Nitrogen cycling in shallow low-oxygen coastal waters off Peru from nitrite  and nitrate nitrogen and oxygen isotopes

Hu, Happy; Bourbonnais, Annie; Larkum, Jennifer; Bange, Hermann W.; Altabet, Mark A.

doi:https://doi.org/10.5194/bg-13-1453-2016

Articles | Volume 13, issue 5

https://doi.org/10.5194/bg-13-1453-2016

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

Special issue:

Biogeochemical processes, tropospheric chemistry and interactions...

https://doi.org/10.5194/bg-13-1453-2016

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

Articles | Volume 13, issue 5

Research article

|

09 Mar 2016

Research article |

| 09 Mar 2016

Nitrogen cycling in shallow low-oxygen coastal waters off Peru from nitrite and nitrate nitrogen and oxygen isotopes

Happy Hu, Annie Bourbonnais, Jennifer Larkum, Hermann W. Bange, and Mark A. Altabet

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Final revised paper (published on 09 Mar 2016)
Preprint (discussion started on 18 May 2015)

Interactive discussion

Status: closed

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

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RC C3222: 'Comments on Biogeosciences Discussions paper by Hu et al.', Anonymous Referee #1, 30 Jun 2015
- AC C7210: 'Response to reviewer #1', Annie Bourbonnais, 30 Oct 2015
  - AC C7306: 'Corrected version 1', Annie Bourbonnais, 02 Nov 2015
RC C3245: 'Referee comment', Anonymous Referee #2, 01 Jul 2015
- AC C7218: 'Response to reviewer #2', Annie Bourbonnais, 30 Oct 2015
  - AC C7307: 'Corrected version 2', Annie Bourbonnais, 02 Nov 2015
RC C3427: 'Review', Anonymous Referee #3, 09 Jul 2015
- AC C7236: 'Response to reviewer #3', Annie Bourbonnais, 30 Oct 2015
  - AC C7308: 'Corrected version 3', Annie Bourbonnais, 02 Nov 2015

Peer-review completion

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

ED: Reconsider after major revisions (15 Nov 2015) by Carol Robinson

AR by Annie Bourbonnais on behalf of the Authors (16 Nov 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (19 Nov 2015) by Carol Robinson

RR by Anonymous Referee #3 (09 Dec 2015)

RR by Anonymous Referee #2 (23 Dec 2015)

Suggestions for revision or reasons for rejection

While the authors have done a fair job in considering the specific comments to the earlier version of their manuscript during revision, the general criticism still applies. The introduction has not changed significantly and still lacks clear structure/focus that would allow the non-expert reader to fully comprehend the broader context and aims of the current study. Unfortunately, this also applies to large parts of the results and discussion sections. Despite being well familiar with N cycling-related OMZ research, I often found it difficult to follow the authors’ train of thought or to extract the main implications of their results. An important result of the current study appears to be rapid nitrite turnover in the Peruvian coastal OMZ and a major role of nitrite oxidation in OMZ N cycling – which basically confirms recently published results from 15N-labelling experiments in the same area (Kalvelage et al. 2013). Confusingly, however, the authors estimate a turnover time for nitrite of at least 40 days - compared to 12 days based on the coastal OMZ nitrite production rates provided by Kalvelage et al. (2013) – which, to my knowledge, is sufficiently long for significant nitrite-water oxygen exchange. The implications of a lower fractionation factor for coastal water column N loss remain equally vague. I am missing a more in-depth discussion on how the global oceanic N (im-)balance changes under the assumption of highly suppressed isotope fraction in oxygen-depleted shelf areas. Further, I feel the authors’ interpretations are in part overly simplified or highly speculative. For example, the role of aerobic ammonium oxidation on nitrite δ15N values is not evaluated, despite this process being a significant source of nitrite at oxygen levels considered here. Also, there are still instances were relevant literature is either not considered/cited, cited incorrectly (not in a technical sense), or irrelevant literature is cited. Last but not least, the manuscript still suffers from a number of spelling and grammatical errors as well as often missing punctuation.

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ED: Publish subject to minor revisions (Editor review) (01 Jan 2016) by Carol Robinson

AR by Annie Bourbonnais on behalf of the Authors (14 Jan 2016) Manuscript

ED: Publish as is (07 Feb 2016) by Carol Robinson

AR by Annie Bourbonnais on behalf of the Authors (08 Feb 2016)