Dear authors:
I have now carefully read through the reviewers' comments and your response. As you could see, particularly one reviewer is very critical about this study while the other one offers also a fair amount of suggestions to improve the manuscript. I have read the paper as well and find that the manuscript really needs substantial improvement. Particularly, I would encourage to base your model more on actually measured data on plankton. At least your model outcome should be mirrored against actual data. As the paper is now, it cannot be accepted for publication. I suggest that you revise the manuscript according to the reviewers' comments, include more measured data and only use relevant references. You were dealing with plankton but you are referring in your response to the reviewers to a paper dealing with Cs uptake in seaweed, which is definitely not plankton but benthic macroalgae. Along with the thoroughly revised manuscript, please provide also a point-by-point statement in which you highlight how you addressed the reviewers' comments in the revised version.
A very careful revision will be required to make this contribution acceptable for publication in Biogeosciences.
Best wishes, Gerhard Herndl

Dear authors:
I have now gone through the revised version and the reply to the reviewers' comments and found that the paper has now been substantially improved over the previous version. Almost all the reviewers' comments have been addressed in the revised paper. Consequently, I appreciate being able to inform you that your manuscript is now acceptable for publication in Biogeosciences.
There is one issue which needs to be resolved, however. Fig 4 needs some more explanations on the abbreviations used on the x-axis in the figure legend.
Fig. 5: the labeling of the x- and y-axes is not of print quality. There are smaller fonts behind the larger fonts. Please change the figures and make them ready for high quality printing. Please let me have the updated manuscript at your earliest convenience.
Best wishes, Gerhard Herndl