Quantitative Morphometric Analysis of Morphologically Similar Species of Fragilaria (Fragilariaceae, Bacillariophyta) Allows Detection of Non-Indigenous Taxa: A Case Study from Lake Ladoga (North of European Russia)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors Invasive species are included in the Scope Water list. Since the article by Rusanov et al. showed morphological similarities between two geographically distant populations of the same species Fragilaria sublanceolata-baikali, and the authors concluded that this taxon can be considered invasive in Lake Ladoga, formally the article fits the Water journal. The title of the article shows the method, object of research, place of research and the main conclusion of the article  “Quantitative morphometric analysis of morphologically close species of Fragilaria (Fragilariaceae, Bacillariophyta) allows to detect non-indigenous taxa: a case study from Lake Ladoga (North of European Russia)”. Essentially, the authors showed that Fragilaria sublanceolata-baikali cells from populations from Lake Baikal and Lake Ladoga are morphologically similar and represent the same “morphological” species. That is, they expanded the distribution area of this species.   Unfortunately, unlike the previous article (Buczkó et al. Rapid expansion of an aquatic invasive species (AIS) in Central-European surface waters; a case study of Achnanthidium 661 delmontii. Ecol. Indic. 2022, 135, 108547, doi: 10.1016/j.ecolind.2022.108547) the authors do not consider any time scale, so the invasion does not have enough support.   The morphological approach itself using scanning microscopy is a basic method in the taxonomy of diatoms. In addition to size and shape, details of their structure are described, for Fragilaria these are: axial and central area shape, striae density, areola density, number and location of rimoportulae, apical pore fields, spines and some others. Based on SEM data, the authors describe them in the “Description” sections. The most difficult feature to describe is the curvature of the valve shape. For example, in the article by Zakharova et al. “Delimitation of Some Taxa of Ulnaria and Fragilaria (Bacillariophyceae) Based on Genetic, Morphological Data and Mating Compatibility”. Diversity 2023, 15, 271. https://doi.org/10.3390/d15020271 written “Valves are very narrow and long, narrow-lanceolate gradually narrowing toward rounded to weakly protracted or barely visible subcapitate ends”. The advantage of the authors of the reviewed article is their proposal to use quantitative geometric morphometric analysis to describe the shape of the valve. An important achievement is also that the authors showed how, in the studied species, the shape curvature of valves changes depending on the size of the valve. As a result of the research, the authors showed that the species F. sublanceolata-baikali, previously found only in Lake Baikal, lives in Ladoga, that is, this species is not endemic to Baikal. This is the second achievement of the authors.   But we must keep in mind that, taking into account current trends, morphological data alone to determine the similarity or difference of species to identify invasions, in my opinion, is not enough for an article in Water. I suggest that authors consider publishing in a more specialized journal, such as Diatom Research, where it will undoubtedly be of interest to diatomists. When preparing the article further, it is important to take into account that the names of the genus and species are highlighted in italics.

Author Response

Reviewer 1:

 

Unfortunately, unlike the previous article (Buczkó et al. Rapid expansion of an aquatic invasive species (AIS) in Central-European surface waters; a case study of Achnanthidium delmontii. Ecol. Indic. 2022, 135, 108547, doi: 10.1016/j.ecolind.2022.108547) the authors do not consider any time scale, so the invasion does not have enough support.

• We discussed the most probable way of the invasion of sublanceolata-baikaliand time of its appearance in Lake Ladoga (line 589-595):

 

There is also an example of successful invasion and active distribution in Lake Ladoga of the Baikal amphipod Gmelinoides fasciatus (Stebbing, 1899), which appeared in the lake in the late 1980s [60]. G. fasciatus invaded Lake Ladoga as a consequence of its intentional introduction, aimed at enhancing fish production, in some Karelian Isthmus lakes close to Lake Ladoga's western shore in the early 1970s [61]. Thus, we believe that the most probable time of appearance of F. sublanceolata-baikali in Lake Ladoga is the period from the early 1970s to the late 1980s.

 

But we must keep in mind that, taking into account current trends, morphological data alone to determine the similarity or difference of species to identify invasions, in my opinion, is not enough for an article in Water. 

• We hope that in the future we will be able to conduct a molecular study to confirm our conclusion based on morphometric similarity that the two populations of sublanceolata-baikali from Lake Ladoga and Lake Baikal are conspecific.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript describes a morphometric analysis of close species of Fragilaria from Lake Ladoga in Russia.  There had been few studies of Fragilaria especially those capable of identifying the three similar forms of the organism.

The manuscript carefully describes the methodology used to define and separate the three forms of the organism and ample figures show the specific characteristics used to identify them.  Likewise, the tables were informative and add to the resulting identifications.  The writing of the English text was clear and appropriate plus all spelling of the English was correct.  

The conclusion that the estimation of allometric shape variation may be a very useful tool for distinguishing among morphilogicaly close diatom species is likely to be a very important aspect of additional diatom research in the future.   

Author Response

Response to the reviewer 2

Manuscript ID: water-2670502

We would like to thank the reviewer for his/her comments for the manuscript.

There are no specific questions.

