Dynamic Characteristics and Environmental Driving Factors of Phytoplankton Communities in Plateau Rivers: The Case of the Lhasa River

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article deals with the interesting topic of phytoplankton analysis and the factors determining its structure. Knowledge of the composition and dynamics of change of phytoplankton is crucial for assessing the functioning of aquatic ecosystems.  I recommend the article for publication after taking into account the following comments.

1) The time range defined in the paper is misleading: from September 2019 to March 2021. This notation suggests continuity of data over this period and in fact there are only four measurements.

2) There are two large power plants on the river under study: the Zhikong and the Pangduo. Please describe in detail their role in the context of the subject under study. What is the spatial extent of their impact on phytoplankton? How is the seasonality of change dependent on energy production?

3) What is the depth of the parameters measured directly in the field (pH, WT, and conductivity). Does changing the depth of measurement of these parameters affect the results?

4) The authors have omitted the key factor of the presence of ice (this is especially for the two dates November 2020 and March 2021). Please refer to the results obtained on these dates and the effect of ice (if present) on species composition and other phytoplankton characteristics.

5) ....In the downstream section of the Lhasa River, which flows through Lhasa's urban area, pollutants from urban activities likely influence the river's water quality, increasing nitrogen concentrations.... This statement does not fully explain the nitrogen issue. As is well known, internal recharge from sediment may be key in this regard. Please address these issues for the river under consideration.

6) In the Conclusions chapter, please point out the limitations of the studies carried out.

Author Response

Please see attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

El manuscrito presenta información sobre el comportamiento dinámico del fitoplancton durante el período 2019 a 2021. Está organizado de manera coherente y sistemática. Aunque podría obviar algunas cuestiones que se describen a continuación.

The manuscript presents information on the dynamic behavior of phytoplankton during the period 2019 to 2021. It is organized in a coherent and systematic manner. Although it could miss some issues described below.

1.    En la L26 se mejoró la redacción de “tendencia decreciente de aguas arriba a aguas abajo”.

1. In L26, the wording of “decreasing trend from upstream to downstream” was improved.

2. L59. Los autores deben especificar a qué vitaminas se refieren. Además, evitar el uso de “etc.”.
2. L59. Authors should specify which vitamins they are referring to. Also, avoid using “etc.”.

3.    L60-61, que podrían especificarse mejor, parecen contradecir L52-55. Mejorar la redacción.
3. L60-61, which could be better specified, seem to contradict L52-55. Improve the wording.

4.    L78. “Una investigación reciente sobre el fitoplancton en el río Lhasa ha cobrado impulso”, esta línea está incompleta, ¿a cuál se refiere? Mejorar la redacción.
4. L78. “A recent investigation on phytoplankton in the Lhasa River has gained momentum” – this line is incomplete, which one does it refer to? Improve the wording.

5.    L90. El término “parámetros fisicoquímicos” se confunde con “parámetros físicos y químicos”. Se cambia a “físicos y químicos” en todo el manuscrito.
5. L90. The term “physicochemical parameters” is confused with “physical and chemical parameters”. It is changed to “physical and chemical” throughout the manuscript.

6.    L90. “Calidad del agua” y en L92 “Calidad del agua”, se sugiere mejorar la redacción, redundancia de términos.
6. L90. “Water quality” and in L92 “Water quality”, it is suggested to improve the wording, redundancy of terms.

7.    L99. “Km2”, lo correcto debería ser km2.
7. L99. “Km2”, the correct wording should be km2.

8.    En la Tabla 1, las unidades de elevación
8. In Table 1, the elevation units

9.    En L136, indique Pi
9. In L136, indicate Pi

10. La unidad de conductividad debe ser “mS/cm”, también poner Dureza Total.
10. The conductivity unit should be “mS/cm”, also put Total Hardness.

11. En la Fig. 3. “10^5”, presente apropiadamente.
11. In Fig. 3. “10^5”, present appropriately.

12. Véase las figuras 4a y 4b, y adapte el texto del punto 2.2.4.
12. See figures 4a and 4b, and adapt the text of point 2.2.4.

