The Role of Phytoplankton in the Assessment of the Ecological State of the Floodplain Lakes of the Irtysh River, Kazakhstan
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript presents original and valuable data on the phytoplankton of floodplain lakes in the Irtysh River basin of Kazakhstan, a region that is ecologically important but understudied, and both in terms of content and quality can be recommended to be published in the journal Environments. The authors examined in detail the species composition, abundance indices, and analyzed them using modern methods of statistical analysis.
At the same time, in my opinion, the reasons for the results obtained require more extensive analysis and discussion. A number of inaccuracies and misspellings are also present, which require additional proofreading of the text.
Below are my comments and suggestions for improvement:
- The temperature data (Table 2) and sampling months (July 2023 vs June 2024) could suggest seasonal differences which could drive community shifts. It is well known that there are seasonal complexes of plankton microalgae and certain seasonal sequences of change of these complexes. In particular, green algae are usually dominant in spring plankton, while cyanobacteria begin to dominate in summer. In June 2024, the authors most likely captured the remainder of the spring complexes, which probably led to the established difference in algal complexes. This important issue, which can explain these differences, but not discussed in the manuscript. It is possible that this will also require a change in the statistical analysis, since in this case aquatic communities should be assessed as different assemblages of species and dominant groups. I would suggest to statistically test the "year/season" effect on assemblage composition and expand the Discussion accordingly.
- Table 3 looks too extensive for the main text and better to be moved to the appendices.
- Line 22: “Ceratium hirudinella” – misspelling.
- Lines 94, 97 etc.: names “Stary Irtysh” and “Old Irtysh” are used simultaneously. Please choose one name for consistency. “Stary Irtysh” seems to be more appropriate.
- Line 130: "Samples for the determination of nutrients were collected in glass bottles with a volume of 0.5 L and preserved with chloroform (1 L)" The method looks doubtful. Please provide reference for this method.
Author Response
Dear Editor and the Reviewer 1,
Thank you for your comments in the Report. Lease find our responses to each comment below.
With best regards, Prof Sophia Barinova,
Corresponding author
Comments and Suggestions for Authors
The manuscript presents original and valuable data on the phytoplankton of floodplain lakes in the Irtysh River basin of Kazakhstan, a region that is ecologically important but understudied, and both in terms of content and quality can be recommended to be published in the journal Environments. The authors examined in detail the species composition, abundance indices, and analyzed them using modern methods of statistical analysis.
At the same time, in my opinion, the reasons for the results obtained require more extensive analysis and discussion. A number of inaccuracies and misspellings are also present, which require additional proofreading of the text.
Below are my comments and suggestions for improvement:
- The temperature data (Table 2) and sampling months (July 2023 vs June 2024) could suggest seasonal differences which could drive community shifts. It is well known that there are seasonal complexes of plankton microalgae and certain seasonal sequences of change of these complexes. In particular, green algae are usually dominant in spring plankton, while cyanobacteria begin to dominate in summer. In June 2024, the authors most likely captured the remainder of the spring complexes, which probably led to the established difference in algal complexes. This important issue, which can explain these differences, but not discussed in the manuscript. It is possible that this will also require a change in the statistical analysis, since in this case aquatic communities should be assessed as different assemblages of species and dominant groups. I would suggest to statistically test the "year/season" effect on assemblage composition and expand the Discussion accordingly.
Response: We cannot a priori state which complexes belong to different seasons, since only summer collections were made in two consecutive years. This is a matter for future monitoring, and then we will be able to identify seasonality and analyze changes using statistical methods. As for the difference between the two years, it is clearly traced using statistical methods and allows us to make an assumption about landscape and climatic influences that have a more significant effect on the composition of phytoplankton than the individuality of the species composition in each of the surveyed lakes.
- Table 3 looks too extensive for the main text and better to be moved to the appendices.
Response: Table corrected but left into main text for better relation of reader to results
- Line 22: “Ceratium hirudinella” – misspelling.
Response: corrected
- Lines 94, 97 etc.: names “Stary Irtysh” and “Old Irtysh” are used simultaneously. Please choose one name for consistency. “Stary Irtysh” seems to be more appropriate. Response: Corrected. “Old Irtysh” was corrected to “Stary Irtysh”
- Line 130: "Samples for the determination of nutrients were collected in glass bottles with a volume of 0.5 L and preserved with chloroform (1 L)" The method looks doubtful. Please provide reference for this method.
Response: Corrected, according to [31] Semenov, A.D. Manual for Chemical Analysis of Surface Waters of Land; Gidrometeoizdat: Leningrad, Russia, 1977; pp. 156–163. (In Russian)
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript is a study on the use of phytoplankton to determine the quality of lakes on the Irtysh River. The study is interesting, but the manuscript's quality is very poor, and its acceptance is highly questionable. Therefore, it is necessary to improve the quality of the manuscript and address some important issues.
