Dear reviewers, 

First and foremost, we wanted to thank you both for your kind words and feedback on the manuscript. We have incorporated all general comments as well as suggestions. 

We have organized some answers to the specific questions that were raised: 

•    Question: “Table 1: Chl-c1+c2: MgDVP has very close retention time to chl-c1 and c2. All laboratories measured as only c1+c2?”

Answer: It is true that MgDVP has a retention time that is very close to that of Chl-c1 and Chl-c2, which can complicate separation depending on the analytical method applied. A common approach across many laboratories is therefore to combine these pigments. Since most of the datasets in this database did not separate, we chose to report them as a combined pool to ensure consistency and comparability across datasets.  

•    Remark on traceability of HPLC methodology:

Answer: Since the last manuscript, all co-authors were asked to provide all the information they could regarding the laboratory’s methodologies for the various cruises. This has resulted in a document, added to the supplementary material of the manuscript as well as the DOI for the data. Thank you for highlighting this as a possible issue for the scientific community. 

Again, thank you for taking the time to give constructive feedback - all the comments and suggestions have been greatly appreciated. We hope that the revised manuscript has improved. 

Updated response

Dear reviewers, 

First and foremost, we wanted to thank you both for your kind words and feedback on the manuscript. We anticipate that we have incorporated all general comments and suggestions. Below, we provide a detailed response to each comment. 

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Referee #1 (RC1): 

General comments

The authors compiled phytoplankton/ice algae pigment concentration data obtained from numerous cruises in the Arctic Ocean. The dataset encompasses the concentrations of chlorophylls and accessory pigments, which are beneficial for estimating phytoplankton community structure and validating ocean color sensors.

While the dataset is highly valuable, the investigation of data quality was limited to categorization based on the availability of pigments and metadata. Methods for HPLC measurement, such as those employed by Zapata et al. (2000) and Van Heukelem and Thomas (2001), as well as the HPLC system, solvent, extraction techniques, and other relevant information are criteria to compare concentrations from different laboratories. The author wrote these variations as uncertainties. Therefore, users have to trace original dataset or articles to know them. Although round-robin experiments have been conducted to compare results from different laboratories, not all laboratories participated in the experiments. Additionally, the sampling technique and measurement methods for ice algae pigments are not explicitly mentioned. I acknowledge the data correction among laboratories is challenging and I believe that the pigment concentrations in this dataset were analyzed using reliable methodologies. However, providing information on the methods employed by the data provider is beneficial for conducting further data analyses. In summary, the dataset presented in this paper is suitable for publication in ESSD after minor revisions of the manuscript and dataset.

Reply: We thank the reviewer for this valuable comment regarding the potential impact of methodological differences among laboratories on the comparability of pigment measurements. We agree that information on analytical protocols, including HPLC methods, instrumentation, extraction procedures, and other laboratory-specific practices, is important for users seeking to assess data comparability and fitness for particular applications.

In response to this comment, we contacted all contributing data providers and requested any available documentation describing the analytical methodologies used for their respective cruises and datasets. The information received has now been compiled into a dedicated methodological document, which has been added to both the manuscript supplementary material and the dataset repository associated with the DOI. This additional documentation provides users with greater transparency regarding the analytical approaches employed and facilitates more informed use of the dataset. We appreciate the reviewer highlighting this aspect, as we agree that making this information readily accessible will increase the value and usability of the dataset for the broader scientific community.

Specific comments

Through the manuscript, "a", "b", and "c" of chlorophylls are sometime not italicized. Pigment names were repeatedly abbreviated. Please check them.

Reply: We have carefully checked the naming and abbreviations for any inconsistency and those were corrected accordingly.

L121-122: Absorption and scattering coefficients of phytoplankton are estimated from reflectance. They are not directly detected by radiometers.

Reply: We thank the reviewer for this correction. The text has been revised to clarify that phytoplankton absorption and scattering coefficients are estimated from reflectance measurements rather than being directly measured by radiometers.

Table 1: What are Dinoflagellates-1 and 2?

Reply: We thank the reviewer for this question. The terms Dinoflagellates-1 and Dinoflagellates-2 refer to pigment-based subgroups of dinoflagellates used in CHEMTAX analyses. These groups are distinguished by differences in their characteristic accessory pigment composition, particularly the relative abundance of peridinin (Peri), fucoxanthin (Fuco), and 19'-hexanoyloxyfucoxanthin (Hex-fuco). Dinoflagellates-1 represents the peridinin-containing dinoflagellates, whereas Dinoflagellates-2 includes non-peridinin dinoflagellates. We have clarified this distinction in Table 1 and the accompanying text.

Table 1: Chl-c1+c2: MgDVP has very close retention time to chl-c1 and c2. All laboratories measured as only c1+c2?

Reply: It is true that MgDVP has a retention time that is very close to that of Chl-c1 and Chl-c2, which can complicate separation depending on the analytical method applied. A common approach across many laboratories is therefore to combine these pigments. Since most of the datasets in this database did not separate, we chose to report them as a combined pool to ensure consistency and comparability across datasets. This approach maximizes consistency and comparability across the diverse datasets included in the database. 

L155: Hayward et al. (2025)? The paper in 2024 is study in the Southern Ocean.

Reply: Hayward et al 2024 was a citation error and the reference has been removed.

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Referee Vanda Brotas (RC2)

General comments:

Firstly, I would like to underline the extreme relevance of a publication such as this one. As reliable and comprehensive datasets are essential to evaluate the state of our ecosystems; Arctic region is obviously a key area regarding the effects of climate change. A dataset as the present one is very useful to future studies. I think this work is very useful for scientists studying the oceanic phytoplankton, not only the ArcticI think it should be published in ESSD.

Reply: We sincerely thank the reviewer for the positive and encouraging assessment of our work. We greatly appreciate the recognition of the importance of reliable, comprehensive datasets for understanding Arctic marine ecosystems and their response to climate change. We are especially pleased that the reviewer finds the dataset valuable for the broader scientific community studying oceanic phytoplankton. We also thank the reviewer for recommending the manuscript for publication in ESSD.

Specific comments

Line 100 - for this very broadly and general sentence, I am sure that the paper you cite, from 2022, is not the first one to state this...  

Reply: An additional reference has been added to state how Chl-a drives photosynthesis.

Line 227/228 – Could you rephrase for clarity?

Reply: The sentence was rephrased for clarity.

Line 352/354 – Authors state The Fuco-derivatives, But-fuco and Hex-fuco, both considered diagnostic markers of haptophytes, had a stable distribution throughout the year, aside from notable peaks in November. Additionally, Hex-fuco had a higher overall proportion than But-fuco, implying higher proportion of dinoflagellates.Last sentence should be clarified, indeed in Table 1, Hex-Fuco is associated with Haptophytes and Dinoflagellates, but the paragraph, as it is, is ambigous.

Reply: We thank the reviewer for this comment. The sentence has been removed from the manuscript, as it reflected interpretation of the data rather than a direct description of the observations and could introduce ambiguity in the context of this data-focused publication.

Please check consistency with pigments abreviations, ex: Peridinin, is Peri (Table 1) and Perid in the text. I suggest following Roy et al 2012 abbreviations

Reply: Consistency in pigment abbreviations were corrected.

Again, thank you for taking the time to give constructive feedback - all the comments and suggestions have been greatly appreciated. We hope that the revised manuscript has improved.