Microplastic Distribution Characteristics Considering the Marine Environment Based on Surface Seawater Quality Parameters in Southern Sea of Korea, 2019
, Hui Ho Jeong 2, Ji Hoo Kim 1, Byeong Kyu Min 3, Chon Rae Cho 4, Ho Young Soh 1, Yasuhiro Ishibashi 2 and Hyeon Seo Cho 1,*Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript (sustainability-3013853) deals with the microplastic distribution in the Southern Sea of Korea in relation to marine water environmental factors, such as water temperature, salinity and pH. Although the paper addresses an interesting topic, I do not believe that paper is publishable in its current form. There are several main reasons for my decision.
- I find the main paper's conclusions are not supported enough by the obtained data. Only one sampling campaign was performed and the obtained data ranges of several parameters are too narrow to discuss the influence of environmental water parameters on the distribution of the microplastics. In particular, salinity was found in the range 31.08-31.63, so I find the discussion about low and high salinity unmeaningful.
- The research area has been divided into 3 groups: A, B, and C, based on the data. However, I believe that differences between sampling points within the group, particularly in group C, are too high to make general conclusions such as “group C has the highest abundance of microplastics, from which the majority is EPS”. Yes, it is true when you calculate the average from points 3, 4 and 6, but this is due to the domination of the point SS04. For example, point SS03 has one of the lowest abundances recorded in the study area, and no EPS was detected.
- The authors have used the Nesuton net with a mesh size of 300 µm for the sampling, and as they pointed out in section 2.3.2.3 the maximum length of particles that can pass through a 300 µm net is about 0.42 mm. Yet, the dominant size fraction at 6 of 9 sampling sites is 0.1-0.5 mm (at 3 sites this fraction comprises over 90%).
- As the authors also remarked, it was unusual that fibres were not found in this research, because they are extensively reported in studies on microplastics in marine surface waters, even in the previous studies in the Sothern Sea of Korea. I find the author's explanation for the lack of fibres due to the sampling method (net 300 µm) unlikely as other authors worldwide use the same methodology and find a lot of fibres. Moreover, the low amount of PE particles was also very unusual.
However, I advise the authors to consider rewriting this paper, as they have done a lot of work, and it would be a shame that the obtained data remain unpublished.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors• Line 19-20 - Rephrase this sentence “The distributions of microplastics by group were determined with microplastics collected with a 300 ㎛ Neuston net.”
• Line 44 - can you provide a data for a newer year (2023?)
• Line 53 – please clarify this number “51 trillion“, in what volume
• Line 69 – Increase the risk to what?
• Line 99 – please rephrase „ Against the backdrop as such“
• Line 111 – please provide coordinates of a sampling locations
• Line 133 – change „analysis items“; maybe „analysed parameters“
• Line 180 and 183 – was it a bottle, or it could be better described as a sample container
• Line 238 – it is a question what it does mean to classify – in terms of MP it could be to determine the type of polymer. Clarify what do you mean
• Line 276 - in more clear way describe process of QA/QC; How did you separate defined number of particles (line 279)
• Line 338 – with or by instead of through
• Line 340 and 341 - 1.9% and 1.3% not 1.90 or 1.30%
• Line 346 – add „and“ (The composition of microplastic polymer, size, and shape.)
• Line 483 - define EPS; in chapter 3.2.2. you are only presenting the results for PS. Are you distinguishing these two?
• Following on to the previous comment, align the text where EPD is mentioned (e.g. chapter 4.2.2)
• Line 565 – worn should be replaced with weathered or degraded
• Line 592 – paint particle is not the best description, please consider a change
• Line 633 - please additionally elaborate sentence “ and suggests that the Southern Sea of Korea is playing a role in identifying marine plastic pollution on a global scale.“, especially regarding the part „ playing a role in identifying marine plastic pollution“. This should be rephrase, or additionally explained in Discussion.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript entitled “Microplastic Distribution Characteristics Considering the Marine Environment Based on Surface Seawater Quality Parameters in Southern Sea of Korea, 2019” focused on the presence of microplastics in surface marine waters related to the environmental parameters.
Although the paper is interesting and give a new vision of the problem, it need to be improved before the publication.
Introduction
Line 44: add more recently data on global plastic production
Line 55: It's not entirely true that there's no human activity; in fact, there are several bases belonging to many countries around the world, and there are various jobs that confirm that the bases themselves can be sources of microplastics. (i.e. the papers by Mancuso et al. 2023, Monitoring of anthropogenic microplastic pollution in antarctic fish (emerald rockcod) from the Terranova Bay after a quarter of century, and Bottari et al. 2022, Anthropogenic microparticles in the emerald rockcod Trematomus bernacchii (Nototheniidae) from the Antarctic), so I suggest changing the sentence.
