Respiration quotient variability: bacterial evidence

Romero-Kutzner, Vanesa; Packard, Theodore T.; Berdalet, Elisa; Roy, Sylvie; Gagné, Jean‐Pierre

doi:10.3354/meps11062

Cited by 22 publications

(17 citation statements)

References 51 publications

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“…Quantifying the variability in RQ allows not only the production of CO 2 to be calculated from dissolved oxygen consumption, but also reveals shifts in plankton physiology that are not evident from any other measurement. Culture studies with marine bacteria (Vibrio natriegens and Pseudomonas nautica) show that the respiratory quotient varies with physiological state, metabolic pathway and carbon source (acetate or pyruvate) (Berdalet et al, 1995;Roy et al, 1999;Romero-Kutzner et al, 2015).…”

Section: Respiratory Quotientsmentioning

confidence: 99%

Microbial Respiration, the Engine of Ocean Deoxygenation

Robinson

2019

Front. Mar. Sci.

109

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Microbial plankton respiration is the key determinant in the balance between the storage of organic carbon in the oceans or its conversion to carbon dioxide with accompanying consumption of dissolved oxygen. Over the past 50 years, dissolved oxygen concentrations have decreased in many parts of the world's oceans, and this trend of ocean deoxygenation is predicted to continue. Yet despite its pivotal role in ocean deoxygenation, microbial respiration remains one of the least constrained microbial metabolic processes. Improved understanding of the magnitude and variability of respiration, including attribution to component plankton groups, and quantification of the respiratory quotient, would enable better predictions, and projections of the intensity and extent of ocean deoxygenation and of the integrative impact of ocean deoxygenation, ocean acidification, warming, and changes in nutrient concentration and stoichiometry on marine carbon storage. This study will synthesize current knowledge of respiration in relation to deoxygenation, including the drivers of its variability, identify key unknowns in our ability to project future scenarios and suggest an approach to move the field forward.

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Section: Respiratory Quotientsmentioning

confidence: 99%

Microbial Respiration, the Engine of Ocean Deoxygenation

Robinson

2019

Front. Mar. Sci.

109

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“…For example, the RQ was set to 1, which is a good estimate for carbohydrate oxidation. For lipids and proteins the RQ is close to 0.7, but in a natural environment RQ is often > 1 (Berggren et al, 2012) and is affected by physiological state, e.g., nutrient limitation (Romero-Kutzner et al, 2015). Any temporal variability in the conversion factors would directly change the overall budget calculations, e.g., RQ affecting total respiration and gross primary production estimates.…”

Section: Budgetmentioning

confidence: 99%

Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

et al. 2016

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Abstract. About a quarter of anthropogenic CO 2 emissions are currently taken up by the oceans, decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO 2 levels on pelagic carbon fluxes. A gradient of different CO 2 scenarios, ranging from ambient (∼ 370 µatm) to high (∼ 1200 µatm), were set up in mesocosm bags (∼ 55 m 3 ). We determined standing stocks and temporal changes of total particulate carbon (TPC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) of specific plankton groups. We also measured carbon flux via CO 2 exchange with the atmosphere and sedimentation (export), and biological rate measurements of primary production, bacterial production, and total respiration. The experiment lasted for 44 days and was divided into three different phases (I: t0-t16; II: t17-t30; III: t31-t43). Pools of TPC, DOC, and DIC were approximately 420, 7200, and 25 200 mmol C m −2 at the start of the experiment, and the initial CO 2 additions increased the DIC pool by ∼ 7 % in the highest CO 2 treatment. Overall, there was a decrease in TPC and increase of DOC over the course of the experiment. The decrease in TPC was lower, and increase in DOC higher, in treatments with added CO 2 . During phase I the estimated gross primary production (GPP) was ∼ 100 mmol C m −2 day −1 , from which 75-95 % was respired, ∼ 1 % ended up in the TPC (including export), and 5-25 % was added to the DOC pool. During phase II, the respiration loss increased to ∼ 100 % of GPP at the ambient CO 2 concentration, whereas respiration was lower (85-95 % of GPP) in the highest CO 2 treatment. Bacterial production was ∼ 30 % lower, on average, at the highest CO 2 concentration than in the controls during phases II and III. This resulted in a higher accumulation of DOC and lower reduction in the TPC pool in the elevated CO 2 treatments at the end of phase II extending throughout phase III. The "extra" organic carbon at high CO 2 remained fixed in an increasing biomass of small-sized plankton and in the DOC pool, and did not transfer into large, sinking aggregates. Our rePublished by Copernicus Publications on behalf of the European Geosciences Union. sults revealed a clear effect of increasing CO 2 on the carbon budget and mineralization, in particular under nutrient limited conditions. Lower carbon loss processes (respiration and bacterial remineralization) at elevated CO 2 levels resulted in higher TPC and DOC pools than ambient CO 2 concentration. These results highlight the importance of addressing not only net changes in carbon standing stocks but also carbon fluxes and budgets to better disentangle the effects of ocean acidification.

