Empirical Characterization Factors for Life Cycle Assessment of the Impacts of Reservoir Occupation on Macroinvertebrate Richness across the United States
, Katrine Turgeon 2, Francesca Verones 3, Daniel Boisclair 4, Cécile Bulle 1,5 and Manuele Margni 1,6Round 1
Reviewer 1 Report
Dear authors and Editor,
well, after a rejection-and-resubmission, following quite many comments, questions, concerns etc. by three reviewers, I think I will not insist on further reviewing. As with the previous version, I again started writing some questions and concerns but all of them were answered (and removed from my comments) after reading the 4.3. Limitations section.
I strongly however advise the authors to re-check section 2.2.1. to make it clearer (maybe my following minor comments will help on this), because (in my personal opinion) if the reader cannot understand the methods, he/she will probably not read the results/discussion, and not cite the document .
Overall, this version is ok. I may not agree with some assumptions made to enable this study but all assumptions are reported and discussed as limitations and thus, the overall results and conclusions are valid, given the weaknesses due to lack of data, which have been properly highlighted.
Anyway, this is an interesting study with interesting findings.
Kind regards,
TITLE
The title is fine. I suggest the following generalization, but it’s your choice of course:
Empirical characterization factors for Life Cycle Assessment (LCA) of the impacts of reservoir occupation on macroinvertebrates across the United States
INTRODUCTION
Line 83. There is no need for a footnote since you define ‘occupation’ again in line 92. I suggest rephrasing line 83 as follows: ‘The impacts of transformation of a river into a reservoir (and its subsequent occupation by the reservoir for a given amount of time) on ecosystem quality have received little attention in LCA’.
MATERIALS AND METHODS
Line 114. The USEtox model [40], for example, builds such mechanistic … [Note: I assume the USEtox model is one of several similar software but if it’s the only one available, just ignore my suggestion here].
Line 134. I saw in literature it is written this way but I honestly cannot understand what this m2.yr/m2.yr actually is. If it means ‘PDF.m2.yr per m2.yr of land occupied’, there should be some parentheses… Never mind, since it is ‘officially’ written this way, you can just leave it as is.
I will try to re-write the section about macroinvertebrates because I think I do not understand it very well as it is. Don’t change anything unless you agree with my interpretation. The information in your text is there but difficult to ‘absorb’.
2.2.1. Macroinvertebrate taxa richness
Macroinvertebrate taxa richness data for reservoirs (n=134 impacted sites; after impoundment) and streams/rivers (n=2062 reference sites) were extracted from two nation-wide datasets as follows:
(1) Reservoirs (impacted sites; n=134): We used the 2012 National Lake Assessment (NLA) dataset, which is a United States Environmental Protection Agency (USEPA) effort that surveys 134 ponds, lakes and reservoirs in the United States, as well as their associated biological, chemical, physical and recreational characteristics [46]. From this dataset, we retrieved macroinvertebrate taxa richness (RICHNESS; taxonomic resolution at the genus level, except for oligochaetes, mites, and polychaetes, which were identified to the family level, and ceratopogonids at the subfamily level; [47]), a unique identifier (UID) for each reservoir, the latitude (LAT), longitude (LON), the ecoregion (ECO), and a suite of environmental variables (Table A1) (Figure 1).
(2) Rivers/streams (reference sites; n=2062): We used the 2008-2009 National Rivers and Streams Assessment (NRSA) dataset, a USEPA initiative that surveys the biological, chemical, physical, and recreational characteristics of 2062 river/stream sites across the United States [49].
Within a space-for-time substitution approach [48], we used the macroinvertebrate richness values in river and stream sites (from the NRSA dataset) around each reservoir as reference values against which the reservoir macroinvertebrate richness values (from the NLA dataset) would be compared to derive the PDFs.
