Influence of Intensive Agriculture on Benthic Macroinvertebrate Assemblages and Water Quality in the Aconcagua River Basin (Central Chile)

Round 1

Reviewer 1 Report

The manuscript (water-1077509) presents a study of aquatic invertebrate community in the Aconcagua River system, which is disturbed by intensive agriculture.  Due to water scarcity, which is a consequence of climate change and direct human impact in the form of diversion of water for irrigation and its pollution at the same time due to intensive agriculture, this article is of great interest to local services for the protection of environment and scientific audience from local population.

However, the manuscript includes several shortcomings and should be improved. I suggest the authors to thoroughly elaborate the manuscript according to concerns and comments described below.

Authors performed numerous statistical analyses on samples, but on the other hand it is not clear, which were the determination levels of the macroinvertebrate taxa included in the “species”-data matrix for these analyses. Were these species, genera, families or mixed? The authors mention names of species, families in the discussion. For the comparisons of diversity indices as well as other analyses the levels should be the same (all families, all genera, higher taxa). I suggest the authors to provide more information on the taxonomic level used in analyses in Methods.

Authors are suggested to send their manuscript to English-editor to improve the language.

The Figures and Tables should be placed in the suitable positions within the Chapters and sub-chapters, close to their first mention in the text.

Tables can contain only horizontal lines. All figures need improvements (suggestions are described below).

 

The present title is not clear enough. I suggest to change it, for example: “Influence of intensive agriculture on the assemblages of aquatic macroinvertebrates and water quality in the Aconcagua River Basin (central Chile).”

 

Minor comments:

Abstract:

I suggest to delete the first sentence, since it is a general statement.

Ln 8: please use water temperature not just temperature, because in the context of altitude gradients in air temperature are also significant.

Ln 10: replace % with the words proportion of.

I suggest to replace the words richness taxa with : the number of taxa

Introduction:

Please add some more references.

 

Methods

Ln 75: Aconcagua River is 5rd Strahler and has a longitude of 142 km . .

The Aconcagua is 5^th order river according to Strahler and is 142 km long.

Ln 79: 145 intakes – 145 inflows

Ln 103: Has the mentioned city Waste-water treatment plant for municipal sewage?

The absence could significantly influence the water quality.

Ln 109: were collected – were sampled

Ln 114: please shorten the sentence:  ….. then taken to the Laboratory.

Ln 123: water temperature

Ln 135: Please change EPT richness to: number of EPT taxa

Ln 133: Explain within this paragraph what was the level of the taxa used in the analyses (see comment above)

Ln 149: macroinvertebrate community composition

Ln 154: Which variable in pair that correlated was removed or both variables?  

Results:

Ln 163:  Please write the lowest value before the highest

Ln 177: Please write numbers in all cases (e.g. fifty-six)

Define the taxa.

Ln 183: were found

Ln 270: woody residues – Do the stoneflies really feed on wood residues? In European watercourses they feed on leaf-litter (shredders) or they feed on other invertebrates (predators) such as mayflies or dipterans.

 

Ln 308: please use the right symbol for micrograms

Table 2: Lines 7 and 8: use the abbreviations BOD and COD instead DBO and DQO.

The letters are very small here. I suggest to put this table into appendix.

 

Figure 1 a: I suggest to remove the dark shading of neighboring countries and leave them white.

 

Figure 2: land uses are not readable. You used 37 + 15 categories/colors in this figure.

Please merge some of the similar land uses in one category (different types of forests, orchards etc.) and reduce their number.

 

Figure 3: Such comparisons mostly include also the results of suitable post-hoc tests to show the statistically significant differences between these types. Please improve.

Please correct the last sentence in caption: …between level agricultural disturbed scores …

 

Figure 4: improve the readability of these figures:

Gray squares are hardly visible in comparison with other symbols. Explain the abbreviations used in figures in the caption below.

 

Author Response

Please see in PDF reviewer #1

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript Number: water-1077509

Title: Variation in macroinvertebrate assemblages and water quality in a highly agricultural basin of central Chile

Article Type: Article

Comments for the Authors:

The author has assessed natural variation in themacroinvertebrate assemblages (MIB) and water quality in one of the main basins with the largest agricultural activities in Chile (Aconcagua River Basin). The topic is interesting for the journal's readership. Also, the methods are right and enough and the results are very good and reasonable. However, in my opinion some issues should be addressed and improved before the manuscript can be published.

Detailed comments:

1. Abstract: please add more interesting and quantitative findings from your work because you got many in this study. Maybe that is more important. For example, what kind of “…a strong influence…”? Please give quantitative results.
2. Keywords: please add “MIB” because your study also focused on the change of MIB.
3. Lines 61-65: please rewrite this part according to the logical relationship.
4. Lines 71-73: please add the time period.
5. Tables: please adjust the table according to the regulation of the WATER.
6. It is better to discuss the uncertainty about your results.
7. Please check and modify the references carefully according to the regulations of the WATER.

