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Microbial activity within a subaqueous dune in a large lowland river (River Elbe, Germany)
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Limnologi.
2004 (English)In: AQUATIC MICROBIAL ECOLOGY, Vol. 36:, 83–97- p.Article in journal (Refereed) Published
Abstract [en]

Microbial processes within subaqueous dunes of large rivers are important for organic

matter retention and decomposition but have rarely been examined. We investigated 3 morphodynamically

defined zones (stoss side, crestal plateau, and lee side) within a subaqueous dune in the

8th-order River Elbe. Analysis of flow velocity, vertical hydraulic gradient, concentration of mobile

fine interstitial particles, and the quantity and biochemical quality of sedimentary organic matter

indicated that the stoss and the lee sides of the dune were focal zones of particulate matter retention

due to infiltration and sedimentation processes. Bacterial abundance and most measures of microbial

activity (sediment community respiration and activities of the extracellular enzymes β-glucosidase,

leucine aminopeptidase, β-xylosidase, and exo-1,4-β-glucanase) were significantly higher in these

zones than in the plateau. Increases in bacterial abundance and microbial activity were closely correlated

with protein, carbohydrates, nitrogen and phaeopigments associated with high-quality particulate

organic matter. Our findings showed that the morphodynamic differentiation of the subaqueous

dune resulted in the formation of distinct functional zones in the sediment. The underlying

mechanisms can be conceptually summarized by a 2-stage regulatory hierarchy. Microbial activities

were controlled directly by the input of dissolved oxygen and easily degradable microbial substrates,

and indirectly by hydromorphological processes. We conclude that the subaqueous dune functioned

as an efficient filter of particulate organic matter, and that the stoss and the lee sides of this river bedform

were focal sites of microbial carbon mineralisation in the large river ecosystem.

Place, publisher, year, edition, pages
2004. Vol. 36:, 83–97- p.
Keyword [en]
Extracellular enzymes · Particulate organic matter · Subaqueous dune · Sediments ·River · Bacteria · Hydrodynamics
Identifiers
URN: urn:nbn:se:uu:diva-72445OAI: oai:DiVA.org:uu-72445DiVA: diva2:100356
Available from: 2007-02-14 Created: 2007-02-14 Last updated: 2011-01-12

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http://www.int-res.com/articles/ame2004/36/a036p083.pdf

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Fischer, Helmut

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