Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

Ji, Qixing; Frey, Claudia; Sun, Xin; Jackson, Melanie; Lee, Yea-Shine; Jayakumar, Amal; Cornwell, Jeffrey C.; Ward, Bess B.

doi:https://doi.org/10.5194/bg-15-6127-2018

Articles | Volume 15, issue 20

https://doi.org/10.5194/bg-15-6127-2018

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

https://doi.org/10.5194/bg-15-6127-2018

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

Articles | Volume 15, issue 20

Research article

|

18 Oct 2018

Research article |

| 18 Oct 2018

Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

Qixing Ji, Claudia Frey, Xin Sun, Melanie Jackson, Yea-Shine Lee, Amal Jayakumar, Jeffrey C. Cornwell, and Bess B. Ward

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Final revised paper (published on 18 Oct 2018)
Supplement to the final revised paper
Preprint (discussion started on 19 Mar 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Reviewers comments', Anonymous Referee #1, 09 Apr 2018
- AC1: 'Response to referee #1', Qixing Ji, 16 May 2018
RC2: 'Review of bg-2018-113', Anonymous Referee #2, 11 Apr 2018
- AC2: 'Response to Referee #2', Qixing Ji, 16 May 2018
RC3: 'Review of “Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay” by Ji et al.', Anonymous Referee #3, 13 Apr 2018
- AC3: 'Response to Referee #3', Qixing Ji, 16 May 2018
RC4: 'Review of Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay by Ji et al.', Anonymous Referee #4, 16 Apr 2018
- AC4: 'Response to Referee #4', Qixing Ji, 16 May 2018

Peer-review completion

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

ED: Reconsider after major revisions (24 May 2018) by Tina Treude

AR by Qixing Ji on behalf of the Authors (27 Jun 2018)

ED: Referee Nomination & Report Request started (11 Jul 2018) by Tina Treude

RR by Anonymous Referee #1 (19 Jul 2018)

RR by Anonymous Referee #4 (17 Sep 2018)

Suggestions for revision or reasons for rejection

The authors refute my major concerns about the paper. They have, however, made changes in response to the other reviewers’ comments that partly resolve these issues.

My major concern was that while the study only examines one pathway of N2O production, denitrification, and pathways associated to nitrification are ignored, the text in several places seems to deal N2O production in general, and not just one of the pathways (e.g., abstract l. 11, 12, 16, 18, 20; l. 273). The authors in their response argue that nitrification is not important during anoxia, which is obvious, but it is not obvious to the reader of the abstract that only (or mainly) anoxic experiments were conducted and that only denitrifying pathways were quantified. This must be made clear from the beginning, e.g., l. 11 should be changed to ”…were used to investigate the geochemical factors controlling N2O production FROM DENITRIFICATION in the Chesapeake Bay”, and so on for the other places mentioned above.

The authors also refute my comment about the detection for H2S by smell being ~10 µM. They do so, however, by referring to a naïve calculation, which has little to do with the context in which (I guess) the olfactory assay was conducted (on deck, in turbulent air, placing a nose above a bottle or stream of water, and not by equilibrating a large volume of water and inhaling the equilibrated air purely – if I’m wrong this needs to be specified). Thresholds in the low µM range can be found as a rule of thumb in the scientific literature and on the www – I leave the search to the authors. The point here is, however, that the conclusion that H2S was absent is not justified.

The first version contained a very rough calculation of nitrogen removal by denitrification based on the N2O production rates. In their response, the authors say that it will be removed. Now I find it in the conclusions (l. 300-9). This is confusing.

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ED: Publish subject to minor revisions (review by editor) (19 Sep 2018) by Tina Treude

AR by Qixing Ji on behalf of the Authors (23 Sep 2018) Author's response Manuscript

ED: Publish as is (04 Oct 2018) by Tina Treude

AR by Qixing Ji on behalf of the Authors (07 Oct 2018)

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Short summary

Nitrous oxide (N₂O) is a strong greenhouse gas and ozone-depletion agent. Intense N₂O effluxes had been observed from nutrient-rich estuaries with human impacts, such as the Chesapeake Bay. We report that increased nitrogen availability and low-oxygen conditions stimulate N₂O production. Thus, controlling the nutrient input to the bay will decrease nitrogen availability and alleviate eutrophication, leading to water column reoxygenation, and subsequently will mitigate N₂O emission.