Effects of Land Use Characteristics, Physiochemical Variables, and River Connectivity on Fish Assemblages in a Lowland Basin
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper has conducted an in-depth examination of the influence of physiochemical variables, land cover areas, and river connectivity on fish assemblages within a lowland basin, China. The findings reveal that upstream land use exerts a more pronounced impact on fish assemblages than river connectivity variables. Overall, the topic is interesting and suitable for this journal. The manuscript is well prepared. The method adopted in the study is reasonable and the analysis is informative. However, I still have some comments about the structures of the manuscript and hope they will prove beneficial to the authors.
1. One primary concern refers to the scientific significance of this work. While the introduction provides an overview of various studies related to fish assemblage, it lacks an explicit explanation of the study's unique contributions, such as methodological innovations or the significance of the topic. Additionally, the hypothesis is briefly mentioned in the discussion but should also be prominently featured in the introductory section to bolster the study's scientific relevance.
2. The cluster analysis, which forms the basis for subsequent comparisons, should be introduced in the "Statistical Analysis" section. The authors grouped all the sites into four clusters, but the methodology behind this grouping is not adequately explained. Please provide a detailed description of the methods employed in the cluster analysis.
3. The manuscript would benefit from a clearer separation between the results and discussion sections. Discuss should focus on elaborating and interpreting the results rather than presenting new results. For example, in paragraph 1 of section 4.2, multiple descriptions of results are interwoven with discussions. It is necessary to restructure the manuscript to enhance the clarity and coherence of these sections.
4. Although it is highlighted that land use exerts the strongest influence on fish assemblages, a more thorough explanation of the factors contributing to this dominance is expected. Why does land use emerge as the most significant factor, and are there site-specific reasons within the Chaohu basin that could elucidate this phenomenon? Additional discussion on this aspect is needed for a comprehensive understanding.
5. Ensure that figures and tables cited in the discussion are appropriately referenced. Furthermore, I noticed that both the Results and Discussion sections incorporate numerous supplementary tables. If these tables play a crucial role in the analysis, consider incorporating them directly into the main text as standalone tables rather than including them as supplementary materials.
Figure 1: Please include the names of the main rivers mentioned in section 2.1. Additionally, I recommend adding a map of China to illustrate the location and extent of the Chaohu Basin.
Comments on the Quality of English Language
Line 14 & 447: Add “a” before “local scale”
Line 83: Add “a” before “lowland plain”
Line 102: “a total of”
Line 115: add “and” before “Pielou’s equitability index”
Line 129 & 139: sites -> site
Line 135: Add “a” before “hydrologic sounding rod”
Line 151: was -> were
Line 167: remove “the”
Line 198: variables -> variable
Line 222: identity -> identify
Lines 342-344: I can not find the percentages from Figure 6
Line 447: varibales -> variables
Author Response
Dear Reviewer,
Thank you for your comments on our manuscript, "Effects of land use characteristics, physiochemical variables and river connectivity on fish assemblages in a lowland basin (Manuscript ID sustainability-2658665)" The manuscript has been revised, and responses to the comments follow (The modified part is marked with red font).
Response to Reviewer #1's comments and suggestions:
This paper has conducted an in-depth examination of the influence of physiochemical variables, land cover areas, and river connectivity on fish assemblages within a lowland basin, China. The findings reveal that upstream land use exerts a more pronounced impact on fish assemblages than river connectivity variables. Overall, the topic is interesting and suitable for this journal. The manuscript is well prepared. The method adopted in the study is reasonable and the analysis is informative. However, I still have some comments about the structures of the manuscript and hope they will prove beneficial to the authors.
1. One primary concern refers to the scientific significance of this work. While the introduction provides an overview of various studies related to fish assemblage, it lacks an explicit explanation of the study's unique contributions, such as methodological innovations or the significance of the topic. Additionally, the hypothesis is briefly mentioned in the discussion but should also be prominently featured in the introductory section to bolster the study's scientific relevance.
