Please refer to the PDF for more details regarding all the following comments.

1. Does the paper present novel concepts, ideas, tools, or data?

   Partially. While the paper presents a bloom that has not been previously reported, the novelty and value of the dataset could be better emphasized. Highlighting the unique aspects of cruises strategy would underline the distinctiveness of the data collected.

2. Are substantial conclusions reached?

   Yes, but the discussion section needs improvement to better articulate the connection with the physical seascape.

3. Are the scientific methods and assumptions valid and clearly outlined?

   No. The authors need to clearly state their hypotheses in the introduction and then outline the methods used to test them.

4. Are the results sufficient to support the interpretations and conclusions?

   Yes, I think they are, but reworking the manuscript will make this link clearer and more convincing. Particularly, by discussing more about the story tell by Lagrangian simulations.

5. Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results)?

   No. The methods section requires more detailed descriptions about the strategy of cruises and methods.

6. Do the authors give proper credit to related work and clearly indicate their own new/original contribution?

   No. While I believe this work is original as mentioned earlier, reworking the manuscript would help clearly highlight that.

7. Does the title clearly reflect the contents of the paper?

   Yes, but the retention process should be described in more detail within the discussion to align fully with the title's focus.

8. Does the abstract provide a concise and complete summary?

   Yes.

9. Is the overall presentation well structured and clear?

   Not entirely. While the paper has valuable content, there are some spelling errors, inconsistencies (e.g., units, figures), and long sentences. Additionally, the structure could be improved to enhance clarity and coherence.

10. Is the language fluent and precise?

    No. See pdf.

11. Are mathematical formulae, symbols, abbreviations, and units correctly defined and used?

    No. See pdf.

12. Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?

    No. See pdf.

13. Are the number and quality of references appropriate?

    No. See pdf.

14. Is the amount and quality of supplementary material appropriate?

    Yes.

General comments

The reviewed paper is a very good contribution that should be published, not only because it is well written, but because it very appropriately addresses the topic of the Amphidomataceae bloom, particularly since it is an offshore event in the Atlantic Ocean and has a large geographic coverage. There are many contributions on harmful blooms in coastal waters. The study not only includes field observations, but also considers the use of satellite images, oceanographic and molecular aspects and various technologies that enrich the scientific content.

This is a contribution that should be published, and with minor modifications.

Specific comments

I am struck by the title of the contribution, since it does not appear Amphidomataceae (Azadinium, Amphihdoma) and neither does the fact that the bloom in question occurs in South America, the Argentine sea shelf. Given the scarce contributions on these topics, i.e. non-coastal blooms, and in a geographic sector in which fewer scientific contributions are published, this is a fact that calls attention. It is suggested to evaluate the feasibility of changing the title considering Amphidomataceae and the geographical area in which the study was carried out.

Another aspect of a specific nature, but which depends both on the editorial policy of the journal in which the article is intended to be published, and on the authors' own interests, refers to the information on all the taxonomic aspects related to the Azadinium and Amphidoma taxa that are included as an appendix (Appendix A). Although it is not something substantial, I have the impression that these aspects should be considered as an independent publication, leaving in it only that which refers to the multispecies Amphidomataceae bloom.

In the discussion, in the point 4.2., in the final part, when the authors contrast the platforms and oceanographic conditions on the Atlantic and Pacific coasts of the southern tip of South America, the information provided in the text is too limited, both from a topographic and oceanographic point of view, and aspects such as the platform characteristics, which is noticeably smaller in size, on the Pacific coast and the marked differences between the Humboldt and Malvinas currents, and the processes associated with phytoplanktonic blooms, should be included, beyond the fact that both currents originate from the Antarctic circumpolar current. These differences have implications for stability, retention, accumulation and oceanographic conditions in general, and a discussion on how these conditions can determine marked differences in the expressions of Amphidomataceae blooms on both coasts of South America, such as the records of abundance, and that these blooms occur at such notable distances from the coast, in the case ot the Atlantic secot.

Other corrections

With regard to figure 2, the text (since line 261) is missing the inclusion of maximum values? ​​or ranges of Chl-a concentrations and surface temperatures, since the figure 2 do not provide details regarding these aspects. And in the same figure, although a, b, c, and d are indicated in the legend, this detail should be included in each box of the figure.

Although in general the contribution is well presented and ordered as corresponds to scientific texts, there are minor errors, particularly in the scientific names of Azadinium species, e.g. lines 342, 484 and 489

On the other hand, in line 536 it says Hernández-Carrazco, it should say Hernández-Carrasco.,