Line 62: In this case too, I disagree with what the authors claim. Plastics themselves are inert, but when they reach the sea due to a series of chemical and physical factors, they change their structure and become capable of absorbing a whole range of toxic substances, including heavy metals, PAHs, etc., which can bioaccumulate along the food chain and thus reach humans. I ask you to rephrase."
Line 69: the sentence ends halfway, please fix it, it increases the risk of what?
Line 106: I suggest adding a line with expected results.
Microplastic analysis: I have some doubts about the fact that in my opinion all these steps could lead to airborne pollution. I recommend you write a detailed paragraph on QA/QC. How many checks have you carried out? How many samples did you have to discard because they were polluted?
Paragraph 2.3.2.2 I would directly start talking about the identification method used in your study.
Table 1: It is too big to tighten otherwise it will be cut.
Figure 4: The photos are not good, replace them with better ones.
3.2.2 start talking about PP first, then PE etc. following the order in which they were listed, this will avoid confusion
Discussions
I would like the discussions to be more detailed, I recommend making a synoptic table with the studies carried out so far on microplastics in surface water, this will help you in the discussions. Furthermore, I would like each polymer found to be discussed both with respect to what has been found in the same area by other authors but also what the origin of the polymers found is. The conclusions should be more comprehensive and enhance your results.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsL40-42 With this sentence construction, it seems like sunscreen is a microplastic, I believe it should be written something like "microplastics are added to various products such as sunscreen".
L55 floats in the global surface water
L56 Risk of what?
Fig1. Please add a north arrow and a scale to the map
L133 I don't see how it is a vertical water temperature if samples were collected at 0.5m and then measured onboard, it is a bit confusing.
L129 “along with seawater samples” is a bit confusing, either add seawater samples for Chl and SPM or delete it as it is mentioned in the next section. In fact, the L116-139 is a bit confusing, because at the end reader is not sure if (1) samples were taken with a Rosettes Water Sampler, and then on board some parameters were measured by the probe and some samples frozen for Chl and SPM, or (2) salinity, DO…were measured with the probe in situ, and just samples for SPM and Chl were taken with a Rosettes and frozen until further analysis.
L161 I would say water samples not plastic samples
L291-295 There is a big difference in precision between this study and the previous studies on the pretreatment methods.
L328-330 This part is very confusing, please write it clearly. What is this total 6.39 particles/m3?
Table 1. Word fragment – the last letter (t) is not in the same line with the rest of the word. It's the same with acrylate.
Figure 3. The scale for these bars is not clear, the SS08 and SS04 seem the same, although their values are quite different.
L341 Nylon is the only one written with the first capital letter.
L348 Butyl is written in lowercase, it should be uniform in the entire manuscript. Check it for all polymers in the whole manuscript.
Figure 5. It is better to write …in the entire sampling area.
L361-363 It would be better to rewrite this sentence because the dominant distribution of fragments appeared at all sampling points except SS07. If you want to highlight that on some sampling points, there are no sheets detected or the number of sheets is negligible, you need to write it more clearly. Also, “The ratios of sheet-type MPs were relatively 361 high at SS01, SS02, and SS07 adjacent to land”, I would say that sheets are dominant at SS07 and relatively high at SS01 and SS02.
Although the authors made substantial improvements to the manuscript, I still don’t believe the grouping of points based on PCA was suitable for this study. The obtained ranges for different parameters were too narrow, especially if we consider that the sampling was done over 4 days. Moreover, we don’t know anything about the PC3, and it explains more than 20% of the variance. I would suggest the authors remove this analysis from the paper.
Comments for author File: Comments.pdf
Author Response
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Author Response File: 
Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsDear authors,
I saw that following the suggestions of the reviewers the manuscript has been improved and in my opinion, it is now ready to be accepted for publication.
Author Response
Dear Editor and Reviewer 3:
We wish to published the manuscript entitled “Microplastic Distribution Characteristics Considering the Marine Environment Based on Surface Seawater Quality Parameters in Southern Sea of Korea, 2019” to the sustainability.
We appreciate the editor and reviewers for your consideration to first revision. Our manuscript was improved through your thoughtful suggestions and insights. We believe that this manuscript closer to published to the journal sustainability.
We appreciate your hard work, dedication, and cooperation again.
Sincerely,
10 July 2024
Corresponding Author
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsThe following comment "Moreover, we don’t know anything about the PC3, and it explains more than 20% of the variance. I would suggest the authors remove this analysis from the paper" was done based on the older version of the supplementary material where it was written that eigenvalue for PC3 is 1.527 and its proportion 21.815%. I apologise if I didn't look at the newest version of the supplementary.
