Dissolved Oxygen in a Shallow Ice-Covered Lake in Winter: Effect of Changes in Light, Thermal and Ice Regimes

Round 1

Reviewer 1 Report

Interesting use of available ice and winter climate data. The results are rather predictable - a person with a good grasp of lake ice dynamics could guess the relationships between ice-cover, temperature, and DO before the data is even plotted - but it is good to have solid evidence to add to winter water research. I do question how useful the FLake model was in this manuscript.  It does not appear to have much purpose other than being something you can plot.

I suggest some of the text be rewritten, and/or clarified to make the paper easier to read in sections. I have attached separate comments.

Good luck with your work.

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments. We have taken into account your recommendations (all corrections are highlighted in green in the manuscript) and hope that the manuscript is now more structured and clearer. Please note that some of the figures and tables have been moved to additional materials, therefore the numbering of figures and tables has changed.

Author Response File: Author Response.docx

Reviewer 2 Report

This is a valid scientific paper, accurately reporting the results of a well-designed research. The only relevant shortage of the manuscript in its present form is the lack of details about the setup of the FLake model for the case study: this needs to be addressed. I understand that the Authors want to mainly concentrate on field results, yet the specifics of modelling exercises should always be illustrated for the sake of repeatability. The manuscript is also generally well written, apart from few word and punctuation usage issues, in addition to rare spelling mistakes, so that an accurate review by the Authors is recommended. Here below are some further minor conceptual issues:

L61-62: How can light intensity be measured in μmol/(m^2·s)?

L153-154: What does the measurement interval of “1-5” minutes mean in practice?

L203-209: Is there any literature reference supporting the accuracy of these criteria?

Figure 2: Please put the lines and dots defining the ice period outside of the plot area, as at present they confuse the reader.

In light of my comments above, I think that the "minor revisions" judgement suits the manuscript in its present form.

Author Response

Thank you very much for your comments. We have taken into account your recommendations (all corrections are highlighted in green in the manuscript) and hope that the manuscript is now more structured and clearer. Please note that some of the figures and tables have been moved to additional materials, therefore the numbering of figures and tables has changed.

Author Response File: Author Response.docx

Reviewer 3 Report

The subject of the article is quite interesting and fits the broader scope of the journal which includes the interannual variability of aquatic ecosystem properties as a result of changing climate. A strong part of the paper is the extensive dataset which is largely based on actual field data. Another important aspect is that the manuscript is very well written (the language is ok as the grammar  and syntax). I found some significant issues mainly related with the quality of the presentation of the results as with the structure of results and discussion. The results need to shorten and the discussion definitely needs to be restructured as a large portion presents results that should be included in the previous section.

Another issue is the trend analysis itself which I think the authors should give larger emphasis on the methods section. They mention a student’s t statistic but it seems that they applied simple linear regression analysis to examine trends which whereas there are many other parametric or non-parametric methods for finding trends.

I would like to see an explanation on why the authors did not choose for instance to apply a Mann Kendall trend test with a subsequent estimation of Sen’s slopes.

In general, besides these weaknesses, I think the authors can address these issues, either with changes in the manuscript or with providing adequate explanations, and thus the manuscript can be improved and considered suitable for publication.

Abstract

The abstract is very well written and informative about the research presented in the paper. A minor comment is about the first introductory sentence and particularly when authors say that oxygen conditions in winter remain challenging. What is challenging about oxygen conditions? Maybe the authors refer to the monitoring of oxygen conditions and the identification of trends?

Keywords

I see shallow lake is included as keyword. Is your study lake considered a shallow lake. Mean and maximum depths are quite large for a typical shallow lake but I guess what is most important is the mixing regime. Typical shallow lakes are usually polymictic but based on the description in the methods the lake seems a typical dimictic lake. If you consider your study lake as shallow lake it should be mentioned in the manuscript along with details about depth and mixing regime. Else just remove the keyword.

Introduction

The introduction is also very well written (as the rest of the manuscript). It seems quite long but it provides relevant and useful information about the scope of the article.

L73: 10-20 layers of snow. I guess this refers to thickness of snow (e.g. cm?)

Methods

The authors have done a very good job in providing extensive details about their methods. I have just a minor comment which is concerns the possibility to provide the methods in subsections. For instance a subsection about the data, another about Flake etc. This makes easier for the reader to follow the methodology and understand the methodological steps that the authors applied.

Results

I found this section quite long and rather difficult to follow. I understand that the authors have conducted an extensive analysis finding various results but I suggest to prioritize their findings and present the most important and relevant with the subject. Some figures can be included in a supplementary section.

Another point is that it seems from the figures that the authors investigated for linear trends but for most variables R² is very low that indicates weak trend over time (e.g. Fig 3; Fig 4). Perhaps it would be beneficial for the paper to omit these figures (and include them in the supplementary) and just mention the trends (and weak R2 value in the text).

Discussion

The discussion includes another set of figures which in my opinion should be included in the results. Actually a large part of the discussion presents results from regressions that normally should be presented in the results section. I highly recommend to restructure both results and discussion because now it causes confusion to the readers.

Overall the authors provide detailed explanations of their findings, which is a good think, but given the current structure it is difficult to follow the findings  

Author Response

Thank you very much for your comments. We have taken into account your recommendations (all corrections are highlighted in green in the manuscript) and hope that the manuscript is now more structured and clearer. Please note that some of the figures and tables have been moved to additional materials, therefore the numbering of figures and tables has changed.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors have addressed all the issues and comments. I found the manuscript significantly improved and i believe that it can be accepted for publication.