| 22 Jul 2026
Late Holocene evolution of a dystrophic Tatra Lake: natural trophic changes revealed by multi-proxy data
Abstract. Dystrophic lakes, characterized by dark-colored water, low transparency, and low pH, are relatively common in the mountainous and lowland regions of temperate and boreal zones. The occurrence of dystrophic conditions depends on hydrological, climatic, and biological factors, including surface and groundwater inflows and outflows, precipitation, air temperature, and vegetation within the lake's catchment. A change in any of these factors can lead to either an increase or a decrease in the degree of lake dystrophy. In this study, we present changes in the trophic status of a small forest lake located in the lower part of the Tatra Mountains (1,089 m a.s.l.; Western Carpathians, Poland). The lake is located within the Tatra National Park, and its natural dystrophic character is one of the features protected under the park's conservation objectives. We aimed to determine whether these dystrophic conditions are of natural origin and have persisted over a long period. To investigate this, we analysed a 1.4-m sediment core spanning the last 3,150 years using a range of geochemical and paleobiological methods, including elemental analysis, stable carbon and nitrogen isotope analyses, and analyses of diatom and Cladocera assemblages. Changes in the species composition of diatoms and Cladocera indicate that dystrophic conditions did not persist throughout the entire study period. The lake was dominated by species characteristic of meso-oligotrophic and oligotrophic water bodies, with only a brief period during which species indicative of dystrophic conditions appeared, coinciding with a low-water phase around 2700–2350 cal. yr BP. Permanent dystrophic conditions became established no earlier than approximately 950 cal. yr BP, which is relatively late compared with many lowland lakes.
General comments
The manuscript by Sienkiewicz et al. (DOI: 10.5194/egusphere-2026-4131) focuses on reconstructing the history of a dystrophic mountain lake. The authors have chosen a very interesting study site, and their results certainly deserve to be published. However, I believe that the manuscript requires substantial revisions before it can be accepted for publication in an international scientific journal.
In the Abstract and the Introduction, the authors should explain why it is important to study the history of the chosen study site (Toporowy Staw Niżni, abbr. TSN). Without such an explanation, the manuscript comes across as a study of purely local interest.
The Introduction section lacks information on mechanisms controlling brownification in mountain lakes. Conversely, the information about mixotrophic organisms of humic lakes—of which, in many cases, no subfossil remains are preserved in lake sediments—appears to be of little importance. The same section also lacks published examples of the evolution of dystrophic mountain lakes or lakes that were dystrophic in the past. As a result, studies presenting results of research projects with a similar focus are not cited sufficiently here (see, e.g., Tichá et al. 2023 showing a Holocene diatom record from a Central European humic lake). Also, some basic information on the use of stable isotopes (C, N) in research into the history of dystrophic lakes would be useful (in Discussion or Materials and methods).
Unfortunately, the authors have not convinced me that dystrophic conditions at the study site have existed only for the last ca. 1,000 years. The onset of dystrophication is usually linked to the development of peatland ecosystems within a (lake) catchment. In the catchment of the nearby lake Toporowy Staw Wiżni (TSW), this process likely started in the mid-Holocene (see Ucar et al. 2026). Diatom assemblage zones (DAZ) 1 and 2 do not indicate a clear absence of dystrophic conditions. Staurosira construens var. venter, Encyonema hebridicum, and Pinnularia microstauron—the most dominant diatom species in DAZ 1 and DAZ 2—are not typical diatoms of dystrophic lakes, but they are known to occur in some dystrophic lakes (e.g., Poenitz et al. 1995, Levkov et al. 2005, Kavková et al. 2022, Rantala et al. 2023). The absence of dystrophic conditions in DAZ 1 and DAZ 2 is also not supported by the high proportion of the cladoceran Alonella excisa (present in almost all sediment samples; relative abundance values between ca. 20–60% were observed in DAZ 1!). This species is very rare in oligotrophic (alpine) lakes in the Tatra Mountains (see Sacherová et al. 2006). The changes observed in diatom and cladoceran assemblages may, of course, indicate important environmental shifts (including shifts in DOC concentrations in the lake water), but these are likely took place in a lake which has always been, to some extent, dystrophic over the last three millennia.
