The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

Moore-Maley, Benjamin L.; Ianson, Debby; Allen, Susan E.

doi:https://doi.org/10.5194/bg-15-3743-2018

Articles | Volume 15, issue 12

https://doi.org/10.5194/bg-15-3743-2018

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

https://doi.org/10.5194/bg-15-3743-2018

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

Articles | Volume 15, issue 12

Research article

|

20 Jun 2018

Research article |

| 20 Jun 2018

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

Benjamin L. Moore-Maley, Debby Ianson, and Susan E. Allen

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Final revised paper (published on 20 Jun 2018)
Supplement to the final revised paper
Preprint (discussion started on 30 Aug 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'referees comment', Anonymous Referee #1, 10 Nov 2017
- AC1: 'Response to anonymous reviewer 1.', Ben Moore-Maley, 24 Dec 2017
RC2: 'Effects of river endmember variatins on carbonate parameters during estuarine mixing', Anonymous Referee #2, 30 Nov 2017
- AC2: 'Response to anonymous reviewer 2.', Ben Moore-Maley, 24 Dec 2017
EC1: 'Editor Comment', Jack Middelburg, 01 Dec 2017
- AC3: 'Response to the editor', Ben Moore-Maley, 24 Dec 2017

Peer-review completion

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

ED: Reconsider after major revisions (04 Jan 2018) by Jack Middelburg

AR by Ben Moore-Maley on behalf of the Authors (10 Feb 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (13 Feb 2018) by Jack Middelburg

RR by Anonymous Referee #2 (29 Apr 2018)

Suggestions for revision or reasons for rejection

This paper has examined the sensitivity of Omega(arag) and pH in the Strait of Georgia to Fraser River carbonate chemistry by summarizing the results of a coupled biogeochemical model across 12 hydrological cycles and 18 freshwater TA and DIC:TA combinations. The simulations and discussion are of interest to the current research. I agree that the revised manuscript is much improved. I generally support the publication after additional improvement of writing. Below are my two main concerns.
1. While I can understand the abstract and summary very well, I feel some of the presentations on the Results and Discussion are still quite hard to follow. I want to warn the authors (and the editor) that other readers may have similar issues in assimilating the ideas from this paper.
2. As stated in the paper (e.g., abstract and summary), the Fraser River pH and Omega are strongly controlled by biological production during the production seasons and, even during the maximum river flow summertime, estuarine sensitivity to river chemistry is greatly reduced. Then, I am not totally convinced that such a lengthy discussion on this aspect is fully justified. Maybe some additional justifications are needed on that the sensitivity to river chemistry is still an important consideration.
Below are some minor issues I spotted while reading:

p.1, Line 9, “while the carbonate portion of the (higher) DIC causes an increase in estuarine A..” is confusion. Simply say “while the resulting higher carbonate ion concentration causes an increase in estuarine A…” is clear and sufficient.
p.2, line 15, the citation Cai et al. 1998 is probably wrong and the correct or more appropriate one would be Cai et al. 2008.
Cai, W.-J., Guo, X., Chen, C.T. A., Dai, M., Zhang, L., Zhai, W., Lohrenz, S.E., Yin, K., Harrison, P. J. and Wang, Y. 2008. A comparative overview of weathering intensity and HCO3- flux of the world’s major rivers with emphasis on the Changjiang, Huanghe, Zhujiang (Pearl) and Mississippi Rivers. Continental Shelf Research 28:1538-1549, doi:10.1016/j.csr.2007.10.014.

Bottom of p.6, eqn 1. I assume the flow dependent river endmember TA can be smaller and greater than the TA0. But just looking at eqn 1, that is not so clear to me. I guess it is in the dQ/dt term, which can be negative. please add a short note (I now see that a reference to fig. 2c is all it needs).

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ED: Publish subject to minor revisions (review by editor) (29 Apr 2018) by Jack Middelburg

AR by Ben Moore-Maley on behalf of the Authors (13 May 2018) Author's response Manuscript

ED: Publish subject to technical corrections (20 May 2018) by Jack Middelburg

AR by Ben Moore-Maley on behalf of the Authors (01 Jun 2018) Manuscript

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Short summary

Estuaries are vulnerable to ocean acidification, but present-day estuarine pH and aragonite saturation state variability are larger than in the open ocean. Using a numerical model of a large estuary and data from its primary river, we find that changes in river alkalinity relative to river carbon may determine a small but significant portion of this variability, while the majority is controlled by photosynthesis/respiration. Future watershed changes may shift the river alkalinity–carbon balance.