The Yellow Sea Green Tides: Spatiotemporal Dynamics of Long-Distance Transport and Influencing Factors
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsGeneral comments on the review
The Yellow Sea Green Tides: Spatiotemporal Dynamics of
Long-Distance Transport and Influencing Factors
Authors: Fanzhu Qu, Bowen Sun, Ling Meng, * and Tao Zou, *
The article highlights important aspects regarding the in-depth knowledge of the phenomenon of green tides in the Yellow Sea. The results can constitute a starting point for the development of a better management of the impact of these blooms on the ecosystem but also on important human activities, such as tourism and aquaculture.
The literature review is extensive and up-to-date (references up to 2024), which is a strength.
The article must undergo certain changes and additions in order to be published.
Some sentences are too long and have many subordinate clauses; they could be broken up to improve readability. A few figures (e.g. Fig. 2 and Fig. 5) have long legends that can be summarized.
I recommend replacing vague expressions such as some discrepancies, little is known with more precise or quantifiable formulations.
The section on satellite methods is detailed and correctly structured, but could be condensed into a comparative table of the indices used (NDVI, FAI, NDAI, etc.) with their advantages and limitations.
The discussion of the determinants is solid, but the role of interactions between factors (nutrients, currents, mariculture) is only mentioned, not analyzed in detail — a conceptual model would clarify.
I recommend clarifying the methodological differences between the comparative studies and their practical implications.
The conclusions should focus on concrete actions and priority directions.
Please rewrite the review respecting English grammar.
Specific comments and recommendations were made directly on the manuscript.
As a result of the analysis of this review, I recommend publishing after minor revision.
Comments for author File: 
Comments.pdf
Please rewrite the review respecting English grammar.
Author Response
Comments 1: Some sentences are too long and have many subordinate clauses; they could be broken up to improve readability.
Response 1: Thank you very much for taking the time and effort to review our manuscript and providing highly constructive feedback. We have revised the manuscript to simplify the sentence structure throughout.
Comments 2: I recommend replacing vague expressions such as some discrepancies, little is known with more precise or quantifiable formulations.
Response 2: We thank the reviewer for this insightful comment. We have carefully revised the text to replace all imprecise language with quantitative data wherever possible. Please see lines 282-290, Page 3 and line 336, Page 12.
Comments 3: The section on satellite methods is detailed and correctly structured, but could be condensed into a comparative table of the indices used (NDVI, FAI, NDAI, etc.) with their advantages and limitations.
Response 3: We thank the reviewer for raising this point. In our manuscript, we have already discussed the advantages and limitations of the various indices (NDVI, FAI, NDAI, etc.) within the text itself. As suggested, this discussion is structured to provide a comparative analysis, though it is not presently in a table format. Please see our detailed description in Section 2 (lines 78-120).
Comments 4: Introduction
The sentence order is not optimal: the phrase about Unlike other green tides... (lines 39–42) is broken from the narrative flow and relocated in the middle, which breaks the logical connection between the global context and the specific case of the Yellow Sea. It would be more logical to present: Global context (growth of the phenomenon worldwide). Specific case of the Yellow Sea (since 2007). Distinctive character (long-distance drift). Ecological and economic impact. Objective of the article.
Response 4: We thank the reviewer for this insightful suggestion. We agree that restructuring the introduction improves the logical flow and narrative clarity. As recommended, we have reorganized the section. Please see the revised introduction for these changes.
Comments 5: Specific comments and recommendations were made directly on the manuscript.
Response 5: We sincerely appreciate the reviewer’s thorough evaluation and constructive suggestions. In the revised manuscript, we have carefully addressed all specific comments and recommendations point-by-point. Detailed modifications have been made throughout the text, with key revisions highlighted (tracked changes or in color, if applicable) for the reviewer’s convenience.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsOver the past decades, the intensive input of nutrients into aquatic ecosystems has led to the eutrophication of natural habitats. In shallow and coastal ecosystems, eutrophication can be expressed in the mass development of ephemeral macroalgae. In relation to marine ecosystems, this phenomenon is called "green" and "golden" ("brown") tides. The main cause of green tides in the seas is the mass development of algae of the genus Ulva, which can adversely affect the ecological state of the reservoir (change in pH of the environment, a sharp decrease in the concentration of nitrogen and phosphorus in the water, which are necessary for the growth and development of other aquatic vegetation, a decrease in the amount of oxygen dissolved in water, etc.).
