How does Urban Pollution Influence Macroinvertebrate Traits in Forested Riverine Systems?
Round 1
Reviewer 1 Report
I appreciate the effort the authors have made in addressing my earlier concerns with the manuscript and I believe the paper is greatly improved. I will include only a few remaining comments on the current resubmission.
Table 2 is an improvement. You might discuss with the editor putting hte entire table in Supplemental Materials and only showing the significant interactions (+/-) to keep the overall manuscript shorter.
I disagree that actually reporting p-values makes a paper overly lengthy and believe it strengthens the understanding for the reader.
Please add units to the water quality parameters in the Supplemental Materials.
Figure 4 y-axis still says log transformed.
The discussion is much improved. I would be careful in the beginning section of putting too much emphasis on using traits in regions where the taxonomy is not well describe since it is the taxonomy that you use to assign traits (LN 379).
I strongly believe it is important to provide more information on the watersheds (such as size, landuse, etc). This information is what allows other researchers to compare their work to yours and for us as a community to begin to ask mechanistic questions about the role of urbanization across landscapes and biomes. Also, lack of this information is what is generally leading to my confusion. You describe these watersheds as forested urban rivers. What does that mean in your region? Does this describe a 1 m riparian buffer? A watershed with forested headwaters but the remainder of the watershed is urban? Or maybe include a couple of phots of the sites?
Finally, while the other paper focuses on agricultural watersheds with an overlap on the urban watersheds in this paper I disagree that there is nothing to be learned by comparing you sites. Forested, agriculture, and urban is part of a larger gradient of land use change - especially if your agricultural streams have potential to become urban due growth of cities.
Author Response
Comment 1: Table 2 is an improvement. You might discuss with the editor putting hte entire table in Supplemental Materials and only showing the significant interactions (+/-) to keep the overall manuscript shorter.
Response: Sure, we will discuss with the editor with regards to showing only the significant interactions and also possibly relocating the Table to supplementary materials section.
Comment 2: I disagree that actually reporting p-values makes a paper overly lengthy and believe it strengthens the understanding for the reader.
Response: At the moment we cannot lay my hands on the p-values of the test for significance performed. Should it be very necessary in the paper, we will consider reanalyzing the data all over, probably at the proof reading stage.
Comment 3: Figure 4 y-axis still says log transformed.
Response: We actually transformed that abundance data logarithmically to avoid skewness. Again, we will consider reanalyzing without transformation, if it became necessary at the proof stage.
Comment 4: The discussion is much improved. I would be careful in the beginning section of putting too much emphasis on using traits in regions where the taxonomy is not well describe since it is the taxonomy that you use to assign traits (LN 379).
Response: The discussion section has been improved with regards to beginning the section with taxa discussion. More discussion on taxa have been dwelled upon in the first paragraph in the Discussion section (please see lines 380-389) of the revised version of the manuscript.
Comment 5: I strongly believe it is important to provide more information on the watersheds (such as size, landuse, etc). This information is what allows other researchers to compare their work to yours and for us as a community to begin to ask mechanistic questions about the role of urbanization across landscapes and biomes. Also, lack of this information is what is generally leading to my confusion. You describe these watersheds as forested urban rivers. What does that mean in your region? Does this describe a 1 m riparian buffer? A watershed with forested headwaters but the remainder of the watershed is urban? Or maybe include a couple of phots of the sites?
Response: Information on the land use types dominance and catchment sizes of the sampled sites have been presented in Table 1 in the Supplementary materials section. Also, a brief explanation on how the dominant land use types were determined can be seen in lines 110 -115 of the Materials and Methods section.
Comment 6: Finally, while the other paper focuses on agricultural watersheds with an overlap on the urban watersheds in this paper I disagree that there is nothing to be learned by comparing you sites. Forested, agriculture, and urban is part of a larger gradient of land use change - especially if your agricultural streams have potential to become urban due growth of cities.
Response: A comparative explanation of the present study findings with regards to sites land use types with our earlier study on urban and agricultural catchments can be found in lines 491 – 500 in the revised manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
I think the authors have made some revisions to improve the manuscript before it was re-submitted. There remain some minor issues although are not too many. These will be probably corrected in preparation of proofs.
Line 53-54: Authors already abbreviate CPOM and FPOM at line 49-50. Please use abbreviated words after abbreviation.
Line 105: Where is the GPS information?
Author Response
Comment 1: Line 53-54: Authors already abbreviate CPOM and FPOM at line 49-50. Please use abbreviated words after abbreviation.
Response: Abbreviated words are now been used in Lines 53 -54 (please see track changes on Lines 53 -54) of the revised manuscript.
Comment 1: Line 105: Where is the GPS information?
Response: The geographical locations of the twenty sampled sites have been presented on Supplementary Table 1. Also see lines 106 -107 of the revised manuscript as reference.
