Benthic Macroinvertebrate Diversity as Affected by the Construction of Inland Waterways along Montane Stretches of Two Rivers in China
Round 1
Reviewer 1 Report
Review
Paper title: Benthic macroinvertebrate diversity as affected by construction of inland waterways along montane stretches of two rivers in China.
The authors studied species the diversity of macrobenthic taxa in two rivers in relation to environmental factors and anthropogenic pressure expressed as different stages of constructing inland waterways. They found a negative impact of anthropogenic activity on benthic communities and concluded that restoration measures must be adopted to minimize negative consequences and restore impacted populations.
The authors have revised their initial paper according to my comments.
All these reasons explain the relevance of the paper by Peng Dou and co-authors submitted to "Water".
General scores.
The data presented by the authors are original and significant. The study is correctly designed and technically sounds. In general, the statistical analyses are performed with good technical standards. We authors conducted careful work which will attract the attention of a wide range of specialists focused on freshwater ecosystems and restoration of degraded habitats.
Major concerns.
Table 1. The authors should add a column with full identification of each code as they did in Table 2.
Table 2. The authors should add information about higher taxa (Oligochaeta, Gastropoda, Chironomidae…) and group species according to these higher taxa.
Specific comments.
L 37. Change “the fauna” to “fauna”
L 37, 49, 61, 64, 65, 86, 131, 134, 157, 169, 348. Change “macroinvertebrate” to “macroinvertebrates”
L 98. Change “Both of” to “Both”
L 100. Change “condition” to “conditions”
L 133. Change “expressed” to “was expressed”
L 136. Change “Ni is the numbers” to “Ni is the number”
L 150. Change “multiple tests was used” to “multiple tests were used”
L 151. Change “overview” to “an overview”
L 157. Change “Beside” to “Besides”
L 177, 178. Change “There is” to “There was”
L 181. Change “significant” to “significantly”
L 182, 196. Change “three groups” to “the three groups”
L 190. Change “enviromental parameters in study area including (a )the flow velocity in” to “environmental parameters in the study area including (a )the flow velocity in the”
L 191, 196. Change “Data are showed” to “Data are presented”
L 200. Change “five” to “five taxa”
L 206. Change “than that in group” to “than that in groups”
L 221. Add “Vertical bars show standard errors”.
L 235. Change “Table 3” to “Tables 1 and 2”
Author Response
Reviewer #1: The authors studied species the diversity of macrobenthic taxa in two rivers in relation to environmental factors and anthropogenic pressure expressed as different stages of constructing inland waterways. They found a negative impact of anthropogenic activity on benthic communities and concluded that restoration measures must be adopted to minimize negative consequences and restore impacted populations.
The authors have revised their initial paper according to my comments.
All these reasons explain the relevance of the paper by Peng Dou and co-authors submitted to "Water".
General scores.
The data presented by the authors are original and significant. The study is correctly designed and technically sounds. In general, the statistical analyses are performed with good technical standards. We authors conducted careful work which will attract the attention of a wide range of specialists focused on freshwater ecosystems and restoration of degraded habitats.
Response: Thanks so much for your encouraging words.
Major concerns.
Table 1. The authors should add a column with full identification of each code as they did in Table 2.
Response: We have revised Table 1 as suggestion.
Table 2. The authors should add information about higher taxa (Oligochaeta, Gastropoda, Chironomidae…) and group species according to these higher taxa.
Response: We have revised Table 2 as suggestion.
Specific comments.
L 37. Change “the fauna” to “fauna”
Response: We have revised the error.
L 37, 49, 61, 64, 65, 86, 131, 134, 157, 169, 348. Change “macroinvertebrate” to “macroinvertebrates”
Response: We have revised the error.
L 98. Change “Both of” to “Both”
Response: We have revised the error.
L 100. Change “condition” to “conditions”
Response: We have revised the error.
L 133. Change “expressed” to “was expressed”
Response: We have revised the error.
L 136. Change “Ni is the numbers” to “Ni is the number”
Response: We have revised the error.
