Review Reports - From Land to Water: The Impact of Landscape on Water Quality Through Linear Models

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Why in Portugal sampling was done only during the spring/summer (dry season) season, while in Galicia it was done all year round (four seasons)? This difference may limit the comparability of the data.

Why 33 stations were used in Portugal and only 7 in Galicia?

The biological or ecological relevance of the models chosen in the modeling process has not been adequately discussed.

Author Response

Reviewer 1

Comments and Suggestions for Authors:

Response: We thank the reviewer for this observation. The difference in sampling periods between Portugal and Galicia reflects the monitoring protocols applied in each region. In Portugal, macroinvertebrate sampling was conducted during the spring/summer (dry season) following the Water Framework Directive (WFD) regulations, which standardize the timing of ecological assessments. In Galicia, the data originate from regional monitoring programs, which collect samples throughout all four seasons. These monitoring campaigns were not originally designed for direct comparison with Portuguese data, but they can still be effectively utilized to apply the IBMWP index and assess water quality. Despite differences in temporal coverage, our analyses focus on ecological patterns and diversity metrics that are robust to seasonal variation, allowing meaningful comparisons between regions. We have also clarified this point in the manuscript, in Section 2.1, to improve clarity. (Lines 184-188)

Why 33 stations were used in Portugal and only 7 in Galicia?

Response: We appreciate the reviewer’s question. The difference in the number of sampling stations between Portugal (33 sites) and Galicia (7 sites) reflects data availability and the scope of regional monitoring programs. In Portugal, a larger dataset was accessible through national and regional Water Framework Directive (WFD) monitoring networks, allowing broader spatial coverage of river typologies within the Entre Douro e Minho region. In contrast, in Galicia, only a limited number of sites met the criteria for data comparability, namely the availability of IBMWP results and corresponding landscape metrics for the same sampling years (2010 and 2016). Despite this difference in sample size, the selected Galician sites were chosen to represent the main land-use and ecological gradients in the region, ensuring a robust and meaningful comparison between the two areas. This clarification has been added to Section 2.1 of the manuscript. (Lines 178-182)

The biological or ecological relevance of the models chosen in the modelling process has not been adequately discussed.

Response: We appreciate this important observation. We agree that emphasizing the ecological interpretation of the models strengthens the manuscript. Accordingly, we have expanded the Discussion to better explain the biological and ecological relevance of the selected predictors. Specifically, we now discuss how landscape metrics such as forest cover, patch connectivity, and edge density relate to macroinvertebrate community structure and water quality regulation. Forested and heterogeneous landscapes are known to reduce sediment and nutrient runoff, stabilize hydrological regimes, and provide shading and organic matter inputs that support diverse aquatic biota. Conversely, agricultural and urban expansion increase habitat fragmentation and pollutant loads, favouring tolerant taxa. These mechanisms explain the strong relationships observed between land-use metrics and the IBMWP index in our models.
New paragraphs addressing these aspects has been added to the Discussion section. (Lines 478-489 and 502-510)

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript entitled “From Land to Water: Unravelling the Impact of Landscape on Water Quality Through Linear Models” is interesting research.

Comment 1: The title of the manuscript is clear but could be slightly refined for conciseness (removing “Unravelling”).

Comment 2: The abstract is instructive but would benefit from including key findings of the results to highlight the strength of landscape–water quality relationships.

Comment 3: Clarify whether multicollinearity among independent variables was tested before running linear models.

Comment 4: Line no. 162, Figure 1. Geographic location and digital elevation model is not clear. If possible, make table of selected sites with Geo-coordinate and elevation.

Comment 5: Figures 6 and 8 should be more self-explanatory with expanded captions.

Comment 6: The discussion is generally strong, but linking the findings more clearly with practical management implications would improve its applicability.

Comment 7: Revise long sentences for clarity and readability.

Comment 8: The conclusion could be slightly more concise, with stronger emphasis on practical implications of the study findings.

Author Response

Reviewer 2

Comments and Suggestions for Authors

The manuscript entitled “From Land to Water: Unravelling the Impact of Landscape on Water Quality Through Linear Models” is interesting research.

Comment 1: The title of the manuscript is clear but could be slightly refined for conciseness (removing “Unravelling”).

Response: The correction was done.

Comment 2: The abstract is instructive but would benefit from including key findings of the results to highlight the strength of landscape–water quality relationships.

Response: Thank you for your comment. We have revised the abstract to better highlight the key findings of the study and emphasize the strength of the relationship between landscape metrics and water quality, as requested. In the updated abstract, we explicitly state that landscape metrics, particularly in agricultural and forested areas, significantly influence water quality, and that land use composition and configuration drive differences in ecological conditions between regions. Additionally, the abstract now clearly links these findings to the predictive performance of the models, reinforcing the relevance of landscape structure in regulating river ecosystem health. (lines 34-35 and 40-41)

Comment 3: Clarify whether multicollinearity among independent variables was tested before running linear models.

