Terrestrial browning from Colored Dissolved Organic Matter (CDOM) changes the seasonal phenology of the coastal Arctic carbon cycle

Bertin, Clement; Le Fouest, Vincent; Carroll, Dustin; Dutkiewicz, Stephanie; Menemenlis, Dimitris; Matsuoka, Atsushi; Manizza, Manfredi; Miller, Charles E.

doi:10.5194/egusphere-2025-973

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https://doi.org/10.5194/egusphere-2025-973

Preprints

13 Mar 2025

| 13 Mar 2025

Terrestrial browning from Colored Dissolved Organic Matter (CDOM) changes the seasonal phenology of the coastal Arctic carbon cycle

Clement Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

Abstract. Arctic warming affects land-to-ocean fluxes of organic matter, with significant impacts on coastal ecosystems and air-sea CO₂ fluxes. In this study, we modify a regional ECCO-Darwin ocean biogeochemistry simulation of the Mackenzie River region to include riverine export of colored dissolved organic matter (CDOM) and its effect on light attenuation, marine carbon cycling, and water-column heating from UV-A to visible light absorption. We find that CDOM light attenuation triggers both a two-week delay in the seasonal phytoplankton bloom and an increase in sea-surface temperature (SST) by 1.7 °C. While the change in phytoplankton phenology has limited effect on air-sea CO₂ fluxes, the local increase in SST due to terrestrial browning switches the coastal zone from an annual sink of atmospheric CO₂ to a source (7.35 Gg C yr^-1). Our work suggests that the projected increase in terrestrial CDOM has strong implications for phytoplankton phenology and coastal air-sea carbon exchange in the Arctic.

Received: 28 Feb 2025 – Discussion started: 13 Mar 2025

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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Journal article(s) based on this preprint

07 Nov 2025

Colored dissolved organic matter (CDOM) alters the seasonal physics and biogeochemistry of the Arctic Mackenzie River plume

Clément Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

Biogeosciences, 22, 6607–6629, https://doi.org/10.5194/bg-22-6607-2025,https://doi.org/10.5194/bg-22-6607-2025, 2025

Short summary

Clement Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-973', Anonymous Referee #1, 24 Apr 2025
General comments:

The manuscript entitled "Terrestrial browning from colored dissolved organic matter (CDOM) changes the seasonal phenology of the coastal Arctic carbon cycle" explores the influence of CDOM on both biogeochemical and physical processes in the Mackenzie River region. The subject is both relevant and timely, addressing key concerns about the role of land-ocean interactions in a rapidly changing Arctic environment. The study provides promising insights that could significantly advance our understanding of how CDOM modulates seasonal carbon fluxes and ecosystem functioning in coastal regions.

However, a few issues require clarification and refinement before the manuscript can be considered for publication.
Major comments:
1. Clarification needed on the consistency of the validation datasets and years used

The authors state that they focus their analysis on the year 2012, and most of the figures throughout the manuscript appear to reflect results from that year. However, it remains unclear whether the model-data comparisons presented are also based solely on 2012 data. For instance, in Appendix B (Figure B1), the terrestrial CDOM ratio is compared to observations from 2009. The manuscript would benefit from a clear statement on whether these validation figures are meant to support the 2012 model run specifically, or whether they are included to assess model performance more generally.
In addition, a major part of the validation appears to rely on the study by Lewis and Arrigo (2020), yet the exact years used in that comparison are not clearly stated in the present manuscript. Upon reviewing Lewis and Arrigo (2020), it is also not obvious which datasets were used by the authors of the current manuscript to reproduce the validation figures, particularly Figure D1.
Greater clarity is needed on:
which years of observational data were used in each validation figure,

whether these years correspond to the 2012 simulation,

and which specific datasets were extracted from Lewis and Arrigo (2020) or other sources.

