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Impact of photochemical degradation of DOC on bacterial respiratory quotient in aquatic ecosystems

Allesson, Lina and Berggren, Martin LU (2015) ASLO 2015 Aquatic Sciences Meeting
Abstract
Many studies assume a respiratory quotient (RQ = CO2 produced per O2 consumed, by moles) of ~1 to calculate bacterial respiration from measured O2 consumption rates. However, the theoretical value of RQ varies with the elemental composition of the compound being decomposed. Photo-oxidation of DOC results in compounds of oxygen-rich organic acids which, theoretically, should result in elevated RQ. We performed organic acid analysis and used optic gas-pressure sensors to monitor the bacterial RQ in irradiated and non-irradiated water from five lakes, plus in Leonardite-extracted humic acid solutions. In irradiated samples, the RQs generally were significantly higher than in the non-irradiated samples. Additionally, we found that enrichment... (More)
Many studies assume a respiratory quotient (RQ = CO2 produced per O2 consumed, by moles) of ~1 to calculate bacterial respiration from measured O2 consumption rates. However, the theoretical value of RQ varies with the elemental composition of the compound being decomposed. Photo-oxidation of DOC results in compounds of oxygen-rich organic acids which, theoretically, should result in elevated RQ. We performed organic acid analysis and used optic gas-pressure sensors to monitor the bacterial RQ in irradiated and non-irradiated water from five lakes, plus in Leonardite-extracted humic acid solutions. In irradiated samples, the RQs generally were significantly higher than in the non-irradiated samples. Additionally, we found that enrichment with inorganic nutrients (N + P) consistently increased the RQs in bioassays based on humic acid extracts. This study shows that bacterial RQ varies depending on the state of oxidation of the DOC and the access to nutrients in the water. Our results imply that RQ can be systematically higher than 1 when the bacterial metabolism is to a large extent based on photo-chemically produced substrates. (Less)
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author
organization
publishing date
type
Contribution to conference
publication status
published
subject
pages
1 pages
conference name
ASLO 2015 Aquatic Sciences Meeting
conference location
Granada, Spain
conference dates
2015-02-22 - 2015-12-27
language
English
LU publication?
yes
id
b3ec5db2-1c7d-4895-8abf-181cf0c70723
date added to LUP
2018-07-05 15:45:54
date last changed
2018-07-06 16:46:23
@misc{b3ec5db2-1c7d-4895-8abf-181cf0c70723,
  abstract     = {Many studies assume a respiratory quotient (RQ = CO2 produced per O2 consumed, by moles) of ~1 to calculate bacterial respiration from measured O2 consumption rates. However, the theoretical value of RQ varies with the elemental composition of the compound being decomposed. Photo-oxidation of DOC results in compounds of oxygen-rich organic acids which, theoretically, should result in elevated RQ. We performed organic acid analysis and used optic gas-pressure sensors to monitor the bacterial RQ in irradiated and non-irradiated water from five lakes, plus in Leonardite-extracted humic acid solutions. In irradiated samples, the RQs generally were significantly higher than in the non-irradiated samples. Additionally, we found that enrichment with inorganic nutrients (N + P) consistently increased the RQs in bioassays based on humic acid extracts. This study shows that bacterial RQ varies depending on the state of oxidation of the DOC and the access to nutrients in the water. Our results imply that RQ can be systematically higher than 1 when the bacterial metabolism is to a large extent based on photo-chemically produced substrates.},
  author       = {Allesson, Lina and Berggren, Martin},
  language     = {eng},
  location     = {Granada, Spain},
  pages        = {1},
  title        = {Impact of photochemical degradation of DOC on bacterial respiratory quotient in aquatic ecosystems},
  year         = {2015},
}