L 150. Change “multiple tests was used” to “multiple tests were used”
Response: We have revised the error.
L 151. Change “overview” to “an overview”
Response: Revised.
L 157. Change “Beside” to “Besides”
Response: Revised.
L 177, 178. Change “There is” to “There was”
Response: Revised.
L 181. Change “significant” to “significantly”
Response: Revised.
L 182, 196. Change “three groups” to “the three groups”
Response: Revised.
L 190. Change “enviromental parameters in study area including (a )the flow velocity in” to “environmental parameters in the study area including (a )the flow velocity in the”
Response: Revised.
L 191, 196. Change “Data are showed” to “Data are presented”
Response: Revised.
L 200. Change “five” to “five taxa”
Response: Revised.
L 206. Change “than that in group” to “than that in groups”
Response: Revised.
L 221. Add “Vertical bars show standard errors”.
Response: We have added the sentence.
L 235. Change “Table 3” to “Tables 1 and 2”
Response: We have revised the error.
Reviewer 2 Report
This paper concerns the alteration of benthic macroinvertebrate assemblages related to construction and operation of inland waterways. In my opinion, this is a topic of great interest to contemporary management of inland running waters.
I think that the paper could be improved by considering the comments/suggestions listened below, where L is line-number in the .pdf file provided by the system.
INTRODUCTION
L 84-86: as an announced objective of the presented research, I expected details about a conservation plan for the restoration of benthic macroinvertebrate assemblages in the investigated river systems (see also below, Discussion section).
MATERIALS AND METHODS
L 97-114: I think that the basic hydromorphology of the investigated river reaches (e.g., channel slope, substrate size, etc.), and the rationale of the survey (e.g., why did you sample 2015 and 2016 only in September? How did you manage/analyze samples of different years? Why did you sample 7-9 sites per reach? Etc.) can be improved.
L 121-129: sampling areas and related positions are not clear to me.
In fact, each sampling site was 0.5 m × 0.5 m, but, from each sampling site, three samples were collected as three replications, each from an area 40 cm × 40 cm.
Please replace “Sauber” by Surber.
Did you sample the riparian zone or the main channel?
L 131-132: It is unclear to me what do you mean by “few were identified at taxa level”, maybe genus or family?
L 139-140: you collected three soil cores per sampling site, but I did not understand how did you analyze them, and what environmental variables were obtained and used in your following analyses.
DISCUSSION
Discussion is essentially limited to two points, repeated more than once:
- Construction/operation of inland waterways negatively affects abundance/diversity of macroinvertebrate assemblages
- Objectives of biological conservation, environmental protection, and habitat restoration need to be considered in contemporary planning/construction/operation of inland waterways
I agree with you, but I expected a more thorough discussion. For instance, a quantitative comparison of your data with literature data. Incidentally, I noticed that references of the last 5 years are nearly missing, I suggest updating your bibliography.
Additionally, some specific quantitative indications concerning feasible mitigation measures (and related expected outcomes) in the investigated river systems were also expected (see also above, Introduction section).
Author Response
Reviewer #2: This paper concerns the alteration of benthic macroinvertebrate assemblages related to construction and operation of inland waterways. In my opinion, this is a topic of great interest to contemporary management of inland running waters.
I think that the paper could be improved by considering the comments/suggestions listened below, where L is line-number in the .pdf file provided by the system.
INTRODUCTION
L 84-86: as an announced objective of the presented research, I expected details about a conservation plan for the restoration of benthic macroinvertebrate assemblages in the investigated river systems (see also below, Discussion section).
Response: Changes in streambed substratum habitats, improvement of river water quality, regulation of waterway operation intensity and even optimization of river hydrological regime have been proposed as measures for the restoration of benthic macroinvertebrates, but the effectiveness of these measures is difficult to evaluate because of little information addressing the mechanism of human disturbance on benthic macroinvertebrate communities. More research is required into the dynamics of benthic macroinvertebrate populations as influenced by such construction and by shipping traffic in inland rivers, and one objective of the present research was to establish a conservation plan for the restoration of benthic macroinvertebrates. We have added these sentences in Introduction (new line 89-94).