So, was it that simple? 2062 sites from NRSA 2008-2009 were assigned to ecoregions; 134 reservoir sites from the NLA 2012 dataset were assigned to ecoregions. Using the NRSA dataset, mean richness was calculated for each ecoregion and for the USA as a whole. Using the NLA dataset, mean richness was calculated for each ecoregion, for the USA as a whole and for each reservoir. If I understood this correct, then we are ok, but it took me hours of reading and reading to understand it. Maybe you could reduce unnecessary talking. You could also leave your text intact but I strongly suggest a short revision of this section before finalizing your manuscript. Anyway, again, this is only a suggestion, not an obligation :)
Author Response
Reviewer 1: Dear authors and Editor,
well, after a rejection-and-resubmission, following quite many comments, questions, concerns etc. by three reviewers, I think I will not insist on further reviewing. As with the previous version, I again started writing some questions and concerns but all of them were answered (and removed from my comments) after reading the 4.3. Limitations section.
I strongly however advise the authors to re-check section 2.2.1. to make it clearer (maybe my following minor comments will help on this), because (in my personal opinion) if the reader cannot understand the methods, he/she will probably not read the results/discussion, and not cite the document.
Overall, this version is ok. I may not agree with some assumptions made to enable this study but all assumptions are reported and discussed as limitations and thus, the overall results and conclusions are valid, given the weaknesses due to lack of data, which have been properly highlighted.
Anyway, this is an interesting study with interesting findings.
Kind regards,
TITLE
Point 1: The title is fine. I suggest the following generalization, but it’s your choice of course: Empirical characterization factors for Life Cycle Assessment (LCA) of the impacts of reservoir occupation on macroinvertebrates across the United States
*** Answer 1: We thank the reviewer for its comments and suggestions on the earlier version of the manuscript. As we are given the choice, we wish to keep the title as it is. It is important for the authors that a notion of biodiversity, richness in this case, is introduced right from the beginning.
INTRODUCTION
Line 83-85. There is no need for a footnote since you define ‘occupation’ again in line 92. I suggest rephrasing line 83 as follows: ‘The impacts of transformation of a river into a reservoir (and its subsequent occupation by the reservoir for a given amount of time) on ecosystem quality have received little attention in LCA’.
*** Answer Line 83-85: We modified the sentence as per the reviewer’s suggestion and deleted the footnote.
MATERIALS AND METHODS
Line 115. The USEtox model [40], for example, builds such mechanistic … [Note: I assume the USEtox model is one of several similar software but if it’s the only one available, just ignore my suggestion here].
*** Answer Line 115: We added “[…], for example, […]”, as the USEtox model is one of several similar initiatives that uses the particular type of model characterization, which was rightly pointed out by reviewer 1.
Line 134. I saw in literature it is written this way but I honestly cannot understand what this m2.yr/m2.yr actually is. If it means ‘PDF.m2.yr per m2.yr of land occupied’, there should be some parentheses… Never mind, since it is ‘officially’ written this way, you can just leave it as is.
*** Answer Line 134: We understand the reviewer’s point, however no changes were made as this is the official way the equation is written in the literature.
I will try to re-write the section about macroinvertebrates because I think I do not understand it very well as it is. Don’t change anything unless you agree with my interpretation. The information in your text is there but difficult to ‘absorb’.
2.2.1. Macroinvertebrate taxa richness
Macroinvertebrate taxa richness data for reservoirs (n=134 impacted sites; after impoundment) and streams/rivers (n=2062 reference sites) were extracted from two nation-wide datasets as follows:
(1) Reservoirs (impacted sites; n=134): We used the 2012 National Lake Assessment (NLA) dataset, which is a United States Environmental Protection Agency (USEPA) effort that surveys 134 ponds, lakes and reservoirs in the United States, as well as their associated biological, chemical, physical and recreational characteristics [46]. From this dataset, we retrieved macroinvertebrate taxa richness (RICHNESS; taxonomic resolution at the genus level, except for oligochaetes, mites, and polychaetes, which were identified to the family level, and ceratopogonids at the subfamily level; [47]), a unique identifier (UID) for each reservoir, the latitude (LAT), longitude (LON), the ecoregion (ECO), and a suite of environmental variables (Table A1) (Figure 1).
(2) Rivers/streams (reference sites; n=2062): We used the 2008-2009 National Rivers and Streams Assessment (NRSA) dataset, a USEPA initiative that surveys the biological, chemical, physical, and recreational characteristics of 2062 river/stream sites across the United States [49].