13. En la Tabla 4, complete el análisis de comparación múltiple de los parámetros.
13. In Table 4, complete the multiple comparison analysis of the parameters.

14. En L275. “El OD en la cuenca del río Lhasa varió de 3,77 a 15 mg∙L-1”, esto no es evidente en la Tabla 4; además, los rangos no corresponden al valor máximo.
14. In L275. “The DO in the Lhasa River basin varied from 3.77 to 15 mg∙L-1”, this is not evident in Table 4; Furthermore, the ranges do not correspond to the maximum value.

15. L415-419. ¿Cuál es la razón de estos cambios y qué los influye, aspectos intrínsecos o extrínsecos? Los autores deben justificarlo.
15. L415-419. What is the reason for these changes and what influences them, intrinsic or extrinsic aspects? The authors must justify this.

Author Response

Please see attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

This manuscript explores the dynamic characteristics and environmental factors driving phytoplankton communities in the Lhasa River Basin. The study aims to connect theoretical research on high-altitude aquatic ecosystems with practical data to support ecological monitoring and conservation efforts in the region. While the topic is intriguing and relevant, there are several areas where the manuscript could be improved. My suggestions are as follows:

 

1. The abstract is informative but overly long, exceeding the 200-word limit set by the author's guidelines. Consider condensing it by focusing on the main ideas and removing less critical details. 

2. The introduction provides a solid overview of phytoplankton's ecological importance and the unique challenges of the Lhasa River. However, it would benefit from a clearer connection to global research issues and the inclusion of more recent references to reflect advancements in this field. 

3. The materials and methods section explains the sampling procedures well but could be improved with more details about the choice of specific seasons and locations. Additionally, provide a clearer explanation of the statistical methods, particularly the use of RDA and CART models, to enhance reproducibility. 

4. The results section presents a comprehensive analysis of phytoplankton abundance, diversity, and environmental factors, along with clear temporal and spatial trends. However, some figures (e.g., Figures 2, 3, 5, and 6) are of low resolution and could use more descriptive labels to allow for easier interpretation. Also, consider emphasizing key findings, such as the dominant drivers for each river section. 

5. The discussion effectively ties the findings to prior research and highlights the influence of environmental factors on phytoplankton. To enhance this section, draw stronger comparisons with similar plateau rivers globally. Expand on the impacts of human activities, like urbanization and hydropower, on environmental stability, and discuss how the study's findings could inform conservation efforts or policy decisions. 

6. In the conclusion, include specific recommendations for monitoring and preserving the Lhasa River ecosystem. Additionally, highlight the broader implications of this research for other plateau river systems around the world. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript is suitable, I recommend it for publication. I noticed minor flaws, which the authors will not have much trouble correcting.

 

Abstract. I think the abstract should be strengthened by indicating the geographical scope of the research.

Lines 20-21: “In this study, we focus on phytoplankton in the Lhasa River Basin”. I recommend to add “including riverbed from the source to the river mouth, five largest tributaries and two adjacent wetlands”.

 

Line 24: “… 127 species of phytoplankton from seven phyla were identified...” - In this number you include “phylum Cyanophyta”, which are prokaryotes and according to modern classification should be classified as bacteria (Cyanobacteria). It would be better to formulate it something like: “127 species of phytoplankton from six algal phyla were identified, as well as Cyanobacteria”.

 

I also recommend checking all mentions of blue-green algae in the text and correct their systematic affiliation.

 

Lines 25-26: “The spatial distribution of phytoplankton showed a decreasing trend from upstream to downstream…” - The spatial distribution of phytoplankton DIVERSITY showed a decreasing trend…

 

Lines 27-28: “Redundancy analysis revealed that in the upstream reaches, phytoplankton were primarily influenced…- what do you mean: phytoplankton DIVERSITY or phytoplankton ABUNDANCE? Which of these parameters did you analyze? It is not specified in the Materials and Methods section or in the results.

 

Line 47: “…autotrophic water bodies…” – want do you mean? I am not familiar with this term.

