Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

Jiao, Nianzhi; Legendre, Louis; Robinson, Carol; Thomas, Helmuth; Luo, Yawei; Dang, Hongyue; Liu, Jihua; Zhang, Rui; Tang, Kai; Luo, Tingwei; Li, Chao; Wang, Xiaoxue; Zhang, Chuanlun

doi:10.1126/science.aab2713

Cited by 37 publications

(38 citation statements)

References 8 publications

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“…For our fit, the lower limit for [DOC] min is 0 mmol m −3 , and the upper limit falls between 76 and 77 mmol m −3 giving errors of approximately ±38.0 mmol m −3 . In addition, as suggested by Jiao et al [2015], the total concentrations of DOC in the experiment may reflect a mixture of recalcitrant DOC and bioavailable DOC that already existed in the control; e.g., bioavailable DOC may have made up 6% of the total DOC. As a consequence, the estimated dilution threshold derived on the basis of the Monod fit to total [DOC] concentrations may be overestimated.…”

Section: Removal Processes 231 Heterotrophic Degradation Of Doc Abmentioning

confidence: 88%

“…As a consequence, the estimated dilution threshold derived on the basis of the Monod fit to total [DOC] concentrations may be overestimated. To explicitly explore the effect of uncertainty in the dilution threshold, we add a scaling term ( x , unitless) into equation that reflects the linear change in parameters when fitting equation assuming that bacterial growth is supported by a smaller proportion of bioavailable DOC [ Jiao et al , ] (see Text S1 for a full derivation). This provides a way of scaling equation for use with different dilution thresholds that is consistent with alternative interpretations of the data:

R_{uptake} = ({, \begin{matrix} V_{\max} \cdot \frac{[DOC]}{Kx + DOC} - b, & if [DOC] \geq {[DOC]}_{\min}^{new} \\ 0, & otherwise \end{matrix})

where

x = \frac{{[DOC]}_{\min}^{new}}{{[DOC]}_{\min}}

.…”

Section: Methodsmentioning

confidence: 99%

“…We explore the simulated steady state deep ocean DOC concentration and its Δ 14 C signature for three sets of experiments: Testing the plausibility of the dilution hypothesis according to Arrieta et al []: We first use the model to explore a hypothetical scenario where DOC that is available for uptake by prokaryotes in the deep ocean is limited by dilution only; i.e., the first‐order reaction rate term in the model ( k ) is set to 0. The dilution threshold is constrained on the basis of experimental results (

{DOC}_{\min} = 38.6 \pm 38.0 mmol m^{- 3}

) to explicitly test whether the hypothesis of Arrieta et al [] is consistent with observations of Δ 14 C in the deep ocean. Testing the robustness of model results : The dilution threshold found by Arrieta et al [] is an average of values ranging from 10 to 57 mmol m −3 that may reflect some unknown variability in the data [ Jiao et al , ] or equal uncertainty in the fitting of the Monod function as demonstrated in Figure . Therefore, we test the robustness of the model results for a range of different dilution thresholds (

{[DOC]}_{\min} = 10 to 42 mmol m^{- 3}

). Testing the sensitivity of the model to the assumption that dilution is the key removal process : Lastly, we explore a scenario where dilution‐limited DOC is removed from the deep ocean with ocean overturning.…”

Section: Methodsmentioning

confidence: 99%

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Modeling radiocarbon constraints on the dilution of dissolved organic carbon in the deep ocean

Wilson

Arndt

2017

Global Biogeochemical Cycles

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract The recalcitrance of dissolved organic carbon (DOC) that leads to its accumulation in the deep ocean is typically considered a function of its reactivity. Yet, recent experimental evidence has shown that DOC from the deep ocean, if concentrated, can support significant microbial growth. This supports an alternative hypothesis that [DOC] may become too dilute to support microbial growth. The radiocarbon signature of DOC is a key constraint on the DOC cycling that allows testing of the plausibility of this hypothesis. Here we use a box model of diluted DOC in the deep ocean and its radiocarbon signature that is constrained on the basis of the new experimental evidence, as well as current knowledge of deep ocean DOC cycling to quantitatively test the dilution hypothesis. We explore the uncertainty in model results across a range of plausible dilution thresholds, additional processes, and fluxes of DOC to the deep ocean. Global Biogeochemical CyclesResults show that the model is able to predict the observed radiocarbon signature for a dilution threshold close to the observed deep ocean [DOC] and for fluxes close to published estimates. Sensitivity analysis shows that this result is highly sensitive to variations in the dilution threshold and the assumption that diluted DOC is able to survive ocean overturning. The experimental findings can be alternatively reconciled over a large range of different conditions assuming a small pool of diluted DOC with a modern radiocarbon signature, consistent with recent observations, and offering a parsimonious interpretation of dilution with existing hypotheses on DOC recalcitrance.

