Modeling Cyanotoxin Production, Fate, and Transport in Surface Water Bodies Using CE-QUAL-W2

Round 1

Reviewer 1 Report

Journal: Environments (ISSN 2076-3298)

Manuscript ID: environments-2398996

Type: Article

Title: Modeling Cyanotoxin Production, Fate, and Transport in Surface Waterbodies Using CE-QUAL-W2

 

This manuscript aimed to develop models for the transport and fate of cyanotoxins in surface waterbodies and to incorporate the models into the two-dimensional (longitudinal and vertical) hydrodynamic and water quality model CE-QUAL-W2. Also, the toxin models were incorporated into the CE-QUAL-W2 code and tested on a previously developed model of Henry Hagg Lake.

However, the presentation is not good. Only results of predicted models ae shown. What are the actual values? What is the reliability of the models? Please insert the data and some discussion. I have the following comments and suggestions for the authors to improve the quality of manuscript.

 

1. Section “1. Introduction”

Lines 34-37

“While all bacterial and algal blooms can have harmful effects on the environment by reducing the availability of oxygen in water bodies, cyanobacterial blooms can also be harmful due to their ability to produce cyanotoxins, exposure to which may cause illnesses in humans [1,4,5].”

Please read and insert the following reference.

Challenges of using blooms of Microcystis spp. in animal feeds: A comprehensive review of nutritional, toxicological and microbial health evaluation. https://doi.org/10.1016/j.scitotenv.2020.142319

2. Line 52

“Arthrospira fusiformis” should be italic. The Latin names of cyanobacterial species should be italic. Please check the entire manuscript, including tables and figures.

3. Table 3

“Ratio of Toxin to Chlorophyll a (ug toxin ug-1 chl a)”

Please check the Greek letter μ (mu), not u.

4. Table 3

The Latin names of cyanobacterial species should be italic.

5. Table 6

Please present full names of CTP, CTB, CTR and CTD.

6. Figures 2-5

What are groups 1-3? Not clear. Please insert the descriptions in the revised manuscript.

7. Figures 6, 7

Why only data of scenario 3 are shown? What about scenario 1, 2 and 4? Please insert the data.

8. Only results of predicted models ae shown. What are the actual values? What is the reliability of the models? Please insert the data and some discussion.

ok

Author Response

#	Reviewer 1 Comments	Response
1	This manuscript aimed to develop models for the transport and fate of cyanotoxins in surface waterbodies and to incorporate the models into the two-dimensional (longitudinal and vertical) hydrodynamic and water quality model CE-QUAL-W2. Also, the toxin models were incorporated into the CE-QUAL-W2 code and tested on a previously developed model of Henry Hagg Lake.   However, the presentation is not good. Only results of predicted models ae shown. What are the actual values? What is the reliability of the models? Please insert the data and some discussion. I have the following comments and suggestions for the authors to improve the quality of manuscript.	Thank you for reviewing our paper and providing feedback. The study lake only had a few values of cyanotoxin to compare and the model was within the range of those data as reported in the paper. But the primary effort here was to present a modeling approach to the problem of cyanotoxins in waterbodies since there are more and more cases of cyanotoxins violating water quality criteria for toxicity throughout the world. We have responded to your comments further below.
2	Section “1. Introduction” Lines 34-37 “While all bacterial and algal blooms can have harmful effects on the environment by reducing the availability of oxygen in water bodies, cyanobacterial blooms can also be harmful due to their ability to produce cyanotoxins, exposure to which may cause illnesses in humans [1,4,5].” Please read and insert the following reference. Challenges of using blooms of Microcystis spp. in animal feeds: A comprehensive review of nutritional, toxicological and microbial health evaluation. https://doi.org/10.1016/j.scitotenv.2020.142319	Thank you for the reference. We enjoyed reading the article. But the conclusion of the paper is not aligned to our discussion of cyanotoxins specifically. The conclusion was: “Microcystis spp., including M. aeruginosa, are rich in protein and have been suggested as a source of protein in animal feeds. However, in addition to protein, Microcystis spp. need to be considered as sources of a wider range of nutrients and metabolites including nutritionally beneficial components but also as animal and human health hazards.” Since this paper is about using the cyanobacteria as animal feed and effects of the bacterium, we did not agree with the reviewer about including this reference in our paper focused only on the cyanotoxin itself.
3	Line 52 “Arthrospira fusiformis” should be italic. The Latin names of cyanobacterial species should be italic. Please check the entire manuscript, including tables and figures.	Latin names have been italicized.
4	3.      Table 3 “Ratio of Toxin to Chlorophyll a (ug toxin ug-1 chl a)” Please check the Greek letter μ (mu), not u.	Changed to μ (mu).
5	Table 3 The Latin names of cyanobacterial species should be italic.	Latin names have been italicized.
6	Table 6 Please present full names of CTP, CTB, CTR and CTD.	Full names listed.
7	Figures 2-5 What are groups 1-3? Not clear. Please insert the descriptions in the revised manuscript.	Expanded on group names in the text and added descriptions to figure captions.
8	Figures 6, 7 Why only data of scenario 3 are shown? What about scenario 1, 2 and 4? Please insert the data.	Only results of scenario three were shown since this is a representative scenario of toxin production. Text was included before table 6 regarding this: "The third scenario was chosen as a representative model that would likely be used in further applications of the CE-QUAL-W2 model, and additional results are provided for this scenario..." We feel that if we present results for the other three scenarios it will clutter up the report.
9	Only results of predicted models ae shown. What are the actual values? What is the reliability of the models? Please insert the data and some discussion.	There were very limited toxin data available at the lake and so the goal of this paper was to present proof of concept of the models more than verification of their ability to predict actual concentrations. A paragraph regarding the few toxin data available at the lake was included at the end of the discussion: "Toxin data were available at Henry Hagg Lake in spring 2019..."