1) Site description: Rather than describing the entire area, authors should provide information on the geological substrate.
2) Figure 1: Honestly, the two photos in this figure don't add anything. The caption doesn't indicate their possible significance. Author of those photos?However, I miss throughout the manuscript some photos taken of the found algae, at least of the most abundant ones. They would be good as supplementary material.
3) Figure 2 Caption: Describe in more detail what should be observed in each photo.
4) Sampling: How many samples were taken from each lake? This is where this information should be reported. Why was the number of samples unequal within each lake?. Where were the samples taken (in which part of the lake), or were the measurements made? Were these samples representative of the entire water body? The authors distinguish between epiphytes and planktonic species, so were surface samples sampled? Please explain the entire sampling process in more detail.
5) Line 130: Was 1 L of chloroform used for every 0.5 L of sample? Check.
6) Lines 139-146: Where are these results?
7) mL better with capital letters.
8) Lines 167-168: This calculation doesn't make sense. If you multiply cell count/volume * volume, the result is cell count, not mg/L.
9) The authors use two Shannon indices but a single formula. Please explain in more detail.
10) Line 201: Baskol was not alkaline.
11) Conductivity is an important parameter and relatively easy to measure. Why wasn't this measurement performed?
This parameter is important for determining effects on phytoplankton communities.
12) Has the possibility of determining whether there were statistically significant differences between the lakes been assessed, taking into account the FQ variables (e.g., MANOVA)? In other words, were the lakes significantly different?
13) Line 206: How did the authors reach this conclusion without determining conductivity or calcium and magnesium?
14) Table 3: I cannot clearly understand how the data is expressed in this table. If the occurrence is in %, why do they not add up to 100%? How should this table be read?
15) Line 237: Where is the st.1 site located?
16) Figure 3: Indicate the results of an ANOSIM.
17) Figure 4: There is data for only two years for two lakes. Why are data from the other lakes included? This analysis should only be used for lakes with data for both years.
18) Lines 305-310: This entire paragraph requires references.
19) Figure 10: The authors should have measured salinity (conductivity) to be consistent with this graph. What was the salinity of these lakes?
20) Figure 11: What trophic status does each lake fall under based on the physicochemical data? Please explain in more detail. References on this possible classification would be necessary.
21) Figure 13: The physicochemical parameters do not correspond exactly to Table 2. Where is the pH? Explain. Why is TDS one of the most important factors? The length of the arrow is not the longest. These results need to be explained in more detail and with greater rigor.
22) The authors use extensive Russian bibliography, the content of which appears to be very similar, in some cases, to the content of this manuscript. Please explain in more detail the new features of this work. Please revise the reference format to make it more uniform.
Author Response
Dear Editor and the Reviewer 2,
Thank you for your comments in the Report. Lease find our responses to each comment below.
With best regards, Prof Sophia Barinova,
Corresponding author
Comments and Suggestions for Authors
This manuscript is a study on the use of phytoplankton to determine the quality of lakes on the Irtysh River. The study is interesting, but the manuscript's quality is very poor, and its acceptance is highly questionable. Therefore, it is necessary to improve the quality of the manuscript and address some important issues.
- Site description: Rather than describing the entire area, authors should provide information on the geological substrate.
Response: added
- Figure 1: Honestly, the two photos in this figure don't add anything. The caption doesn't indicate their possible significance. Author of those photos?However, I miss throughout the manuscript some photos taken of the found algae, at least of the most abundant ones. They would be good as supplementary material.
Response: Figure 1 replaced. Organisms photo added.
3) Figure 2 Caption: Describe in more detail what should be observed in each photo.
Response: Corrected
4) Sampling: How many samples were taken from each lake? This is where this information should be reported. Why was the number of samples unequal within each lake?. Where were the samples taken (in which part of the lake), or were the measurements made? Were these samples representative of the entire water body? The authors distinguish between epiphytes and planktonic species, so were surface samples sampled? Please explain the entire sampling process in more detail.
Response: Added. At each lake, all samples (phytoplankton, water samples for chemical analysis, measurements) were collected at three conventional stations at one time. A total of 24 phytoplankton samples were collected over two years. The same number of samples were collected at the same stations for chemical analysis.
The number of stations was the same at each lake (three at each lake at one time).
The stations were located at approximately equal distances from each other: one in the central part of the lake and two others in the coastal zone in opposite parts of the lake. We additionally showed their location on the map.
The lakes have a water area from 0.43 to 1.68 km2. If we divide the water area by the number of stations, we get one station per 0.14-0.56 km2.
We are talking about the ecological preferences of algae species. In the water column, not only planktonic species can be found, but also planktonic-benthic and epiphytes. This is discussed in more detail in the monograph (Barinova 2025). The sampling methods are described in the corresponding section “Material and Methods”.