 

Lines 81- 82: “…the primary factors influencing the community structure in the Lhasa River Basin[22]….” - The referred article is absent at the Journal site, and the issue doesn't exist. https://www.sciencedirect.com/journal/acta-ecologica-sinica/issues

Line 105: “…dense rivers…” – “river network”?

Lines 109-111: “…Field surveys was conducted, from 2019 to 2021, specifically in September 2019, June 2020, November 2020, and March 2021” - over THREE years.

Figure 1: It is desirable to indicate the boundaries of upper, middle and lower reaches. For example, by painting in different colors the parts of the rivers corresponding to groups S1, S2, S3, S4 and S5… S10.

1.2 Phytoplankton collection and analysis

Line 127: could you specify, what is Rugo’s reagent? A link to the source where it is described would be desirable.

Lines 132-142: References to sources describing these indices are needed.

Line 136: “Shannon-Wiener diversity index: H’ = −Σ𝑃𝑖𝑁𝑠𝑖 = 1ln𝑃𝑖” - Specify what means 𝑃𝑖 and 𝑁𝑠𝑖.

Line 138: “Mcnaughton dominance coefficient” - first, a reference to the source where this index is described is needed. Second, clarify, please, is this an index for a sample, sampling site or for the entire water body? How was fi frequency calculated? According to Mcnaughton (1967), the dominance index is calculated differently: "Dominance in the grasslands was related according to diversity according to Y=138 - 6x6, X where Y is the percentage of the peak standing crop contributes by the two most important species and X is the number of species recorded from 100 random points on the two transects..."

MCNAUGHTON, S. J. (1967). Relationships among Functional Properties of Californian Grassland. Nature, 216(5111), 168–169. doi:10.1038/216168b0

Table 2. Sulfateion, Nitrateion, Chloridion – must be written in two words

Line 156: “A redundancy analysis (RDA) of the relationship between phytoplankton and environmental factors…” - phytoplankton diversity or phytoplankton abundance?

 

Lines 165-167 and further: 41.73% 32.28%; 11.02%; 5.51% - Accuracy to hundredths is excessive. Tenths or even whole values are sufficient.

 

Line 166: Cyanophyta – change to Cyanobacteria.

 

Line 168 Pyrrophyta – this is outdated concept of taxon, should be replaced with Dinophyta.

 

Lines 169-170: “The four surveys recorded 51 species from 5 phyla, 54 from 5 phyla, 57 from 6 169 phyla, and 57 from 7 phyla” – It's not clear, there were 127 species, right? What about the rest?

 

Figure 2. Spatial and temporal distributions of phytoplankton species in the Lhasa River Basin…» - distributions of phytoplankton diversity in the Lhasa River …

 

Line 206: Pyrrophyta – replace with Dinophyta.

 

Line 231: Cyanophyta – replace with Cyanobacteria.

 

Lines 236-240: “…Sellaphora sp., Encyonema sp., and Synedra ulna as endemic dominant species…”; |…Pinnularia interrupta was recognized as an endemic dominant species…”, “…Chroomonas acuta were identified as the endemic dominant species….” – Why do you use the term “endemic”? All mentioned species are widespread.

 

Synedra ulna – according to the Algaebase this name is currently regarded as a synonym of Ulnaria ulna (Nitzsch) Compère (https://www.algaebase.org/search/species/detail/?species_id=31527).

Synedra acus - this name is currently regarded as a synonym of Ulnaria acus (Kützing) Aboal (https://www.algaebase.org/search/species/detail/?species_id=34471).

Chroomonas acuta - this species is currently regarded as a synonym of Komma caudata (L.Geitler) D.R.A.Hill ((https://www.algaebase.org/search/species/detail/?species_id=29972).

 

Table 3. - Synedra ulna, Chroomonas acuta - replace with the name accepted in modern taxonomy.

 

Lines 324, 333, 339, 407, 415, 459, 489, 494, 522 etс - Cyanophyta – replace with Cyanobacteria.

 

Lines 326, 341 etc: Pyrrophyta - replace with Dinophyta.

