Threshold Response Identification to Multi-Stressors Using Fish- and Macroinvertebrate-Based Diagnostic Tools in the Large River with Weir-Regulated Flow

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is an interesting study, particularly differentiating between tipping point and management thresholds. Too often, systems are designed to remain below tipping point, when the management threshold is the critical one for protecting ecosystems. It is also valuable that you conducted this study over a long time period and compared model data to the actual ecological system.

The only change that would improve the paper in my opinion is clarification of the  first paragraph in section 2.2 Data collection design. IT is not clear if you measured each of the 16 survey points at the same time of year (point one on one date, point two on another date, point three of a third date), but kept the date consistent for each site for each year of the study or if you varied the date annually for each site with the date still being different for each survey point. Or, were the 16 survey point sampled on the same date each year with that date changing every year? I think this can be made more clear.

Also, perhaps add a table that lists the 29 individual variables, 18 individual variables describing habitat environment, and 19 variables representing hydrological characteristics stated in the 2nd paragraph of section 2.2.

In line 149, define RF.

Otherwise, this paper was well written and you gave a good explanation of model variables as they relate to the real system. many papers do not do this well, but you did.

Under section 3.2.1, in the first paragraph; can you explain why legally protected species, including endangered species, were left out?

 

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The researches were carried out on a very large area and over a significant period covering the proposed objectives of the project

Observations on biological factors were made during construction and during the exploitation period. Observations before the period of human intervention would have been useful in order to establish the natural state of ecosystems and the behavior of species before the construction period

Among the physicochemical parameters there are some important for determining the quality of aquatic ecosystems, but heavy metals are missing, which are considered strong stressors for biota

The list of observed species is very important and can reflect their response to stressors in an integrated way. It would have been useful to classify them according to sensitivity/adaptability in order to observe especially the evolution of less adaptable species

There are numerous articles that refer to important rivers that refer to indicator systems (WQI type) in which there are also guidelines on the weight of the negative impact of some parameters, as well as the impact of heavy metals, like: 

1.     Ira-Adeline Simionov, Madalina Calmuc, Catalina Iticescu, Valentina Calmuc, Puiu-Lucian Georgescu, Caterina Faggio, Stefan-Mihai Petrea, Human health risk assessment of potentially toxic elements and microplastics accumulation in products from the Danube River Basin fish market, Environmental Toxicology and Pharmacology 104 (2023) 104307, https://doi.org/10.1016/j.etap.2023.104307

2.     Maxim Arseni, Adrian Rosu, Madalina Calmuc, Valentina Andreea Calmuc, Catalina Iticescu and Lucian Puiu Georgescu, Development of Flood Risk and Hazard Maps for the Lower Course of the Siret River, Romania, Sustainability 2020, 12(16), 6588; doi:10.3390/su12166588

 The use of the GF technique is well exploited but there are still many limitations due to the incomplete list of physicochemical parameters observed and the consideration of all taxa with equal weights in the response to stressors.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, based on the results of consideration of the submitted manuscript, please provide clarifications on the following issues:

1. Is there a hydroelectric power station on the reservoir in question? Can the presented methods be used in this case?

2. Based on the research results, is it possible to recommend fish passage structures?

3. It is necessary to indicate the MPC values ​​for the indicators under consideration, such as COD, suspended solids, etc. for fishery reservoirs with references to current standards

4. Also provide data on the speed limit in the reservoir

5. Indicate the dimensions of indicators such as COD, suspended solids, etc. in Fig. 4,5

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Some of the initial recommendations were not taken into account.

It would have been useful to classify them according to sensitivity/adaptability in order to observe especially the evolution of less adaptable species

There are numerous articles that refer to important rivers that refer to indicator systems (WQI type) in which there are also guidelines on the weight of the negative impact of some parameters

The use of the GF technique is well exploited but there are still many limitations due to the incomplete list of physicochemical parameters observed and the consideration of all taxa with equal weights in the response to stressors

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

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Author Response File: Author Response.pdf