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In situ plankton community respiration measurements show low respiratory quotients in a eutrophic lake

Münzner, Karla LU and Berggren, Martin LU (2018) ASLO Summer Meeting 2018
Abstract
Planktonic community respiration is an important carbon cycling process, typically quantified by converting measured values of dissolved oxygen consumption rates into carbondioxide production rates using a respiratory quotient of 1 (RQ = carbondioxide per oxygen by moles). However, the true variability in planktonic RQs between different aquatic ecosystems is poorly understood. We conducted in situ RQ measurements in a eutrophic lake (Sweden) to test the hypothesis that the RQ is systematically below 1 when the organic matter pool is dominated by reduced algal-derived substrates that theoretically require large amounts of oxygen to mineralize. The RQ was significantly lower than 1, confirming our hypothesis. However, many of the values... (More)
Planktonic community respiration is an important carbon cycling process, typically quantified by converting measured values of dissolved oxygen consumption rates into carbondioxide production rates using a respiratory quotient of 1 (RQ = carbondioxide per oxygen by moles). However, the true variability in planktonic RQs between different aquatic ecosystems is poorly understood. We conducted in situ RQ measurements in a eutrophic lake (Sweden) to test the hypothesis that the RQ is systematically below 1 when the organic matter pool is dominated by reduced algal-derived substrates that theoretically require large amounts of oxygen to mineralize. The RQ was significantly lower than 1, confirming our hypothesis. However, many of the values were extremely low (0.2 – 0.6), below theoretical RQs for oxidation of algal organic matter substrates (0.7 - 0.8), suggesting that other factors than substrate control need to be considered to understand the RQ. Lack of substrate control of the RQ was further evidenced through analyses of the functional capacity of the bacterioplankton community to degrade standard compounds on the Biolog Ecoplate. Based on the measured dynamics in methane and nutrient pools, methane oxidation and nitrification likely occurred in the lake, contributing to the unusually low RQs. Our findings demonstrate that planktonic RQs in productive lakes can systematically be < 1, suggesting that the respiration in these lakes may currently be overestimated. (Less)
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1 pages
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ASLO Summer Meeting 2018
language
English
LU publication?
yes
id
7822a567-46e8-424e-be01-3e839c6811dd
date added to LUP
2018-07-05 16:27:48
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2018-07-13 12:09:40
@misc{7822a567-46e8-424e-be01-3e839c6811dd,
  abstract     = {Planktonic community respiration is an important carbon cycling process, typically quantified by converting measured values of dissolved oxygen consumption rates into carbondioxide production rates using a respiratory quotient of 1 (RQ = carbondioxide per oxygen by moles). However, the true variability in planktonic RQs between different aquatic ecosystems is poorly understood. We conducted in situ RQ measurements in a eutrophic lake (Sweden) to test the hypothesis that the RQ is systematically below 1 when the organic matter pool is dominated by reduced algal-derived substrates that theoretically require large amounts of oxygen to mineralize. The RQ was significantly lower than 1, confirming our hypothesis. However, many of the values were extremely low (0.2 – 0.6), below theoretical RQs for oxidation of algal organic matter substrates (0.7 - 0.8), suggesting that other factors than substrate control need to be considered to understand the RQ. Lack of substrate control of the RQ was further evidenced through analyses of the functional capacity of the bacterioplankton community to degrade standard compounds on the Biolog Ecoplate. Based on the measured dynamics in methane and nutrient pools, methane oxidation and nitrification likely occurred in the lake, contributing to the unusually low RQs. Our findings demonstrate that planktonic RQs in productive lakes can systematically be &lt; 1, suggesting that the respiration in these lakes may currently be overestimated.},
  author       = {Münzner, Karla and Berggren, Martin},
  language     = {eng},
  pages        = {1},
  title        = {In situ plankton community respiration measurements show low respiratory quotients in a eutrophic lake},
  year         = {2018},
}