Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes

Fiskal, Annika; Deng, Longhui; Michel, Anja; Eickenbusch, Philip; Han, Xingguo; Lagostina, Lorenzo; Zhu, Rong; Sander, Michael; Schroth, Martin H.; Bernasconi, Stefano M.; Dubois, Nathalie; Lever, Mark A.

doi:https://doi.org/10.5194/bg-16-3725-2019

Articles | Volume 16, issue 19

https://doi.org/10.5194/bg-16-3725-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-16-3725-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 19

Research article

|

30 Sep 2019

Research article |

| 30 Sep 2019

Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes

Annika Fiskal, Longhui Deng, Anja Michel, Philip Eickenbusch, Xingguo Han, Lorenzo Lagostina, Rong Zhu, Michael Sander, Martin H. Schroth, Stefano M. Bernasconi, Nathalie Dubois, and Mark A. Lever

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Final revised paper (published on 30 Sep 2019)
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Preprint (discussion started on 27 Mar 2019)
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Interactive discussion

Status: closed

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

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RC1: 'Comments to the manuscript', Anonymous Referee #1, 18 Apr 2019
- AC1: 'Answer to RC1 BGD AFetal', Annika Fiskal, 18 Jun 2019
RC2: 'Reviewer comment #2', Anonymous Referee #2, 04 Jun 2019
- AC2: 'Answer to RC2 BGD AFetal', Annika Fiskal, 18 Jun 2019

Peer-review completion

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

ED: Reconsider after major revisions (01 Jul 2019) by Gwenaël Abril

AR by Annika Fiskal on behalf of the Authors (03 Jul 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Jul 2019) by Gwenaël Abril

RR by Anonymous Referee #2 (28 Aug 2019)

Suggestions for revision or reasons for rejection

Most of my comments for the previous version were addressed. The authors have improved the Method section substantially, particularly the model calculations and definition of terms. This makes the paper easier to understand. More explanation on comparison of nitrate reduction rates is now included. My major concern is the conclusion about “redox zonation”. However, I consider this an easy fix by clarifying the terms, rephrasing the conclusions and some parts of discussion (see specific comments below)
1. Page 1, line 25: “No major effect of trophic state on the relative distributions of these reactions” – I disagree (see comment # 5).
2. Page 1, line 30-32: This is interesting the explanations on reduced P concentration is not clear (see comment # 6)
3. Page 3, line 14-15: What’s the difference between “OC loading” and “OC sedimentation rates”? What exactly is OC loading? From external?
4. Page 3, line 22-23: “Furthermore, links between historically documented human activities in lakes and lake watersheds, eutrophication in lake water columns, which would inform on links between OC burial and mineralization processes in lake sediments.” – There is a grammatical problem (incomplete sentence). Also, it’s not obvious why “these links” would inform “those links”.
5. Page 17: line 7-10: “The eutrophication-related changes in respiration rates are, however, not reflected in the vertical zonation of microbial respiration pathways with respect to each other ” – I still don’t understand what the authors mean by this. Do you mean the zones are not clearly separated? Please state that specifically.
“the depth intervals of denitrification, Mn reduction, Fe reduction…. Show strong overlaps, independent of lake trophic state” – It’s not clear why there should be a link between the trophic state and “zonation”. What do you expect the effects of trophic state would be? Would you expect they not overlapping when TOC sedimentation is high? Why? More clarification is needed. Otherwise, I suggest rephrasing the sentence, perhaps using “regardless of their trophic state”. “Independent” suggests not having any effect, but I would argue that eutrophication would shift the locations of each zone. However, by looking at porewater profiles now, one would not know if the dynamics in primary production (and TOC sedimentation) shift the reaction zones. This is because dissolved species move (diffuse) much faster than sediment burial. The porewater profiles you are seeing now represent a snapshot of what’s going on right now, although the solid sediments is a mixture of historical and fresh sediments.
6. Page 19, line 10-14: “Such remobilization of P is not necessarily evident based on total P concentrations as most remobilized P is present in the highly bioavailable inorganic form” – but total P includes bioavailable inorganic P (the P released from sediments) and P from wastewater. Changes in sediment released P and its products (e.g., after being taken up as biomass P) would be reflected in the dynamics of total P.
7. Page 21, line 31 “Trophic state does not affect the zonation of microbial respiration reactions” – this conclusion is misleading (see comments above). I would rephrase it to: We observe less clear zonation of microbial redox reactions in sediments of lakes, regardless of their trophic states. I suggest not using the word “independent”.

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ED: Publish subject to minor revisions (review by editor) (29 Aug 2019) by Gwenaël Abril

AR by Annika Fiskal on behalf of the Authors (02 Sep 2019) Author's response Manuscript

ED: Publish as is (04 Sep 2019) by Gwenaël Abril

AR by Annika Fiskal on behalf of the Authors (05 Sep 2019) Author's response Manuscript

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