Cyanobacterial Blooms in Lake Varese: Analysis and Characterization over Ten Years of Observations

Round 1

Reviewer 1 Report

This paper is clearly on the climatic wave and give strong preference to physico-chemical driving factors. Please – ad at least a subsection, which will present the fact, that biotic interactions and the history of the lake (inoculum in sediments) play also the important and in some years strongly driving forces affecting on only the total biomass of cyanobacterial blooms but also the species composition. I have problem with the methodology of this paper – we are in 21^st century and, please, have a look on the number of on-line and in-situ technologies which can send the data every hour. It is not a toy for cyanobacterial ecologist, it is real tool, which can improve our knowledge concerning the autecology, dynamic of revitalisation and species composition, colony formation, biotic interaction etc. etc.  The statement, why you were sampling only 6times per season is essential (and you can add some advantage of your sampling approach like more detailed taxonomic groups composition etc.) Table 1 show the physical-chemical variables. Averages are good, but the stratification during the season is the key factor driving the dominance, composition and biomass of phytoplankton, so add some sentences describing the stratification of N, P, oxygen, temperature Figure 2b show the biovolume: 2013 less than 10%, 2014 more than 50%... it is pity, that you did not add the more recent data, because 2015-2019 were dry season also in Lombardia and the biovolume and total cyanobacterial biomass could more strongly illustrate the effect of meteorological drivers as you are describing in this paper. Could you please add some sentences concerning the actual situation? Iron is essential nutrient in these conditions, could you add some information concerning the iron fraction, forms, concentrations in pelagial and in sediments? There are a numbers of models for prediction of cyanobacterial blooms, including a complicated and sophisticated neural network models. Please can you enrich the discussion about other models and state why you did select the multiple linear regression as the acceptable predictor? I am strongly missing the true, which should be stated at the of discussion, that also other factors can strongly influence the cyanobacterial bloom formation. For example, the turbidity, even in high temperature can shift the taxa composition (what is here not mentioned at all), and even total biomass of cyanobacteria. Discussion must be enriched by these information, or less oriented readers will believe, that just temperature is the most important factor driving the cyanobacterial blooms, but, however, such a simple task it is not.

Author Response

Thank you very much. Please see the attached file as the responses.

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript presents an effort to model cyanobacteria dominance using an impressive long term data set. The importance of such a data set would not go unnoticed. The results have both biological and management implications. However, this work would benefit from a refocusing and formatting of text, particularly in an effort to distill down the primary goals and conclusions drawn. The manuscript would benefit from a stronger connection and clear theme from the introduction through the discussion. 

Please see attached document for specific comments and suggestions. 

Comments for author File: Comments.docx

Author Response

Thank you very much. Please see the attached file as the responses.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript is sound and conclusions drawn based on the analysis are within reach. However, the manuscript could benefit from some english revisions.

Author Response

Thank you very much. Please see the attached file as the responses.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Even paper is improved, still there are old data, lack of new analytical methods, interpretation focussed on temperature, even it is known, that cyanobacterial blooms formation is strongly multifactorial process...  consider please if you really need such a low novelty paper published with your name...

Author Response

Please see attached the replies to the reviewer's comments as pdf file

Author Response File: Author Response.pdf

Reviewer 2 Report

Introduction

Line 39: Suggest removing "which are directly exposed to them." This is implied. 

Line 43-44: Sentence structure, suggest "considering the negative impacts of cyanobacterial blooms on economic and human health.... importance for lake management." 

Line 61: Verb agreement, "confirm" 

Line 62: Remove "also" 

Line 72: Verb agreement, "it has been shown that.." 

I appreciate addition of paragraphs starting line 84 and line 102. This information will allow others to compare their lakes to Lake Varese, and speaks to applicability of the study. 

 

Materials and Methods

Line 185: I'm not sure what "consistent with" means. I suggest changing this vague language. 

Line 220-222: Sentence starting "cyanobacteria were detected at..." is better suited for results rather than methodology. 

Section 2.4 (Statistical analysis): I'm not sure if this is due to the formatting for track changes, but I suggest simplifying this section into one or two complete paragraphs rather than short, 2-3 sentence paragraphs. This was one of the biggest issues I had with this manuscript, and appears in multiple sections. 

Results

Line 317: This is a repetitive statement that was made clear in the previous paragraph. 

Figure 2: I found it difficult to discern the blue shade for Cryptophyta and Cyanophyta. It may be possible to change this graph to include both color and pattern. 

Figure 3: Is it possible to update the legend to include mm3 as mm³?

I don't understand the rationale behind including Figure 3a and 3b together. Is this because authors suspect that precipitation and therefore water clarity are driving seasonal cyanobacteria distribution and the notable shift in species? 

I understand that this may be outside of the goals for this work, but considering the role of biotic interactions in driving algal blooms, were there any statistical explorations between the planktonic community and cyanobacteria. I see that other members of the planktonic community were identified and enumerated (Fig 2). 

I found the description for correlation between surface water temperature and stratification unnecessarily long and drawn out. The relationship between water temperature and stratification strength is well-founded. 

Discussion

Again, this may be an artifact of track-changes formatting, but please ensure that sentences are grouped into sturdy paragraphs rather than 2-3 sentence sections. This significantly reduced the readability and flow of the manuscript. The discussion was very disjointed to me, especially when authors describe the role of abiotic parameters (temperature, stratification, wind speed) on cyanobacteria dominance. 

 

I appreciate that authors have added information as to how this work applies to other lakes. To drive this message home, I suggest adding to the end of line 596 "reduce their occurrence in ____ lakes," filling in for the type of lake this these data best represent. Eutrophic? shallow? monomictic? etc. 

Conclusion

The use of bulleted summary is helpful. However, authors may consider combining the 3rd and 4th topic. 

 

 

Author Response

Please see attached the replies to the reviewer's comments as pdf file

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The last version is OK.