the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Sep 2022
Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)
Abstract. This study is based on multiproxy data gained from a 14C-dated 6.5 m long sediment core and a 210Pb-dated 23 cm short core retrieved from Lake Rauchuagytgyn in Chukotka, Arctic Russia. The main objectives are to reconstruct the environmental history and ecological development of the lake during the last 29k years and to investigate the main drivers behind bioproduction shifts. The methods comprise age-modeling and accumulation rate estimation, light-microscope diatom species analysis (74 samples), organic carbon, nitrogen, and mercury analysis. Diatoms have appeared in the lake since 21.8 cal ka BP and are dominated by planktonic Lindavia ocellata and L. cyclopuncta. Around the Pleistocene-Holocene boundary, other taxa including planktonic Aulacoseira and benthic fragilarioid (Staurosira) and achnanthoid species increase in their abundance. There is strong correlation between variations of diatom valve accumulation rates (DAR, mean 176.1 109 valves m2 a1), organic carbon accumulation rates (OCAR, mean 4.6 g m-2 a-1), and mercury accumulation rates (HgAR, mean 63.4 µg m-2 a-1). We discuss the environmental forcings behind shifts in diatom species and found responses of key-taxa to the cold glacial period, postglacial warming, Younger Dryas, and the Holocene Thermal Maximum. The short core data likely suggest recent change of the diatom community at 1907 CE related to human-induced environmental change. Significant correlation between DAR and OCAR in the Holocene interglacial indicates within-lake bioproduction as the main source of carbon deposited in the lake sediment. During both glacial and interglacial episodes HgAR is mainly bound to organic matter in the lake associated to biochemical substrate conditions. There were only ambiguous signs of increased HgAR during the industrialization period. We conclude that pristine Arctic lake systems can serve as CO2 and Hg sinks during warming climate driven by insolation-enhanced within-lake primary productivity. Maintaining intact natural lake ecosystems should therefore be of interest to future environmental policy.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-985', Anonymous Referee #1, 10 Nov 2022
This is an interesting and data-rich research paper from a remote region of Chukotka, far eastern Russian Arctic. Here, the environmental history of Lake Rauchuagytgyn was reconstructed during the last 29 ka years, using 14C-dated sediment records of diatoms frustules together with organic carbon, nitrogen and mercury accumulation rates. Diatom assemblages responded to the major Pleistocene and Holocene environmental changes through shifts in species composition and abundance. It appears that organic carbon in lake sediments has largely autochthonous origin, as it is strongly correlated with the diatom frustule accumulation rate. This implies that this type of arctic lake may play an important role as a carbon sink as most organic carbon (OC) is effectively buried in the sediments. However, OC concentrations in the sediments do not reflect the amount of carbon dioxide emitted during the ice melt, and this may be substantial.
I suggest that you change your discussion, conclusions and the abstract reflecting on existing uncertainty regarding the role of arctic lakes in the global carbon cycle.
The age-depth model of the long core, which was based on 23 14C bulk organic carbon dates in a 651.75 cm core, was developed using LANDO modelling. This is in a broad agreement with the earlier published core chronology using different modelling and this gives extra confidence in the results. The short core was dated using 210Pb and 137Cs. The short core chronology is uncertain for the 7-11 cm interval.
Overall, this is a valuable and thorough contribution to the series of recent publications from this remote arctic region, which may play an important role in the global climate change. It deserves a publication. Substantial uncertainty remains, however, regarding the fate of carbon in artic lakes and their role as sinks or emitters of carbon.
The manuscript is well written for the most part, although some of the sentences need clarifying or re-writing. I highlighted those in the attached pdf copy. In addition, there are several minor grammar mistakes which I corrected and highlighted in the attached pdf file.
Below I outlined sentences which need re-writing and other comments.
I suggest combining short and long core diatom and biochemistry data to facilitate visual interpretation of the results, please see the details below. This will also reduce the number of figures in this manuscript, which is quite high. My other concern is the way sedimentation rates were calculated. It is not well described in Methods. I give the details below.
Abstract:
Line 37. Please change this sentence as uncertainty exists regarding the role of arcitic lakes in the global carbon cycle.
Methods.
Lines 195-205.
I suggest replacing the text with formulae and short justification of your calculations of sedimentation rates. You need to clearly describe how sedimentation rates were calculated to ensure the validity of the results.
