Seasonal Variability in Present-Day Coccolithophore Fluxes in Deep Eastern Mediterranean Sea: A Multi-Year Study (2015–2017) of Coccolithophore Export in SE Ionian Sea at 4300 m Depth

Round 1

Reviewer 1 Report

This work is a follow-up of previous work by the (largely) same team of authors. Overall, the paper offers little novelty and falls into the category of 'useful confirmation'. The most interesting part is the comparison of the Nestor site with the second, shallower sampling site in the Eastern Mediterranean Sea. Major weaknesses are that there is no hypothesis, the research goals remain rather vague and the paper is exclusively descriptive. The style is wordy, beginning with the Abstract (too long, 339 words). Detailed descriptions of the water masses (section 1.1) are not needed. The Discussion lacks focus. The English needs to be improved throughout the text.

Author Response

-Reviewer 1

This work is a follow-up of previous work by the (largely) same team of authors. Overall, the paper offers little novelty and falls into the category of 'useful confirmation'. The most interesting part is the comparison of the Nestor site with the second, shallower sampling site in the Eastern Mediterranean Sea. Major weaknesses are that there is no hypothesis, the research goals remain rather vague and the paper is exclusively descriptive. The style is wordy, beginning with the Abstract (too long, 339 words). Detailed descriptions of the water masses (section 1.1) are not needed. The Discussion lacks focus. The English needs to be improved throughout the text.

All changes in the text have been corrected as suggested by the reviewers. We corrected a numerical error in the flux calculation (split factor parameter). Consequently, the flux numbers have been modified but the species contribution to total coccolithophore flux remained the same. We changed the discussion according to all comments of the three reviewers.

We made the research goals more clear (Lines 60-64). The discussion was reorganised to support the aim of the study and to provide focused sub-chapters. The detailed descriptions of the water masses were removed (Lines 82-91). We improved the English and wordy style of the manuscript.

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

-Reviewer 2

 In the manuscript entitled “Seasonal Variability in Present-Day Coccolithophore Fluxes in Deep Eastern Mediterranean Sea: A Multi-Year Study of Coccolithophore Export Production in SE Ionian Sea at 4300 m Depth” by Hayat et al., the authors show the coccolith flux displays a seasonal variability with high a flux during the late winter-early spring, and a low flux during summer. The dominant species of heterococcoliths that contribute to the coccolith flux were observed and compared at 4300 m and 2000 m, and Emiliania huxleyi and Florisphaera profunda were the most abundant species. The authors propose the difference is attributed to lateral advection, resuspension, and/or the influence of Eastern Mediterranean Deep Waters. Overall, the experimental data are well presented, and the subject is appropriate to the journal. Therefore, this manuscript can be published in Journal of marine Science and Engineering after a minor revision.

All changes in the text have been corrected as suggested by the reviewers. We corrected a numerical error in the flux calculation (split factor parameter). Consequently, the flux numbers have been modified but the species contribution to total coccolithophore flux remained the same. We changed the discussion according to all comments of the three reviewers.

1. L66-72, the novelty of this work should be strengthened. This paragraph needs to be fully clarified for the necessity of this study.
   Reviewer is right, we modified the paragraph as suggested (Lines 56-64).
2. Physico-chemical characteristics of the sediment samples should be provided in the Materials and Methods section.
   We added satellite environmental data (precipitation, sea surface temperature, Chl-a) in the Materials and Methods (Lines 93-99) and Results (Lines 136-142) sections. Those data were used in the Discussion section to strengthen the findings of the present study.

3. L293, the comparison of the coccolith fluxes at 2000 m (by Skampa et al.) and 4300 m (by this study) is not accurate, despite overlap with the time of the present study. Please highlight factors for the seasonal variability of the coccolith flux at 4300 m depth.
   We changed the discussion (section 4.2 “Comparison of coccolith fluxes at 2000 m and 4300 m for the 2015 sampling interval”) according to the comments of the reviewer. A better explanation of the correlation between the two different depth fluxes has been added to the discussion (Lines 232-269) and also supported by performing a statistical correlation (Figure 4a).

4. L351-373, the conclusions are too scattered to be concise. Please recondense the conclusions to 3-4 points.
   We rephrased the conclusions as suggested (Lines 282-294).

Reviewer 3 Report

Dear Authors,

You have addressed a nice and relevant research question, and provided a nice dataset accordingly. However, I have the following concerns about your results:

1. the methods you have used to make quantitative analysis sound a bit odd. My main concern is: how can you be sure that on the filter media the coccoliths are evenly distributed and why you did not use SEM for counting or transects etc. 

2. the time series dataset you have provided has 2 long time periods not covered with data. I haven't seen any data analysis method which show how you cope with this gaps. Namely: how can you be sure that there were no peaks in the coccolith production during the time periods not covered by sampling?

3. the gaps make your discussion more or less hypothetical, because the winter periods are undersampled. Moreover you compare two datasets with timegaps, and there is  not a single statistical evaluation of the reliability of the comparison, not even some calculations as regards the trends in the fluxes studied.

4. Data analysis: quantitative data should be compared using statistical methods. Correlation matrix would have been the simplest to compare your data. There is no correlation coefficient calculated etc. Just a simple visual correlation is not enough.

