The paper 'The Mediterranean observation systems: MonGOOS analysis of present capabilities, weaknesses and perspectives' by Vargas-Yanez et al. presents a complete and detailed inventory of the ocean observation capabilities in the Mediterranean. The analysis was conducted within the framework of MonGOOS, an international organization dedicated to the coordination of Mediterranean ocean observing systems. The paper provides a detailed and accurate snapshot of the Mediterranean observing systems, highlighting the strengths and weaknesses of the current system.

I really appreciated the paper, as such inventories are difficult to realize due to the fragmentation of observation efforts in Europe. The method is robust, well-explained, and helps non-expert users find their way in the intricate and somewhat incomprehensible world of ocean observation. Additionally, they provide a complete explanation of the governance and organizational framework, which, even for an expert, can sometimes be hard to appreciate.

However, I expected the conclusions to go a little further. Some of the suggestions, derived from the weaknesses identified by the analysis, are certainly true, although somewhat rather generic (e.g., “increase observations in the eastern part of the basin, augment funding and personnel involved, etc.”). Such messages are essential, and there is no doubt that they must be addressed. However, from a consortium of more than 30 scientists, I expected a little more.

I sketch below some points that could be addressed by the authors. They are not mandatory for final publication, but I strongly suggest, at least, treating them partially, as the final relevance of the paper will, in my opinion, be strongly augmented.

I also suggest substantially reducing the initial part of the paper, where definitions and descriptions of the platforms are provided. Although I found it very interesting and well done, this section is not essential for the rest of the paper and could be moved to supplementary material, retaining only the main messages (and Figure 1) in the main text.

Here are some suggestions to improve manuscript relevance:

1. It would be really informative to have a bibliographic study of the MonGOOS system as a whole, as well as for each sub-system. An interannual evolution of some bibliographic parameters would also be highly informative. The idea here is not to rank the "best" systems, but to inform non-expert users that MonGOOS systems are real scientific tools, essential not only for data collection but also for advancing ocean knowledge.
2. I understand that most observing systems are developed at the national (or sometimes laboratory) level, and that basin-scale coordination is only possible a posteriori rather than a priori. Nonetheless, I was surprised that an objective analysis of the systems was not included. OSSE and OSE methods provide scientific and effective tools to assess the relevance and usefulness of observing systems. Other approaches (e.g., bioregionalization, correlation analysis, temporal and spatial scale analysis, etc.) could also be used to evaluate the performance (and, more importantly, the weaknesses) of a system and to provide guidance for future improvements. Again, the goal here is not to prioritize systems, but to offer insights for further enhancements.
3. Similarly, apart from generic statements (e.g., "increase biogeochemical observations"), no specific indications are provided regarding the evolution of the system in terms of parameters. Cost is clearly the most significant limiting factor, preventing the expansion of parameters in observing systems. However, even if no additional resources are allocated in the coming years, I believe it is important that such analyses be performed in papers like this one.

Again, these are only suggestions, as I consider the paper ready for publication with minor revisions:

Line 395: As mentioned earlier, I suggest reducing the chapter “Current observation capabilities” and moving most of the text to the appendix or supplementary material.

Line 275: For the sake of completeness, also cite surface autonomous devices.

Figure 2: I have some issues with the legend: where are the blue dots? The colors of the bars are not clearly explained.

General comment on figures and tables: I am not convinced that systems not yet deployed (even if funded) should be included in the figures and tables. The future is always uncertain, especially for ocean operations, and secured funding does not guarantee that observing systems will ultimately be deployed. Adding planned systems/points to the figures could be misleading for non-expert readers. I strongly suggest removing them.

Table 5, Second row: The entry should be “Ajaccio” (not “AJACCIOI”). Unless the authors opt to use Corsican, in which case the correct form is “Aiacciu”.

Table 6: I strongly suggest indicating in the table the maximum depth of the stations available for each cruise. Sometimes, even if the bottom depth is great, data are only obtained at the surface or at intermediate depths. For non-expert readers seeking information, this detail could be useful in identifying the most suitable systems for their scientific purposes. Another useful indicator could be the number of stations exceeding 1000 meters depth.

Table 7, Third row: “CNRS/IFREMER” is repeated three times.

Line 821: It would be really informative for non-expert readers to explicitly explain the difference between EOOS and EuroGOOS.

Line 880: Maybe I missed something (it is true that the paper is full of acronyms, a glossary would be really useful), but I am surprised that the authors, in their comprehensive overview of the puzzling governance framework, did not cite specific national coordination initiatives such as Fr-OOS (froos.fr) or It-IOOS (it-ioos.eu). It would also be important to somehow mention the GOOS reform project (goosocean.org/news/call-for-proposals-global-ocean-observing-system-reform-consultancy), which will likely impact the governance of all sub-regional and regional systems, such as MonGOOS.

The manuscript presents MonGOOS, the regional alliance centered on ocean observing systems in the

Mediterranean Sea. The study is grounded in a census of these systems, conducted in consultation with regional

observation actors across the basin. The consultation methodology is clearly framed, which strengthens the

openness and thoroughness of the inventory. While the manuscript section ordering is classical, it is clear and

logical, and effectively supports the paper's central aim. I particularly appreciated the contextualization effort

given to (i) describe observing systems, (ii) MonGOOS's role within the broader system of global and regional

alliances, and (iii) the authors' justification of the chosen terminology. Overall I think the paper fits its central

purpose and will be useful for the community and recommends acceptance with minor revisions based on the

two subsequent points.

My principal criticism concerns the stated goal of “analyzing the current state of the Mediterranean observation

capabilities" to "evaluating strengths and weaknesses to outline a path for future development," (l175-180) which

I find presently under-done, given its prominence as a primary aim of the paper. A complete assessment of

strength and weaknesses of the observing system would compare modes of ocean variability against existing

observational capabilities, in terms of both resolution and spatio-temporal coverage. I do acknowledge that such

an analysis is not feasible for each and every EOV at the scale of the Mediterranean basin (especially at the

paper level). I find that this point could be tuned down or discussed as a perspective. As an alternative approach,

I suggest the authors connect their manuscript more explicitly to the official EOV framework

(https://doi.org/10.3389/fmars.2026.1737002). Stating for instance which EOVs fall within MonGOOS's scope ;

which EOVs should be better observed for societal needs ; and quantifying how often each EOV is addressed by

observing systems. These simple additions would allow to quantitatively pinpoint underrepresented variables or

categories of variables (physical, biogeochemical, and ecology & ecosystem) and would grant a firmer basis to

the discussion section.

Second, I think the manuscript's form requires tightening. Figures could be improved for aesthetic clarity and, in

some cases, modified to better serve their intended purposes. These issues are flagged in the specific comments

below. While the manuscript's ideas flow smoothly, I found the writing quality to be uneven. Many sentences need

rewriting (e.g., in the section on infrastructures) for typos, grammatical errors, repetition, and inconsistencies.

Sections are also not sequential with section 4.6 appearing twice. Finally, there are inconsistencies in the references

that reference-management software (e.g., Zotero) should easily resolve (e.g., "Milglietta" instead of "Miglietta";

"Liubarsteva" vs. "Liuvaresteva"). These issues are itemized in the technical corrections below.