Environmental Variables Outpace Biotic Interactions in Shaping a Phytoplankton Community

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Manuscript ID: diversity-3108745

Title: Environmental variables outpace biotic interactions in shaping phytoplankton community

 

This paper covers an investigation on the main regulatory factors of phytoplankton community in a shallow reservoir in Brazil. Overall, this paper is well structured and shows good results of plankton interactions in non-eutrophic environments. However, some details must be taken into consideration before a possible publication in Diversity. Hope below comments will be able to help to further improve the paper.

 

Line 142: Please clarify if the range of rain is monthly or annual.

Line 144: The data of the reservoir present inconsistencies. Considering that the average depth is 3 m (the authors affirm this is the maximum depth) and the surface area is 26,000 m², the maximum volume the reservoir can reach is 78,000 m³. Please revise this. Checking this with Menezes and Bicudo (2006),

Line 690-693: In my opinion, this statement is not appropriate towards this study. This because the authors have not compared different approaches. Furthermore, conclusion section is very large, but some lines are repetition of the results instead of a conclusion.

English language must be improved by a native speaker towards a better readability. Some examples

 

Minor comments:

Line 15: Remove “(200 words)”.

Lines 180,181, 212 and other cases.: Citation in text must be carefully revised.

Lines 184-185: The written of inorganic nitrogen compounds must be revised.

Line 163: Multiparameter probe

Line 351: It is necessary to include the number of measurements (n = 6) in the table caption.

Lines 376 and 383: It is not necessary to write ANOVA in parentheses

Comments on the Quality of English Language

Moderate editing of language is required

Author Response

This paper covers an investigation on the main regulatory factors of phytoplankton community in a shallow reservoir in Brazil. Overall, this paper is well structured and shows good results of plankton interactions in non-eutrophic environments. However, some details must be taken into consideration before a possible publication in Diversity. Hope below comments will be able to help to further improve the paper.

 

Line 142: Please clarify if the range of rain is monthly or annual. Precipitation data is annual. This information was added to the text (Line 145-146).

 

Line 144: The data of the reservoir present inconsistencies. Considering that the average depth is 3 m (the authors affirm this is the maximum depth) and the surface area is 26,000 m², the maximum volume the reservoir can reach is 78,000 m³. Please revise this. Checking this with Menezes and Bicudo (2006). We checked with the references and found only data about maximum depth and area. We changed the text accordingly. (Line 147-148).

 

Line 690-693: In my opinion, this statement is not appropriate towards this study. This because the authors have not compared different approaches. Furthermore, conclusion section is very large, but some lines are repetition of the results instead of a conclusion. The text referring to the conclusion of the manuscript was carefully adjusted to make it clearer and more objective for the reader's understanding. A detailed review was carried out, which included the simplification of the sentences, the removal of repeated sentences of the results and the logical organization of the ideas presented. This adjustment process is intended to ensure that the final message of the manuscript is transmitted in a direct and efficient manner, facilitating the assimilation of the two main points and implications of the public study. With these modifications, it is expected that the conclusion of the manuscript will provide a more fluid reading and a more precise understanding of the results and contributions of the research. (Line 627-635)

 

 

English language must be improved by a native speaker towards a better readability. Some examples

 Minor comments:

Line 15: Remove “(200 words)”. This change was made to the text. (Line 15)

 

Lines 180,181, 212 and other cases.: Citation in text must be carefully revised. All citations in the text have been carefully reviewed.

 

Lines 184-185: The written of inorganic nitrogen compounds must be revised. The name and acronym of the nitrogen forms - nitrate, nitrite and ammonium - were modified. (Lines 188-189)

 

Line 163: Multiparameter probe. This change was made to the text. (Line 165)

 

Line 351: It is necessary to include the number of measurements (n = 6) in the table caption. This information was added to the text. (Line 365)

 

Lines 376 and 383: It is not necessary to write ANOVA in parentheses. This change was made to the text. (Lines 255, 261, 376, 383, 440, 447)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The aim of this manuscript is to study the influence of main factors (abiotic and biotic) on the formation of the phytoplankton community functional structure in a shallow tropical reservoir located in a conservation area (Brazil). Currently, studies based on the analysis of functional and morpho-functional groups of phytoplankton are widely used in monitoring aquatic ecosystems, as well as in assessing the relationship between phytoplankton communities and main environmental factors. Such studies are of particular value in water bodies with weak anthropogenic impact, which can serve as reference ones in assessing water quality.

