Characteristics of Two Lagoons in the Coastal Area of the Baltic Sea
, Laura Grinberga 2, Linda Dobkevica 1, Agnija Skuja 2, Davis Ozolins 2, Ivars Druvietis 3, Viesturs Ozols 1 and Jana Paidere 4Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsReview for the paper "Characteristics of two lagoons in the coastal area of the Baltic Sea" by Oskars Purmalis, Laura Grinberga, Linda Dobkevica, Agnija Skuja, Davis Ozolins, Ivars Druvietis, Viesturs Ozols, Jana Paidere submitted to "Limnological Review".
General comment.
Coastal lagoons represent about 13% of the world's coastline and these marine or estuarine ecosystems are of high interest in terms of biodiversity and socio-economic activities, as they provide important food resources and are considered one of the most productive ecosystems in the world and one of the oldest areas of aquaculture. The biodiversity of coastal ecosystems depends on variations in environmental parameters, which can be frequent and of great magnitude. Changes in nutrients, freshwater discharge and wastewater can alter the community structure of pelagic organisms. Plankton is a key component in aquatic systems, serving as a production base for higher trophic levels. The study deals with coastal lagoons in Latvia (Baltic Sea region) and aims to describe the environmental conditions and biota during 2020-2021. The region is less studied and the present research is a baseline comprehensive report interesting for future monitoring of the coastal zone in the Baltic Sea. There are some issues to be addressed before the paper is accepted.
Specific comments.
Abstract. It is important to include the main results in the abstract. Currently, there is no text that refers to the results. Expand on the key findings in this section to provide a clearer overview of the study.
Keywords. It is suggested to add 'benthos' or 'benthic fauna' in the Keywords.
L90. Consider replacing " period 2020–2021 " with " period of 2020–2021 ".
Section 2.1. Please provide a brief overview of the climatic conditions in the region and also the hydrological conditions in the lagoons. In particular, data on water temperature should be included in the paper.
Table 1. Replace 'x' and 'y' with 'N' and 'E' in the Coordinates line.
Section 2.4. The authors employed the Simpson index to assess zooplankton diversity. However, it is recommended to calculate and present data using the Shannon-Wiener index and Pielou evenness, which are more commonly used and preferred measures. Relevant information should be included in the Results section.
Section 2.5. Describe a procedure for determining the biomass of phytoplankton and the appropriate units for measuring it (wet or dry).
Results. It is recommended to present the average values for the environmental and biotic variables that were analyzed. Additionally, compare different sites based on these parameters using appropriate statistical methods such as ANOVA or Kruskal-Wallis Test.
L422. Acanthocyclops must be in Italics.
L438. Provide the range from the smallest to the largest value (i.e. 0.10 to 0.19).
L451. The free-living marine ciliate Mesodinium rubrum is not classified as a type of phytoplankton. Please make the necessary correction in the text below or replace Section 3.6 with the heading 'Microplankton Community Structure'.
L552. Consider replacing "Sea" with "the sea".
L554. Consider replacing "Baltic Sea" with "the Baltic Sea ".
Discussion. More details must be included in the discussion regarding the composition and diversity of the benthos and phytoplankton. To further support the argument, comparisons of the biomass and composition with past reports should be provided.
Comments on the Quality of English LanguageSome revisions are required.
Author Response
Comment: Abstract. It is important to include the main results in the abstract. Currently, there is no text that refers to the results. Expand on the key findings in this section to provide a clearer overview of the study.
Response: Thanks for suggestion, abstract were improved by adding results and main key findings: “The physico-chemical composition of lagoon sediments and water shows the impact of sea water by increased electrical conductivity, concentration of SO42- and Cl- in water, while presence of detritus in sediments is almost non-existent, thus also content of organic matter is low with relatively variable pH. The results show that the diversity of studied benthic macroinvertebrates, macrophytes, zooplankton and even phytoplankton species is low, but with higher diversity in lagoons and their parts with regular water exchange with the sea.
Comment: Keywords. It is suggested to add 'benthos' or 'benthic fauna' in the Keywords.
Response: Agree with comment and to keywords were added “benthic fauna”.
Comment: L90. Consider replacing " period 2020–2021 " with " period of 2020–2021 ".
Response: Agree with the comment and we were made suggested changes.
Comment: Section 2.1. Please provide a brief overview of the climatic conditions in the region and also the hydrological conditions in the lagoons. In particular, data on water temperature should be included in the paper.
