Review Reports - Nautical Tourism in Marine Protected Areas (MPAs): Evaluating an Impact of Copper Emission from Antifouling Coating

Round 1

Reviewer 1 Report

The study is very interesting and highly necessary as this field of research is not explored compared to other areas of knowledge.

Although the study is of significant importance to the audience of sustainability, I will recommend that authors further work on the study before it can be considered for publication in this journal.
Therefore, authors are advised to incorporate the following observation in improving the quality of the study:

The research gap is unclear. The authors should justify the value of their contribution in the introduction section. Why is this research important?, What has previous research discover and cover?
The introduction section needs to be improved. It will be convenient to add more references to make the paper robust. I suggest you develop aspects related to marinas because of their close connection with recreational boating including recent references.
The conclusions needs more clarity. It will be essential to improve the limitations of the study and the next lines of investigation.

Author Response

The study is very interesting and highly necessary as this field of research is not explored compared to other areas of knowledge.

1. The research gap is unclear. The authors should justify the value of their contribution in the introduction section. Why is this research important?, What has previous research discover and cover?

Response: The research gap and contribution are now more emphasized through the text, especially in the introduction and conclusion paragraphs.

2. The introduction section needs to be improved. It will be convenient to add more references to make the paper robust. I suggest you develop aspects related to marinas because of their close connection with recreational boating including recent references.

Response: The introduction has been improved to make it clearer

3. The conclusions needs more clarity. It will be essential to improve the limitations of the study and the next lines of investigation.

Response: Conclusion was rewritten to become clearer and the next lines of investigation were highlighted.

Reviewer 2 Report

This is an interesting manuscript however there are some points that need to be corrected

1) there is a need for English proofreading. The problem is not overt mistakes but rather the use of improper phrases, so the correction should be done with caution by a fluent English speaker see some examples here

replace

Nautical tourism provides the stress to the environment by

with

Nautical tourism causes environmental stress by

replace

are partly regulated, the others are not as described

with

are partly regulated, some others are not

you state

Since copper pollution is a worldwide problem, particularly in semi-enclosed areas, 60
pleasure craft marinas and anchorage areas

a verb is needed

you state

A separate software ("Check Boats") was also developed to analyses collected data in 125
manual/automatic mode and to create numerical and graphical reports for the chosen pe- 126
riod.

you mean to analyze?

replace

For the assessment of underwater sur- 134
faces of ships, they are divided into three categories (less than 7 m, 7-15 m and more than 135
15 m)

with

Underwater ship surface was categorized into 3 classes (less than 7 m, 7-15 m and more than 135
15 m)

cm2 2 should be superscript

please proofread throughout

2) there are a number of textbook information pieces that are not needed. also some textbook information that is not relevant here eg TBT. please erase or shorten lines 32-43, 39-51,

3) lines 61-71. In this part you have to state exactly the purpose of your study. You claim some things that are understandable however some others are not eg what frame working the discussion by fo- 68
cusing on the policy structures in relation to Cu-related eco(toxico)logical risks means? also extending the data from the ratio of copper concentrations and nautical tourism to assess 70
the other risks (hydrocarbon, fecal coliform, marine waste, underwater noise, etc.) is described here? if not it should be erased

please rephrase the aims and scope of the research at this point

4) lines 95-99 I dont understand what is claimed here. is this a reliability problem of the study or something else?

5) 1.1 study site

this part is well described but it should be shortened to 2/3 of present length

6) I dont understand why two different softwares were used. please clarify.

