Polluted Rivers—A Case Study in Porto, Portugal

Round 1

Reviewer 1 Report

The paper focuses on regional river pollution and does not highlight insights for global river pollution prevention and control. This magazine is an international academic journal, and the author should add literature to indicate what references are available for global river pollution prevention and control.

1.      L104-106，This sentence seems to have no relevance to the author's research objectives.

2.      L107-116，In which aspect the authors are said to be this study is highly significant and it’s very important to specify why this study become perspective in my opinion authors more specific about their objectives.

3.      L88-90，This sentence should be deleted.

4.      The introduction section of the paper lacks logical coherence and should be rewritten

5.      L119-120，The samples were collected (at least two samples in duplicate) around 8:00 and 10:00. Please explain why.

6.      Please add the significance or inspiration of this study for similar river pollution in other regions

7.      L394-395，This sentence should be described in the overview of the sampling point or research area.

Minor editing of English language required

Author Response

Manuscript:

ecologies-2907212

(P. Lemos, P. Silva, C.A. Sousa, A.J. Duarte)

The authors made a careful revision of the manuscript taking into account the suggestions and comments proposed. All the required modifications were taken into account. We consider that the comments were very useful to improve the quality of the work.

We made the revision using the following approach:

• Reformulation of the manuscript when needed (with the highlighted in blue).
• Our answers to the comments and recommendations proposed by the Reviewers.

Reviewer #1

The paper focuses on regional river pollution and does not highlight insights for global river pollution prevention and control. This magazine is an international academic journal, and the author should add literature to indicate what references are available for global river pollution prevention and control.

- We acknowledge the Reviewer for the comments. In fact, this manuscript focuses on a regional river pollution; however, the main goal of this work is to highlight the importance of the maintenance and monitoring of a river pollution within highly populated urban areas, which is the case of Tinto River. Moreover, several articles had provided similar studies in specific rivers in specific countries and not as a global analysis (Borja-Serrano et al, 2020; Carvalho et al, 2004; Nhantumbo et al, 2023; Sandoval et al, 2009; Pharaoh et al, 2023). Therefore, in order to compare with our results, different articles describing rivers pollution and/or prevention in different countries were cited in this manuscript (L.242-253; 300-306).

Borja-Serrano, P., Ochoa-Herrera, V., Maurice, L., Morales, G., Quilumbaqui, C., Tejera, E., & Machado, A. (2020). Determination of the microbial and chemical loads in rivers from the Quito capital province of Ecuador (Pichincha) - a preliminary analysis of microbial and chemical quality of the main rivers. International Journal of Environmental Research and Public Health, 17, 5048. https://doi.org/10.3390/ijerph17145048

Carvalho, C. D. F., & Stapelfeldt, F. (2004). Qualidade das águas do ribeirão Ubá-MG. Revista Escola de Minas, 57, 165-172. https://doi.org/10.1590/S0370-44672004000300005

Nhantumbo, C., Cangi Vaz, N., Rodrigues, M., Manuel, C., Rapulua, S., Langa, J., Nhantumbo, H., Joaquim, D., Dosse, M., Sumbana, J., Santos, R., Monteiro, S., & Juízo, D. (2023). Assessment of Microbial Contamination in the Infulene River Basin, Mozambique. Water, 15, 219. https://doi.org/10.3390/w15020219

Pharaoh, E., Diamond, M., Ormerod, S. J., Rutt, G., & Vaughan, I. P. (2023). Evidence of biological recovery from gross pollution in English and Welsh rivers over three decades. Science of the Total Environment, 878, 163107. https://doi.org/10.1016/j.scitotenv.2023.163107

Sandoval Villasana, A. M., Pulido-Flores, G., Monks, S., Gordillo Martinez, A. J., & Villegas Villareal, E. C. (2009). Physicochemical, microbiological and toxicological evaluation of the environmental degradation of the Atoyac river, Mexico. Interciencia, 37, 880–887.

1. L104-106，This sentence seems to have no relevance to the author's research objectives.

- We acknowledge the Reviewer for the comment. The sentence was removed.

2. L107-116，In which aspect the authors are said to be this study is highly significant and it’s very important to specify why this study become perspective in my opinion authors more specific about their objectives.

- We acknowledge the Reviewer for the comment. The Tinto River comes into contact with densely populated areas, industrial processes, and wastewater treatment facilities within the Porto city. As such, studying its contamination profile is essential to demonstrate the influence of those external factors on a river's health (for instance, as a model case for other cities and/or countries). The sentence was reformulated (L.104-109).