Reviewer 2 Report

The manuscript is rather theoretical (mathematical) in nature. There is no analysis of environmental parameters. The objectives of this research were to develop a general framework to model cyanotoxin production, distribution, and degradation in surface waterbodies that could be incorporated into CE-QUAL-W2. However, the authors did not make any verification of the proposed models for the transport and fate of cyanotoxins in surface waterbodies. There are only a few references to literary sources. I do not think that this article will be of interest to a wide range of readers of the journal Environments.

Author Response

	Reviewer 2 Comments	Response
1	The manuscript is rather theoretical (mathematical) in nature. There is no analysis of environmental parameters. The objectives of this research were to develop a general framework to model cyanotoxin production, distribution, and degradation in surface waterbodies that could be incorporated into CE-QUAL-W2. However, the authors did not make any verification of the proposed models for the transport and fate of cyanotoxins in surface waterbodies. There are only a few references to literary sources. I do not think that this article will be of interest to a wide range of readers of the journal Environments.	Thank you for your comments. We expect that with use of the model in the future, there will be more options for finding lakes/reservoirs that have sufficient data: flow rates in and out, temperature, water quality, and cyanotoxin data. The primary effort here was to present a modeling approach to the problem of cyanotoxins in waterbodies since there are more and more cases of cyanotoxins violating water quality criteria for toxicity throughout the world.

Reviewer 3 Report

 The research was well reported but I have a few clarification requirements as outlined below:

Line 77- at the end of the introduction, the model CE-QUAL-W2 was introduced without any details, only refs 25-26. Please detail here what was the water body used as a model for the development of CE-QUAL-W2 algorithm. Was it the same as the one used here: the Henry Hagg Lake (lines 170-172)? Can it be applied to which type of water bodies? Only for temperate regions? Others?

Line 170- the model was calibrated for which years? Were the same ones used here (2013-2014?)?

Figures 2-7. The x-axis titles were not provided. It is not clear to me which is ‘1/1/13’ (The USA dates usually are not written in the order of day-month-year). The authors do not detail to which timeframe the simulation was prepared. On a scale of weeks, months or years? The word ‘annual’ never appears in the text. It seems two years were calculated. Why those two years?