5) Line 130: Was 1 L of chloroform used for every 0.5 L of sample? Check.
Response: Corrected. It was a technical mistake. 1mL of chloroform was added for every 0.5 L of sample
6) Lines 139-146: Where are these results?
Response: Data added to table 2.
7) mL better with capital letters.
Response: left mL as the journal rules recommended.
8) Lines 167-168: This calculation doesn't make sense. If you multiply cell count/volume * volume, the result is cell count, not mg/L.
Response: “The biomass of each species in the sample was then determined by multiplying the average cell volume (mass) by the number of cells”. This is the average individual cell mass of each species, which is calculated using the appropriate formulas. This method for calculating the biomass of cells/species/the entire phytoplankton community is described in many manuals as cited for example Hillebrand et al., 1999.
9) The authors use two Shannon indices but a single formula. Please explain in more detail.
Response: The same formula given in the paper (formula 2) is used to calculate the Shannon index. The index values ​​are calculated in the PRIMER program. Original data on the species composition, abundance and biomass of each species are used. The Shannon Ab index is calculated based on the ratio (share) of species in the total abundance of the community, Shannon Bi – based on the ratio (share) of species in the total biomass of the community.
10) Line 201: Baskol was not alkaline.
Response: Corrected
11) Conductivity is an important parameter and relatively easy to measure. Why wasn't this measurement performed?
Response: Water conductivity is measured to determine the total content of dissolved salts. This indicator is an approximate characteristic of the concentration of inorganic electrolytes in water - cations Na+, K+, Са2+, Mg2+ and anions Сlˉ, SO42-, HCO3-. We took a different approach. A more accurate method for determining the ionic composition of water is laboratory analysis, which was used in this study.
12) Has the possibility of determining whether there were statistically significant differences between the lakes been assessed, taking into account the FQ variables (e.g., MANOVA)? In other words, were the lakes significantly different?
Response: MANOVA was not used. Other statistical programs were used, as indicated in the MM section.
13) Line 206: How did the authors reach this conclusion without determining conductivity or calcium and magnesium?
Response: The conclusion was made based on the data on total dissolved solids concentration (TDS) and other ions concentration (table 2). It characterizes the total content of ions (dissolved salts) in each water sample.
14) Table 3: I cannot clearly understand how the data is expressed in this table. If the occurrence is in %, why do they not add up to 100%? How should this table be read?
Response: Occurrence is calculated for each species separately; it is not a total indicator for all species. Occurrence is calculated using the formula: the number of samples where the species was encountered is divided by the total number of samples (separately for each lake) and multiplied by 100%. If the species is encountered in all samples, the occurrence is 100%, if in half of the samples from the total number - 50%, etc. This indicator characterizes how common (widely distributed) a particular species is within the water area of ​​the surveyed reservoir.
15) Line 237: Where is the st.1 site located?
Response: Location of stations added to the map.
16) Figure 3: Indicate the results of an ANOSIM.
Response: done in figure caption
17) Figure 4: There is data for only two years for two lakes. Why are data from the other lakes included? This analysis should only be used for lakes with data for both years.
Response: We tried not to artificially select the data analyzed arrays, thereby excluding many of them. But we analyzed the entire available data array on the abundance and biomass of phytoplankton using different methods and in this analysis in Figure 4, similarity of quantitative data of phytoplankton by years of survey was revealed, which we did not seek to identify, but similarity of more than 50% revealed such a dependence.
18) Lines 305-310: This entire paragraph requires references.
Response: This paragraph presents the results of bioindication. In order not to clutter the description, the relevant references are given in the section “Material and Methods” and in the notes to Tables B1 and B2 as: Abbreviation of ecological groups are as in cited [8].
19) Figure 10: The authors should have measured salinity (conductivity) to be consistent with this graph. What was the salinity of these lakes?
Response: Figure 10 represents bioindication results. Section 4.1. Hydrophysical and Hydrochemical Characteristics contain data on water TDS and chlorides for each of the surveyed lakes. Concentration of chlorides and salinity are the same thing, only the first term is used for inland water bodies, and the second for marine ones. Since the data in the ecological database are unified and relate to water bodies of different types (Barinova 2025), we use the term “salinity”, which is used in the work cited above.
20) Figure 11: What trophic status does each lake fall under based on the physicochemical data? Please explain in more detail. References on this possible classification would be necessary.
