Dear dr. Couturier,

Thank you for submitting your detailed replies to the comments of the reviewers. As you have seen, both reviewers are positive about your manuscript and support publication upon major revision. I agree with that assessment. When submitting your manuscript, please include a reply letter with details on where and how you modified the text in response to the comments. If possible, please also provide a track changes version of your manuscript, besides the clean copy. I look forward to seeing your revised manuscript.

best regards,
Caroline Slomp

Dear dr. Couturier,

Thank you for providing a revised manuscript. I have carefully assessed the changes made and kindly ask you to address the following points in a minor revision.

P1. Line 25: remove “of”
P3. Line 3: change “others” to “other”
P5. Line 17. Please rephrase this sentence to indicate that the date (“spring 2013”) refers to the water table levels and groundwater flow and not the data analysis of Chaillou et al. (2016)
P9. Change to “were lower”
P9. Line 24: Here “the potential biogeochemical mechanisms” is a better description and better reflects the uncertainties as mentioned by reviewer #1
P11. Line 5. Suggested change: “and may have induced a loss”
P11. Line 15: replace “weak” by “low”
P13. Line 15. Suggested change “in the STE is thought to be mineralization of”
P13. Line25: Change to “estimated in this way”
P14. Line 8. Change to “Estimates of nutrient export from the STE to the coastal ocean are more difficult”
P15. Line 10. Please rephrase lines 10-11 starting with “Even if” to make it proper English.
P15, Line 22 and Figure 7. Here, the production of NH4 is attributed to mineralisation of DON, whereas earlier, the degradation of terrestrial organic matter is invoked and Figure 7 clearly shows that DON degradation cannot explain the increase in NH4. I suggest a change to both the text and Figure 7 to make clear in both the conclusions and in graphical form that the TDN increase is attributed to a contribution of solid phase N.
P15. Line 22. Change “In consequences” to “As a consequence”.
P16. Line 2: Change to “supports”

best regards,
Caroline Slomp

Dear dr. Couturier,

Thank you for submitting your revised manuscript. I have gone through the changes made and kindly ask you to make the following changes in the current version:

(1) p5, line 21. Please make your text in the manuscript consistent with your reply letter, i.e. remove “in spring 2013” from the revised sentence.
(2) P15, lines 17-20. The revised text in the conclusions section is not very clear. You write “A part of NH4+ production could be attributed to mineralization of DON. However, the increase of TDN (i.e., DON and NH4+ concentration) in beach groundwater probably originated from terrestrial solid phase fraction.” For clarity, I would suggest to change this to: “A part of the NH4+ production could be attributed to mineralization of DON. The increase of TDN (i.e., the sum of DON and NH4+) in beach groundwater is likely the result of release of N from particulate organic matter of terrestrial origin.”
(3) Regarding Figure 7. I respect your choice to not include the release of TDN from organic matter in Figure 7. However, given that there clearly is a mass balance problem in the figure, I suggest you explain in the caption of the figure that additional TDN is added to the groundwater, e.g., by adding:” The increase in TDN along the groundwater flow path is attributed to release of N from particulate organic matter of terrestrial origin.”

I look forward to seeing a revised version of the manuscript.

best regards,
Caroline Slomp

Dear dr. Couturier,

Thank you for making the final changes. I look forward to seeing the final version of the manuscript published.

best regards,
Caroline Slomp