Not a Good Place to Live for Most, but Excellent for a Few—Diversity of Zooplankton in a Shallow Coastal Ecosystem

Round 1

Reviewer 1 Report

The manuscript reflects the results of zooplankton research in the Vistula Lagoon in recent years. The study continues the observations of zooplankton that have been carried out for almost half a century. Such long-term investigations are valuable, as they allow us to observe changes in the community over time under changing climatic conditions and anthropogenic impact. The authors show the decline in zooplankton diversity under the influence of several stressful factors. Only a few species gained the advantage of development and formed a significant zooplankton biomass. Thus, brackish waters can serve as a springboard for the penetration of new species, both in freshwater and marine systems.

The authors show that the Shannon index decreases over the years and believe that the decrease in zooplankton diversity is due to the action of factors such as salinity and turbidity. However, such a statement seems speculative, since the authors provide data on these factors during the period of this study, but do not provide data for past periods. It is necessary to provide data on the physico-chemical parameters of the environment in earlier periods in order for the authors' assumption about the relationship between zooplankton diversity and environmental factors to be more evidence-based.

Author Response

Comment: The authors show that the Shannon index decreases over the years and believe that the decrease in zooplankton diversity is due to the action of factors such as salinity and turbidity. However, such a statement seems speculative, since the authors provide data on these factors during the period of this study, but do not provide data for past periods. It is necessary to provide data on the physico-chemical parameters of the environment in earlier periods in order for the authors' assumption about the relationship between zooplankton diversity and environmental factors to be more evidence-based.

Response: We agree with that. We do not analyze the effect of physico-chemical parameters in this manuscript, we present only basic physico-chemical parameters in Methods (lines 100-102) as a background. To avoid speculation we modified the aims of the study (lines 68-70) and some other parts of the manuscript (lines: 16-19, 226-230, 321-324).

Reviewer 2 Report

This study is examined diversity of zooplankton in a coastal ecosystem. The ms is well discussed seasonal occurrence of the zooplankton species. But I have some comments to revise it before publishing as follows.

 

1, Authors simply stated the study periods, spring, summer and autumn for 3 years. However, it may be better describe months instead of seasons. And, explain how are months in each season among years similar or different in terms of environmental conditions, temperature etc? If environmental factors are highly different in the season among years, you could not categorize as a season. If not, then you can summarize the description.

 

2, In Fig. 2 and 3, you summarized as 3 seasons. But it would be better to show each month for 3 years. 

Author Response

Comment: 1, Authors simply stated the study periods, spring, summer and autumn for 3 years. However, it may be better describe months instead of seasons. And, explain how are months in each season among years similar or different in terms of environmental conditions, temperature etc? If environmental factors are highly different in the season among years, you could not categorize as a season. If not, then you can summarize the description.

2, In Fig. 2 and 3, you summarized as 3 seasons. But it would be better to show each month for 3 years.

Response: The sampling was made in the middle of spring, summer, and autumn each year - we improved the description in Methods (line 94).

In the year preceding the research (2017-18), we conducted research every month, but due to the low variability, we limited the sampling to one time in each season.

There were no significant differences between plankton communities and environmental parameters between the same season in different years. Furthermore, there was a low variability of environmental parameters between seasons. We pointed out in Methods ‘In 2019-2021 the average water temperature in the study area was 13.9 ± 4.3°C, salinity 3.6 ± 0.8 PSU, oxygenation 96.4 ± 15.9 %, Secchi depth 0.47 ± 0.24 m, and turbidity 38.2 ± 22 FNU (Kornijów, unpublished data)’ (lines 99-101 ).

Reviewer 3 Report

General comments

The problem addressed in this study is interesting and important for aquatic sciences. It is known that transitional waters of the brackish type are affected by various types of pressure, pollution, eutrophication, mixing with fresh waters, and sediments.

However, the manuscript has some deficiencies.

The study design is insufficient. There is no correlation between the stated purpose of the study and the way the results and discussions are presented. The conclusion is risky because no data series were presented for temperature, salinity, and turbidity. Also, there is no multivariate statistical processing to support the conclusions of the study. These are discussed further from the literature or unpublished data.

The hypothesis stated in the introduction has no coverage in the conclusions because there were no comparative studies, before and after earthworks opening the canal through Vistula Spit

In conclusion, the manuscript can be published in Sustainability, after a major revision.

 

 

Specific comments

The introduction must be improved with the current state of knowledge of the problem treated in the study

 

For other specific comments, please see the revised manuscript.

Comments for author File: Comments.pdf

Author Response

Comment: The study design is insufficient. There is no correlation between the stated purpose of the study and the way the results and discussions are presented. The conclusion is risky because no data series were presented for temperature, salinity, and turbidity. Also, there is no multivariate statistical processing to support the conclusions of the study. These are discussed further from the literature or unpublished data.

Response: We agree with that. We do not analyze the effect of physico-chemical parameters in this manuscript, we present only basic physico-chemical parameters in Methods (lines 100-102) as a background. To avoid speculation we modified the aims of the study (lines 68-70) and some other parts of the manuscript (lines: 16-19, 226-230, 321-324).

Comment: The hypothesis stated in the introduction has no coverage in the conclusions because there were no comparative studies, before and after earthworks opening the canal through Vistula Spit

Response: Our research covered the period of hydro-technical works in Vistula Lagoon related to digging a canal through the Vistula Spit. This could be one of the factors responsible for the declining diversity of zooplankton and we discussed our results on the background of the long-term changes of zooplankton. We also believed that the results of our research could be relevant for the analysis of future changes in plankton communities after increasing the exchange of waters with the Baltic Sea.

Round 2

Reviewer 2 Report

The revised manuscript is satisfied.

Reviewer 3 Report

I believe that the manuscript has mostly been improved and can be published in this form.