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Magnitude and regulation of bacterioplankton respiratory quotient across freshwater environmental gradients

Berggren, Martin LU ; Lapierre, Jean-Francois and del Giorgio, Paul A. (2012) In The Isme Journal 6(5). p.984-993
Abstract
Bacterioplankton respiration (BR) may represent the largest single sink of organic carbon in the biosphere and constitutes an important driver of atmospheric carbon dioxide (CO2) emissions from freshwaters. Complete understanding of BR is precluded by the fact that most studies need to assume a respiratory quotient (RQ; mole of CO2 produced per mole of O-2 consumed) to calculate rates of BR. Many studies have, without clear support, assumed a fixed RQ around 1. Here we present 72 direct measurements of bacterioplankton RQ that we carried out in epilimnetic samples of 52 freshwater sites in Quebec (Canada), using O-2 and CO2 optic sensors. The RQs tended to converge around 1.2, but showed large variability (s.d.=0.45) and significant... (More)
Bacterioplankton respiration (BR) may represent the largest single sink of organic carbon in the biosphere and constitutes an important driver of atmospheric carbon dioxide (CO2) emissions from freshwaters. Complete understanding of BR is precluded by the fact that most studies need to assume a respiratory quotient (RQ; mole of CO2 produced per mole of O-2 consumed) to calculate rates of BR. Many studies have, without clear support, assumed a fixed RQ around 1. Here we present 72 direct measurements of bacterioplankton RQ that we carried out in epilimnetic samples of 52 freshwater sites in Quebec (Canada), using O-2 and CO2 optic sensors. The RQs tended to converge around 1.2, but showed large variability (s.d.=0.45) and significant correlations with major gradients of ecosystem-level, substrate-level and bacterial community-level characteristics. Experiments with natural bacterioplankton using different single substrates suggested that RQ is intimately linked to the elemental composition of the respired compounds. RQs were on average low in net autotrophic systems, where bacteria likely were utilizing mainly reduced substrates, whereas we found evidence that the dominance of highly oxidized substrates, for example, organic acids formed by photo-chemical processes, led to high RQ in the more heterotrophic systems. Further, we suggest that BR contributes to a substantially larger share of freshwater CO2 emissions than presently believed based on the assumption that RQ is similar to 1. Our study demonstrates that bacterioplankton RQ is not only a practical aspect of BR determination, but also a major ecosystem state variable that provides unique information about aquatic ecosystem functioning. The ISME Journal (2012) 6, 984-993; doi:10.1038/ismej.2011.157; published online 17 November 2011 (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
DISSOLVED ORGANIC-MATTER, CALCITE PRECIPITATION, GROWTH EFFICIENCY, CARBOXYLIC-ACIDS, BACTERIAL-GROWTH, LAKE ECOSYSTEMS, CARBON, METABOLISM, CO2, PHYTOPLANKTON
in
The Isme Journal
volume
6
issue
5
pages
984 - 993
publisher
Nature Publishing Group
external identifiers
  • scopus:84859918979
ISSN
1751-7362
DOI
10.1038/ismej.2011.157
project
BECC
language
English
LU publication?
no
id
f8cfe109-e0a1-4d25-b0eb-12289da8eebd (old id 3055015)
date added to LUP
2012-11-27 16:20:48
date last changed
2017-09-24 03:00:08
@article{f8cfe109-e0a1-4d25-b0eb-12289da8eebd,
  abstract     = {Bacterioplankton respiration (BR) may represent the largest single sink of organic carbon in the biosphere and constitutes an important driver of atmospheric carbon dioxide (CO2) emissions from freshwaters. Complete understanding of BR is precluded by the fact that most studies need to assume a respiratory quotient (RQ; mole of CO2 produced per mole of O-2 consumed) to calculate rates of BR. Many studies have, without clear support, assumed a fixed RQ around 1. Here we present 72 direct measurements of bacterioplankton RQ that we carried out in epilimnetic samples of 52 freshwater sites in Quebec (Canada), using O-2 and CO2 optic sensors. The RQs tended to converge around 1.2, but showed large variability (s.d.=0.45) and significant correlations with major gradients of ecosystem-level, substrate-level and bacterial community-level characteristics. Experiments with natural bacterioplankton using different single substrates suggested that RQ is intimately linked to the elemental composition of the respired compounds. RQs were on average low in net autotrophic systems, where bacteria likely were utilizing mainly reduced substrates, whereas we found evidence that the dominance of highly oxidized substrates, for example, organic acids formed by photo-chemical processes, led to high RQ in the more heterotrophic systems. Further, we suggest that BR contributes to a substantially larger share of freshwater CO2 emissions than presently believed based on the assumption that RQ is similar to 1. Our study demonstrates that bacterioplankton RQ is not only a practical aspect of BR determination, but also a major ecosystem state variable that provides unique information about aquatic ecosystem functioning. The ISME Journal (2012) 6, 984-993; doi:10.1038/ismej.2011.157; published online 17 November 2011},
  author       = {Berggren, Martin and Lapierre, Jean-Francois and del Giorgio, Paul A.},
  issn         = {1751-7362},
  keyword      = {DISSOLVED ORGANIC-MATTER,CALCITE PRECIPITATION,GROWTH EFFICIENCY,CARBOXYLIC-ACIDS,BACTERIAL-GROWTH,LAKE ECOSYSTEMS,CARBON,METABOLISM,CO2,PHYTOPLANKTON},
  language     = {eng},
  number       = {5},
  pages        = {984--993},
  publisher    = {Nature Publishing Group},
  series       = {The Isme Journal},
  title        = {Magnitude and regulation of bacterioplankton respiratory quotient across freshwater environmental gradients},
  url          = {http://dx.doi.org/10.1038/ismej.2011.157},
  volume       = {6},
  year         = {2012},
}