Dear Dr Martignier,

After consultation with (some of) the reviewer(s), I would like to invite you to upload a new version of your manuscript. I indicated 'major revisions', but I expect your updated manuscript will not need very many more adjustments before acceptance in Biogeosciences.

Sincerely,

Lennart

Dear Dr Martignier and co-authors,

I think your manuscript is ready to be accepted for publication. There is one final comment from one of the reviewers, which I copied below. Looking forward to see this incorporated and accept your manuscript for publication in Biogeosciences.

Sincerely,

Lennart

I very much appreciate the considerable effort made by the authors in answering all of my comments. I think the manuscript is now ready for publication. The only modification I am suggesting is concerning comment 20, i.e. the stabilization of ACC by inorganic or organic additives. The paragraph the authors proposed to add is well written. However, one sentence is not totally correct (underlined part): “Magnesium is known to play a key role in the stabilization of ACC by introducing a distortion in the host mineral structure (Politi et al., 2010).” Indeed Mg stabilized ACC but the reason is not the one stated here, but rather the fact that Mg binds to water and decreases ion mobility. I would suggest to remove the underlined part. I additionally noted that in the legend Figure 1, (j) is tetrath_ac is still missing.