The article “MAREL Carnot data and metadata from Coriolis Data Center” describes a long-term (2004 - 2022) dataset acquired in a fixed meteo-oceanographic coastal station located in the Eastern English Channel. The purpose of the paper is to describe the dataset, the parameters measured and the several steps of data validation required to obtain the final quality checked dataset which is indicated to be available and which is used to produce the figures presented in the article. The manuscript also provides an overview of studies using the dataset. Availability of time series of multidisciplinary marine environmental data collected at high-frequency, such as those from the MAREL Carnot station, is indeed valuable to study temporal dynamics of physical, biogeochemical and biological processes, to integrate discrete monitoring and to provide information useful for environmental status assessment. On the other hand, long term and continuous operation of multiple sensors, especially in coastal areas, stable and continuous data transmission and data quality still represent challenges for long term data availability. Accordingly, the objective to provide long term validated multidisciplinary data is very relevant.

However, the manuscript and, even more, the dataset present serious weaknesses which should be seriously addressed before considering publication in Earth System Science Data.

Dataset:

General comments:

The dataset available on the website does not correspond to that described in the article. In fact, data available online are not validated as described in the article (sections 3.3 and 3.4): there are no Quality Codes related to the measured parameters, the calculated parameter (e.g. oxygen saturation) mentioned in the text is not present in the dataset, many data are well above “sensor range” and “expert range”. This suggests that the dataset available on the website has not been validated, at least not according to the method described in the text.

Furthermore, the statistics summary (Tab. 3) presents data higher than the ranges used for data validation. Thus, it is not clear if the described processing has been applied to the dataset or not.

This is the major issue for a contribution to Earth System Science Data.

Specific comments:

Is the data set accessible via the given identifier? The doi gives access to raw data, or data that do not correspond to what is described in the manuscript.

Is the data set complete? No, there are no quality codes, no information on sensors/instruments used over such a long time.

Are error estimates and sources of errors given (and discussed in the article)? Only weakly. There are no indications on instruments used, which may have changed over time, neither if sensor calibrations have been regularly performed.

Are the accuracy, calibration, processing, etc. state of the art? There is no indication if sensors have been regularly calibrated.

Are common standards used for comparison? There is no mention.

The dataset cannot be used as it is as it requires the validation procedure described in the text. It can be useful once data Quality Control procedures are carried out and once information on acquisition protocols and on sensor calibration are made available. The lack of this information limits the use of this dataset for quantitative assessment of long-term variability.

A legend explaining the codes used in the dataset for the parameters is needed to understand what are the variables listed.

Manuscript:

General comments:

In its current form, the manuscript requires a deep formal and content revision. The text is not compliant with a scientific paper, the formal aspects need revision and English editing. Many parts need rephrasing. One relevant literature is missing, some statements are incorrect, or incorrectly attributed to the listed references and not supported by evidence. There is no information on which sensors were used over the almost 20 years, if they have changed, if they have been calibrated. This is very important for long term time-series. Pay attention to the use of punctuation and of conjunctions, avoid/limit the use of “in other words”, “in general” which are not suitable for a scientific text, 

It is recommended to reorganize the whole section presenting the review of studies using MAREL Carnot data (from page 14 to 16), in order to better highlight approaches, research objectives and benefits.

There are no references to already well consolidated data Quality Control procedures:

•    e.g. Intergovernmental Oceanographic Commission. (1993). Manual of quality control procedures for validation of oceanographic data.

•    Bushnell, M. (2015, October). Quality assurance/quality control of real-time oceanographic data. In OCEANS 2015-MTS/IEEE Washington (pp. 1-4). IEEE.

•  SeaDataNet (2010) SeaDataNet: Data Quality Control Procedures, Version 2.0. Available via DIALOG https://www.seadatanet.org/Standards/Data-Quality-Control.

According to consolidated data validation procedures (e.g. SeaDataNet, 2010), the outcomes from data validation consist in assigning Quality Flags (or Quality Codes), without modifying or removing original data. The removal of data (regarded of bad quality) is highly controversial because once data are removed, they are lost; conversely, data quality definition is in someway subjective and data considered of bad quality could, in some cases, provide information on extreme events.

Specific comments:  

Please see the attached file. Parts highlighted in pink need rephrasing. Comments are included in the pdf.

Please carefully revise and integrate section 3.4 (3.4.1, 3.4.2, 3.4.3, 3.4.4) which is very relevant for a data paper.

What are “major errors”? How is Quality Code Correction done? How are QC assigned? How is temporal alignement carried out?

Page 16: Huang & Schmitt 2014 do not deal with what is here stated.

Alain & David 20220 not cited

In Conclusion (and also before): the link between fluorescence (which is measured) and HAB (Harmful algal blooms) is not so straightforward. Statements need to be carefully revised.

The paper serves a useful function of introducing the MAREL Carnot database to a broader community of users. It provides a description of the measurements taken and duration of records.  It also provides several illustrative examples of how the data have been used in publications that advance understanding. These data will certainly have many future uses in scientific research, monitoring and forecasting. What is less clear is how they can be effectively used to improve policies and management, for example in achieving the objectives of the WFD and MSFD, beyond documenting ecological status and trends.  Adding a short paragraph discussing how results could be used, e.g., in models that help set goals and guide adaptive management, would be helpful.

The manuscript would also benefit for some more English language editing.  Some detailed comments below point out some examples. 

Detailed editorial comments:

20  sends not send

21–23  use present tense, i.e. demonstrate and show.

28  phytoplankton is not phytoplanktons are

40–42 “marine environment, they are of insufficient temporal resolution to advance understanding of phytoplankton dynamics and eutrophication.”

45–46 repetitive

54  Is it essential biodiversity variables (EVB), as used later, or important biodiversity variables (IVB)?

60  mucopolysaccharides or muco-polysaccharides, not mucco

68  French not French

77  In 2004 the MAREL Carnot monitoring station was installed in the French part of the English Channel.

101  ECC has a macro-tidal regime

105  mass that hugs the shore.  How far offshore does this coastal water mass extend?

108  Why isn’t it the case that spring tide are stronger than neap tides?

132  Hence, some data for the year . . .

241  Is there some text missing ahead of this paragraph, because the “indeed” doesn’t follow from the earlier paragraph?

242–243  These sentence doesn’t make much sense. Surely, nutrient concentrations are not made from space.  Maybe restate this as “MAREL Carnot performs some measurements that are not made from space such as for nutrient concentrations.”

250  Don’t need another “indeed” here.

257  their rather than his