Sediment Legacy of Aquaculture Drives Endogenous Nitrogen Pollution and Water Quality Decline in the Taipu River–Lake System
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis is a relatively meaningful study, which has important practical significance for pollution control, restoration and protection of water quality in river and lake systems. Therefore, it is suggested that the manuscript be published after minor revision.
Figure 1 is too simple. As a manuscript published in international journals, the location of the research area needs to be more detailed.
Please add the detection limit of each chemical component in Section 2.2.
In Figure 2~4, some words are too small for readers to read.
KMO value is only 0.591, why does the author say it is suitable for principal component analysis?
Line 439-440, the author mentioned that the results of cluster analysis and principal component analysis are consistent, and they are divided into four categories. So are the results represented by these four categories consistent?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe reviewed manuscript (water-3699887) studied the nitrogen pollution in the Taipu River-lake system. Water and surface sediment samples were collected from the Taipu River and five interconnected lakes to analyze the forms, spatial distribution, and ecological impact of nitrogen. The results were statistically treated and discussed. The findings are worthy of publication and highly relevant to the water and sediment quality field. Please consider the following comments:
- Introduction; Although the introduction presents the problem background and the research gap, it should be supported by more recent and relevant literature. Please consider highlighting the novelty of this study.
- Figure 1; It would be better if this figure were modified to include a base map to show the exact location of the Taipu River in relation to Taihu Lake and China. Also, you should improve the figure quality (sample No. and lake names are not clear).
- Line 181; Results → Results and Discussion
- Line 187; Please mention these sampling seasons in Section 2.2.1.
- Figures 2, 3, and 4; Please improve the quality of these figures (horizontal axis labels are not clear).
- Figure 6; This is not an important figure, just refer to the eigenvalues in the presentation and discussion of the PCA.
- Please discuss the practical implications of the study findings or recommend specific sediment management strategies.
- Study limitations should be discussed.
- The conclusions section is consistent with the presented findings, but you should strengthen it with recommended future research.
- The references are up to date, but there are many recent key regional studies on nitrogen pollution in lake systems.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript presents a study of a longitudinal series in a river in an area with ponds and lakes in which the quality of the water and that of the sediment is compared, focusing on the content of nitrogen and phosphorus as elements indicating quality.
The manuscript is well presented and written in the parts that contain a scientific article, but I have some considerations about it:
It would be necessary in the introduction to describe other studies where analysis of water and sediment samples has been carried out in order to compare the results obtained here with other places already studied, which will allow us to know if the presence of the elements studied is greater or lesser in similar circumstances. With only a few references, the introduction is poor and very limited to the study area.
The objectives of the study and its contribution to scientific knowledge are not clear; The final part of the introduction should be written indicating these aspects.
The methodology is well described and allows the reproducibility of the tests and results process. But it is proposed to indicate in detail what is the depth of sediment that is taken with the dredger. If the sedimentation rate is as high as indicated by 4.2 cm/year, it is possible that the analyses have only been made of the content of the last year at some points, so the results would present a limitation in terms of their applicability in places where sedimentation is the usual one of a few millimeters per year.
Some details about the water should be provided, such as the depth of the sampling site, if there is a current that allows the body of water to be known.
It would be interesting to know the granulometry of the sediment, even if it were approximate; A sandy bottom is not the same as a bottom with fine materials. Also if it is oxidized or in a reduced state.
In the results, it would be desirable to have a diagram of the nitrogen cycle indicated by the authors at the different times of the year or environmental conditions. The correlations they present on nitrate, ammonium, oxygen and ORP are what can be expected as presented by the books that study these variables, so there is nothing new. That is why it is convenient to present interesting details of the lake and river areas, if they exist.
Paragraph 542-556 presents precisely the need to know which sedimentary layer is studied. If the processes occur in the first two centimeters, since sedimentation is so high, it is likely that only what happens in the very recent sediment from the previous season is studied, nothing more likely. It is therefore convenient to clarify these aspects.
Finally, the biota existing in the surface layer could contribute to the movement of sediment and changes in the composition of the elements studied. It would be desirable to know if macroinvertebrates exist on the bottom or are absent due to excess pollution.
Conclusions could be written in paragraph style without including a prominent headline.
The supplementary material is very extensive, perhaps the main table of results should be an annex to the manuscript, not a separate document.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI appreciates the authors' point-by-point responses. No more comments.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have made significant contributions to the manuscript following the recommendations made in my review. In my opinion, the manuscript is ready for publication, as all the suggested proposals have been accepted and incorporated into the text.
