Shifts in dimethylated sulfur concentrations and microbiome composition in the red-tide causing dinoflagellate <i>Alexandrium minutum</i> during a simulated marine heatwave

Deschaseaux, Elisabeth; O'Brien, James; Siboni, Nachshon; Petrou, Katherina; Seymour, Justin R.

doi:https://doi.org/10.5194/bg-16-4377-2019

Articles | Volume 16, issue 22

https://doi.org/10.5194/bg-16-4377-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-16-4377-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 22

Research article

|

19 Nov 2019

Research article |

| 19 Nov 2019

Shifts in dimethylated sulfur concentrations and microbiome composition in the red-tide causing dinoflagellate Alexandrium minutum during a simulated marine heatwave

Elisabeth Deschaseaux, James O'Brien, Nachshon Siboni, Katherina Petrou, and Justin R. Seymour

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Final revised paper (published on 19 Nov 2019)
Preprint (discussion started on 17 Dec 2018)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of Deschaseaux et al.', Anonymous Referee #1, 05 Jan 2019
- AC1: 'Responses to Reviewer#1's comments', Elisabeth Deschaseaux, 28 Mar 2019
RC2: 'Review of Deschaseaux et al.', Anonymous Referee #2, 30 Jan 2019
- AC2: 'Responses to Reviewer#2's comments', Elisabeth Deschaseaux, 28 Mar 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (28 Apr 2019) by Gerhard Herndl

AR by Elisabeth Deschaseaux on behalf of the Authors (07 May 2019) Manuscript

ED: Referee Nomination & Report Request started (11 Jun 2019) by Gerhard Herndl

RR by Anonymous Referee #2 (26 Jul 2019)

RR by Anonymous Referee #3 (29 Jul 2019)

Suggestions for revision or reasons for rejection

I found this paper to be on a very interesting and important topic. The model organism used was wholly appropriate and I can understand why the authors carried out such a study. I must say that upon reading the comprehensive reviews of the two reviewers that their significant questions are valid. Particularly, I am not certain a 12C hike in temperature is environmentally relevant. However the authors take on this point and acknowledge this, but, I do feel that this could be stated more often and more prominently. As with the two reviewers, I agree that the temperature increases are having an effect on the growth and physiology of the dinoflagellate, but I am less than convinced on the effects of the temperature hikes on the cycling of organic sulfur compounds, which is one of the key aims of the study.

-I am afraid that I am not certain of effects of the 24C and 32C treatments on DMS and DMSO standing stocks, since in all cases effects are only seen in one time point (6h for 32C and 24h for 24C). Perhaps the authors are not likely to capture changes in DMSP/DMS/DMSO when only looking at studying standing stocks. This should be acknowledged in the manuscript. There is no noticeable change in DMSP standing stocks across the experiments until 96 h in the 33C experiment. Even then it seems to be equalling up at 120h. It might be more convincing if the authors had monitored changes in gene transcription for DMSP synthesis and lysis genes in A. minutum over the experiment. I do appreciate though that this is not easy and I am not asking for this to be done here.
-Also I do not understand why the 20C controls for the 24C and 32C experiments have such different profiles (e.g., Panel E and F of figure 4)? If I am understanding it correctly they should have very similar profiles? If I am understanding it correctly then some of the differences between the two 20c incubations are more dramatic than the differences reported here for the temp hikes, e.g., the DMSO production in panel’s e and f of Figure 4. I may have misinterpreted the experiments here. Apologies if I have. Can this be explained?
-Given the community change work was done at 120h when DMS and DMSO levels are similar to control samples, I feel it is most likely the temperature may be governing the change in microbial community and not the organic sulfur molecules they make? This should be stated in the manuscript.

Generally I feel that the authors of this manuscript have done a good job answering the reviewer’s points and making the manuscript more balanced. In conclusion, I feel that the manuscript is worthy of publication here if the above concerns are dealt with.

Extra points to raise:
-on line 43Indictae temperature itself as a potential driver for community change.
-L52 sulfur “compound”
-L75 A. minutum
-L86-94 can you give an example of a =12C hike in temp?
-L109 Specifically state 12C hike in temp and say if natural or not.
-L223 I may have a problem here with how you assay for DMSO. My problem is that if A. minutum produces DMSOP (Thume et al., Nature. 2018 Nov;563(7731):412-415.) then your assay for DMSO described here will also include DMSO derived from DMSOP that has been chemically cleaved.
L516 You have the wrong reference for dsyB. This should be Curson et al., Nat Microbiol. 2017 Feb 13;2:17009.
L560 Mimicking extreme coastal MHW’s is this true? Give example.
-It is perhaps worth mentioning more prominently that A. minutum is very robust in relation to temperature changes and that actually it is not likely to be affected by environmentally relevant temperature hikes. This almost definitely will be a strain specific phenomenon.

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ED: Publish subject to minor revisions (review by editor) (16 Aug 2019) by Katja Fennel

AR by Elisabeth Deschaseaux on behalf of the Authors (10 Sep 2019) Manuscript

ED: Publish as is (18 Sep 2019) by Katja Fennel

AR by Elisabeth Deschaseaux on behalf of the Authors (27 Sep 2019) Manuscript

Short summary

Here we report that abrupt increases in temperature–simulating marine heatwaves might have the potential to shape the physiological state and biogenic sulfur production in microalgae involved in harmful algal blooms. Changes in physiology and biochemistry seem to trigger a shift in the bacteria community associated with these microalgae. Since microalgae and associated bacteria play an important role in climate regulation, this could have serious consequences for our future ocean and climate.