Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

Zhang, Yuanyuan; Su, Youheng; Li, Zhe; Guo, Shuhui; Lu, Lunhui; Zhang, Bin; Qin, Yu

doi:https://doi.org/10.5194/bg-2021-234

Preprints

https://doi.org/10.5194/bg-2021-234

Preprints

29 Sep 2021

| 29 Sep 2021

Status: this preprint has been withdrawn by the authors.

Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

Abstract. Methane (CH₄) emissions from freshwaters to the atmosphere have a profound impact on global atmospheric greenhouse gas (GHG) concentrations. Anthropogenic footprints such as dam construction and reservoir operation significantly changed the fate and transport of CH₄ in freshwaters. The type of particulate organic carbon (POC) in reservoirs is a critical factor controlling CH₄ production and emissions. However, little is known of how reservoir operation mediates the distribution of POC and regulates CH₄ accumulation in cascade hydroelectric reservoirs. Here, spatial and temporal variations in POC and CH₄ were explored in the Xiluodu (XLD) and Xiangjiaba (XJB) reservoirs which are deep valley dammed cascade reservoirs located in the main channel of the upper Yangtze River. Based on the δ¹³C-POC and N / C mole ratios of particulate organic matter, the results of multi-endmember stable isotope mixing models by a Bayesian model show that terrestrial POC and autochthonous POC accounted for approximately 56 ± 19 % and 42 ± 19 % (SD, n = 181) of POC, respectively. CH₄ concentrations and δ¹³C-CH₄ in the cascade reservoirs were potentially influenced by CH₄ oxidation. Together with other physicochemical parameters and structural equation model, these results suggested that the input of terrestrial POC was dominantly influenced by water level variations and flow regulation due to reservoir operation. The cumulative effect of POC caused by cascade reservoirs was not apparent at a bimonthly scale. Terrestrial POC was more likely to dominate CH₄ accumulation in cascade reservoirs under reservoir operation.

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Received: 02 Sep 2021 – Discussion started: 29 Sep 2021

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Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

Interactive discussion

Status: closed

RC1:
'Comment on bg-2021-234', Anonymous Referee #1, 05 Nov 2021

This paper, entitled "Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China" by Zhang et al., systematically quantified the contribution of environmental factors to reservoir methane (CH4) emissions in the two cascade reservoirs along Yangtze River, and highlighted the significant role of terrestrial POC input in CH4 oxidation and accumulation. The topic is interesting and valuable. The manuscript is well written and clear with informative figures. I would therefore have no major issue recommending it for publication.

Citation: https://doi.org/10.5194/bg-2021-234-RC1
- AC1: 'Reply on RC1', Zhe Li, 07 Nov 2021
  
  Dear Editor and Referee #1:
  
  Thanks very much for your kind work. We also thank the Referee #1 for reviewing our manuscript entitled “Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China” and providing us with very positive feedbacks on our study. If there will be any queries on this paper in the future, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
  
  Yours sincerely,
  
  Zhe Li
  
  On behalf of all authors
  
  Citation: https://doi.org/10.5194/bg-2021-234-AC1
RC2:
'Comment on bg-2021-234', Anonymous Referee #2, 26 Nov 2021

Review

Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

By Zhang et al. Biogeosciences

Major comments

This is an interesting paper where the authors study the functioning of the hydropower reservoir on the accumulation and emission of methane. It’s a timely contribution but some edition is needed before it should be accepted for publication. I am not English native and had a hard time understanding the writing particularly in the introduction. I think the writing in this ms should be carefully revised. I made some specific comments below but might be more. Most of the result section is discussion of the results. Finally, I do not clearly see from the results how the dam operation affects POC accumulation.

Specific comments

Tittle: I think dammed is unnecessary to say since reservoirs are dammed…

Lines 56-58. Unclear why the cumulative effect of POC caused by cascade reservoirs should be at a bimonthly scale

Line 70. Revise the phrase “explicitly and well explained”

Lines 796-77. Unclear what you mean with “geomorphological alternation “ and “and nutrients from surrounding communities”

Line 79. Dam, reservoir, impoundment are synonymous to me…aren’t they? Unclear what you mean with “Dam construction and reservoir impoundments”

Line 90. You use supported very close twice. Unclear if you are commenting results from others studies or where does this evidence comes from since a reference is missing here.

Lines 93-94. Please revise “has been received challenges”

Line 96. Predictors for what?

Iine 115. Unclear what you mean with “sophisticated”

Line 119 Correct “physiochemical”

Line 121. Unclear what you mean with “dammed reservoirs”

Line 131. Which parameters?

