the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Mar 2026
Invertebrate communities on seasonal snow patches in the European lowlands are shaped by tree canopy-derived organic inputs
Abstract. The cryosphere encompasses a wide range of habitats that support cold-adapted communities. Seasonal snow patches (SSPs) in lowlands are underexplored cryohabitats, characterized by a short persistence period (late winter–early spring) and the presence of trees around, in contrast to large vegetation-free high-mountain and polar ecosystems. To provide the first assessment of organisms from SSPs, we focused on invertebrate diversity and densities from 40 sites in the Baltic States in relation to physicochemical parameters (i.e., suspended solids, chlorophyll a, nutrients), microalgae, and surrounding landscape features (i.e., tree canopy cover). SSPs appeared to be an important spot for bdelloid rotifers (Bdelloidea), tardigrades (Tardigrada), and nematodes (Nematoda), which together accounted for 60–100 % of all invertebrates, reaching densities >7,000 ind∙m-2. Acari and Insecta were less abundant, whereas other invertebrates occurred only sporadically. The community was strongly determined by surroundings (trees), which supply snow ecosystems with organic and inorganic matter. Chlorophyll a, particulate phosphorus, total suspended solids and organic debris were strongest predictors of invertebrate distribution. The canopy cover also influenced invertebrate communities, highlighting the importance of the organic deposition from trees and also suggesting that trees may be a source of microscopic invertebrates to the snow. Results demonstrate the importance of SSPs as overlooked ephemeral habitats and can be used as a baseline for future changes in snow communities in temperate regions.
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Status: open (until 21 Apr 2026)
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RC1: 'Comment on egusphere-2026-1173', Anonymous Referee #1, 13 Mar 2026
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The authors present an in-depth analysis of invertebrate fauna that inhabit transient snow patches located throughout lowland areas in Baltic States. Collections were systematic and incorporated physiochemical parameters, data was analyzed with appropriate statistical methods, text is clear/organized, and conclusions are mostly reasonable with respect to the dataset. Nonetheless, the following points should be addressed:
- Figure legends need to stand alone from the text, currently they do not provide enough information (particularly Fig. 6, which is complex and needs to include qualitative information for context).
- Is it possible that monogononts were overlooked? These often co-occur with bdelloids in cold environments but can be misclassified as protists due to their small size.
- The interaction/contribution of the underlying soil is not considered. It seems that in recurring years there will be large depositions of invertebrates into the soil once the snow has melted. Is there any data available that compares invertebrate composition/density in underlying soil from a snow patch vs. other soil areas? Also, is it possible that the underlying soil is a major contributor to the invertebrates that appear each year in seasonal snow, instead of them being deposited from the peripheral surroundings, as suggested?
- What is the evidence that these invertebrates are reproducing in the snow? Could it be that reproduction occurs without snow and they are just tolerating the snow conditions?
- Can anything be said about the diversity of species within each phylum? Are these mostly the same species of rotifers, tardigrades, nematodes, etc or is there notable biodiversity within phyla? Are these species different from those which inhabit glacial ecosystems? I understand there is no molecular data, but some morphological characters would give a sense of species diversity within phyla.
- Is there any evidence that these snow invertebrates are more similar to glacial or soil counterparts?
Minor comments:Line 71: is --> wasLine 74: onto --> onLine 78: for understanding the SSPsLine 117: Figure 1 legend needs more information (e.g., cross-reference numbers to Table with coordinates)Line 138: Figure 2 legend needs more detailsLine 173: “...contents of tubes were slowly refrozen at +5 –...” do you mean “unfrozen” or “thawed”?Line 189: canopies --> canopyLine 379: is --> wasLine 446: characterized “to” be…471: in Figure 6ReplyCitation: https://doi.org/10.5194/egusphere-2026-1173-RC1 -
AC2: 'Reply on RC1', Dzmitry Lukashanets, 17 Apr 2026
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Thank you for comments provided.
Please find here the answers on comments:
- Figure legends need to stand alone from the text, currently they do not provide enough information (particularly Fig. 6, which is complex and needs to include qualitative information for context).
Response: Changed, the revised version for Figure 6 legend is:
Fig. 6. Distance-based redundancy analysis (tbRDA) showing relationships between invertebrate taxa (response variables, red arrows) and environmental variables (explanatory variables, black arrows; see Table 1). The direction of arrows indicate the direction of relationships: angles between arrows reflect correlations among variables, with smaller angles indicating positive relationships and opposite directions indicating negative relationships. Solid black arrows indicate environmental variables that significantly explain variation in community composition (Monte Carlo permutation test, p < 0.05), dashed arrows represent non-significant variables (p > 0.05). Sites (n = 32) are shown as grey numbers. Response variables: Aca – Acari, Ara – Araneae, Col – Collembola, Ins – Insecta, Nem – Nematoda, Rot – Rotifera, Tar – Tardigrada; Explanatory variables: CC – canopy cover, CHA – chlorophyll a, CHL – Chlorophyceae biomass, CON – conductivity, CORG – organic carbon, CYA – Cyanophyceae biomass, DEN – tree density, DIS – distance to trees, OD – organic debris.
