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

Allesson, Lina; Ström, Lena; Berggren, Martin

doi:10.1002/2016gl069621

Cited by 24 publications

(22 citation statements)

References 36 publications

(59 reference statements)

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“…Bacterioplankton respiration is a key process for converting organic carbon to CO 2 in aquatic ecosystems (Williams and Del Giorgio, 2005). This mineralization of DOC driven by microbial respiration is accompanied by O 2 consumption, often with an assumed RQ of 1, yet this quotient depends on substrate properties and metabolic states (Dilly, 2003;Berggren et al, 2012;Allesson et al, 2016). Similar to the CO 2 production rates in experimental set-up 1 and the higher O 2 consumption rates in P-spiked samples in experimental set-up 2 could represent a situation with higher BGE than in P-limited samples.…”

Section: Experimental Validation Of Driversmentioning

confidence: 99%

Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production

et al. 2020

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The current trend of increasing input of terrestrially derived dissolved organic carbon (DOC) to boreal freshwater systems is causing increased levels of carbon dioxide (CO 2) supersaturation and degassing. Phosphorus (P) is often the most limiting nutrient for bacterial growth and would thus be expected to increase overall mineralization rates and CO 2 production. However, high carbon (C) to P ratios of terrestrially derived DOC could also cause elevated cell-specific respiration of the excess C in heterotrophic bacteria. Using data from a survey of 75 Scandinavian lakes along an ecosystem gradient of DOC, we estimated in situ CO 2 production rates. These rates showed a unimodal response with DOC-specific CO 2 production negatively related to DOC:total phosphorus (TP) ratio, and a turning point at 5 mg C L −1 , indicating higher DOC turnover rates in productive than in unproductive lakes. To further assess the dependency of bacterial respiration (BR) on DOC and P, we monitored CO 2 production in incubations of water with a gradient of DOC crossed with two levels of inorganic P. Finally, we crossed DOC and P with a temperature gradient to test the temperature dependency of respiration rates [as oxygen (O 2) consumption]. While total CO 2 production seemed to be unaffected by P additions, respiration rates, and growth yields, as estimated by ribosomal gene copy numbers, suggest increased bacterial growth and decreased cell-specific respiration under non-limited P conditions. Respiration rates showed a sigmoid response to increasing DOC availability reaching a plateau at about 20 mg C L −1 of initial DOC concentrations. In addition to these P and DOC level effects, respiration rates responded in a non-monotonic fashion to temperature with an increase in respiration rates by a factor of 2.6 (±0.2) from 15 to 25°C and a decrease above 30°C. The combined results from the survey and experiments highlight DOC as the major determinant of CO 2 production in boreal lakes, with P and temperature as significant modulators of respiration kinetics.

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Section: Experimental Validation Of Driversmentioning

confidence: 99%

Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production

et al. 2020

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“…A weakness with this approach is the uncertainty related to the RQ value used for unit conversion to carbon. Studies in unproductive lakes in different boreal regions have reported average bacterioplankton RQs of 1.2 (Berggren et al ) or ~ 2 (Cimbleris and Kalff ), and RQs as high as ~ 3 have been experimentally achieved by feeding bacteria with UV light treated partially oxidized DOC (Allesson et al ). Considering that partial UV oxidation followed by microbial decay could be a major pathway of organic carbon decay in tundra region freshwaters (Cory et al ), it is possible that the RQ and thus also the DOC decay rates in this study were underestimated.…”

Section: Discussionmentioning

confidence: 99%

Systematic microbial production of optically active dissolved organic matter in subarctic lake water

Berggren

Gudasz

Guillemette

et al. 2019

Limnology & Oceanography

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The ecology and biogeochemistry of lakes in the subarctic region are particularly sensitive to changes in the abundance and optical properties of dissolved organic matter (DOM). External input of colored DOM to these lakes is an extensively researched topic, but little is known about potential reciprocal feedbacks between the optical properties of DOM and internal microbial processes in the water. We performed 28-day dark laboratory incubation trials on water from 101 subarctic tundra lakes in northern Sweden, measuring the microbial decay of DOM and the resulting dynamics in colored (CDOM) and fluorescent (FDOM) DOM components. While losses in dissolved oxygen during the incubations corresponded to a 20% decrease in mean DOM, conversely the mean CDOM and total FDOM increased by 22% and 30%, respectively. However, the patterns in microbial transformation of the DOM were not the same in all lakes. Notably, along the gradient of increasing ambient CDOM (water brownness), the lakes showed decreased microbial production of protein-like fluorescence, lowered DOM turnover rates and decreasing bacterial growth per unit of DOM. These trends indicate that browning of subarctic lakes systematically change the way that bacteria interact with the ambient DOM pool. Our study underscores that there is no unidirectional causal link between microbial processes and DOM optical properties, but rather reciprocal dependence between the two.

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“…A systematic field study of the RQs of freshwater bacterioplankton showed large variability (1.2 ±0.45) with a significant negative correlation between RQ and in situ O 2 concentration and pH and a significant positive correlation between RQ and in situ pCO 2 (Berggren et al, 2011). Bacterioplankton RQs were low (average 0.81) in net autotrophic freshwater systems where reduced substrates derived from phytoplankton excretion are likely to dominate and higher (average 1.35) in net heterotrophic freshwater systems where oxidized substrates such as organic acids formed by photochemical processes could occur (Allesson et al, 2016). However, due to the low rates of oxygen consumption and CO 2 production by marine plankton, and the precision of methods to measure changes in dissolved inorganic carbon (DIC; ∼1-2 mmol m −3 ), there has not been a systematic field study of the magnitude and variability of marine plankton RQs.…”

Section: Respiratory Quotientsmentioning

confidence: 93%

Microbial Respiration, the Engine of Ocean Deoxygenation

Robinson

2019

Front. Mar. Sci.

103

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

Cited by 24 publications

References 36 publications

Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production

Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production

Systematic microbial production of optically active dissolved organic matter in subarctic lake water

Microbial Respiration, the Engine of Ocean Deoxygenation

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