Author Response File: Author Response.docx
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
The paper by Edegbene et al. investigates the distribution of macroinvertebrate species and traits across multiple watersheds in the Niger Delta area of Nigeria. The authors relate these patterns to changes in water quality to determine how pollution impacts macroinvertebrate traits compared to forested rivers. Overall, this paper contributes to our knowledge of stream macroinvertebrates and river health by focusing on an ecosystem that is not well described and where there are few data on either species or traits. Also, the trait-based approach adds information to our overall knowledge of the impact of changing water quality on ecosystem processes.
While there are many strong aspects to this paper and it is interesting, there are several weaknesses that should be addressed. I have summarized ways the authors can improve the paper below.
- Generally the paper could use editing for both spelling and grammar. I have put some issues here by line number.
15: urbanization (and throughout the paper)
18: put a colon after classes and semicolons after each category (LIS, MIS)
19: write out what KLQ stand for
23: sentence is too long, consider breaking into 2 or more sentences
36: what does developmental quest mean?
39: what does complexity of ecological niches mean? rephrase
48: litter
52: just use CPOM
53: efficient instead of easy; nutrients instead of nutrient cycling
54: delete aquatic food chain
56: the majority
57: are shaded (not covered by shades from leaves)
58: need a reference for this fact (if possible)
60: floodwaters instead of flood
64: sources
65: sources
66: using a instead of by exploring
75: need a reference for the urban stream syndrome (Walsh is fine)
79: genera (not genus)
83: remain scarce instead of scanty
94: change heading to Study Sites
149: small "s" in sites
151: delete a multivariate model
246: plots
318 and 356: predation
329: a distribution is a pattern and not a process; reword
343: resilient
- General paper comments
Ln 48: In this system what is the difference between litter and coarse particulate organic matter? Generally, litter is part of the CPOM category.
Ln 86: How are points (I), (ii), and (iii) different? I think these need to be rephrased. Point (i) seems more like the overall goal and not a specific objective.
Ln 127: Can you describe the timing of sampling more clearly? By seasonal I assume you mean the wet/dry season? And then you sampled monthly in each one? Were all sites collected equally? How many samples were collected in each season and over the course of the study?
Ln 142: How many replicates were collected for the water quality analyses for N, P, and BOD?
Figure 2a would be improved if you could color code the site names by LIS, MIS, HIS. Eventually Figure 2 would have to be cleaner - meaning a higher quality figure as it is quite blurry in its present form.
I would consider redoing Figure 3 to make it easier for a reader to interpret. Could you only include the traits that were significant so that you have fewer rows? Or even make this a table with the significant traits (as names) written out in the first column and a "+" or "-" in the column under the WQ variables? In its current form it is too hard to interpret.
Figure 4 and KW-results - I would like to see the actual p-values here (instead of p<0.05). How significantly different are these means? Based on the plots they seem very close and so I have to question if they are close to p~0.05 are they truly biologically significant in this system? If you use transformed data (see major comments below) please plot the untransformed data on the graph so the reader can see the "true" values for relative abundance instead of transformed values which have less meaning. And if they are significant it is not indicated on the figure.
- Major paper comments
The site description would be significantly improved if there were more details given about the watersheds such as watershed size, geology, general description of the geomorphology of the reaches (are they riffle-runs? glides?), slope of the reaches (are these mountainous, lowlands, steep headwaters, floodplain systems). If available, it would also improve the paper if you could describe the land use in each watershed you sampled - how much was forest, urban, and agriculture and how did these vary among the sites?
I am confused on how you collected the samples. You say you only collected for 3 minutes at each site? How is it possible to get a representative sample at a site in only 3 minutes? Did you mean 3 minutes per biotope?
I understood the initial PCA analysis (LN 161) but it would strengthen the paper to show these data so as a reader I can evaluate the results since it is the basis of your overall classifications. Perhaps the PCA plot could be put in a supplemental material? Also, it would be useful to show the water quality data across sites - this could also be put in a table in the supplemental materials. And I think it would be a better paper to show the PCA plot and put Table 1 in the supplemental materials. The inter-site distances are not meaningful to the reader in this format.
Why did you log transform the data (figure 4) if you are using a KW test? The KW is a non-parametric data that you use on non-normal data so there would be no need to transform the data. Why did you use Tukey's (not turkey) HSD test with the Kruskal-Wallis? KW is a non-parametric test and it is more typical to use the Wilcoxon test to look at differences between means. It makes more sense to transform the data, check for normality and use ANOVA/Tukey or don't transform the data and use KW/Wilcoxon.
The Discussion section need to be significantly expanded and compared to other literature to demonstrate the importance of these results to freshwater ecology. Some suggestions for improving this section include:
- expand on the kinds of taxa (by name) that are sensitive to urban pollution in this system (LN332);
- you say that grazing (LN347) is significantly lower in MIS and HIS compared to LIS however in the results section they are not significantly different (p>0.05) and your boxplots don't look different so this conclusion needs to be clarified;
- you compare predators in your rivers with those of the St. Laurence River (ref [5]) - are these the same taxa being compared; you could be more specific here on the types of taxa and what their prey items; it is not clear if your predators are also dominated by Coleoptera and Hemiptera as in ref [5]
- you do not integrate at all the results that are significant into the Discussion such as the hard-shell trait; what are these organisms and why would they be sensitive to pollution?
