PONE-D-20-34799

Effects of sea ice and wind speed on Phytoplankton spring bloom in Central and Southern Baltic Sea

PLOS ONE

Dear Dr. Pärn,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Both the reviewers have offered critical comments and have suggested major revision. The methodology followed and the inferences are also questioned. In view of such a review, though a major revision is suggested, authors need to convincingly answer the comments and take up much needed appropriate revision, for a fresh round of review.

Please submit your revised manuscript by Jan 10 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Arga Chandrashekar Anil, Ph. D., D. Agr.,

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that there are some minor issues with English grammar and language usage. Such examples include, but are not limited to: "In recent years have been mainly mild winter." (line 101). While we do not feel that these are prevalent enough to necessitate the use of a professional editing service, we suggest that you have a native English speaker review and edit the text for you.

3.Thank you for stating the following financial disclosure:

 [The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.].

At this time, please address the following queries:

1. Please clarify the sources of funding (financial or material support) for your study. List the grants or organizations that supported your study, including funding received from your institution.
2. State what role the funders took in the study. If the funders had no role in your study, please state: “The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”
3. If any authors received a salary from any of your funders, please state which authors and which funders.
4. If you did not receive any funding for this study, please state: “The authors received no specific funding for this work.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

4. We note that [Figure(s) 10 and 12] in your submission contain map images which may be copyrighted. All PLOS content is published under the Creative Commons Attribution License (CC BY 4.0), which means that the manuscript, images, and Supporting Information files will be freely available online, and any third party is permitted to access, download, copy, distribute, and use these materials in any way, even commercially, with proper attribution. For these reasons, we cannot publish previously copyrighted maps or satellite images created using proprietary data, such as Google software (Google Maps, Street View, and Earth). For more information, see our copyright guidelines: http://journals.plos.org/plosone/s/licenses-and-copyright.

We require you to either (1) present written permission from the copyright holder to publish these figures specifically under the CC BY 4.0 license, or (2) remove the figures from your submission:

1.    You may seek permission from the original copyright holder of Figure(s) [10 and 12] to publish the content specifically under the CC BY 4.0 license. 

We recommend that you contact the original copyright holder with the Content Permission Form (http://journals.plos.org/plosone/s/file?id=7c09/content-permission-form.pdf) and the following text:

“I request permission for the open-access journal PLOS ONE to publish XXX under the Creative Commons Attribution License (CCAL) CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). Please be aware that this license allows unrestricted use and distribution, even commercially, by third parties. Please reply and provide explicit written permission to publish XXX under a CC BY license and complete the attached form.”

Please upload the completed Content Permission Form or other proof of granted permissions as an "Other" file with your submission.

In the figure caption of the copyrighted figure, please include the following text: “Reprinted from [ref] under a CC BY license, with permission from [name of publisher], original copyright [original copyright year].”

2.    If you are unable to obtain permission from the original copyright holder to publish these figures under the CC BY 4.0 license or if the copyright holder’s requirements are incompatible with the CC BY 4.0 license, please either i) remove the figure or ii) supply a replacement figure that complies with the CC BY 4.0 license. Please check copyright information on all replacement figures and update the figure caption with source information. If applicable, please specify in the figure caption text when a figure is similar but not identical to the original image and is therefore for illustrative purposes only.

The following resources for replacing copyrighted map figures may be helpful:

USGS National Map Viewer (public domain): http://viewer.nationalmap.gov/viewer/

The Gateway to Astronaut Photography of Earth (public domain): http://eol.jsc.nasa.gov/sseop/clickmap/

Maps at the CIA (public domain): https://www.cia.gov/library/publications/the-world-factbook/index.html and https://www.cia.gov/library/publications/cia-maps-publications/index.html

NASA Earth Observatory (public domain): http://earthobservatory.nasa.gov/

Landsat: http://landsat.visibleearth.nasa.gov/

USGS EROS (Earth Resources Observatory and Science (EROS) Center) (public domain): http://eros.usgs.gov/#

Natural Earth (public domain): http://www.naturalearthdata.com/

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The manuscript titled “Effects of sea ice and wind speed on Phytoplankton spring bloom in Central and Southern Baltic Sea” by Parn et al. describes a model study of the phytoplankton spring bloom composition in the Central and Southern Baltic Sea in relation to ice cover. Experiments with an established hydrodynamic–biogeochemical model (GETM + ERGOM) lead the authors to an interesting conclusion that in years with sea ice - dinoflagellates dominate in the phytoplankton biomass and, vice versa, in years with no sea ice - diatoms dominate. The authors then extrapolate that into the future when diatoms are expected to dominate as ice will almost certainly either disappear or become rare in the Southern and Central Baltic Sea due to climate change. These conclusions are certainly interesting and even intriguing. The explanations given by the authors make sense but it remains puzzling for the world ocean where many areas never experience ice but have with huge dinoflagellate blooms and, on the contrary, areas of the Arctic and Antarctic oceans with ice are often dominated by diatoms. It is difficult to understand why the Baltic Sea would be such a peculiar case. In my opinion the modeling study has been performed at high professional level and I cannot find any technical problems that would be producing those intriguing results. However, it is quite possible that the inherently crude parametrization of the dynamics of diatom and dinoflagellate populations leads to these model results. Natural diatom and dinoflagellate populations have huge variations in their characteristics, e.g. cell size, growth and sinking speed, vertical mobility, etc. and parameters fixed to some estimates may not lead to realistic outcomes of the model.

