Harmful Algal Blooms: A Prolific Issue in Urban Stormwater Ponds
Round 1
Reviewer 1 Report
Brief summary:
Thank you for allowing me to review the manuscript “Harmful algae blooms: A prolific issue in urban stormwater ponds ” authored by Grogan et al. In this paper, the authors focused on sampling and identification of 87 algal blooms in the greater Wilmington, North Carolina area from 2019 to 2022. The study is current and novel in assessing the potential hazard of such blooms in monitoring and restoration of stormwater ponds. Since these stormwater ponds play an important role in the storage of rainwater and other runoffs, their damage by algal blooms affects their natural nutrient recycling process. The authors reported that several cyanobacterial groups producing harmful toxins were present in the stormwater samples indicating the development of potential management strategies that could minimize the frequency of algal bloom occurrence, especially from those which produce harmful toxins. Overall, this study is well-designed and sufficiently carried out according to standard protocols. Apart from that, I would like to suggest some essential improvements in the manuscript as given below:
Please add continuous line numbering to facilitate easy reviewing.
Title:
Please indicate the study location, state, and country in the title.
Abstract:
Although the authors wrote an abstract while covering most of the critical information about this study, the arrangement of sentences is not precise, which makes its reading redundant. I suggest that the authors reduce the length of the abstract to not more than 250 words and rearrange the contents in the following order: the problem of algal blooms in stormwater, research objectives, research method, major numerical findings, the major outcome of the study, and overall contribution of these findings to current knowledge.
Keywords:
The keyword section is missing in the manuscript, please provide it accordingly.
Introduction:
The introduction is well formulated however, it would be better if the authors provide some stats on algal bloom issues at the global and national levels with relevant citations.
Methods:
It is not clear how many samples were collected from each stormwater pond. Also, were the samples pooled before analysis or they were pooled post-analysis to obtain a single mean value?
Physicochemical conditions: please replace it with Physicochemical parameters.
Mostly, the unit of chlorophyll content is taken concerning algal biomass and not water. Please check it carefully.
Figure 2: The location of the 39 sampled locations should be supported by geocoordinate axes. Also, what is meant by different color points (green, sky blue red, etc.)? This map should be reduced in size and place a map of individual North Carolina within the USA on the left. Then use an arrow to focus on the location there. Please provide the source of the map too within its caption.
Please cite the methods of microcystin estimation as per test kits (reference).
The information on instruments used is missing (instrument name, model, company, city, country, etc.).
Results and discussion:
Table 1: Please write the full names of toxins under the table footer. Also, replaced sp. in the middle column with the exact Genera name followed by sp.
The PCA results are not satisfactory. E.g., the variance covered by each PC (PC1 and PC2) hardly has cumulative coverage of 55% which is very low. Did the author try rotation? What are the possibilities of significance in PC3 and PC4? If they have higher eigenvalues and variances, I suggest including them in the results (or as supplement files).
Please check the results of MCA too.
Conclusion:
Fine.
References:
Citations in the text and reference list don’t follow the MDPI style guidelines. Please correct them accordingly.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been significantly improved. I suggest accept in current form.
Author Response
We thank the reviewer for their suggestions and appreciate their review.
Reviewer 2 Report
As reported by the authors, microcystin was detected in 5 blooms. Please indicate that in Table S1.
Author Response
We thank the reviewer for their comments and advise that the location of microcystin positive blooms is in Table S1. An additional in-text reference was made to Table S1 where microcystin detections are mentioned.
"Though the presence of MC detected in blooms was not remarkable, the five blooms found to be positive for MC occurred across five unique locations (Table S1), demonstrating toxin production is not isolated to specific waterbodies."