Response: Thank you for your comment and suggestion. Outcomes of this study will enhance our comprehension of the importance of multiple environmental variables and guide the protection and recovery of riparian zones (fish habitat). For example, he Grain for Green policy should be implemented in upper reaches, where fish population conservation could be improved and the key influential factors impacting riverine biodiversity might be mitigated after returning cropland to forests could be increased. The modified part is marked with red font in the section 5.
We added the hypothesis of this study in the last paragraph of “1. Introduction”. “however, in this study, we focused on river connectivity, land use, and some common physicochemical factors. Therefore, the aims of this study were to test the hypothesis that connectivity variables regulate fish assemblages. If not, which variables regulate fish as-semblages?”
2. The cluster analysis, which forms the basis for subsequent comparisons, should be introduced in the "Statistical Analysis" section. The authors grouped all the sites into four clusters, but the methodology behind this grouping is not adequately explained. Please provide a detailed description of the methods employed in the cluster analysis.
Response: Thank you for your comment and suggestion. For group sites with similar connectivity, Ward’s clustering method was used, based on Euclidean distances as a measure of similarity obtained from four connectivity variables (Link, BLink, CLink, and DLink). Clusters with Ward’s method are joined such that increases in within-group variance are minimized, which can be performed in using PAST 4.14 software. The modified part is marked with red font in the first paragraph of "2.4 Statistical Analysis".
3. The manuscript would benefit from a clearer separation between the results and discussion sections. Discuss should focus on elaborating and interpreting the results rather than presenting new results. For example, in paragraph 1 of section 4.2, multiple descriptions of results are interwoven with discussions. It is necessary to restructure the manuscript to enhance the clarity and coherence of these sections.
Response: Thank you for your comment and suggestion. We moved “fish taxa richness and diversity indices were not significantly related to all river connectivity variables (not shown in the text) and no significant difference existed among the connectivity groups (p>0.099, Table 4), fish assemblages significantly varied by connectivity groups (global R=0.089, p=0.026), particularly between Groups 3 and 4 and Groups 2 and 4.” from paragraph 1 of section 4.2 to the first paragraph of section 3.3, and “ROrder and BLink_Lf explain a fraction of the variance (3.0% and 2.6%, respectively).” from paragraph 1 of section 4.2 to the first paragraph of section 3.4. We also moved “Sites in Group 1 had the highest Width, Depth, and DO and even the highest pH values. Sites in Group 1 had the highest values of the connectivity variables (ROrder, Link, BLink, and DLink), local-size variables (river width, water depth, and DO), and U_Crop. The sites in Group 4 had the highest Elevation, U_Wood, and U_Grass; the lowest river width, wa-ter depth and U_Crop; and the lowest nutrient levels (e.g., TP, NO3--N, PO43+-P).” from paragraph 1 of section 4.1 to the first paragraph of section 3.2. The modified part is marked with red font in the MS.
4. Although it is highlighted that land use exerts the strongest influence on fish assemblages, a more thorough explanation of the factors contributing to this dominance is expected. Why does land use emerge as the most significant factor, and are there site-specific reasons within the Chaohu basin that could elucidate this phenomenon? Additional discussion on this aspect is needed for a comprehensive understanding.