There are some questions about the manuscript.

In Section 2.4 Samples and data analysis of plankton community

Lines 194-202. A method for calculating phytoplankton development indicators is presented. What counting chamber was used to count phytoplankton? What guidelines were used to identify taxa? It is not clear what the counting unit was – cell/colony/filaments?  To calculate biomass, the volume of the cell is determined. How was the biomass of filamentous and colonial algae determined? This needs to be specified.

In Section 2.5 Statistical analysis

Why was RLQ analysis chosen rather than RDA or PCA, traditionally used in such studies?

In Section 3. Results

Line 294. Differences in air temperature by month are indicated, but such differences (if any) by year of study are not indicated.

Table 3. Why were median values chosen? Was the data for these indicators non-normally distributed? It is necessary to clarify in the manuscript whether the data distribution was checked for normality.

Line 359: It states that "74 phytoplanktonic species" were detected. However, the Supplementary Material also lists species variations (for example, Desmodesmus armatus var. bicaudatus) or mentions cf. (confer), which suggests that the authors are not sure of the definition of this species. In addition, there are many taxa defined only to genus. It would be more correct to indicate "74 taxa", as was done with regard to the taxonomic diversity of zooplankton.

Lines 380-381. It was indicated that phytoplankton biomass was higher in the bottom layers, especially noticeable in December 2017 and March 2018. However, according to Figure 4, in March 2018, the biomass at the surface and at the bottom was the same, amounting to about 750 μg C L-1. It is necessary to check the data.

 It is known that zooplankton is also an important factor for phytoplankton. The work lacks RDA for phytoplankton, where both abiotic and biotic indicators were used as factors (in this case, density, zooplankton biomass and some indicators based on the functional characteristics of zooplankton).

Discussion is too long, better make it shorter and clearer.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

The aim of this manuscript is to study the influence of main factors (abiotic and biotic) on the formation of the phytoplankton community functional structure in a shallow tropical reservoir located in a conservation area (Brazil). Currently, studies based on the analysis of functional and morpho-functional groups of phytoplankton are widely used in monitoring aquatic ecosystems, as well as in assessing the relationship between phytoplankton communities and main environmental factors. Such studies are of particular value in water bodies with weak anthropogenic impact, which can serve as reference ones in assessing water quality.

There are some questions about the manuscript.

In Section 2.4 Samples and data analysis of plankton community

Lines 194-202. A method for calculating phytoplankton development indicators is presented. What counting chamber was used to count phytoplankton? What guidelines were used to identify taxa? It is not clear what the counting unit was – cell/colony/filaments?  To calculate biomass, the volume of the cell is determined. How was the biomass of filamentous and colonial algae determined? This needs to be specified. As asked, we changed the text and included more details about phytoplankton counts. (Lines 198 - 211).

 

In Section 2.5 Statistical analysis

Why was RLQ analysis chosen rather than RDA or PCA, traditionally used in such studies?

The RLQ method allows the joint analysis of three data matrices: an environmental matrix (R), a species attribute matrix (Q) and a species abundance matrix (L). This provides a more comprehensive view of the interactions between environmental variables, functional traits of species and their abundances. Ecologically, this analysis can directly relate the functional traits of species (such as size, shape, mode of reproduction, etc.) with environmental conditions and species abundances. This is crucial for understanding how different species traits respond to environmental variations. Consequently, such analysis facilitates the identification of complex ecological patterns and the relationships between species attributes and environmental variables.