- Is it possible that monogononts were overlooked? These often co-occur with bdelloids in cold environments but can be misclassified as protists due to their small size.
Response: No, likelihood that monogonont rotifers were overlooked is extremely low. First author of the manuscript can identify rotifers, and all individuals were identified as bdelloids based on morphological characteristics. Even if they are not-active, their characteristic ‘tun’-shaped external view and ramate mastax were clearly distinguishable. Furthermore, this observation is consistent with our understanding of snow rotifer communities, which are thought to be colonized primarily from mosses and lichens (e.g., those growing on tree bark), habitats typically dominated by bdelloid rotifers.
- The interaction/contribution of the underlying soil is not considered. It seems that in recurring years there will be large depositions of invertebrates into the soil once the snow has melted. Is there any data available that compares invertebrate composition/density in underlying soil from a snow patch vs. other soil areas? Also, is it possible that the underlying soil is a major contributor to the invertebrates that appear each year in seasonal snow, instead of them being deposited from the peripheral surroundings, as suggested?
Response: We fully agree that the potential contribution of the underlying soil was not explicitly considered in this study. However, our aim was not to determine the source(s) of microfauna present on snow surfaces, as these are likely to be multiple and interacting. Instead, we focused on identifying the key environmental variables that explain variation in invertebrate community composition.
In the article, we initially considered the SSPs as habitats influenced by their most visible and closest context, which are trees (since almost all SSPs were located in sheltered places in forest). All sampled SSPs were covered by organic debris indicating the great influence of trees on snow surface. This interpretation is further supported by our statistical analyses, which highlighted the importance of variables associated with this close surrounding.
To accept the idea that snow ecosystem can be influenced by soil, we have to assume that soil particles can be transported from the soil surface through entire snow column (up to 30 cm in some cases) and then be deposited on the surface where microfauna lives. It appears less likely compared to downward deposition processes.
Regarding the source of microfauna itself – we agree that multiple pathways are possible, and we intentionally avoid making conclusions on this aspect. However, active upward migration of rotifers and tardigrades from the soil through the snow to the surface seems unlikely. In contrast, deposition from above represents a more plausible mechanism. Conversely, the deposition of microfauna from melting snow into the underlying soil, as suggested by the reviewer, is indeed possible but falls beyond the scope of the present study and would require targeted studies.
- What is the evidence that these invertebrates are reproducing in the snow? Could it be that reproduction occurs without snow and they are just tolerating the snow conditions?
Response: We made this suggestion basing mostly on numbers of microscopic invertebrates – for example, in case of thousands of all three main groups at one spot. Please note that these habitats are short-living. Given this, it appears unlikely that such densities could be explained solely by sporadic inputs of individual organisms. However, we absolutely agree that ability to reproduce should be tested experimentally, hence our interpretation, potentially explaining the large presence of microfauna on snow surface, remains hypothetical. However, we do not claim that reproduction is restricted to snow environments; rather, we suggest that snow is inhabited by ‘normal’ microfauna which representatives may be capable of both surviving and potentially reproducing. And this assumption explains the observation we made. Importantly, this was not used as a basis for any formal hypothesis in the manuscript. We fully understand that other mechanisms also can work, at least partially.
- Can anything be said about the diversity of species within each phylum? Are these mostly the same species of rotifers, tardigrades, nematodes, etc or is there notable biodiversity within phyla? Are these species different from those which inhabit glacial ecosystems? I understand there is no molecular data, but some morphological characters would give a sense of species diversity within phyla.
Response: Yes, the molecular studies aimed to reveal the species composition in snow patches and in the surroundings (mosses, lichens nearby) are still in process. However, based on preliminary morphological examination, some initial conclusions can be drawn. Both rotifers and tardigrades found in snow appear to belong to common, European taxa, particularly rotifers typical of limno-terrestrial environments. So far, no glacial (polar, Arctic, etc.) species have been identified. However, there is only partial overlap between species found in snow and those in the immediate surroundings. We found some rare rotifer species (previously recorded in Europe but not considered common). These results are still preliminary and have to be supported using molecular approach, which supposed to be another study (focused on diversity and connectivity with other types of cryosphere). Regarding other groups – unfortunately, the specialists in nematodes and arthropods were not involved ; therefore, we refrain from further interpretation for these taxa.
- Is there any evidence that these snow invertebrates are more similar to glacial or soil counterparts?
Response: Please, see above. In general – we did not observe similarities of SSP fauna with the glacial one.
Minor comments:
Line 71: is --> was
Line 74: onto --> on
Line 78: for understanding the SSPs
Line 117: Figure 1 legend needs more information (e.g., cross-reference numbers to Table with coordinates)
Line 138: Figure 2 legend needs more details
Line 173: “...contents of tubes were slowly refrozen at +5 –...” do you mean “unfrozen” or “thawed”?
