Characterization of Microplastics and Mesoplastics and Presence of Biofilms, Collected in the Gualí Wetland Cundinamarca, Colombia
and Luis David Gómez-Méndez 5,*
Round 1
Reviewer 1 Report
This study has reported the qualitative and quantitative findings on the characterization of different types of plastics in a wetland ecosystem. Overall, this manuscript needs improvement in many sections to increase the overall quality as well as readers understanding of the reported results and discussion. The detailed comments are appended below.
Abstract
Abstract can be improved by providing the key quantitative data as well as a statement at the end on the important implication of this work.
Keywords. They should be re-arranged in a proper order of logic. For example, the first keyword “Biofilms” which is not the main focus of this work.
Introduction:
Provide some quantitative information from literature on the abundance and distribution of microplastics in wetland or similar nature-based systems.
Clearly highlight the novelty and importance of this study with respect to exiting knowledge in literature.
Line 33: Change “According to [1],” to “According to a report [1],”
Section 2.1: Could you provide more information about water sampling, i.e., are water samples collected from the surface or at a certain depth from the surface.
Line 99 – 100: The word “according” is repeated. Rewrite the sentence for better readability.
Line 109: Change “Biofilm detection was performed according to [23] modified.” to “Biofilm detection was performed according to the modified method published previously [23]”. Just adding reference in the mid of a sentence does not convey the message clearly.
Figure 1: Improve the picture quality with increase of resolution as well as the text font.
Figure 9: Are the five samples of plastisphere from the three sampling points? Mention in the figure legend or in the text.
The discussion section can be strengthened by comparing the concentration of various types of plastics observed in this study with published studies on wetland systems.
Provide some discussion of the changes of microplastic concentration and their characteristics with the changes of season (rainy vs. dry season) since authors have reported that two samplings were done in rainy season and one in dry weather.
At the end of the discussion, develop a paragraph on the implications and limitations of this work.
Concussions: It is too brief, thus need to be expanded by highlighting the major findings and observations.
Authors are encouraged to include in their manuscript the key water quality data of the wetland if available.
Several studies have indicated that microplastics are the vector for various environmental pollutants including heavy metals. Authors are suggested to do analysis of the presence of inorganic or organic contaminants on the surface of microplastics in future works.
This manuscript needs minor English editing.
Author Response
- Abstract can be improved by providing the key quantitative data as well as a statement at the end on the important implication of this work.
R/ Done Lines 79 – 84.
- They should be re-arranged in a proper order of logic. For example, the first keyword “Biofilms” which is not the main focus of this work.
R/ The order was changed.
- Provide some quantitative information from literature on the abundance and distribution of microplastics in wetland or similar nature-based systems.
R /Done, discussion (section)
- Clearly highlight the novelty and importance of this study with respect to exiting knowledge in literature.
R/ Done. Lines 42-48
- Line 33: Change “According to [1],” to “According to a report [1],”
R/ Done
- Section 2.1: Could you provide more information about water sampling, i.e., are water samples collected from the surface or at a certain depth from the surface.
R/ Done. Lines 107-109 (section 2.1)
- Line 99 – 100: The word “according” is repeated. Rewrite the sentence for better readability.
R/ Done
- Line 109: Change “Biofilm detection was performed according to [23] modified.” to “Biofilm detection was performed according to the modified method published previously [23]”. Just adding reference in the mid of a sentence does not convey the message clearly.
R/ Done
- Figure 1: Improve the picture quality with increase of resolution as well as the text font.
R/ The map was improved.
- Figure 9: Are the five samples of plastisphere from the three sampling points? Mention in the figure legend or in the text.
R/ Done in legend.
- The discussion section can be strengthened by comparing the concentration of various types of plastics observed in this study with published studies on wetland systems.
R/ Done. Lines 216-222
- Provide some discussion of the changes of microplastic concentration and their characteristics with the changes of season (rainy vs. dry season) since authors have reported that two samplings were done in rainy season and one in dry weather.
R/ Done. Lines 295-306
- At the end of the discussion, develop a paragraph on the implications and limitations of this work.
- Conclussions: It is too brief, thus need to be expanded by highlighting the major findings and observations.
R/ Done
- Authors are encouraged to include in their manuscript the key water quality data of the wetland if available.
R / Data not available
- Several studies have indicated that microplastics are the vector for various environmental pollutants including heavy metals. Authors are suggested to do analysis of the presence of inorganic or organic contaminants on the surface of microplastics in future work.
