Understanding Nutrient Loads from Catchment and Eutrophication in a Salt Lagoon: The Mar Menor Case

Round 1

Reviewer 1 Report

The author undertook the calibration of various models to monitor changes in water quality (eutrophication) and successfully developed the daily algal growth model (Mmag). Through the monitoring of input flows, the author effectively predicted algal changes using the adopted measures. I find the results to be scientifically robust, and the models were well-calibrated. I have included some minor comments below for your consideration. Furthermore, I recommend that the authors consider a grammatical edit, as certain issues hinder a complete understanding of the paper.

Line 56. Since the nutrient proportions (N:P ratios) are important, it may be good for authors to list the N:P ratios of the flows as water quality parameters in the study.

 

Line 299. “due there isn´t phosphorus imitations in summer?” It is better to change a way of saying it.

 

 

I have included this in the overall comment. 

 

 

 

 

Author Response

The author undertook the calibration of various models to monitor changes in water quality (eutrophication) and successfully developed the daily algal growth model (Mmag). Through the monitoring of input flows, the author effectively predicted algal changes using the adopted measures. I find the results to be scientifically robust, and the models were well-calibrated. I have included some minor comments below for your consideration. Furthermore, I recommend that the authors consider a grammatical edit, as certain issues hinder a complete understanding of the paper.

 

Author want to express the thanks to the reviewer for your valuable comments that has improved the manuscript

A careful revision of the English was addressed in the manuscript

 

Line 56. Since the nutrient proportions (N:P ratios) are important, it may be good for authors to list the N:P ratios of the flows as water quality parameters in the study.

Response: N:P ratios are added in the document in the results discussion, as follows,

Considering only continuous annual external inputs to the lagoon the N:P ratio (= 287) is extremely high due to the large amount of nitrogen. If it is also included phosphorus loads during floods N:P ratio is reduced and varies from 30 to 130. However, when it is included the internal load of phosphorus from the sediment N:P ratio decreases to around 14. In all cases N:P ratio is more consistent with green algae presence in the MM.

Line 299. “due there isn´t phosphorus imitations in summer?” It is better to change a way of saying it.

Response: All the paragraph was rewritten in a better understanding way

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript with the title “Understanding nutrient loads from catchment and eutrophication in a salt lagoon, Mar Menor case” present a specialized mathematical MMag model to simulate algal growth in a Mar Menor lagoon. The Mar Mentor lagoon was suffering from algae blooms in recent years (specially 2019 and 2021). Extreme algal blooms cause biological decomposition of organic matter in lake bottom and reduces dissolved oxygen content and finally producing heavy mortalities to the flora and fauna. That is why it is necessary to prevent algae blooms bay identifying factors leading to it according to seasonal oscillations of parameters like temperature and nutrient availability in the lake. The authors elaborated a for Mar Mentor specialized MMag model and it was trained with real measurements from the past and it was proven to calculate values in good correlation to real lagoon performance (Fig. 6). Authors identified key risk parameters (NO3 input) which led to higher risk of algae blooms and proposed some reasonable countermeasures to prevent it in future. They also expanded the simulation it the future with shows significant alga bloom risk reduction if countermeasures are applied. The modelling of the Chl A content in the lake has a good correlation regarding oscillation intensity in comparison to real measurements. However, it is obvious that the real measurements have a constant delay of 2-3 month, with leads to a shift in model prediction. This can be led maybe for future prediction to a cumulative effect with an higher uncertainty of the result. Can this shift be explained for example theoretical assumptions regarding algae growth? Can the model be modified to correlate better regarding time? Nevertheless, I strongly recommend this manuscript for publication in water journal.

Author Response

The manuscript with the title “Understanding nutrient loads from catchment and eutrophication in a salt lagoon, Mar Menor case” present a specialized mathematical MMag model to simulate algal growth in a Mar Menor lagoon. The Mar Mentor lagoon was suffering from algae blooms in recent years (specially 2019 and 2021). Extreme algal blooms cause biological decomposition of organic matter in lake bottom and reduces dissolved oxygen content and finally producing heavy mortalities to the flora and fauna. That is why it is necessary to prevent algae blooms bay identifying factors leading to it according to seasonal oscillations of parameters like temperature and nutrient availability in the lake. The authors elaborated a for Mar Mentor specialized MMag model and it was trained with real measurements from the past and it was proven to calculate values in good correlation to real lagoon performance (Fig. 6). Authors identified key risk parameters (NO3 input) which led to higher risk of algae blooms and proposed some reasonable countermeasures to prevent it in future. They also expanded the simulation it the future with shows significant alga bloom risk reduction if countermeasures are applied. The modelling of the Chl A content in the lake has a good correlation regarding oscillation intensity in comparison to real measurements.

However, it is obvious that the real measurements have a constant delay of 2-3 month, with leads to a shift in model prediction. This can be led maybe for future prediction to a cumulative effect with an higher uncertainty of the result. Can this shift be explained for example theoretical assumptions regarding algae growth? Can the model be modified to correlate better regarding time? Nevertheless, I strongly recommend this manuscript for publication in water journal.

 

Author want to express the thanks to the reviewer for your valuable comments that has improved the manuscript

 

We thanks to the reviewer the idea of applying these models for prediction.

The purpose of both models developed and this research is to identify main factors that produce risk of appearance of algal blooms in the Mar Menor, but in this moment, these models are not prepared for short-term algal bloom prediction in the Mar Menor.

