the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 May 2024
The diel vertical migration of microbes within snowpacks driven by solar radiation and nutrients
Abstract. Seasonal snowpacks are inhabited by various microbes despite their ephemeral and cold environments. Physicochemical conditions in snowpacks drastically change with day-night cycles; however, their effect on the microbial community is largely unknown. This study describes the diel vertical migration (DVM) of microbes within a snowpack in an alpine forest in northern Japan. Microscopy revealed the presence of snow algae, microinvertebrates, and fungi in the snowpack. Periodic sampling across snow depths revealed that the vertical distribution of microbes changed over time. Motile cells of snow algae and microinvertebrates were distributed near the surface at night but migrated to a depth of 10–20 cm during the day. Other microbes, including algal spores and fungi, remained on the surface layer throughout the day. The vertical migration of microbes was synchronized with the intensity of solar radiation, suggesting that the microbes moved downward to avoid intense solar radiation on the snow surface. Soluble nutrients (PO43-, NH4+, and K+) were always the highest at the snow surface, suggesting that surface snow provides a favorable environment for microbial growth. These results indicate that motile microbes migrate diurnally within the snowpack to remain under the best conditions for their growth in terms of the intensity of solar radiation and nutrients. Snow core sampling from the surface to bottom revealed that microbes were mostly present above a depth of 30 cm in the snowpack. Therefore, the upper snow layer above this depth, referred to as the Microbial Active Snow Surface (MASS) layer, is important for the life cycles of microbes and biogeochemical cycles within snowpacks.
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RC1: 'Comment on egusphere-2024-1193', Anonymous Referee #1, 11 Jul 2024
The results presented in this study provide significant insights into snow algae blooms and their associated communities. The meticulous effort invested in sampling, separating, and analyzing various microorganisms under the microscope throughout a 24-hour cycle is commendable and underscores the study's value. It's important to acknowledge the inherent challenges of field studies, as opposed to laboratory experiments where there is much control of what is happening, which should be considered when evaluating this research.
However, the study of these communities is conditionate by how these blooms occur in nature, making it impossible to sample the same community twice given their patchy distribution. This entails a series of limitations when planning the experiment and drawing up conclusions that should be considered.
My primary concerns are:
-As the results are presented, the observed differences could be due to vertical movements in the community because of changes in temperature and radiation, but they could also be due to their heterogeneous distribution (on the surface and along the vertical profile). As an example of the patchy distribution, there are differences if we add total chl-a along the vertical profile for the two days at 2:00 AM (30% difference between days), which gives an idea that the same community is not being compared even if it has been sampled in almost the same place. It is not clear to me the methodology used for sample collection, whether the heterogeneity of these communities was considered, or if the variability observed at each time point reflects the variability within the snowpatch. A more thorough explanation of the methods would be beneficial.
-Differences, between days, in the vertical distribution of chl-a observed in the 02:00 AM samples (with maximum concentrations in the lower layer vs to the surface, respectively), suggest that extending the study over a longer period might lead to, perhaps, different conclusions. This indicates that additional sampling may be needed to model vertical movements within a snow patch, and this could be an initial observation of such movements. This aspect deserves more thoughtful consideration in drawing the conclusions.
-Another point to consider, is that algae are classified into motile and non-motile categories, and conclusions are drawn based on this classification. However, this study does not provide evidence for their motility. While it is assumed that these organisms demonstrate active movement, no motility structures were identified through the extensive microscopic observation of the algae. It would be necessary for the authors to further explore this in the discussion.
-An important aspect for this study is understanding the properties of the snow, which have not been analysed throughout the vertical profile. The snowpack conditions are crucial for explaining potential movements of microorganisms or defining a microbial active snow surface (MASS) layer. If data such as temperature and water content along this vertical profile have not been measured, the authors should provide evidence demonstrating that all samples exhibit uniform conditions and, for example, there is no ice layer restricting some of these vertical movements.