Correcting these flaws would make your manuscript a nice paper!

Please find detailed comments in the attached annotated manuscript file.

I wish you good luck and nice work!

Censor Anonymous

Author Response

-Reviewer 3

Dear Authors,

You have addressed a nice and relevant research question, and provided a nice dataset accordingly. However, I have the following concerns about your results:

1. the methods you have used to make quantitative analysis sound a bit odd. My main concern is: how can you be sure that on the filter media the coccoliths are evenly distributed and why you did not use SEM for counting or transects etc.
   For the coccolithophore analysis, standard sample preparation and Light Microscopy techniques followed the methodology of previous sediment trap studies in the Eastern Mediterranean in order to ensure the accuracy of data comparison (Lines 122-124).
2. the time series dataset you have provided has 2 long time periods not covered with data. I haven't seen any data analysis method which show how you cope with this gaps. Namely: how can you be sure that there were no peaks in the coccolith production during the time periods not covered by sampling?
   The reviewer is absolutely right about the sampling gaps. However, previous studies in the E. Mediterranean Sea (e.g. Triantaphyllou et al., 2004, Malinverno et al., 2014, Skampa et al., 2020) displayed the same seasonal pattern in coccolithophore fluxes as the one presented in our study. In addition, Stavrakakis et al. (2013), showed that a similar seasonality was followed in the Nestor site for the interval 2006-2010. Since that unfortunately, there were not samples available for the gap intervals, we tried to use our data with caution, assuming that the overall trend remains the same.
3. the gaps make your discussion more or less hypothetical, because the winter periods are undersampled. Moreover you compare two datasets with timegaps, and there is not a single statistical evaluation of the reliability of the comparison, not even some calculations as regards the trends in the fluxes studied.
   We performed a correlation between the total coccolith fluxes recorded at 2000 m with their fluxes at 4300 m during 2015 (Lines 234-236, Figure 4a), to prove the common seasonal trends of the two depths.
4. Data analysis: quantitative data should be compared using statistical methods. Correlation matrix would have been the simplest to compare your data. There is no correlation coefficient calculated etc. Just a simple visual correlation is not enough.
   Reviewer is right, we carried out a correlation between the total coccolith fluxes recorded at 2000 m with their fluxes at 4300 m during 2015, showing a statistically significant common monthly pattern between the two studied depths (Lines 234-236, Figure 4a).

All changes in the text have been made according the suggestions of the reviewers. Additionally, we corrected a numerical error in the flux calculation (split factor parameter). Consequently, the flux numbers have been modified but the species contribution to the total coccolithophore flux remained the same. We changed the discussion according to all comments of the three reviewers.

Round 2

Reviewer 1 Report

I acknowledge that the revision improved this manuscript. However, some major issues remain. Apart from the lack of novelty, which cannot be overcome at this stage, the structure, style and language of this manuscript are poor. Most parts of the Abstract must be written in past tense, not present tense.  Some clauses are all but clear; I give two examples: (1), lines 63-4, "...(c) compare the coccolithophore fluxes from the Nestor site different water column depths to determine potential alterations in the sinking coccolithophore assemblages."; (2), lines 157-8, " In total 19 species of heterococcoliths were identified in the studied samples (see Table 2) with E. huxleyi being the dominant."(meaning, E, huxleyi was the dominant sample??).  Section 3.1 is not on Satellite parameters but describes Chl a levels obtained by satellite measurements. Lines 279-91 do not represent conclusions and should be removed.

Author Response

Reviewer 1:

I acknowledge that the revision improved this manuscript. However, some major issues remain. Apart from the lack of novelty, which cannot be overcome at this stage, the structure, style and language of this manuscript are poor. Most parts of the Abstract must be written in past tense, not present tense.  Some clauses are all but clear; I give two examples: (1), lines 63-4, "...(c) compare the coccolithophore fluxes from the Nestor site different water column depths to determine potential alterations in the sinking coccolithophore assemblages."; (2), lines 157-8, " In total 19 species of heterococcoliths were identified in the studied samples (see Table 2) with E. huxleyi being the dominant."(meaning, E, huxleyi was the dominant sample??).  Section 3.1 is not on Satellite parameters but describes Chl a levels obtained by satellite measurements. Lines 279-91 do not represent conclusions and should be removed.

“lack of novelty” Novelty is strengthened in lines: 57-67.

“language of this manuscript” Editing of English language was performed and the text has been modified accordingly, e.g., see 4.1, 4.2.

“Most parts of the Abstract must be written in past tense, not present tense” Done as suggested.

“(1), lines 63-4, "...(c) compare the coccolithophore fluxes from the Nestor site different water column depths to determine potential alterations in the sinking coccolithophore assemblages."” We rephrased for better understanding.

“(2), lines 157-8, " In total 19 species of heterococcoliths were identified in the studied samples (see Table 2) with E. huxleyi being the dominant."(meaning, E, huxleyi was the dominant sample??)” We rephrased the sentence.

“Section 3.1 is not on Satellite parameters but describes Chl a levels obtained by satellite measurements” We corrected the section 3.1 as suggested.

“Lines 279-91 do not represent conclusions and should be removed.” A better clarification of the paragraphs was added in order to represent conclusions (lines 285-307).