Spatial Distribution Patterns of Zooplankton and Macroinvertebrates in a Small River under Strong Anthropogenic Pressure

Round 1

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors

The manuscript with title “Spatial distribution patterns of zooplankton, and macroinvertebrates in a small river under strong anthropogenic pressure” is well written and is dealing with an extremely pressing problem – what are the consequences of strong anthropogenic pressure experienced by riverine ecosystems. Below is a list of suggested changes and additions, which I believe would improve the quality of the manuscript:

1.       Add (if it is possible using the same materials) an analysis and respective comments on the relative dominance of the general functional groups (shredders, collectors, grazers, and predators). It might give even more value to the main findings of the authors and shed new light on the noticed deviations from the expectations of the River Continuum Concept (RCC).

2.       I recommend also to expand a little more the explanation (which is included in the Introduction) of the main postulates of the RCC. Also may be include a pragraph on what is already known about the applicability of RCC to zooplankton composition (both littoral and pelagic) in small lowland rivers.

 

3.       Adding a paragraph on the limitations of the study and advises on what should focus on or what should be included in the further research on the topic, could be useful. May be put that somewhere before the conclusions or as part of them.

4.       Rephrase the following: “We discovered two studies on the ecological state” to “I two of the studies on the ecological state…”

5.       The results presented in Table 3 could be included in the text and the table removed.

6.       Enhance the quality of Figure 3 and Figure 4, et least in the pdf for review, the text on the figures is not readable, I do not know if that’s the case with the originals.

7.       In Table 4, please add column names, or state such names in the annotation of this table.

8.       In the Discussion on row 247, I suggest changing: “Dzierżęcinka is an pattern river that consists of…”, to “Dzierżęcinka is a model river that is under the influence of…”.

Please, see the attached pdf for further comments.

I recomend the publication of the mresented for review manuscript after the listed minor changes are applied.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 1

1. Add (if it is possible using the same materials) an analysis and respective comments on the relative dominance of the general functional groups (shredders, collectors, grazers, and predators). It might give even more value to the main findings of the authors and shed new light on the noticed deviations from the expectations of the River Continuum Concept (RCC).

Response: We think it is not necessary because RCC is not visable in examined river. We think that used data as family of macrozoobenthos are better factor of changes than functional feeding groups. They are responsible to show the effect of regulated bed on macrozoobenthos communities.

2. I recommend also to expand a little more the explanation (which is included in the Introduction) of the main postulates of the RCC. Also may be include a pragraph on what is already known about the applicability of RCC to zooplankton composition (both littoral and pelagic) in small lowland rivers.

      Response: We added to introduction the sentence: RCC is a pattern based on feeding functional groups of macroinvertebrates mainly, however it not describes some changes in drifting zooplankton structures. .  

3. Adding a paragraph on the limitations of the study and advises on what should focus on or what should be included in the further research on the topic, could be useful. May be put that somewhere before the conclusions or as part of them.

 

Response: We added the sentence at the end of discussion. Either way, it is worth examining in further research what are the patterns of changes in both drifting zooplankton and macrozoobenthos communities in differently regulated rivers. There are rivers regulated for river navigation, for water retention in the riparian zone in meadows and forests, and for fish ponds. Regulations such as threats require the use of many different hydrotechnical structures affecting river fauna and flora. Thus, different regulations may shape different structures of drifting zooplankton and macrozoobenthos.

 

4. Rephrase the following: “We discovered two studies on the ecological state” to “I two of the studies on the ecological state…”

Response: We changed the sentence on: We found two studies on the ecological state of Dzierżęcinka concerning the macroinvertebrate structure, primarily conducted in the urban section of the river [18, 19].

5. The results presented in Table 3 could be included in the text and the table removed.

 

We think that results included in table are better visible for reader.

 

6. Enhance the quality of Figure 3 and Figure 4, et least in the pdf for review, the text on the figures is not readable, I do not know if that’s the case with the originals.

 

Quality of figures was corrected.

7. In Table 4, please add column names, or state such names in the annotation of this table.

It was corrected

8. In the Discussion on row 247, I suggest changing: “Dzierżęcinka is an pattern river that consists of…”, to “Dzierżęcinka is a model river that is under the influence of…”.

It was corrected

Please, see the attached pdf for further comments.

It was takes into account and corrected. Yes, the applicability if RCC is more pronounced for drifting organisms in small lowland rivers which are not experiencing such drong antropopressure.

