Simultaneous shifts in elemental stoichiometry and fatty acids of <i>Emiliania huxleyi</i> in response to environmental changes

Bi, Rong; Ismar, Stefanie M. H.; Sommer, Ulrich; Zhao, Meixun

doi:https://doi.org/10.5194/bg-15-1029-2018

Articles | Volume 15, issue 4

https://doi.org/10.5194/bg-15-1029-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-15-1029-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 4

Research article

|

20 Feb 2018

Research article |

| 20 Feb 2018

Simultaneous shifts in elemental stoichiometry and fatty acids of Emiliania huxleyi in response to environmental changes

Rong Bi, Stefanie M. H. Ismar, Ulrich Sommer, and Meixun Zhao

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Final revised paper (published on 20 Feb 2018)
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Preprint (discussion started on 19 May 2017)
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Interactive discussion

Status: closed

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

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RC1: 'Simultaneous shifts in stoichiometric and fatty acid composition of Emiliania huxleyi in response to environmental changes', Anonymous Referee #1, 07 Jun 2017
RC2: 'Reviewer comments', Anonymous Referee #2, 07 Aug 2017
AC1: 'Final author comments', Rong Bi, 30 Aug 2017

Peer-review completion

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

ED: Reconsider after major revisions (30 Aug 2017) by S. Wajih A. Naqvi

AR by Rong Bi on behalf of the Authors (07 Oct 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (09 Oct 2017) by S. Wajih A. Naqvi

RR by Anonymous Referee #2 (30 Oct 2017)

Suggestions for revision or reasons for rejection

General comments:

The authors did a good job revising the manuscript, as the current version is more concise and improved a lot. Furthermore, I think the presented results are extremely interesting and can further advance the field of climate change effects on stoichiometry and fatty acids composition. However, I still have some comments on the manuscript in its current form:

Table 2 at the moment includes both significant and non-significant changes, which can confuse the reader. I would therefore opt to either clearly indicate which changes are significant or alternatively only show significant changes in this table. This also relates to parts of the discussion (lines 449-465) where you discuss changes in C:P ratio with elevated temperature, which are actually non-significant in your analysis (table 1).

I’m currently missing some lines in the results addressing the SFA responses to interactions between nutrient and CO2 treatment.

I don’t fully understand how to interpret Figure 5, which I think came about after my previous comment on the relationship between changes in stoichiometry and fatty acid composition. My earlier comment was not directed towards the ratios between cellular contents and PUFAs, but towards a correlation between stoichiometric changes and fatty acid changes related to table 2. In other words, can changes in for instance PON (or POP, POC or PIC) content be related to changes in PUFAs (e.g. if PON goes up, does PUFAs also go up)? Thus, I would leave this figure out and discuss these putative correlations in the discussion.

Line 298 (and discussion lines 399-403): Why would you discuss an interaction effect that is not supported by the statistical analysis in table 1? I would omit this from the text.

Line 502: I would not state that non-significant changes in POC content attributed to altered PIC:POC ratios.

Specific comments:
Line 43: ‘compared to’ instead of ‘compared with’
Line 117: ‘.’ Instead of ‘; ‘
Line 133 (and throughout the manuscript): typesetting of °C
Line 139: As the IPCC is a model prediction, I would add some nuance to this sentence.
Line 184-185: It is not clear to me what you mean with the gross growth rate. How does it only result from the process of reproduction? In these systems you would still have cell death as well right?
Line 312: ‘values’ instead of ‘trend’ as it otherwise suggests non-significance while it is supported by your analysis
Line 351: ‘N:P supply ratio’ instead of ‘nutrient deficiency’ as in your experimental set-up one nutrient becomes deficient in replacement of the other over the experimental gradient. Related to that comment, in several parts of the discussion (lines 370 and 415) you write nutrient deficiency which I think should be phosphorus deficiency (as nitrogen is replete in these cases).
Line 408: two times ‘conceptual’ in one sentence, consider revising.
Line 479: add ‘and’
Line 522: The example (txCO2) is inconsistent with the factors in the previous sentence (txnutrient)
Line 548: ‘MUFAs’ instead of ‘MUAFs’
Line 588: ‘while’ instead of ‘with’
Line 616: rephrase as no effect of N:P supply ratios on C:P, nor on PON and POP were observed.

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ED: Reconsider after major revisions (02 Nov 2017) by S. Wajih A. Naqvi

AR by Rong Bi on behalf of the Authors (16 Nov 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (17 Nov 2017) by S. Wajih A. Naqvi

RR by Anonymous Referee #2 (15 Dec 2017)

ED: Publish subject to minor revisions (review by editor) (23 Dec 2017) by S. Wajih A. Naqvi

AR by Rong Bi on behalf of the Authors (03 Jan 2018) Author's response Manuscript

ED: Publish as is (15 Jan 2018) by S. Wajih A. Naqvi

AR by Rong Bi on behalf of the Authors (15 Jan 2018) Manuscript

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Short summary

We observed that N : P supply ratios had the strongest effect on C : N : P stoichiometry, while temperature and pCO₂ played more influential roles on PIC : POC and polyunsaturated fatty acid proportions in Emiliania huxleyi. Synergistic interactions indicated the enhanced effect of warming under nutrient deficiency and high pCO₂. Simultaneous changes of elements and fatty acids should be considered when predicting future roles of E. huxleyi in biogeochemical cycles and ecological functions.