For the reasons mentioned above, I recommend interpreting all results more critically (i.e., using a multi-proxy approach) and with reference to a wider range of published studies. Moreover, I suggest discussing the results in the light of published findings on Holocene vegetation changes in the Tatra Mountains.
I was surprised that the manuscript does not mention that Toporowy Staw Niżni is one of only two sites in Central Europe where the cladoceran Daphnia lacustris is known to occur (Nilssen et al. 2007, Petrusek et al. 2007, Hamrová et al. 2010). The second site is the nearby Toporowy Staw Wiżni (TSW). The cladoceran results presented are therefore of great value from a nature conservation perspective, as they also provide us with indirect (!) information about the history of this interesting species in the lake under study. Daphnia lacustris is considered a glacial relict species in the Tatra Mountains.
Specific comments
Lines 16-17: “Dystrophic lakes… are relatively common in the mountainous and lowland regions of temperate and boreal zones.“ – Are lakes of this type really common in the mountainous regions of temperate and boreal zones? If so, are they also common in Central European mountains? On the Polish side of the Tatra Mountains, there are only three such lakes... (see lines 70-72).
Lines 40-42: “Dystrophic lakes, classified as humic or brown, are typically small water bodies found in mountain and boreal regions with relatively cold, humid climates (Kankaala et al., 2006; Górniak, 2017).” – However, dystrophic lakes are also very common in tropical rainforests.
Lines 40-63: In the first paragraph of the Introduction section, the phytoplankton of dystrophic lakes is discussed. Why are other groups of organisms inhabiting the same type of lakes not mentioned in the same (or in the following) paragraph? In view of your results, it would be appropriate to comment at least on the zooplankton (or at least on Cladocera).
Line 45: “or have disappeared” – Could you be a bit more specific here? Why did these lakes disappear?
Lines 68-69: “many humic lakes existed in the Tatra Mountains in the past (Kapustka et al., 2018; Bitušík et al., 2024)” – How many? Tens? Hundreds? What was the approximate proportion of dystrophic lakes compared to other types of lakes in the Tatra Mountains? And what is that proportion today? I was unable to find this information in the articles by Kapustka et al. (2018) and Bitušík et al. (2024).
Lines 96-97: “comparable studies from mountain environments remain exceptionally rare (Bitušík et al., 2024).” – I disagree with this statement. Although comparative studies are not numerous, they are also not exceptionally rare. Here are some examples from Europe: Steinberg (1991), Gąsiorowski and Sienkiewicz (2010a), Tichá et al. (2023), Florescu et al. (2024), and Perret-Gentil et al. (2024). And here are two examples of non-European studies: Norton et al. (2011) and Mariani et al. (2018).
Lines 97-98: “Consequently, it is still unclear whether the mechanisms driving dystrophication and ecological succession in mountain lakes are similar to those described for lowland systems.” – What are the drivers of dystrophication/brownification in lowland dystrophic lakes? Why are different driving mechanisms expected in the case of mountain dystrophic lakes?
Section 2 (Study site): This section lacks information on the size of the TSN catchment area. Figure 1 shows that the TSN site is connected to the TSW site via a tributary. The TSW site and its history appear to be important for the interpretation of your results. See, e.g., Szarłowicz et al. (2022), Ucar et al. (2026) and references therein.
Section 3.1: What was the total sediment thickness measured at the coring site? 140 cm? Or is this parameter unknown because it has not been possible to obtain a complete sedimentary record from TSN?
Section 3.4.1: How many dystrophic lakes are included in the POL_SLOV training set? It seems that most of the sites in that training set are alpine lakes affected by anthropogenic acidification (see e.g. Supplementary information in Stuchlík et al. 2017).
Table 1: “Carex” → “Carex seed”?
Line 273: “low frequency” – Low frequency of what? Was your diatom analysis quantitative? If so, please include information on markers used during the analysis in Section 3.4.
Line 288: “dystrophic diatoms” – Please list the dominant species of dystrophic diatoms in brackets.
Lines 290-296: For the species listed, it would be useful to indicate their classification into ecological groups, as shown in Figure 4B.
Section 4.3.1: This section is too short (less than two lines). It would be advisable to add more information, for example regarding the error in the reconstructed DI-pH values. It might also be worth considering merging sections 4.3 and 4.3.1.
Figure 4A: Explain the abbreviation DAZ in the figure caption. Please mention somewhere in the Results that all DAZs are statistically significant zones.
