the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Nov 2022
Model estimates of metazoans' contributions to the biological carbon pump
Abstract. The daily vertical migrations of fish and other metazoans actively transport organic carbon from the ocean surface to depth, contributing to the biological carbon pump. We use an oxygen-constrained, game-theoretic food-web model to simulate diel vertical migrations and estimate global carbon fluxes and sequestration by fish and zooplankton due to respiration, fecal pellets, and deadfalls. Our model provides estimates of the carbon export and sequestration potential for a range of pelagic functional groups, despite uncertain biomass estimates of some functional groups. While the export production of metazoans and fish is modest (∼20 % of global total), we estimate that their contribution to carbon sequestered by the biological pump (∼ 800 PgC) is conservatively more than 50 % of the estimated global total (∼1300 PgC) and have a significantly longer sequestration time scale (∼250 years) than previously reported for other components of the biological pump. Fish and multicellular zooplankton contribute about equally to this sequestered carbon pool. This essential ecosystem service could be at risk from both unregulated fishing on the high seas and ocean deoxygenation due to climate change.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1418 KB) - Metadata XML
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Supplement
(20255 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-1227', Emma Cavan, 27 Jan 2023
The study by Pinti et al provides a detailed analysis showcasing the importance of fish and other metazoa in the global ocean carbon cycle. This is an important study as it goes beyond just looking at zooplankton to also quantifying contributions of higher trophic levels. The modelling work is also able to capture the diel vertical migrations of different organisms, which is not a trivial process to express computationally. The paper is very well written with clear figures and logical conclusions and is an impressive amount of work. I believe this work will make a valuable contribution to the scientific community. I have very few comments:
- The authors state in abstract the paper is of global scale, and in the paper acknowledge it does not cover the poles. i think this should be mentionned upfront to make sure readers are aware of this early on. The poles are important in cycling of carbon with large biomasses of metazoa (e.g. Yang et al 2022).
- line 143, do fish ingest zooplankton in the mesopelagic or only at surface? How have you defined strongest trophic coupling?
- line 170 - define efficient, what does it mean in this context? Arguable most efficient is from primary production conversion of CO2 to organic matter, and then final sequestration.
Citation: https://doi.org/10.5194/egusphere-2022-1227-RC1 -
AC1: 'Reply on RC1', Jerome Pinti, 30 Jan 2023
Thank you very much for your comment and for taking the time to review our manuscript. To answer your three points:
1/ ok. We will modify the second sentence of the abstract to "...near-global (global ocean minus coastal areas and high latitudes) carbon fluxes and sequestration by fish and..."
2/ Fish can ingest zooplankton both in the mesopelagic and at the surface. However, the feeding rates will be very different because of temperature, light and oxygen effects on the different metabolic rates of animals. Strongest coupling simply refers to the largest flow of carbon between two functional groups. We add a reference to figure 1 in that sentence for clarity.
3/ We mean that it will be sequestered the longest (i.e. longest residence time scale). We modify "stored more efficiently" to "stored for a longer time" to avoid confusion.Thank you again for taking the time to review our manuscript.
Jerome Pinti
Citation: https://doi.org/10.5194/egusphere-2022-1227-AC1
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AC1: 'Reply on RC1', Jerome Pinti, 30 Jan 2023
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RC2: 'Comment on egusphere-2022-1227', Anonymous Referee #2, 30 Jan 2023
In this work, Pinti et al try to identify taxa and pathways mainly involved in carbon storage using a pelagic food web model. This is an important topic and an excellent scientific work. There is no doubt that this paper will be of strong impact in the scientific community. I especially appreciated that the authors take into account functional groups including jellyfish and the potential impact of bathypelagic fish in the discussion. I also appreciated information provided in the supplementary materials but felt a little bit difficult to read the main paper without the model detailed in the main text.
Very minor questions/comments:
- Is it possible to have more than one Nash equilibrium in this case?
- The comparison with Nowicki publication seems to have a major difference without fish and jellies which can strongly modify the similarities between these works. This is notified but I am not sure if the comparison of figures between these two works is realistic then.
- The discussion about how this work could provide baseline for future assessments for fishing (L263 and then 323) is extremely short. In particular, the authors state that the main uncertainty in their work is about mesopelagic fish biomass. This potential bias is taken into account and highlighted at the beginning and in the discussion, and by doing so they highlight the need of a better estimate in biomass. Could you develop a little bit based on your model results what would happen for carbon sequestration if you decrease the biomass by 50% as mentioned from St john2016?
Citation: https://doi.org/10.5194/egusphere-2022-1227-RC2 -
AC2: 'Reply on RC2', Jerome Pinti, 01 Feb 2023
Thank you very much for your comment and for taking the time to review our manuscript. Our answers to your three comments are as follow:
1/ Yes, it is theoretically possible to have several Nash equilibria in this case (depending on initial conditions). We investigated this with a number of different initial conditions, and did not find several equilibria in any of the set ups tested. We will add a comment about this to the section of the SI talking about Nash equilibria (section 1.5).
2/ While we agree that both studies are different, the comparison with Nowicki was provided because it is the only other study we know of that estimates the sequestration of carbon mediated by different pathways of the biological carbon pump on a global scale. We can still compare the relative importance of different pathways (eg fecal pellets vs. respiration) with Nowicki's study, as we do in the discussion.
3/ It is a bit hard to predict what will happen to carbon export and sequestration as a harvest rate does not linearly relates to a biomass decrease. However, you are right that our discussion was a bit thin on that topic. We can expend the discussion after l. 323 to talk about the difficulties of relating the harvest rate to carbon export and sequestration: "The exact form of this trade-off is hard to assess, as the rate of biomass harvest cannot be equated to the biomass inventory -- and thus to the export rate and inventory of sequestered DIC. Indeed, if the harvest can be done sustainably and without affecting the total biomass, then it is possible that it has relatively little impact on carbon sequestration".