Results.
Please combine Figures 5 and 6 into one indicating a gap between two cores. This would facilitate better visualization of the floristic changes.
Similarly, please combine Figures 8 and 9 into one figure, this would ease interpretation of the results.
Line 284. You refer here to Figure 5, not Figure 9.
Discussion.
Section 5.2.
Consider reviewing this section, it requires clarifying and re-writing. Use combined Figure made from Figures 8 and 9 to describe the changes and correlations between the profiles.
Lines 400-405. You need to re-write this passage about sediment accumulation rates, it is not entirely clear.
Line 407. This sentence about lake ontogeny (which is lake development) looks incomplete to me. You need to explain how lake ontogeny changes, this is a process.
Lines 409-410 – Similarly, it is difficult to understand these sentences. You need to think clearly what you are trying to say here, and re-write this passage. I highlighted it in the pdf copy.
Lines 462-465. These two sentences require reviewing and rewriting, it is not entirely clear what is the meaning there.
Figures.
Figure 10 is not easy to interpret, I do not think that this Figure is necessary, I suggest removing it.
It would be better to combine Figures 8 and 9. The combined Figure can be used to describe and discuss the trends in the profile changes and correlations between them.
If you wish to display the correlations, you can use a table.
-
AC1: 'Author reply on RC1', Boris K. Biskaborn, 06 Mar 2023
Dear Reviewer #1
Thank you very much for reviewing the manuscript and your work invested in giving feedback to our study. We are specifically grateful for the comment on remaining uncertainties on the fate of CO2 that is not only accumulated in the sediment but also released after ice-brake up of the lake. We see that we did not involve this aspect enough in the manuscript, even though we considered it in the overall study. We will carefully address this topic in all relevant chapters and make sure that our findings are based on the presented core data.
We will also carefully use your detailed comments to revise the manuscript and provide point-to-point answers and explanations of what we change. Yes, we can combine long and short core graphs to reduce the number of figures, and we can describe better our SR calculations using equations.
Please find our detailed answers in the revision note attached (5 pages PDF).
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AC1: 'Author reply on RC1', Boris K. Biskaborn, 06 Mar 2023
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RC2: 'Comment on egusphere-2022-985', Anonymous Referee #2, 14 Feb 2023
Comments on the manuscript entitled 'Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)' by Biskaborn et al.
This manuscript explores past environmental changes during the last 29k years based on diatom and geochemical records of a well-dated lake sediment core in Chukotka, which is a less investigated region. The results are interesting, particularly the relationships between diatom accumulation rates, organic carbon accumulation rates and mercury accumulation rates. I have one major concern on the driving force on diatom flora shifts (see details as follows). I suggest that this manuscript can be acceptable after major revions.
Major concern:
Although authors have provided potential driving forces for diatom flora shift, the mechanism is still ambiguous. The major trends in diatom flora are that an increase in benthic species during the early Holocene, and then the gradual replacement of benthic taxa by planktonic species. This general trend might be closely linked to temperature-driven changes in ice-cover period. For example, short ice-cover period in the early Holocene promote light penetration and the availability of littoral habitats.
In addition, effects of DOC on diatom flora should be considered during lake ontogeny since the deglaciation. DOC can be an important resilience against from external driving forces.
Some references might be useful
Engstrom, D. R., et al. (2000). "Chemical and biological trends during lake evolution in recently deglaciated terrain." Nature 408(6809): 161-166.
Hu, Z., et al. (2018). "The Landscape–Atmosphere Continuum Determines Ecological Change in Alpine Lakes of SE Tibet." Ecosystems 21(5): 839-851.
Chen, X., et al. (2018). "Direct and indirect effects of Holocene climate variations on catchment and lake processes of a treeline lake, SW China." Palaeogeography, Palaeoclimatology, Palaeoecology 502: 119-129.
Wischnewski, J., et al. (2011). "Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries." Global Change Biology 17(11): 3376-3391.I suggest that authors could clarify the major underlying driving forces of diatom flora shifts, specify the meanings of PC1 and PC2.
Other minor revisions:
1) L31-32: the responses to climate events are not very clear, probably due to low resolution of diatom records
2) L33-34: 'human-induced environmental change', please specify, atmospheric deposition?
3) L34-35:C/N ratios are generally larger than 10 during the Holocene, suggestive of the mixture of within lake production and terrestrial organic matter. Therefore, it should be cautious to draw this conclusion.
