Dear Pei-Chuan,

the reviewers have raised some important concerns regarding your manuscript, which I fully support. Your replies and planed modification for the MS seem appropriate and I would thus like to invite you to prepare a revised MS for further consideration.

With the best wishes, Helge

Dear Dr. Chuang,

thank you very much for submitting a revised version of your manuscript on sulphate dynamics in sediments of mangrove dominated lagoons. I will contact the reviewers and ask them about their opinion about the revised MS.

With the best wishes, Helge Niemann

Dear Dr. Chuang,

thank you very much for handing in a revised version of your MS. The content has improved substantially and I only have a few technical details open that I would like you to address. Additionally, one of the reviewers provided some general thoughts.

Helge Niemann
Page Line 12/13: mark inserted sentence with commas: “It is surprising that at many sites, particularly within Groups 1 and 2 in the inner zone of both lagoons (1CEL, 2CEL, 3CEL and 1CH), high concentrations….

Page 10, line 20 ff: modify accordingly: There are several possible explanations for these observations: Firstly…. Secondly…. Thirdly…

Page 14, L31: ions in formula are wrong/incomplete. Sulphate is SO4 (4 in lower case and smaller than the font size than O) 2- (2- in upper case with lower font size than O). Check also chlorinity


Further thoughts by a reviewer:

1. Why is a lagoon/estuary that is receiving excess sulfate emitting more methane that other mangrove systems? The addition of sulfate would enhance the oxidative capacity of the system.

2. What is the concentration of the freshwaters where the anhydrite was dissolved? To increase the pore water concentration in these coastal sediments by mM amounts requires a significant contribution of sulfate. I would guess the groundwater would contain 5-10 mM sulfate. Is that reasonable?

3. It remains unclear to me why AOM would be inactive even if there is a lot of competition for sulfate. In other systems with high OM and high methane, the competition is eliminated and both systems enabled by spatially separating the organoclastic and AOM zones. Both processes are possible.

4. I am still suspect that mangrove systems would have such a high relative abundance of non-competitive substrates in comparison to salt marshes and places with high vegetative detritus. Fascinating.

Technical Corrections:
Page 8, line 26: replace ‘chlorine’ with ‘chloride’
Page 9, line 32: put a space between ‘sulfate’ and ‘and’

I understand that you can not fully address these concerns, but I’d like to encourage you to address them in the text and provide at least an “educated guess”.

With the best wishes, Helge Niemann