The Role of Microalgae in the Biogeochemical Cycling of Methylmercury (MeHg) in Aquatic Environments

Round 1

Reviewer 1 Report

The manuscript the role of microalgae in the accumulation of methylmercury in aquatic environment. The topic is interesting, however the manuscript should be improved. Below are my detailed comments.

Please provide full name of abbreviation when first mentioned in text.

Section 2 – Please use a more specific title instead of just “discussion”. Or try to remove the title discussion and make all subsections become a main section.

Line 100-103 – Why mention only Baltic Sea? How about other places?

Line 209-210 – What is dry and wet deposition? Please provide examples.

Although the title mentioned microalgae, the section on microalgae is not that much. Please provide more discussion on response to methylmercury of different algae species. How the presence of mercury influences the composition of algal community? Try to make a table to summarize them.

The flow of the manuscript can be further improved

The summary of literature is not sufficient as there is only one table.

Please provide a section of challenges and future prospect.

Author Response

Thank you for very detailed and highly constructive comments that will greatly improve the quality and scientific relevance of the manuscript.

Author Response File: Author Response.docx

Reviewer 2 Report

I read with interest the manuscript entitled “The role of microalgae in the biogeochemical cycling of methylmercury (MeHg) in aquatic environments”. MeHg is the most toxic among the mercury species because of its volatility and its ability to pass through biological membranes. As a neurotoxic contaminant that bioaccumulates in aquatic food webs, and is thus found in seafood, most of the methylmercury found in aquatic food webs originated as anthropogenic emissions, and the path from emission sources to fish depends on many processes. Therefore, the identification, quantification, evaluation, and treatment of MeHg pollution in aquatic environments have aroused extensive interest. In this manuscript, the authors are focusing on the microalgae−MeHg interaction which is one of the entering points for MeHg into the aquatic environment. The uptake, distribution, toxicity, and complexation of MeHg in cultures of the green microalgae at a molecular level were well reviewed. The scope and the quality of the manuscript fit with the standards of the Phycology journal. Therefore, I would recommend it be published after a moderate revision.

1.       Figure 1a shows a very basic biogeochemical pathway of Hg in coastal areas with very limiting novelty. At least, the conditions (including DO, chemical or enzymatic catalysts, bacteria, etc.) which drive the change of Hg valency should be mentioned in the figure, e.g., DO level and redox potential mentioned in Section 2.2.

2.        As same as Figure 1a, Figure 1b is also too simple. The underlying metabolisms or interactions between microalgae and MeHg are not presented at a molecular level. e.g., the take-home message from Section 2.4 should be summarized and shown in the figure.

3.       Table 1 should be more informative. The authors barely reviewed the Hg and MeHg concentrations in different aquatic environments. However, how much of the MeHg can be accumulated or assimilated by algae, and further accumulated in different marine living organisms, should be of more interest. These numbers should be further reviewed and added to this table, or in a new table.

4.     Section 2.5 is the core of the manuscript. It is strongly recommended that the authors summarize the information into a table that introduces the response and mechanisms of different algae to the exposure/toxicity of MeHg, as well as the detoxification strategies.

 

5.     Most of the literature cited is out of the recent five years. A review paper should introduce the state-of-the-art of this area and cite the most advanced research instead of the obsoletes.

Author Response

Thank you for very detailed and highly constructive comments that will greatly improve the quality and scientific relevance of the manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All the comments have been addressed satisfactorily