Author Response

	Reviewer 3 Comments	Response
11	The research was well reported but I have a few clarification requirements as outlined below:	Thank you for providing useful comments to improve the quality of the paper.
12	Line 77- at the end of the introduction, the model CE-QUAL-W2 was introduced without any details, only refs 25-26. Please detail here what was the water body used as a model for the development of CE-QUAL-W2 algorithm. Was it the same as the one used here: the Henry Hagg Lake (lines 170-172)? Can it be applied to which type of water bodies? Only for temperate regions? Others?	Added description of CE-QUAL-W2 model in introduction.
13	Line 170- the model was calibrated for which years? Were the same ones used here (2013-2014?)?	Added description of model calibration and simulation period.
14	Figures 2-7. The x-axis titles were not provided. It is not clear to me which is ‘1/1/13’ (The USA dates usually are not written in the order of day-month-year). The authors do not detail to which timeframe the simulation was prepared. On a scale of weeks, months or years? The word ‘annual’ never appears in the text. It seems two years were calculated. Why those two years?	The x-axis labels on Figure 2-7 have been adjusted to show the full date. Added description in text of model simulation period and reason for choosing two years to present results.

Round 2

Reviewer 1 Report

Journal: Environments (ISSN 2076-3298)

Manuscript ID: environments-2398996-peer-review-v2

Type: Article

Title: Modeling Cyanotoxin Production, Fate, and Transport in Surface Waterbodies Using CE-QUAL-W2

 

This manuscript aimed to develop models for the transport and fate of cyanotoxins in surface waterbodies and to incorporate the models into the two-dimensional (longitudinal and vertical) hydrodynamic and water quality model CE-QUAL-W2. Also, the toxin models were incorporated into the CE-QUAL-W2 code and tested on a previously developed model of Henry Hagg Lake.

 

The manuscript improved during the revision. However, there are still some issues need to be addressed. I have the following comments and suggestions for the authors to improve the quality of manuscript.

 

1. Section “1. Introduction”

Lines 31-34

“Cyanobacteria are found throughout the world in both fresh and marine water, and since warmer temperatures have been shown to increase cyanobacterial growth, the occurrence of cyanobacteria could likely increase with the rise in global temperatures brought about through climate change [1–3].”

The references 1-3 are too old. Please cite the following reference.

Challenges of using blooms of Microcystis spp. in animal feeds: A comprehensive review of nutritional, toxicological and microbial health evaluation. https://doi.org/10.1016/j.scitotenv.2020.142319

This comprehensive paper is not only about animal feed, but also have many basic information about cyanobacteria and cyanotoxins.

2. Table 3

“Percent Extracellular”

Not clear. Please rephrase it in the revised manuscript.

3. I am confused by CTP, CTB, CTR and CTD. Definitions and full names of CTP, CTB, CTR and CTD are not clear. How abbreviations of CTP, CTB, CTR and CTD come from? Please insert detailed descriptions in the manuscript.

4. Please read and carefully check through all the manuscript text, tables and figures. It is the authors’ responsibility to present their best work to the readers.

minor

Author Response

The comments from Reviewer #1 were: 

1. Section “1. Introduction”

Lines 31-34

“Cyanobacteria are found throughout the world in both fresh and marine water, and since warmer temperatures have been shown to increase cyanobacterial growth, the occurrence of cyanobacteria could likely increase with the rise in global temperatures brought about through climate change [1–3].”

The references 1-3 are too old. Please cite the following reference.

Challenges of using blooms of Microcystis spp. in animal feeds: A comprehensive review of nutritional, toxicological and microbial health evaluation. https://doi.org/10.1016/j.scitotenv.2020.142319

This comprehensive paper is not only about animal feed, but also have many basic information about cyanobacteria and cyanotoxins.

2. Table 3

“Percent Extracellular”

Not clear. Please rephrase it in the revised manuscript.

3. I am confused by CTP, CTB, CTR and CTD. Definitions and full names of CTP, CTB, CTR and CTD are not clear. How abbreviations of CTP, CTB, CTR and CTD come from? Please insert detailed descriptions in the manuscript.
4. Please read and carefully check through all the manuscript text, tables and figures. It is the authors’ responsibility to present their best work to the readers.

Here are the responses to each suggestion:

1. Thank you for the comment about the paper citation. We do not feel that a good citation can be ‘old’. But the import of the paper you mention is not in the context of our modeling study. We agree though that it provides some information on overall toxicity and will include it.
2. Revised
3. Revised abbreviations with added context
4. Will do, thanks!

Reviewer 2 Report

The authors have significantly improved the manuscript. Now the article can be published in the journal Environments.

Author Response

Thank you for your help in reviewing our paper! No response required.