Line 189: canopies --> canopy
Line 379: is --> was
Line 446: characterized “to” be…
471: in Figure 6
Response: All comments were considered, and appropriate changes were made.
New legends for figures 1 and 2:
Fig. 1. Locations of sampling sites ## 1–40 in Lithuania, Latvia, and Estonia in 2023–2024 (a); SSPs at sampling sites # 11 (b), # 20 (c), and # 36 (d). For coordinates of sampling sites, see Table S1
Fig. 2. Sampling sites # 16 (a), # 22 (b), and # 36 (c) representing different levels of canopy cover: 5 %, 24 %, and 58 %, respectively. For coordinates of sampling sites, see Table S1
Citation: https://doi.org/10.5194/egusphere-2026-1173-AC2
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RC2: 'Comment on egusphere-2026-1173', Dorota L. Porazinska, 10 Apr 2026
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This manuscript is very well written, with novel questions posed, and appropriate methods used. The results are well presented and discussed. It was a pleasure to review this work.
Citation: https://doi.org/10.5194/egusphere-2026-1173-RC2 -
AC1: 'Reply on RC2', Dzmitry Lukashanets, 17 Apr 2026
reply
Thank you so much
Citation: https://doi.org/10.5194/egusphere-2026-1173-AC1
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AC1: 'Reply on RC2', Dzmitry Lukashanets, 17 Apr 2026
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RC3: 'Comment on egusphere-2026-1173', Anonymous Referee #3, 20 Apr 2026
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General comment:The paper by Lukashanets et al., submitted to BG, focuses on the overlooked habitat of lowland snowfields and their invertebrate communities. This interesting and novel study identifies invertebrates via morphology and examines correlations between their distribution, snow chemistry, habitat characteristics, and algal biomass.
Specific comments:
line 34: Snowfields in general receive much attention, but here authors should rather specify the uniqueness of their research in having a look on "snowfields and snow patches in LOWLANDS" (of course not in capital letters)
line 123: Great that only the upper layer of snow was harvested. This may be due to the avoidance of the snow-soil interface. This is according to the best practice to collect "true" (autochthonous) algae and avoid soil algae as it is shown in Fig. S2 in Lutz et al. 2018.
Stefanie Lutz, Lenka Procházková, Liane G. Benning, Linda Nedbalová & Daniel Remias (2019): Evaluating amplicon high–throughput sequencing data of microalgae living in melting snow: improvements and limitations. Fottea , 19(2), 115-131. DOI: 10.5507/fot.2019.003
However, the authors of the paper under review collected the uppermost layer of snow, so the airborne algae were most likely part of the sampled snow.
line 123 - Was the depth of the sampled snowfield measured before sampling? Or the snow cover was always much thicker than 4 cm, making it possible to safely avoid any sampling of the soil to snow interface?
line 163-165: Could the authors briefly describe the protocol for microalgae enumeration in the Utermöhl chamber according to HELCOM guidelines? For instance, what was the minimum number of cells counted per species? Furthermore, how many cells of each species were measured to determine the mean cell volume?
Line 218-220 It would be appreciated if the authors could also include algal cell abundances in the manuscript, rather than only biomass levels. This would facilitate comparison with existing literature on Chloromonas snow algae, such as e.g. in Procházková et al. (2020). I assume the abundance was lower than 10,000 cells/ml, as the sampled snow patches did not appear to show any visible snow algal discoloration (if I understood correctly).
Lenka Procházková , Daniel Remias, Wolfgang Bilger, Heda Křížková, Tomáš Řezanka, Linda Nedbalová (2020): Cysts of the Snow Alga Chloromonas krienitzii (Chlorophyceae) Show Increased Tolerance to Ultraviolet Radiation and Elevated Visible Light. Frontiers in Plant Science 11: 617250. DOI: 10.3389/fpls.2020.617250
line 305 - In which order the sites are shown? Sample number? The authors shall specify that density of animals is shown by grey bar chart (it is currently not clear on the first sign). What about showing an alternative figure of animal density in relation to chlorophyll-a?
line 272 - 273 - The results of the analysis is regarded by the authors as "weak positive correlation" if Rs=0.48 while on the lines 349-350 it is regarded by the authors as "moderate positive correlation" if Rs=0.38, Rs=0.46 and Rs=0.39. This is a bit inconsistent, especially if the common interpretation scale of Spearman Correlation coefficient is the following: weak for 0.20 – 0.39, moderate for 0.40 – 0.59.
line 436: in this study, I wonder, were there sampled any visible colored snow patches (due to snow algal blooms)? If not, it is better to mention this detail here or in the methods clearly.
line 483- 484 - The authors suggest that rotifers primarily originated from the surrounding trees. However, the images in Fig. 1b-d suggest that the sampled snowfields were quite shallow. Although the manuscript does not specify the total depth of the snow patches (noting only that the uppermost 2-4 cm were collected), is it possible to entirely exclude the possibility that the detected rotifers also originated from the soil beneath these shallow snowfields?Citation: https://doi.org/10.5194/egusphere-2026-1173-RC3
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