Response: In materials and methods was added overview of the climatic conditions in the region of studied lagoons. Hydrological conditions were not quantified in this study, but in section 2.1 were described lagoons and hydrological conditions from surveys during study period. Water temperature data were added to Table S1.
Comment: Table 1. Replace 'x' and 'y' with 'N' and 'E' in the Coordinates line.
Response: Since some aspects about sampling places were also in comments from other reviewers, we decided to change the table to figure with representation of sampling points.
Comment: Section 2.4. The authors employed the Simpson index to assess zooplankton diversity. However, it is recommended to calculate and present data using the Shannon-Wiener index and Pielou evenness, which are more commonly used and preferred measures. Relevant information should be included in the Results section.
Response: The Simpson's reciprocal index (or Hill's reciprocal numbers N2) also quantifies species diversity by considering richness and evenness. The index was used as it is the preferred form of species diversity measures because they are in units of species numbers, and varies from 1 to s, the number of species in the sample. In this form index can be most easily interpreted as the number of equally common species required to generate the observed heterogeneity of the sample.
Comment: Section 2.5. Describe a procedure for determining the biomass of phytoplankton and the appropriate units for measuring it (wet or dry).
Response: Description of procedure was improved and added units for wet biomass.
Comment: Results. It is recommended to present the average values for the environmental and biotic variables that were analyzed. Additionally, compare different sites based on these parameters using appropriate statistical methods such as ANOVA or Kruskal-Wallis Test.
Response: Thank you for the suggestion. We would use ANOVA or Kruskal-Wallis Test, however there are too few replicates in each lagoon, e.g., 1 zooplankton and macroinvertebrate sample per lagoon. Please, see chapters 2.4, 2.5., 2.6., where number of replicates are described. Similarly to biologic constituents also characterized environmental conditions: sediments and water chemistry doesn’t reach the number of replicates to be able to use ANOVA or Kruskal-Wallis Test. Moreover surveyed lagoons have noticeable individual differences limiting usefulness of certain statistical analysis.
Comment: L422. Acanthocyclops must be in Italics.
Response: Agree with the comment and we were made suggested changes.
Comment: L438. Provide the range from the smallest to the largest value (i.e. 0.10 to 0.19).
Response: Agree with the comment and we were made suggested changes.
Comment: L451. The free-living marine ciliate Mesodinium rubrum is not classified as a type of phytoplankton. Please make the necessary correction in the text below or replace Section 3.6 with the heading 'Microplankton Community Structure'.
Response: More detailed description of the free-living mixotrophic marine ciliate Mesodinium rubrum was added in the discussion with explanation that it was found additionally to the phytoplankton.
Comment: L552. Consider replacing "Sea" with "the sea".
Response: Agree with the comment and we were made suggested changes.
Comment: L554. Consider replacing "Baltic Sea" with "the Baltic Sea ".
Response: Agree with the comment and we were made suggested changes.
Comment: Discussion. More details must be included in the discussion regarding the composition and diversity of the benthos and phytoplankton. To further support the argument, comparisons of the biomass and composition with past reports should be provided.
Response: The discussion of phytoplankton and benthos was supplemented with a comparison of results of other studies.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper aims to characterize two lagoons in the coastal area of Latvia and is agreeable to read, but I think that some key issues are missing. I will comment on some specificities.
It is not clear in the manuscript if these lagoons have been studied before or not. The right characterization of the ecosystems lacks also characterization in terms of climatic variables such as temperature, precipitation, knowledge of productive season and known anthropogenic sources. None of this exists so my question remains. Have these systems been studied previously? If not, mention that in the text, if so write it down.
There are issues in the way this manuscript is done since is based on just a few surveys, If no others have been made for these lagoons I would advise you to consider this as a reference condition study and don«t do much speculation about the results, but if there are some previous studies than this manuscript needs to be rewritten in various parts.
Introduction
lines 36-41: "Such conditions...." Two paragraphs almost say the same thing and some words are repeated. Could you summarize it in just one paragraph without repetitions?
lines 47-49 "High.... biodiversity". It´s again a repetition of what has been said in lines 36-41. Eliminate this or work it out with the previously mentioned lines.
lines 56-58: "Because---existence". Again it´s a repetition.
I suggest that you organize this part of the introduction until this point in two sections, the one where you explain/refer to the generalities about lagoons and the section where you refer to lagoons in the Baltic area. The present form seems a little like a patchwork.