7) for all the software and apparatuses used please state as following: name or type of apparatus, manufacturer, city, country of origin. This should be done for everything used eg bottles, weighing scales, filters, reference material, softwares, cameras, microscopes etc

8) I am not quite sure how part 2.2. Assessment of the nautical status by using drone spot monitoring and heat-maps is organically linked with the rest of the methods. you state that the sampling took place at between June 2018 and October 2019. I also guess Video surveillance system was at the same time. The drone survey was at August 2018. also if I see correctly from the map the drones are in places that are far from the sampling points. Please explain more clearly what the drone survey contributed and how

9) I am not quite sure about the actual sampling of water. You state that it was done at the entrance of the marine station Martinska and "upstream" transversal profile sites, so how many sites were there? you never stated the number of sampling sites. or there was only one and this was correlated with the other data? how reliable is it then to correlate actual measurements of Cu only at one site with the other methods? all these should be more understandable for the reader

10) it is very important that you corrected for the biogenic Cu your measurements. Please see also Okamura et al (2021) Floating particles with high copper concentration in the sea-surface microlayer and compare the methods

11) the part 2.4. Estimation of the antifouling emission

I am not quite sure where this information you obtained from this reaserch was used in your results and discussion. was it to predict the Cu emission and to compare with actual Cu levels? please elaborate

12) Figure 4. Correlation of maritime traffic and Cu concentrations. how was this Figure created? with data from what analyses?

13) do not repeat parts of materials and methods in results and discussion eg lines 263-265

14) the formula in materials and methods should be given as stand alone and not part of the text. also the A, B, etc should be explained as

where A: submerged hull area (cm2),

not

In the equation, A is submerged hull area (cm2),

etc...

15) the part 3.3. Estimating the Cu toxicity risk is very important but be careful-you never examined the toxicity in materials and methods! as such it cannot possibly be part of your discussion. All you can do is to verify that these concentrations will be toxic for marine biota based on the results you obtained, but this cannot be part of your actual results. This has to be clear in the text

16) discussion and especially conclusion should be rewritten so that the reader can understand what each method you applied corresponded to these results (eg the drone application etc) because right now it is not clear. Conclusion should not talk about new findings and other topics but it should summarize your most important results

17) you have to use italics in all species names

Author Response

This is an interesting manuscript however there are some points that need to be corrected

replace

Nautical tourism provides the stress to the environment by

with

Nautical tourism causes environmental stress by

Response: Done

replace

are partly regulated, the others are not as described

with

are partly regulated, some others are not

Response: Done

you state

Since copper pollution is a worldwide problem, particularly in semi-enclosed areas, 60
pleasure craft marinas and anchorage areas

a verb is needed

Response: Corrected, we are sorry for this mistake.

you state

A separate software ("Check Boats") was also developed to analyses collected data in 125
manual/automatic mode and to create numerical and graphical reports for the chosen pe- 126
riod.

you mean to analyze?

Response: Corrected

replace

For the assessment of underwater sur- 134
faces of ships, they are divided into three categories (less than 7 m, 7-15 m and more than 135
15 m)

with

Underwater ship surface was categorized into 3 classes (less than 7 m, 7-15 m and more than 135 15 m)

Response: Replaced.

cm2 2 should be superscript

please proofread throughout

Response: Corrected at 5 locations.

2) there are a number of textbook information pieces that are not needed. also some textbook information that is not relevant here eg TBT. please erase or shorten lines 32-43, 39-51,

Response: Thanks to the reviewer for the suggestion. The paragraph is shortened and most of the unnecessary facts about TBT are excluded.

please rephrase the aims and scope of the research at this point

Response: Rephrased

4) lines 95-99 I dont understand what is claimed here. is this a reliability problem of the study or something else?

Response: Yes, this is a real problem pointed out by our preliminary research from 2014.

5) 1.1 study site

this part is well described but it should be shortened to 2/3 of present length

Response: Study site paragraph is shortened

6) I dont understand why two different softwares were used. please clarify.

Response: The "other" software used for analysis of captured images was develop separately in order to be used for any other type of similar data images in "off line" mode.

Response: These data are updated.

Response: The drone survey was carried out to get a clearer picture of the distribution of maritime traffic (mostly nautical tourism) in the area. This also helped to correlate the spatial distribution of traffic with the sampling. Changes have been made in the text to improve this argument.

Response: It was one regular sampling site in front of our marina station located in front of city of Šibenik. However, we did several sampling surveys in other part of the Krka River Estuary.