MATERIALS AND METHODS
L 97-114: I think that the basic hydromorphology of the investigated river reaches (e.g., channel slope, substrate size, etc.), and the rationale of the survey (e.g., why did you sample 2015 and 2016 only in September? How did you manage/analyze samples of different years? Why did you sample 7-9 sites per reach? Etc.) can be improved.
Response: In order to obtain more comprehensive data, we set up as many sampling points as possible. Our study was carried out in two mountainous stretches, so many riparian areas are difficult to access, bringing difficulties to sampling. We set up sampling points on each river with different number. We repeated the sampling for two years for the stability of the data, and the data was analyzed as replications (new line 104-105).
L 121-129: sampling areas and related positions are not clear to me. In fact, each sampling site was 0.5 m × 0.5 m, but, from each sampling site, three samples were collected as three replications, each from an area 40 cm × 40 cm.
Response: We have revised the errors and deleted the confusing sentences. This part was revised as “Benthic macroinvertebrate populations were sampled from parts of the river bank in contact with river water. From each sampling site in the riparian zone, three samples were collected as three replications, using a Surber net (15 cm depth), each from an area 40 cm × 40 cm; filtered through a 2 mm sieve, and the residue preserved in 5% (v/v) formaldehyde in plastic vials. The macroinvertebrates in the residue were handpicked using a dissection microscope at 10× magnification and preserved in 70% alcohol.” (new line 124-130)
Please replace “Sauber” by Surber.
Response: Revised.
Did you sample the riparian zone or the main channel?
Response: Benthic macroinvertebrate populations were sampled in the riparian zone. We have revised the errors and rewrote Methods part.
L 131-132: It is unclear to me what do you mean by “few were identified at taxa level”, maybe genus or family?
Response: We have revised as “few were identified at family level”.
L 139-140: you collected three soil cores per sampling site, but I did not understand how did you analyze them, and what environmental variables were obtained and used in your following analyses.
Response: We have revised the errors and deleted the confusing information. We did not use sediment samples in this study. The study rivers have similar riverside substrate, but the water quality conditions are quite different in the three stretches due to waterway construction (Figure 3). We forced on addressing the response of macroinvertebrate assemblages on water environmental variables (temperature, pH, dissolved oxygen, total dissolved solids, suspended solids, water velocity, total nitrogen, nitrate nitrogen, total phosphorus, chemical oxygen demand, and ammonium nitrogen).
DISCUSSION
Discussion is essentially limited to two points, repeated more than once:
Construction/operation of inland waterways negatively affects abundance/diversity of macroinvertebrate assemblages.
Objectives of biological conservation, environmental protection, and habitat restoration need to be considered in contemporary planning/construction/operation of inland waterways.
I agree with you, but I expected a more thorough discussion. For instance, a quantitative comparison of your data with literature data. Incidentally, I noticed that references of the last 5 years are nearly missing, I suggest updating your bibliography.
Response: As suggested, we have added the comparison to literature data and updating references as “The diversity and abundance of the macroinvertebrate community are lower in mountainous river, compared to river in plain or agricultural irrigated areas. Benthic macroinvertebrate communities in mountain rivers were more responsive to the waterway construction activities. If habitats are suitable, populations of benthic macroinvertebrate fauna can survive periods of intense external disturbance to the riparian ecosystem.”
Additionally, some specific quantitative indications concerning feasible mitigation measures (and related expected outcomes) in the investigated river systems were also expected (see also above, Introduction section).