R/ thank you for your suggestion.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In my opinion, the article “Characterization of micro-meso plastics and presence of biofilms, collected in the Gualí wetland Cundinamarca, Colombia” submitted to Journal of Microplastics by Porras-Rojas et al. poses an interesting contribution to the research field focusing on microplastic pollution in the wetland. The authors characterized microplastics, mesoplastics and macroplastics in a wetland and discovered the presence of biofilms on these plastic particles. The sampling, sample processing and final analysis were conducted with care and the monitoring results are interesting.
Nonetheless, I still have serval questions and comments regarding the sample preparation but also the data analysis. Only in the case of clarification and explanation of certain essential aspects/parts of the manuscript, I would recommend the article for publication in Microplastics.
Major:
1. L 24, I do not find any SEM evidence regarding the presence of diatoms on the surface of microplastics in the section of Discussion.
2. The authors do not summarize the studies on microplastics in wetlands and state why it is necessary to characterize plastic particles in this wetland.
3. L 90-96, sampling procedure should be stated more clearly. How did authors use tweezers to transfer MPs that were down to 25 microns to the tubes as small MPs were not visible via eyes?
4. What were the criteria for selecting MPs from the mesh sieves during sampling campaigns?
5. L 98-99, were the MPs filtered onto filters for optical observation? Please add some details here.
6. L 100-101, was the major dimension of MPs reported in this study?
Minor:
1. L 33-35, the authors missed one of the quotation marks.
2. L 51, “…presence of microplastics (MP) plastic fragments….” should be “…presence of microplastic (MP) particles” as MPs can be classified into fragments, fibers, films and so forth.
3. L 76, “And” should not be capitalized.
4. L 90-91, sentence “A bucket…. per sampling point” is not clear and contains grammar errors.
5. L 144-145, this sentence contains grammar errors.
6. L 167, “for cultures” is redundant.
7. L 210, do the authors mean “white and blue pieces”?
8. L 261, “particle” was misspelled.
9. L 261-262, do the authors mean the surface area and volume-to-volume ratio decrease while the particle size decreases?
Minor editing of English language required.
Author Response
- L 24, I do not find any SEM evidence regarding the presence of diatoms on the surface of microplastics in the section of Discussion.
R/ Figure 10 C and lines 337-339
- The authors do not summarize the studies on microplastics in wetlands and state why it is necessary to characterize plastic particles in this wetland.
R/ Done. Lines 42-48
- L 90-96, sampling procedure should be stated more clearly. How did authors use tweezers to transfer MPs that were down to 25 microns to the tubes as small MPs were not visible via eyes?
R/ Done. Lines 107 – 123 (section 2.1 and 2.2)
- What were the criteria for selecting MPs from the mesh sieves during sampling campaigns?
R/ Done. Lines 120-121 (section 2.2)
- L 98-99, were the MPs filtered onto filters for optical observation? Please add some details here.
R/ Done. Lines 107 – 123 (section 2.1 and 2.2)
- L 100-101, was the major dimension of MPs reported in this study?
R/ Done. Lines 149-150 (section 3)
- L 33-35, the authors missed one of the quotation marks.
R/ Done. Quotes removed.
- L 51, “…presence of microplastics (MP) plastic fragments….” should be “…presence of microplastic (MP) particles” as MPs can be classified into fragments, fibers, films and so forth.
R/ Done
- L 76, “And” should not be capitalized.
R/ OK
- L 90-91, sentence “A bucket…. per sampling point” is not clear and contains grammar errors.
R/ Wording was changed.
11 L 144-145, this sentence contains grammar errors.
R /Done
- L 167, “for cultures” is redundant.
R/ Done
- L 210, do the authors mean “white and blue pieces”?
R/ Done
- L 261, “particle” was misspelled.
R/ OK
- L 261-262, do the authors mean the surface area and volume-to-volume ratio decrease while the particle size decreases?
R/ Changed. The size of the part decreases, the surface-to-volume ratio increases. Lines 332-334
Author Response File: Author Response.docx
Reviewer 3 Report
The authors tried to study how civilization affects plastic pollution and bacterial growth on it. Even though it has some novelty, there are obvious weaknesses.
General comments
One of the weaknesses is English. It should have been corrected before its submission. Sample preparation may have not been done properly. Some examples are shown below:
Lines 33, 109: Not proper way to cite.
Fig. 1: very difficult to see what is what.
Line 90: more details in sample are required such as exactly how, how deep, etc. A plastic bucket was used? If so, how to avoid contamination from the bucket?
Line 91: how to sample 35L using a 12 L bucket?