In summary, the paper is very interesting and good. I would like to recommend this paper to be accepted after minor revision.

Author Response

Please see in PDF reviewer #2

Author Response File: Author Response.pdf

Reviewer 3 Report

Este trabajo está bien estructurado e interesante. Señalo algunas deficiencias detectadas para mejorar el documento:

• En la Tabla 1 y Tabla 2. El Código de PO20. ¿Es correcto? ¿Es posible que sea PO10? como se indica en la Figura 1 y la línea 99.
• En la Tabla 1. Los datos de elevación para los puntos AC20, PU10 y PO20 (o PO10) se cambian, como se indica en las líneas 98 y 100.
• En la línea 122, se indica que en cada lugar se evaluaron las condiciones del hábitat y 26 parámetros fisicoquímicos, reflejados en la Tabla 2, y no en la Tabla 1. En cuanto a la nomenclatura, es recomendable utilizar los mismos términos y la misma cantidad. de parámetros, ya que la discusión, en la línea 282, indica que se ha recolectado información de 28 variables ambientales. ¿Es 26 o 28? ¿Son parámetros fisicoquímicos o variables ambientales?
• Si los sitios de muestreo se agrupan en 3 tipos: A) las estaciones con mayor altitud y menor perturbación (JU, JU10, BL20 y AC10); B) estaciones intermedias (AC20 y PU10); y C) las estaciones con menor altura y más perturbadas (PO10, AC30 y AC40). ¿No sería más conveniente que la Tabla 2 se estructurara según esas características o ese agrupamiento? lo que permitiría un mejor y más cómodo seguimiento de la discusión de los resultados. El orden de las columnas conlleva criterios específicos, que no discuto con los autores, pero no ayudan a seguir la discusión de la investigación.
• En las líneas 154-157 se indican las variables que se eliminan en las diferentes estaciones del año, por tener una alta correlación, ¿podrían ir acompañadas de los valores de r de Pearson obtenidos?

Author Response

Please see in PDF reviewer #3

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Manuscript ID: water-1077509

The manuscript has been improved, but there are still some corrections to be performed. I suggest the authors to consider the comments described below and continue with improvement.

comments:

It is not clear, which were the determination LEVELS of the macroinvertebrate taxa INCLUDED in the “species”-data matrix FOR STATISTICAL ANALYSES. Were these species, genera, families or mixed? For the comparisons of diversity indices as well as other analyses the levels should be the same (all families, all genera, higher taxa).

I understand the authors and I think the determination is sufficient and is not a problem. But, what I wanted to point at with this concern was the same taxonomic level in the taxa matrices used for the analyses. It is only correct to use the taxonomic level consistently through all of the samples, e.g. all invertebrates included only at the level of families or only at level of genus or at higher taxonomic level in one table subjected for analyses. Since you compare also the diversity indices – Number of taxa, Diversity (H’) and you performed statistical analyses this is mandatory.

The same taxonomic level is needed for all samples, if you want to compare the results in a sensible way. Please explain and/or correct.  

 

Figure 2: land uses are not readable. Please improve Figure 2 to more readable form. As I wrote in previous round over 50 categories in similar colors could not be distinguished. Please merge some of the similar land uses in one category (different types of forests, orchards etc.) and reduce their number.

What did you mean with direct land-use is this land-use adjacent to the watercourses, which has more direct influence? Is indirect land-use actually land-use in wider catchment area? Please explain these terms. I advise you to compare you land uses with descriptions in Zelnik et al. 2020, Water; doi:10.3390/w12020345.

Author Response

The manuscript has been improved, but there are still some corrections to be performed. I suggest the authors to consider the comments described below and continue with improvement.

comments:

It is not clear, which were the determination LEVELS of the macroinvertebrate taxa INCLUDED in the “species”-data matrix FOR STATISTICAL ANALYSES. Were these species, genera, families or mixed? For the comparisons of diversity indices as well as other analyses the levels should be the same (all families, all genera, higher taxa).

I understand the authors and I think the determination is sufficient and is not a problem. But, what I wanted to point at with this concern was the same taxonomic level in the taxa matrices used for the analyses. It is only correct to use the taxonomic level consistently through all of the samples, e.g. all invertebrates included only at the level of families or only at level of genus or at higher taxonomic level in one table subjected for analyses. Since you compare also the diversity indices – Number of taxa, Diversity (H’) and you performed statistical analyses this is mandatory.

The same taxonomic level is needed for all samples, if you want to compare the results in a sensible way. Please explain and/or correct.  

