Aquatic Microplastic Research—A Critique and Suggestions for the Future
Round 1
Reviewer 1 Report
Microplastics have become an emerging pollutant, which attracts increasing attention, especially in the marine environment due to its small size, difficult removal and wide distribution. This paper summarizes the current research results and puts forward suggestions for the future. This review is of great value for future research.
1. This review focuses on the research Suggestions of microplastics on aquatic animals, and water ecology contains aquatic plants and microorganisms, please supplement the toxic effect of microplastics on aquatic plants.
2. In natural water, the surface of microplastics is easily covered by biofilms, which is a good habitat for insects to lay eggs and bacteria and algae to colonize. Microplastics can be used as the carrier of microorganisms.
3.Some studies have shown that microplastics adhere to the surface of aquatic animals and aquatic plants, causing negative effects. Please add relevant content.
Author Response
Comment
- This review focuses on the research Suggestions of microplastics on aquatic animals, and water ecology contains aquatic plants and microorganisms, please supplement the toxic effect of microplastics on aquatic plants. Reply - a section on effects of mps on aquatic plants has been added - on page 4
2. In natural water, the surface of microplastics is easily covered by biofilms, which is a good habitat for insects to lay eggs and bacteria and algae to colonize. Microplastics can be used as the carrier of microorganisms. Reply a consideration of microfilms is added on page 2
3.Some studies have shown that microplastics adhere to the surface of aquatic animals and aquatic plants, causing negative effects. Please add relevant content. Reply - this is mentioned on page 2
Reviewer 2 Report
I think that this review is a valid perspective on the research that is being done on microsplastics (mps).
1.Introduction
I suggest that the author such add to the introduction that mps can be carriers of toxins that would be delivered inside the organisms that causes the toxicity and not the microplatics itself. In that way makes sense that you approach that topic in 7. chemical toxicity.
2 Collecting and counting. In the last paragraph I think that would benefit this review to mention also the mps in sediments because a large portion of the organisms are bottom dwellers and ingest mps from the sediment. It makes a lot of sense because in the next chapter (3), you mention the organism that feed on sediments and did not talk about them in the previous chapter(2).
6. Effects
I think that the author must add references at the end of the sentence that starts with "Papers....[].
Again in ln 143. "Some studies....[]. I think that will exemplify better what you are trying to evidence.
7. Chemcal toxicity
Ln 219 (50) and mus be [50].
Author Response
I suggest that the author such add to the introduction that mps can be carriers of toxins that would be delivered inside the organisms that causes the toxicity and not the microplatics itself. In that way makes sense that you approach that topic in 7. chemical toxicity.
Response This has been added on page 1
2 Collecting and counting. In the last paragraph I think that would benefit this review to mention also the mps in sediments because a large portion of the organisms are bottom dwellers and ingest mps from the sediment. It makes a lot of sense because in the next chapter (3), you mention the organism that feed on sediments and did not talk about them in the previous chapter(2). Response Sediments as a sink for mps have been added on page 2
6. Effects
I think that the author must add references at the end of the sentence that starts with "Papers....[].
Again in ln 143. "Some studies....[]. I think that will exemplify better what you are trying to evidence. Response I am reluctant to cite by name researchers that I am criticizing. Anyone reading the paper who has done this kind of study will recognize it. So I prefer to leave it as it is and not cause embarrassment..
7. Chemcal toxicity
Ln 219 (50) and mus be [50]. Response - the brackets have been changed
Reviewer 3 Report
Water-806672 Reviewer Comments: CT
Dr. Weis presents a collection of personal thoughts about the current state of scientific research on microplastics and their role in ecosystems. The review addresses several areas that should be the focus of future research on microplastics and highlights several important studies that have shown interesting results. The paper is very well written and present a well laid-out argument for the need for standardized methods in this line of research. I believe this paper could be acceptable for publication “as-is”, since it is well-researched and scientifically sound. However, I have a few comments for the author to consider. Most significantly, the author recommends cessation of the type of study that has so far been applied to microplastics research; namely small, local studies where microplastics are either quantified in ambient water and/or the bodies of aquatic fauna OR the reporting of ingestion of microplastics by a type of organism that has not yet been reported on. While I agree that these studies can be misleading in the broader picture, I disagree with the discouragement of their publication altogether. I hope that the author can see that many researchers are only able to work within the bounds of their research dollars and are best able to capitalize on relatively straightforward work that can be done by undergrads and lab techs using common equipment (i.e. plankton nets, light microscopes). It’s true that the findings of such studies often cannot be compared between studies and thus does not move this line of research forward significantly, however, it still may be informative and useful for regional environmental managers. Instead of recommending that this research not be performed, I suggest that it should be encouraged towards smaller journals focused on regional ecologies. Additionally, I support the publishing of new instances of organisms that are found to ingest microplastics. While this type of research may not be hugely exciting, I believe these types of studies should be encouraged so that we may get closer to discovering which organisms are exceptions to the rule. This type of finding would be very important to the field of microplastics research (as the author states) but is not likely to happen if researchers are discouraged from looking.
Specific Comments:
L25: It would be interesting to know the lower end of the range of microplastics size. How small have particles been observed at? It would be interesting to see if these particles get as small as some common phytoplankton. In general, it seems that studies examining microplastic ingestion/physiological effects in the lower food web (phytoplankton, zooplankton and macroinvertebrates) will be particularly important since the ecological risks surrounding mps seem to be mostly “bottom-up” processes. This is alluded to in the article at several points but could be stated more directly.
L140-145: It seems like mesocosm studies would be particularly well-suited for mps research, since they often involve tanks placed within natural environments while allowing for some degree of experimental control by researchers. This could address many of the issues described in this paragraph. Another thought: microspheres are often used in place of microfibers in experimental studies even though they are found less often in natural environments. It seems that the primary reason for this is that microspheres are a more available research tool. I would be interested to hear of any studies that successfully replicated microfibers in an experimental study, or if the author has a suggestion for an alternative to microspheres that is easily accessible to scientists. I appreciate the idea of collaborative research between materials scientists and ecologists working on this issue. Have there been any successful studies that were able to utilize microfibers in place of microspheres?
L175: define the acronym PCB
L225: see above comments. I disagree slightly. I encourage the author to consider my comments and rephrase this sentence in a way that does not rule out researchers in small environmental departments with limited resources.
L229: see above comments. I disagree slightly. These studies are important, and there may be appropriate journals for this type of research.
L231-233: again, researchers will be limited by what is available. It is a little more complicated than just asking scientists to stop using microspheres when an alternative is not available. This is an opportunity to encourage innovation in methodology and collaboration with other scientific disciplines.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