Line 92: When separating the organic and plastics, how to tell which is which? There can be something other than those two members such as rocks, ceramics (shell), and metals. Then, how to sort these out?
How to use the meshes, for example, collecting anything collected between the meshes?
Line 96: One of the themes was checking biofilm. Then, how to make sure that those separated plastics were not contaminated after being separated from the sampling and to minimize microbes growing during storing at 14oC?
Line 120: Why randomly?
Line 134: same scale?
Table 1 vs Figure 3: the numbers do not seem add up. I presume that Fig. 3 shows the total number. For example, 7 microplastics and 8 mesoplastics (thus the total 15) for Sampling 1, but Table 1 shows that there are 17. Which one is correct?
Lines 167-169, so what is the result?
Line 272, Suddenly cocci were addressed there. Any characterization?
One of the weaknesses is English. It should have been corrected before the submission.
Author Response
- Lines 33, 109: Not proper way to cite.
R/ Done
- 1: very difficult to see what is.
R/ The map was improved.
- Line 90: more details in sample are required such as exactly how, how deep, etc. A plastic bucket was used. If so, how to avoid contamination from the bucket?
R/ Done. Lines 107-115
- Line 91: how to sample 35L using a 12 L bucket?
R/ Wording was changed. Lines 107-108
- Line 92: When separating the organic and plastics, how to tell which is which? There can be something other than those two members such as rocks, ceramics (shell), and metals. Then, how to sort these out?
R/ Wording was changed. Lines 107-115
- How to use the meshes, for example, collecting anything collected between the meshes?
R/ Wording was changed. Lines 107-115
- Line 96: One of the themes was checking biofilm. Then, how to make sure that those separated plastics were not contaminated after being separated from the sampling and to minimize microbes growing during storing at 14oC?
R/It is explained in numeral 2.3.
- Line 120: Why randomly?
R/ Due to limitations of access to the SEM
- Line 134: same scale?
R/ I don't understand what you mean.
- Table 1 vs Figure 3: the numbers do not seem add up. I presume that Fig. 3 shows the total number. For example, 7 microplastics and 8 mesoplastics (thus the total 15) for Sampling 1, but Table 1 shows that there are 17. Which one is correct?
R/ Done. Error in Table.
- Lines 167-169, so what is the result?
R/ I don't understand what you mean.
- Line 272, Suddenly cocci were addressed there. Any characterization?
R/ None
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The author's response to most of the comments seems fine. But, authors should clearly mention the detailed revision in the response file with page and line numbers which would be easier for the reviewer to re-evaluate the revised version. At present, in most of the responses, aurors just wrote "done".
Minor English/typographical editing is needed for this manuscript.
Author Response
- Lines 33, 109: Not proper way to cite.
R/ Done
RR/ Ref 27 is fine, but Ref 1 is still not fine. Ref 1 is not the only issue. Ref 22 was not cited properly either.
RRR/ Ref 1 adjusted and Ref 22, ISBN included.
- Line 90: more details in sample are required such as exactly how, how deep, etc. A plastic bucket was used. If so, how to avoid contamination from the bucket?
R/ Done. Lines 107-115
RR/ Any particles (including non-plastics) staying between 4.75- and 25-micron sieves would be analyzed since they removed non-plastics sitting on the 4.75-micron sieve. Thus, there can be an issue.
RRR/ The first sieve was 4.75 mm and there those non-plastic particles were visually discarded…what remained on the 25-um sieve if everything was collected and analyzed.
- Line 91: how to sample 35L using a 12 L bucket?
R/ Wording was changed. Lines 107-108
RR/ Those lines do not talk about how to sample.
R/ Water was taken from the wetland three times with the 12L bucket, for a total of 36L.
They are explained at the beginning of the third paragraph (numeral 2.1)
- Line 92: When separating the organic and plastics, how to tell which is which? There can be something other than those two members such as rocks, ceramics (shell), and metals. Then, how to sort these out?
R/ Wording was changed. Lines 107-115
RR/ Visible inspection does not seem scientific.
RRR/ A separation in the laboratory using a microscope or stereoscope is adequate, but here the selection was made in situ without microscopes, visually using the first sieve (4.75 mm), which allowed differentiating large organic objects from plastics; everything else that was on the 25um sieve was collected and those were analyzed in the laboratory
- How to use the meshes, for example, collecting anything collected between the meshes?
R/ Wording was changed. Lines 107-115
RR/ Was that simply relying on gravity or did somebody shake the meshes. If it was the latter case, how long and how did they make sure that such action did not induce any change is the size of the particles?