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Dear Editor,

I have completed my review of the manuscript that evaluates the spatial and temporal distribution of aquatic invertebrates in an impacted river.

 

The manuscript attempts to delve into an important area of aquatic ecology, addressing the distribution of organisms along a river. However, there are several areas that require significant improvement to enhance the clarity, precision, and overall quality of the study.

 

Hypotheses and Objectives: The introduction discusses relevant theories but falls short in clearly defining the hypotheses and objectives of the study. I suggest the authors more explicitly detail the questions being tested and elucidate the ecological processes associated with the spatial and temporal distributions observed.

Figure and Table Quality: The resolution of the three maps in Figure 1 is inadequate for assessing the information, including the critical locations of sampling points. This needs rectification. In Table 1, I recommend adopting the American standard of using a dot instead of a comma as a decimal separator for consistency and clarity.

Methodological Choices: The use of Jaccard's distance in the analysis is questionable, as it does not disregard double absences. Sørensen's distance would be a more appropriate metric for assessing community similarity.

Representative Months and Mantel Test: The manuscript lacks clarity on what criteria were used to determine the 'most representative' months for the Mantel test. A detailed explanation of this selection process is essential.

Data Presentation: Table 3 appears redundant. It would be more effective to integrate the Mantel correlation values and p-values directly into the text. Similarly, Table 4, which lacks column names and features excessive decimal places, could be condensed into the text for brevity and clarity.

Canonical Correspondence Analysis (CCA): The presentation of CCA eigenvalues without the percentage of explanation is a significant oversight. Additionally, the exclusion of non-significant predictor variables would refine the analysis. The authors should perform a variable selection procedure. The figures supporting this analysis (Figures 3 and 4) suffer from low resolution and small font sizes, hindering proper evaluation. I recommend using abbreviations and other strategies to improve readability and focusing on significant predictor variables.

Methodologies for Water Quality Metrics: The authors present various water quality metrics (chloride, chlorophyll, nitrates, total phosphorus, total nitrogen and ammonia) without detailing the methodologies used for their quantification. This information is vital for the scientific rigor of the study.

Conclusions and Limitations: While the conclusions are somewhat supported by the results, the limitations imposed by the low resolution of the CCA graphs and the temporal scope of the study (only one year) need to be addressed. It is crucial to clarify that these findings are specific to the year of study and may not represent a consistent pattern across different years.

 

I recommend major revisions to address these concerns. The manuscript has the potential to contribute meaningfully to our understanding of aquatic ecosystems in Poland, but it requires significant improvements in clarity, methodology, and presentation to realize this potential.

Comments on the Quality of English Language

The text is mostly free from spelling errors and the grammar seems OK, with few instances. For example, "is an pattern river..." (line 247) should be "is a pattern river..."

Author Response

1. Hypotheses and Objectives: The introduction discusses relevant theories but falls short in clearly defining the hypotheses and objectives of the study. I suggest the authors more explicitly detail the questions being tested and elucidate the ecological processes associated with the spatial and temporal distributions observed.

 

Response: We added to introduction few sentences about your suggestion.

The River Continuum concept is a model that assumes that each natural watercourse is a longitudinally changing ecosystem that connects to the shore. The ratio of primary pro-duction to respiration is different along the river course. In natural state of river the upper forested sections, primary production is low, but there is a large inflow of coarse-particle organic matter. Due, the macrozoobenthos biocenosis is dominated  by shredders collec-tors. In upper section zooplankton not exists, because the current velocity is too fast and amount of drifting organic food is also low. In lower section of rivers  where fine-particle of organic matter dominate the composition of feeding group of macrozoobenthos is changing. Hence, the macrozoobenthos is dominated by filtrators and collectors. Due to low current velocity the volume of water in lower course of river is habitated by zooplankton and phytoplankton.

The aim of study was to examine a pattern of spatial distribution of benthic and drifting invertebrates (macrozoobenthos and zooplankton) in degraded river, still being under strong human pressure.

 

2. Figure and Table Quality: The resolution of the three maps in Figure 1 is inadequate for assessing the information, including the critical locations of sampling points. This needs rectification. In Table 1, I recommend adopting the American standard of using a dot instead of a comma as a decimal separator for consistency and clarity.

Response: It was corrected

3. Methodological Choices: The use of Jaccard's distance in the analysis is questionable, as it does not disregard double absences. Sørensen's distance would be a more appropriate metric for assessing community similarity.