Line 133. Unclear what you mean with every other month…monthly, bimonthly?

Lines 138-139. Unclear what you mean here “The sampling time of a day was139 controlled between 8:00 AM and 6:00 PM”

Line 142. Revise “disturbance to collected samples”

Line 145-146. Two 10 L water samples? One 0.5 m below the water surface and other above the sediment? Which was the depth of the sampling points?

Line 148. How do you know the water column was well mixed? Did you measure water temperature?

Line 152. Please define here HRT

Line 191. Particulate matter or chlorophyll a (Chl-a) concentration? I am not familiar with this methodology. Could you add any reference?

Line 195. Unclear what you mean with infiltration.

Line 220. Is it ok to use plankton as autochthonous end member? I think periphyton is the widely used community. At least write a couple of sentences regarding your decision.

Line 302-303. This is discussion. Besides, why excrement? Do you mean raw sewage?

Lines 312-325. Discussion.

Lines 335-337. Discussion.

Lines 374-388. Discussion.

Lines 389-411. Most of this section is discussion. Thus, move to discussion.

Citation: https://doi.org/10.5194/bg-2021-234-RC2
- AC2:
  'Reply on RC2', Zhe Li, 03 Dec 2021
  
  Dear Editor and Referee #2:
  Thanks very much for your kind work. We also thank the Referee #2 for reviewing our manuscript entitled “Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China” and providing us with valuable feedbacks and comments to improve our manuscript. The reply of Referee #2’s comments was put in Supplement. If there will be any questions, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
  Yours sincerely,
  Zhe Li
  On behalf of all authors
  
  Citation: https://doi.org/10.5194/bg-2021-234-AC2
  - RC3: 'Reply on AC2', Anonymous Referee #2, 06 Dec 2021
    
    I appreciate the effort made by answering to each of my comments. However, I asked you to explain why did you use phytoplankton as an end member to study allochthony and not periphyton and you answered that you changed the word plankton by periphyton all over the ms. You cannot do that! You have to mention the comunity you actually used and explain why. You cannot just change the name if you used plankton!
    I hope you can explain which community you used and why.
    
    Citation: https://doi.org/10.5194/bg-2021-234-RC3
    
    AC3: 'Reply on RC3', Zhe Li, 07 Dec 2021
    
    We feel sorry for the misunderstanding and inaccurate response about this question and thank the Referee #2 for pointing out this mistake.
    At first, autochthonous organic matter was derived from aquatic production. Our research site, i.e., the Xiangjiaba Reservoir, is a deep-valley large reservoir located in the upper Yangtze River, China. Unlike streams, creeks or some other shallow lakes where dominant primary producers are periphyton communities (Piggott et al., 2015; Trochine et al., 2017), phytoplankton communities contributed almost all the primary productivity and autochthonous organic matter in water column in large water bodies, such as the Xiangjiaba Reservoir. Even there would be periphyton communities who contributed partial autochthonous organic matter in the reservoir, we believed that the relative abundance of periphyton-derived organic matter was negligible because of such large water bodies.
    In our sampling campaign, as indicated in the manuscript, water samples were collected at the main channel of the reservoir. The phytoplankton and zooplankton communities were collected in water by phytoplankton net (diameter of mesh pore 64 μm) and sorted under microscope to represent the endmember of the autochthonous particulate organic matter. This approach was also discussed in some of the previous studies (Grasset et al., 2018; Chen et al., 2018; Tittel et al., 2019; Bueno et al., 2020).
    Here, we would like to withdraw our previous mistake, and keep the term “plankton” in the manuscript. If there will be any questions, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
    
    References
    Bueno, C.C., Frascareli, D., Gontijo, E.S.J., van Geldern, R., Rosa, A.H., & Friese, K., Barth, J.A.C.: Dominance of in situ produced particulate organic carbon in a subtropical reservoir inferred from carbon stable isotopes, Scientific Reports, 10: 13187, 2020.
    Chen, J., Yang, H., Zeng, Y., Guo, J., Song, Y., & Ding, W.: Combined use of radiocarbon and stable carbon isotope to constrain the sources and cycling of particulate organic carbon in a large freshwater lake, China, Science of the Total Environment, 625, 27-38, 2018.
    Grasset, C., Mendonça, R., Villamor Saucedo, G., Bastviken, D., Roland, F., & Sobek, S.: Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter, Limnology and Oceanography, 63, 1488-1501, 2018.
    Piggott, J. J., Salis, R. K., Lear, G., Townsend, C. R., & Matthaei, C. D.: Climate warming and agricultural stressors interact to determine stream periphyton community composition, Global Change Biology, 21, 206-222, 2015.
    Tittel, J., Hüls, M., & Koschorreck, M.: Terrestrial vegetation drives methane production in the sediments of two German reservoirs, Scientific reports, 9, 1-10, 2019.
    Trochine, C., Guerrieri, M., Liboriussen, L., Willems, P., Lauridsen, T. L., Søndergaard, M., & Jeppesen, E.: Factors controlling the stable isotope composition and C: N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures, Freshwater Biology, 62, 1596-1613, 2017.
    
