Dear Dr. Lin et al.,

We have received two reports from two external reviewers. Both suggest that this is an interesting study. However, they also emphasize a need to improve the manuscript. I agree with the reviewer #2 that the methods and results should be revised to improve the content and clarity and the English and language also need to be further polished.

Based on the reviews and your responses, I find that your manuscript could be suitable for publication after Major revisions. Please consider each of the reviews carefully and submit a revised version along with a point-to-point response.

Best regards,
Yuan Shen
Associate Editor

Dear Dr. Lin,

We appreciate your effort in submitting the revised manuscript. Finding external referees for this particular manuscript proved to be quite challenging. Unfortunately, the previous two referees were unavailable to evaluate your revisions, which resulted in a significant delay. We sincerely thank you for your patience throughout this process.

We have now received two reports that assess the submitted revisions. Both reports indicate the need for additional changes to improve the clarity, summary, and organization of your paper. Taking this feedback into account, I believe a moderate to substantial amount of revision is required. Therefore, I am returning the manuscript to you so that you can incorporate the suggested changes.

Please refer to the appended review comments below.

Best regards,
Yuan Shen
Associate Editor


Report #1:
The manuscript titled "Conceptual models of dissolved carbon fluxes considering interannual typhoon responses under extreme climates in a two-layer stratified lake " aims to discuss the impacts of extreme typhoon climates on the distribution of carbon (C) in small subtropical lakes, taking the Yuan-Yang Lake (YYL) as an example. The manuscript highlights how typhoons rapidly introduce significant amounts of terrestrial C into the lake, influencing the water chemistry in the lake. The study develops a conceptual dissolved C model and proposes that the loading of allochthonous C and river inflow intrusion affect the distribution of dissolved inorganic C (DIC) and dissolved organic C (DOC) in the lake under extreme climate conditions. This is an interesting study, but some modifications are required.

General comments:
More references should be included in the Introduction section on how extreme climate will impact the water chemistry in both small and large lakes. (e.g. 2023 Water Research, 10.1016/j.watres.2022.119448 and 2020 Water Research 10.1016/j.watres.2020.1 16471)
There are also some grammar and terminology issues to be addressed.

Specific comments:
Figure 1 I can’t see any useful information on how river intrusion will change the upper and lower DOC-DIC from this figure. The allochthons C shown in the lower panel seem a little bit too short. Technically, the inflowing river mouth areas are significantly influenced by the rainstorm-induced C inputs. Also, only typhoons are discussed in the manuscript and I think the other extreme climate examples should be removed. The figure needs to be reorganized.
Figure 2. Inflowing rivers should be included in this figure.
Figure 3 I can see much higher Chl-a in the lower than in the upper layer of this lake. Higher phytoplankton biomass is usually found in the upper layer of a specific lake. Please double-check your data.
Line 58: It should be written as fluxes.
Line111: It should be written as Fig. 2.
Line139：The specific wavelengths used were 430 nm (blue) and 662 nm (red). Was the portable fluorometer used to measure Chl-a? Please reorganize the text.
Line 149: It should be written as Fig. 1.
Line 160: It should be written as Fig. 2.
Line 246: Please change Lower NEPDOC in the formula, and pay attention to your language.
Line 284: It should be written as Fig. 6c.
Line 752: It should be written as Fig. 8.


Report #2:
I think this is a nice contribution that couples measurements + modeling on an important issue of quantifying carbon cycling in lakes globally. However, before publication, I think there is still some lacking organization, synthesis of clear results, and connection to the study’s broader objective. I have some suggestions and concerns that fall largely into the following categories that the author could consider incorporating:

1) Introduction edits: improve the flow to really synthesize the importance. There is also a harsh transition to talking about precipitation in line 80, I think you can weave concepts a little more strategically. From my interpretation, I see 4-5 paragraphs in the introduction addressing the following: we need to keep improving quantifying carbon flux in lakes globally, it is not clear how climate will impact these fluxes, extremes in precipitation are likely to increase in a lot of parts of the world (likely in this study site as well), and it’s been shown that precipitation has impacted carbon cycling in lake systems, but it remains foggy. So, in this study….

