The Effects of Hypoxia on Threshold Food Concentrations in Different Daphnia Species

Round 1

Reviewer 1 Report

This paper aimed to assess the effects of various environmental factors on the competitive abilities of different Daphnia genotypes. The design used in this study seems appropriate. My issue with the the paper is the lack of coherence in across all parts from the introduction up to the discussion. Making it difficult to fully comprehend the study. I suggest that the authors would consult a technical editor at the very least to further enhance the manuscript. 

Minor comments are attached in the manuscript. Please check them out. 

Comments for author File: Comments.pdf

Author Response

This paper aimed to assess the effects of various environmental factors on the competitive abilities of different Daphnia genotypes. The design used in this study seems appropriate. My issue with the the paper is the lack of coherence in across all parts from the introduction up to the discussion. Making it difficult to fully comprehend the study. I suggest that the authors would consult a technical editor at the very least to further enhance the manuscript. 

Minor comments are attached in the manuscript. Please check them out. 

Dear Reviewer,

We have carefully read your general comment, as well as your minor comments. In accordance with your general comment, we had our colleague, most experienced with technical editing, read and correct the whole manuscript (he has now been included in acknowledgements). The changes throughout the whole text were made in the “track changes” mode, we believe that with a proper introduction and more explicit (yet shorter) methods, the manuscript no longer lacks coherence. We thank you for your comments as they have significantly contributed to improving our manuscript.

As for the minor comments, our response (below) is marked in blue:

Please completely re-write the introduction part as it lacks coherence.

The entire introduction section has been completely rewritten based on your, the second reviewer’s and the technical editor’s comments. Thank you for this comment.

Re-write first sentence probably about importance of body size in adaptation to various environmental conditions/stresses.

In accordance with your comment, we rewrote the first part of the introduction, beginning it with a sentence about the importance of ectotherms’ body size in adaptation to environmental conditions. (Page 2, line 40-43 in the revised manuscript, display tracked changes mode).

Why is this bold?

Same as this, why is this in bold?

Why bold?

In accordance with your comment, we have removed the bold text from these parts (Page 2, lines: 69, 74, 76 in the revised manuscript, display tracked changes mode).

cite the work of Reyes, V.P.; Ventura, M.A.; Amarillo, P.B. Ecotoxicological Assessment of Water and Sediment in Areas of Taal Lake with Heavy Aquaculture Practices Using Allium Cepa and Daphnia Magna Assay. Philipp J. Sci. 2022, 151, 969–974.

In accordance with your comment, we have cited this study in this part of the introduction section (Page 2, line 87 in the revised manuscript, display tracked changes mode).

Literature

Modified (Page 3, line 115 in the revised manuscript, display tracked changes mode).

Author Response File: Author Response.doc

Reviewer 2 Report

A report for: Water-1922927, The effects of hypoxia on threshold food concentrations in different Daphnia species

I have reviewed the manuscript that aims to understand relation among the body size, water temperature, oxygen concentration and food availability in aquatic ectotherm organisms. This type of studies are always interesting. The subject fall within the general scope of the journal and the title quite clearly reflects the contents of the paper.

The manuscript describes the results of several lab experiments and although the language is quite good; however it is difficult to recommend this manuscript for publication in the present form. The main concern is that I struggled for completely understanding the experimental plan and the obtained results, and consequently the discussion. Often in the manuscript, species with different body size are mixed/confused with adults (can you confirm that) of same species with diffent body size. Some section could be improved as suggested below.

 Introduction: several concepts have to be clarify and explained.

Lines 35-36. ‘’The individuals, populations and communities of ectotherms reach a smaller body size in warmer as compared to cooler environments ’’. The sentence has to be re-written using more words to better explain the content, although the authors elucidate that after 15 lines. For example, what is the means of ‘’ communities of ectotherms reach a smaller body size’’?

Species with different body size or individuals (belonging the same species) with different body size.

Line 59. The reference 19 doesn’t seem to be in the right context. Probably, the reference is not useful for the manuscript topic.

Line 103-113. the aims have to be better defined and developed, and they are not to be inferred by the reader.

 Methods: the section is very complicate to follow; the reader has to spend a lot of time to understand, interpret and sometime image the different experiments, number of individuals and species involved, number of replicates…I suggest to create a diagram that highlight the experimental plan and be more clear in the text.

 Results

Figures: when available please add statistical analysis parametres, e.g. in fig 1 regression paramenters, such us R², p... ect.

Some results need to be supported with higher efforts, and the analyses have to be completely presented. For example (Line 228...) ‘’ Although we have not detected any interaction between  oxygen concentration and species (p = 0.2656, likelihood-ratio chi-squared test), upon grouping the species into two clusters: lake cluster (comprising smaller species) and pond cluster (comprising larger species), the statistical analysis has shown that decreased oxygen concentrations had different effect on the groups. In this sentence, only p is presented ... that is not enough... in which figure it is possible to appreciate the absence of the relationship, reader has to understand in deep the analysis.                        Line 247...’’ lake cluster (comprising smaller species) and pond cluster (comprising larger species), the statistical analysis has shown that decreased oxygen concentration has increased the TFC of the lake cluster more than the pond cluster by 3.8 – 57.9 % (95% bootstrapped CI)’’.

Please add a figure of cluster, or deeply explain this part that in this way is really difficult to understand.

All the results have to be revised following this approach.