The manuscript submitted for review provides a detailed overview of scientific publications devoted to the problem of green tides in the Yellow Sea. The authors provide an overview of methodological approaches to the study of green tides. The causes of spatiotemporal changes in green tides, interannual variability in the size of blooms and possible factors causing these fluctuations are analyzed. The main results of such studies were presented, and the areas where additional scientific research is needed were indicated.
The manuscript claims to be a complete and informative review on this topic. It is written in good, concise language. It may be useful for researchers studying a similar scientific problem.
The manuscript can be recommended for publication with minimal editing. The following recommendations can be offered to improve the manuscript.
- It would be good to provide some information about the biology of Ulva prolifera, the features of the life cycle, growth rates and biomass accumulation in the Introduction. Does this species have biotechnological potential?
- Figs. 1 and 4 - the scale is difficult to read. Figure 1 is placed in the manuscript in section 2 (lines 99-100), although the first mention and reference to it is given in section 3.1 (line 107). In Fig. 4, small font is used for dates. For Fig. 3 It is necessary to unify the font and writing of locations (some coordinates are given, some are not).
- It would be good to consider such an abiotic factor as the content of total phosphorus in sea waters. Phosphorus is one of the most important biogenic components that determine the growth and development of algae, along with nitrogen. Wastewater phosphates are also likely to be a driver of such changes.
- The authors indicate that the reasons for the movement of mats to the east are still not entirely clear. However, are there any hypotheses on this issue?
- The authors discuss the rationality of using certain approaches to pixel analysis to assess the intensity of blooming. At the moment, apart from a comprehensive analysis, which of the proposed methods is more indicative? Or does each approach have its own advantages and disadvantages?
- Probably, in the methodological part it is worth mentioning who carried out the satellite imagery, what technological means were used to obtain the images and their further analysis.
- The presence of "green macroalgae blooms", mainly of the genus Ulva, is used in a number of European countries to assess the ecological status of water bodies (Wan AHL, Wilkes RJ, Heesch S, Bermejo R, Johnson MP, Morrison L (2017) Assessment and Characterisation of Ireland's Green Tides (Ulva Species). PLoS ONE 12(1): e0169049. https://doi.org/10.1371/journal.pone.0169049). Has similar work been carried out in the Yellow Sea? Perhaps this should be included as one of the future tasks in the study of green tides in this aquatic ecosystem.
Author Response
Comments 1: It would be good to provide some information about the biology of Ulva prolifera, the features of the life cycle, growth rates and biomass accumulation in the Introduction. Does this species have biotechnological potential?
Response: Thank you for this valuable suggestion. Following your guidance, we have expanded the Introduction to include a more detailed description of the life cycle features and biomass accumulation characteristics of Ulva prolifera. However, we have not included a detailed description of its general biological features, as the main objective of this paper is to investigate the long-distance transport process of Ulva prolifera. Green-tide macroalga hold significant biotechnological potential. Their biomass can serve as a sustainable feedstock for producing biofuels, high-value extracts (like ulvan polysaccharides), and agricultural fertilizers.
Comments 2: Figs. 1 and 4 - the scale is difficult to read. Figure 1 is placed in the manuscript in section 2 (lines 99-100), although the first mention and reference to it is given in section 3.1 (line 107). In Fig. 4, small font is used for dates. For Fig. 3 It is necessary to unify the font and writing of locations (some coordinates are given, some are not).
Response: Thank you for your valuable suggestions. We have revised the figures accordingly: repositioned Fig. 1, replaced Fig. 3, and replaced Fig. 4 with a direct citation of the original literature image. These modifications significantly improve the clarity and rigor of the manuscript.
Comments 3: It would be good to consider such an abiotic factor as the content of total phosphorus in sea waters. Phosphorus is one of the most important biogenic components that determine the growth and development of algae, along with nitrogen. Wastewater phosphates are also likely to be a driver of such changes.