The manuscript is definitely too long and looks more like a report. The text should be shortened and the flow of text improved. It has a fair share of typos and omissions. The following is just a sample.

Line 26, Kili Bay is in Taiwan. Do you mean the Kiel Bay?

Fig 1 does not seem to have a caption.

Reviewer #2: Review of Pärn et al Effects of sea ice and wind speed on Phytoplankton spring bloom in Central and Southern Baltic Sea.

The paper is a model study that investigates the spring bloom in the Baltic Sea, and in particular focuses on the shifting dominance between diatoms and dinoflagellates. There has been a shift over the past decades from diatom dominance towards more dinoflagellates during this period. The conclusion drawn from the paper suggests diatoms dominate the spring bloom when there is thick ice cover, whereas dinoflagellates dominate when the ice cover is thin. They also argue that diatoms will dominate when the ice cover is completely removed something that might take place in a warmer future.

I am not a modeler and cannot go into the details behind the model, but I found the paper interesting and worthy of publication although I am not sure about the general conclusion and would like to see some revision in that respect.

Getting the model to work with the slower growing dinoflagellates can be difficult, and it seems they had to increase the growth rate above what is published under optimal conditions for dinoflagellates. Also, large parts of the central Baltic Sea is very often without ice and still dinoflagellates seem to dominate, see e.g. Fig 4 in Klais et al 2011. So the distribution of dinoflagellate dominance extends from typically ice covered to not ice covered.

What I think is something missing in the model is the fact that the spring bloom is driven by the inflow of freshwater creating the initial stratification rather than thermal stratification which requires longer time for the surface layer to warm up. I would suggest to play around with this in the model, or at the very least bring up the limitations in the model in the discussion as it clearly is not well able to capture the dinoflagellate dominance in the southern and central parts of the Baltic Sea that is typically ice free every winter.

Minor comments

L 75: Could add a line explaining that diatoms are non-motile and sink quicker whereas dinoflagellates are motile and can position themselves vertically.

L 79 Most of dinoflagellates sink in the form of cysts, otherwise vegitative cells tend to lyse before reaching the seafloor and still diatoms is probably the more quickly sinking group.

L 81: This is only in the case of the resting cysts that are not decomposed in the sediment

L84-97: The difference in growth rate is the same between dia and dinos in the Baltic Sea (Spilling and Markager 2008 - https://doi.org/10.1016/j.jmarsys.2006.10.012). What is likely a factor is timing of requirement (Kremp et al 2008) and stratification. What is different in the Baltic Sea from many other coastal regions is the massive freshwater outflow at spring and salinity stratification rather than thermal stratification playing an effect (Stipa 2002 & 2004) which is important for the start of the spring bloom.

L123. 0.7 d-1 is likely too high, 0.4 d-1 is more realistic

L124 ranging 0.6 to 1.4 d-1 depending on species

L313: In reality dinoflagellates are actually the dominating group at least in station 32.

L440-41: no they actually swim

L477-479: sounds like there was no spring bloom in the past

L483-486: There is ample evidence dinoflagellates dominate even under ice free winters so I do not buy this conclusion, a more interesting question is why the model gets it wrong.

Some new and relevant citations:

Hjerne, Olle, Susanna Hajdu, Ulf Larsson, Andrea Downing, and Monika Winder. "Climate driven changes in timing, composition and size of the Baltic Sea phytoplankton spring bloom." Frontiers in Marine Science 6 (2019): 482.

Lipsewers, Tobias, Riina Klais, Maria Teresa Camarena-Gómez, and Kristian Spilling. "Effects of different plankton communities and spring bloom phases on seston C: N: P: Si: chl a ratios in the Baltic Sea." Marine Ecology Progress Series 644 (2020): 15-31.

Camarena‐Gómez, María Teresa, Clara Ruiz‐González, Jonna Piiparinen, Tobias Lipsewers, Cristina Sobrino, Ramiro Logares, and Kristian Spilling. "Bacterioplankton dynamics driven by interannual and spatial variation in diatom and dinoflagellate spring bloom communities in the Baltic Sea." Limnology and Oceanography (2020).

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Effects of sea ice and wind speed on Phytoplankton spring bloom in Central and Southern Baltic Sea

PONE-D-20-34799R1

Dear Dr. Pärn,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Arga Chandrashekar Anil, Ph. D., D. Agr.,

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: N/A

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: I am happy with the response to the review and the changes done. There are still a few typos so please read carefully through it before the final version goes to print.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No