Dear Christiane,

thank you very much for handing in your replies to the reports of two reviewers that assessed your MS. These raised substantial concern to which I agree. In accordance with your replies, which seem sound, I would hereby like to invite you to prepare a revised version of your MS. Please pay particular attention to the inconsistencies with respect to sample treatment (thawing, incubation time etc), and add discussion on this matter so that it becomes clearer in how far the different treatments can be compared. Reviewer 2 provided important and helpful comments regarding this matter. I am aware that this is a field study and that sampling and replication is not always textbook-like. Nevertheless, make sure to clearly note and discuss when other inconsistencies occurred (eg differences in water masses) and in how far this limits/affects the significance of your MS. Water mass transport, eg, can severely change microbial community composition, abundance and activity (see eg Steinle et al., 2015); thus counting samples from differential water masses as replicates is a bit complicated.

Best wishes ,Helge

Dear Christiane,

thank you very much again for submitting your work to Biogeosciences. Both reviewers checked the MS and are happy with the modifications. There are only a few minor issues, which I kindly ask you to address:

P1
L8. change phrasing “before it has a chance” reads like active intention of methane to escape. Rather use, “before it can escape..”

L24, methane cycling is an erroneous term, which is unfortunately rather widely used in the literature. It implies that methane is transformed into an oxidation product which is then a substrate for MOg. Mostly that is not the case

L27. Use updated GWP from Etminan et al., 2016


P2

L8, there are much earlier discussion on methane dispersal than Gentz et al. 2014 (eg Damm’s HMMV work). Also, dispersal/dilution does not hinder CH4 efflux to the atmosphere.

L14, no ref given to the rather large seep area west off Svlabard

L17 this is up to 700%

L18, 160000% does as a number not make sense. Provide as factor

L22, several studies could show that the CH4 content is not the driving force behind activity of MOBs, see refs in James et al., 2016

L30ff, specify which MOBs can be targeted with pmoA

P4
L5. Rephrase to: temperature and salinity was recorded with…

L12, specify the type of in situ measurement

P9
L6. ‘higher isotope signatures’ does not make sense and I presume the value in line 7 is -54.4‰?

P13, see above, RE methane cycling. Rather methane dynamics

L13, add Leonte et al., 2017

L11 here and throughout the text. Don’t use x as a multiplication sign but rather ×

L19 sample size in statistics is usually abbreviated as ‘n’ not ‘N’

L25. …the microbial community possibly shifted towards…


P14
L18, the community size dependent methane oxidation (potential) has been verified in a number of studies (see works by Steinle et al. and refs cited in there), which should be cited here.


P16
L15ff, this is rather a summary, change the title of the subsection accordingly

Dear Christiane and co-authors,

thank you very much again for handing in your interesting research data on methane dynamics in the Arctic Ocean, which I would hereby like to accept for publication.

Best wishes, Helge