Response: As suggested, we have added the relevant information in Introduction and Discussion as “Changes in streambed substratum habitats, improvement of river water quality, regulation of waterway operation intensity and even optimization of river hydrological regime have been proposed as measures for the restoration of benthic macroinvertebrates, but the effectiveness of these measures is difficult to evaluate because of little information addressing the mechanism of human disturbance on benthic macroinvertebrate communities. More research is required into the dynamics of benthic macroinvertebrate populations as influenced by such construction and by shipping traffic in inland rivers, and one objective of the present research was to establish a conservation plan for the restoration of benthic macroinvertebrates”. “Sediment accumulation during waterway construction depends mainly on the hydraulic conditions and on the type of slope of the riverbank. Protecting the slopes, providing alternative habitats within the waterway, and restoring sediment quality are some practical ways of conserving the diversity of benthic macroinvertebrate taxa. This study emphasizes the effect of water quality deterioration caused by waterway construction on benthic macroinvertebrates. Therefore, regulating the waterway operation pattern or purification of water quality will be effective measures to improve the macroinvertebrate community.”
Round 2
Reviewer 2 Report
I think that the revised version of this manuscript is improved compared to the previous draft. The Authors comprehensively and accurately considered the comments and suggestions provided, as also documented by the point-by-point responses.
Author Response
Dear Editor,
Thank you for the opportunity to revise our manuscript (water-1344923). We appreciated the constructive comments from the reviewers. Below, we describe the changes that we have made in response to the review. We trust that these changes will meet with your approval.
Sincerely,
Peng Dou and Tian Xie
Overall, I consider the discussion is poor. It is still very repetitive on statements that say inland waterway construction is detrimental for the abundance and diversity of benthic macroinvertebrates. Regarding the specific factors that can explain this lowering of abundance and diversity, there are statements that are not supported by the data you have provided in the results section. Primarily the effect of changes in the riparian vegetation and the hydrology. It is understood that these type of changes must have occurred, but you have not considered them as specific causative factors in your analyses, so there is no quantitative information on differences between sites in flow rates or amount of riparian vegetation. Therefore, we do not know how the contribution of these two factors compares to the water quality factors, traffic density and so on that you have used in your statistical analyses.
Response：Thank you very much for your suggestions. We have reorganized the Discussion. We deleted the parts that could not be supported by the data and results of this study. We also explain the causative factors and the reasons for not using factors of vegetation factors. The data of flow rates has been showed in Figure 2 (a) and information of riparian vegetation has been added in the overview of the study area (newline 113: There is very little vegetation in the bedrock or gravelly substrate of riverside).
Discussion section 4.2. is also quite repetitive, in the sense that you continuously repeat the idea of the need for conservation and restoration strategies to recover benthic macroinvertebrate communities. However, the recommendations given are very general, not directly based on specific results from your data analysis.
Response：Thanks so much for suggestions. We have removed the redundant and repetitive parts of the discussion.
Main recommendations
-Do not divide the discussion into subsections.
Response：We have revised as suggested.
- If possible, extend the analysis (in the results section) of the factors that can potentially affect the benthic macroinvertebrate abundance and diversity to include flow rate (or any other hydrological factor) and riparian vegetation abundance. Then discuss on which factors have been shown to contribute most in your case study. If the additional information is not available, in the discussion differentiate clearly the statements supported by your results and the statements that are speculative and should be studied more in depth to provide proper evidence.
Response：Two rivers with similar hydrogeological conditions were selected in our study, so there was no difference in the environmental background such as pH, temperature and flow velocity. There was no significantly difference in velocity between the two rivers (0.20 ± 0.02 m/s in Wuyang river and 0.22 ± 0.03 m/s in Zhangjiang river, P = 0.688, Figure 2a). We have extended the analysis in Figure 2 and result part. Riparian vegetation was not considered as a factor affecting macroinvertebrate community in this study, because the study area is mountainous rivers and the bedrock substrate failed to develop well plant communities. Whether the riparian vegetation damage caused by inland waterway construction is an important factor affecting macroinvertebrate community needs more in-depth studies. We have added the information about riparian vegetation in new Discussion.
- Regarding contents in section 4.2., summarize the information you have now, so that the text is not so repetitive and is much shorter.
Response：We have removed the redundant and repetitive parts in section 4.2.
Author Response File: 
Author Response.doc