Lines 316-317: “Three cladoceran zones (CLZ) were distinguished” → “Three statistically significant cladoceran zones (CLZ) were distinguished”
Section 4.4 and Figure 5: Cladocerans are not classified into any ecological groups here. Would it be possible to change that? Are any of the cladoceran taxa found typical of dystrophic lakes?
Lines 385-388: “Water-level fluctuations and changes in groundwater or surface-water supply could have intensified the contact between lake water and organic-rich peat substrates, thereby enhancing the leaching of humic substances into the basin.” – Do you see any clear evidence of water-level fluctuations in your results? Or is it just one of the possible interpretations of the results obtained?
Line 395: “Close to TSN occurred raised and transitional peat bogs.” – The presence of Toporowy Staw Wiżni (the nearby almost completely infilled dystrophic lake) should be mentioned here.
Line 399: “elevated biodiversity” – Could you be a bit more specific about this? Is the biodiversity observed in TSN exceptional compared to other (Central European) dystrophic lakes?
Lines 420-423 and 426-428: “Domination of small form of Staurosira is characteristic for boreal forest lakes, shallow, nutrient-poor cold environments with short growing season (Rühland et al., 2003). There are diatom taxa occurring very often in oligotrophic and mesotrophic water bodies, but not typical for dystrophic waters (Morales, 2001).” & “including S. construens var. venter, which may indicate meso-eutrophic conditions (Cantonati et al., 2021)” – In your record, DAZ 1 and the first half of DAZ 2 are strongly dominated by the diatom S. construens var. venter. This taxon is not a good indicator of trophic conditions. In some dystrophic lakes, its relative abundance is high (e.g., Kavková et al. 2022).
441-443: “Low carbon isotopic signal means that organic matter is dominated by peat, leaves, humus and low internal production in lake.” – Is this interpretation supported by lake sediment lithology? Would it be possible to add some information about the lithology to the manuscript?
Lines 511-512: “Cladocera, the best indicator of changes in trophic state was Camtocercus rectirostris, a species previously reported from dystrophic lake (Zawisza et al., 2019).” – Camtocercus rectirostris is not a typical cladoceran of dystrophic lakes (see Błedzki and Rybak 2016). I suggest focusing on Acroperus elongatus (Alonopsis elongata), Alonella excisa, and Alonella nana.
Line 518: “biogenic substances” – Could you explain what you mean by this term?
Lines 583-586: “The comparison with Lake Suchar IV is particularly useful in this context, because Zawisza et al. (2019) showed that dystrophication may represent an alternative pathway of lake development, driven by lake–peatland succession and humic-matter input rather than by classical eutrophication.” – A comparison with a mountain lake that has followed a similar trajectory (i.e., dystrophication) during its evolution would be even more useful.
Lines 603-604: “The present dystrophic state of TSN appears to be the result of long-term natural lake development rather than direct anthropogenic impact.” – Please give a few examples (in the Introduction section or Discussion section) of natural lakes that have become dystrophic because of direct anthropogenic impact.
It would be great if this study included a Supplementary Material file. This file could show, for example, the following items:
Technical corrections
Line 51: “abundant. (Karpowicz et al., 2026).” → “abundant (Karpowicz et al., 2026).”
Line 81: “last 3000 years” → “last ca. 3000 years”
Line 102: “49.2835806 N, 20.0305586 E” → “49.2836° N, 20.0305° E”
Line 137: “Core chronology based” → “Core chronology was based”?
Line 156: “lead-210” → “Pb-210” (I recommend using abbreviations consistently)
Line 164 versus line 172: “1150° C” vs. “1020°C” (I recommend using units consistently – with space or without space)
Line 179 versus line 190: “(Battarbee 1986)” vs. “(Juggins, 2023)” – Unify the style for abbreviated citations.
Line 220: “zonation was performer with” → “zonation was performed with”
Line 237: “14C” – This abbreviation is used only here and in Table 1 in the manuscript. Moreover, it is not explained anywhere in the manuscript.
Fig. 3: The y-axes are not labelled.
Fig. 4: Explain the colors used in the two diagrams. Error bars should be shown for DI-pH.
Fig. 5: “Iliocryptus” → "Ilyocryptus"; Use the same font for values on the age and depth y-axes.
