The Danube Delta: The Achilles Heel of Danube River–Danube Delta–Black Sea Region Fish Diversity under a Black Sea Impact Scenario Due to Sea Level Rise—A Prospective Review

Round 1

Reviewer 1 Report

The topic in the paper is very important and interesting, however the approach is too descriptive even for a review paper, especially when considered that large portions of the manuscript are without references.

The whole text needs to be more concise.

Suggestions and comments are marked and given in the text of the manuscript.

Comments for author File: Comments.pdf

Author Response

Reviewer 1

The topic in the paper is very important and interesting.

Authors

Thank you very much for your kind appreciations and suggestions.

 

The approach is too descriptive even for a review paper,

The descriptive parts were synthetized and simplified as suggested.

 

large portions of the manuscript are without references.

references were added at all texts which are not belong to the authors

 

The whole text needs to be more concise.

The whole text was shortened and make more concise without to lose the main ideas.

 

Suggestions and comments are marked and given in the text of the manuscript.

All the marked suggestions and comments in the text were followed and solved accordingly to the reviewer 1 suggestions.

Please mark which area do you consider to be: the Danube-Danube Delta-Black Sea geo-ecosystem 

In terms of fish fauna historical exchanges and inter-influences all the Danube, its delta and the Black Sea are parts of this geo-ecosystem.

 

 

Reviewer 2 Report

 

1 -       The paper has some problems with syntax and the phrases used – this may not be a translation issue as much as an English writing issue – examples from the abstract include, the meaning of “natural safe buffer.” And the trailing end of a sentence, “sometimes by contrary”. In neither case is the meaning clear. The final sentence of the abstract is clunky – repair the syntax.

2-      Line 45 “circumstance of long term” is not clear

3-      Line 64-65 – the forces are not clear, what kind of forces?

4-      Line 83 “It is obvious”.. – not to a non-European readers or someone not familiar with the watershed in question

5-      Line 87-88 – serious syntax issue

6-      General style – the general information in the introductory paragraphs is rambling and is familiar to most readers, suggest tightening and moving quickly from point to point, focusing on the area under discussion

7-      There are a number of places where the reason an example is introduced is unclear. An example ca line 154 is the mention of the Hudson and the Aucilla Rivers in the US and the reference to historic patterns  of flooding. These two rivers are extremely different in terms of recent geological and hydrologic history as the Hudson watershed was glaciated in the last ice age and the Aucilla was not. Further, the geology of the lower reaches is also quite different, with the Hudson bordered by basalt cliffs. The example needs to be more obviously tied to climate and flooding.

8-      Line 187, “a come and go” the meaning is not clear

9-      The paper improves when it reviews recent studies of sea level relative to the Black Sea because it becomes more directed and more data-based. It would improve the paper to arrive at this point sooner.

10-   - One of the major issues with the current presentation is the lack of specific population data for each species.  Almost all are shown as in decline, but this is not backed by survey numbers.

11 – A way to improve the explication of long-term climate impacts would be to chose some cameo species from each of the major categories, and provide some short vignettes concerning the actual population trends – then separating climate from other factors – either synergistic or confounding – such as heavy fishing pressure. Providing a cameo on one of the critically endangered sturgeon species would interest many readers and would help to substantiate the overall conclusions of the paper. A possible strategy is to select a couple of the most endangered, a couple of the species in steep decline, and a couple that are resisting the stressors and provide somewhat more detailed documentation, then relate them to other species in similar circumstances.

12 – The paper is basically a review rather than presentation of new data. To be a successful review it needs to rise above the conclusion the speedy environmental change will have generally negative impacts on most of the species, and give this more nuance.  Surely the impacts are not all from the same phenomena.  Also, due to reducing competition for some species, other established species or invasive species may take advantage of the shifts. The article points to very few winners or adaptable species.  The paper largely lacks any discussion of potential restructuring of fish communities, and what this will look like. Would it be possible to draw a clearer picture of what the surviving communities will look like?

see the above, they are mixed with problems concerning meaning 

Author Response

Reviewer 2

Authors. Thank you for your suggestions end encouragements. All the suggested changes were made in the text.

1 -       The paper has some problems with syntax and the phrases used – this may not be a translation issue as much as an English writing issue – examples from the abstract include, the meaning of “natural safe buffer.” And the trailing end of a sentence, “sometimes by contrary”. In neither case is the meaning clear. The final sentence of the abstract is clunky – repair the syntax.

The paper was reviewed and corrected by the MDPI special English proofing service.

 

2-      Line 45 “circumstance of long term” is not clear

changed with: the long term 

 

3-      Line 64-65 – the forces are not clear, what kind of forces?

The phrase was changed: 

The Danube River-Danube Delta-Black Sea geo-ecosystem (Figure 1), with different biotops and biocoenoses assures and retains a smooth transition zone from fresh Danube river water to salt water of the Black Sea and represents a specific complex of unique ecosystems [27].

 

4-      Line 83 “It is obvious”.. – not to a non-European readers or someone not familiar with the watershed in question

It is obvious words were deleted.

 

5-      Line 87-88 – serious syntax issue

The paper was reviewed and corrected by the MDPI special English proofing service.

 

6-      General style – the general information in the introductory paragraphs is rambling and is familiar to most readers, suggest tightening and moving quickly from point to point, focusing on the area under discussion

The introduction part was tightened keeping information which form the red line of the text as much as was possible to not lose key logic elements which form the platform of the need of such a paper.