 

This sentence is added at the end of the introduction for better understanding.

so the main purpose of this research is to identify the key factors that produce algal blooms in the Mar Menor for help managers in formulating measures to reduce the risk of algal blooms.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript covers a fascinating topic – establishing a mathematical connection between nutrient loads generated in the catchment area and the eutrophication process in a coastal lagoon, especially algal blooms. Such an approach can only happen in well-studied systems such as Mar Menor coastal lagoon. However, there are several critical flaws that the author should take under consideration before this manuscript is published!

 

-I think the manuscript is written as a technical report; therefore, the results should be separated from the discussion for clarity. Noticeably, from 66 citation, the 53 have been cited in parts 1 (Introduction) and 2 (Study Case and Data).

-The connection (correlation) between the components of the lagoon MMag model should be better presented (mathematically) as supplementary material!

-All the model component parameters of Table 3 should be explained. Also, the terms filamentous, algae, deep species, and deep plants should be explained with examples! Significant: RGR=Relative Growth Rate, not Ratio!

-All the Latin names of species should be written in italics (in many cases in the text, lines 142-143, 245-246, 251, 287-288)

-Why so many times the term “Lake” is used when the case in the study is a coastal lagoon?

-The conclusion is too long! Several sentences should be transferred to discussion.

-The temperature tolerance data should not be based in only one paper! There are are several relevant publications that can be used.

-English should be considerably improved by a professional!

 

Specific comments

Line 115: Remove the point after the parenthesis.

Figure 4: Filamentous algae. Algal RGR!

Lines 254-256: The sentence needs clarification.

Line 283: Deep plant content! Please explain.

Line 239: filamentous seaweeds disappear!

Figures 4-8 legends: Capital letters at the beginning of the sentence and after separation a, b, c..

 

Figure 6: Density of filamentous and deep plants. Could you give more information on the Material and Methods?

-English should be considerably improved by a professional!

Author Response

This manuscript covers a fascinating topic – establishing a mathematical connection between nutrient loads generated in the catchment area and the eutrophication process in a coastal lagoon, especially algal blooms. Such an approach can only happen in well-studied systems such as Mar Menor coastal lagoon. However, there are several critical flaws that the author should take under consideration before this manuscript is published!

 

Author want to express the thanks to the reviewer for your valuable comments that has improved the manuscript

-I think the manuscript is written as a technical report; therefore, the results should be separated from the discussion for clarity. Noticeably, from 66 citation, the 53 have been cited in parts 1 (Introduction) and 2 (Study Case and Data).

Four more references are added in the discussion

 

-The connection (correlation) between the components of the lagoon MMag model should be better presented (mathematically) as supplementary material!

A supplementary material is added including connection and formulation between the components of the lagoon MMag.

 

-All the model component parameters of Table 3 should be explained. Also, the terms filamentous, algae, deep species, and deep plants should be explained with examples! Significant: RGR=Relative Growth Rate, not Ratio!

Al parameters of Table 3 are detailed described in the supplementary material

Examples of species are included in the paper

Filamentous algae: Chaetomorpha linum (cabello de angel in Spanish), Enteromorpha intestinalis (Ova marina in Spanish)

Deep plants in Mar Menor: Cymodocea nodosa (plant) and Caulerpa proligera (alga)

Algae: microscopic marine algae, phytoplankton

RGR, thanks for the clarification

 

-All the Latin names of species should be written in italics (in many cases in the text, lines 142-143, 245-246, 251, 287-288)

Response: all names was revised. Thank you for your comment

 

 

 

 

-Why so many times the term “Lake” is used when the case in the study is a coastal lagoon?

Response: many thanks for your comment and for improve the manuscript.

All the terms referred to lake are replaced by lagoon, unless correspond with a reference of a study of fresh water lake.

Thank you for remark the difference

Lagoons and lakes could be differentiated by which supports marine species in its waters. If it supports marine species, it is not cut off from the ocean, and it is a lagoon. If it only supports freshwater species, it is a lake.

 

 

-The conclusion is too long! Several sentences should be transferred to discussion.

Maybe conclusions are quite long but are focus on: chlorophyll levels associated with algal blooms risk, main nutrient inputs to the lagoon, main lagoon internal factors detected with the Mmag model, main nutrient components to reduce and measures to reach this.

So, respectfully, it is very difficult to reduce these conclusions

 

 

-The temperature tolerance data should not be based in only one paper! There are several relevant publications that can be used.

Four additional references are included. But the most important thing is not the temperature tolerance, model need the RGR curve for different temperatures.

We do not fine many studies that include this curve. We suggest the develop of more studies to obtain this curve and specifically for the Mar Menor species.

Next sentence is added in the manuscript,

“It is recommended to develop specific studies to determine RGR curves depending on water temperature and salinity for the Mar Menor deep water plants species.”

 

 

-English should be considerably improved by a professional!

English was carefully revised.

 

 

 

Specific comments

All specific comments are included

 

Line 115: Remove the point after the parenthesis.

Ok

 

Figure 4: Filamentous algae. Algal RGR!

ok

 

Lines 254-256: The sentence needs clarification.

The sentence was rewritten

 

Line 283: Deep plant content! Please explain.

It is replaced by Deep plants density (kg/m²)

 

Line 239: filamentous seaweeds disappear!

Thanks, this sentence was changed

 

Figures 4-8 legends: Capital letters at the beginning of the sentence and after separation a, b, c..

Done

 

Figure 6: Density of filamentous and deep plants. Could you give more information on the Material and Methods?

It is included the next paragraph at the end of material and Methods.

Intermediate results of the model are deep water plants density and filamentous algae density, both in kg/m², respectively indicate the amount of deep water plants in the soil and the quantity of filamentous algae in the water. The deep water plants density results are compared with observed data, amount of macrophytes, in the Mar Menor.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

No other suggestions!