RRR/ Water taken from the wetland was poured through the sieves, so particles larger than 25 microns were trapped on the finer sieve.
- Line 96: One of the themes was checking biofilm. Then, how to make sure that those separated plastics were not contaminated after being separated from the sampling and to minimize microbes growing during storing at 14oC?
R/It is explained in numeral 2.3.
RR/ Section 2.3 explains how to collect biofilm, not how to make sure no contamination after being sampled. Since biofilm on the MPs is a crucial part of the work, there should be a method to make sure that no more biofilm generation after sampling.
RRR/ In section 2.2, first paragraph, the procedure to avoid contamination is explained... the samples were washed in sterile water allowing microorganisms that were on the surface of the plastic to "fall off" but that were not part of the biofilm, since these are more difficult to learn Then they were dried on sterile petri dishes for 45 min (very short time for "new biofilms" to form).
- Line 134: same scale?
R/ I don't understand what you mean.
RR/ There are 10 pictures, but only one scale bar. Then, how can readers know the size of pieces in the other 9 pictures?
R/ The Scale was only placed on one image, but it is the same for all 10 images.
- Lines 167-169, so what is the result?
R/ I don't understand what you mean.
RR/ First, Figure numbers are wrong: Figure 10 (Line 193) and Figure 8 (Line 208).
RRR/ Corrected
- Authors made plastisphere as shown in Fig. 9. Any description about the result?
R/ Little annotation was included in the last paragraph of the discussion.
- Line 272, Suddenly cocci were addressed there. Any characterization?
R/ None
RR/ It is not scientific to address that way without characterization.
RRR/ Little annotation was included in the last paragraph of the discussion.
Reviewer 3 Report
The revision clearly has been done to improve the quality of the manuscript. However, there are still a lack of scientific approach.
1. Lines 33, 109: Not proper way to cite.
R/ Done
RR/ Ref 27 is fine, but Ref 1 is still not fine. Ref 1 is not the only issue. Ref 22 was not cited properly either.
2. Fig. 1: very difficult to see what is.
R/ The map was improved.
RR/ Ok
3. Line 90: more details in sample are required such as exactly how, how deep, etc. A plastic bucket was used. If so, how to avoid contamination from the bucket?
R/ Done. Lines 107-115
RR/ Any particles (including non-plastics) staying between 4.75 and 25 micron sieves would be analyzed since they removed non-plastics sitting on the 4.75 micron sieve. Thus, there can be an issue.
4. Line 91: how to sample 35L using a 12 L bucket?
R/ Wording was changed. Lines 107-108
RR/ Those lines do not talk about how to sample.
5. Line 92: When separating the organic and plastics, how to tell which is which? There can be something other than those two members such as rocks, ceramics (shell), and metals. Then, how to sort these out?
R/ Wording was changed. Lines 107-115
RR/ Visible inspection does not seem scientific.
6. How to use the meshes, for example, collecting anything collected between the meshes?
R/ Wording was changed. Lines 107-115
RR/ Was that simply relying on gravity or did somebody shake the meshes. If it was the latter case, how long and how did they make sure that such action did not induce any change is the size of the particles?
7. Line 96: One of the themes was checking biofilm. Then, how to make sure that those separated plastics were not contaminated after being separated from the sampling and to minimize microbes growing during storing at 14oC?
R/It is explained in numeral 2.3.
RR/ Section 2.3 explains how to collect biofilm, not how to make sure no contamination after being sampled. Since biofilm on the MPs is a crucial part of the work, there should be a method to make sure that no more biofilm generation after sampling.
8. Line 120: Why randomly?
R/ Due to limitations of access to the SEM
RR/ Ok
9. Line 134: same scale?
R/ I don't understand what you mean.
RR/ There are 10 pictures, but only one scale bar. Then, how can readers know the size of pieces in the other 9 pictures?
10. Table 1 vs Figure 3: the numbers do not seem add up. I presume that Fig. 3 shows the total number. For example, 7 microplastics and 8 mesoplastics (thus the total 15) for Sampling 1, but Table 1 shows that there are 17. Which one is correct?
R/ Done. Error in Table.
RR/ Ok
11. Lines 167-169, so what is the result?
R/ I don't understand what you mean.
RR/ First of all, Figure numbers are wrong: Figure 10 (Line 193) and Figure 8 (Line 208).
Authors made plastisphere as shown in Fig. 9. Any description about the result?
12. Line 272, Suddenly cocci were addressed there. Any characterization?
R/ None
RR/ It is not scientific to address that way without characterization.