Citation: https://doi.org/10.5194/egusphere-2022-1227-AC2
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-1227', Emma Cavan, 27 Jan 2023
The study by Pinti et al provides a detailed analysis showcasing the importance of fish and other metazoa in the global ocean carbon cycle. This is an important study as it goes beyond just looking at zooplankton to also quantifying contributions of higher trophic levels. The modelling work is also able to capture the diel vertical migrations of different organisms, which is not a trivial process to express computationally. The paper is very well written with clear figures and logical conclusions and is an impressive amount of work. I believe this work will make a valuable contribution to the scientific community. I have very few comments:
- The authors state in abstract the paper is of global scale, and in the paper acknowledge it does not cover the poles. i think this should be mentionned upfront to make sure readers are aware of this early on. The poles are important in cycling of carbon with large biomasses of metazoa (e.g. Yang et al 2022).
- line 143, do fish ingest zooplankton in the mesopelagic or only at surface? How have you defined strongest trophic coupling?
- line 170 - define efficient, what does it mean in this context? Arguable most efficient is from primary production conversion of CO2 to organic matter, and then final sequestration.
Citation: https://doi.org/10.5194/egusphere-2022-1227-RC1 -
AC1: 'Reply on RC1', Jerome Pinti, 30 Jan 2023
Thank you very much for your comment and for taking the time to review our manuscript. To answer your three points:
1/ ok. We will modify the second sentence of the abstract to "...near-global (global ocean minus coastal areas and high latitudes) carbon fluxes and sequestration by fish and..."
2/ Fish can ingest zooplankton both in the mesopelagic and at the surface. However, the feeding rates will be very different because of temperature, light and oxygen effects on the different metabolic rates of animals. Strongest coupling simply refers to the largest flow of carbon between two functional groups. We add a reference to figure 1 in that sentence for clarity.
3/ We mean that it will be sequestered the longest (i.e. longest residence time scale). We modify "stored more efficiently" to "stored for a longer time" to avoid confusion.Thank you again for taking the time to review our manuscript.
Jerome Pinti
Citation: https://doi.org/10.5194/egusphere-2022-1227-AC1
-
AC1: 'Reply on RC1', Jerome Pinti, 30 Jan 2023
-
RC2: 'Comment on egusphere-2022-1227', Anonymous Referee #2, 30 Jan 2023
In this work, Pinti et al try to identify taxa and pathways mainly involved in carbon storage using a pelagic food web model. This is an important topic and an excellent scientific work. There is no doubt that this paper will be of strong impact in the scientific community. I especially appreciated that the authors take into account functional groups including jellyfish and the potential impact of bathypelagic fish in the discussion. I also appreciated information provided in the supplementary materials but felt a little bit difficult to read the main paper without the model detailed in the main text.
Very minor questions/comments:
- Is it possible to have more than one Nash equilibrium in this case?
- The comparison with Nowicki publication seems to have a major difference without fish and jellies which can strongly modify the similarities between these works. This is notified but I am not sure if the comparison of figures between these two works is realistic then.
- The discussion about how this work could provide baseline for future assessments for fishing (L263 and then 323) is extremely short. In particular, the authors state that the main uncertainty in their work is about mesopelagic fish biomass. This potential bias is taken into account and highlighted at the beginning and in the discussion, and by doing so they highlight the need of a better estimate in biomass. Could you develop a little bit based on your model results what would happen for carbon sequestration if you decrease the biomass by 50% as mentioned from St john2016?
Citation: https://doi.org/10.5194/egusphere-2022-1227-RC2 -
AC2: 'Reply on RC2', Jerome Pinti, 01 Feb 2023
Thank you very much for your comment and for taking the time to review our manuscript. Our answers to your three comments are as follow:
1/ Yes, it is theoretically possible to have several Nash equilibria in this case (depending on initial conditions). We investigated this with a number of different initial conditions, and did not find several equilibria in any of the set ups tested. We will add a comment about this to the section of the SI talking about Nash equilibria (section 1.5).
2/ While we agree that both studies are different, the comparison with Nowicki was provided because it is the only other study we know of that estimates the sequestration of carbon mediated by different pathways of the biological carbon pump on a global scale. We can still compare the relative importance of different pathways (eg fecal pellets vs. respiration) with Nowicki's study, as we do in the discussion.
3/ It is a bit hard to predict what will happen to carbon export and sequestration as a harvest rate does not linearly relates to a biomass decrease. However, you are right that our discussion was a bit thin on that topic. We can expend the discussion after l. 323 to talk about the difficulties of relating the harvest rate to carbon export and sequestration: "The exact form of this trade-off is hard to assess, as the rate of biomass harvest cannot be equated to the biomass inventory -- and thus to the export rate and inventory of sequestered DIC. Indeed, if the harvest can be done sustainably and without affecting the total biomass, then it is possible that it has relatively little impact on carbon sequestration".
Citation: https://doi.org/10.5194/egusphere-2022-1227-AC2
Peer review completion
Journal article(s) based on this preprint
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Jérôme Pinti
Tim DeVries
Tommy Norin
Camila Serra-Pompei
Roland Proud
David A. Siegel
Thomas Kiørboe
Colleen M. Petrik
Ken H. Andersen
Andrew S. Brierley
Andre W. Visser
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1418 KB) - Metadata XML
-
Supplement
(20255 KB) - BibTeX
- EndNote
- Final revised paper