Response: Thank you for your comment. We have clarified in the Methods section that multicollinearity among independent variables was thoroughly assessed before fitting the linear regression models. Specifically, Variance Inflation Factor (VIF) values were calculated for all potential regressors, and only variables with VIF < 5 were included in the models. This ensures minimal multicollinearity and reliable estimation of the individual effects of landscape metrics on the IBMWP index. (lines 262-263)

Comment 4: Line no. 162, Figure 1. Geographic location and digital elevation model is not clear. If possible, make table of selected sites with Geo-coordinate and elevation.

Response: Thanks for the observation, we have included now included in the supplementary material, S2, the coordinates and elevation of points, used for calibration and validation.

We have also mentioned at the begging of the result section, that the coordinates of the sampling sites are available “In this study, 1,926,343 benthic macroinvertebrate individuals belonging to 106 families were identified across the 40 studied sites (7 GL and 33 PT), coordinates are provided in the Supplementary Material S2.”

Please note that all the used data for the regression models is also available in the supplementary material.

Comment 5: Figures 6 and 8 should be more self-explanatory with expanded captions.

Response: Thank you for your comment. We have expanded the captions of Figures 6 and 8 to make them more self-explanatory. These updated captions provide a clear description of the data presented and the relevance of each figure to the study’s objectives. (lines 458-463 for Fig 6 and lines 531-534for Fig. 8)

Comment 6: The discussion is generally strong, but linking the findings more clearly with practical management implications would improve its applicability.

Response: We thank the reviewer for this valuable suggestion. In the revised manuscript, we have strengthened the link between our results and practical management actions (see please lines: 364-373, 430-437, 486-489 and 564-572). This addition clarifies how the findings can inform restoration, monitoring, and conservation strategies, providing concrete examples relevant to both Galicia and North Portugal.

Comment 7: Revise long sentences for clarity and readability.

Response: We thank the reviewer for this important observation regarding sentence length and readability. In the revised manuscript, we carefully reviewed all long and complex sentences throughout the text. Several sentences were divided into shorter, more focused statements to improve clarity, flow, and readability without altering the scientific content or meaning.

Comment 8: The conclusion could be slightly more concise, with stronger emphasis on practical implications of the study findings.

Response: We thank the reviewer for the suggestion. In response, we have revised the Conclusions section to make it more concise and to emphasize the practical implications of our findings. The revised text highlights how land management practices influence biodiversity and water quality, and explicitly discusses actionable recommendations for integrated and adaptive governance, including maintaining habitat heterogeneity, supporting biodiversity, and implementing targeted restoration measures. These changes improve the clarity and applicability of the study for management and conservation purposes. (lines 582-591).

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript submitted for review addresses a pressing issue: assessing landscape influence on water quality using linear models (using the Galicia-North Portugal Euroregion as an example).

Water quality assessment is a priority for any country, as water is an essential resource for maintaining normal human life. Water resource management is currently a complex and dynamic decision-making process that requires constant adaptation. In the face of climate change, it is essential to develop adaptive management strategies that take into account current and projected changes. A landscape-geoecological approach is currently widely used to address these issues. This tool allows for a comprehensive understanding of the state of the basin as a whole, identifying zones of increased anthropogenic pressure, and determining the dynamics of processes affecting the hydrological, hydrochemical, and hydrobiological parameters of aquatic ecosystems.

The manuscript contains interesting results.

However, there are some comments regarding it. The main one concerns the structure of the manuscript. The authors excluded Section 4. Discussion from the manuscript structure, merging it with Section 3. Results. However, this Section 3 essentially presents only the results and weakly discusses them. In my opinion, it should be broken down into separate components.

Other comments:

Lines 140-141. The names of the main forest-forming species in the studied watershed (Pinus pinaster, etc.) should be provided with the authors' names.
It is necessary to clarify what the authors mean by "40 sites" (line 166). Are these 40 samples or 40 sampling points, each with multiple samples? And then, how many samples were collected in total?
Line 171 states "Benthic macroinvertebrate." Other macroinvertebrates are not described in the paper. In my opinion, the word "Benthic" should be added to the Abstract (line 28) of the paper. The same should be added to the keywords, as well as to lines 165 and 166. From here on, it can be referred to as "macroinvertebrate." Macroinvertebrates are a fairly large group of organisms, so it would be more appropriate to provide a more detailed description of the group of organisms studied in the Materials and Methods.
Since the authors studied benthic macroinvertebrates, whose life is associated with the substrate, some clarification is needed regarding the predominant types of sediments in the water bodies, as well as the types of organic and inorganic substrates as habitats considered (Line 179).
To what unit of measurement is the abundance of organisms expressed? (Lines 278, 282, etc.).
The results of the statistical analysis of the boxplots should reflect the results of pairwise comparisons. It would be helpful to show the differences between years in Figure 4 using compact letter notations.
Some figures in the manuscript are of poor quality. For example, Figure 8 is difficult to read. Also, the caption for this figure in the manuscript is located above the figure itself.