 

 R:  Thanks for the observations. The “taxonomic surrogancy” (i.e. the degree to which higher taxonomic levels portray species-level patterns) and the “taxonomic suffiency” (identifying organisms only to a level of taxonomic resolution sufficient to satisfy the objectives of a study) are accepted methods to assess the impact of pollution on biological communities, especially marine communities (Bertrand et al 2006). However, these methods can not be applied to all ecoregions and biological communities. We agree with Heino (2014) in that applying statistical analyses to the greater level of taxa could promote the loss of information about the response of the organisms to environmental variability.

 

The use of greatest levels of taxa can not be used without restrictions to infer relationships between communities and environmental effects (Heino 2014). We have identified organisms at different levels of taxa because, and as it is mentioned in lines 133-138, there are not sufficient keys for the identification of invertebrates in South America.

 

Several studies in rivers of the region have shown that parametric and no-parametric analyses, among others, are able to differentiate between natural and anthropogenic disturbances based on the level of macroinvertebrate taxa (e.g. Elgueta et al 2021; Fierro et al 2017, 2019, 2020; Novoa et al 2020). Thus, we strongly believe that our analyses are correct. We have re-written the text in line 151 to clarify the message: “The following macroinvertebrate assemblages metrics descriptors were calculated using the level taxa (such as Elgueta et al. 2021, Fierro et al 2019, Novoa et al. 2020), averaging all seasons for each sampling site”.

 

References:

Bertrand, F. Pleijel, G.W. Rouse. (2016). Taxonomic surrogacy in biodiversity assessments, and the meaning of Linnean ranks. Syst. Biodivers., 4 (2006), pp. 149-159

Elgueta, A., Górski, K., Thoms, M., Fierro, P., Toledo, B., Manosalva, A., & Habit, E. (2020). Interplay of geomorphology and hydrology drives macroinvertebrate assemblage responses to hydropeaking. Science of The Total Environment, 144262.

Fierro, P., Bertrán, C., Tapia, J., Hauenstein, E., Peña-Cortés, F., Vergara, C., ... & Vargas-Chacoff, L. (2017). Effects of local land-use on riparian vegetation, water quality, and the functional organization of macroinvertebrate assemblages. Science of the Total Environment, 609, 724-734.

Fierro, P., Valdovinos, C., Arismendi, I., Díaz, G., Jara-Flores, A., Habit, E., & Vargas-Chacoff, L. (2019). Examining the influence of human stressors on benthic algae, macroinvertebrate, and fish assemblages in Mediterranean streams of Chile. Science of the total environment, 686, 26-37.

Fierro, P., Ferrú, M., & Lara, C. (2020). Effects of forest conversion on the aquatic Coleoptera assemblage in Mediterranean-climate streams. Ecological Indicators, 111, 106043.

Heino, J. (2014). Taxonomic surrogacy, numerical resolution and responses of stream macroinvertebrate communities to ecological gradients: are the inferences transferable among regions?. Ecological Indicators, 36, 186-194.

Salvo, J., Valdovinos, C., & Fierro, P. (2020). Benthic macroinvertebrate assemblages of a stream-lake network in the upper zone of the trans-Andean basin of the Valdivia River (Chile). New Zealand Journal of Marine and Freshwater Research, 1-18.

Novoa, V., Rojas, O., Ahumada-Rudolph, R., Sáez, K., Fierro, P., & Rojas, C. (2020). Coastal Wetlands: Ecosystems Affected by Urbanization?. Water, 12(3), 698.

 

Figure 2: land uses are not readable. Please improve Figure 2 to more readable form. As I wrote in previous round over 50 categories in similar colors could not be distinguished. Please merge some of the similar land uses in one category (different types of forests, orchards etc.) and reduce their number.

R: Thanks for the observations. According with your suggestions, we improve Figure 2 with only 8 land uses. However, as we believe that the original figure is important, we leave it in appendix 1.

Figure 2. Map of land uses and sampling sites on the Aconcagua River Basin. Name of sampling stations in Figure 1, black circles, least-disturbed sites; lead squares, intermedium-disturbed sites; white triangles, most-disturbed sites by agricultural activities.

 

What did you mean with direct land-use is this land-use adjacent to the watercourses, which has more direct influence? Is indirect land-use actually land-use in wider catchment area? Please explain these terms. I advise you to compare you land uses with descriptions in Zelnik et al. 2020, Water; doi:10.3390/w12020345.

R: Thanks for the observations. We add a new Appendix 1 (original Figure 2). In the description of the appendix 1, according with your comments, we explained what is direct and indirect land uses.

 

Appendix 1. Map of land uses and sampling sites on the Aconcagua River Basin. Direct land use corresponds to land use adjacent to watercourses, principally anthropogenic land use. Indirect land use corresponds to land use in a wider catchment area. Name of sampling stations in Figure 1, black circles, least-disturbed sites; lead squares, intermedium-disturbed sites; white triangles, most-disturbed sites by agricultural activities.

Author Response File: Author Response.pdf