Reviewer 3 Report

Comments and Suggestions for Authors

 

This paper employed both traditional and geometric morphometrics to characterize morphology of three diatom species: F. sublanceolata-baikali, F. pectinalis and F. perminuta. This study highlighted the importance of size correction in accurately distinguishing these morphologically close species. The experiment was conducted meticulously, and data was interpreted thoughtfully.

Please find specific comments below.

1. L 155, I would suggest the authors to add the concentrations of sulfuric acid and potassium dichromate used for cold burning.

2. L 165, what is diameter of the Isopore polycarbonate membrane filter? Was the filter trimmed to fit the aluminum stubs?

3. L 210, Is it “generalized Procrustes superimposition procedure”?

4. L 471, a minor grammatical issue is present in this sentence.

5. L 598, there is a small grammatical error.

 

 

Author Response

Response to the reviewer 3

Manuscript ID: water-2670502

At first, we would like to thank the reviewer for his/her comments and useful suggestion for the manuscript. Below our point-by-point response to reviewer.

 

1. L 155, I would suggest the authors to add the concentrations of sulfuric acid and potassium dichromate used for cold burning.

• We added the following (line 158-162):

To clean diatom valves for the preparation of permanent slides, the field samples were treated by cold burning with sulphuric acid (H₂SO₄) and potassium dichromate (K₂Cr₂O₇) [38]. In the laboratory, 1 g of K₂Cr₂O₇ was added to 100 ml of warm concentrated H₂SO₄ and heated until dissolution of K₂Cr₂O₇. Then, 1 ml of this mixture was added to the diatom material for 10 min.

2. L 165, what is diameter of the Isopore polycarbonate membrane filter? Was the filter trimmed to fit the aluminum stubs?

• The diameter of the filter was 13 mm and it was not trimmed because it fitted well to stubs having diameter of 15 mm (line 172-173).

3. L 210, Is it “generalized Procrustes superimposition procedure”?

• Yes, it is (line 217).

4. L 471, a minor grammatical issue is present in this sentence.

• allowed (line 483).

 

5. L 598, there is a small grammatical error.

• to characterize (line 614).

 

Reviewer 4 Report

Comments and Suggestions for Authors

This paper reports an innovative and through body of research.

The main question addressed by research Is a diatom regarded as endemic to Lake Baikal also found in Lake Lagarda? The topic is completely original and uses novel techniques.
The paper is well-written and it is easy to read.

 

A few points need attention.

 

Lines 3-4. ‘allow detection of non-indiginous’.

 

Line 17. ‘a diatom, putatively Fragilaria’.

 

Line 21. ‘population (the putative F. sublancolata-baikali).

 

Line 64. Taxa of diatoms? Taxa of algae? Taxa of all organisms?

 

Line 148. What genus and species of reed?

 

Line 157. Explain ‘for dcantation’.

 

Line 198. ‘as a more effective’.

 

Line 434. ‘a’. not ‘the’.

Author Response

Response to the reviewer 4

Manuscript ID: water-2670502

At first, we would like to thank the reviewer for his/her comments and useful suggestion for the manuscript. Below our point-by-point response to reviewer.

 

Lines 3-4. ‘allow detection of non-indigenous’.

• We changed the title as suggested: “allows detection of…” (line 3-4).

 

Line 17. ‘a diatom, putatively Fragilaria’.

• We changed the text as suggested (line 19).

 

Line 21. ‘populations (the putative F. sublancolata-baikali).

• We changed the text as suggested (line 23).

 

Line 64. Taxa of diatoms? Taxa of algae? Taxa of all organisms?

• We have added “diatom taxa” (line 67).

 

Line 148. What genus and species of reed?      

• Phragmites australis (Cav.) Trin. ex Steud. (line 152).

 

Line 157. Explain ‘for decantation’.

• We added the following (line 162-163):

 

The cleaned diatom material was then washed three times in distilled water by centrifugation at 2000 rpm for 10 min and decantation of water layer.

 

Line 198. ‘as a more effective’.

• We changed the text as suggested (line 205).

 

Line 434. ‘a’. not ‘the’.

• We changed the text as suggested (line 443).

 

 

 

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Lines 633-637 "This 633 research was carried out as a part of the state assignment of Institute of Limnology RAS (No. 0154-634 2019-0001 for A.G.R.), the scientific project of Lomonosov Moscow State University (No. 635 121032300081-7 for M.A.G. and A.A.G.; No. 121032300124-1 for M.Y.K.) and the Széchenyi Plan Plus 636 program with the support of the RRF 2.3.1 21 2022 00008 project." This needs to be moved to Funding.

Author Response

We would like to thank the reviewer for his/her comment. Below our response to the reviewer.

Lines 633-637 "This 633 research was carried out as a part of the state assignment of Institute of Limnology RAS (No. 0154-634 2019-0001 for A.G.R.), the scientific project of Lomonosov Moscow State University (No. 635 121032300081-7 for M.A.G. and A.A.G.; No. 121032300124-1 for M.Y.K.) and the Széchenyi Plan Plus 636 program with the support of the RRF 2.3.1 21 2022 00008 project." This needs to be moved to Funding.

• This was moved to the Funding – line 631-634.

Author Response File: Author Response.pdf