- why are the other traits you examined tolerant to pollution?
I recommend coming back to your objectives and organizing your discussion around them. If I only read the discussion I would not walk away with a clear understanding the purpose of your paper and your significant conclusions.
The discussion would also be improved by having some general summaries of the system - I have no idea what kinds of macroinvertebrates live in these systems, I have no idea on the range of water quality values across the watershed. These types of data could be summarized near the top of the discussion with a re-emphasis on the study objectives. You emphasize the lack of knowledge for this region but I don't feel I know any more about its ecology after reading your paper - you could really emphasize multiple comparisons here with the rich literature from Europe and North America on macroinvertebrate species and traits and water quality.
My major concern with this paper is citation [13]. This other paper in Aquatic Ecology seems very similar to this paper which brings up multiple questions. First, why were these 2 studies separated into 2 different papers? Is there some difference in the sites that is important? Some of the sites in the 2 papers seem to overlap - so why are they in both papers? Is there a scientific reason for separating the sites? Also, if there is a good reason to have the sites separated into 2 papers, why do you not cite this paper in the conclusions? It seems the other paper found more traits that varied with pollution than your paper, why? Is it due to the sites? Again why? While I do not have a problem with using the same experimental design and analytical approach for the 2 papers, the lack of information about why these sites are different from the other paper is extremely worrisome.
Reviewer 2 Report
Overall comment
The manuscript entitled “How would urban pollution influence macroinvertebrate traits in forested riverine systems in the Niger Delta area of Nigeria?” which you submitted to Water, has been reviewed. I am not an expert on macroinvertebrate study field, but as a reader, I have found this manuscript interesting. While I am generally positive about the manuscript, I think there are some major points that should be issued (or at least clarified) by the authors; as well as some minor comments which I hope will help improving the manuscript.
Major comments
- Studies of functional feeding group traits are now emerging issue in the ecological research field. But also, this paper pointed out macroinvertebrate FFG trait in the forested riverine system. However, You should state objective and hypothesis of the study more clearly and repetition statement about importance of forested riverine systems should be fastened and shortened but also have to provide specific definition of forested riverine systems
- The statistical analysis looks not well explained and poor and this might affect the conclusions. It is important to avoid that in order to enforce the credibility of a paper that has important data that might show importance of forested riverine habitat for macroinvertebrate. Therefore, you should explain it much more clearly and provide more detailed information (i.e. which kind of data did you use, transformed data or not?).
- Readers of the article would be interested in what management actions will occur as a result of this study. Will there be planting of vegetation in the forested riverine system, improvements in water quality or any other activities?
Minor comments
- Line 20-21: which were positively significantly associated with => which were significantly positive association with
- Line: BOD5 => please provide a full information
- Line 29-30: keywords should be revised. It doesn’t match with abstract.
- Line 36: occasioned => are occasioned
- Line 52: coarse particulate organic materials (CPOM) => CPOM
- Line 53: fine organic materials (FPOM) => FPOM
- Line 54: the functional groupings è the functional feeding groups (FFG)
- Line 70-71: the macroinvertebrate functional feeding groups => the macroinvertebrate of FFG
- Line 98-99: how big size of space is covered by canopy of forest?
- Line 109-111: I suggest you providing a GPS information of sampling sites.
- Line 133: Could you provide detailed information such as company name, location and so on.
- Line 135-137: Could you provide unit information of physico-chemical variables.
- Figure 2: Please provide scale bar and publishable quality figure file.
- Figure 4: I suggest you to add alphabets or number on each panel. It would be more readable for the readers
- Line 329-330: need relevant references
- Line 331: which species has large body size? Could you provide information for species name?
Please see the related references.
Hulot, F. D., Lacroix, G., Lescher-Moutoué, F., & Loreau, M. (2000). Functional diversity governs ecosystem response to nutrient enrichment. Nature, 405(6784), 340-344.
Ishikawa, N. F., Chikaraishi, Y., Ohkouchi, N., Murakami, A. R., Tayasu, I., Togashi, H., ... & Okuda, N. (2017). Integrated trophic position decreases in more diverse communities of stream food webs. Scientific reports, 7(1), 1-8.
Oh, H. J., Jeong, H. G., Nam, G. S., Oda, Y., Dai, W., Lee, E. H., ... & Chang, K. H. (2017). Comparison of taxon-based and trophi-based response patterns of rotifer community to water quality: applicability of the rotifer functional group as an indicator of water quality. Animal cells and systems, 21(2), 133-140.
Reviewer 3 Report
The manuscript must be improved because both physico-chemical and biological data, on which statistical analyses are based, are completely lacking. In the test must be reported detailed tables on collected data, macroinvertebrate list and relative abundance in the sites. The taxa founded as indicative of water quality, especially pollution, must be clearly treated crossing biological, chemical and statistical data. The evidence of relation between taxon-water quality must be showed clearly.
The english language must be improved