Within a space-for-time substitution approach [48], we used the macroinvertebrate richness values in river and stream sites (from the NRSA dataset) around each reservoir as reference values against which the reservoir macroinvertebrate richness values (from the NLA dataset) would be compared to derive the PDFs.
So, was it that simple? 2062 sites from NRSA 2008-2009 were assigned to ecoregions; 134 reservoir sites from the NLA 2012 dataset were assigned to ecoregions. Using the NRSA dataset, mean richness was calculated for each ecoregion and for the USA as a whole. Using the NLA dataset, mean richness was calculated for each ecoregion, for the USA as a whole and for each reservoir. If I understood this correct, then we are ok, but it took me hours of reading and reading to understand it. Maybe you could reduce unnecessary talking. You could also leave your text intact but I strongly suggest a short revision of this section before finalizing your manuscript. Anyway, again, this is only a suggestion, not an obligation :)
*** Answer 2.2.1: We have improved section 2.2.1, inspired by reviewer 1 suggestion. We mostly moved sentences around to enhance reading flow and overall understanding of the method, as well as tried to delete unnecessary words/sentences. We think it is easier to “absorb” in this revised version.
Reviewer 2 Report
Dear Authors,
I can see that the manuscript is improved a lot after these revisions. It is a great job, indeed. I have a minor suggestion for your consideration.
Please consider moving the supplementary Figure A1 and A3 to main documents, rather than keeping them here.
The rest is fine.
Author Response
Reviewer 2 : Dear Authors,
I can see that the manuscript is improved a lot after these revisions. It is a great job, indeed. I have a minor suggestion for your consideration.
Please consider moving the supplementary Figure A1 and A3 to main documents, rather than keeping them here.
The rest is fine.
*** Authors: We thank the reviewer for its comments and suggestion on the earlier draft of the manuscript. In light of the previously made comments, we think the reviewer 2 wants Table A1 (there was never any mention to move Figure A1 to the main manuscript) and Figure A3 to be moved to the main text. Assuming this is right, we proceeded to move Table A1 and Figure A3 to main manuscript and update tables and figures’ numbering.
Reviewer 3 Report
I have gone through this revised version as well as through authors comments to my previous concerns outlined in the previous version. Overall, I my satisfied with the comments and revision provided by the authors, while this version being much improved over the original submission.
Author Response
Reviewer 3: I have gone through this revised version as well as through authors comments to my previous concerns outlined in the previous version. Overall, I my satisfied with the comments and revision provided by the authors, while this version being much improved over the original submission.
*** Authors: We thank the reviewer for its kind comments on the earlier draft of the manuscript. No further revisions were requested by reviewer 3 on this subsequent version of the manuscript.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Dear authors and Editor,
this article calculates the potentially disappeared fraction of species (PDF) using riverine and reservoir macroinvertebrate richness, to be used for assessing macroinvertebrates-based ecological impact scores of reservoir occupation in life cycle assessments. The concept is interesting and, as the authors are native English speakers, reading is fine. But I have several concerns that should be addressed if this article is to proceed to review/publication. My major concern is that I/the reader was not able to check the validity of the results (the PDFs provided) because crucial information is missing (i) in the Materials and Methods on how macroinvertebrate sampling was carried out within the NLA and NRSA campaigns. Was the same macroinvertebrate sampling area sampled over the same duration? Was the RIVPACS 3-min kick sampling method used in both campaigns? This is not mentioned and if the NLA and NRSA sampling methods are different, then the whole river-reservoir comparisons may not be valid; (ii) the authors showed only the PDFs but not the mean riverine richness vs the mean reservoir richness, from which the PDFs have been derived. Based on the above, the discussion is much speculative on what could be the reason for observing the specific PDFs but we cannot conclude on anything; but maybe we could if this information was provided.
