Effect of 10 UV Filters on the Brine Shrimp Artemia salina and the Marine Microalga Tetraselmis sp.

Round 1

Reviewer 1 Report

This study evaluates the toxicity of selected UV filters on two marine organism (autotroph and heterotroph). Owing to the increased use of personal care products globally, there is a need to characterize their toxicity effects in aquatic systems including their stability, degradation and adsorption to sediments. Authors performed their experiments on 10 selected UV filters. Although the study has some relevance given the current context, however, it requires major revisions and is not acceptable in its current form. Some comments are provided in the manuscript PDF which needs to be addressed. Apart from them, there are some concerns as well regarding experimental design: 

1. What was the rationale behind selection of the concentration range? As authors referred in discussion that some of the concentration used in the study are many folds lower than found in natural environments. 
2. Why did authors decide to study acute toxicity and established lethal doses for not so realistic concentration ranges? As these UV filters are not added in high concentrations in PCPs, their release will bioaccumulate slowly so sub-chronic or chronic exposure might have been a better way to study toxicity. 
3. Out of 10 UV filters, 7 of them did not show any toxic/lethal effects for two model organisms. What does this signify? Can authors comment whether similar findings are reported in literature for these compounds.

Apart from these concerns, significant improvement is required for Introduction and Results section. Certain sections in Introduction have no logical flow and lack coherence, while, in Results and Discussion, it is more like a summary and listing of similar work rather than any discussion. 

Comments for author File: Comments.pdf

Author Response

Answers to your comments in the pdf file :

Introduction :

• line 35-36 : we added the main references with the range of concentrations for the most commonly found filters – see lines 36-40 of the revised version.
• Line 48-49 : yes, they are the most commonly used and studied filters for which toxicity has been reported in many papers – we added a sentence – see lines 58-60 in the revised version
• Line 50-52 + lines 57-69 : we have reorganized this part of the introduction to make it shorter and also much more logical.

 Methods :

• Lines 82-83 : now lines 80-84 – we have added some comments on the choice of the concentrations and we also explain that for phytoplankton, this study on Tetraselmis sp. is a preliminary study to investigate the dose-response to several filters to determine if it makes sense to study the response on a large diversity of species.

Results and discussion :

• Line 153 : you are right – we have clarified using only LC50 and EC10 or EC50. This is added in the M&M section (statistics) and also in the text at different places in the discussion.
• Lines 154-156 : We think that this is not a problem and clear in the paper : even if the tested concentrations are sometimes 500 times higher than those reported in the natural environment, (i) it is not the case for all filters because BP for instance can reach the highest tested concentrations, (ii) our interest was to determine the toxicity even at higher concentrations to see if the filters are toxic at these concentrations since most of them accumulate in the environment (low or not degradable) and their concentration may increase with time and ,(iii) it is interesting to see at what toxicity occur (when it occurs) to compare the response to the different filters.
• Line 165 : now line 275-277 – we have added a sentence to clarify`
• Lines 182-184 + line 192 : all this section has been improved according to your comments, with more discussion/interpretation.
• Lines 210, 217, 227 : same comment for different parameters – we have added a sentence saying that for a few filters and these parameters there is no toxicity but the next step will be to apply the same assay to a large diversity of phytoplaktonic species, including those who are symbionts of corals to determine their potential impact of phytoplankton and also their potential contribution to coral bleaching.

Answers to your comments on line :

• Point 1 : it concerns the concentration range – as indicated above and added in the text at different places we have argued about the concentrations. For Artemia we used a large range of concentrations because there are little data on the toxicity of UV filters and we used concentrations covering the entire range of concentrations reported in the filed considering that there are filters for which there are more or less no data on their occurrence. BP3 can be found at concentration up to 1.4 mg/L. For Tetraselmis, the range was limited to three concentrations in a preliminary study and the selected concentrations 10 to 1000 µg/L are in the range of the high concentrations reported in the field.
• Point 2 : As stated above we were investigating the dose-response effect and it was much more appropriate to study acute toxicity. The sub-chronic exposure may be also very interesting and this is something we will investigate in the future but both approaches have interest.
• Point 3 : We have added some comments on the discussion (lines 400-408) and conclusion sections. It is right that some filters have no toxic/lethal effects : it means that the toxicity differ between filters and species and if you look at Tetraselmis results it shows that the results between filters very depending on the parameter which is analyzed.

The attached file is the revised version with all changes in the checking mode

Reviewer 2 Report

The authors present a comprehensive study on the toxicity of 10 UV filters on Artemia salina and Tetraselmis sp. Although valuable, it needs to address several concerns before publication:

1. There are some issues with the use of the English language:

Title: It should say “…..the marine microalga Tetraselmis sp” not microalgae

Line 60: It should say Tetraselmis has

Line 111: It should say “ seven days of exposure” not exposition

Please, revise

2. In their conclusions the authors state values of NOECs and LOECs however, nothing is written in the manuscript on how the have calculated them. In addition, it is very tentative to calculate NOECs and LOECs for Tetraselmis when it seems that only three UV filter concentrations have been used (Figure 2).
3. Lines 187-189: The authors state that OC increases growth in the alga accompanied by a decrease in metabolic activity but on line 189 they say that they cannot find an explanation for the increased metabolic activity, which is a contradiction. I guess that authors meant that they couldn’t find an explanation for the increased growth rate, please re-write this well. In addition, the increase in growth rate might be due to hormesis, please discuss about this.
4. Please explain in more detail how the ChemChrom fluorochrome used to measure esterase activity works

Author Response

 

Point 1 :

• Title : it has been changed
• Line 60 : it has been changed accordingly
• Line 111 : right, we did the modification

 

Point 2 : This was also suggested by reviewer 1 and we did the modification and clarification in the text – it is clarified in the M&M section (statistics) and in the results and discussion.

 

Point 3 : You are right – this has been clarified in the text – see 319-329 in the revised version.

 

Point 4 : This has been added in the M&M section (FCM).

 

The attached file is the revised version in the checking mode to see all changes

Round 2

Reviewer 1 Report

Authors have done a number of changes in the manuscript to improve the overall quality. Final thorough read is warranted to close any minor gaps. 

Author Response

The manuscript has been checked by a native english speaking colleague.

All changes appear in the revised version using the word tracking system and you can see all modifications.

Also the introduction was improved as suggested by the editor by adding aims at the end