Assessment of Leachate Generated by Sargassum spp. in the Mexican Caribbean: Part 2, Mobility of Metals

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I am writing regarding the manuscript titled “Assessment of Leachate Generated by Sargassum spp. in the Mexican Caribbean: Part 2 - Mobility of Metals,” submitted for potential publication in Water.

The study is highly relevant due to the urgent need to assess the environmental impact of the substantial sargassum biomass that has been accumulating on the coasts of Mexico, the United States, and various Caribbean nations. The decomposition of sargassum can release potentially hazardous elements, which may lead to contamination of marine and coastal ecosystems, including karstic aquifers. Thus, the research presented is important.

However, there are several concerns regarding the methodology and the comparative results from different sampling sites in the leaching experiments conducted in the laboratory. 

The manuscript does not detail the method used for analyzing trace elements in seawater. It is unclear whether the presence of major ions in seawater and potentially in leachates interferes with the trace element analysis in both liquid matrices.

There is an error in the representation of the aluminum symbol; it is incorrectly denoted as “AL,” which could be confused with the site “AL.”

Some figure legends are written in Spanish, which needs to be corrected to ensure consistency throughout the manuscript.

The manuscript incorrectly describes the conversion of sulfates to sulfides as an oxidation reaction; it is, in fact, a reduction reaction.

 

Discussions and Conclusions

The results indicate a negligible presence of certain potentially toxic elements, such as lead (Pb) and cadmium (Cd), as well as elements of biological significance, including manganese (Mn), zinc (Zn), and iron (Fe), in the leachate. These findings prompt a critical evaluation of the underlying factors contributing to the low concentrations observed.

It is recommended that further analyses be conducted to quantify the amounts of these metals potentially released per kilogram or ton of decomposed sargassum. Such estimates would provide a clearer understanding of the potential environmental impact.

The current conclusions lack specificity regarding the implications of these results. To strengthen the discussion, it is essential to highlight the significance of these findings more explicitly, emphasizing their relevance to environmental pollution and public health.

Comments on the Quality of English Language

PLEASE REVIEWE THE COMPLETE TEXT

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Leal-Bautista et al presented the case of 'ASSESSMENT OF LEACHETE GENERATED BY SARGAS- 2 SUM SPP AT THE MEXICAN CARIBE: part 2 mobility of metals'. I have gone through the manuscript critically. This is very interesting study, but have some issues, those need careful attention by author, before it is considered for publication. I recommend 'Reject' for this communication in its present form. But by considering the unique topic they have attempted the study, they are encouraged to resubmit the paper as fresh communication, but only after addressing my comments.   

Special comment :

English through-out the manuscript is poor and needs substantial improvement. Authors can take the help of native speaker or professional services.   

Major comments: 

1. The introduction part is not very clear, there are several instances of using long sentences e.g. 'Several references have indicated that sargassum (Sargassum spp.) is porous and easily permeable to cationic species (10, 11) thus, the presence of metals is possible due to the process of biosorption of cations, due to the high content of carboxylic groups and alginate contained in Sargassum (12, 13).' Please rephrase, this to convey the clear meaning.

2. I suggest authors to start with issue of algal times, then go and describe specifically regarding brown tide - with specific reference to Sargassum bloom.  Please give some empirical numbers regarding the extent of biomass that is being generated each year - global scenario, followed by the economic burden it causes. This will give the idea of extent of problem. There are several recent reviews and publications giving this information. Including this all make your study more relevant to scientific community. 

3. Authors stated that 'The collection of sargassum samples was carried out in two periods: from September 17 to 24, 2020, and in April and May 2021 in the northern area of the Mexican Caribbean  coast, including fresh and residual collection areas (Figure 1)' does this coincides with bloom period?

4.  It was stated that 'From the methodology described in (17)' please provide detailed methodology, kindly remember that all readers might not have access to the paper you cited. 

5. Authors have stated S. natans and S. fluitans samples were used, how they have identified the species, the taxonomy of this genus if very confusing, please provide reference.