2. Terminology in the manuscript may overstate the scope of the analysis

In a few places, the manuscript uses terminology that suggests a broader ecosystem analysis than is actually conducted. For example, in the introduction, the authors state that they explore the effect of CDOM on the “seasonal cycle of plankton biomass, productivity, and carbon cycling,” which implies a study of both autotrophic and heterotrophic plankton communities. Similarly, in Section 3.4, the title “CDOM effect on marine productivity” gives the impression that both primary and secondary production are addressed, whereas the analysis focuses solely on phytoplankton primary production.
Another example appears in the sentence: “We explore the specific effects of CDOM light attenuation and ocean heating on the coastal ecosystems and the carbon cycle.” Again, the wording implies a broader analysis than what is presented in the paper.
To improve clarity and avoid overstatement, I recommend that the authors revise general terms such as plankton productivity, ecosystem dynamics, and carbon cycle to more specific phrases such as phytoplankton production, chlorophyll concentration, or primary production. This is especially important given the study’s focus on a single trophic level (phytoplankton only), while terms such as “ecosystem” may imply a broader biological or biogeochemical system.
3. Potential confounding effects due to differing nutrient concentrations in simulations

In Figure 7a, it appears that the initial nutrient concentrations are higher in the CDOM ON simulation than in the control simulation (CDOM OFF). However, the manuscript does not mention any differences in nutrient forcing or initial conditions between the two simulations.

Given that nutrient availability is a key limiting factor for phytoplankton growth, such differences could strongly influence the interpretation of CDOM-related effects.
If nutrient fields or boundary fluxes differ between the simulations, the observed variations in phytoplankton biomass and productivity may not be attributable solely to the effects of CDOM on light attenuation or temperature. I recommend that the authors clarify whether nutrient initial conditions and boundary forcings were kept identical between simulations. If they differ, a justification should be provided, and the interpretation of the results should be revisited accordingly.
4. Clarification needed on bloom timing and comparison to observations

In the discussion (line 370), the authors state that the model "successfully simulates the timing of the bloom peak compared to Lewis et al. (2020),” while also noting that improvements to the sea ice model are needed to simulate bloom initiation more accurately. However, it is not clearly stated which simulation is being referenced (CDOM ON or CDOM OFF).
Based on the figures comparing model results to observations (e.g., Figure D1), it appears that the CDOM OFF simulation initiates the bloom closer to the observed timing, while the CDOM ON simulation results in a delayed bloom. This seems to contradict the statement that the model accurately reproduces bloom timing — unless the authors are referring specifically to the amplitude of the bloom rather than its onset.
I recommend that the authors clarify:
which simulation is being evaluated when claiming agreement with observations,

whether CDOM improves or delays bloom timing relative to the data,

and how this affects the interpretation of CDOM's role in modulating bloom phenology.

A more nuanced discussion would be helpful here, especially if CDOM appears to delay the bloom in a way that is less consistent with observed phenology.
5. Apparent inconsistency between NPP and chlorophyll concentrations

In line 365, the authors state that the simulated phytoplankton amplitude is 85% higher in the CDOM ON simulation, which is consistent with the values shown in Figure 7a (NPP ≈ 4.6 Gg C d⁻¹ without CDOM vs. ≈ 8.1 Gg C d⁻¹ with CDOM). However, in Figure D1 — which compares surface chlorophyll concentrations from both simulations to observations — the amplitude of the two simulations appears quite similar.
Since chlorophyll is commonly used as a proxy for phytoplankton biomass, one would expect a notable difference in amplitude if NPP nearly doubles. The manuscript does not provide an explanation for this apparent discrepancy. Could the authors clarify whether this discrepancy reflects a decoupling between biomass and productivity in the model (e.g., due to C:Chl ratio dynamics or other processes such as loss terms or export)? Additional clarification would help interpret how CDOM influences not only the rate of primary production but also the standing stock and its comparison to observations.
Conclusion:

Overall, the manuscript addresses an important and timely topic with a solid modeling approach. With the clarifications and revisions suggested above, the study will present a clearer and more robust contribution to our understanding of CDOM effects in Arctic coastal systems.
Citation: https://doi.org/10.5194/egusphere-2025-973-RC1
- AC1: 'Reply on RC1', Clement Bertin, 21 Jun 2025
  
  Dear reviewer,
  Please find attached the pdf file with the answers to your comments.
  Best regards,
  The authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-973-AC1
RC2:
'Comment on egusphere-2025-973', Anonymous Referee #2, 31 May 2025

Please find my review of the paper in the attachment.

Citation: https://doi.org/10.5194/egusphere-2025-973-RC2
- AC2:
  'Reply on RC2', Clement Bertin, 21 Jun 2025
  
  Dear reviewer,
  Please find attached the pdf file with the answers to your comments.
  Best regards,
  The authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-973-AC2
  - AC3: 'Reply on AC2', Clement Bertin, 23 Jun 2025
    
    We noticed that we omitted to answer one comment from the review.
    