4) Section 2 Study site: Please provide more details on aquatic plants in this lake. Are there macrophytes or mosses around the lake shore? This is important to explain the development of benthic diatoms during the Holocene. In addition, water chemistry data should be provided, such as pH, conductivity, and dissolved organic carbon,
5) Section 3.5 Data processing and statistics: L 173, generally, square-root transformation of percentage data were used in CONISS, please check. In addition, the number of zones should be tested by the broken stick model (Bennett, 1996).
Bennett, K. D. (1996). "Determination of the number of zones in a biostratigraphical sequence." New Phytologist 132(1): 155-170.6) L243-246, please check the units of DVC and DAR, superscript should be used.
7) L330-331: thick ice due to long ice-cover period probably reduces light penetration?
8) L339-340: more detailed explanation for the linkage between diatom flora shift and climate. During this stage, the major change is the disappearance of Linvidavia bodanica and L. cyclopuncta
9) L354-355: rising alkalinity might be linked to enhanced chemical weathering intensity of bare rocks under warmer and wetter climate during the early and mid-Holocene
10) L371: the influx of melted water during the spring and summer probably increase the mixing?
11) L396: Here, potential effects of nitrogen deposition?
12) L488-489: prolonged ice-free period increases the availability of littoral habitats
13) Figure 7: legends for the two figures are needed, depths can be changed to 'ages'
14) Figure 8: for the total percentage of light Lindavia, L. bodanica might be different from other species, since this taxon has relatively heavy valves, which are similar to some Aulacoseira species (see the review by Saros and Anderson, 2015, The ecology of the planktonic diatom Cyclotella and its implications for global environmental change studies).
Citation: https://doi.org/10.5194/egusphere-2022-985-RC2 -
AC2: 'Reply on RC2', Boris K. Biskaborn, 06 Mar 2023
Dear Reviewer #2
Thank you very much for taking your time to review the manuscript. We are grateful for the comments you provided to ecology and environmental interpretation of diatom community shifts. We find that your comments on the increase of benthic species in course of changing ice cover period in the Early Holocene fits well into our discussion that was focused mainly on stratification before. We are also grateful for the valuable hints on DOC effects on diatoms during lake ontogeny parallel to deglaciation processes. We will carefully consider the list of additional papers you provided to make sure our discussion on diatom assemblage responses is based on state-of-the art relevant literature. We also will make sure that the revised discussion of underlying driving forces of diatom shifts is in accord with the PCA results as you suggested.
Please find our detailed answers in the revision note attached (6 pages PDF).
With best regards,
on behalf of all authors
Boris Biskaborn
-
AC2: 'Reply on RC2', Boris K. Biskaborn, 06 Mar 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-985', Anonymous Referee #1, 10 Nov 2022
This is an interesting and data-rich research paper from a remote region of Chukotka, far eastern Russian Arctic. Here, the environmental history of Lake Rauchuagytgyn was reconstructed during the last 29 ka years, using 14C-dated sediment records of diatoms frustules together with organic carbon, nitrogen and mercury accumulation rates. Diatom assemblages responded to the major Pleistocene and Holocene environmental changes through shifts in species composition and abundance. It appears that organic carbon in lake sediments has largely autochthonous origin, as it is strongly correlated with the diatom frustule accumulation rate. This implies that this type of arctic lake may play an important role as a carbon sink as most organic carbon (OC) is effectively buried in the sediments. However, OC concentrations in the sediments do not reflect the amount of carbon dioxide emitted during the ice melt, and this may be substantial.
I suggest that you change your discussion, conclusions and the abstract reflecting on existing uncertainty regarding the role of arctic lakes in the global carbon cycle.
The age-depth model of the long core, which was based on 23 14C bulk organic carbon dates in a 651.75 cm core, was developed using LANDO modelling. This is in a broad agreement with the earlier published core chronology using different modelling and this gives extra confidence in the results. The short core was dated using 210Pb and 137Cs. The short core chronology is uncertain for the 7-11 cm interval.
Overall, this is a valuable and thorough contribution to the series of recent publications from this remote arctic region, which may play an important role in the global climate change. It deserves a publication. Substantial uncertainty remains, however, regarding the fate of carbon in artic lakes and their role as sinks or emitters of carbon.