If the editor finds it acceptable to proceed with publication despite what was mentioned above, I will fully support its publication. However, it should be noted that some conclusions presented in this work may me reconsidered.
Find more specific comments on the manuscript below:
Ln1. Title: The presented data is insufficient to substantiate this claim. Nutrient levels at 15cm might provide adequate conditions for algae to thrive, potentially not influencing their vertical movements. Please consider modifying the title accordingly.
Ln 37-38. The use of degrees Kelvin in a study like this seemed unusual to me. To make it more universal, I would recommend changing the units to Celsius.
Ln 98-102. Do the authors have information on the slope, water content, and temperature in the snow?
Ln 105. How did the authors decide where to take the samples?
I expect there's significant variability in the presence of algae across both the surface and vertical profile of the snow patch. This suggests that differences in the vertical distribution of the community were already present at the beginning of the experiment, under identical radiation and temperature conditions.
Ln 115. There appears to be an ice layer below 18 cm that could potentially disrupt the vertical movement of microbial communities. I'm concerned the presence and variability in ice layer depth across the snowpatch could impact some of the conclusions of this study. Including photos of each sample would greatly clarify whether the ice is affecting the vertical flow.
Ln 130. Why did the authors choose not to filter/process the samples before freezing them? Freezing samples before processing can alter the nutrients present, potentially lysing millions of bacteria and resulting in a misunderstanding of the actual conditions in the snow. This consideration should be acknowledged in the discussion.
Ln 136. From the photos, it seems there is accumulated tree biomass on the snow patch surface. Was this biomass removed before aliquoting the samples? If not, it might have heightened surface chlorophyll levels. If it was removed, how was this process carried out? This could be a significant source of microfauna.
Ln 187. Could these be different species? Even if they are the same species, would it be worthwhile to analyse them separetly within the vertical profile? Variations in size like this might indicate differing abilities for vertical movement.
Ln 195. It would be interesting to include images of both species of tardigrades to offer a clearer description of the community.
Ln 232. It seems that this section its already included in the title of the previous section. Please delete this section or modify the title of the preceding section.
Ln 246. Could be associated to the different species?
Ln 276. This is very cool and provides valuable information for better understanding the dynamics of these communities. It appears that the green snow patch never reached the color intensity seen the first time...
Ln 290. Did the authors detect any motility structures in this group of cells that would better support this assumption?
Ln 293. Dormant cell or a cell in a state prior to dormancy?
Ln 305. Were the cells found in aggregates or individually? This could explain why they are not washed from the surface.
Ln 312. Could it be that meltwater washes the algae cells and that they actively return to the surface when melt rates decrease due to changes in radiation? Type C may be producing exopolysaccharides that allow the formation of larger groups of cells that limit their vertical movement
Ln 329. The water content in the snow and the presence of ice layers are likely crucial factors for explaining the vertical movement of microorganisms.
Ln 358. Did the authors see differences in the distribution of the two species of tardigrades along the vertical profile?
Ln 365. As previously mentioned, could it be that the meltwater is washing them downward?
Ln 369. My concern is that an ice layer might be causing this difference. Since all the samples were collected from the same snow patch, which has a similar slope, this ice layer could be present throughout the entire area. Thus, this could imply that without an ice layer, there are no barriers to vertical movement, making it unnecessary to discuss a microbial active snow surface layer.
Ln 391. Please consider revising the conclusions based on the earlier suggestions.
Figure 7. It may be a good idea presenting the vertical profiles of NH4, PO4, and K in the first row, as they share a similar profile distinct from the others.