2) Results edits: I think the results section still remains hard to follow, it was suggested from a previous review that the descriptor “nonseasonal” is confusing. I agree and I think it still remains in the manuscript and hasn't been changed all over (maybe just a few places). If you are also going to use seasons, should you consider using a hemisphere descriptor for clarity (for example, boreal fall for Northern Hemisphere fall…)? I would maybe suggest being clearer about your section headers. Maybe divide into typhoon and non typhoon years and then into measured and modeled results. I think right now it goes back and forth a lot and is hard to follow. I think it will also improve when the term “nonseasonal” is removed.

3) Figure edits: Fig 1: In conceptual model, can droughts not also impact lake thermal stratification? Why is DIC connected to photosynthesis and respiration but not DOC? I believe the DOC pool is influenced by those processes? How does the bar of different C pools (auto/allocthon) on the bottom fit into the conceptual model? For example, sediments are in blue like autochthonous C, but it is likely your sediments are a mixture (likely dominated) by allochthonous C too. There are also additional biogeochemical processes + C flux from sediments that aren't addressed in the figure (but are brought up in the conclusion)...
Fig 2: I would make your markers bigger on the map.
Fig 3: should you maybe just write the p values on the respective graph panels instead of the key to the values (ns, *, **)? For example, since you use the term “nonseasonal” I think ns means that, but I do not believe that is the case…
700-702: I see no red values in this table..
706: Perhaps rewrite figure caption to: “Conceptual diagram of river intrusion (red arrows) and thermal stratification 706 (red dashed line) influencing dominant responses of DIC and DOC in a subtropical two-layer 707 stratified lake under extreme climates”
Also the tables in the format (as is) are not well aligned (e.g, titles on two lines, hard to read), you might need to adjust. Maybe add your “Level” characterizations to Table 2 or 3 - the differentiation is getting a bit lost in the methods.

4) Discussion: consider sub-organizing the discussion into typhoon/non typhoon years, or model/measured data, or how the modeled/measured data disagree? I think this will help add flow that feels missing as is. Reviewer #1 suggested adding some additional sentences on seasonal CO2 emission flux, but it is not popping out to me right now...

5) General specifics to be added: I mentioned a few line specific places where I think you can just provide a bit more detail to give the reader clarity, but there are other places throughout the manuscript that can benefit from this. A sentence that I marked but can be used as an example: “The water depth is not only steady but also changes”< I think additional detail is needed to clarify this. Another in the introduction: For example: “River inflows, sediment, and respiration contribute to DIC loading into lakes”>> sediment what? Flux? Respiration in the water column or post depositional biogeochemical processes? There are a myriad of steps that exist between...


Line specific comments:
Line 21: models to model
Line 24: should transportation be transformation?
Line 28: change a load to loading
Line 39: fresh or salty water columns- can you note?
50: with to within
Line 80: big scale shift to talking about rain– expand on what is known about rainfall impacting DOC and C cycling…
121-123: what nutrients? What organisms– can you be more specific?
183/184: Fix sentence “The water depth is not only steady but also changes”> also is this different font?
233: different font
255: different font
256-258: clarify this sentence– what is the difference between typhoon and non typhoon years here, and what is this result trying to compare or conclude?
261: be more specific- what are you comparing in this t test?
275-276: should this conclusion (correlation with resp, DIC and chl) be in the discussion? Or give a reference for this interpretation…
282: define NSE
285: best fit different text
298-299: is this a statistical output or an interpretation?
311-312: Can you clarify “the upper layer DIC and DOC consumed approximately 3.7 times more DIC in the typhoon years than in the non-typhoon years”? How does DIC and DOC consume, maybe missing biogeochemical steps here….
323: in saying “upper layer ratios” are you referring to DIC:DOC in the upper layer? Likely should clarify….
326: You talk about ratios varying within this paragraph, but only use a value at the very end in regards to the lowest… keep that consistent throughout the paragraph if you’d like to compare values/numbers.
341-345: more specifically describe the result or point of this result.
351: be more specific about what parameters changed.. What do you consider water quality data? How might remineralization change with anoxic conditions.
355: probably good to specifically reference microorganisms rather than just organisms here?
365: corresponds or proves hypothesis?
372-375: Can you clarify the following: “Additionally, 372 because of the absence of typhoon-induced mixing and allochthonous C loading, the absolute 373 values of total fluxes in the non-typhoon years were less than those the non-typhoon years 374 (Table 4). “
377: seasonal C what? Concentration? Flux? Sequestration?
408: Remove the phrasing “to our knowledge”
414: two commas
420: Typhoon disturbances or seasons?
421: Rephrase sentence:” Without typhoons, the strength of thermal stratification was the primary determinants (determinant of) the seasonal and interannual patterns of DIC and DOC concentration. Typhoon-induced upwelling and loading facilitated 102.2 mg-DIC m-3 d-1 and 62.3 mg-DOC m-3 d-1 flux in YYL, respectively.”