Methods
This entire section needs to be improved. It is not clear how many surveys and when. for several parameters. To my understanding, most of them were made in summer except for water.
1. It lacks a map with the localization of the stations in each lagoon, where we can see also their shapes which I find essential. You can accommodate all in Fig 1. Provide it. With a correct map, table 1 is unnecessary.
2.1. Characterization of lagoons
this entire section is written without a single reference. How do you know these characteristics? Include the respective references,
2.2 Characterization of water and sediments
The readers do not have to guess or go to supplementary material to understand how many surveys have been done. Please specify in the text the number of surveys made for water samples and sediments.
The methods are vague and lack the proper description of the methods and the techniques used not to mention the method's precision. You need to provide this for both sediments and water samples
Also, for the water, specify the "main ions", Another question is why the supplementary variables are not mentioned in the text.
2.5. Characterization of phytoplankton
It lacks the number of surveys and the units for the abundance of phytoplankton being presented, which equipment you use, etc... The phytoplankton description is very poor compared to zooplankton. Do try to balance both.
if you are using orthophoto mapping in results do describe the lagoons changes. it is missing a proper section in methods, how did you get this?
Result
3.1 Sediment analysis
lines 233-243: Unless this was made during this study, which is not clear, this entire section should be in the section where you characterize the lagoons and also it lacks references.
How many times have you collected sediments and when? Just one? it seems so, by the legend of table 2. If so how can you speak about sedimentation rates? unless you have previous studies but that is not clear in the manuscript.
3.2. Water analysis
salinity is in SI units whether represented in psu or with no units, so your results are not concerning salinity but electrical conductivity. Decide what are you presenting and write lines 302-305 accordingly.
Fig 5, 5, 7, and 8 make a clear separation between lagoons. It can be easily achieved with a line as tall as y axis between Mersrags section and Randu plavas.
line 331-333: "a concentration....34". remove this sentence. I do not agree with this. Intensive growth of algae and others is also dependent on N/P ratio and N/Si and P/Si and other things, P alone will not cause blooms like it is mentioned.
line 333-334: you speak about good quality, but for this, you have to have thresholds already established. Unless you provide this, rewrite the paragraph.
line 353-355: This section is a repetition. You´ve already said that there was a contribution of the water from the sea. Don´t use the expression hypersaline, because except for the Baltic Sea which behaves mostly as an estuary concerning salinity, hypersaline water in general is above 36 in most parts of the world. You are located in one part of the Baltic Sea that has salinities below 20, which is not salt water.
Discussion
There are a lot of parts that are already said in the results. Also, some claims about the lagoons are made not in the base of this study, again, if there are any previous studies those should be mentioned. This is particularly denoted in the section on sediment and water properties. So, rewrite this.
Overall, macrophytes, macroinvertebrates, zooplankton and phytoplankton sections in results and discussion do not need much work.
Conclusion
You've started this section with generalities about lagoons, then in the middle, you do it again and the all section is very vague. This is not what a conclusion section should look like. Rewrite it fitting it to your results at the beginning and then explain the measures and what it highlights. You have only one year of results and unless you have previous data, you can not make many assumptions. Simplify it,
References
They seem adequate, but some have the date in bold and others don't. Please uniformize it according to the journal's requirements.
Author Response
Comment: It is not clear in the manuscript if these lagoons have been studied before or not. The right characterization of the ecosystems lacks also characterization in terms of climatic variables such as temperature, precipitation, knowledge of productive season and known anthropogenic sources. None of this exists so my question remains. Have these systems been studied previously? If not, mention that in the text, if so write it down.
Response: In Abstract were made addition to highlight that such study were done for first time: “for the first time characterize their current conditions and ecological parameters
In materials and methods were added overview of the climatic conditions in the region of studied lagoons, length of productive season and known anthropogenic sources
Comment: ”There are issues in the way this manuscript is done since is based on just a few surveys, If no others have been made for these lagoons I would advise you to consider this as a reference condition study and don«t do much speculation about the results, but if there are some previous studies than this manuscript needs to be rewritten in various parts.
Introduction
lines 36-41: "Such conditions...." Two paragraphs almost say the same thing and some words are repeated. Could you summarize it in just one paragraph without repetitions?
lines 47-49 "High.... biodiversity". It´s again a repetition of what has been said in lines 36-41. Eliminate this or work it out with the previously mentioned lines.
lines 56-58: "Because---existence". Again it´s a repetition.