 Discussion: In general, it was very difficult following this section, as experimental plan and results were difficult to understand.

 Conclusion: It is necessary to add a section with the most important conclusions

 I wish those changes will contribute to improve your paper.

Author Response

I have reviewed the manuscript that aims to understand relation among the body size, water temperature, oxygen concentration and food availability in aquatic ectotherm organisms. This type of studies are always interesting. The subject fall within the general scope of the journal and the title quite clearly reflects the contents of the paper.

The manuscript describes the results of several lab experiments and although the language is quite good; however it is difficult to recommend this manuscript for publication in the present form. The main concern is that I struggled for completely understanding the experimental plan and the obtained results, and consequently the discussion. Often in the manuscript, species with different body size are mixed/confused with adults (can you confirm that) of same species with diffent body size. Some section could be improved as suggested below.

Dear Reviewer,

We have carefully read your general comment, as well as your minor comments. In accordance with your general comment, we had our colleague, most experienced with technical editing, read and correct the whole manuscript (he has now been included in acknowledgements). The changes throughout the whole text were made in the “track changes” mode, we believe that with a proper introduction and more explicit (yet shorter) methods, the manuscript no longer lacks coherence. We thank you for your comments as they have significantly contributed to improving our manuscript.

As for the minor comments, our response (below) is marked in blue:

 Introduction: several concepts have to be clarify and explained.

Lines 35-36. ‘’The individuals, populations and communities of ectotherms reach a smaller body size in warmer as compared to cooler environments ’’. The sentence has to be re-written using more words to better explain the content, although the authors elucidate that after 15 lines. For example, what is the means of ‘’ communities of ectotherms reach a smaller body size’’?

Species with different body size or individuals (belonging the same species) with different body size.

In accordance with your comment, we have clarified the oversimplified description of body size trends in individuals, populations and communities by more explicitly outlining the first paragraphs in the introduction – as you indicated, what we meant was to describe the trends in the body size of individuals, the mean body size of individuals in populations and species in the communities of ectotherms. (Page 2, line 43-47 in the revised manuscript, display tracked changes mode). Moreover, we have rewritten this part more elaborately, including the importance of body size in ectotherms’ adaptation to various environmental conditions.

Line 59. The reference 19 doesn’t seem to be in the right context. Probably, the reference is not useful for the manuscript topic.

Indeed. In accordance with your comment, we have completely deleted this reference from the revised manuscript.

Line 103-113. the aims have to be better defined and developed, and they are not to be inferred by the reader.

In accordance with your comment, we rewrote the aim more elaborately, so that the reader does not have to backtrack and infer the aim of our study (Page 4, line 139-142 in the revised manuscript, display tracked changes mode).

 Methods: the section is very complicate to follow; the reader has to spend a lot of time to understand, interpret and sometime image the different experiments, number of individuals and species involved, number of replicates…I suggest to create a diagram that highlight the experimental plan and be more clear in the text.

In accordance with your comment, we have completely rewritten most of the Methods section in order for it to be shorter, yet more informative and easier to understand. Moreover, as you have suggested, we added a diagram highlighting the experimental plan (Page 5, line 189 in the revised manuscript, display tracked changes mode).

Results

Figures: when available please add statistical analysis parametres, e.g. in fig 1 regression paramenters, such us R², p... ect.

In accordance with your comment, across the whole Results section, we have added the R2 parameters for our regression models. Moreover, wherever it was possible (everywhere except for the bootstrapping analyses), we have added p – values.

Some results need to be supported with higher efforts, and the analyses have to be completely presented. For example (Line 228...) ‘’ Although we have not detected any interaction between  oxygen concentration and species (p = 0.2656, likelihood-ratio chi-squared test), upon grouping the species into two clusters: lake cluster (comprising smaller species) and pond cluster (comprising larger species), the statistical analysis has shown that decreased oxygen concentrations had different effect on the groups. In this sentence, only p is presented ... that is not enough... in which figure it is possible to appreciate the absence of the relationship, reader has to understand in deep the analysis.                        

In accordance with your comment, across the whole Results section, we have added additional values for the reader to better understand our analysis. We have added the likelihood-ratio (LRT) values incorporated into the analysis.

Line 247...’’ lake cluster (comprising smaller species) and pond cluster (comprising larger species), the statistical analysis has shown that decreased oxygen concentration has increased the TFC of the lake cluster more than the pond cluster by 3.8 – 57.9 % (95% bootstrapped CI)’’.

Please add a figure of cluster, or deeply explain this part that in this way is really difficult to understand.

Perhaps this has not been described elaborately enough in the Methods section – in accordance with your comment, across the whole Results section (wherever the clusters were mentioned), we have indicated precisely which species belonged to the clusters earlier mentioned in the methods.

All the results have to be revised following this approach.

 Discussion: In general, it was very difficult following this section, as experimental plan and results were difficult to understand.

We hope that after both yours and reviewer 1’s comments, as well as the changes made by our technical editor, the whole manuscript, including the discussion section, has been significantly improved.

Conclusion: It is necessary to add a section with the most important conclusions

In accordance with your comment, we have rewritten the conclusions more elaborately, highlighting our most important findings (Page 13, line 418-428 in the revised manuscript, display tracked changes mode).

I wish those changes will contribute to improve your paper.

Once more thank you very much for the valuable comments. We believe they were of vital importance as we could not notice many of the shortcomings in the manuscript ourselves.

Author Response File: Author Response.docx