Response: Thank you for your comment and suggestion. We added a more thorough explanation of land use which emerge as the most significant factor in the Lake Chaohu Basin. The conversion of land use from woodland to cropland and/or built-up land around streams may lead to changes in habitat destruction (e.g., poor water quality) and further cause the replacement of specialist species by generalist species and finally trigger the changes in fish abundance, distribution and diversity. Therefore, there may be a threshold, where a slight disturbance can significantly alter the state or development of the fish habitat, for the proportion of land use conversion that triggers changes in fish abundance, distribution and diversity. Furthermore, watershed land use are significantly related to hydrological connectivity, riparian, and habitat heterogeneity, all of which are critical factors that can direct influence the fish community composition, distribution, and diversity. The influence of land use could be amplified when these factors interact with nutrient loading and sedimentation from intensive human activities (e.g., agricultural activities). Besides, there is a long history of agricultural activities in the Lake Chaohu Basin from the Three Kingdom Period (220–265 A.D.) to the present. Due to the rapid population growth in recent decades in the Lake Chaohu Basin, the area and yield of cropland constantly increasing to meet the rapidly growing demand for crop production. Besides, Wang et al. found that a part of woodland has been converted into cropland and built-up land in the Lake Chaohu Basin, especially in the past ten years. Therefore rapid changes in land use have profoundly effect on river ecosystems in Lake Chaohu Basin. The modified part is marked with red font in the second paragraph of section 4.3.
5. Ensure that figures and tables cited in the discussion are appropriately referenced. Furthermore, I noticed that both the Results and Discussion sections incorporate numerous supplementary tables. If these tables play a crucial role in the analysis, consider incorporating them directly into the main text as standalone tables rather than including them as supplementary materials.
Response: Thank you for your comment and suggestion. We checked the figures and tables in the MS, and changed “Fig.” to “Figure” according to the Instructions for Authors of Sustainability. We ensure that figures and tables cited in the discussion are appropriately referenced. We have incorporated all supplementary tables directly into the main text as standalone tables. The modified tables are marked with red font in the MS.
6. Figure 1: Please include the names of the main rivers mentioned in section 2.1. Additionally, I recommend adding a map of China to illustrate the location and extent of the Chaohu Basin.
Response: Thank you for your comment and suggestion. We have added the names of the main rivers mentioned in section 2.1 and a map of China in Figure 1 to illustrate the location and extent of the Lake Chaohu Basin.
Comments on the Quality of English Language
7. Line 14 & 447: Add “a” before “local scale”
Response: Thank you for your thoughtful comment and suggestion. We have added “a” before “local scale” in the two sentences.
8. Line 83: Add “a” before “lowland plain”
Response: Thank you for your thoughtful comment and suggestion. We have added “a” before “lowland plain” in the MS.
9. Line 102: “a total of”
Response: Thank you for your thoughtful comment and suggestion. We have changed “a total” to “a total of” in the MS.
10. Line 115: add “and” before “Pielou’s equitability index”
Response: Thank you for your thoughtful comment and suggestion. We have added “and” before “Pielou’s equitability index” in the MS.
11. Line 129 & 139: sites -> site
Response: Thank you for your thoughtful comment and suggestion. We have changed “sites” to “site” in the two sentences.
12. Line 135: Add “a” before “hydrologic sounding rod”
Response: Thank you for your thoughtful comment and suggestion. We have added “a” before “hydrologic sounding rod” in the MS.
13. Line 151: was -> were
Response: Thank you for your thoughtful comment and suggestion. We have changed “was” to “were” in the MS.
14. Line 167: remove “the”
Response: Thank you for your thoughtful comment and suggestion. We have removed “the” in the first sentence of “2.3.3. River connectivity variables”.
15. Line 198: variables -> variable
Response: Thank you for your thoughtful comment and suggestion. We have changed “variables” to “variable” in the MS.
16. Line 222: identity -> identify
Response: Thank you for your thoughtful comment and suggestion. We have changed “identity” to “identify” in the MS.
17. Lines 342-344: I can not find the percentages from Figure 6
Response: Thank you for your thoughtful comment. The explanatory power for these environmental variables to the fish assemblages were calculated by the percentages of the selected variables to the total explanatory power, all of which can be gotten from the forward selection step in the Canoco 4.5 software. When CCA is run in Canoco software, these percentages do not appear in Figure 6. Therefore we did not listed them in Figure 6. We have supplemented the calculation process of these percentages in the “2.4. Statistical analysis” (the second paragraph from bottom).