I suggest that you organize this part of the introduction until this point in two sections, the one where you explain/refer to the generalities about lagoons and the section where you refer to lagoons in the Baltic area. The present form seems a little like a patchwork.
Response: Following the suggestions, corrections for introduction have been made.
Comment: Methods. This entire section needs to be improved. It is not clear how many surveys and when. for several parameters. To my understanding, most of them were made in summer except for water.
Response: Section materials and methods were improved.
Comment: 1. It lacks a map with the localization of the stations in each lagoon, where we can see also their shapes which I find essential. You can accommodate all in Fig 1. Provide it. With a correct map, table 1 is unnecessary.
Response: Instead of a table we prepared a map with sampling point locations and added information on the methodology section about sampling methods.
Comment: 2.1. Characterization of lagoons. this entire section is written without a single reference. How do you know these characteristics? Include the respective references.
Response: In the study period of lagoons without samplings were made field surveys for characterization of lagoons and to better understand dynamics of these ecosystems including impact of water level fluctuations and dominant flows. Acquired knowledge about abiotic factors is of high importance therefore were precisely described in section 2.1.
Comment: 2.2 Characterization of water and sediments. The readers do not have to guess or go to supplementary material to understand how many surveys have been done. Please specify in the text the number of surveys made for water samples and sediments.
Response: Sample collection times have been specified.
Comment: The methods are vague and lack the proper description of the methods and the techniques used not to mention the method's precision. You need to provide this for both sediments and water samples
Response: The description of water chemical analysis methods has been updated.
Comment: Also, for the water, specify the "main ions"
Response: Suggestion taken into account and ions named.
Comment: Another question is why the supplementary variables are not mentioned in the text.
Response: The description of water chemical analysis methods has been updated.
Comment: 2.5. Characterization of phytoplankton. It lacks the number of surveys and the units for the abundance of phytoplankton being presented, which equipment you use, etc... The phytoplankton description is very poor compared to zooplankton. Do try to balance both.
Response: Were improved description of methodology: “Species composition, density, and cell dimensions were determined under a Leica DMIL microscope (200 and 400 fold magnification). 5 ml and 10 ml KC Denmark sedimentation counting chamber was used. Cell counts were converted to biovolumes (fresh weight mg/l), calculated using measured cell dimensions applied to simple geometrical shapes. ”
Comment: if you are using orthophoto mapping in results do describe the lagoons changes. it is missing a proper section in methods, how did you get this?
Response: Was improved description of methodology.
Comment: Result.3.1 Sediment analysis
lines 233-243: Unless this was made during this study, which is not clear, this entire section should be in the section where you characterize the lagoons and also it lacks references.
Response: In lagoons detailed field works were done and the majority of lagoon territory can be surveyed also by walking, because of low water depth. We have removed sentences which do not represent sediment analysis and actual measurements.
Comment: How many times have you collected sediments and when? Just one? it seems so, by the legend of table 2. If so how can you speak about sedimentation rates? unless you have previous studies but that is not clear in the manuscript.
Response: Described results were revised with focus on sediments and their composition. Sediment sampling were done once in study period.
Comment: 3.2. Water analysis. salinity is in SI units whether represented in psu or with no units, so your results are not concerning salinity but electrical conductivity. Decide what are you presenting and write lines 302-305 accordingly.
Response: The description has been clarified.
Comment: Fig 5, 5, 7, and 8 make a clear separation between lagoons. It can be easily achieved with a line as tall as y axis between Mersrags section and Randu plavas.
Response: The separation between the lagoons is placed in the images.
Comment: line 331-333: "a concentration....34". remove this sentence. I do not agree with this. Intensive growth of algae and others is also dependent on N/P ratio and N/Si and P/Si and other things, P alone will not cause blooms like it is mentioned.
Response: Unsuccessfully formulated sentence were changed as well as results of N/P ratios are added.
Comment: line 333-334: you speak about good quality, but for this, you have to have thresholds already established. Unless you provide this, rewrite the paragraph.
Response: Thanks for pointing out this aspect. In result text was revised.
Comment: line 353-355: This section is a repetition. You´ve already said that there was a contribution of the water from the sea. Don´t use the expression hypersaline, because except for the Baltic Sea which behaves mostly as an estuary concerning salinity, hypersaline water in general is above 36 in most parts of the world. You are located in one part of the Baltic Sea that has salinities below 20, which is not salt water.