Citation: https://doi.org/10.5194/egusphere-2024-1193-RC1 - AC2: 'Reply on RC1', Masato Ono, 01 Aug 2024
-
RC2: 'Comment on egusphere-2024-1193', Anonymous Referee #2, 14 Jul 2024
The manuscript by Ono et al., presents interesting data on the vertical distribution and dispersal of algae and microscopic invertebrates in the snow patches. Snow ecosystems are poorly known in general, therefore each piece of data on the algae and their consumers are crucial. Although interesting, manuscript cannot be accepted in the present form. Manuscript require corrections and changes of the tone in the interpretation of the results. I like the idea of MASS and in my opinion the idea makes sense, at least for algae and invertebrates. However, without some clarifications (e.g. sampling) the evaluation of the data robustness is difficult.
Few general comments:
- I would mute the tone of the results and discussion. The studies were conducted in the Japanese forests, on the mountain slope in the specific insular climate, it is hard to extrapolate these data to other snow ecosystems. It will be better to highlight in many places that results are valid for Japan. Therefore, I support the importance of the findings but some sentences are overstated.
- Could you compare radiation in the forests and open landscape? I’m not convinced that UV could be explanation of the migration in the forests (even without leafes trees offer sort of protection).
- I would be happy to see discussion on the another option/reason of migration between snow layers. I would expect that predators (e.g. springtails) could impact on the migration; preys avoid predators (birds and ice worms on the North American glaciers are a good example of such relation).
- it is not clear, how many cores were collected at each spot? One core = one sample. What about subsamples = layers? what about replicates = sampling of the same layers?
- How many cores? How many pits?
- Why algae were not identified to genus or family level? Even though many snow algae are morphological species complexes, still their identification at higher taxonomic level is possible.
- Why authors did not use the best predictor (e.g. by PCA approach), then focus on the analysis involving the most important variables.
- Im not sure that tardigrades are migrating between layers. It seems they are splitting from one big group into upper and lower groups. It could be accidental?
- Finally, I miss basic data on the general dispersal features of algae and micorinvertebrates. Do we know what is the avarege distance the target organisms can disperse withing specific time? At least any basic data could help in the convincing reviewers to observed dispersal.Abstract:
I suggest to higlight that percolation do not impact the results.Introduction:
Line 26: i.a. tardigrades and rotifers
Line 27: add reference
Line 30: tropically? typo
Line 37: use one unit (C or K)
Lines 45: can author say mating in terms of algae?
Line 64: reference is missingRezults:
Line 193: not genera. Phyla.
Line 195: specimens instead of species
Figure 4: add names of higher taxonomic levels before names of species, for example Tardigrade Hypsibius spp.
219: 26:00??
Figure 5: For tardigrades, rotifers and fungi the names of axis are missing.Citation: https://doi.org/10.5194/egusphere-2024-1193-RC2 -
AC3: 'Reply on RC2', Masato Ono, 01 Aug 2024
Dear Editor and Reviewer#1,
Please see attached our reply to the review comments.Sincerely,
Masato Ono and co-authors-
AC4: 'Reply on AC3', Masato Ono, 03 Aug 2024
We apologized that we sent wrong addressee name. The correct addressee name is “Dear Editor and Reviewer #2,”.
Citation: https://doi.org/10.5194/egusphere-2024-1193-AC4
-
AC4: 'Reply on AC3', Masato Ono, 03 Aug 2024
-
AC3: 'Reply on RC2', Masato Ono, 01 Aug 2024
-
EC1: 'Editor's recommendation', Florent Dominé, 17 Jul 2024
Dear Authors,
The Reviewers have made a number of valuable remarks and recommendations that need to be addressed in detail in your response before a revised version is uploaded.
In general, Reviewers note the lack of data specific to the sampling protocol and sampling conditions. In particular, details on snow conditions would be desirable. Do you have any data on the temperature profile and/or the liquid water content in the snowpack? Your Figure 3 suggests the snowpack may have been ripe, i.e., isothermal at 0°C and melting. If none of the required data are available, at least air temperature and radiation data for the past few days may help estimate whether the snowpack may have been ripe or not. Also, regarding snow data, the presence of ice layers is important as clearly this affects migration. Any notes on this aspect?