    Below is the specific answer to this comment:
    According to reviewer comment, we changed the first sentence of the abstract (L1-2) as follows: “Arctic warming affects land-to-ocean fluxes of organic matter through increased permafrost thaw, coastal erosion or river discharge, with significant impacts on coastal ecosystems and air-sea CO₂fluxes” and changed the term terrestrial browning by: “terrestrial organic matter input” (L7).
    Apologies for the missing answer.
    
    The authors
    
    Citation: https://doi.org/10.5194/egusphere-2025-973-AC3

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-973', Anonymous Referee #1, 24 Apr 2025
General comments:

The manuscript entitled "Terrestrial browning from colored dissolved organic matter (CDOM) changes the seasonal phenology of the coastal Arctic carbon cycle" explores the influence of CDOM on both biogeochemical and physical processes in the Mackenzie River region. The subject is both relevant and timely, addressing key concerns about the role of land-ocean interactions in a rapidly changing Arctic environment. The study provides promising insights that could significantly advance our understanding of how CDOM modulates seasonal carbon fluxes and ecosystem functioning in coastal regions.

However, a few issues require clarification and refinement before the manuscript can be considered for publication.
Major comments:
1. Clarification needed on the consistency of the validation datasets and years used

The authors state that they focus their analysis on the year 2012, and most of the figures throughout the manuscript appear to reflect results from that year. However, it remains unclear whether the model-data comparisons presented are also based solely on 2012 data. For instance, in Appendix B (Figure B1), the terrestrial CDOM ratio is compared to observations from 2009. The manuscript would benefit from a clear statement on whether these validation figures are meant to support the 2012 model run specifically, or whether they are included to assess model performance more generally.
In addition, a major part of the validation appears to rely on the study by Lewis and Arrigo (2020), yet the exact years used in that comparison are not clearly stated in the present manuscript. Upon reviewing Lewis and Arrigo (2020), it is also not obvious which datasets were used by the authors of the current manuscript to reproduce the validation figures, particularly Figure D1.
Greater clarity is needed on:
which years of observational data were used in each validation figure,

whether these years correspond to the 2012 simulation,

and which specific datasets were extracted from Lewis and Arrigo (2020) or other sources.

2. Terminology in the manuscript may overstate the scope of the analysis

In a few places, the manuscript uses terminology that suggests a broader ecosystem analysis than is actually conducted. For example, in the introduction, the authors state that they explore the effect of CDOM on the “seasonal cycle of plankton biomass, productivity, and carbon cycling,” which implies a study of both autotrophic and heterotrophic plankton communities. Similarly, in Section 3.4, the title “CDOM effect on marine productivity” gives the impression that both primary and secondary production are addressed, whereas the analysis focuses solely on phytoplankton primary production.
Another example appears in the sentence: “We explore the specific effects of CDOM light attenuation and ocean heating on the coastal ecosystems and the carbon cycle.” Again, the wording implies a broader analysis than what is presented in the paper.
To improve clarity and avoid overstatement, I recommend that the authors revise general terms such as plankton productivity, ecosystem dynamics, and carbon cycle to more specific phrases such as phytoplankton production, chlorophyll concentration, or primary production. This is especially important given the study’s focus on a single trophic level (phytoplankton only), while terms such as “ecosystem” may imply a broader biological or biogeochemical system.
3. Potential confounding effects due to differing nutrient concentrations in simulations

In Figure 7a, it appears that the initial nutrient concentrations are higher in the CDOM ON simulation than in the control simulation (CDOM OFF). However, the manuscript does not mention any differences in nutrient forcing or initial conditions between the two simulations.

Given that nutrient availability is a key limiting factor for phytoplankton growth, such differences could strongly influence the interpretation of CDOM-related effects.
If nutrient fields or boundary fluxes differ between the simulations, the observed variations in phytoplankton biomass and productivity may not be attributable solely to the effects of CDOM on light attenuation or temperature. I recommend that the authors clarify whether nutrient initial conditions and boundary forcings were kept identical between simulations. If they differ, a justification should be provided, and the interpretation of the results should be revisited accordingly.
4. Clarification needed on bloom timing and comparison to observations

In the discussion (line 370), the authors state that the model "successfully simulates the timing of the bloom peak compared to Lewis et al. (2020),” while also noting that improvements to the sea ice model are needed to simulate bloom initiation more accurately. However, it is not clearly stated which simulation is being referenced (CDOM ON or CDOM OFF).
Based on the figures comparing model results to observations (e.g., Figure D1), it appears that the CDOM OFF simulation initiates the bloom closer to the observed timing, while the CDOM ON simulation results in a delayed bloom. This seems to contradict the statement that the model accurately reproduces bloom timing — unless the authors are referring specifically to the amplitude of the bloom rather than its onset.
I recommend that the authors clarify:
which simulation is being evaluated when claiming agreement with observations,

whether CDOM improves or delays bloom timing relative to the data,

and how this affects the interpretation of CDOM's role in modulating bloom phenology.