The manuscript is well written for the most part, although some of the sentences need clarifying or re-writing. I highlighted those in the attached pdf copy. In addition, there are several minor grammar mistakes which I corrected and highlighted in the attached pdf file.
Below I outlined sentences which need re-writing and other comments.
I suggest combining short and long core diatom and biochemistry data to facilitate visual interpretation of the results, please see the details below. This will also reduce the number of figures in this manuscript, which is quite high. My other concern is the way sedimentation rates were calculated. It is not well described in Methods. I give the details below.
Abstract:
Line 37. Please change this sentence as uncertainty exists regarding the role of arcitic lakes in the global carbon cycle.
Methods.
Lines 195-205.
I suggest replacing the text with formulae and short justification of your calculations of sedimentation rates. You need to clearly describe how sedimentation rates were calculated to ensure the validity of the results.
Results.
Please combine Figures 5 and 6 into one indicating a gap between two cores. This would facilitate better visualization of the floristic changes.
Similarly, please combine Figures 8 and 9 into one figure, this would ease interpretation of the results.
Line 284. You refer here to Figure 5, not Figure 9.
Discussion.
Section 5.2.
Consider reviewing this section, it requires clarifying and re-writing. Use combined Figure made from Figures 8 and 9 to describe the changes and correlations between the profiles.
Lines 400-405. You need to re-write this passage about sediment accumulation rates, it is not entirely clear.
Line 407. This sentence about lake ontogeny (which is lake development) looks incomplete to me. You need to explain how lake ontogeny changes, this is a process.
Lines 409-410 – Similarly, it is difficult to understand these sentences. You need to think clearly what you are trying to say here, and re-write this passage. I highlighted it in the pdf copy.
Lines 462-465. These two sentences require reviewing and rewriting, it is not entirely clear what is the meaning there.
Figures.
Figure 10 is not easy to interpret, I do not think that this Figure is necessary, I suggest removing it.
It would be better to combine Figures 8 and 9. The combined Figure can be used to describe and discuss the trends in the profile changes and correlations between them.
If you wish to display the correlations, you can use a table.
-
AC1: 'Author reply on RC1', Boris K. Biskaborn, 06 Mar 2023
Dear Reviewer #1
Thank you very much for reviewing the manuscript and your work invested in giving feedback to our study. We are specifically grateful for the comment on remaining uncertainties on the fate of CO2 that is not only accumulated in the sediment but also released after ice-brake up of the lake. We see that we did not involve this aspect enough in the manuscript, even though we considered it in the overall study. We will carefully address this topic in all relevant chapters and make sure that our findings are based on the presented core data.
We will also carefully use your detailed comments to revise the manuscript and provide point-to-point answers and explanations of what we change. Yes, we can combine long and short core graphs to reduce the number of figures, and we can describe better our SR calculations using equations.
Please find our detailed answers in the revision note attached (5 pages PDF).
-
AC1: 'Author reply on RC1', Boris K. Biskaborn, 06 Mar 2023
-
RC2: 'Comment on egusphere-2022-985', Anonymous Referee #2, 14 Feb 2023
Comments on the manuscript entitled 'Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)' by Biskaborn et al.
This manuscript explores past environmental changes during the last 29k years based on diatom and geochemical records of a well-dated lake sediment core in Chukotka, which is a less investigated region. The results are interesting, particularly the relationships between diatom accumulation rates, organic carbon accumulation rates and mercury accumulation rates. I have one major concern on the driving force on diatom flora shifts (see details as follows). I suggest that this manuscript can be acceptable after major revions.
Major concern:
Although authors have provided potential driving forces for diatom flora shift, the mechanism is still ambiguous. The major trends in diatom flora are that an increase in benthic species during the early Holocene, and then the gradual replacement of benthic taxa by planktonic species. This general trend might be closely linked to temperature-driven changes in ice-cover period. For example, short ice-cover period in the early Holocene promote light penetration and the availability of littoral habitats.
In addition, effects of DOC on diatom flora should be considered during lake ontogeny since the deglaciation. DOC can be an important resilience against from external driving forces.
Some references might be useful
Engstrom, D. R., et al. (2000). "Chemical and biological trends during lake evolution in recently deglaciated terrain." Nature 408(6809): 161-166.
Hu, Z., et al. (2018). "The Landscape–Atmosphere Continuum Determines Ecological Change in Alpine Lakes of SE Tibet." Ecosystems 21(5): 839-851.