Response: Text was revised to avoid repetition.
Comment: Discussion. There are a lot of parts that are already said in the results. Also, some claims about the lagoons are made not in the base of this study, again, if there are any previous studies those should be mentioned. This is particularly denoted in the section on sediment and water properties. So, rewrite this.
Overall, macrophytes, macroinvertebrates, zooplankton and phytoplankton sections in results and discussion do not need much work.
Response: Agree to comments and discussion part were revised and necessary additions were made.
Comment: Conclusion. You've started this section with generalities about lagoons, then in the middle, you do it again and the all section is very vague. This is not what a conclusion section should look like. Rewrite it fitting it to your results at the beginning and then explain the measures and what it highlights. You have only one year of results and unless you have previous data, you can not make many assumptions. Simplify it,
Response: Structure of conclusions were improved.
Comment: References. They seem adequate, but some have the date in bold and others don't. Please uniformize it according to the journal's requirements.
Response: Reference list were prepared according to journal guidelines.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript covers an interesting topic, but still requires many corrections.
Detail comments
There are many sentences in Results that should only be included in Discussion. For example, this concerns the algal and macrophyte origin of sediments, eutrophication with reference citation (line 333). Feel free to separate these fragments and move them to Discussion or combine Resuls and Discussion.
The record of whether benthic invertebrates or benthic macroinvertebrates were analyzed should be standardized.
Line 397 – remove the letter e - ... ewas found
Use lower case letters in terms such as cryptophytes, chlorophytes, euglenophytes, desmids (compare lines 448 and 458).
On what basis were ciliates included in phytoplankton???? See line 451-452, 461-462. This raises my serious reservations about the correctness of the phytoplankton determinations and the researcher's awareness.
Uthermol's method only concerns abundance and does not explain how to calculate phytoplankton biomass. You need to complete the information.
Table 1 - … water color not color
Author Response
Comment: There are many sentences in Results that should only be included in Discussion. For example, this concerns the algal and macrophyte origin of sediments, eutrophication with reference citation (line 333). Feel free to separate these fragments and move them to Discussion or combine Resuls and Discussion.
Response: Thanks for suggestions, those sections were revised.
Comment: The record of whether benthic invertebrates or benthic macroinvertebrates were analyzed should be standardized
Response: Thank you for pointing this out! We standardized it to “benthic macroinvertebrate”
Comment: Line 397 – remove the letter e - ... ewas found.
Response: Agree with comment and we were made suggested changes.
Comment: Use lower case letters in terms such as cryptophytes, chlorophytes, euglenophytes, desmids (compare lines 448 and 458).
Response: Agree with the comment and upper case letters were changed to lower case letters.
Comment: On what basis were ciliates included in phytoplankton???? See line 451-452, 461-462. This raises my serious reservations about the correctness of the phytoplankton determinations and the researcher's awareness.
Response: More detailed description of ciliates was added in the discussion with explanation that they were found additionally to the phytoplankton in samples.
Comment: Uthermol's method only concerns abundance and does not explain how to calculate phytoplankton biomass. You need to complete the information.
Response: Agree with the comment. Information to the materials and Methods was added: “Species composition, density, and cell dimensions were determined under a Leica DMIL microscope (200 and 400 fold magnification). 5ml and 10ml KC Denmark sedimentation counting chamber was used. Cell counts were converted to biovolumes (fresh weight mg/l), calculated using measured cell dimensions applied to simple geometrical shapes”.
Comment: Table 1 - … water color not color
Response: Agree with the comment and we made suggested changes.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI've read the manuscript and I was satisfied with the changes made by the authors.
Author Response
Thanks for review and made suggestions for improvements.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript clearly improved after the corrections.
However, the discussion should explain why some species of ciliates can carry out the process of photosynthesis and may play an important role in the primary production of marine ecosystems. If there are citations about ciliates in the discussion, you should also leave your results about ciliates, separating this group from typical phytoplankton (a separate paragraph).
Author Response
Thanks for previous review and suggestions! We added 3.7. chapter with results of microplankton. It is worth to mention that microplankton analysis weren’t our aim of study, but since they were present and abundant, decided to mention in manuscript. Were improved also discussion part about ciliates but removed sentence about primary production. It wasn’t formulated very successfully and therefore can be confusing for readers.
Author Response File: 
Author Response.pdf