The issue of spatial variability and representativity of your samples is also important. The small size of your data set can indeed be an issue for the validity of your conclusion. Perhaps you have obtained additional data in spring 2024 that could strengthen your paper?
Lastly, details on your protocol, that would strengthen the validity of your conclusions, are objections that you should address in detail.
In summary, your study is original and interesting. I am however worried about the size of your data set and also the lack of details given on non-microbial aspects, which limits the strength of your interpretation. The Reviewers furthermore make a number of requests concerning additional details on the microbial aspects.
I will need to read your responses to each of the Reviewers’ comments before I can decide whether a revised version will be considered.
Best regards,
Florent Domine
Citation: https://doi.org/10.5194/egusphere-2024-1193-EC1 - AC1: 'Reply on EC1', Masato Ono, 01 Aug 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-1193', Anonymous Referee #1, 11 Jul 2024
The results presented in this study provide significant insights into snow algae blooms and their associated communities. The meticulous effort invested in sampling, separating, and analyzing various microorganisms under the microscope throughout a 24-hour cycle is commendable and underscores the study's value. It's important to acknowledge the inherent challenges of field studies, as opposed to laboratory experiments where there is much control of what is happening, which should be considered when evaluating this research.
However, the study of these communities is conditionate by how these blooms occur in nature, making it impossible to sample the same community twice given their patchy distribution. This entails a series of limitations when planning the experiment and drawing up conclusions that should be considered.
My primary concerns are:
-As the results are presented, the observed differences could be due to vertical movements in the community because of changes in temperature and radiation, but they could also be due to their heterogeneous distribution (on the surface and along the vertical profile). As an example of the patchy distribution, there are differences if we add total chl-a along the vertical profile for the two days at 2:00 AM (30% difference between days), which gives an idea that the same community is not being compared even if it has been sampled in almost the same place. It is not clear to me the methodology used for sample collection, whether the heterogeneity of these communities was considered, or if the variability observed at each time point reflects the variability within the snowpatch. A more thorough explanation of the methods would be beneficial.
-Differences, between days, in the vertical distribution of chl-a observed in the 02:00 AM samples (with maximum concentrations in the lower layer vs to the surface, respectively), suggest that extending the study over a longer period might lead to, perhaps, different conclusions. This indicates that additional sampling may be needed to model vertical movements within a snow patch, and this could be an initial observation of such movements. This aspect deserves more thoughtful consideration in drawing the conclusions.
-Another point to consider, is that algae are classified into motile and non-motile categories, and conclusions are drawn based on this classification. However, this study does not provide evidence for their motility. While it is assumed that these organisms demonstrate active movement, no motility structures were identified through the extensive microscopic observation of the algae. It would be necessary for the authors to further explore this in the discussion.
-An important aspect for this study is understanding the properties of the snow, which have not been analysed throughout the vertical profile. The snowpack conditions are crucial for explaining potential movements of microorganisms or defining a microbial active snow surface (MASS) layer. If data such as temperature and water content along this vertical profile have not been measured, the authors should provide evidence demonstrating that all samples exhibit uniform conditions and, for example, there is no ice layer restricting some of these vertical movements.
If the editor finds it acceptable to proceed with publication despite what was mentioned above, I will fully support its publication. However, it should be noted that some conclusions presented in this work may me reconsidered.
Find more specific comments on the manuscript below:
Ln1. Title: The presented data is insufficient to substantiate this claim. Nutrient levels at 15cm might provide adequate conditions for algae to thrive, potentially not influencing their vertical movements. Please consider modifying the title accordingly.
Ln 37-38. The use of degrees Kelvin in a study like this seemed unusual to me. To make it more universal, I would recommend changing the units to Celsius.
Ln 98-102. Do the authors have information on the slope, water content, and temperature in the snow?
Ln 105. How did the authors decide where to take the samples?
