Spatio–Temporal Water Quality Determines Algal Bloom Occurrence and Possibly Lesser Flamingo (Phoeniconaias minor) Presence in Momella Lakes, Tanzania

Round 1

Reviewer 1 Report

This study investigated the changes of water physico-chemical variables, algal biomass, and lesser flamingo number in 12 consecutive months in the lakes Big Momella and Rishateni in northern Tanzania. The potential relationships among water physico-chemical variables, algal biomass, and lesser flamingo number were detected, and the tipping points (thresholds) of each variable were calculated. Generally speaking, this manuscript is well-written, and some results are interesting. However, since lesser flamingo number is depended on the abundance of blue-green algae A. fusiformis rather than harmful algal, we would like to see the dynamic of algal compositions instead of the total algal biomass. In addition, to better understand the relationships among water environmental factors, algal biomass, and lesser flamingo abundance, structural equation model (SEM) might be used.

Detail suggestions,

Line 46-49 Please separate this long sentence into some short ones.

Line 154 Please change “Dissolved Oxygen” to “dissolved oxygen”.

Line 236-242 To be better understanding, please add “Algal biomass (mg/l)” in the left of each subgraph y-axis in Figure 4.

Line 207-210 Please cite the figure number of these data, such as Fig. 4.

Line 217-221 Please cite the figure number of these data, such as Fig. 4c for water temperature, and Fig. 4d for dissolved oxygen. Meanwhile, change “dissolved Oxygen” to “dissolved oxygen”.

Line 224-235 Please cite the figure number of these data, such as Fig. 5a for water N, Fig. 5b for water P.

Line 252 Please change “Dissolved Oxygen and Water transparency” to “dissolved oxygen and water transparency”.

Line 271 Please change “Nitrogen (mgl/)” to “Nitrogen (mg/l)” in Fig. 6a.

Line 331-352 Because water physico-chemical factors have influences on water algal biomass, which affect lesser flamingo abundance. To better understand the relationships among water environmental factors, algal biomass, and lesser flamingo abundance, structural equation model (SEM) might be used here.

Line 379-389 Please change “dissolved Oxygen” to “dissolved oxygen”.

Line 352-445 We would suggest to add the data of algal compositions, and their correlations with both water physico-chemical factors and lesser flamingo abundance. It might be more significance to calculate the tipping points (thresholds) of algal species abundance to the number of lesser flamingo.

Author Response

Dear reviewer,

First, I would like to appreciate your comments, with the good intention of improving our article for publication. The attached document contains responses to the comments.

Kind regards

Deogratias Lihepanyama

 

Author Response File: Author Response.docx

Reviewer 2 Report

In this manuscript, the authors monitored algal biomass changes and related water  physico-chemical variables for 12 consecutive months in the lakes Big Momella and Rishateni in 19 northern Tanzania. They also monitored lesser flamingo numbers and try to find out the relationship between lesser flamingo numbers and algal biomass which affected by physico-chemical variables. Overall, this study is interesting and the written is clear. The results is important for the protection of lesser flamingo. However, the main weakness of this manuscript is the lack of community identification of the algal variations. The algal biomass is quite high during Jan. and April, 2021. But there was a sharp decline of lesser flamingo numbers after Feb. 2021. This could not be explain just by algal biomass or algal blooms. I suggest the author to provide algal community variation data (investigation data by the authors or published data by other researches) in explain the changes of lesser flamingo numbers.

 

Other comments and suggestion:

1. Line 240: change “)” to “.”.

2. Figure 4: (1) the concentration of algal biomass in Figure 4a and Figure 4b are different from other sub-figures. Why? (2) the highest concentrations of N and P reached as high as about 12 mg/L and 4 mg/L? Are they right? Please check them? And the value of N and P should be mentioned in the main text. (3) Are the points of N, P, Temp, etc. represent mean values of each month? An error bar needs to be added into each point.

3. Figure 5: (1) please check the value of N and P; (2) please add error bar for each data point.

4. Line 322: The authors determined the tipping points (thresholds) using the non-linear curves. I don’t know how the non-linear curves can determine the tipping points. The authors need to provide the method of making non-linear curves, justify why the non-linear curves can determine the tipping points, and give appropriate citations at the section of “2.3. Data Analysis”.

5. Figure 9: It seems that the data of lesser flamingo abundance in April 2021 (please see Figure 8) has not been presented and analysed in Figure 9. Why? It need to be explained in the text.

6. “3.4. Physico-chemical Factors and Lesser Flamingo Abundance”: I don’t think this section is reasonable and needed. The physico-chemical parameters the author used are N, P, Temp, Oxygen, Transp. and pH. They are not the direct factor that could influence the abundance of lesser flamingo. Food, i.e., algal biomass is the main direct factor. Thus, I suggest the authors to delete this section as well as Table 2 and Table 3. In addition, the Discussion section of “4.4. Physico-chemical Factors and Lesser Flamingo Abundance” is redundant. The discuss of algal community reparations and toxicity could be inserted into section 4.3.

Author Response

Dear reviewer,

First, I appreciate the comments for improving our article for publication. The attached document contains the responses to the comments given.

Kind regards

Deogratias Lihepanyama

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

No more comments and suggestions.

Author Response

Dear Sir/Madam,

Thank you very much for your concern in reviewing our manuscript. I understand that you had no more comments/suggestions, but I have attached the responses again just to make the dialogue box for resubmission of the manuscript active.

Sorry for the inconvenience.

Kind regards

Author Response File: Author Response.docx

Reviewer 2 Report

The quality of the revised manuscript has improved distinctly. However, there are still some questions that need to be addressed.

1. Line 212: delete ")" at the end of this sentence.

2. Table B: the significance of "p" values should be italic.

3. My previous question "Figure 4: (1) the concentration of algal biomass in Figure 4a and Figure 4b are different from other sub-figures.": It seems that the question has not been addressed in the revised version. For example, the algal biomass in May in Fig. 4a and Fig. 4b is about 2.5 mg/L, but in Fig. 4c-4f, it is about 4.3 mg/L. This is inconsistent.

4. My previous question "Figure 9: It seems that the data of lesser flamingo abundance in April 2021 (please see Figure 8) has not been presented and analyzed in Figure 9 ": It seems that the data has not been presented in the revised figure yet.

 

Author Response

Dear Sir/Madam

Attached are the responses to the issues raised in the second round of comments. Many thanks for your time and concern.

Kind regards,

Deogratias

Author Response File: Author Response.docx