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Distinct patterns of microbial metabolism associated to riverine dissolved organic carbon of different source and quality

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Author

Summary, in English

Dissolved organic carbon (DOC) in rivers contains a wide range of molecules that can be assimilated by microbes. However, there is today no integrated understanding of how the source and composition of this DOC regulate the extent to which the DOC can support microbial growth and respiration. We analyzed patterns in microbial metabolism of DOC from different streams and rivers in Québec, by combining short-term bacterial production and respiration measurements with long-term DOC loss and analyses of bacterial use of different single substrates. We show that distinct metabolic patterns indeed exist across catchments, reflecting the varying nature and sources of the DOC. For example, DOC from forest headwaters systematically supported the highest bacterial growth efficiency (BGE) that was recorded, while in contrast DOC in peat bog drainage was used with significantly lower BGE. The carbon consumption in clear mountain rivers, possibly represented by autochthonous algal DOC, supported the highest bacterial respiration rates and the highest long-term DOC losses. By using principle component analysis, we demonstrate how the major axes of variation in all of the measured metabolic responses are tightly connected to spectrofluorometrical DOC composition indicators and to isotopic indicators of DOC source. If causality is assumed, our results imply that changes in DOC supply from different sources, for example, caused by land use or climate change, should result in dramatic changes in the patterns of aquatic microbial metabolism and thus in altered aquatic ecosystem functioning, with likely consequences for food-web structures and greenhouse gas balances.

Publishing year

2015

Language

English

Pages

989-999

Publication/Series

Journal of Geophysical Research - Biogeosciences

Volume

120

Issue

6

Document type

Journal article

Publisher

Wiley

Topic

  • Earth and Related Environmental Sciences

Keywords

  • dissolved organic carbon
  • microbial metabolism

Status

Published

Project

  • Aquatic greenhouse gas emissions mediated by microbial use of allochthonous organic carbon of varying source and quality

ISBN/ISSN/Other

  • ISSN: 2169-8953