A more nuanced discussion would be helpful here, especially if CDOM appears to delay the bloom in a way that is less consistent with observed phenology.
5. Apparent inconsistency between NPP and chlorophyll concentrations

In line 365, the authors state that the simulated phytoplankton amplitude is 85% higher in the CDOM ON simulation, which is consistent with the values shown in Figure 7a (NPP ≈ 4.6 Gg C d⁻¹ without CDOM vs. ≈ 8.1 Gg C d⁻¹ with CDOM). However, in Figure D1 — which compares surface chlorophyll concentrations from both simulations to observations — the amplitude of the two simulations appears quite similar.
Since chlorophyll is commonly used as a proxy for phytoplankton biomass, one would expect a notable difference in amplitude if NPP nearly doubles. The manuscript does not provide an explanation for this apparent discrepancy. Could the authors clarify whether this discrepancy reflects a decoupling between biomass and productivity in the model (e.g., due to C:Chl ratio dynamics or other processes such as loss terms or export)? Additional clarification would help interpret how CDOM influences not only the rate of primary production but also the standing stock and its comparison to observations.
Conclusion:

Overall, the manuscript addresses an important and timely topic with a solid modeling approach. With the clarifications and revisions suggested above, the study will present a clearer and more robust contribution to our understanding of CDOM effects in Arctic coastal systems.
Citation: https://doi.org/10.5194/egusphere-2025-973-RC1
- AC1: 'Reply on RC1', Clement Bertin, 21 Jun 2025
  
  Dear reviewer,
  Please find attached the pdf file with the answers to your comments.
  Best regards,
  The authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-973-AC1
RC2:
'Comment on egusphere-2025-973', Anonymous Referee #2, 31 May 2025

Please find my review of the paper in the attachment.

Citation: https://doi.org/10.5194/egusphere-2025-973-RC2
- AC2:
  'Reply on RC2', Clement Bertin, 21 Jun 2025
  
  Dear reviewer,
  Please find attached the pdf file with the answers to your comments.
  Best regards,
  The authors
  
  Citation: https://doi.org/10.5194/egusphere-2025-973-AC2
  - AC3: 'Reply on AC2', Clement Bertin, 23 Jun 2025
    
    We noticed that we omitted to answer one comment from the review.
    
    Below is the specific answer to this comment:
    According to reviewer comment, we changed the first sentence of the abstract (L1-2) as follows: “Arctic warming affects land-to-ocean fluxes of organic matter through increased permafrost thaw, coastal erosion or river discharge, with significant impacts on coastal ecosystems and air-sea CO₂fluxes” and changed the term terrestrial browning by: “terrestrial organic matter input” (L7).
    Apologies for the missing answer.
    
    The authors
    
    Citation: https://doi.org/10.5194/egusphere-2025-973-AC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (24 Jun 2025) by Huixiang Xie

Dear authors,

Thank you very much for your responses to the reviewers’ comments. I have carefully examined your responses and am now inviting you to submit a revised manuscript. Please modify the manuscript according to the plan you described in the response letters. In addition, please pay attention to the following points when revising the manuscript.

Your response to reviewer#1’s major comment#4
The responses do not directly address the three aspects which the reviewer requested to clarify. Please clarify them when revising the manuscript.

Your response to reviewer#2’s comment#2.
Please provide references to your statement that the degradation of CDOM produces DON and DOP according the canonical Redfield ratio. To my knowledge, CDOM is enriched with high-molecular-weight DOM, which is relatively richer in carbon but poorer in N and P compared to fresh DOM or POM. Moreover, the end products of degradation of CDOM (either microbial or photochemical) are inorganic compounds (e.g., CO2, DIN, and DIP), although the refractory fractions remain as organic forms. I think what really you intend to mean is that the stoichiometry of CDOM follows the canonical Redfield ratio (but this may not be true as I mentioned above).