 

Lines 365-366: “When TH <55 mg/L, Mg²⁺ ≥8.6 mg/L, and SO₄²⁻ <42 mg/L, the total 365 abundance was 46,639 cells/L. However, when TH ≥19 mg/L, the abundance was 35,244 cells/L”. – If the second sentence is a clarification of the first one (TH ≥19 mg/L with the same Mg and SO₄ values as in the first sentence), then for clarity it is better to separate these sentences not with a period, but with a semicolon.

 

Line 457, 528: Synedra sp. - Ulnaria?

 

Lines 520-521: “total of 127 phytoplankton species belonging to seven phyla were identified” – As Cyanobacteria is not algal phylum reformulate, please, this sentence. …to six algal phyla and Cyanobacteria…

Lines 522-523: Pyrrophyta replace with Dinophyta.

Line 606: the referred article #22 ( Jun S.; Wang D.-B.; Zhou J.-S.; Bai X.-Y.; Bai K. Community structures of phytoplankton and its relationship with environmental 606 factors in the Lhasa River. Acta Ecologica Sinica) is absent at the Journal site, and the issue doesn't exist. Check, please.

 

Attachment: List of phytoplankton in Lhasa River

The table contains outdated names for a number of species, and there are spelling errors in some names. In international journals, it is customary to check the taxonomy against the AlgaeBase https://www.algaebase.org/, where changes are promptly made in accordance with new knoledge. Adhering to a single taxonomy is important for the comparability of data from different regions.

Citing AlgaeBase:

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 19 January 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on … (date of search).

 

Names that need to be corrected:

 

Cyclotella bodonica - this species is absent in the AlgaeBase. Check, please, the name - bodanica?

Cyclotella ocellata - this name is currently regarded as a synonym of Pantocsekiella ocellata (Pantocsek) K.T.Kiss & Ács.

Cymbella naviculiformis - this name is currently regarded as a synonym of Cymbopleura naviculiformis (Auerswald ex Heiberg) Krammer.

Navicula capitata - this species is absent in the Algaebase. Check, please, the name.

Stauroneis phoeicenteroa – change with Stauroneis phoenicenteron (Nitzsch) Ehrenberg 1843.

Synedra tabulata - currently regarded as a synonym of Tabularia tabulata (C.Agardh) Snoeijs.

Synedra ulna - regarded as a synonym of Ulnaria ulna (Nitzsch) Compère.

Ankistrodesmus angustus - this name is currently regarded as a synonym of Monoraphidium contortum (Thuret) Komárková-Legnerová.

Oocystis solitaria - this name is currently regarded as a synonym of Neglectella solitaria (Wittrock) Stenclová & Kaštovský.

Scenedesmus dimorphus – to be replaced with Tetradesmus dimorphus (Turpin) M.J.Wynne.

Scenedesmus acuminatus - a synonym of Tetradesmus lagerheimii M.J.Wynne & Guiry.

Scenedesmus bijuga - do you mean Scenedesmus bijugatus? This name is currently regarded as a synonym of Tetradesmus obliquus (Turpin) M.J.Wynne.

Scenedesmus quadricanda - This name is not listed in the Algaebase, maybe you mean Scenedesmus quadrialatus?

Selenastrum bibraianum - Messastrum gracile (Reinsch) T.S.Garcia.

Tetraedronoidrae - ?

Uronema confervicolum - Uronema confervicola Lagerheim 1887.

Synuraceae urelin - ???

Chroomonas acuta - Komma caudata (L.Geitler) D.R.A.Hill.

Chroomonas acuta uterm - ??? Chroomonas acuta? See above.

Cyanophyta – 14 reps – Cyanobacteria.

Lyngbya hieronymusii - This name is currently regarded as a synonym of Limnoraphis hieronymusii (Lemmermann) J.Komárek, E.Zapomelová, J.Smarda, J.Kopecký, E.Rejmánková, J.Woodhouse, B.A.Neilan & J.Komárková.

Oscillatoria princes - Oscillatoria princeps Vaucher ex Gomont 1892.

Euglena acus - regarded as a synonym of Lepocinclis acus (O.F.Müller) B.Marin & Melkonian.

Euglenophyta sp. - Euglenophyta gen. sp.

Author Response

Please see attachment

Author Response File: Author Response.pdf