 

7-      There are a number of places where the reason an example is introduced is unclear. An example ca line 154 is the mention of the Hudson and the Aucilla Rivers in the US and the reference to historic patterns  of flooding. These two rivers are extremely different in terms of recent geological and hydrologic history as the Hudson watershed was glaciated in the last ice age and the Aucilla was not. Further, the geology of the lower reaches is also quite different, with the Hudson bordered by basalt cliffs. The example needs to be more obviously tied to climate and flooding.

The examples try to reveal planetary, regional and local examples which sustain the text. The example about the Hudson watershed was deleted as suggested.

 

8 - Line 187, “a come and go” the meaning is not clear

These words were deleted in a new rephrased context.

 

9-      The paper improves when it reviews recent studies of sea level relative to the Black Sea because it becomes more directed and more data-based. It would improve the paper to arrive at this point sooner.

The authors would like to reveal a continuum of information between past and present to put a base for some prognoses. Unfortunately old data are scarce or even missing and we can not balance more the past and last few/present from this perspective.

 

10-   - One of the major issues with the current presentation is the lack of specific population data for each species.  Almost all are shown as in decline, but this is not backed by survey numbers.

Some of the cited research are based on quantitative data and their conclusions related to the decline or not were used. The paper is under reviewers pressure that is already to long so adding such primary data is not an option here in this conditions, those quantitative more data will have the same conclusions as used here already. In some fish species cases old or new quantitative data, and the existent previous studies are based on qualitative approaches. There are some major gaps in this respect in the studied area.

 

11 – A way to improve the explication of long-term climate impacts would be to chose some cameo species from each of the major categories, and provide some short vignettes concerning the actual population trends – then separating climate from other factors – either synergistic or confounding – such as heavy fishing pressure. Providing a cameo on one of the critically endangered sturgeon species would interest many readers and would help to substantiate the overall conclusions of the paper. A possible strategy is to select a couple of the most endangered, a couple of the species in steep decline, and a couple that are resisting the stressors and provide somewhat more detailed documentation, then relate them to other species in similar circumstances.

We tried to have a broad coverage of all the present fish species. Going in deep with some species approach will unbalance the paper and will make it longer as far as some of the reviewers want it even now much more shorter. For sure your idea deserve specific new approach work to be done in the near future and we are very interested in this. After this paper rejection or admition the authors will be happy to work together with the reviewer in a new co-authorship/new paper to cover this approach angle too.

 

12 – The paper is basically a review rather than presentation of new data. To be a successful review it needs to rise above the conclusion the speedy environmental change will have generally negative impacts on most of the species, and give this more nuance.  Surely the impacts are not all from the same phenomena.  Also, due to reducing competition for some species, other established species or invasive species may take advantage of the shifts. The article points to very few winners or adaptable species.  The paper largely lacks any discussion of potential restructuring of fish communities, and what this will look like. Would it be possible to draw a clearer picture of what the surviving communities will look like?

Yes, this work was submitted as a review.

We added at the conclusions your suggestions trying to avoid to be too speculative in this situation in which the complexity of the issue approached is almost huge from a prospective point of view. Please see below.

In synthesis, trying to not be too speculative in this complex ecosystems changing situation, the speedy environmental change will have generally negative impacts on most of the species, but not on all of them. Surely the impact of the sea level rise will not be single but in synergy with other natural and anthropogenic stressors. Due to fish structure changes which will change the interspecific relations, including the next coming alien and invasive fish different species will take advantage on the new created situation. Only uptodate in situ adapted future monitoring programs will be able to register these firstly intimate changes, the base for future ichthyofaunal structure and relations establishment. For sure this in progress major changes will bring very interesting developments and discoveries in terms of the regional biological and ecological fish fauna characteristics.

 

Round 2

Reviewer 1 Report

The authors have incorporated some of the given suggestion, those that have not been are mostly acceptable. However, there is still an issue with numbers of years and "prehistoric periods". Please, make sure that part is in order and synchronized throughout the MS. Also, there is an issue about the writing of species names. Please, take some time to sort that out. One more thing, I think some references are not in order or are missing after parts of the MS text were deleted.

Some additional shortenings would be welcomed, but I understand that it is difficult to make reductions at this type of text.

All in all, there are still some corrections to be made, what does not reduce the contribution of the MS to the awareness of the influence climate change has at all levels.

Comments for author File: Comments.pdf

Author Response

The authors have incorporated some of the given suggestion, those that have not been are mostly acceptable.

THANK YOU FOR THE SUPPORT AND APRECIATION.

 

However, there is still an issue with numbers of years and "prehistoric periods". Please, make sure that part is in order and synchronized throughout the MS. 

DEAR REVIEWER THE YEARS AND PERIOD WERE TAKEN FROM THE APPROPRIATE REFERENCES. WE ARE AFRAID THAT WE ARE NOT SURE WHAT IS YOUR SUGESTION HERE.

 

 Also, there is an issue about the writing of species names. Please, take some time to sort that out. 

ALL THE SPECIES NAMES WERE CHECKED IN THE TEXT IN CONFORMITY WITH THEIR INTERNATIONAL ACCEPTED NAMES FOR THEM.

 

One more thing, I think some references are not in order or are missing after parts of the MS text were deleted.

THE REFERENCES WERE CHECKED AND MODIFIED WERE WAS NECESSAY.