The authors further tend to write long sentences justifying why they did not apply a specific method or speculating without concluding. Just focus on what you did, describe it in detail in the Materials and Methods and discuss your findings focusing not much on what previous literature suggests but on where your results contribute. Currently, there is a lot of discussion on ‘the inability to conclude, caution when interpreting’ etc. and a large ‘limitations’ section. Shift the focus of the discussion from discussing the limitations of your study to promoting the advantages that LCA studies will gain by incorporating your macroinvertebrates-based PDF (for example, as you say they can complement the fish-based PDFs or they can be used when fish species are not present in a stream/river).
Please note that I selected 'Major Revision' but a 'Major-Major Revision' is actually required.
Kind regards,
DETAILED COMMENTS
TITLE
Why not changing your title to describe what you actually did instead of generally talking about biodiversity etc.? It is your choice of course but I suggest:
- Empirical LCA characterization factors assessing the impact of reservoir occupation on macroinvertebrate richness across the USA
- Empirical characterization factors assessing the ecological impact of reservoir occupation in LCAs using benthic macroinvertebrates
Or something similar.
INTRODUCTION
Lines 40-43. These ‘i.e.’s do not look so nice and they can be removed without losing the meaning. So, ‘The extraction (withdrawal or abstraction), the regulation of water flow by dams (storage reservoirs for drinking water, flood control and energy production), or the water diversion by channels for irrigation or navigation, has …’.
Line 72. … decision-making (life cycle assessment; LCA) …
Lines 79-80. … its entire life cycle from resource extraction to end of life (ISO, 2006).
Line 82. … product’s …
Line 90. … of species (PDF), which can also sometime account for time and space, is recommended …
Lines 92-93. … a reservoir (the original river bed …
Line 98. … on fish (Turgeon et al., 2019) …
Line 99. … richness curves, such as species-discharge relationship (SDR; Dorber et al., 2019) or species-area relationship (SAR).
Line 103. … impoundment (the river bed occupation …
Line 113. … I do not agree with the ‘complementary to fish’ statement. Macroinvertebrates have long been used as stand-alone ecological indicators. Within a holistic (ideal) perspective, all biotic elements of the aquatic ecosystem should be studied, not hierarchically (not prioritizing fish first and other elements next) but simultaneously. So, I would rephrase to either ‘ … organism (macroinvertebrates) and the use …’ or ‘The originality of this study relies (i) on the choice of a new group of aquatic organisms (macroinvertebrates), which, within a holistic perspective, should be monitored together with other types of organisms, such as fish and aquatic vegetation, and (ii) the use of empirical values of richness instead of model predictions’. Note: Please correct my English since I am not a native speaker.
MATERIALS AND METHODS
Line 117. I am not an expert in LCA but shouldn’t this be titled ‘Life-cycle impact assessment framework’?
Line 118. CFs are determined by models, either based on … nature that link inventory flows (emissions of pollutants, the extraction/consumption of resources or a change of land use) to impact indicators, or on empirical observations …
Line 128. Two categories of ecological quality impact-indicators exist. The first one … temporary loss of species … (the potentially disappeared fraction of species over a given area and time; Joliet et al., 2003) or …
Line 132. … of the absolute species loss.
Line 140. … to assess the occupation of a water body, in surface-time units (m2·yr).
Line 144. Previously you said you used the first category (expressed in PDF·m2·yr) and here you say ‘expressed in PDF units. Also, the way this implicit equation is written may be mistaken for . Maybe write it as but again, what’s the point of this writing style? I would rephrase as follows: ‘In our study, the CF is the observed change in taxa richness, with respect to a reference macroinvertebrate community, multiplied by the inventory flow (m2 of water body occupied for a year) to get an impact score expressed in PDF·m2·yr’. Note: Saying that ‘m2·yr of water body occupied for a given time’ is a bit confusing; since you already multiplied m2 by yr you obviously refer to annual occupation.
Lines 147-157. This is quite unnecessary; why should you justify why you did not measure ‘something’? It is obvious that there would be a reason related with data probably. Just focus on what you did, not what you did not. I would end this paragraph by ‘In this study we did not measure the ecological impact of water body transformation but only that of water body occupation (although both impacts are complementary) due to lack of available post-transformation, water-body recovery data’.
