Methane distribution and oxidation around the Lena Delta in summer 2013

Bussmann, Ingeborg; Hackbusch, Steffen; Schaal, Patrick; Wichels, Antje

doi:https://doi.org/10.5194/bg-14-4985-2017

Articles | Volume 14, issue 21

https://doi.org/10.5194/bg-14-4985-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-14-4985-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 14, issue 21

Research article

|

08 Nov 2017

Research article |

| 08 Nov 2017

Methane distribution and oxidation around the Lena Delta in summer 2013

Ingeborg Bussmann, Steffen Hackbusch, Patrick Schaal, and Antje Wichels

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Final revised paper (published on 08 Nov 2017)
Supplement to the final revised paper
Preprint (discussion started on 08 Feb 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Referee Comment to Bussmann et al.', Anonymous Referee #1, 20 Mar 2017
- AC1: 'Response to Reviewer 1', Ingeborg Bussmann, 06 Jun 2017
RC2: 'Review Bussmann et al.', Anonymous Referee #2, 04 Apr 2017
- AC2: 'Response to Reviewer 2', Ingeborg Bussmann, 06 Jun 2017
RC3: 'review', Anonymous Referee #3, 26 Apr 2017
- AC3: 'Response to Reviewer 3', Ingeborg Bussmann, 06 Jun 2017

Peer-review completion

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

ED: Reconsider after major revisions (13 Jun 2017) by Gwenaël Abril

AR by Ingeborg Bussmann on behalf of the Authors (26 Jun 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Jul 2017) by Gwenaël Abril

RR by Anonymous Referee #3 (04 Jul 2017)

Suggestions for revision or reasons for rejection

L8 : « biggest” in terms of what ? Discharge ? Drainage area ?

Please define the abbreviations (qPCR, MISA, etc…) in the abstract. The abstract should be understood on its own, which requires that abbreviations are defined. Refer to instructions “The abstract should be intelligible to the general reader without reference to the text”, which is obviously not the case if the abstract is full of abbreviations. Since there is no size limit for abstracts in BG it should be not a problem to define all of the abbreviations.

L64: “MOBs” abbreviation is not defined, as it should the first time an abbreviation is used. Same applies to DOC, TDN, etc… The authors should take the time to polish the presentation of their work. It’s not the reviewer’s job to check this, especially at the second round of review.

L74: Here, explain how the present paper adds to the previous papers by the authors in the area.

L97: Specify what was the delay between the sampling and the analysis of CH4 in the home laboratory ? How were samples stored between sampling and analysis in the home lab: room temperature ? Did the authors check if poisoning with H2SO4 is efficient to stop biological activity and for how much time ? While I can imagine that acidification can preserve a sample for a few days, I not sure this is adequate for storage for months.

L101: specify the concentration of the NaOH solution.

L185: it’s Liss not Lisa

L 195: the relationship was not “developed for coastal seas”, it was derived from an experiment in a continental shelf. In fact the Nightingale relationship converges with relationships derived in the Southern Ocean (Ho et al. 2006).

L 235: “very high” is not adequate to describe CH4 concentrations since they vary by several orders of magnitude accross aquatic systems. 400 nmol/L might be "very high" for the Laptev Sea but will be very low for a tropical reservoir. Refer to actual numbers.

L 236: use an uniform unit throughout the text, a not a mix of µM, nM, nmol/L.

L 321: Did the vertical profiles of T and S show a mixing in response to “wind increase” ?

L 327, 363: “Unfortunately” is a subjective evaluation. Scientific writing should neutral and objective.

L 333: Oxygen in surface waters of rivers/estuaries can also be lowered by sediment organic matter degradation, since sediment respiration is usually equivalent to water column respiration in estuaries (Gazeau et al. 2004). So the correlation of CH4 and O2 does not necessarily imply that CH4 is produced in the water column due to a process that consumes O2 in the water column.

L336: Is there evidence that DMSP occurs in the Lena river/estuaries ? The study of Florez-Leiva et al. 2013 shows that the increase of CH4 in response to a spike in DMS was 2 nmol/L/d. Could this production term sufficient to account for the CH4 concentrations ?

L338-345: The CH4 concentrations in the Arctic estuaries (Lena, Ob and Yenisei) are much lower than those in temperate and tropical estuaries. This is an important information from this paper that should be mentioned and discussed. This probably results from the low temperatures and possibly lower organic matter concentrations in rivers (although this needs checking and discussing). This is relevant because temperature and possible organic matter concentrations in rivers can change in future in Arctic estuaries.

L 460: what is the reproducibility and accuracy of these measurements ? Is a 0.02 ppm difference significant, given differences in calibration gases, methods, etc… ?

