Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and
global biogeochemical cycles

Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín; Alvain, Séverine; Aumont, Olivier; Bopp, Laurent; Chollet, Sophie; Enright, Clare; Franklin, Daniel J.; Geider, Richard J.; Harrison, Sandy P.; Hirst, Andrew G.; Larsen, Stuart; Legendre, Louis; Platt, Trevor; Prentice, I. Colin; Rivkin, Richard B.; Sailley, Sévrine; Sathyendranath, Shubha; Stephens, Nick; Vogt, Meike; Vallina, Sergio M.

doi:https://doi.org/10.5194/bg-13-4111-2016

Articles | Volume 13, issue 14

https://doi.org/10.5194/bg-13-4111-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-13-4111-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 14

Research article

|

18 Jul 2016

Research article |

| 18 Jul 2016

Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

Corinne Le Quéré, Erik T. Buitenhuis, Róisín Moriarty, Séverine Alvain, Olivier Aumont, Laurent Bopp, Sophie Chollet, Clare Enright, Daniel J. Franklin, Richard J. Geider, Sandy P. Harrison, Andrew G. Hirst, Stuart Larsen, Louis Legendre, Trevor Platt, I. Colin Prentice, Richard B. Rivkin, Sévrine Sailley, Shubha Sathyendranath, Nick Stephens, Meike Vogt, and Sergio M. Vallina

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Final revised paper (published on 18 Jul 2016)
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Preprint (discussion started on 30 Jul 2015)
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Interactive discussion

Status: closed

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

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RC C7351: 'Review of manuscript', Victor Smetacek, 03 Nov 2015
RC C7542: 'Review', Anonymous Referee #2, 10 Nov 2015
AC C9507: 'Reply to reviewer (V. Smetacek)', Corinne Le Quere, 31 Jan 2016
AC C9508: 'Reply to reviewer 2', Corinne Le Quere, 31 Jan 2016

Peer-review completion

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

ED: Reconsider after major revisions (08 Feb 2016) by Gerhard Herndl

AR by Corinne Le Quere on behalf of the Authors (21 Mar 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (02 Apr 2016) by Gerhard Herndl

RR by Anonymous Referee #2 (18 May 2016)

Suggestions for revision or reasons for rejection

In their revised version the authors have largely responded to the questions and remarks of the referees and revised the manuscript additional information/figures accordingly. However, there is still little justification given for the choice of weighing factors used to describe the preferences of the different zooplankton functional types in the model. I generally agree that in the absence of sufficient data, arbitrary predator-prey ratios could be used to weigh the preferences. However, they should at least match the current understanding of grazing losses by various PFTs. In case of the well-studied Phaeocystis spp, for instance, this is not the case as the weighing contradicts the size-dependent relationship recently reviewed by Nejstggard et al. (2007). It is therefore difficult to accept that the colonial form is preyed on with the same preference like picophytoplankton or with a similar weighing to larger zooplankton. Similar discrepancies exists in other PFTs and might be one factor for stronger coupling between phytoplankton and zooplankton biomass as suggested in the conclusion. While this procedure might be acceptable in the present manuscript as it is based on a published source, the authors could generally be more critical with their results and stronger highlight the lacking knowledge (e.g., on trophic relationships, not represented PFTs) to improve the understanding of the role of macrozooplankton in controlling the phytoplankton stocks because this might be critical for the improvement of future models. Apart from this criticism, I find the manuscript well in the focus of BG, stimulating and acceptable for publication.

Hirst & Kiorboe (2002) is missing in the references.

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ED: Publish subject to technical corrections (11 Jun 2016) by Gerhard Herndl

AR by Corinne Le Quere on behalf of the Authors (14 Jun 2016) Author's response Manuscript

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Short summary

We present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types, and use the model to assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean. Our results suggest that observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton growth.