    Citation: https://doi.org/10.5194/bg-2021-234-AC3

Interactive discussion

Status: closed

RC1:
'Comment on bg-2021-234', Anonymous Referee #1, 05 Nov 2021

This paper, entitled "Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China" by Zhang et al., systematically quantified the contribution of environmental factors to reservoir methane (CH4) emissions in the two cascade reservoirs along Yangtze River, and highlighted the significant role of terrestrial POC input in CH4 oxidation and accumulation. The topic is interesting and valuable. The manuscript is well written and clear with informative figures. I would therefore have no major issue recommending it for publication.

Citation: https://doi.org/10.5194/bg-2021-234-RC1
- AC1: 'Reply on RC1', Zhe Li, 07 Nov 2021
  
  Dear Editor and Referee #1:
  
  Thanks very much for your kind work. We also thank the Referee #1 for reviewing our manuscript entitled “Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China” and providing us with very positive feedbacks on our study. If there will be any queries on this paper in the future, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
  
  Yours sincerely,
  
  Zhe Li
  
  On behalf of all authors
  
  Citation: https://doi.org/10.5194/bg-2021-234-AC1
RC2:
'Comment on bg-2021-234', Anonymous Referee #2, 26 Nov 2021

Review

Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China

By Zhang et al. Biogeosciences

Major comments

This is an interesting paper where the authors study the functioning of the hydropower reservoir on the accumulation and emission of methane. It’s a timely contribution but some edition is needed before it should be accepted for publication. I am not English native and had a hard time understanding the writing particularly in the introduction. I think the writing in this ms should be carefully revised. I made some specific comments below but might be more. Most of the result section is discussion of the results. Finally, I do not clearly see from the results how the dam operation affects POC accumulation.

Specific comments

Tittle: I think dammed is unnecessary to say since reservoirs are dammed…

Lines 56-58. Unclear why the cumulative effect of POC caused by cascade reservoirs should be at a bimonthly scale

Line 70. Revise the phrase “explicitly and well explained”

Lines 796-77. Unclear what you mean with “geomorphological alternation “ and “and nutrients from surrounding communities”

Line 79. Dam, reservoir, impoundment are synonymous to me…aren’t they? Unclear what you mean with “Dam construction and reservoir impoundments”

Line 90. You use supported very close twice. Unclear if you are commenting results from others studies or where does this evidence comes from since a reference is missing here.

Lines 93-94. Please revise “has been received challenges”

Line 96. Predictors for what?

Iine 115. Unclear what you mean with “sophisticated”

Line 119 Correct “physiochemical”

Line 121. Unclear what you mean with “dammed reservoirs”

Line 131. Which parameters?

Line 133. Unclear what you mean with every other month…monthly, bimonthly?

Lines 138-139. Unclear what you mean here “The sampling time of a day was139 controlled between 8:00 AM and 6:00 PM”

Line 142. Revise “disturbance to collected samples”

Line 145-146. Two 10 L water samples? One 0.5 m below the water surface and other above the sediment? Which was the depth of the sampling points?

Line 148. How do you know the water column was well mixed? Did you measure water temperature?

Line 152. Please define here HRT

Line 191. Particulate matter or chlorophyll a (Chl-a) concentration? I am not familiar with this methodology. Could you add any reference?

Line 195. Unclear what you mean with infiltration.

Line 220. Is it ok to use plankton as autochthonous end member? I think periphyton is the widely used community. At least write a couple of sentences regarding your decision.

Line 302-303. This is discussion. Besides, why excrement? Do you mean raw sewage?

Lines 312-325. Discussion.

Lines 335-337. Discussion.

Lines 374-388. Discussion.

Lines 389-411. Most of this section is discussion. Thus, move to discussion.