Author Response

Reviewer 3

Comments and Suggestions for Authors:

The manuscript submitted for review addresses a pressing issue: assessing landscape influence on water quality using linear models (using the Galicia-North Portugal Euroregion as an example).

The manuscript contains interesting results.

Response: We thank the reviewer for this observation. As part of the revisions suggested by Reviewer 2, we have already strengthened the discussion within Section 3, explicitly linking the results to practical management and conservation implications. The added text in Section 3.5 ensures that the ecological and management significance of our findings is clearly presented. (see please lines: 364-373, 430-437, 486-489 and 564-572).

We chose not to split the section into separate “Results” and “Discussion” sections to maintain a cohesive narrative that integrates ecological patterns, statistical modelling, and landscape implications. This integrated structure allows the reader to immediately connect observed patterns in macroinvertebrate diversity and landscape metrics with the corresponding management recommendations, without interrupting the logical flow of the manuscript. The added discussion text ensures that the section meets the reviewer’s expectations for interpretative depth while preserving clarity and readability.

Other comments:

Lines 140-141. The names of the main forest-forming species in the studied watershed (Pinus pinaster, etc.) should be provided with the authors' names.

Response: The correction was done. (lines 141-142)

Line 171 states "Benthic macroinvertebrate." Other macroinvertebrates are not described in the paper. In my opinion, the word "Benthic" should be added to the Abstract (line 28) of the paper.

Response: The correction was done. (line 28)

The same should be added to the keywords, as well as to lines 165 and 166. From here on, it can be referred to as "macroinvertebrate."

Response: The corrections were done. (line 44 and 168-171)

Macroinvertebrates are a fairly large group of organisms, so it would be more appropriate to provide a more detailed description of the group of organisms studied in the Materials and Methods.

Response: We appreciate the reviewer’s valuable comments. A new introductory paragraph has been added at the beginning of Section 2.2.1 (Water Quality Assessment Using Benthic Macroinvertebrate Assemblages) to provide a more detailed description of the benthic macroinvertebrate community and its ecological relevance. (lines 168-176)

Since the authors studied benthic macroinvertebrates, whose life is associated with the substrate, some clarification is needed regarding the predominant types of sediments in the water bodies, as well as the types of organic and inorganic substrates as habitats considered (Line 179).

Response: The corrections were done. (line 198-199)

To what unit of measurement is the abundance of organisms expressed? (Lines 278, 282, etc.).

Response: We appreciate the reviewer’s observation. We agree that, given the differences in the sampled areas between Portugal (1.25 m²) and Galicia (2.5 m²), the most appropriate way to express abundance is by standardizing the data to individuals per square meter (ind/m²). This adjustment allows for a more accurate comparison of macroinvertebrate densities between sites and regions, minimizing the influence of sampling effort. Accordingly, the text has been revised to present relative abundance values expressed as ind/m². (lines 301-303)

The results of the statistical analysis of the boxplots should reflect the results of pairwise comparisons. It would be helpful to show the differences between years in Figure 4 using compact letter notations.

Response: Thank you for your comment. The results indicate no significant differences either between regions (Portugal vs. Galicia; p = 0.7324 and p = 0.8066, both > 0.05) (Fig. 3) or between years (p = 0.27 and p = 0.21, both > 0.05) (Fig. 4). Therefore, there is no need to add different letters on the boxplots. When the global test (Kruskal-Wallis or ANOVA) is not significant, no pairwise (post-hoc) comparisons are performed, and all samples are considered to belong to the same statistical group. Nevertheless, we have added a small sentence in the figure legends of Figures 3 and 4 indicating that no significant differences were detected between regions and years, respectively: “No significant differences were detected among regions (Kruskal-Wallis, p = 0.73; ANOVA, p = 0.81)” for Figure 3, and a similar note for Figure 4. (lines 379 and 384)

Some figures in the manuscript are of poor quality. For example, Figure 8 is difficult to read. Also, the caption for this figure in the manuscript is located above the figure itself.

Response: According to this pertinent observation, authors have improved the quality of Figures, >=300 dpi. Specifically for Figure 8, the text size was increase. However, for the supplementary material figures (each model scatter plot) the text size was not changed, as these are not portrayed in panes but individually. Still, for the figures that are presented in the manuscript, are shown in lower quality to decrease the size of the document but were uploaded in high quality in the journal platform.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have made corrections and clarifications to most of my comments. I believe the manuscript can be accepted for publication.