Traditional methodologies such as PCA focus on variation in environmental variables or species abundances, while RDA integrates environmental variables with abundance data but does not directly incorporate species traits. In general, PCA does not test for relationships, and simply reduces the data dimensionality by correlating different variables. On the other hand, RDA tests for significant relationships between species abundances and predictors, but does not allow the test between species abundances and predictors mediated by species traits, which is what is done by the RLQ analysis. Since trait composition was an important part of our research, we found it sensible to include RLQ analysis which have already been applied to phytoplankton in other studies (Graco-Roza et al., 2022; https://doi.org/10.1111/oik.08677)

 

In Section 3. Results

Line 294. Differences in air temperature by month are indicated, but such differences (if any) by year of study are not indicated. The two-way Anova analysis revealed no significant difference in air temperature values ​​between years. This information was added to the text. (Lines 305-306).

 

Table 3. Why were median values chosen? Was the data for these indicators non-normally distributed? It is necessary to clarify in the manuscript whether the data distribution was checked for normality. The median is a statistical measure of central tendency, especially in contexts where the data may contain extreme values ​​or outliers. Extreme values ​​were observed mainly in relation to silica and dissolved inorganic nitrogen. For this reason, we prefer to use the median and coefficient of variation to better demonstrate the data set and its variability.

 

Line 359: It states that "74 phytoplanktonic species" were detected. However, the Supplementary Material also lists species variations (for example, Desmodesmus armatus var. bicaudatus) or mentions cf. (confer), which suggests that the authors are not sure of the definition of this species. In addition, there are many taxa defined only to genus. It would be more correct to indicate "74 taxa", as was done with regard to the taxonomic diversity of zooplankton.  This change was made to the text. (Line 369).

 

Lines 380-381. It was indicated that phytoplankton biomass was higher in the bottom layers, especially noticeable in December 2017 and March 2018. However, according to Figure 4, in March 2018, the biomass at the surface and at the bottom was the same, amounting to about 750 μg C L-1. It is necessary to check the data. The phytoplankton biomass data has been reviewed and is consistent with the findings presented in the article. I believe my previous mention of the months of December and March was unclear. The oscillation in phytoplankton biomass occurred at the surface in December, while at the bottom, it occurred in March. This clarification has already been incorporated into the manuscript. (Lines 376-388)

 

 It is known that zooplankton is also an important factor for phytoplankton. The work lacks RDA for phytoplankton, where both abiotic and biotic indicators were used as factors (in this case, density, zooplankton biomass and some indicators based on the functional characteristics of zooplankton).

The manuscript presents the RLQ analysis, which included zooplankton as a variable predicting the structure of the phytoplankton community. More details about this statistical analysis are in the topic answered above. RLQ analysis is a multivariate approach that allows simultaneously relating habitat characteristics, species functional traits and the composition of biological communities. In this analysis, zooplankton appears as a significant variable, indicating its important influence on the structure of the phytoplankton community (Figure 5).

Furthermore, our work used CWM-RDA (Community Weighted Mean - Redundancy Analysis) analysis, which incorporates the functional traits of both planktonic communities. The objective of this analysis was to observe the existence of interactions between the functional traits of phytoplankton and zooplankton, providing a more in-depth understanding of how these communities structure and interact functionally.

Given that the RLQ already included zooplankton as a variable and demonstrated its significance in phytoplankton community structure, performing an additional RDA analysis would be redundant. RLQ not only captured the essential relationships between zooplankton and phytoplankton, but also provided a comprehensive view of community structure based on environmental variables and functional traits. Thus, the RLQ analysis fully fulfills the role of evaluating zooplankton influences, making a separate RDA analysis unnecessary.

 

Discussion is too long, better make it shorter and clearer. Modifications were made to the discussion to reduce its length and improve clarity for the reader. The ideas were reorganized to follow a logical and cohesive sequence, excessive details that were not related to our hypothesis were removed, improving the readability and fluidity of the text. With these modifications, the discussion is expected to be more accessible and direct text. (Lines 502 - 624).

 

Author Response File: Author Response.pdf