Line 404: “Sphagnum” → "Sphagnum" (use italics; the same appears elsewhere in the manuscript)
Line 414 (and elsewhere in the manuscript): “cal. yr. BP” or “cal. BP”? Please ensure you maintain a consistent style when using this unit.
Additional references
Błedzki L. A., Rybak J. I. (2016): Cladocera & Copepoda (Calanoida, Cyclopoida): Key to species identification, with notes on ecology, distribution, methods and introduction to data analysis. Springer. DOI :10.1007/978-3-319-29871-9
Florescu G., Tinner W., Feurdean A., Finsinger W., Kuneš P., Vondrák D., Heurich M., van der Knaap W. O., Brychová V., Kletetschka G., Carter V. (2024): Forest composition and density shaped long-term fire regimes and catchment-lake interactions in the temperate-mixed mountain forests of Central Europe. Forest Ecology and Management 572: 122267. DOI: 10.1016/j.foreco.2024.122267
Gąsiorowski M., Sienkiewicz (2010a): The Little Ice Age recorded in sediments of a small dystrophic mountain lake in southern Poland. Journal of Paleolimnology 43: 475-487. DOI: 10.1007/s10933-009-9344-5
Hamrová E., Goliáš V., Petrusek A. (2010): Identifying century-old long-spined Daphnia: species replacement in a mountain lake characterized by paleogenetic methods. Hydrobiologia 643: 97-106. DOI: 10.1007/s10750-010-0127-9
Kavková R., Vondrák D., Chattová B., Švecová E., Takáč M., Goliáš V., Štorc R., Stanghellini C., Kletetschka G. (2022): Suzdalevo Lake (Central Siberia, Russia) —A Tunguska Event-related impact crater? Frontiers in Earth Science 10: 777631. DOI: 10.3389/feart.2022.777631
Levkov Z., Krtic S., Nakov T., Melovski L. (2005): Diatom assemblages on Shara and Nidze Mountains, Macedonia. Nova Hedwigia 81 (3-4): 501-537. DOI: 10.1127/0029-5035/2005/0081-0501
Mariani M., Beck K. K., Fletcher M.-S., Gell P., Saunders K. M., Gadd P., Chisari R. (2018): Biogeochemical responses to Holocene catchment-lake dynamics in the Tasmanian World Heritage Area, Australia. Journal of Geophysical Research: Biogeosciences 123: 1610–1624. DOI: 10.1029/2017JG004136
Nilssen J. P., Hobæk A., Petrusek A., Skage M. (2007): Restoring Daphnia lacustris G.O. Sars, 1862 (Crustacea, Anomopoda): A cryptic species in the Daphnia longispina group. Hydrobiologia 594: 5–17. DOI: 10.1007/s10750-007-9076-3
Norton S. A., Perry R. H., Saros J. E. et al. (2011): The controls on phosphorus availability in a Boreal lake ecosystem since deglaciation. Journal od Paleolimnology 46: 107–122. DOI: 10.1007/s10933-011-9526-9
Perret-Gentil N., Rey F., Gobet E., Tinner W., Heiri O. (2024): Human impact leads to unexpected oligotrophication and deepwater oxygen increase in a Swiss mountain lake. The Holocene 34(2): 189-201. DOI: 10.1177/09596836231211821
Petrusek A., Černý M., Mergeay J., Schwenk K. (2007): Daphnia in the Tatra Mountain lakes: multiple colonisation and hidden species diversity revealed by molecular markers. Fundamental and Applied Limnology (Archiv für Hydrobiologie) 169(4): 279–291. DOI: 10.1127/1863-9135/2007/0169-0279
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Sacherová V., Kršková R., Stuchlík E., Hořická Z., Hudec I., Fott J. (2006): Long-term change of the littoral Cladocera in the Tatra Mountain lakes through a major acidification event. Biologia 61/Suppl. 18: S109-S119. DOI: 10.2478/s11756-006-0124-7
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Szarłowicz K., Stobiński M., Jedrzejek F., Kubica B. (2022): Sedimentary conditions based on the vertical distribution of radionuclides in small dystrophic lakes: a case study of Toporowe Stawy Lakes (Tatra Mountains, Poland). Environmental Science and Pollution Research 29: 89530–89541 DOI: 10.1007/s11356-022-21922-3
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