Dear Authors,
three reviews have been received for your ms. Rev#1 and rev#2 address largely minor scientific and technical issues, whereas rev#3 raised serious concern about the scientific quality of the presented results. All reviewers pointed out that the discussion about the origin of the DOM in the SML (terrestrial vs upelled material) needs clarification.

On the basis of the three reviews I, therefore, would like to invite you to re-submit the ms after major revisons. In the revised ms the concerns of all reviewers should be addressed carefully and special attention should be given to address the points raised by rev#3.

Dear authors,
thank your for re-submitting a revised version of your ms. I have sent out the revised version for review. The comments of the reviewer are listed below.
Please consider all comments carefully in a revised version the ms.

Best regards
Hermann Bange

Suggestions for revision from the reviewer:
I greatly appreciate the authors' thorough revision of their initial submission. These revisions addressed most of the referees' comments and improved the manuscript significantly.

I particularly appreciate the information added on PARAFAC modelling of fluorescence EEMs and the verification of the final 5 component model. In addition, the discussion of possible (C)DOM origins and cycling is now much clearer than before.

This leaves me with only some very minor comments:

1. The abstract still does not contain cruise dates, nor does it carry any quantitative information. I did request this in my initial comments, and I still believe that cruise / sampling dates should always be reported, and that publications reporting field observations should carry at least some quantitative info, not simply some qualitative description of the findings.

2. N2O interactions with 'phenolic groups' (lines 1449 ff in authors' response): I still believe that the statement on possible implications of N2O-FDOM interactions (F1, F4 = proteinaceous fluorescence) for N2O cycling is rather too speculative, given that it is based on experiments in a neon matrix carried out at or below 8 K using millimolar levels of both aromatic monomeres and N2O (Cao et al. 2014). I appreciate the authors' opinion on speculative discussion. However, I recommend that they clarify the conditions of the experimental work used in Cao et al. (2014) (rather than simply state “non-comparable to our study area ”) if they want to retain this statement.
Additional minor comment: phenylalanine is an aromatic but not a phenolic amino acid. Please correct your wording.

Dear Colleagues,
I am pleased to let you know that the revised version of your ms is now acceptable for publication in Biogeosciences.

Best wishes
Hermann Bange