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I am satisfied with the modifications that have been made to the manuscript and recommend that it be accepted for publication. Congratulations.
[# PeerJ Staff Note - this decision was reviewed and approved by Ann Hedrick, a PeerJ Section Editor covering this Section #]
I have received comments back from one experte reviewer who has evaluated your resubmission. While some of the comments have been incorporated into the new version, there are some that were not. Please ensure that all comments are incorporated into the text.
The authors have revised the ambiguous text and have proofread the manuscript for clarity. Appropriate literature references have been added and removal of inappropriate citations. Figure captions have been edited for clarity.
Headings of the endpoints measured were modified for clarity, and reviewer queries were answered and incorporated appropriately.
A more comprehensive commentary of the data was undertaken and added to the manuscript. Please add a statement in the Conclusion reiterating the contribution of the study to the limited knowledge of the potential effects of PHMG to the aquatic ecosystem.
The authors did a thorough job of responding to reviewer comments; however, some of the responses were not incorporated that would benefit the manuscript. For example, please include the following authors' response within the Introduction:
While direct monitoring data of PHMG in natural water bodies remain limited, existing studies suggest its potential accumulation in aquatic systems through sludge disposal pathways. Guanidine derivatives (structural analogues of PHMG) have been detected in municipal wastewater treatment effluents, highlighting the persistence of such disinfectants in the aquatic environment (Sci. Total Environ. 2022, 839, 156329; Sci. Total Environ. 2022, 816, 151665). These studies support the hypothesis that PHMG could enter and persist in aquatic systems, particularly in areas with intensive industrial or medical use of disinfectants.
The following response should be included within the text of the Methods:
The concentrations of PHMG chosen for the experiments (0.03-3 mmol/L) are much higher than the typical concentrations found in current natural waters, but are nevertheless relevant. The low concentration group (0.03 mmol/L) is close to the potential contamination level in the real environment, while the high concentration group (3 mmol/L) is used to assess the ecological risk under extreme conditions(Sci. Total Environ. 2022, 839, 156329; Sci. Total Environ. 2022, 816, 151665).
This response should be included within the text of the Discussion:
PHMG (polyhexamethylene guanidine) is a cationic polymer that exerts its biocidal effects primarily by disrupting microbial cell membranes. In this study, we observed that PHMG exposure caused significant damage to the photosynthetic apparatus of microalgae, particularly impairing Photosystem II efficiency and reducing chlorophyll content. Additionally, PHMG induced oxidative stress in microalgae, as evidenced by increased levels of antioxidant enzymes (e.g., CAT, SOD) and malondialdehyde (MDA). These findings suggest that PHMG's mode of action involves both direct membrane disruption and secondary oxidative stress.
We have received evaluations from two expert reviewers and their comments can be seen below. Please ensure that you attend to all of the reviewers´ comments in a rebuttal where you clearly show the changes that have been made in the manuscript. Also, please ensure that the many typographical and grammatical errors throughout the manuscript which must be corrected before resubmission. In your rebuttal letter, please clearly indicate where the changes have been made in the manuscript.
**Language Note:** The review process has identified that the English language must be improved. PeerJ can provide language editing services - please contact us at [email protected] for pricing (be sure to provide your manuscript number and title). Alternatively, you should make your own arrangements to improve the language quality and provide details in your response letter. – PeerJ Staff
There are numerous grammatical and typographical errors throughout the manuscript.
Some references that can be added:
Genty et al 1989, Schreiber et al 1986, Annenkov et al. 2020, Postulkova and Kopp 2016
Please include units in raw data file.
Objective of the study is clear and relevant; however, the design of the experiment is unclear.
Methods need cleaning up and need to be more detailed.
Need more comparisons with other studies. Assumptions were made without sufficient substantive evidence.
Please see attached file for a more comprehensive review of the manuscript.
The article is written in clear English throughout. The Introduction is precise.
Line 67-68 mentioned PHMG as external stressor should be supported with supportive references.
Hypothesis is not new in this article but employing SEM tool is useful.
Hypothesis can be justified more to carry out the work.
The design of experiment is properly planned and executed.
Research question is relevant, and parameters are well studied to study the identified gap.
Results section the subheadings should be modified for instance, mechanism of photosynthesis in microalgae (181) where actually no mechanism is explained.
Findings are well written and statistically verified. SEM is explained well
Conclusions are stated clearly in the article.
no comments
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