Phycoremediation as a Strategy for the Recovery of Marsh and Wetland with Potential in Colombia

Round 1

Reviewer 1 Report

The review article is very well written and extremely rich in information, it addresses a topic of great interest both for environmental policies and even for public health. The publication of the paper will be of great relevance to the academic community, especially in the area of ​​environmental biology.

Author Response

We appreciate your review very much.

Reviewer 2 Report

Dear Authors,

the manuscript is very interesting and deals with phytoremediation and bioremediation, however it should be enriched by highlighting the following points:

1- Biodegradation allows to degrade pollutants but molecules of interest are not always obtained (eg lipids, sugars, etc.), in other cases the degradation products maintain their toxicity;

2- The presence of microalgae can determine risks of hypoxia or can release toxins and mucilages in the waters and therefore, if the growth is uncontrolled, it can cause serious alterations of the ecosystems in particular of the restricted ones;

3-The possibility of creating bioreactors with microalgae, fungi or bacteria for bioremediation activities should be highlighted;

4-The work should be enriched with degradation schemes in order to highlight the degradation of dangerous compounds such as PAHs.

5-The degradative activity of fungi such as Trichoderma spp, Plerotus ostreatus etc. should be highlighted more.

Best regards 

Author Response

Response to Reviewer 2 Comments

Point 1:  Biodegradation allows to degrade pollutants but molecules of interest are not always obtained (eg lipids, sugars, etc.), in other cases the degradation products maintain their toxicity

Response 1: The document added that to solve this problem, associate the cultivation of microalgae with bacteria or a consortium of microalgae, however, if toxicity is still maintained, it is best to extract the biomass, because it is generally immobilized in the biomass.

Point 2: The presence of microalgae can determine risks of hypoxia or can release toxins and mucilages in the waters and therefore, if the growth is uncontrolled, it can cause serious alterations of the ecosystems in particular of the restricted ones;

Response 2: To avoid bloom, mixed cultures of microalgae with bacteria are suggested, which have the ability to control the growth of microalgae. This information was added to the document.

Point 3: The possibility of creating bioreactors with microalgae, fungi or bacteria for bioremediation activities should be highlighted;

Response 3: the suggestion was considered, however, the cultivation system for the recovery of large areas is mentioned.

Point 4: The work should be enriched with degradation schemes in order to highlight the degradation of dangerous compounds such as PAHs.

Response 4: The suggestion was considered and is modified in the manuscript. Changes were underlined.

Point 5: The degradative activity of fungi such as Trichoderma spp, Plerotus ostreatus etc. should be highlighted more.

Response 5: We consider that it is not pertinent, since the review is about microalgae, however, we mentioned that some fungi have a better degradation capacity.

Reviewer 3 Report

The work presents an interesting compendium of information on the application of microalgae for the elimination of contaminants in aqueous bodies, taking Colombia as a case study. Unfortunately, this reviewer does not find the novelty and scientific contribution in the work, which seems to be written more as a book chapter than as a review article for a scientific journal. Although the objective is described, it is not clear if there is any research question or hypothesis to be solved, so that the work detects the limitations or gaps that need to be addressed to improve this technology. It is also not clear why the study is focused on Colombia, how the study model can contribute to the rest of the cases in the world, or why Colombia is a special case that should be studied independently from the rest? 

Author Response

We appreciate your review very much. Your considerations were taken into account, some issues of how the methodologies for recovering bodies of water were included. Colombia is rich in freshwater; however, many of these bodies of water are contaminated, making the general population vulnerable. Perhaps in a small country, and with that diversity, it can be used as a pilot to recover large bodies of water to later scale and take it to larger countries with similar problems, such as India or China. For this reason, Colombia was taken as an example.

Reviewer 4 Report

The manuscript ID resources-1498881 deals with a very interesting and perspective topic, which is the protection of water resources through the use of phycoremediation techniques. The use of microalgae in environmental protection and engineering technologies is gaining more and more importance, and the reviewed review is in line with these global trends. The manuscript is well written and the layout is correct and logical. The authors have actually separated the chapters. In my opinion, this is a fairly well-read study. It fully corresponds to the profile of the Resources journal. In my opinion, however  the authors omit many aspects of phytoremediation, which makes the manuscript incomplete, and I believe it should be expanded and supplemented.

The abilities of microalgae and phytoplankton related to the removal of heavy metals, pesticides, and biogenic compounds, as well as limiting the amount of bacteria are well known. It is not surprising, therefore, the idea to use these features in phytoremediation processes in contaminated water bodies. However, many questions and doubts about this approach arise, which should be clarified in the manuscript. My critical remarks below:

1. Please explain in manuscript how to permanently remove the pollutants from natural water bodies bound by algae biomass, because only then will the phycoremediation be effective?
2. Please describe and present the available technologies and methods of phytoremediation of water reservoirs. Should the biomass of specialized species of microalgae inhabit polluted waters, or would the purification processes take place in separate, separated tanks, reactors, photobioreactors, and fully controlled installations? Perhaps, before the end of the growing season, the biomass of microalgae inhabiting the remediated water bodies should be harvested?
3. Please explain in the manuscript the risk of recontamination of tanks after the end of the growing season and the death of phytoplankton cells (or macroalgae). The pollutants then return to the trophogenic zone, and the dead biomass (organic matter) consumes oxygen and intensifies the processes of degradation of water reservoirs. A comparison of the strengths and weaknesses of technologies based on the use of microalgae biomass, including the impact on natural ecosystems, is presented in the paper: https://0-doi-org.brum.beds.ac.uk/10.3390/su12239980
4. In my opinion, describing only the skills of microalgae and indicating their potential for application is not enough, one should also describe specific methods and solutions for this type of protection of water resources.
5. The authors should indicate the strengths and weaknesses of this solution.

