Temperature Affects the Time Required to Discern the Relationship between Primary Production and Export Production in the Ocean
Round 1
Reviewer 1 Report
The functioning of the biological carbon pump responsible for regulating the climate on the planet is determined by two processes. The first is based on the binding of inorganic carbon in photosynthetic reactions to form organic matter. There is new production in the ocean. The second process determines the flow of organic matter to the ocean interior. These are export production, the intensity of which depends on new production and the structure of the food chain in the carbon cycle in the photic layer. There is a time lag between these two processes, which depends on both the temperature and the structure of the food chain. In natural conditions, it is complicated to determine this time lag. Therefore, the authors used ecosystem models to study the reaction of these two processes to temperature changes. At the same time, they used two types of ecosystems. The first ecosystem is based on small phytoplankton cells, and the second is based on large cells. The structure of the food chain has changed accordingly. Using these two models, the authors showed that the time lag significantly depends on the temperature of the medium. The importance of this work lies in the fact that it substantially improves our understanding of the functioning of the biological carbon pump in a wide range of ecosystems, from tropical to polar. In addition, it allows you to predict the response of ecosystems to temperature changes.
The structure of a model is adequate for natural ecosystems. Computational experiments with the model are also beyond doubt. In general, the work seems to be very interesting and can be published without significant corrections.
Author Response
Response: The comments of the first reviewer were all positive. The first reviewer made no suggestions for improving the manuscript. Therefore, I made no changes in response to the comments from the first reviewer.
Reviewer 2 Report
It will be better to have a methodology chapter to let the reader to understand the station location methods used to depict the originality of approach in results and discussion. The mention of station ALOHA in introduction with no detailed description about, mention station description on results chapter is to late. The station M also is used and mention it on discussions with no reference in methods why you consider to be relevant. The calculations based on food web model is unclear if is made with adaptation or just calibration to be used on specific ALOHA, M stations characteristics for comparison reasons or model validation in different conditions. Please try to be more organized in methods used description.
Author Response
Reviewer 2
It will be better to have a methodology chapter to let the reader to understand the station location methods used to depict the originality of approach in results in discussion. The mention of Station ALOHA in introduction with no detailed description about, mention station description on results chapter is to late. The Station M is also used and mention it on discussion with no reference in methods why you consider to be relevant. The calculation based on food web model is unclear if is made with adaptation or just calibration to be used on specific ALOHA. M stations characteristics for comparison reasons or model validation in different conditions. Please try to be more organized in methods used description.
Response: Information about Station ALOHA has been added in lines 32–39. Information about Station M appears in lines 456–465. Primary production rates at the two stations are virtually identical (540 and 553 mg C m−2 d−1, respectively), but the physical dynamics are very different. The food web model does a good job of explaining relationships at Station ALOHA but not at Station M. The comparison therefore provides a good assessment of what the model can and cannot do. The five adjustable parameters in the model (ef, f2L, f3, f5, and f6) were chosen to produce steady states with maximum resilience to perturbations. They were not chosen to give a good fit to any empirical data. This is explained in lines 282–284: The combination of the ef ratio and f2L, f3, f5, and f6 that produced a steady state with maximum resilience was then determined for different combinations of temperature and NPP.
Reviewer 3 Report
Dear Authors,
Please see the section-wise comments below on your research article with the following details.
Manuscript title: Temperature affects the time required to discern the relationship between primary production and export production in the ocean
Manuscript Number: water-1410044
Journal Submitted: Water
Specific Comments:
Title:
The title looks suitable, although a bit longer statement. Since it is based on a theoretical model, I guess you should avoid making such a bold statement in your title, or at least indicate from where it is coming. You may consider making it brief.
Abstract:
L 19-24: One of the most important factors appears to be the altitude; what other factors compound here, leading to a difference of one month to one year? Would you please explain it here?
The abstract does not conclude the outcomes of this theoretical study.
Since it is a theoretical model, please indicate the main limitations.
Keywords can also include NPP and EP.