I expect there's significant variability in the presence of algae across both the surface and vertical profile of the snow patch. This suggests that differences in the vertical distribution of the community were already present at the beginning of the experiment, under identical radiation and temperature conditions.
Ln 115. There appears to be an ice layer below 18 cm that could potentially disrupt the vertical movement of microbial communities. I'm concerned the presence and variability in ice layer depth across the snowpatch could impact some of the conclusions of this study. Including photos of each sample would greatly clarify whether the ice is affecting the vertical flow.
Ln 130. Why did the authors choose not to filter/process the samples before freezing them? Freezing samples before processing can alter the nutrients present, potentially lysing millions of bacteria and resulting in a misunderstanding of the actual conditions in the snow. This consideration should be acknowledged in the discussion.
Ln 136. From the photos, it seems there is accumulated tree biomass on the snow patch surface. Was this biomass removed before aliquoting the samples? If not, it might have heightened surface chlorophyll levels. If it was removed, how was this process carried out? This could be a significant source of microfauna.
Ln 187. Could these be different species? Even if they are the same species, would it be worthwhile to analyse them separetly within the vertical profile? Variations in size like this might indicate differing abilities for vertical movement.
Ln 195. It would be interesting to include images of both species of tardigrades to offer a clearer description of the community.
Ln 232. It seems that this section its already included in the title of the previous section. Please delete this section or modify the title of the preceding section.
Ln 246. Could be associated to the different species?
Ln 276. This is very cool and provides valuable information for better understanding the dynamics of these communities. It appears that the green snow patch never reached the color intensity seen the first time...
Ln 290. Did the authors detect any motility structures in this group of cells that would better support this assumption?
Ln 293. Dormant cell or a cell in a state prior to dormancy?
Ln 305. Were the cells found in aggregates or individually? This could explain why they are not washed from the surface.
Ln 312. Could it be that meltwater washes the algae cells and that they actively return to the surface when melt rates decrease due to changes in radiation? Type C may be producing exopolysaccharides that allow the formation of larger groups of cells that limit their vertical movement
Ln 329. The water content in the snow and the presence of ice layers are likely crucial factors for explaining the vertical movement of microorganisms.
Ln 358. Did the authors see differences in the distribution of the two species of tardigrades along the vertical profile?
Ln 365. As previously mentioned, could it be that the meltwater is washing them downward?
Ln 369. My concern is that an ice layer might be causing this difference. Since all the samples were collected from the same snow patch, which has a similar slope, this ice layer could be present throughout the entire area. Thus, this could imply that without an ice layer, there are no barriers to vertical movement, making it unnecessary to discuss a microbial active snow surface layer.
Ln 391. Please consider revising the conclusions based on the earlier suggestions.
Figure 7. It may be a good idea presenting the vertical profiles of NH4, PO4, and K in the first row, as they share a similar profile distinct from the others.
Citation: https://doi.org/10.5194/egusphere-2024-1193-RC1 - AC2: 'Reply on RC1', Masato Ono, 01 Aug 2024
-
RC2: 'Comment on egusphere-2024-1193', Anonymous Referee #2, 14 Jul 2024
The manuscript by Ono et al., presents interesting data on the vertical distribution and dispersal of algae and microscopic invertebrates in the snow patches. Snow ecosystems are poorly known in general, therefore each piece of data on the algae and their consumers are crucial. Although interesting, manuscript cannot be accepted in the present form. Manuscript require corrections and changes of the tone in the interpretation of the results. I like the idea of MASS and in my opinion the idea makes sense, at least for algae and invertebrates. However, without some clarifications (e.g. sampling) the evaluation of the data robustness is difficult.
Few general comments:
- I would mute the tone of the results and discussion. The studies were conducted in the Japanese forests, on the mountain slope in the specific insular climate, it is hard to extrapolate these data to other snow ecosystems. It will be better to highlight in many places that results are valid for Japan. Therefore, I support the importance of the findings but some sentences are overstated.
