Dear authors,

thank you for your replies to the reviewers comments. I would like to invite you to submit a revised version of your manuscript.

Sincerely,
Kai Schulz

PS. Bringing the pH of MQ water up by de-gassing of CO2 will not change the saturation state significantly, as MQ does not contain calcium ions. However, the short exposure time of seconds and the fact that you find sharp edges around individual coccoliths on SEM images, is convincing.

Dear authors,

thank you for submitting a revised version of your manuscript, addressing all of the issues raised by the reviewers. Upon minor technical corrections (see below) I am happy to accept it for publication in Biogeosciences.

Sincerely,
Kai Schulz


1) Looking at TA climatologies, it seems to me that the Southern Ocean does not have low alkalinities per se - although lower than some subtropical regions. Maybe check again and/or re-formulate.

2) Line 486: Do you mean POC/BSi ratio?

3) Please update the reference Gafar et al. (2017) to

Gafar, N. A., B. D. Eyre, and K. G. Schulz (2017), A conceptual model for projecting coccolithophorid growth, calcification and photosynthetic carbon fixation rates in response to global ocean change (carbonate chemistry speciation, temperature and light) based on Gephyrocapsa oceanica.", Frontiers in Marine Science, in review.