3. L88-90，This sentence should be deleted.

- We acknowledge the Reviewer for the comment. The sentence was removed.

4. The introduction section of the paper lacks logical coherence and should be rewritten

- We acknowledge the Reviewer for the comment. The Introduction section was reformulated.

5. L119-120，The samples were collected (at least two samples in duplicate) around 8:00 and 10:00. Please explain why.

- We acknowledge the Reviewer for the comment. The reason is to analyze the samples on the same day they were collected (at least two times in duplicate to be representative of the location). It is recommended for microbial analysis to perform water analysis on the same day (Rice et al, 2017).

Rice, E. W., Baird, R. B., & Eaton, A. D. (2017). Standard Methods for the Examination of Water and Wastewater, 23rd Edition. American Public Health Association, American Water Works Association, Water Environment Federation. https://doi.org/10.2105/SMWW.2882.002

6. Please add the significance or inspiration of this study for similar river pollution in other regions

- We acknowledge the Reviewer for the comment. The significance of this work was improved and described in L.97-109. Moreover, several articles had provided similar studies in specific rivers in specific countries and not as a global analysis (Borja-Serrano et al, 2020; Carvalho et al, 2004; Nhantumbo et al, 2023; Sandoval et al, 2009; Pharaoh et al, 2023). Therefore, in order to compare with our results, different articles describing rivers pollution in different countries were cited in this manuscript, such in Ecuador (Borja-Serrano et al., 2020), Brazil (Carvalho & Stapelfeldt, 2004), Poland (Lenart-Boroń et al., 2017) and Mozambique (Nhantumbo et al., 2023) (L.241-252; 301-305).

Borja-Serrano, P., Ochoa-Herrera, V., Maurice, L., Morales, G., Quilumbaqui, C., Tejera, E., & Machado, A. (2020). Determination of the microbial and chemical loads in rivers from the Quito capital province of Ecuador (Pichincha) - a preliminary analysis of microbial and chemical quality of the main rivers. International Journal of Environmental Research and Public Health, 17, 5048. https://doi.org/10.3390/ijerph17145048

Carvalho, C. D. F., & Stapelfeldt, F. (2004). Qualidade das águas do ribeirão Ubá-MG. Revista Escola de Minas, 57, 165-172. https://doi.org/10.1590/S0370-44672004000300005

Lenart-Boroń, A., Wolanin, A., Jelonkiewicz, E., & Żelazny, M. (2017). The effect of anthropogenic pressure shown by microbiological and chemical water quality indicators on the main rivers of Podhale, southern Poland. Environmental Science and Pollution Research, 24, 12938–12948. https://doi.org/10.1007/s11356-017-8826-7

Nhantumbo, C., Cangi Vaz, N., Rodrigues, M., Manuel, C., Rapulua, S., Langa, J., Nhantumbo, H., Joaquim, D., Dosse, M., Sumbana, J., Santos, R., Monteiro, S., & Juízo, D. (2023). Assessment of Microbial Contamination in the Infulene River Basin, Mozambique. Water, 15, 219. https://doi.org/10.3390/w15020219

Pharaoh, E., Diamond, M., Ormerod, S. J., Rutt, G., & Vaughan, I. P. (2023). Evidence of biological recovery from gross pollution in English and Welsh rivers over three decades. Science of the Total Environment, 878, 163107. https://doi.org/10.1016/j.scitotenv.2023.163107

Sandoval Villasana, A. M., Pulido-Flores, G., Monks, S., Gordillo Martinez, A. J., & Villegas Villareal, E. C. (2009). Physicochemical, microbiological and toxicological evaluation of the environmental degradation of the Atoyac river, Mexico. Interciencia, 37, 880–887.

7. L394-395，This sentence should be described in the overview of the sampling point or research area.

- We acknowledge the Reviewer for the comment. The sentence was added in L.104-106.

Reviewer 2 Report

The paper about Polluted rivers – a stern case study in Porto, Portugal has as a scientific objective  to study the contamination of a Portuguese river (Tinto River), within the Porto city (a highly populated urban area), based on analysis of aerobic microorganisms, coliforms and Enterococcus and total organic matter. The paper is well structured but the authors must take into cosideration the folowing:

1. in the introduction part is necessary to clearly specify the scientifc objectives and the novelty of the analysis made;

2. Also in introdcution part the auhtos can develop the state of the art related to the topic;

3. figure 1 is a capture where authros put the points from whre they made the analysis. Maybe an original igure with the location of the area studied in the city of Porto, and the drainage basin of the Tinto river can enriched the aspect of this figure

4. Sampling point description can be added as an anex at the end of the paper;

5. in the methdo part is necessary to have a flow chart where the authors must point out the stepts used to make the entire analysis.