Citation: https://doi.org/10.5194/bg-2021-234-RC2
- AC2:
  'Reply on RC2', Zhe Li, 03 Dec 2021
  
  Dear Editor and Referee #2:
  Thanks very much for your kind work. We also thank the Referee #2 for reviewing our manuscript entitled “Methane accumulation affected by particulate organic carbon in upper Yangtze deep valley dammed cascade reservoirs, China” and providing us with valuable feedbacks and comments to improve our manuscript. The reply of Referee #2’s comments was put in Supplement. If there will be any questions, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
  Yours sincerely,
  Zhe Li
  On behalf of all authors
  
  Citation: https://doi.org/10.5194/bg-2021-234-AC2
  - RC3: 'Reply on AC2', Anonymous Referee #2, 06 Dec 2021
    
    I appreciate the effort made by answering to each of my comments. However, I asked you to explain why did you use phytoplankton as an end member to study allochthony and not periphyton and you answered that you changed the word plankton by periphyton all over the ms. You cannot do that! You have to mention the comunity you actually used and explain why. You cannot just change the name if you used plankton!
    I hope you can explain which community you used and why.
    
    Citation: https://doi.org/10.5194/bg-2021-234-RC3
    
    AC3: 'Reply on RC3', Zhe Li, 07 Dec 2021
    
    We feel sorry for the misunderstanding and inaccurate response about this question and thank the Referee #2 for pointing out this mistake.
    At first, autochthonous organic matter was derived from aquatic production. Our research site, i.e., the Xiangjiaba Reservoir, is a deep-valley large reservoir located in the upper Yangtze River, China. Unlike streams, creeks or some other shallow lakes where dominant primary producers are periphyton communities (Piggott et al., 2015; Trochine et al., 2017), phytoplankton communities contributed almost all the primary productivity and autochthonous organic matter in water column in large water bodies, such as the Xiangjiaba Reservoir. Even there would be periphyton communities who contributed partial autochthonous organic matter in the reservoir, we believed that the relative abundance of periphyton-derived organic matter was negligible because of such large water bodies.
    In our sampling campaign, as indicated in the manuscript, water samples were collected at the main channel of the reservoir. The phytoplankton and zooplankton communities were collected in water by phytoplankton net (diameter of mesh pore 64 μm) and sorted under microscope to represent the endmember of the autochthonous particulate organic matter. This approach was also discussed in some of the previous studies (Grasset et al., 2018; Chen et al., 2018; Tittel et al., 2019; Bueno et al., 2020).
    Here, we would like to withdraw our previous mistake, and keep the term “plankton” in the manuscript. If there will be any questions, please don’t hesitate to contact us at lizhe@cigit.ac.cn.
    
    References
    Bueno, C.C., Frascareli, D., Gontijo, E.S.J., van Geldern, R., Rosa, A.H., & Friese, K., Barth, J.A.C.: Dominance of in situ produced particulate organic carbon in a subtropical reservoir inferred from carbon stable isotopes, Scientific Reports, 10: 13187, 2020.
    Chen, J., Yang, H., Zeng, Y., Guo, J., Song, Y., & Ding, W.: Combined use of radiocarbon and stable carbon isotope to constrain the sources and cycling of particulate organic carbon in a large freshwater lake, China, Science of the Total Environment, 625, 27-38, 2018.
    Grasset, C., Mendonça, R., Villamor Saucedo, G., Bastviken, D., Roland, F., & Sobek, S.: Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter, Limnology and Oceanography, 63, 1488-1501, 2018.
    Piggott, J. J., Salis, R. K., Lear, G., Townsend, C. R., & Matthaei, C. D.: Climate warming and agricultural stressors interact to determine stream periphyton community composition, Global Change Biology, 21, 206-222, 2015.
    Tittel, J., Hüls, M., & Koschorreck, M.: Terrestrial vegetation drives methane production in the sediments of two German reservoirs, Scientific reports, 9, 1-10, 2019.
    Trochine, C., Guerrieri, M., Liboriussen, L., Willems, P., Lauridsen, T. L., Søndergaard, M., & Jeppesen, E.: Factors controlling the stable isotope composition and C: N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures, Freshwater Biology, 62, 1596-1613, 2017.
    
    Citation: https://doi.org/10.5194/bg-2021-234-AC3

Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

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https://doi.org/10.5194/bg-2021-234-supplement

Yuanyuan Zhang, Youheng Su, Zhe Li, Shuhui Guo, Lunhui Lu, Bin Zhang, and Yu Qin

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Short summary

POC in the XLD and XJB reservoirs mainly originates from terrestrial POC (56 %). CH₄ oxidation potentially influences the variations in CH₄ concentrations and δ¹³C-CH₄ in cascade reservoirs. Water level variations and flow regulation caused by reservoir operation are primary factors for the input of terrestrial POC. The cumulative effect of POC at a bimonthly scale was not significant in the XLD and XJB reservoirs. Terrestrial POC displays more persistent impacts on CH₄ accumulation.


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