Diazotrophic <i>Trichodesmium</i> impact on UV–Vis radiance and pigment composition in the western tropical South Pacific

Dupouy, Cécile; Frouin, Robert; Tedetti, Marc; Maillard, Morgane; Rodier, Martine; Lombard, Fabien; Guidi, Lionel; Picheral, Marc; Neveux, Jacques; Duhamel, Solange; Charrière, Bruno; Sempéré, Richard

doi:https://doi.org/10.5194/bg-15-5249-2018

Articles | Volume 15, issue 16

https://doi.org/10.5194/bg-15-5249-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Interactions between planktonic organisms and biogeochemical...

https://doi.org/10.5194/bg-15-5249-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 16

Research article

|

30 Aug 2018

Research article |

| 30 Aug 2018

Diazotrophic Trichodesmium impact on UV–Vis radiance and pigment composition in the western tropical South Pacific

Cécile Dupouy, Robert Frouin, Marc Tedetti, Morgane Maillard, Martine Rodier, Fabien Lombard, Lionel Guidi, Marc Picheral, Jacques Neveux, Solange Duhamel, Bruno Charrière, and Richard Sempéré

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Final revised paper (published on 30 Aug 2018)
Preprint (discussion started on 15 Jan 2018)

Interactive discussion

Status: closed

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

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RC1: 'Comments on bg-2017-570-manuscript-version2 (Diazotrophic Trichodesmium influence on ocean color and pigment composition in the South West tropical Pacific)', Anonymous Referee #1, 15 Feb 2018
- AC2: 'Responses to Reviewer#1', Cécile DUPOUY, 28 Apr 2018
RC2: 'Review of bg-2017-570', Anonymous Referee #2, 12 Mar 2018
- AC1: 'Responses to Reviewer#2', Cécile DUPOUY, 28 Apr 2018

Peer-review completion

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

ED: Reconsider after major revisions (07 May 2018) by Thierry Moutin

AR by Cécile DUPOUY on behalf of the Authors (25 Jun 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (26 Jun 2018) by Thierry Moutin

RR by Anonymous Referee #2 (10 Jul 2018)

Suggestions for revision or reasons for rejection

Journal: Biogeosciences Discuss.
Title: Diazotrophic Trichodesmium impact on UV-Vis radiance and pigment composition in the South West tropical Pacific

Author(s): Dupouy et al.
MS No.: 2017-570
MS Type: Research Article

\noindent{\bf General comments}\\
The authors have satisfactorily addressed my comments from the initial review, and I thank them for making this effort. In my opinion the revised manuscript is much improved and better conveys the results of their study.

I have only one minor comment and a few technical corrections on the revised manuscript, all easily addressed, which the authors may wish to consider for the final version.

\noindent{\bf Specific comments}\\
Line 407: I would say the fits of nLw vs. Chla at 305 and 325 nm from OUTPACE are different from BIOSOPE, but are they necessarily “better”? Can you provide a reason why the relationships are different in these bands but not other UV bands (e.g., 340, 380 nm)? Is it related to the presence of Trichodesmium, or some other constituent covarying with Chl?

\noindent{\bf Technical corrections}\\
Line 282: Here the surface TChla “accumulation” for station LDB is stated as 1 mg m^{-3}, yet in Table 1 the surface value is given as 0.433, the Fig. 2 legend states it is 0.42, and Line 299 again states it is 0.433. I suspect that by “accumulation” you are referring to some depth-integrated value, if that is the case please make it clear. These small inconsistencies confused this reader at least.

Line 329: Unless I am mistaken, Fig. 4a is not derived from HPLC pigments, as suggested by this sentence, but from the UVP measurements.

Line 417: I realize it’s rounding approximation, but the sum of the two PCs as written (81 + 13) is 94%, not 93%. The same comment applies to Line 429 (89 + 7 = 96%, not 95%).

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ED: Publish subject to technical corrections (10 Jul 2018) by Thierry Moutin

AR by Cécile DUPOUY on behalf of the Authors (19 Jul 2018) Author's response Manuscript

Short summary

The marine diazotrophic Cyanobacterium Trichodesmium from the Underwater Vision Profiler 5 is concentrated in the first 50 m in the western tropical Pacific Ocean (18–22° S, 160° E–160° W). Its contribution to Tchl a and zeaxanthin is 60 % in the Melanesian archipelago and 30 % in the Fijian archipelago. Its impact on UV–VIS radiance is a peculiar signal in the green and yellow and possibly associated with backscattering or phycoerythrin fluorescence from Trichodesmium.