Possible Origin and Distribution of an Invasive Diatom Species, Skeletonema potamos, in Yangtze River Basin (China)

Round 1

Reviewer 1 Report

The present ms report the morphology, genetic sequences and distribution of Skeletonema potamos from the Changjiang River Basin during 2016–2022. They found genetic similarity between Chinese strains and those from USA and Japan and suspect that it is an invasive species through currents or cargo ship. The conclusion however is not supported by the results.

 

Major concern:

(1) Previous record of S. potamos in China

Skeletonema potamos has been reported in Yangtze River by Zhang et al. 2022.

Zhang, L., Yang, J., Zhang, Y., Shi, J., Yu, H., & Zhang, X. (2022). eDNA biomonitoring revealed the ecological effects of water diversion projects between Yangtze River and Tai Lake. Water Research, 210, 117994.

(2) Possible Origin of S. potamos in China

Skeletonema potamos is a freshwater species, how can they transport through ocean currents? Do you have evidences that this species can survive high salinity?

Table 4 cited Seoane, et al. 2005, but this reference stressed ‘freshwater representative Skeletonema potamos’.

I do not have access to Bazzon et al 2012, but the authors need double check.

 

Specific comments:

Line 18, please delete ‘are’;

Line 29, diatom genus;

line 33, please introduce the second freshwater species;

Line 40, as a synonym of what?

Table 2, the Chinese strains were not in bold;

 

 

English needs polish.

Author Response

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Reviewer 2 Report

The article devoted to the study of morphology and distribution of the invasive diatom species, Skeletonema potamos, from the Yangtze River Basin. The manuscript is well elaborated and contains interesting data.

Please, find some my comments in the attached file. I think that the title should be modified to be more relevant to the article content. In fact the authors studied not origin but invasion of S. potamos in China. Honestly, I don't like the term "exotic species". I prefer terms "alien", ''adventive", "invasive" etc (see also: Richardson et al. 2000, doi: 10.1046/j.1472-4642.2000.00083.x) The quality of Fig. 3 is too low. Also I think that authors should add the phylogenetic tree to show the placement of their strain.

Unfortunately, I couldn't open supplementary files. 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript is devoted to clarifying the identification and geographical distribution of the diatom Skeletonema potamos in some water bodies of China. The authors of the manuscript consider the possible origin and distribution of this alga in the Yangtze River basin, as well as the mechanisms that contribute to the development and dominance of S.potamos. The results obtained greatly expand our understanding of the biology and ecology of Skeletonema potamos and can serve as a basis for future physiological and ecological studies. The analysis presented in this manuscript is based on many years of observations and a large amount of factual material, which is the advantage of the manuscript.

Some points require clarification.

1.     Section 2 (Materials and methods) lacks information about the Study area. How many water bodies were observed in total, what type of water bodies are these? It is necessary to give the main morphometric, hydrophysical and hydrochemical characteristics of these reservoirs. Below in the text of the manuscript (section 3.4 Ecology Analysis), a correlation analysis is given with important environmental factors that significantly affect the occurrence and abundance of S. potamos. How were these basic environmental parameters measured? If these data have already been published earlier, then it is necessary to make a link to these publications.

 2.     In Section 2.1. (SampleExamination) the authors indicate that in each sample with Skeletonema potamos they counted 400 algal units. At the same time, the authors do not specify what was taken as a counting unit (which corresponded to 1 unit) - were they individual cells or were the colonies of this diatom counted. This needs to be specified.

 3.     In Section 4.1 (Morphological Comparison), the authors point out that Skeletonema potamos found in samples from Chinese water bodies had a smaller frustules diameter (Lines 220-221). How can the authors explain such small sizes? It would be a good idea to do a correlation analysis with environmental factors to determine the parameters that favor the development of small celled forms of this species.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors did not provide a point to point response and my concern has not been addressed.