6. the results and discussion par must be splitted in two diferrent part. The result part must include the description of the entire research made and in the discussion part the authors must compare their results with similar research made in the area studied or who used the same methodology. Also the auhtors must decribe the limitation of the methdology used

some minor editing of English language are required

Author Response

Manuscript:

ecologies-2907212

(P. Lemos, P. Silva, C.A. Sousa, A.J. Duarte)

The authors made a careful revision of the manuscript taking into account the suggestions and comments proposed. All the required modifications were taken into account. We consider that the comments were very useful to improve the quality of the work.

We made the revision using the following approach:

• Reformulation of the manuscript when needed (with the highlighted in blue).
• Our answers to the comments and recommendations proposed by the Reviewers.

Reviewer #2

The paper about Polluted rivers – a stern case study in Porto, Portugal has as a scientific objective to study the contamination of a Portuguese river (Tinto River), within the Porto city (a highly populated urban area), based on analysis of aerobic microorganisms, coliforms and Enterococcus and total organic matter. The paper is well structured but the authors must take into cosideration the folowing:

1. in the introduction part is necessary to clearly specify the scientifc objectives and the novelty of the analysis made;

- We acknowledge the Reviewer for the comment. That introduction part was improved (L.97-109). The objective of this study is to investigate the source of potential microbial contamination from the upstream to the downstream of the Tinto River, a significant river in Porto that comes into contact with densely populated areas, industrial processes, and wastewater treatment facilities. While the analysis methodology itself is not novel (as microorganisms quantification and total organic matter - TOC), as it is described in the Standard Methods (Rice et al, 2017), the novelty lies in monitoring the root cause of contamination across the Tinto River.

Rice, E. W., Baird, R. B., & Eaton, A. D. (2017). Standard Methods for the Examination of Water and Wastewater, 23rd Edition. American Public Health Association, American Water Works Association, Water Environment Federation. https://doi.org/10.2105/SMWW.2882.002

2. Also in introdcution part the auhtos can develop the state of the art related to the topic;

- We acknowledge the Reviewer for the comment. The Introduction section was reformulated.

3. figure 1 is a capture where authros put the points from whre they made the analysis. Maybe an original igure with the location of the area studied in the city of Porto, and the drainage basin of the Tinto river can enriched the aspect of this figure

- We acknowledge the Reviewer for the comment. An original figure with the locations are not feasible since we have 14 locations among 11 km. Moreover, in authors perspective, adding original photos would make reading and perceiving locations on the map difficult (Figure 1). Nevertheless, the drainage basin of the Tinto River was added into Figure 1, as requested.

4. Sampling point description can be added as an anex at the end of the paper;

- We acknowledge the Reviewer for the comment. Appendix A was created and the sampling description points were moved.

5. in the methdo part is necessary to have a flow chart where the authors must point out the stepts used to make the entire analysis.

- We acknowledge the Reviewer for the comment. A flow chart was added in the Appendix (Figure A1).

6. the results and discussion par must be splitted in two diferrent part. The result part must include the description of the entire research made and in the discussion part the authors must compare their results with similar research made in the area studied or who used the same methodology. Also the auhtors must decribe the limitation of the methdology used

- We acknowledge the Reviewer for the comment. The discussion section can be combined with Results (as explained in the Ecologies instructions: https://www.mdpi.com/journal/ecologies/instructions and in the picture above). Also, other articles published in Ecologies used the same approach (for instance: Paiva et al., 2024). Moreover, considering the topics explored and the information contained, it was easier to combined these sections. The limitations of the methodology used are described in L.318-324.

Paiva, P.E.B., Neto, L.M., Marques, N.T., Duarte, B.Z., Duarte, A.M. (2024). Citrus Aphids in Algarve region (Portugal): species, hosts, and biological control. Ecologies, 5, 101-115. https://doi.org/10.3390/ecologies5010007

Round 2

Reviewer 1 Report

Accept in present form

Author Response

We acknowledge the Reviewer for the comment.

Reviewer 2 Report

The discussion part is missing at the end of the result and discussion chapter.

Moderate editing of English language required.

Author Response

Reviewer #2

The discussion part is missing at the end of the result and discussion chapter.

- We acknowledge the Reviewer for the comments. All the required modifications were taken into account. We consider that the comments were very useful to improve the quality of the work. As such, all the manuscript was revised considering the English level (highlighted in blue). Furthermore, more discussion was added to the manuscript at the end of the “Results and Discussion” section (L.317-326, 331-334).