18. Line 447: varibales -> variables
Response: Thank you for your thoughtful comment and suggestion. We have changed “varibales” to “variables” in the MS.
We have examined the mistakes in the article carefully and also checked the language. This paper was edited for proper English language, grammar, punctuation, spelling, and overall style by one or more of the highly qualified native English speaking editors at American Journal Experts (verification code ECE2-0986-9C2D-A50A-F36P). Thanks again for handling our work. If you have any questions, please do not hesitate to contact us.
Sincerely yours,
Zhiming Zhang and co-author
Email: [email protected]
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper is well-executed and well-written. Authors may cite two references that I have indicated in the marked MS, if appropriate. The marked MS is attached herewith.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer,
Thank you for your comments on our manuscript, "Effects of land use characteristics, physiochemical variables and river connectivity on fish assemblages in a lowland basin (Manuscript ID sustainability-2658665)" The manuscript has been revised, and responses to the comments follow (The modified part is marked with red font).
Response to Reviewer #2's comments and suggestions:
1. The paper is well-executed and well-written. Authors may cite two references that I have indicated in the marked MS, if appropriate. The marked MS is attached herewith.
Response: Thank you for your comment. We have cited two references that you have indicated in the marked MS.
Reference 9: Amarasinghe, U.S.; Welcomme, R.L. An analysis of fish species richness in natural lakes. Environ. Biol. Fish. 2002, 65(3), 327-339. And Reference 28: Amarasinghe, U.S.; De Silva, S.S.; Nissanka, C. Evaluation of the robustness of predictive yield models based on catchment characteristics using GIS for reservoir fisheries in Sri Lanka. Fisheries Manag. Ecol. 2002, 9, 293-302.
Details are as follows:
In the first paragraph of Introduction “Many natural factors caused by elevation gradients, such as temperature, precipitation, and flow velocity, co-determine species richness and species distribution patterns [5-9].” And “In addition, elevation, catchment area, and river longitudinal gradients primarily deter-mine the fish assemblages [9,12-16].”
In the second paragraph of Introduction “Excessive nutrient input and habitat degradation derived from land use changes (e.g., changes from woodland to cropland and/or built-up land) can reduce the species richness and diversity of fish communities [14,22-28].”
Besides, we also have reordered the references. And we have changed “The environmental variables with a significance 229 level of p<0.1 were chosen based on 9,999 Monte Carlo permutation tests (Zhang et al. 2018).” as “The environmental variables with a significance 229 level of p<0.1 were chosen based on 9,999 Monte Carlo permutation tests [13]”.
3. Change R2 as R^2 (R-square) in the second paragraph of “2.4. Statistical analysis”
Response: Thank you for your comment. We have changed R2 as R2.
We examined the mistakes in the article carefully and also checked the language. This paper was edited for proper English language, grammar, punctuation, spelling, and overall style by one or more of the highly qualified native English speaking editors at American Journal Experts (verification code ECE2-0986-9C2D-A50A-F36P). Thanks again for handling our work. If you have any questions, please do not hesitate to contact us.
Sincerely yours,
Zhiming Zhang and co-author
Email: [email protected]
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsEffects of land use characteristics, physiochemical variables and river connectivity on fish assemblages in a lowland basin by Zhang et al. is a very complete manuscript that includes habitat description, physical-chemical characterization, biological sampling and statistical analyses. I only have some general comments that I think could improve the quality of the paper:
If you are writing scientific names, please use the correct use from the Zoological nomenclature, e.g.: ‘Carassius carassius (Linnaeus, 1758)’. Apply this to all the scientific names in the text, or else just use the latin name without the author, but keep it the same way throughout the manuscript.
Regarding the capture of fish using your described method, was this approved by any ethics committee? Please include it as a statement
Specific comments:
Line 42: ‘can live and grow’…in a given area, right?
Line 42: what is ‘catchment area’?
Line 45: ‘reduced flow velocity stability’?
