Monitoring Aquatic Debris in a Water Environment Using a Remotely Operated Vehicle (ROV): A Comparative Study with Implications of Algal Detection in Lake Como (Northern Italy)
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The topic of the research is undoubtedly important and relevant in modern conditions, when an ever-increasing flow of solid waste enters aquatic ecosystems, and the development of methods for detecting and counting garbage becomes an important task.
However, after reading the manuscript, I had a misunderstanding.
Abstract
First, there is a discrepancy between the results mentioned in the abstract and the content of the article. In particular, in the abstract, the authors announce “…a novel approach that optimizes the operation of remotely operated vehicles (ROVs) to spot submerged debris even in the presence of dense algal blooms”. However, it is unclear what exactly this new optimized approach consists of. Further, the authors report that they adapted “…data processing techniques to filter out algal noise”, but in the manuscript, data filtering to reduce algal noise is not mentioned at all. The authors then report that their technology allows filling a critical gap in modern methods of studying garbage. But it is unclear what exactly this critical gap consists of.
The authors then write that they are studying "...the accumulation, distribution, sources... of debris", although the text of the article contains no information about the accumulation, distribution, or sources of debris.
It is possible that the drawing after the abstract should clarify the sources of debris entering the lake, but the authors do not comment on this drawing in the text. As for the accumulation and distribution of debris, there is no information about this.
In the last sentence of the abstract, the authors again mention an improved methodology, but it is unclear what exactly the improvement consisted of.
My recommendation is to rewrite the abstract to highlight only the results achieved in the study.
Introduction, Methods
The introduction section is written quite informatively, the authors report on the existing difficulties in studying debris using underwater vehicles. However, the last paragraph of the introduction again contains discrepancies with the content of the manuscript. In particular, the authors indicate that they assessed the effect of turbidity caused by algal blooms, they received an idea of ​​the seasonal variability of monitoring accuracy. However, the manuscript does not contain a joint analysis of water turbidity (we do not see turbidity series), as well as its seasonal variability. Lines 140-142 report that turbidity was assessed at a qualitative level, which raises the question, how many turbidity levels were there? Were there two - turbid and clear water - or more? For example, very turbid, not very turbid, almost clear, clear?
In any case, it would be worth adding at least some criterion of water turbidity to figures 4–9 and 11 to understand what is turbid water from the authors’ point of view. For example, I don’t see much difference in water turbidity in photos 3, 8, 10, 11. By the way, it would be good to add the dates to the captions to the photographs.
Line 78-79: The authors use the phrase "lake surface" when they mean "lake bottom surface". Perhaps it would be better to use the phrase "lake bottom surface" here.
Figure 1 - The authors have outlined the contours of the research area, but it would be very good if they had put a scale ruler on the figure 1 and marked the routes of their floating apparatus in different colors for different months and years. This is necessary for understanding the results. In particular, I have a question about how the amount of rather large metal pieces of garbage on the lake bottom could have decreased so critically with a difference of 1-2 months - see Figures 4 and 5. Was garbage collected and removed between surveys? If so, then information about this should be added. Or was the survey conducted along a new route each month? If so, then what was the length of the routes in each month? How can we compare different months and years if there is no information about the path traveled or the area surveyed? Or was the entire survey area marked in Figure 1 as redline surveyed every month? Information about this should be added to the manuscript.
It is also unclear what is the shooting width in meters while the device is following the route and what is the height of the device above the bottom? Information on the distribution of depths at the testing ground would also be useful.
Lines 158-160: the authors write about seasonal and time trends, which is an unfortunate term. A trend implies changes over a fairly long period of time. It is more correct to talk about detected changes in the number of garbage objects in different months and different years.
Lines 162-166: the authors write about the distribution of garbage units on the bottom along the drone routes, however, the results section does not present maps of the garbage distribution across the water area in different months and years, but provides integral characteristics for each month for the entire survey area. Therefore, it is necessary to add to the manuscript a diagram of the spatial distribution of garbage units along the bottom of the studied area of ​​the lake or at least add a description of how exactly the garbage was distributed along the bottom, whether there were "constant" centers of garbage accumulation or each survey showed a new picture, otherwise the authors' assertion that they studied the distribution of garbage is unfounded.
Lines 168-173: Given the clear differences in the number of waste units in different years, the choice of the analysis method and the essence of the null hypothesis are unclear.
Results
First of all, it would be very good to increase the font size in the axis labels, in the legend and in the figures 4, 5, 6, 7 and 9 themselves, since now it takes some effort to see what is written there.
Secondly, it would be very informative if the water turbidity criteria were added to the figures and photographs.
Lines185-188: In April 2019, 9 beach beds were found, in May - 8. In my understanding, a beach bed is a fairly large and water-heavy metal object that cannot be carried away by the current and cannot be completely buried by bottom sediments in one month. The question is - where did one beach bed disappear? In this regard, the assumption arises that the filming path was different in April and May 2019. Or it is possible that between the filming, partial cleaning of the lake bottom was carried out and one of the beach beds was pulled out of the lake.
