Dear dr Gourdin,

Thank you for your detailed author replies and revised version. Your revised version will be sent out for re-evaluation by both original referees, since both indicated they would like to see the revised version.
When going through your author replies concerning the absence/presence of carbonates, I have an addition concern related to the sampling approach, whereby samples were not filtered but instead evaporated. It would be worth considering if the dissolved inorganic carbon present in the water samples would not lead to carbonate precipitation, and if so, it would need to be argued quantitatively why this would not lead to significant shifts in d13C. Are there data on alkalinity and/or dissolved inorganic carbon concentrations for this system ? In particular under low TSS conditions (and thus, low POC levels) this contribution may be quantitatively substantial.

Best regards
Steven Bouillon

Dear Elian,

One of the original reviewers has now evaluated your revised version and author replies, and in line with my own reading, the revised version represents a strong improvement in which the referee comments and suggestions have overall been well incorporated. I'm therefore pleased to accept your manuscript for publication in Biogeosciences, but as suggested by Ref#1, please take some time to go through the last version for some minor textual corrections, and cross-check the references between text and reference list(e.g. Clark et al. 2013 is not in reference list).
Best regards
Steven Bouillon