Line 159. … the difference in taxa richness between reference macroinvertebrate communities from unpolluted rivers and impacted ones (from reservoirs) to develop …
Line 162. See my comment for line 144 and adapt accordingly.
2.2.1 Macroinvertebrate richness. You tend to use many words and unnecessary justifications to describe specific ‘things’, and particularly ‘things’ you did not apply. Throughout the Materials and Methods, use less words and only describe what you applied. I will rephrase this section based on what the reader expects, please correct once again my non-native English usage.
‘Macroinvertebrate richness data (taxonomic resolution: genus level except for oligochaetes, mites and polychaetes, which were identified to the family level and ceratopogonids to the subfamily level; USEPA, 2017) were extracted for 148 reservoirs across the United States (Figure 1) from the 2012 National Lake Assessment (NLA), a United States Environmental Protection Agency (USEPA) effort to statistically survey ponds, lakes and reservoirs in the USA and their associated biological, chemical, physical and recreational properties (USEPA, 2015a). A unique reservoir identifier, the latitude, longitude, the ecoregion and a suite of environmental variables (Table A1) were also retrieved from the NLA/2012 dataset. As no macroinvertebrate richness information was available for pre-impoundment conditions, we applied the space-for-time substitution approach (Pickett, 1989) using the 2008-2009 National Rivers and Streams Assessment (NRSA) dataset, a similar to the NLA effort focused on streams and rivers (USEPA, 2015b). The NRSA/2008-2009 dataset was used as a reference for pre-impoundment macroinvertebrate richness, assuming that richness in streams and rivers of a reservoir’s surrounding area would be comparable to what would have been found in a river prior to its transformation and occupation by a reservoir. The same environmental and physical variables were further retrieved for 2121 rivers and streams across the USA from the NRSA/2008-2009 dataset (Figure 1)’. Note: All other information given is not necessary, but a brief description (two lines) of the space-for-time approach would be. Also, since you are referring to ‘reservoirs’, isn’t it by default that you are referring to ‘impacted sites’?
Line 172. … macroinvertebrate richness … Note: Do you mean ‘at the genus level’? Also, was the same macroinvertebrate sampling scheme applied at the NLA and NRSA datasets? To compare the two datasets, you need to ensure that you compare macroinvertebrate richness sampled over the same sampling area and time/duration, otherwise the samples are not comparable.
2.2.2 Ecoregions. Similarly to my comments for 2.2.1 you could rephrase as follows: Reservoirs and rivers/streams were distributed across nine ecoregions, a priori defined by Omernik (1987) and Herlihy et al. (2008) based on similarities among environmental characteristics, such as climate, vegetation, soil types and geology, and macroinvertebrate assemblages (Figure 1): Coastal Plains (CPL), Northern Appalachians (NAP), Northern Plains (NPL), Southern Appalachians (SAP), Southern Plains (SPL), Temperate Plains (TPL), Upper Midwest (UMW), Western Mountains (WMT) and Xeric (XER). This ecoregion-based aggregation was adopted for both the NLA and NRSA surveys (USEPA, 2016). Land cover and human-pressure related variables were also extracted for each ecoregion (USEPA, 2016; Table A1).
2.2.3. Native riverine taxa identification. I don’t understand what you did here. You used the NRSA dataset as a reference dataset. Then you say ‘using only native …’; but did you actually use only native riverine taxa? Why not just measuring your reference richness based on all the taxa found in a riverine site? Comparing to a mean reference in each ecoregion? Wouldn’t it be more valid if this mean reference was calculated from NRSA samples around a specific (and fixed) radius of each reservoir, to avoid land-use related implications?
2.2.4. PDFs calculation
For the PDFusa do you mean one observation per river/stream sample (in total 2121 samples), averaged over the US? Did you compare one single value for RICHNESSrivers-usa against one single value for RICHNESSreservoirs-usa? If this is the case, the result may not be that informative since it aggregates samples from a very wide geographical area.
2.3.1. Regionalization and ANOVA. Here you also use many sentences that repeat the same thing to describe one specific method (ANOVA). Also, this section could simply start from line 260, further removing repeating parts.