Author Response

We appreciate your review very much. Your considerations were taken into account; the article you provided to us was very enriching; all the observations made were included in the document, such as the elimination or obtaining of biomass, production technologies. However, the article is more focused on bioremediation, risks of microalgae blooms and their control; above all, the disadvantages of the cultivation and use of microalgae from or obtained from contaminated environments

Response to Reviewer 4 Comments

Point 1. Please explain in manuscript how to permanently remove the pollutants from natural water bodies bound by algae biomass, because only then will the phycoremediation be effective?

Response 1: The suggestion was considered and is modified in the manuscript. Changes were underlined.

Point 2. Please describe and present the available technologies and methods of phytoremediation of water reservoirs. Should the biomass of specialized species of microalgae inhabit polluted waters, or would the purification processes take place in separate, separated tanks, reactors, photobioreactors, and fully controlled installations? Perhaps, before the end of the growing season, the biomass of microalgae inhabiting the remediated water bodies should be harvested?

Response 2: The suggestion was considered and is modified in the manuscript. Changes were underlined.

Point 3. Please explain in the manuscript the risk of recontamination of tanks after the end of the growing season and the death of phytoplankton cells (or macroalgae). The pollutants then return to the trophogenic zone, and the dead biomass (organic matter) consumes oxygen and intensifies the processes of degradation of water reservoirs. A comparison of the strengths and weaknesses of technologies based on the use of microalgae biomass, including the impact on natural ecosystems, is presented in the paper: https://0-doi-org.brum.beds.ac.uk/10.3390/su12239980

Response 3: the document suggested by you was of great help, it mentions methodologies to control the uncontrolled growth of microalgae.

Point 4. In my opinion, describing only the skills of microalgae and indicating their potential for application is not enough, one should also describe specific methods and solutions for this type of protection of water resources.

Response 4: The suggestion was considered and is modified in the manuscript. Changes were underlined.

Point 5. The authors should indicate the strengths and weaknesses of this solution.

Response 5: The suggestion was considered and is modified in the manuscript. Changes were underlined.

Round 2

Reviewer 3 Report

The manuscript  Phycoremediation as a Strategy for the Recovery of Bodies of Water: The Colombian Approach presents an improved version; however, the main observation made has not been satisfactorily met. The present version maintains only a minimal section on studies in Colombia, section 5 page 16. So, there is no reason to include Colombia as a case study. Throughout the text, results of recently reported work on the application of the technology in the removal of various pollutants are summarized. The text is well described and includes basic information for the first readers, however, it lacks the description of the basic principles necessary for the development and implementation of the technology, highlighting the knowledge gaps that must be addressed for its eventual application.  

There are subsections that do not really contribute to the writing, such as section 3.2, where only one related reference is mentioned, while the rest of the text is a description of the problem (perhaps the authors forgot to write the references, page 13, line 85). 

Author Response

We appreciate your review very much. 

Response to Reviewer 3 Comments

Point 1: 

The manuscript  Phycoremediation as a Strategy for the Recovery of Bodies of Water: The Colombian Approach presents an improved version; however, the main observation made has not been satisfactorily met. The present version maintains only a minimal section on studies in Colombia, section 5 page 16. So, there is no reason to include Colombia as a case study. Throughout the text, results of recently reported work on the application of the technology in the removal of various pollutants are summarized. The text is well described and includes basic information for the first readers, however, it lacks the description of the basic principles necessary for the development and implementation of the technology, highlighting the knowledge gaps that must be addressed for its eventual application. 

Response 1: Clearly Colombia is a country that has little technological development in this regard, investigations related to isolation, identification and use of microalgae are incipient, therefore the little information presented in the review, however, we are a group that is incurring in this field, and we want to take microalgae studies a step forward, not only isolating and characterizing, but also using as bioremediation tools in bodies of water. Despite the fact that Colombia is considered one of the richest countries in Renewable Internal Freshwater Resources (https://www.fao.org/3/y4473e/y4473e0g.gif), the quality of the water of the population in general is deficient (from the microbiological and chemical point of view), for that reason, the interest of us to give a point of view from Colombia, of the problem of water, and the use of microalgae as a final tool for the treatment of water bodies

Point 2: There are subsections that do not really contribute to the writing, such as section 3.2, where only one related reference is mentioned, while the rest of the text is a description of the problem (perhaps the authors forgot to write the references, page 13, line 85). 

Response 2: In the subsection of degradation of pesticides, the information on the mechanism was expanded, and it was mentioned that the mechanism of degradation is very similar to the mechanism of degradation of antibiotics, so in the subsection that you mention, we did not expand so as not to be repetitive. The reference is on page 13 line 91

Reviewer 4 Report

Thanks a lot for Authors for improving manuscript. In may opinion manuscript can be publish in current form. 

Author Response

Thank you very much for your initial comments and for your review.

Round 3

Reviewer 3 Report

After reading several times, and asking the authors for argumentation about the Colombian approach, I do not find the manuscript strong enough to explain to the readership what the Colombian approach is. Therefore, the manuscript does not fulfill the scientific information described in the title,  abstract, and introduction; it is not clear what the new information reported is.

Author Response

Thank you very much for your comments and thorough review.