Lines 203-219: It is completely unclear where all the metal objects disappeared to in February and April-June 2024. Perhaps the bottom was cleaned in February 2024. Then the bottom was quickly covered with garbage in March, and then cleaned again. If this is not the case, then the question arises as to how sophisticated the bottom survey method was.
Lines 222-244: As for the changes in the number of plastic objects, due to their very heterogeneous composition - from candy wrappers to plastic chairs - it is difficult to judge the dynamics of their numbers. At times it is generally difficult to understand the logic of the authors. I do not understand at all how it is possible to identify and count such heterogeneous objects as candy wrappers and a plastic chair on the bottom, based on video recording data with not very good resolution. To begin with, many candy wrappers can be hidden under one plastic chair, which are not visible and therefore not taken into account during video recording.
The results of the statistical analysis presented in paragraph 3.5 are completely incomprehensible - despite the obvious difference in the number of units of waste in the two years under study, the authors note that no statistically significant difference was found.
Figure 10: It seems that the figure is turned inside out - the panels and letters on the panels are mirrored. By the way, there is a lack of decoding of the letter designations a, b, c and so on of the different panels.
Lines 300-304: What year is meant here? The conclusion does not correspond to what is shown in figures 4, 5, 6, 7.
Lines 364-369: Item 4.3 requires at least a small paragraph of text, so far it only contains a table.
line 372: what do the author
Author Response
Please find the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
The manuscript entitled Monitoring Aquatic Debris in a water environment using a remote operating vehicle (ROV): A Comparative Study with implications of algal detection in Lake Como (Northern Italy) Minor (Moderate) revision
Abstract
The Abstract should be re-written again and some parts of the Abstract can reflected the main insights.
Because of the large number of the words, the section of Abbreviation can be included in the main text.
The one sentence of the limitations could be included too in this part of the manuscript too.
Very well drawn graphical Abstract
Introduction
The Introduction is good written but for my opinion could be a little bit extended. In this section, the authors need to add more about similar research and that way the authors can compare they own findings.
Can the authors add more about Debris flow in other space more facts? In that way would be interesting for further comparisons.
Also the main methodology is good to be labeled in this section too.
Because of all before labeled, I highly recommend to the authors to read and cite one valuable reference.
- Yousefi, S., Jaafari, A., Valjarević, A. et al. Vulnerability assessment of road networks to landslide hazards in a dry-mountainous region. Environ Earth Sci 81, 521 (2022). https://doi.org/10.1007/s12665-022-10650-z.
Materials and Methods
Figure 1. Because authors did not put coordinates I ask to labeled to place in one sentence.
Tell me more information about camera drone properties.
The authors need to add more facts about climate patterns of this region.
The main problems within this research addressed in the next issues.
1. The study used visual counts for debris identification, which lacked differentiation between debris sizes and types. This limitation restricts the conclusions that can be drawn about the environmental impacts of the debris, explain better.
2. The study did not address suspended debris, focusing instead on items visible on the lakebed explain well.
3. The analysis was based on debris data collected in only three months (April, May, and June) across two years (2019 and 2024). This small sample size limits the statistical power to detect significant differences and reduces the robustness of the conclusions. Can explain better statistical approach.
4. In 2024, the reduced water clarity caused by algal blooms introduced detection bias, as the remotely operated vehicle (ROV) struggled to identify debris in murky conditions. This issue complicates comparisons between the two years. Explain better this issue.
Results
The results can be divided on statistical and results analyzed from underwater drone.
Conclusion
The conclusion is currently too brief and should be expanded. In this section, the authors are encouraged to address the following questions:
What is the significance of this research?
What new findings or insights does this study contribute to the field?
Overall, the paper is well-written. However, I now recommend a Major Revision.
Good luck to the authors!
Reviewer #1
Comments for author File: Comments.pdf
Author Response
Please find the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
Dear Authors,
Thank you for substantially revising the manuscript and for presenting the results of your research more fully. The topic of your research - development of a method for monitoring lake bottom pollution - seems to me to be very relevant and in demand in industrially developed regions. Publication of the results of your research in a highly rated journal will allow you to convey this important information to the general public.
I can recommend the manuscript for publication in its present form.
Reviewer 2 Report
Comments and Suggestions for Authors
The manuscript Monitoring Aquatic Debris in a water environment using a remote operating vehicle (ROV): A Comparative Study with implications of algal detection in Lake Como (Northern Italy) in my opinion, acceptable as presented.
General conclusion
Especially they improved the section Introduction and Conclusion and Literature. The number of references now is satisfying in accordance of the value and reputation of the Journal. Also authors changed almost 30% of the text and improved all parts of the paper. The Discussion and Conclusion sections new reflect the main advance of the manuscript. The methodology now is concise and well written.
So with the full reasonability I therefore recommend acceptance of this paper in its presented form.
Sincerely,
Reviewer#1