 

Response. Yes, however the Jaccard index is widely used in taxonomical comparisons between sites. We think it is a well adding to CCA, that orditaned both qulitative distribution of taxa and sites regarding to abundace.

 

4. Representative Months and Mantel Test: The manuscript lacks clarity on what criteria were used to determine the 'most representative' months for the Mantel test. A detailed explanation of this selection process is essential.

 

Response. In the Palearctic, due to the phenology of organisms, the most representative month for zooplankton are the summer months: from June to August. For benthic macroinvertebrates, the most representative month is May - before the well-developed larvae of the last stage of insects leave the water reservoir. This information is basic knowledge and, in our opinion, does not require additional explanation in the text.

 

 

5. Data Presentation: Table 3 appears redundant. It would be more effective to integrate the Mantel correlation values and p-values directly into the text. Similarly, Table 4, which lacks column names and features excessive decimal places, could be condensed into the text for brevity and clarity.

 

Response: We think that results included in table are better visible for reader.

 

6. Canonical Correspondence Analysis (CCA): The presentation of CCA eigenvalues without the percentage of explanation is a significant oversight. Additionally, the exclusion of non-significant predictor variables would refine the analysis. The authors should perform a variable selection procedure. The figures supporting this analysis (Figures 3 and 4) suffer from low resolution and small font sizes, hindering proper evaluation. I recommend using abbreviations and other strategies to improve readability and focusing on significant predictor variables.

Respone: Percentage of explanation is given in the text. We have tried to improve the visibility of CCA.

 

7. Methodologies for Water Quality Metrics: The authors present various water quality metrics (chloride, chlorophyll, nitrates, total phosphorus, total nitrogen and ammonia) without detailing the methodologies used for their quantification. This information is vital for the scientific rigor of the study.

 

Response; All parameters except of PTOT (total phosphorus) and NTOT (total nitrogen) were measured using multiprobe Hydrolab DS5 (USA). PTOT and NTOT were measured using photometer Hach Lange Dr 890 (USA).

 

 

8. Conclusions and Limitations: While the conclusions are somewhat supported by the results, the limitations imposed by the low resolution of the CCA graphs and the temporal scope of the study (only one year) need to be addressed. It is crucial to clarify that these findings are specific to the year of study and may not represent a consistent pattern across different years.

 

Response: Quality of CCA figures was corrected

 I recommend major revisions to address these concerns. The manuscript has the potential to contribute meaningfully to our understanding of aquatic ecosystems in Poland, but it requires significant improvements in clarity, methodology, and presentation to realize this potential.

 

The text is mostly free from spelling errors and the grammar seems OK, with few instances. For example, "is an pattern river..." (line 247) should be "is a pattern river..."

It was changed into new sentence

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Materials and Methods section. Lines 120-125 - Table 1 would be better suited for the Results section. Also, based on the recorded parameters, a classification of the five sampling sites should be made so that the reader can understand more easily which are the most polluted areas. What are the parameters that indicate anthropogenic pollution?

Discussion section. Sometimes the authors use a vague, confusing expression, such as the text on lines 267-275. We did not understand the mechanism by which anthropogenic factors negatively influence the respective taxa. Anthropogenic influence and pollution are generous and very broad terms. I would suggest the authors to coherently examine each factor and its influence on the analysed species.

Lines 275-276. I ask the authors to be more specific about the microhabitats created by man. Which are these? How do they influence the analysed species?

Lines 277-286. The authors describe the transition from spring to summer and the succession of different species. How does anthropogenic activity influence this succession which at first sight seems to be natural?

Lines 297-298. What is the scale considered by the authors when they talk about microhabitat? Millimeters, centimeters?

Line 313. It is a confusing wording. What do the authors understand more precisely by this statement? I ask the authors to clarify.

Lines 314-316. Again it is a confusing phrase to understand. Additional clarifications please!

Conclusions section.

Lines 324-325. Please explain the statement made by you! Why do changes in zooplankton composition occur rather in time than in space? Does anthropogenic activity manifest itself only in certain periods of time? I did not understand from the content of the article if there are pollution indicator species. What physiological traits are characteristic of species from polluted sites?

Comments on the Quality of English Language

I recommend the authors to check the quality of the English language and especially the meaning of the sentences from a scientific point of view.