L 466: This not the case in the Southern part of the North Sea where there is no thermal stratification, and fluxes are much higher than in the Northern part of the North Sea where stratification occurs (Borges et al. 2016).

L 520: diverse

Figure 2: remove PSU. Salinity is measured as a ratio of two conductivities (sample:standard), hence, unitless.

In the plot of Figure 2 replace nM by nmol L-1

In plot of Figure 3 replace nM by nmol L-1 and remove @ depth (m) = first

It could be useful to add the salinity plot (appendix figure) to figure 3, so that the CH4 concentration can be compared directly to the salinity (on the same figure).

In plots of Figure 5 add the units of MOX, and remove @ depth (m) = first

Appendix Table A1: specify if this was done only for the surface data or the full data-set (all depths). Specify what do the bold numbers mean.

References

Borges AV, W Champenois, N Gypens, B Delille, J Harlay (2016) Massive marine methane emissions from near-shore shallow coastal areas, Scientific Reports, 6:27908, doi:10.1038/srep27908

Gazeau et al. (2004) The European coastal zone: characterization and first assessment of ecosystem metabolism, Estuarine, Coastal and Shelf Science 60, 673-694

Ho, D. T., C. S. Law, M. J. Smith, P. Schlosser, M. Harvey, and P. Hill (2006), Measurements of airsea gas exchange at high wind speeds in the Southern Ocean: Implications for global parameterizations, Geophys. Res. Lett., 33, L16611, doi:10.1029/2006GL026817.

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ED: Reconsider after major revisions (19 Jul 2017) by Gwenaël Abril

Decision #3 on bg-2017-22 Methane distribution and oxidation around the Lena Delta in summer 2013

Dear Authors
I have received a second review of anonymous referee #3, and her/his evaluation of your revised MS was quite severe (see report). Note that this reviewer is an expert in the field. I made my own reading of your revised MS, including the modifications in the first version, and, indeed, I agree with referee#3 that your revisions were too superficial and not sufficient to satisfy all initial comments and reach the standards of a high quality journal like Biogeosciences. However, I believe this work must be published in BG, but only after a more careful and detailed revision. Critics concern: (1) presentation of the MS and formatting of figures and tables, and legends; (2) a too superficial discussion that does not adequately refer to the literature in order to put the presented results in a broader context; (3) some imprecise or inappropriate statements in the interpretation of the data. I would be pleased if you could revise your MS in order to satisfy the referee’s comments (and mine you will find below), and provide a detailed list of responses and a description of what as been changed in the MS.
Looking forward to reading this soon.
Best Regards
Gwenaël Abril, BG associate editor

Additional comments:
L204, what were the criteria used to delimit the two rectangular area. Appendix Fig. A1 is not necessary if the rectangles appear in Fig.1
L234 and throughout MS: “pale orange” is inappropriate as in fact it is “pale pink”, pale orange appearing between the yellow and the red in the colour grid. All the figures drawn with ocean data view are of poor quality (coloured points are very large and sometimes overlap) and the mentions “@depth(m)=last” are not understandable. Please improve also the legends.
Notation „riverine water“ is not conventional and unacceptable
I believe the information in the appendix tables 1 and 2 could appear together in a same table in the MS.
Why didn’t you test the correlation of CH4 concentration and MOX activity only after separating “river” “mixed” and “artic” and for the whole dataset?
Please also consider a presentation of CH4 concentrations versus salinity, as this is very classical and broadly used in the literature.
L317 The question raised by the referee of the general low CH4 concentrations in artic rivers and estuaries compared to other regions in the world is to my opinion fundamental and deserves a specific paragraph in the discussion: why are CH4 concentrations lower in artic estuaries?
L344 Reader is lost here. CH4 vs salinity plots would help the discussion.
L346 “we thus exclude the Lena River as methane source” strong statement not based on quantitative analysis. In theory you should be able to calculate the CH4 input from rivers using concentration and discharge
L347“One reason for this missing correlation, could be another source of freshwater, but with low methane concentrations.” Formulated that way, it appears as a speculative statement.
L355 “This additional aspect of the water budget in ice covered estuaries might explain the missing relation between salinity and methane concentration.” Ok, but please improve this part of the discussion (and associate figures) to make it clearer.
L456 “matter of debate between biogeochemists, ecologists, and PHYSICISTS” please revise English

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AR by Ingeborg Bussmann on behalf of the Authors (28 Aug 2017) Author's response Manuscript

ED: Publish subject to minor revisions (Editor review) (13 Sep 2017) by Gwenaël Abril

AR by Ingeborg Bussmann on behalf of the Authors (25 Sep 2017) Manuscript

ED: Publish as is (05 Oct 2017) by Gwenaël Abril

AR by Ingeborg Bussmann on behalf of the Authors (06 Oct 2017)

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