecosystems, with consequences for food web structures and exchange of greenhouse gases with the atmosphere. In the boreal region, loadings of AlloOC are particularly high due to leaching from huge organic deposits in boreal forest, mire and tundra soils.

A main process of AlloOC turnover in aquatic systems is its use by heterotrophic bacteria. Applying a bioassay approach, I measured the respiration and growth (production) of bacteria in northern Sweden, in streams and lakes almost totally dominated by AlloOC. The objective was to elucidate how variations in AlloOC source, age, composition and concentration impact on its use by aquatic bacteria, and how AlloOC properties, in turn, are regulated by landscape composition and by hydrology.

The bacterial respiration (30-309 µg C L-1 d-1) was roughly proportional to the concentration of AlloOC (7-47 mg C L-1), but not significantly related to AlloOC source or character. Bacterial production (4-94 µg C L-1 d-1), on the other hand, was coupled to the AlloOC character, rather than concentration. A strong coupling to AlloOC character was also found for bacterial growth efficiency (0.06-0.51), i.e. production per unit of assimilated carbon. Bacterial production and growth efficiency increased with rising concentrations of low molecular weight AlloOC (carboxylic acids, free amino acids and simple carbohydrates). While the total AlloOC concentrations generally were the highest in mire-dominated catchments, low molecular weight AlloOC concentrations were much higher in forested catchments, compared to mire-dominated. These patterns were reflected in a strong landscape control of aquatic bacterial metabolism. Moreover, high flow episodes increased the export of organic carbon from forests, in relation to the export from mires, stimulating the bacterial production and growth efficiency in streams with mixed (forest and mire) catchments. The potential of AlloOC to support efficient bacterial growth decreased on time-scales of weeks to months, as the AlloOC was aged in laboratory or lake in situ conditions.

To conclude, landscape, hydrology and conditions which determine AlloOC age have large influence on bacterial metabolism in boreal aquatic systems. Considering the role of bacteria in heterotrophic food chains, these factors can have spin-off effects on the structure and function of boreal aquatic ecosystems.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2009. 17 + 4 papers p.
Keyword
lakes, streams, boreal, bacterial respiration, bacterial production, bacterial growth efficiency, allochthonous organic carbon, low molecular weight compounds
Research subject
Physical Geography
Identifiers
urn:nbn:se:umu:diva-30051 (URN)978-91-7264-870-8 (ISBN)
Public defence
2010-01-15, Stora hörsalen, KBC, Linnaeus väg 6, Universitetsområdet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2009-12-04 Created: 2009-12-01 Last updated: 2009-12-04Bibliographically approved

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Publisher's full textThe ISME Journal - Abstract of article: Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources

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