Response: Figure 10 represents bioindication results. Relations of each group of bioindicators to the Environment variables ranks are shown in the cited paper of ecological database that also related to environmental classification [8, 61 and 64 in corrected version], Added. cited in Van Dam H, Mertens A, Sinkeldam J. A coded checklist and ecological indicator values of freshwater diatoms from the Netherlands. Netherland J. Aquat. Ecol. 1994, 28, 117–133. Added to Discussion section also text and the references: Barinova, S. On the Classification of Water Quality from an Ecological Point of View. International Journal of Environmental Sciences & Natural Resources 2017, 2(2), 1-8. DOI: 10.19080/IJESNR.2017.02.555581
21) Figure 13: The physicochemical parameters do not correspond exactly to Table 2. Where is the pH? Explain. Why is TDS one of the most important factors? The length of the arrow is not the longest. These results need to be explained in more detail and with greater rigor.
Response: As required by correspondence analysis, the number of dependent and independent variables must match. Thus, we selected measurement and chemical analysis data as independent parameters, and biological variables as dependent variables. But the analysis has a function of statistical testing and exclusion of one environmental and one biological parameter from the visible ones. In this analysis, pH was excluded from the visible ones. But it was included in the analysis.
We mentioned that: The primary factor explaining the variability in green algae biomass was phosphate and TDS levels. So, the largest arrows are P-PO4 and TDS that coincidence with Chlorophyta biomass.
22) The authors use extensive Russian bibliography, the content of which appears to be very similar, in some cases, to the content of this manuscript. Please explain in more detail the new features of this work. Please revise the reference format to make it more uniform.
Response: Since the objects of this study are considered for the first time and there is no literature on previous studies, we were forced to use data described in nearby water bodies. Unfortunately, in this poorly studied region, we found only a few works published in Russian. They enriched the list and showed our careful work with the material. In addition, several references were made to the methods used in the hydrochemical laboratory in Kazakhstan that supports our research; it uses references in Kazakh or Russian-language sources, we preferred the latter. However, overall, we have reviewed the references, added some English-language references and renumbered the bibliography. The novelty mentioned in Abstract, MM and Conclusion sections.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors of the manuscript have generally done a good job of correcting minor comments. However, my primary and most significant concern regarding the interpretation of the phytoplankton community differences remains unresolved. The reliance of authors on a statistical assessment of environmental variables to explain away the role of seasonal succession is, in my view, methodologically unsound and conceptually misleading.
The sampling design (single time points in July 2023 and June 2024) initially captures communities at different stages of seasonal succession. It is a well-established principle in limnology that phytoplankton assemblages undergo predictable successional changes throughout the growing season. Typically, green algae often dominate in spring, while cyanobacterial blooms are a hallmark of late summer conditions. The observed differences between lakes sampled in June 2024 and July 2023 are likely confounded by this seasonal effect.
Since the authors do not have the sequential data within a single year to quantify this, I must return to my previous recommendation: this central limitation must be explicitly acknowledged and discussed in the manuscript. A formal statistical analysis of environmental data cannot disprove or negate the potential influence of an unmeasured temporal variable like seasonality.
I strongly suggest adding a paragraph to the Discussion section that:
- acknowledges that the sampling design captured lakes at different potential stages of seasonal succession
- cites relevant literature on typical seasonal phytoplankton succession in temperate floodplain lakes
- posits that the observed community differences could be influenced by these seasonal dynamics, in addition to the hydrological and nutrient factors they analyzed
- notes that future studies involving intra-annual sampling are needed to disentangle the effects of seasonality from spatial and anthropogenic factors
Incorporating this discussion would significantly strengthen it by demonstrating a nuanced understanding of ecological dynamics. It would frame the conclusions more appropriately within the context of the study's limitations and add valuable depth for the reader. Merely referring to statistics in a response letter without addressing this fundamental ecological concept in the manuscript itself is insufficient.
I recommend to accept the manuscript after considering of this crucial discussion point.
Author Response
Dear reviewer!
We appreciate your valuable comments, which we have taken into account.
The text of the article has been supplemented with data on the climatic climate of Kazakhstan (in particular, on the beginning of the relatively summer period, which does not correspond to the calendar beginning of summer; information on the frequent return of cold weather in May and June).
Some inaccurate wording that could be used to understand the presented material has been corrected.
In the "Discussion" section, extensive comparative material has been added on the effect of temperature as one of the primary predictors of the seasonal dynamics of phytoplankton in various types of water bodies.
It has been demonstrated that the seasonal succession of phytoplankton varies according to the specific water body. Increased water temperature in the spring stimulates the development of phytoplankton, but its further development is largely determined by the availability of nutrients or other limiting factors. Information has been added on the need for extended and long-term studies of the Irtysh River floodplain lakes to determine the complex, region-specific and constantly changing abiotic factors on phytoplankton as the basis for the primary productivity of the ecosystem.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript has been clearly improved. The requested changes have been appropriately addressed. The answers to the questions posed have been adequately answered. In my view, the manuscript can be accepted.
Author Response
Dear Reviewer 1,
Thank you very much for recommendation.
With best regards,
authors