Response: We sincerely thank the reviewer for this insightful suggestion. We fully agree that phosphorus is a critical abiotic factor influencing algal growth. In response to this comment, we have now incorporated a discussion on the role of total phosphorus on algal processes. Please see lines 373-375, Page 14.
Comments 4: The authors indicate that the reasons for the movement of mats to the east are still not entirely clear. However, are there any hypotheses on this issue?
Response: We thank the reviewer for this comment. We have now addressed the potential hypotheses regarding the eastward movement of the mats in the manuscript (lines 196-209, Page 7). Although the precise mechanisms behind this eastward movement are not yet fully understood, several hypotheses have been proposed in the field, and we have incorporated discussions on these existing theories.
Comments 5: The authors discuss the rationality of using certain approaches to pixel analysis to assess the intensity of blooming. At the moment, apart from a comprehensive analysis, which of the proposed methods is more indicative? Or does each approach have its own advantages and disadvantages?
Response: We sincerely thank the reviewer for raising this critical point regarding the rationality of pixel analysis methods for assessing algal bloom intensity. We fully agree that a comprehensive validation with precise in situ data would be essential for definitively ranking the performance of these methods. However, due to the current lack of high-resolution synchronous measured biomass data, we are unable to conduct a rigorous empirical comparison of the proposed methods in our study.
Comments 6: Probably, in the methodological part it is worth mentioning who carried out the satellite imagery, what technological means were used to obtain the images and their further analysis.
Response: We sincerely appreciate the reviewer's valuable suggestion. We have introduced an article with a detailed introduction to this content. For the revisions, please refer to lines 119-120, Page 3.
Comments 7: The presence of "green macroalgae blooms", mainly of the genus Ulva, is used in a number of European countries to assess the ecological status of water bodies (Wan AHL, Wilkes RJ, Heesch S, Bermejo R, Johnson MP, Morrison L (2017) Assessment and Characterization of Ireland's Green Tides (Ulva Species). PLoS ONE 12(1): e0169049. https://doi.org/10.1371/journal.pone.0169049). Has similar work been carried out in the Yellow Sea? Perhaps this should be included as one of the future tasks in the study of green tides in this aquatic ecosystem.
Response: Yes, similar research to that conducted in Europe using Ulva (genus) green tides to assess ecological status has been carried out in the Yellow Sea area.
As you cited, the study by Xia et al. (2023), published in the Journal of Sea Research under the title “Distribution of Ulva prolifera, the dominant species in green tides along the Jiangsu Province coast in the Southern Yellow Sea, China,” is representative of such research.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsReview of manuscript
The Yellow Sea Green Tides: Spatiotemporal Dynamics of Long-Distance Transport and Influencing Factors by
Fanzhu Qu, Bowen Sun, Ling Meng, and Tao Zou.
The authors analyze green tides in the Yellow Sea, which has experienced the world's largest green tides in 2007-2025. Unlike other global green tides, those in the Yellow Sea are characterized by long-distance drifting and an astonishing scale, which affects agriculture and tourism and cause economical losses. The authors summarize recent understanding of the spatiotemporal patterns of long-distance transport, interannual variability in bloom size, and the underlying mechanisms driving these fluctuations.
The authors analyze variations in the green tides using remote sensing and imaging from satellites.
Figure 5 is very informative.
I recommend this manuscript for publication with minor revision.
Some more discussion on the causes of appearance of Ulva prolifera would be helpful.
I recommend adding coordinates in Fig. 3 similar to Fig. 4.
Author Response
Comments: I recommend this manuscript for publication with minor revision.
Some more discussion on the causes of appearance of Ulva prolifera would be helpful.
I recommend adding coordinates in Fig. 3 similar to Fig. 4.
Response: Thank you for this insightful and constructive suggestion. Following your guidance, we have supplemented manuscript accordingly. The modified content can be found on Page 15, Lines 442-450 of the manuscript. We have also updated Figure 3 accordingly. However, due to layout considerations, we again decided not to include coordinate axes. Even in its current form, the figure effectively demonstrates the spatiotemporal distribution dynamics of Ulva prolifera within the same month.
Author Response File: Author Response.pdf