Response: The corresponding paper is related to the particulate copper in the sea-surface microlayer (SML). However, in our study we sampled underlaying water (ULW) and the sample was filtered. As such, the particulate fraction is avoided. Nevertheless, this paper is very useful for our other study we are performing related to the sea-surface microlayer. Many thanks for the suggestion.

11) the part 2.4. Estimation of the antifouling emission

Response: This section is a short overview discussing the estimation of Cu emission based on work of other authors which we used as a base to estimate the emission in our study.

12) Figure 4. Correlation of maritime traffic and Cu concentrations. how was this Figure created? with data from what analyses?

Response: Figure 4 was created using our data on the number of ships, and the results of measuring the concentration of copper in the surface layer.

13) do not repeat parts of materials and methods in results and discussion eg lines 263-265

Response: Corrected

14) the formula in materials and methods should be given as stand alone and not part of the text. also the A, B, etc should be explained as

where A: submerged hull area (cm2),

not

In the equation, A is submerged hull area (cm2),

etc...

Response: Formula is separated, and A, L, B, and D are explained.

Response: The Cu toxicity in our study is discussed based on findings of other authors. As the discussion section is merged with results section, there is no other place to comment the toxicity of Cu we measured in our samples. The text is English-corrected, so we hope it is now clearer.

Response: Done.

17) you have to use italics in all species names

Response: Done.

Reviewer 3 Report

In this study, the authors explored the relationship between maritime traffic and the Cu concentration through a pilot study performed within the marine protected area (MPA) of the Krka River estuary in Croatia over 16 months period. They found that seasonal increase of maritime traffic caused by nautical tourism coincides with the increase of Cu concentrations by more than 5-fold. This provides findings of Cu-related toxicity risks of Cu that should be considered in the marine management and planning processes. Hence, I think that the results presented here are valuable. My comments are given below.

Lines 67–71: Are there results and discussion on Objectives (ii) and (iii) in this paper?

Line 171: The authors should explain the reason why only surface sample (depth ~0.5 m) was collected? In warm season, it is expected that Cu concentration in water column varies depending on the stratification of the estuary. What is the vertical profile of Cu concentration in a stratified period?

Lines 192–193: The results of the validation (e.g., recovery efficiency and standard deviation of replicate measurements) should be shown.

Lines 204–206: The authors should explain concretely what “bioindicators” and “sediment research of the location” are.

Line 225: What does “0.9” in the equation mean?

Line 240: This sentence is cut off in the middle.

Lines 254–258: As already pointed out by the reviewer, in warm season, it is expected that Cu concentration in water column varies depending on the stratification of the estuary. This should be discussed.

Lines 294–296: The authors should explain why estuarine DOC is more protective against Cu-toxicity than the pure marine (oceanic) DOC, buffering the impact of Cu.

Line 313: Is “biomagnification” for Cu a fact? If so, cite references.

Author Response

Reviewer #3: Responses

Comment: Lines 67–71: Are there results and discussion on Objectives (ii) and (iii) in this paper?

Response: There are no direct results related to these two objectives, while the discussion is based on the literature overview. To avoid confusion, this part of the text is corrected to: "This work aims primarily to assess the relationship between Cu concentrations and nautical activities and to direct the discussion towards policy structures related to Cu-related ecological and toxicological risks. The survey methodology used should also be applicable to other types of contaminants to estimate their ecotoxicological risk (hydrocarbons, fecal coliforms, marine litter, underwater noise, etc.)."

Comment: Line 171: The authors should explain the reason why only surface sample (depth ~0.5 m) was collected? In warm season, it is expected that Cu concentration in water column varies depending on the stratification of the estuary. What is the vertical profile of Cu concentration in a stratified period?

Response: We thank reviewer for noticing this. Our previous studies (references 16 and 17) revealed that the influence of increased copper was mostly limited to the surface (brackish) layer up to dept about 2 m. Below the halocline (in a seawater layer), the Cu concentration is very similar, all over the year (~0.4 ug/L). In winter period, the Cu concentration in surface layer is usual lower than in the bottom, seawater layer, while in summer period it is opposite. The thickness of the halocline is usually up to 1 m.