Author Response

Materials and Methods section. Lines 120-125 - Table 1 would be better suited for the Results section. Also, based on the recorded parameters, a classification of the five sampling sites should be made so that the reader can understand more easily which are the most polluted areas. What are the parameters that indicate anthropogenic pollution?

Response. We think the physico-chemical parameters results are not a main subject of the work. Therefor we put it in material and methods chapter as area description. It is very common pattern for ecological study papers. All chemical and physical parameters indicate river environmental state e.g. low contenst of oxygen, high value of conductivity or TDS or suspended solids. All the factors indicate anthropogenic impact.

Discussion section. Sometimes the authors use a vague, confusing expression, such as the text on lines 267-275. We did not understand the mechanism by which anthropogenic factors negatively influence the respective taxa. Anthropogenic influence and pollution are generous and very broad terms. I would suggest the authors to coherently examine each factor and its influence on the analysed species.

Response: According to reviewer no. 3 and another reviewers we added some descriptions about anthropogenic perssure more specyfc way. We changed the main sentence on „However environmental changes such as river regulation, dam reservoirs and water pollution caused by human created new microhabitats that are not typical for spatial natural course of river.”

Lines 275-276. I ask the authors to be more specific about the microhabitats created by man. Which are these? How do they influence the analysed species?

Response: We added the sentence: These microhabitats may be small pools or unwashed fine organic matter accumulations along a longer section of the river.

Lines 277-286. The authors describe the transition from spring to summer and the succession of different species. How does anthropogenic activity influence this succession which at first sight seems to be natural?

Response: As we wrote phenological changes were very much responsible for the changes in the communi-ties, which mainly relate to changes in thermal conditions and sun exposition. Therfore the influence of human is the same in the Sommer, Spring and autumn. It is natural according to natural increase of temperature.

Lines 297-298. What is the scale considered by the authors when they talk about microhabitat? Millimeters, centimeters?

Response. It means that local conditions characterised for studied section created invertebrata comminities in more extent than big catchment area.

Line 313. It is a confusing wording. What do the authors understand more precisely by this statement? I ask the authors to clarify.

Response. As we indicated in cited papers, zooplankton amount can reach a rapid growth in small dam reservoirs even, which occurr in Dzieżęcinka riber bed. It is a typical pattern for zooplankton development in rivers.

Lines 314-316. Again it is a confusing phrase to understand. Additional clarifications please!

Response: we added the sentence: Due to the lower abundance of feeding fish and macroinvertebrates or additionally undeveloped macrophytes in spring, zooplankton could drift long distances.

Conclusions section.

Lines 324-325. Please explain the statement made by you! Why do changes in zooplankton composition occur rather in time than in space? Does anthropogenic activity manifest itself only in certain periods of time? I did not understand from the content of the article if there are pollution indicator species. What physiological traits are characteristic of species from polluted sites?

Response: This conclusion was deleted.

Round 2

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

For the canonical correspondence analysis, the authors said that they included the percentage of explanation in the text, however the values they reported were the eigenvalues which are different from the percentage of explanation. The percentage of explanation is more interpretable than the eigenvalues alone. In addition, the canonical correspondence analysis graph is still very difficult to interpret, so I leave it up to the editor to decide whether to publish this graph or to ask the authors for a new correction.

Author Response

I apologize for the misunderstanding. We added information about Eigenvalues and Proportion Explained in the text.

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Dear authors,

I have carefully read your answer. Some aspects are still unclear, but in general the quality of the manuscript has improved.

Comments on the Quality of English Language

The quality of the English language is satisfactory, but the authors should carefully reread the manuscript to detect minor spelling mistakes.

Author Response

Thank you for your opinion, the authors made every effort to ensure that the article was written correctly.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study is devoted to phytoplankton, zooplankton and macroinvertebrates of a small river Dzierżęcinka from the middle flow to the inlet in the Jamno Lake. 

 Main comments

The article does not contain any, even general, data on the species composition of phytoplankton, zooplankton and macroinvertebrates of the studied river. It is not clear what species richness and number of studied groups of organisms were at the stations. It is not clear which macrotaxa were taken into account in each of the groups of organisms (at least which orders?). The fact that only 11 phytoplankton taxa were found in all samples raises doubts about the quality of sample processing. This is a very strange situation when there found 11 taxa (species?) of phytoplankton and 72 species of zooplankton. There is a strong feeling that the phytoplankton samples were not processed well enough.

The authors divide zooplankton into pelagic and littoral. On basis of which features is this division? What is the composition of these zooplankton groups, at least at the level of macrotaxa?