Lines 114-126: maybe you could add a statement of why are you calculating each of these diversity indices
Line 307: if you are writing scientific names, please use the correct use from the Zoological nomenclature, e.g.: ‘Carassius carassius (Linnaeus, 1758)’
Lines 365-371: here you are naming Orders (e.g.: Perciformes), please specifiy this, at least at the start of the sentence
Author Response
Dear Reviewer,
Thank you for your comments on our manuscript, "Effects of land use characteristics, physiochemical variables and river connectivity on fish assemblages in a lowland basin (Manuscript ID sustainability-2658665)" The manuscript has been revised, and responses to the comments follow (The modified part is marked with red font).
Response to Reviewer #3's comments and suggestions:
Effects of land use characteristics, physiochemical variables and river connectivity on fish assemblages in a lowland basin by Zhang et al. is a very complete manuscript that includes habitat description, physical-chemical characterization, biological sampling and statistical analyses. I only have some general comments that I think could improve the quality of the paper:
1. If you are writing scientific names, please use the correct use from the Zoological nomenclature, e.g.: ‘Carassius carassius (Linnaeus, 1758)’. Apply this to all the scientific names in the text, or else just use the latin name without the author, but keep it the same way throughout the manuscript.
Response: Thank you for your comment and suggestion. We apologize for any inconvenience caused by this confusion. We have used the latin name without the author and kept it the same way throughout the manuscript.
Details are as follows:
In the second paragraph of “3.3. Influence of river connectivity on fish assemblages”: “The SIMPER analysis revealed that the species that primarily contributed to the dissimilarity between Groups 3 and 4 were Carassius auratus (16.72% of contribution), Ctenogobius sp. (13.14%), Hemiculter leucisculus (11.45%), and Misgurnus anguillicaudatus (8.53%), while Ctenogobius auratus (18.10%), Ctenogobius sp. (14.24%), H. leucisculus (11.41%), and Acheilognathus barbatulus (6.10%) mostly contributed to the difference between Groups 2 and 4. In addition, Carassius auratus, Ctenogobius sp., and Hemiculter leucisculus were the dominant species and occurred at most of the sites throughout Lake Chaohu Basin.”
In the second paragraph of “3.4. Linking environmental variables to fish assemblages”: “Similarly, five species (such as Zacco platypus, Misgurnus anguillicaudatus, Ctenogobius sp., Pseudobagrus truncates and Odontobutis sinensis) were positively correlated to Elevation, U_Wood, and Flow. In other words, these species generally occurred in the upper reaches with high Elevation, U_Wood, and Flow. Moreover, Abbottina rivularis, Rhodeus lighti and Hypseleotris swinhonis were most frequently found in the upper reaches of high U_Grass and low ROrder. Bsides, Cobitis sinensis and Sarcocheilichthys nigripinnis were found in the upper and middle reaches with high DO.”
In the second paragraph of “4.3. Upstream land use and flow velocity play more important roles in the variation in fish assemblages”: “Similar results were found in this study, which showed a shift from herbivore (Rhodeus lighti), omnivore (Ctenogobius sp. and Zacco platypus) and primary carnivore (Abbottina rivularis, Hypseleotris swinhonis, and Odontobutis sinensis) fish assemblages in segments with the highest amount of woodland and grassland along the upper streams to omnivore (Hemiculter leucisculus and Pseudorasbora parva) and secondary carnivore (Channa argus and Cultrichthys erythropterus) fish assemblages in segments with the highest cropland and built-up land along the upper streams.”
2. Regarding the capture of fish using your described method, was this approved by any ethics committee? Please include it as a statement
Response: Thank you for your comment and suggestion. The animal study was reviewed and approved by the Animal Ethics Committee of the Anhui Normal University. We are very sorry we did not provide an ethics statement due to our carelessness. The Ethics Statement has been supplemented at the end of this manuscript.