Rest of Materials and Methods. The same comments on removing unnecessary sentences and avoiding repetition applies for the rest of this section.
RESULTS
You should somehow include in your results presentation, not only the PDFs, but also the x (riverine mean richness) and y (reservoir mean richness), otherwise the reader cannot confidently reach the conclusions you have reached. This would be especially useful in supporting and explaining/discussing the results shown in 3.3. Figures 2 and 3, and possibly Table 1 should be adapted accordingly (see below).
Lines 308-315. A total of 975 riverine macroinvertebrate taxa were inventoried … United States. The mean riverine taxa richness per ecoregion varied from 25.9 ± 13.3 to 44.6 ± 15.7 (mean ± standard deviation) (Table A3). The mean reservoir taxa richness per ecoregion varied from … Our empirically derived PDFs showed an impoundment-induced loss in macroinvertebrate taxa richness in the US, following a longitudinal gradient … At the USA scale, 26% of … vanished in response to river impoundment (PDFusa = 0.255 ± 0.010) (mean ± standard error) (Table 1; Figure 2).
Lines 315-318. At the ecoregion scale, six out of nine ecoregions (67%) showed statistically … taxa, with PDFs varying from … to 0.472 ± 0.027. One ecoregion (CPL) showed significant increase in macroinvertebrate richness (PDFCPL = -0.26 ± 0.053) (Table 1; Figure 2). PDFs in most …
Line 323. … macroinvertebrate taxa (Table A3). Note: Please correct this throughout the text; there is no need to specifically direct the reader inside figures and tables; just mention the table or the figure.
Figure 2. For each ecoregion, instead of showing only the PDF bar, show three bars (x, y, PDF). Change the y-axis range to -0.5 <-> 0.5 (and possibly move the USA ecoregion map to the bottom-right part of the plot).
Line 336. Remove ‘i.e.’.
Line 337. … PDFres (Figure 3; Table A4). Note: Similarly to the comment for line 323.
Lines 338-343. Remove the ‘i.e.’s.
Line 354. … = 0.434; p<0.001) …
Line 355. … trophic state (either oligotrophic or eutrophic; 11%) …
Figure 3. The blue-green colors are not much visible. I suggest instead of one big plot, show us three smaller plots; one with the sqrt(elevation) vs x (mean riverine richness) for the eutrophic and oligotrophic reservoirs (choose more visible different colors); a second one with sqrt(elevation) vs y (mean reservoir richness) for the two reservoir types; and a third one with the sqrt(elevation) vs PDFs for each type. Note: How is it explained that your blue line starts below zero when your most close to zero oligotrophic PDF is at approx. x=15;y=0.8? Shouldn’t we expect a straight line starting from somewhere around PDF=0.6?
DISCUSSION
Line 384. What do you mean ‘consistent across the three spatial scales’?
Lines 386-387. … to evaluate the potential ecological impact of reservoir occupation for a specific reservoir … Note: I don’t understand the ‘ecosystem quality area of protection’ but if it is used in LCA-based terminology then you may keep it as is.
Line 391. But in line 356, surface area accounted for < 1%. Why to include this variable?
Lines 407-425. This discussion is not based on your results but on your experience and previous literature on the hydrological/physical differences between the eastern and western ecoregions. Based on your results you cannot conclude on why there is such PDF difference, and this part should be removed but if you included the mean riverine richness vs the mean reservoir richness for these ecoregions, you could develop a more valid discussion here.
4.2. Trophic state. Again, your discussion here would have more meaning if we could compare the mean riverine vs mean reservoir richness between oligotrophic and eutrophic reservoirs. With only the PDF available, you and I can just speculate.
4.3. Surface area. If surface area does account for <1% of the variation, I would not include it in the analysis. And similarly to sections 4.1 and 4.2, you discuss but don’t conclude. If you re-read it, all these sections speculate on possible reasons for the observed trends but end with ‘information is not available to allow … caution is needed when interpreting this result … no hypotheses can be drawn etc.’.
Finally, I think that this journal requires the references to be numbered and only use the numbers in the main text, please check this upon possible resubmission.