- Could you compare radiation in the forests and open landscape? I’m not convinced that UV could be explanation of the migration in the forests (even without leafes trees offer sort of protection).
- I would be happy to see discussion on the another option/reason of migration between snow layers. I would expect that predators (e.g. springtails) could impact on the migration; preys avoid predators (birds and ice worms on the North American glaciers are a good example of such relation).
- it is not clear, how many cores were collected at each spot? One core = one sample. What about subsamples = layers? what about replicates = sampling of the same layers?
- How many cores? How many pits?
- Why algae were not identified to genus or family level? Even though many snow algae are morphological species complexes, still their identification at higher taxonomic level is possible.
- Why authors did not use the best predictor (e.g. by PCA approach), then focus on the analysis involving the most important variables.
- Im not sure that tardigrades are migrating between layers. It seems they are splitting from one big group into upper and lower groups. It could be accidental?
- Finally, I miss basic data on the general dispersal features of algae and micorinvertebrates. Do we know what is the avarege distance the target organisms can disperse withing specific time? At least any basic data could help in the convincing reviewers to observed dispersal.Abstract:
I suggest to higlight that percolation do not impact the results.Introduction:
Line 26: i.a. tardigrades and rotifers
Line 27: add reference
Line 30: tropically? typo
Line 37: use one unit (C or K)
Lines 45: can author say mating in terms of algae?
Line 64: reference is missingRezults:
Line 193: not genera. Phyla.
Line 195: specimens instead of species
Figure 4: add names of higher taxonomic levels before names of species, for example Tardigrade Hypsibius spp.
219: 26:00??
Figure 5: For tardigrades, rotifers and fungi the names of axis are missing.Citation: https://doi.org/10.5194/egusphere-2024-1193-RC2 -
AC3: 'Reply on RC2', Masato Ono, 01 Aug 2024
Dear Editor and Reviewer#1,
Please see attached our reply to the review comments.Sincerely,
Masato Ono and co-authors-
AC4: 'Reply on AC3', Masato Ono, 03 Aug 2024
We apologized that we sent wrong addressee name. The correct addressee name is “Dear Editor and Reviewer #2,”.
Citation: https://doi.org/10.5194/egusphere-2024-1193-AC4
-
AC4: 'Reply on AC3', Masato Ono, 03 Aug 2024
-
AC3: 'Reply on RC2', Masato Ono, 01 Aug 2024
-
EC1: 'Editor's recommendation', Florent Dominé, 17 Jul 2024
Dear Authors,
The Reviewers have made a number of valuable remarks and recommendations that need to be addressed in detail in your response before a revised version is uploaded.
In general, Reviewers note the lack of data specific to the sampling protocol and sampling conditions. In particular, details on snow conditions would be desirable. Do you have any data on the temperature profile and/or the liquid water content in the snowpack? Your Figure 3 suggests the snowpack may have been ripe, i.e., isothermal at 0°C and melting. If none of the required data are available, at least air temperature and radiation data for the past few days may help estimate whether the snowpack may have been ripe or not. Also, regarding snow data, the presence of ice layers is important as clearly this affects migration. Any notes on this aspect?
The issue of spatial variability and representativity of your samples is also important. The small size of your data set can indeed be an issue for the validity of your conclusion. Perhaps you have obtained additional data in spring 2024 that could strengthen your paper?
Lastly, details on your protocol, that would strengthen the validity of your conclusions, are objections that you should address in detail.
In summary, your study is original and interesting. I am however worried about the size of your data set and also the lack of details given on non-microbial aspects, which limits the strength of your interpretation. The Reviewers furthermore make a number of requests concerning additional details on the microbial aspects.
I will need to read your responses to each of the Reviewers’ comments before I can decide whether a revised version will be considered.
Best regards,
Florent Domine
Citation: https://doi.org/10.5194/egusphere-2024-1193-EC1 - AC1: 'Reply on EC1', Masato Ono, 01 Aug 2024
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