Technical Note: Cost-efficient approaches to measure carbon dioxide (CO<sub>2</sub>) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

Bastviken, D.; Sundgren, I.; Natchimuthu, S.; Reyier, H.; Gålfalk, M.

doi:https://doi.org/10.5194/bg-12-3849-2015

Articles | Volume 12, issue 12

https://doi.org/10.5194/bg-12-3849-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/bg-12-3849-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 12, issue 12

Technical note

|

24 Jun 2015

Technical note |

| 24 Jun 2015

Technical Note: Cost-efficient approaches to measure carbon dioxide (CO₂) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

D. Bastviken, I. Sundgren, S. Natchimuthu, H. Reyier, and M. Gålfalk

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Final revised paper (published on 24 Jun 2015)
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Preprint (discussion started on 04 Feb 2015)
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC C120: 'review', Anonymous Referee #1, 10 Feb 2015
RC C196: 'Review of "Technical Note: Cost-efficient approaches to measure carbon dioxide..."', Gwenaël Abril, 13 Feb 2015
RC C223: 'Review of Bastvikan et al, Technical Note: Cost-efficient approaches to measure carbon dioxide (CO2) fluxes', Anonymous Referee #3, 16 Feb 2015
AC C1875: 'Author Comment', David Bastviken, 05 May 2015

Peer-review completion

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

AR by David Bastviken on behalf of the Authors (16 May 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 May 2015) by Steven Bouillon

RR by Gwenaël Abril (19 May 2015)

Suggestions for revision or reasons for rejection

Second Review of the technical note by Bastviken et al submitted to BG

Authors provided satisfactory responses to most of my comments and those of the other reviewers and have intensively reworked their MS in consequence. This technical note is much clearer now and a significant contribution to the field. I have only few additional comments that mainly concern the choices for separating the information in the main MS and in the supplementary material. Basically no changes were maid in the figures between this version and the previous, and important additional figures are now shown in the supplement. I think that information such as the validation of water pCO2 values measured with the headspace chamber as well as limitation of the chamber technique due to long response time at low wind speed must appear in the main MS; There is enough room for that in this technical note. Supplementary material should be limited to practical and very technical aspects and not fundamental points.

Figure S12 gives a validation of the pCO2 chamber method (see comments by referee #1 and myself). It is important that it appears in the main MS (actually more important than Figure 2 which concerns simple gas samples).

Figure S13 shows the limitation of the method in lakes at low wind speed. It must also appear in the MS. I suggest the authors plot TET90 versus wind speed (rather than the Cole&Caraco k value), so less experienced readers will have a better idea on the limitation of the technique, which I think is crucial for future uses of the method. In the text in P11L30-P12L5 it should be clearly stated that at wind speed lower than a given value in m s-1, the response time of the chamber becomes longer than 10 hours, making difficult the interpretation of diel variations. Mention also that this might be critical, because low wind speed conditions are in many cases concomitant with strong diel variations, as they favour stratification and primary production in lakes. L4: Suggestion to readers to reduce the volume to area ratio (as in Fig S13) can be made. However, the inconvenient (and risk) of having the sensor to close to the water surface could be mentioned. Maybe the surface area of the chamber should be doubled rather than the height reduced by half.

Detail:
As stated in the MS, there are important problems with the calculation of pCO2 from pH and TA in acidic waters. So I suggest the authors prioritize comparison of their results with those in paper that report measured pCO2 in page11L26. In poorly buffered tropical waters in particular, the reference Abril et al. 2014 Nature (Measured pCO2) should be preferred from Marotta et al. 2010 (calculated pCO2).

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RR by Anonymous Referee #1 (21 May 2015)

Suggestions for revision or reasons for rejection

The authors have included most of my comments of the previous version of the ms. I really appreciate the level of detail and illustration given in the supplements to set-up the instrumentation. My major comment is that Figure S12 is in my opinion one of the most important of this paper and should be included in the main text rather than buried in the supplemental material. I recommend publication after the minor comments below are addressed.
P2 L11 : The main reason is that heating inside the chamber and pressure changes will bias the measurement if made over long periods (Belanger & Korzum 1991).
P2 L 32 - P3 L1 : this was initially postulated by Wanninkhof (1992)in lakes and extended to estuaries by Borges et al. (2004)
P3 L 17-19 : this is not a universal rule. In numerous tropical rivers, due to nutrient limitation and light limitation (turbidity or cdom), there’s little primary production, hence no detectable night-day variations of O2 or pCO2.
P9 L 20 : typo further
P 12 L 4: typo ratio
P 12 L 24 : could the protection housing of the sensor be adapted to hold silica gel to remove part of the moisture ? Rather than fully remove moisture, just remove enough moisture to avoid condensation ?
P13 L 18 : Please note that the equilibrator used by Abril et al. (2006) was in fact initially designed by Frankignoulle et al. (2001).

BELANGER, T. V. AND E. A. KORZUM. 1991. Critique of floatingdome technique for estimating reaeration rates. Journal of Environmental Engineering 117:144–150.
BORGES, A. V., B. DELILLE, L. S. SCHIETTECATTE, F. GAZEAU, G. ABRIL, AND M. FRANKIGNOULLE. 2004. Gas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames). Limnology and Oceanography49(5): 1630-1641
Frankignoulle M., Borges A. & R. Biondo (2001) A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments, Water Research, 35(5): 1344-1347
WANNINKHOF, R. 1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97: 7373–7382

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ED: Publish subject to minor revisions (Editor review) (22 May 2015) by Steven Bouillon

AR by David Bastviken on behalf of the Authors (31 May 2015) Author's response Manuscript

ED: Publish as is (01 Jun 2015) by Steven Bouillon

AR by David Bastviken on behalf of the Authors (01 Jun 2015)

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Short summary

Measurements of concentrations and fluxes of carbon dioxide (CO2) are fundamental to our understanding of carbon cycling and greenhouse gas balances. We are currently limited by the high cost of such measurements, making it difficult to properly investigate variability in space and time. This study presents measurement approaches that are very resource efficient in terms of equipment cost and measurement labor time, opening new opportunities to advance our knowledge of CO2 across landscapes.

Technical Note: Cost-efficient approaches to measure carbon dioxide (CO2) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

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Technical Note: Cost-efficient approaches to measure carbon dioxide (CO₂) fluxes and concentrations in terrestrial and aquatic environments using mini loggers