Your response to reviewer#2’s comment#3.
Particulate matter contains organic matter, part of which comprises chromophores (i.e., colored particulate organic matter or CPOM). Like CDOM, CPOM also absorbs light and produces heat. Even some particulate minerals, such as Fe, Mn, etc., also absorb light throughout the UV-visible spectrum. Although the effect of particle light backscattering may overtake the effect of CPOM and mineral light absorption, it’s probably premature to say particulate matter does not produce heat.

Associate Editor’s comments
L27: What do you mean by “complex aromatic cycles”?
L38: I would remove “drastically”. This is an exaggeration.
L38: Belanger et al. (2006) did not directly study the effect of CDOM on primary production. This is not an appropriate reference.
Figure 1: This figure uses “tDOC” in two instances without spelling it out. However, the definition of tDOC in main text (L100) occurs after the citation of Figure 1 (L91).
L95: “bleaching rate of 1/6 days”. The units are days not a rate unit. Is this the turnover time? (I doubt it. I do not think CDOM photobleaching is so fast). Or is it 1/6 (i.e. 0.17) per day? If so, it is the first-order bleaching rate constant (corresponding to a turnover time of 6 days). Please clarify.
L95: Does this rate apply to the euphotic zone, surface mixed layer, or the exact surface (depth~0 m)?
L96-97: Why CDOM photobleaching rate does not further increase when light intensity is >13W m-2?
L117-118: The MKR delivers a large load of particles. Scattering is potentially an important contribution to light attenuation in the water column.
Figure 2a: No explanation why “aCDOM(440)” is in the graph.
Equation 1: The calculation of KCDOM is confusing. First, the contribution of CDOM absorption to light attenuation is far more important than the contribution of CDOM scattering. So, what’s the point of calculating KCDOM (i.e., aCDOM ~=KCDOM). Second, the Mackenzie River delivers a large load of particles. Particle scattering is potentially an important contribution to light attenuation in the water column. Please justify neglecting the particle scattering. Third, according to equation 1, KCDOM is dimensionless, while in fact KCDOM is in m-1 (L122). Please clarify.
L257: KCDOM. CDOM should be in subscript.

Please submit the revised manuscript before July 14, 2025.

Kind regards,

Huixiang Xie

Hide

AR by Clement Bertin on behalf of the Authors (08 Jul 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (12 Jul 2025) by Huixiang Xie

RR by Anonymous Referee #1 (28 Jul 2025)

Suggestions for revision or reasons for rejection

I would like to thank the authors for the revisions made following the first round of comments. The discussion has been improved and is now clearer and more compelling. I have noted a few minor revisions and typographical errors, which are listed below:

L.319 stating for starting
L.320 phytoplankton decline for phytoplankton declines
L.354 how do you define high values of CDOM?

L.399-400 The interpretation suggesting a “match-mismatch” with zooplankton is conceptually unclear in this context, given that zooplankton seems implemented as a general closure term in the model. If there is no explicit representation of zooplankton dynamics (e.g., no seasonal or phenological variability), the notion of temporal decoupling between phytoplankton and zooplankton seems inappropriate. I would suggest rephrasing this sentence to better reflect the limitations imposed by the closure term formulation — for example, by discussing how the imposed grazing pressure might artificially lower Chla levels after the bloom, without implying an actual mismatch.

Throughout the manuscript, “Chl” is used to refer to chlorophyll a. For clarity and to avoid ambiguity with other chlorophyll types, I recommend consistently using “Chl a” or “Chla”, which is the standard abbreviation for chlorophyll a in the oceanographic and biogeochemical literature.

There is an inconsistency in the manuscript regarding the spelling of “sea ice” — it appears both as “sea ice” and “sea-ice”. I recommend choosing one form and using it consistently throughout the text. Unless used as a compound adjective (e.g., “sea-ice concentration”), the unhyphenated form “sea ice” is generally preferred.

Hide

RR by Anonymous Referee #2 (05 Aug 2025)

ED: Publish subject to minor revisions (review by editor) (07 Aug 2025) by Huixiang Xie

Dear authors,

Both reviewers gave favorable opinions on the revised manuscript. However, a few more minor revisions are needed before the manuscript can be accepted for publication. Please provide a point-by-point response to the reviewers’ comments (appended below), and either change the manuscript appropriately or provide convincing reasons for declining to do so.

Kind regards,

Huixiang Xie

Reviewer#1

I would like to thank the authors for the revisions made following the first round of comments. The discussion has been improved and is now clearer and more compelling. I have noted a few minor revisions and typographical errors, which are listed below:

L.319 stating for starting
L.320 phytoplankton decline for phytoplankton declines
L.354 how do you define high values of CDOM?