Figures numbers should be carefully shown.
Author Response
- Lines 33, 109: Not proper way to cite.
R/ Done
RR/ Ref 27 is fine, but Ref 1 is still not fine. Ref 1 is not the only issue. Ref 22 was not cited properly either.
RRR/ Ref 1 adjusted and Ref 22, ISBN included.
- Line 90: more details in sample are required such as exactly how, how deep, etc. A plastic bucket was used. If so, how to avoid contamination from the bucket?
R/ Done. Lines 107-115
RR/ Any particles (including non-plastics) staying between 4.75- and 25-micron sieves would be analyzed since they removed non-plastics sitting on the 4.75-micron sieve. Thus, there can be an issue.
RRR/ The first sieve was 4.75 mm and there those non-plastic particles were visually discarded…what remained on the 25-um sieve if everything was collected and analyzed.
- Line 91: how to sample 35L using a 12 L bucket?
R/ Wording was changed. Lines 107-108
RR/ Those lines do not talk about how to sample.
R/ Water was taken from the wetland three times with the 12L bucket, for a total of 36L.
They are explained at the beginning of the third paragraph (numeral 2.1)
- Line 92: When separating the organic and plastics, how to tell which is which? There can be something other than those two members such as rocks, ceramics (shell), and metals. Then, how to sort these out?
R/ Wording was changed. Lines 107-115
RR/ Visible inspection does not seem scientific.
RRR/ A separation in the laboratory using a microscope or stereoscope is adequate, but here the selection was made in situ without microscopes, visually using the first sieve (4.75 mm), which allowed differentiating large organic objects from plastics; everything else that was on the 25um sieve was collected and those were analyzed in the laboratory
- How to use the meshes, for example, collecting anything collected between the meshes?
R/ Wording was changed. Lines 107-115
RR/ Was that simply relying on gravity or did somebody shake the meshes. If it was the latter case, how long and how did they make sure that such action did not induce any change is the size of the particles?
RRR/ Water taken from the wetland was poured through the sieves, so particles larger than 25 microns were trapped on the finer sieve.
- Line 96: One of the themes was checking biofilm. Then, how to make sure that those separated plastics were not contaminated after being separated from the sampling and to minimize microbes growing during storing at 14oC?
R/It is explained in numeral 2.3.
RR/ Section 2.3 explains how to collect biofilm, not how to make sure no contamination after being sampled. Since biofilm on the MPs is a crucial part of the work, there should be a method to make sure that no more biofilm generation after sampling.
RRR/ In section 2.2, first paragraph, the procedure to avoid contamination is explained... the samples were washed in sterile water allowing microorganisms that were on the surface of the plastic to "fall off" but that were not part of the biofilm, since these are more difficult to learn Then they were dried on sterile petri dishes for 45 min (very short time for "new biofilms" to form).
- Line 134: same scale?
R/ I don't understand what you mean.
RR/ There are 10 pictures, but only one scale bar. Then, how can readers know the size of pieces in the other 9 pictures?
R/ The Scale was only placed on one image, but it is the same for all 10 images.
- Lines 167-169, so what is the result?
R/ I don't understand what you mean.
RR/ First, Figure numbers are wrong: Figure 10 (Line 193) and Figure 8 (Line 208).
RRR/ Corrected
- Authors made plastisphere as shown in Fig. 9. Any description about the result?
R/ Little annotation was included in the last paragraph of the discussion.
- Line 272, Suddenly cocci were addressed there. Any characterization?
R/ None
RR/ It is not scientific to address that way without characterization.
RRR/ Little annotation was included in the last paragraph of the discussion.
Author Response File: Author Response.docx
Round 3
Reviewer 3 Report
The authors need to know how to cite a reference properly. For example, “According to the report by Peck [1]” is a proper way.
They also need to understand that missing information can lead to misunderstanding. For example, Figure 2 has only one scale bar for 10 pictures without stating anything about the scale of each picture.
The authors need to know how to cite a reference properly. For example, “According to the report by Peck [1]” is a proper way.
They also need to understand that missing information can lead to misunderstanding. For example, Figure 2 has only one scale bar for 10 pictures without stating anything about the scale of each picture.
Author Response
1. The authors need to know how to cite a reference properly. For example, “According to the report by Peck [1]” is a proper way.
R/ Modified reference (first paragraph of the Introduction)
2. Figure 2 has only one scale bar for 10 pictures without stating anything about the scale of each picture.
R/ Done. A scale bar is placed on each image in Fig. 2.
Author Response File: Author Response.docx