Reviewer 2 Report
Manuscript title: Potential impacts of river impoundment on biodiversity in LCA: an empirical model building on freshwater macroinvertebrate richness
Manuscript Number: sustainability-827713
First, this is within the scope of this journal. However, English language description is a big issue in this manuscript.
Title:
The title must be revised. It contains an acronym which is not well-know.
Abstract:
L 19-20: This is ambiguous. Please open the abstract in way that it gives the main idea. What is “transformation and occupation of a river bed by a reservoir”? I think something is missing here.
L 20-24: This is jumbled up. Please simplify it.
You are confused between the terms of reservoir and impoundments. I think it is better to be consistent with one.
L 29: What is following impoundment? I think this is bit unclear. I feel that you mean “after appearance of impoundment”
The conclusions need more clarifications.
Please enrich with more of your findings and less of the methodologies used.
Introduction:
L 40: Extraction or abstraction? This is not appropriate here. Normally extraction is for groundwater.
The introduction is too long and scattered.
The last paragraph mostly belongs to methods.
Please revise your objectives.
Materials and Methods:
L 117-164: This section is merged with more details that are more like theoretical background. Therefore, you need to take care of it. Please make it brief and useful so that it can be followed by the researchers in future.
L 197-200: Please enlist all the potential limitations under a separate section.
L 200-202: Revise this sentence.
I feel that the methodology is too detailed. I feel that you need to consider moving some of the less important details to the supplementary section.
Please cut short the methods section.
Results
The results are aptly described. However, it is advisable to merge the results and discussions section.
Please consider moving the supplementary tables to the main results section.
Discussion:
L 375-377 & L 397-399: The information is repeated.
L 429-435: What could be the potential reason for this? Please provide more details on this as well.
L 443-444: The sentence is incomplete.
The description of limitation is very valid.
Overall, discussion section is well written.
Figures and Tables:
Figure 1. The legends are missing for map.
Move table 1 of supplementary section to the main manuscript.
Same for table 2 of the supplementary section.
Move the Figure A1 to the main manuscript.
Overall, figures and table are suitable and supportive.
Conclusions
The conclusions are okay.
References:
The references are relevant.
Reviewer 3 Report
GENERAL COMMENTS
I found this study well written and structured, easy to read with well-defined objectives, about an issue of interest to a wide audience, dealing with the potential impacts of river impoundment on biodiversity in lifecycle assessment, focusing on macroinvertebrates at different spatial scales. There are some minor comments below the need clarification, should the authors want to use them to improve their manuscript.
SPECIFIC COMMENTS
Title – provide full name for LCA in the title.
L155- “we don’t have this information”. Perhaps better to say it is presently not available for the study.
L159-160 – “between natural reference ecosystems (i.e., rivers)”. When you say natural reference ecosystems, it is supposed the rivers to be pristine or least with low human disturbance. Is it the case? To these rivers have other pressures such as point source pollutions, urbanization, etc.?
L200 – provide full name for these acronyms.
Fig. 1 – Provide a scale and indication of the north.
L217 – Remove “some”.
L247 - plural for “stream”.
L277-281 and throughout the manuscript – Avoid the use of “etc.”. Specify all your variables here.
L321 – Could you be more specific about this gradient?
L357 – “was also negatively related”. Why “also negatively related”, if in the previous sentence you referred it was positively related?
L357 – “was also negatively related to eutrophication status”. Not clear this sentence as the eutrophication status seems to be the response variable, with predictors being elevation (+) and area (+).
L363-368 – The coefficients in both equations (oligotrophic and eutrophic) are almost the same (including the SD), except for the constant. Is that ok?
L375-378 – For better clarification, I think it would be useful to refer the types of the 148 reservoirs. Are all for hydropower purposes? Some irrigation? Multiple uses?
L392 – Would you like to comment on the other 50% unexplained variation? Any potential factors/variables not accounted for the present study and worth of studying in the future?
L447 – “between 0 to 1500 ha,”. Zero??
Fig. A1- provide a scale on the map and the north indication.
Captions to Tables A3 and A4 – This is too vague. Give complete captions, outlining the name of your study area, goal, etc.