L.399-400 The interpretation suggesting a “match-mismatch” with zooplankton is conceptually unclear in this context, given that zooplankton seems implemented as a general closure term in the model. If there is no explicit representation of zooplankton dynamics (e.g., no seasonal or phenological variability), the notion of temporal decoupling between phytoplankton and zooplankton seems inappropriate. I would suggest rephrasing this sentence to better reflect the limitations imposed by the closure term formulation — for example, by discussing how the imposed grazing pressure might artificially lower Chla levels after the bloom, without implying an actual mismatch.

Throughout the manuscript, “Chl” is used to refer to chlorophyll a. For clarity and to avoid ambiguity with other chlorophyll types, I recommend consistently using “Chl a” or “Chla”, which is the standard abbreviation for chlorophyll a in the oceanographic and biogeochemical literature.

There is an inconsistency in the manuscript regarding the spelling of “sea ice” — it appears both as “sea ice” and “sea-ice”. I recommend choosing one form and using it consistently throughout the text. Unless used as a compound adjective (e.g., “sea-ice concentration”), the unhyphenated form “sea ice” is generally preferred.

Reviewer#2
In my view the comments of both reviewers and editor were well addressed by the authors. I would therefore recommend the paper for publication. A few minor points from reading the manuscript again:

L11 "..(IPCC, 2023).."
I would cite the specific chapter.

L14 "..or roughly 7% of the global-ocean sink.."
There are more recent more comprehensive observation and model based estimates for the global coastal ocean CO2 sink:

Dai, Minhan, et al. "Carbon fluxes in the coastal ocean: synthesis, boundary processes, and future trends." Annual Review of Earth and Planetary Sciences 50.1 (2022): 593-626.

Resplandy, L., Hogikyan, A., Müller, J. D., Najjar, R. G., Bange, H. W., Bianchi, D., et al. (2024). A synthesis of global coastal ocean greenhouse gas fluxes. Global Biogeochemical Cycles, 38, e2023GB007803. https://doi.org/10.1029/2023GB007803

L65 "Here" -> Here,

L89 "..the terrestrial dissolved organic matter pool is not constrained by a constant C:N:P ratio." -> The terrestrial dissolved organic matter pools are not constrained by a fixed stoichiometric ratio (such as in other studies?).

L100 Maybe state the CDOM pools are constrained by fixed ratio due to lack of data, and the assumption would be somewhat uncertain?

L106 "..un-published data from Nunataryuk field campaign.."
Potentially add the relevant data to supplementary information?

Hide

AR by Clement Bertin on behalf of the Authors (10 Sep 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (15 Sep 2025) by Huixiang Xie

AR by Clement Bertin on behalf of the Authors (15 Sep 2025) Manuscript

Journal article(s) based on this preprint

07 Nov 2025

Colored dissolved organic matter (CDOM) alters the seasonal physics and biogeochemistry of the Arctic Mackenzie River plume

Clément Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

Biogeosciences, 22, 6607–6629, https://doi.org/10.5194/bg-22-6607-2025,https://doi.org/10.5194/bg-22-6607-2025, 2025

Short summary

Clement Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

Supplement

https://doi.org/10.5194/egusphere-2025-973-supplement

Data sets

Model Outputs from ED-SBS with CDOM Bertin Clément https://doi.org/10.5281/zenodo.14969145

Model code and software

ED-SBS CDOM setup Clement Bertin, Dustin Carroll, Dimitris Menemenlis, and Hong Zhang https://github.com/MITgcm-contrib/ecco_darwin/tree/master/regions/mac_delta/llc270/biogeochem_setup/carroll_2020_ecosystem/CDOM_setup

Clement Bertin, Vincent Le Fouest, Dustin Carroll, Stephanie Dutkiewicz, Dimitris Menemenlis, Atsushi Matsuoka, Manfredi Manizza, and Charles E. Miller

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Short summary

We adjusted a model of the Mackenzie River region to account for the riverine export of organic matter that affects light in the water. We show that such export causes a delay in the phytoplankton growth by two weeks and raises the water surface temperature by 1.7 °C. We found that temperature increase turns this coastal region from a sink of carbon dioxide to an emitter. Our findings suggest that rising exports of organic matter can significantly affect the carbon cycle in Arctic coastal areas.


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