Chen, X., et al. (2018). "Direct and indirect effects of Holocene climate variations on catchment and lake processes of a treeline lake, SW China." Palaeogeography, Palaeoclimatology, Palaeoecology 502: 119-129.
Wischnewski, J., et al. (2011). "Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries." Global Change Biology 17(11): 3376-3391.I suggest that authors could clarify the major underlying driving forces of diatom flora shifts, specify the meanings of PC1 and PC2.
Other minor revisions:
1) L31-32: the responses to climate events are not very clear, probably due to low resolution of diatom records
2) L33-34: 'human-induced environmental change', please specify, atmospheric deposition?
3) L34-35:C/N ratios are generally larger than 10 during the Holocene, suggestive of the mixture of within lake production and terrestrial organic matter. Therefore, it should be cautious to draw this conclusion.
4) Section 2 Study site: Please provide more details on aquatic plants in this lake. Are there macrophytes or mosses around the lake shore? This is important to explain the development of benthic diatoms during the Holocene. In addition, water chemistry data should be provided, such as pH, conductivity, and dissolved organic carbon,
5) Section 3.5 Data processing and statistics: L 173, generally, square-root transformation of percentage data were used in CONISS, please check. In addition, the number of zones should be tested by the broken stick model (Bennett, 1996).
Bennett, K. D. (1996). "Determination of the number of zones in a biostratigraphical sequence." New Phytologist 132(1): 155-170.6) L243-246, please check the units of DVC and DAR, superscript should be used.
7) L330-331: thick ice due to long ice-cover period probably reduces light penetration?
8) L339-340: more detailed explanation for the linkage between diatom flora shift and climate. During this stage, the major change is the disappearance of Linvidavia bodanica and L. cyclopuncta
9) L354-355: rising alkalinity might be linked to enhanced chemical weathering intensity of bare rocks under warmer and wetter climate during the early and mid-Holocene
10) L371: the influx of melted water during the spring and summer probably increase the mixing?
11) L396: Here, potential effects of nitrogen deposition?
12) L488-489: prolonged ice-free period increases the availability of littoral habitats
13) Figure 7: legends for the two figures are needed, depths can be changed to 'ages'
14) Figure 8: for the total percentage of light Lindavia, L. bodanica might be different from other species, since this taxon has relatively heavy valves, which are similar to some Aulacoseira species (see the review by Saros and Anderson, 2015, The ecology of the planktonic diatom Cyclotella and its implications for global environmental change studies).
Citation: https://doi.org/10.5194/egusphere-2022-985-RC2 -
AC2: 'Reply on RC2', Boris K. Biskaborn, 06 Mar 2023
Dear Reviewer #2
Thank you very much for taking your time to review the manuscript. We are grateful for the comments you provided to ecology and environmental interpretation of diatom community shifts. We find that your comments on the increase of benthic species in course of changing ice cover period in the Early Holocene fits well into our discussion that was focused mainly on stratification before. We are also grateful for the valuable hints on DOC effects on diatoms during lake ontogeny parallel to deglaciation processes. We will carefully consider the list of additional papers you provided to make sure our discussion on diatom assemblage responses is based on state-of-the art relevant literature. We also will make sure that the revised discussion of underlying driving forces of diatom shifts is in accord with the PCA results as you suggested.
Please find our detailed answers in the revision note attached (6 pages PDF).
With best regards,
on behalf of all authors
Boris Biskaborn
-
AC2: 'Reply on RC2', Boris K. Biskaborn, 06 Mar 2023
Peer review completion
Journal article(s) based on this preprint
Data sets
Sedimentological and biogeochemical dataset for Arctic glacial lake Rauchuagytgyn, Chukotka, Russia Vyse, Stuart Andrew; Herzschuh, Ulrike; Pfalz, Gregor; Diekmann, Bernhard; Nowaczyk, Norbert R; Pestryakova, Luidmila A; Biskaborn, Boris K https://doi.pangaea.de/10.1594/PANGAEA.929719
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Cited
1 citations as recorded by crossref.
Boris K. Biskaborn
Amy Forster
Gregor Pfalz
Lyudmila A. Pestryakova
Kathleen Stoof-Leichsenring
Jens Strauss
Tim Kröger
Ulrike Herzschuh
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(15041 KB) - Metadata XML