Dear Dr. Lin,

We have received reports from the previous two reviewers. While one reviewer offered only minor editorial suggestions, the other still raised important concerns about the writing, structure, and length of the results, figures, and discussion sections. Please refer to the attached review comments for details. I believe these comments will be beneficial in enhancing the quality and clarity of your manuscript.

Please consider the reviewer comments thoughtfully and proceed with appropriate revisions.


Best regards,
Yuan Shen
Associate Editor


Report #1:
Fig. 1 Yuang-Yang Lake in the lower panel and Yuanyang Lake in the right panel should be changed to Yuan-Yang Lake.

Report #2:
I appreciate the changes and improvements that were made to this manuscript, but I still think additional editing needs to be completed before acceptance for publication. In this second round of peer review, I believe that the results section and amount of figures is too long, and should be compressed to detail the most meaningful results. As written, I find the results still extremely confusing to get through, and find it hard to streamline what is important and how the authors reach the conclusions from the figures and results presented as is.

I would suggest additional time in re-structuring the results. Firstly, I still don’t understand how you talk about the measurements (observations) and the simulated (conceptual model) data. It seems like most of your data is simulated, but you still made measurements- can you differentiate more clearly?

Right now, I have also found that many of the statements seem redundant and this flows into the discussion. Much of the discussion just reads like a continuation of results, not an actual evaluation of the results in the context of how it’s expanded what is known about the current literature/biogeochemical processes in subtropical lakes. I would suggest spending more time discussing specific results as they tie to specific or broader patterns in biogeochemical processes, and removing some of the truly analytical results (perhaps moving those into the results section, like lines 384-391).

I also think you can move some of your figures into supplemental. In my opinion, there is a lot of redundancy (like figures 5 and 6 without clearer explanation of Level 1/2) and figure 4 doesn’t seem to add much as a priority figure. Can you consider more succinctly combining some of the findings into figures that make things easier to follow? For example- do you think Figure 7 and 8 are both necessary? Figure 9 comprehensively brings together observations and modeled values (I like this). Is Figure 3 populated by observations or modeled values?

So, my overall analysis would be to compress the results and figures and expand the discussion as it relates to biogeochemical processes.

Other conceptual things that need clarity:
What do you mean by interannual variability: are you just referring to seasonal change? For example, how is 3.4 different than 3.1? Can you clarify within section 3.3 too?
Can you clarify/write in more detail your methods of sample collection? Did you collect separate samples for DOC that was not filtered on the GFF filters? What did you use the 0.7 um particulates for? That is too big of a mesh size for DOC concentrations. Did you only do some of the samples for water quality once? And then the outflow monthly? Maybe include the number of observations on your figure/within your figure caption.
Can you please provide further clarity in the text on what is Level 1 and 2 and what climate extremes does it relate to? Localized extremes? Already known modeled extremes?
Another read through to clarify (concepts + references) and condense sentences. An example where sentence to me was hard to follow:
369: “Therefore, these physical and biogeochemical processes might describe different patterns between the upper and lower layers (Fig. 4). “In summer, the spatial differences between layers in DIC and DOC were inhibited due to strong thermal stratification, describing the positive upper net primary production and lower negative net primary production (Lin et al., 2021).”
What specific patterns? What would we expect (provide reference)? Spatial differences between layers in DIC and DOC< what does that mean? Across a transect? Within layers? How is it describing the positive/negative primary production.. Missing a link between DIC/DOC variability and PP….