Specific comments:
3. Line 42: ‘can live and grow’…in a given area, right?
Response: Thank you for your comment and suggestion. You are right. We have changed this sentence as “which also determine how many fish species can live and grow in a given area [6].”
4. Line 42: what is ‘catchment area’?
Response: Thank you for your comment. Here, catchment area means the area of a basin, therefore we have changed “catchment area” as “basin area” in the text.
5. Line 45: ‘reduced flow velocity stability’?
Response: Thank you for your comment. We have changed this sentence as “Excessive nutrient input and habitat degradation derived from land use changes (e.g., changes from woodland to cropland and/or built-up land) can reduce the species richness and diversity of fish communities [14,22-28].”
6. Lines 114-126: maybe you could add a statement of why are you calculating each of these diversity indices
Response: Thank you for your comment and suggestion. We added a statement in the MS, “In this study, the diversity, dominance, richness, and evenness indices of fish were considered to analyze the influence of hydrological connectivity on fish α diversity. Therefore, four commonly used indices, Shannon-Wiener index, Berger-Parker dominance index, Margalef's richness index, and Buzas and Gibson's evenness, were calculated for each site based on species abundance data.” We have checked the calculation processes of all indices and found that an index was written incorrectly, which mistakenly wrote “Buzas and Gibson's evenness index” as “Pielou’s equitability index” in the body. We apologize for this. The modified part is marked with red font in the MS.
7. Line 307: if you are writing scientific names, please use the correct use from the Zoological nomenclature, e.g.: ‘Carassius carassius (Linnaeus, 1758)’
Response: Thank you for your comment and suggestion. We apologize for any inconvenience caused by this confusion. We have used the latin name without the author and kept it the same way throughout the manuscript.
Details are as follows:
In the second paragraph of “3.4. Linking environmental variables to fish assemblages”: “Similarly, five species (such as Zacco platypus, Misgurnus anguillicaudatus, Ctenogobius sp., Pseudobagrus truncates and Odontobutis sinensis) were positively correlated to Elevation, U_Wood, and Flow. In other words, these species generally occurred in the upper reaches with high Elevation, U_Wood, and Flow. Moreover, Abbottina rivularis, Rhodeus lighti and Hypseleotris swinhonis were most frequently found in the upper reaches of high U_Grass and low ROrder. Bsides, Cobitis sinensis and Sarcocheilichthys nigripinnis were found in the upper and middle reaches with high DO.”
8. Lines 365-371: here you are naming Orders (e.g.: Perciformes), please specify this, at least at the start of the sentence
Response: Thank you for your comment and suggestion. We apologize for any inconvenience caused by this confusion. We rewritten this sentence. Due to the naming Order is not the main aims of this MS, we delete the naming Order. Details are as follows:
“Similarly, five species (such as Zacco platypus, Misgurnus anguillicaudatus, Ctenogobius sp., Pseudobagrus truncates and Odontobutis sinensis) were positively correlated to Elevation, U_Wood, and Flow. In other words, these species generally occurred in the upper reaches with high Elevation, U_Wood, and Flow. Moreover, Abbottina rivularis, Rhodeus lighti and Hypseleotris swinhonis were most frequently found in the upper reaches of high U_Grass and low ROrder. Bsides, Cobitis sinensis and Sarcocheilichthys nigripinnis were found in the upper and middle reaches with high DO.”
We examined the mistakes in the article carefully and also checked the language. This paper was edited for proper English language, grammar, punctuation, spelling, and overall style by one or more of the highly qualified native English speaking editors at American Journal Experts (verification code ECE2-0986-9C2D-A50A-F36P). Thanks again for handling our work. If you have any questions, please do not hesitate to contact us.
Sincerely yours,
Zhiming Zhang and co-author
Email: [email protected]
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript has improved a lot after revision. It's OK for publication in the recent version.
Author Response
Response to Reviewer #1's comments and suggestions:
The manuscript has improved a lot after revision. It's OK for publication in the recent version.
Response: Thank you for your comment and suggestion.