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“…However, in this study bacterial production was not measured and it can only be speculated that enhanced biomass production might have partly contributed to the high RQ values observed in UV treated compared to dark samples. Nonetheless, considering the vastly elevated RQs that we observed, a shift in substrate pool due to partial photooxidation is more likely to have had an overriding impact on the bacterial RQ than physiological processes that tend to have only marginal effects [ Romero‐Kutzner et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…For example, the RQ is affected by biochemical pathways of metabolism, where anabolic processes (cell growth) contribute to higher RQs than catabolic respiration alone [ Berggren et al ., ; Dilly , ]. More importantly, RQ is strongly dependent on the composition of the assimilated organic substrate [ Berggren et al ., ; Romero‐Kutzner et al ., ], especially the O and H content [ Dilly , ]. Assimilation of organic substrates with large O content and high O:H ratio requires less O 2 from the surroundings, and hence, respiration is performed at a relatively high RQ.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the RQ is affected by biochemical pathways of metabolism, where anabolic processes (cell growth) contribute to higher RQs than catabolic respiration alone Dilly, 2003]. More importantly, RQ is strongly dependent on the composition of the assimilated organic substrate Romero-Kutzner et al, 2015], especially the O and H content [Dilly, 2001] ]. Several of the most common LMW compounds that are released from reactions between DOC and ultraviolet (UV) sunlight are theoretically oxidized at RQs between 1.3 and 4 (see examples in Table 1).…”

Section: Introductionmentioning

confidence: 99%

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Impact of photochemical processing of DOC on the bacterioplankton respiratory quotient in aquatic ecosystems

Allesson

Ström

Berggren

2016

Geophysical Research Letters

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Many studies assume a respiratory quotient (RQ = molar ratio of CO2 produced to O2 consumed) close to 1 when calculating bacterioplankton respiration. However, evidence suggests that RQ depends on the chemical composition of the respired substrate pool that may be altered by photochemical production of oxygen‐rich substrates, resulting in elevated RQs. Here we conducted a novel study of the impact of photochemical processing of dissolved organic carbon (DOC) on RQ. We monitored the bacterial RQ in bioassays of both ultraviolet light irradiated and nonirradiated humic lake water, using optic gas‐pressure sensors. In the experimentally irradiated samples the average RQ value was significantly higher (3.4–3.5 [±0.4 standard error (SE)]) than that in the dark controls (1.3 [±0.1 SE]). Our results show that the RQ is systematically higher than 1 when the bacterial metabolism in large part is based on photoproducts. By assuming an RQ of 1, bacterioplankton respiration in freshwater ecosystems may be greatly underestimated.

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Respiration quotient variability: bacterial evidence

Cited by 22 publications

References 51 publications

Microbial Respiration, the Engine of Ocean Deoxygenation

Microbial Respiration, the Engine of Ocean Deoxygenation

Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

Impact of photochemical processing of DOC on the bacterioplankton respiratory quotient in aquatic ecosystems

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