Introduction:
L 33: Table 4???? How could you cite a study area without describing the background?
L 44-47: This isn't very clear. Especially lines 45-47. Please rephrase.
L 61-89: Too long paragraph.
The authors have not detailed any previous literature on theoretical food web modeling in marine ecosystems.
It would help if you also kept up with the standard layout of the paper i.e. study aims. Please add.
Materials and Methods:
Figure 1. What does the question mark indicate in almost every box? Would you please revise it? You must use some colorful boxes to differentiate and make it more appealing.
Table 1. This must be sent to the supplementary section.
I feel that the study design is well-explained. However, the authors must consider adding logical flow charts to depict their theoretical model proposed in this study.
I could not find enough details if someone else wants to replicate this study in the future.
Results:
L 296: ef ratios? Please explain.
Figure 3. Would you please enhance the clarity of this figure and use bold lines?
Figure 5. Same as for figure 3.
Figure 6. Please use a larger font size and bold lines in the figures.
Figure 7. The figure visibility is compromised. Please improve it.
Figure 8. Same as for figure 7.
The description of the results appears to be good as the authors remain concise.
Discussion:
L 439: Please provide the exact link to this information and not the website only.
L 488: This sub-heading should be revised, I guess.
L 550: ------?
I can see that the authors have discussed the results discussed from multiple angles and placed them into context without being overinterpreted.
Conclusions
Please avoid citing so many figures, tables, and references in this section. It would help if you stuck to what you have concluded and did not support your outcomes from previous studies. This does not make sense, and it looks like the conclusions are driven from other sources. This also indicates that this section is an extension of the discussions.
Would you please add another paragraph about the limitations of this food web modeling and the potential reasons and future strategies to overcome them in future modeling endeavors?
References:
The references are not formatted according to the journal format.
Author Response
Reviewer 3
The title looks suitable, although a bit longer statement. Since it is based on a theoretical model, I guess you should avoid making such a bold statement in your title, or at least indicate from where it is coming. You may consider making it brief.
Response: I did not change the title. I could avoid making such a bold statement by changing the title to: A theoretical study of the time required to discern the relationship between primary production and export production in the ocean. However, that is a longer title, and the reviewer also suggests making the title shorter.
L 19-24: One of the most important factors appears to be the altitude; what other factors compound here, leading to a difference of one month to one year? Would you please explain it here?
Response: I assume that the reviewer means latitude, not altitude. The previous sentence indicates that the problem is temperature, which of course varies with latitude. The last sentence makes the point that food webs at high latitudes are likely to be far from equilibrium. The biology just cannot keep up with the physics at low temperatures.
The abstract does not conclude the outcomes of this theoretical study.
Response: The important conclusions of the study are the last two sentences of the abstract.
Since it is a theoretical model, please indicate the main limitations.
Response: The abstract is limited to 200 words, and it is already 209 words. The Discussion section includes several paragraphs about the limitations of the study. If the limit on the word count in the abstract is raised to 300, I can discuss the limitations of the study, but I am already 9 words over the limit of 200.
Keywords can also include NPP and EP.
Response: I have added NPP and EP to the keywords.
L 33: Table 4???? How could you cite a study area without describing the background?
Response: I have added information about Station ALOHA in lines 32–39.
L 44-47: This isn't very clear. Especially lines 45-47. Please rephrase.
Response: I have modified the text as follows: Because organic matter cannot be exported until it is first produced, and because the mechanisms responsible for exporting organic matter are not intrinsically coupled to photosynthesis, there is understandably a time lag between photosynthetic production of organic matter and its export from the euphotic zone.
L 61-89: Too long paragraph. The authors have not detailed any previous literature on theoretical food web modeling in marine ecosystems. It would help if you also kept up with the standard layout of the paper i.e. study aims. Please add.
Response: I have cited several previous food web models that have been used to address some of the issues discussed in this paper. Those earlier studies include references [4] and [19]. I have broken the paragraph into two paragraphs. The first sentence of the second paragraph states the hypothesis that we are testing, and the subsequent sentences are corollary arguments.