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Section: Removal Processes 231 Heterotrophic Degradation Of Doc Abmentioning

confidence: 88%

R_{uptake} = ({, \begin{matrix} V_{\max} \cdot \frac{[DOC]}{Kx + DOC} - b, & if [DOC] \geq {[DOC]}_{\min}^{new} \\ 0, & otherwise \end{matrix})

where

x = \frac{{[DOC]}_{\min}^{new}}{{[DOC]}_{\min}}

.…”

Section: Methodsmentioning

confidence: 99%

{DOC}_{\min} = 38.6 \pm 38.0 mmol m^{- 3}

{[DOC]}_{\min} = 10 to 42 mmol m^{- 3}

Section: Methodsmentioning

confidence: 99%

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Modeling radiocarbon constraints on the dilution of dissolved organic carbon in the deep ocean

Wilson

Arndt

2017

Global Biogeochemical Cycles

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“…Arrieta and coworkers have stated that the 'dilution hypothesis is the primary mechanism controlling on the biogeochemical cycling of DOC in the deep ocean' (Arrieta et al, 2015a). It has been pointed out that there is no significant increase in DOC consumption (< 6%) when increasing DOC concentrations (Jiao et al, 2015). Arrieta and coworkers explained that it would take a longer time for complete consumption of labile substrates and illustrated this process by a simulation study that assumed that DOC utilization depends only on concentration.…”

Section: Explanations Of Low Doc Consumption In Concentrated Experimentsmentioning

confidence: 99%

“…This reservoir plays a critical role in global carbon sequestration and potentially affects global climate (Hansell et al, 2009;Jiao et al, 2014). Although we know that RDOC persists in the water column for thousands of years (Brophy and Carlson, 1989;Lancelot et al, 1993;Carlson and Ducklow, 1995;Jiao et al, 2010;Hansell, 2013), the mechanisms underpinning this extraordinary stability remain objects of controversy (Arrieta et al, 2015b,b;Jiao et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Contribution of structural recalcitrance to the formation of the deep oceanic dissolved organic carbon reservoir

Wang

Luo

Polimene

et al. 2018

Environ Microbiol Rep

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Summary The origin of the recalcitrant dissolved organic carbon (RDOC) reservoir in the deep ocean remains enigmatic. The structural recalcitrance hypothesis suggests that RDOC is formed by molecules that are chemically resistant to bacterial degradation. The dilution hypothesis claims that RDOC is formed from a large diversity of labile molecules that escape bacterial utilization due to their low concentrations, termed as RDOCc. To evaluate the relative contributions of these two mechanisms in determining the long‐term persistence of RDOC, we model the dynamics of both structurally recalcitrant DOC and RDOCc based on previously published data that describes deep oceanic DOC degradation experiments. Our results demonstrate that the majority of DOC (84.5 ± 2.2%) in the deep ocean is structurally recalcitrant. The intrinsically labile DOC (i.e., labile DOC that rapidly consumed and RDOCc) accounts for a relatively small proportion and is consumed rapidly in the incubation experiments, in which 47.8 ± 3.2% of labile DOC and 21.9 ± 4.6% of RDOCc are consumed in 40 days. Our results suggest that the recalcitrance of RDOC is largely related to its chemical properties, whereas dilution plays a minor role in determining the persistence of deep‐ocean DOC.

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Polycomb Repressive Complex 2: Modulator Development for Functional Regulation of a Multiprotein Complex by Using Structural Information

Tokodai

Yakushiji

2019

ChemBioChem

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Functional regulation of a protein complex is generally difficult because information of the target complex as a whole is limited. However, regulation of a protein complex is important for understanding complicated biological events in cells and therapeutic possibilities. This concept article introduces the potential for the functional regulation of a multiprotein complex, polycomb repressive complex 2 (PRC2), by developing chemical modulators. Functional regulatory mechanisms of PRC2 are described by using protein interaction information found through structural analyses. Subsequently, possibilities of novel chemical modulator development of PRC2 based on structural insights into the complex and related interactions are discussed.

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Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

Cited by 37 publications

References 8 publications

Modeling radiocarbon constraints on the dilution of dissolved organic carbon in the deep ocean

Modeling radiocarbon constraints on the dilution of dissolved organic carbon in the deep ocean

Contribution of structural recalcitrance to the formation of the deep oceanic dissolved organic carbon reservoir

Polycomb Repressive Complex 2: Modulator Development for Functional Regulation of a Multiprotein Complex by Using Structural Information

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