 All figures are inserted into the text in very low quality. For example, it is impossible to understand what is on Figures 2-4. It is impossible to read the signatures of the factor vectors and points, so I cannot assess the adequacy of the description of these figures in the text.

 The article as presented cannot be published in the journal Water and must be rejected. The article should be completely revised and resubmitted.

 Comments to the different sections of the article

Introduction

1. The introduction must be supplemented with information about the phytoplankton flora and fauna of zooplankton and macrozoobenthos of the studied region in general and the Dzierżęcinka River in particular (if such studies have taken place).

2. The concept of river continuum is not the only one that describes the natural state of river communities. There is also a hypothesis suggesting a discrete location of the communities of benthic fauna in different biotopes. In general, everything depends on the scale of consideration of the natural ecosystem. Thus, the deviation of the structure of the studied communities from the concept of continuum does not yet indicate their disruption by the anthropogenic factor.

 Materials and methods

1. It is necessary to indicate how many samples were collected for each group of organisms.

2. In Figure 1A should be provide a coordinate grid with latitude and longitude labels. There seems to be some kind of grid on this Figure, but it is in such poor quality that I can’t judge what it is.

 Results

1. There is no data on the composition of flora and fauna, as well as the species richness and abundance of organisms in the studied river. This does not make it possible to assess the validity of the authors' conclusions. This data should be presented in the article.

2. 11 species of phytoplankton for such a number of samples is very, very few. I believe that the samples were bad processed.

3. Figures 2-4 are of poor quality, it is not clear that is on them.

4. Table 2 is not needed. There is no need to provide similarity index values for all compared pairs. The most important of these meanings should be discussed in the text.

5. Occasionally the text contains Latin names for genera of organisms. According to the taxonomic code, genus level Latin must be written in italics.

 Discussion and Conclusion

1. Both these parts must be rewritten in accordance with the modified Results part.

2. The Discussion contains general conclusions about plankton and benthic fauna, but no specifics in connection with data on real communities in the studied river. It is necessary that the discussion will be written in connection with the materials of study.

3. The concept of river continuum is not the only one that describes the natural state of river communities. There is also a hypothesis suggesting a discrete location of the communities of benthic fauna in different biotopes. In general, everything depends on the scale of consideration of the natural ecosystem. Thus, the deviation of the structure of the studied communities from the concept of continuum does not yet indicate their disruption by the anthropogenic factor.

  The article in the present form should be rejected.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have collected a large amount of material, but the presented manuscript requires improvement in most sections. The purpose of the study was to study the patterns of spatial distribution of phytoplankton and aquatic invertebrates in an environment characterized by significant anthropogenic stress. The authors' conclusions that benthic macroinvertebrates and coastal zooplankton showed a strong relationship with local conditions, while, in contrast, pelagic zooplankton and phytoplankton showed a strong relationship with drift and its production in the upper reaches, also requires substantiation.

It should be noted that to differentiate changes in the taxonomic groups of phytoplankton, zooplankton and macroinvertebrates associated with anthropogenic stress and natural seasonal and daily dynamics, the influence of flow speed, the introduction of alien organisms, artificial changes in the hydrological regime, makes the formulation of this problem complex and legitimate.

 

Notes:

 

1. Provide a map of the research scheme and sampling stations in a clearer resolution “Figure 1. Map of sampling sites. A – localization of Dzierżęcinka River in north-western Poland, B – catchment of 98 Dzierżęcinka River, C – sampling sites along the river and in the lake.” Geographical locations are not indicated by numbers. Also give Figures 2-4 in higher resolution.

 

2. Clarify and provide a more detailed methodology, taking into account

- sampling stations, whether vertical distribution was included.

- daily dynamics, which is important for sampling phytoplankton, due to vertical migration.

- seasonal dynamics taking into account the hydrological regime of lines 116-118 “Macroinvertebrates were collected in April, May, August and October of 2022 by method kick sampling (60 sec.) taking into account all microhabitats at the site, and adjusting the sampling time from the habitat to its area. All organisms were stored in the buckets, samples were flooded with 96% alcohol and then sorted in the laboratory."

 

3. I propose to include a graph of the ratio of taxonomic groups of phytoplankton, zooplankton and macroinvertebrates by season in the main material of the article on the analysis of data presented in additional materials on diversity and biomass.

 

The study can be considered relevant, but significant revision of the manuscript is required.