Comment: Lines 192–193: The results of the validation (e.g., recovery efficiency and standard deviation of replicate measurements) should be shown.

Response: The quality control data is added: "The value obtained (±standard deviation) was 0.370 ± 0.030 μg L-1 (the certified value is 0.380 ± 0.028 μg L-1)."

Comment: Lines 204–206: The authors should explain concretely what “bioindicators” and “sediment research of the location” are.

Response: This part of the text is describing only the previous studies performed in Dubrovnik port (Craotia), related to cruise ships (ref 25) and the use of passive sampling technique (DGT) to access bioavailability of trace metals in water column along with the analysis of sediment samples (Queensland, Australia) (ref 26). We think further clarification of the terms pointed by the reviewer is not necessary here.

Comment: Line 225: What does “0.9” in the equation mean?

Response: The factor "0.9" is a constant estimated empirically to describe a formula of a hull area calculation. The formula is adapted from an Environmental Impact Assessment Study that analyzed the sailboats' and speedboats' bases similar to the base shape of the nautical vessels visiting the Adriatic (Legović, T., 2005. Environmental Impact Assessment Study: Port in Seget Donji (in Croatian). Ekonerg, Zagreb, Croatia.)

Comment: Line 240: This sentence is cut off in the middle.

Response: Thanks for noticing this. The number 65 is missing at the end. This is corrected.

Comment: Lines 254–258: As already pointed out by the reviewer, in warm season, it is expected that Cu concentration in water column varies depending on the stratification of the estuary. This should be discussed.

Response: As explained in the previous response, the vertical profiles in the water column are different for winter and summer period. However, the concentration of Cu in the seawater layer is not changing over the year. Thus, the only change is in the surface layer, which is studied in this work. We would like to avoid further explanation of the vertical profiles as this is out of the aim of this study. For more details readers are directed to our previous papers (ref 16 and 17). A short sentence is added to this part of the text: "Note that the Cu concentration in the lower seawater layer changes only slightly throughout the year, i.e. the vertical transport down to deeper layers is insignificant (for more details see [16, 17])."

Lines 294–296: The authors should explain why estuarine DOC is more protective against Cu-toxicity than the pure marine (oceanic) DOC, buffering the impact of Cu.

Response: The higher protective effect of estuarine DOC is found by the study of Zitoun et al. (2019) (ref 34). To better clarify, we added the following sentence: "This is related to the higher input of humic substances by the rivers, which form strong Cu complexes, making it less bioavailable. "

Comment: Line 313: Is “biomagnification” for Cu a fact? If so, cite references.

Response: We are sorry for this mistake. Biomagnification in food chains is not related to Cu. The term is removed from the line.

Round 2

Reviewer 1 Report

Although the introduction has considered the questions that were asked, it continues to lack consistency. The introduction should be extended and consider more papers to make it robust (it currently has 15). Please, complete this part with more citations (at least 35).

Author Response

We thank reviewer for the new comments. The Introduction is slightly updated and the number of references is considerably increased. However, we think that there is no exact number of references which should be cited as long as the subject discussed in the work is elaborated with adequate references. Overreferencing is not recommended, and use of the most recent publications, from which back referencing is possible, is preferred. This was our guiding principle in writing the Introduction.

Reviewer 2 Report

The manuscript has been improved. please see the following

1) proofreading is still needed. for example, besides proofreading for English there are some mistakes due to carelessness eg policy makers are once written as policymakers, M galloprovincialis is not in italics once and also in some cases there are more than one spaces between words eg the house instead of the house

2) I understand that you wanted to incorporate the risk factor in your research however you should make it clearer that you didnt actually test for ecotoxicity but that through the levels you found, you can infer ecotoxicity, both in the introduction and in the discussion

Author Response

We thank reviewer for careful reading of the text. We made proofreading and we hope the updated version is free of typing mistakes.

Reviewer 3 Report

I think that the revised manuscript has been satisfactorily improved.

Author Response

Many thank for supporting our work