6. Authors have stated that they have used consortium, of what species?

7. Please indicate where Leachate collector design assembly was kept and under what conditions?  

8.  It was stated that 'For this purpose, reagent type I water was used. The volume of water used was based on the average rainfall of the collection months from the last ten years in the state of Quintana Roo. Please indicate what is type I water.  Please also indicate what is the volume of the water used, it can not be simply last ten years? Remember this is scientific paper and all the relevant information needs to be provided. 

9. Although water quantity for obtaining leachates from dry sample is pnot provided, this reviewer believes that it is different than the water  use for extraction of leachates from fresh sample, how once can expect that the further data / experiments/ results of heavy metals are comparable?   

10. 'It was decided to determine the presence and concentration of heavy metals in sargassum as tissue, and in a sample of water collected from those that correspond to fresh, to define if any of these elements are present in the leachate generated; therefore, there is a concentration of PM in seawater, tissue and leachate.' This is extremely confusing statement, what do you want to say, please revise. 

11.  It was stated that 'Water samples will be collected as directed by (23) regarding containers, quantity, and preservation. All samples for water analysis are filtered using a 0.45 μm pore size nitrocellulose membrane'. In the material method section the term 'will be' / 'are' should not come, it should be only past tense. Please correct through out the manuscript. 

12.  It was stated ' the concentrations of nitrites (NO₂⁻/L), nitrates (N-NO3-), and total or- 134 thophosphates were evaluated' what is the purpose of these analysis, please elaborate regarding their relevance to the present study.

13. Why following metals and metalloids Arsenic, Boron, Iron, Zinc, Manganese, Cadmium, Lead, Aluminum, Nickel and Copper were chosen in the present study.

14. Why standards were not used / if used why not mentioned? This is extremely important because in ICP-OES, heavy metal data should be always correlated / corroborated with standard heavy metals, in absence of it results are not considered authentic in scientific studies. 

15. Authors have not mentioned how many replicates they have used, I have not seen any standard deviation or standard error as well in results section.  Without that based on single collection and analysis how such important study is valid. 

16.  In table 4; Presence of metals in Sargassum spp. and in the processes of leachate generation per se and by percolation. Data for each metal needs to be given and not only highest and lowest values, please revise accordingly.

17.  The expression of data for metals, mg/L is alright, but as I stated before, your volume of water used in dry and fresh feedstock is different , it is better to covert the data to per gram of sargassum feedstock in dry weight for uniformity.  Or re-do the study with equal volume of water.   

18. Discussion is very poor and more than half is their results,  there is comparison with municipal municipal solid waste. My point of view is this comparison is alright, but there are several studies available on seaweeds authors are encouraged to use those. 

19. Authors need to explain the limitations of this study.   

 

Minor comments: 

1. Term 'sargassum' should always have first letter Caps and entire word italics, please follow this through-out the manuscript.  

2. Please provide the latitude and longitude of the collection locations.

3.  It is stated that 'The AL collection was carried out 19-6 Km away from the coast in  front of the municipality of Benito Juárez and Isla Mujeres'. What do you mean by 'AL' please define the abbreviation when first used.

4.  It was stated that ' water samples were collected as indicated by the AWWA'. What do you mean by 'AWWA' please define the abbreviation when first used.  

5. Term LDM low detection method  should be replaced with BDL - Below detectable level.  

5.  It was stated that 'pH, Salinity and Temperature readings were taken using conductronic 18 field probe'. Please provide model and company name of the instrument used.

 

Comments on the Quality of English Language

Extensive editing of English language required.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have revised the manuscript in light of comments provided by me and also given a rebuttal. In view of this, the revised version may be accepted for publication. Nevertheless, there are still few standard English language errors e.g. the discussion starts with "The results obtained in this work are consistent with the values reported by other authors in metal sorption and transport" It is pertinent that all the statements in the results and discussion need to be in past tense. I am sure editorial team will take care of this during proof reading.  

Comments on the Quality of English Language

There are still few standard English language errors e.g. the discussion starts with "The results obtained in this work are consistent with the values reported by other authors in metal sorption and transport" It is pertinent that all the statements in the results and discussion need to be in past tense. I am sure editorial team will take care of this during proof reading.