Materials and Methods:
Figure 1. What does the question mark indicate in almost every box? Would you please revise it?
Response: I do not see any question marks in Figure 1. The question marks may have been artifacts that were created when the document was converted to a pdf.
You must use some colorful boxes to differentiate and make it more appealing.
Response: I did not make any changes in response to this comment.
Table 1. This must be sent to the supplementary section.
Response: The Supplementary Materials includes values of ef, f2L, f3, f5, and f6 that produce a steady state with maximum resilience as function of temperature and NPP and a Matlab computer program that can be used to find the values of ef, f2L, f3, f5, and f6 that produce a steady state with maximum resilience at any temperature and NPP. I can add Table 1 to the Supplementary Materials if the editors feel that it would be desirable to do that.
I feel that the study design is well-explained. However, the authors must consider adding logical flow charts to depict their theoretical model proposed in this study. I could not find enough details if someone else wants to replicate this study in the future.
Response: The Matlab computer program, complete with comments that explain what the program is doing, is included in the Supplementary Materials. Anyone can duplicate our results by running the computer program, and by changing the specified temperature and primary production rate (NPP), they can explore scenarios other than the ones we considered.
Results:
L 296: ef ratios? Please explain.
Response: The ef ratio was explained in lines 181–183: In the steady state, new production and export production are identical, and we refer to the ratio of new production to NPP [f ratio: 31] or export production to NPP [e ratio: 32, 33] as the ef ratio in accord with [19].
Figure 3. Would you please enhance the clarity of this figure and use bold lines?
Response: Done
Figure 5. Same as for figure 3.
Response: Done
Figure 6. Please use a larger font size and bold lines in the figures.
Response: Done
Figure 7. The figure visibility is compromised. Please improve it.
Response: Done
Figure 8. Same as for figure 7.
Response: Done
The description of the results appears to be good as the authors remain concise.
Discussion:
L 439: Please provide the exact link to this information and not the website only.
Response: This information can be obtained by using the vertical profiles dropdown menu that appears on this website. I have added this information to the text.
L 488: This sub-heading should be revised, I guess.
Response: Agreed. The sub-heading has been changed to Effects of lateral currents.
L 550: ------?
I can see that the authors have discussed the results discussed from multiple angles and placed them into context without being overinterpreted.
Conclusions
Please avoid citing so many figures, tables, and references in this section. It would help if you stuck to what you have concluded and did not support your outcomes from previous studies. This does not make sense, and it looks like the conclusions are driven from other sources. This also indicates that this section is an extension of the discussions.
Response: I have changed the heading to Conclusions and implications. We felt it would make sense to suggest ways that field work could be conducted to obtain realistic estimates of the relationship between photosynthetic rates and export production. Clearly this cannot be done with measurements made over spatiotemporal scales that are too small to integrate over the sources of variability cited in this manuscript, including time lags.
Would you please add another paragraph about the limitations of this food web modeling and the potential reasons and future strategies to overcome them in future modeling endeavors?
Response: I have added the following final paragraph: Although use of such methods may provide reliable empirical data that can be used to relate NPP to EP, there will remain the need for a theoretical understanding of those relationships that could be used to predict, for example, how carbon cycling and export production will change in response to global warming. Simple food web models (Fig. 1) are inappropriate for describing the behavior of such physically dynamic systems. An analogy might be made to the hierarchy of quantum mechanics, statistical mechanics, and classical mechanics in physics. Quantum mechanics is not used to describe a ball rolling down an inclined plane. Theoretical tools must be chosen that are appropriate to the task. Theoretical understanding of the behavior of these physically dynamic systems remains a challenge for future work.
References:
The references are not formatted according to the journal format.
Response: The references have been modified so that they are now in the correct format for
Round 2
Reviewer 3 Report
My only concern is adding one or two sentences at the end of the abstract as suggested in my previous comments. The authors have satisfied all the remaining concerns adequately.