43: Reference at the end of that sentence ?
45: important for humans because of the C processing? Or because of C processing providing availability to foodwebs that support human resources? Alternatively, you could mean C storage? < Consider making a better connection there.
49: Start a new paragraph when you begin talking about small lakes.
56: Remove however
66: Consider rephrase “Not only taking is taking in situ measurements difficult, but resolving the dynamics and interactions…. Remains complex.”
102: was that a different year than 2004, can you clarify?
122: remove second its
128: the world annually (half of totally precip in YYL annually)
140-144: please clarify these sentences. You collected water via van Dorn for various parameters (DOC/DIC/Chla.a). You also collected GFF filters for POC at the outflow which would be the filtrate– as 0.7 represents POC not DOC– can you clarify? So, you had liquid samples and filtrate, correct?
148-153: Provide more detail/clarity here in what you did. What did the fluormeter measurements give you? What machine was used to measure Chla after methanol extraction?
152-153: do you mean all analysis was complete within 72 hours of exposure to light to reduce the degradation?
159: Add a sentence in how the observable data was used within the conceptual equations model– how did you make that link?
161: extra dash there.
165: remove one of the uses of meteorological
172: did you sample the secchi disk depth at a certain interval in that time frame?
173: How did you confirm there were four strong typhoons recorded? Wind speed/other meteorological parameters? Clarify.
173-174: Please clarify this concept. It is not 35.6% of annual rainfall, it’s 35.6% of rainfall across 2 years of typical rainfall (>3000 mm/y).
176: So, 2017 and 2018 are both below average years? ~1268 mm/y instead of 3000 mm/y as suggested in line 127?
177: Was average water depth higher in 2015/2016?
178-179: In general, please clarify how you defined typhoon/non typhoon years at the beginning of this paragraph. The way it is written makes me think the rainfall in 2015 and 2016 is less than 2017/2018 (which you are considering non typhoon), I think you need to be really clear that it’s not rainfall alone, but it is temporal variability of the rainfall (falls all between X months), avg wind speed higher, discharge overall lower, etc.
194: variated to varied
197: add “was used to establish”
205: missing parentheses
219: Start new paragraph when talking about climate change.
224: what were the extreme conditions based on? Qin? how did you define Level 1 and Level 2 respectively? How can we compare this to real-time projections of what is expected in climate scenarios for the YYL– rainfall amounts?
267: I am confused- are these results modeled or measured?
299-300: can you clarify what you are comparing here- DIC measured/modeled? Best fit to what sort of regression/relationship?
310-311: Can you clarify how you got to that conclusion? What did you compare- state it directly?
318: Was this relationship between Fc and Flux DIC in both typhoon and non typhoon years– consider rephrasing the sentence as you are talking about both?
320-321: consider rephrasing sentence: two ‘declines’ in a short sentence.
322: What’s with the quotations? The text size also looks different…
You start section 3.4 with mentioning these are simulated results, but seemingly the references to figures in the above sections are also the conceptual model simulations. I find this confusing. Streamline what is observed and what is modeled.
328/329: looks like different text size
359: As Table 1 shows, four strong typhoons were recorded, contributing a total of 2,254 mm 173 of precipitation in all 24 months of 2015 and 2016, This accounted for 35.6% of the annual 174 precipitation. However, no typhoon rainfall was recorded at YYL in 2017 and 2018; the total 175 precipitation in that 2-year period was around 2,537 mm. << how does this compare to what is said around lines 173?
410-413 repeating the concept in 367-369
443-445 I would rephrase this. I don’t think the words autochthonous or photo biochemical is used efficiently here. (e.g., within lake, primary production, photochemical degradation might be better choices to incorporate)

Dear Dr. Lin,

Thank you for your diligent work in addressing three rounds of significant revisions. The revised manuscript has shown significant improvement. I am pleased to accept it for publication. There are a few minor technical corrections that require attention, see below:

line 38: combine double sets of parentheses

line 266 “Measuring data” implies an ongoing process of data collection. I think the author meant “Measurement data” or “Measured data”.

line 485 Data availability: Please be more specific about which data were taken from these references. We recommend that any data set used in your manuscript is submitted to a reliable data repository and linked from your manuscript through a DOI.

Best regards,
Yuan Shen
Associate Editor