Toxic Effects of Heavy Metals and Organic Polycyclic Aromatic Hydrocarbons in Sediment Porewater on the Amphipod Hyalella azteca and Zebrafish Brachydanio rerio Embryos from Different Rivers in Taiwan
, Chi-Ying Hsieh 2,*, Hans-Uwe Dahms 3,4,5,*, Yu-Hsien Tseng 2, Jesse Chen 1, Meng-Chun Wu 2, Jin-Hyoung Kim 6 and Cheng-Han Liu 3Round 1
Reviewer 1 Report
Review
Paper title: Toxic effects of heavy metals and organic polycyclic aromatic hydrocarbons in sediment porewater on the amphipod Hyalella azteca and zebra fish Brachydanio rerio embryos from different rivers in Taiwan.
The authors used the amphipod Hyalella azteca and zebra fish embryos as test organisms to study possible toxic effects of important environmental pollutants such as heavy metals and organic polycyclic aromatic hydrocarbons contained in sediment porewater from rivers in Taiwan. They found that these pollutants affect survival rates, development and cardiovascular functions of tested organisms.
The results of this toxicological study highlight the importance of monitoring trace elements and PAHs in aquatic systems and expand our knowledge about their pollution effects and risk status for aquatic organisms and human health.
All these reasons explain the relevance of the paper by Shao-Yang Hu and co-authors submitted to "Applied Sciences".
General scores.
The data presented by the authors are original and significant. All conclusions are justified and supported by the results. The study is correctly designed and technically sounds. In general, the statistical analyses are performed with excellent technical standards. We authors conducted careful work which will attract the attention of a wide range of specialists focused on the freshwater toxicology and ecology.
Main concerns.
Figure 1 has to low resolution to be easily read. Please, increase the resolution of this figure.
L 169-174 and 180-183. This section should be presented in Materials and Methods.
L 176. First column should be "Site". Please, provide the description of codes in footnote.
L 198, 251, 256, 260. Please, indicate what vertical bars mean as you did in other captions (L 287, 295).
L 372-386. This section should be presented in Materials and Methods.
Specific comments.
L 19, "(HJ3, DG1, YS, SY, DB, AGD, WR and LK)". These abbreviations should be defined or even deleted.
L 27. Change “was significantly” to “were significantly”
L 75. Please, check the sentence "Research indicates that the…"
L 85. Change “relationship of” to “relationship between”
L 89. Change “collected” to “were collected”
L 100. Change “role for” to “role in”
L 120. Change “twice daily” to “twice a day”
L 149. Change “Results” to “Results and Discussion”
L 163. Change “sites, HJ7 and DG1,” to “sites HJ7 and DG1”
L 208. Change “low with about 1%” to “low at about 1%”
L 212. Change “highest toxicity” to “the highest toxicity”
L 228. Change “rate increased” to “rates increased”
L 236. Change “a normal development” to “normal development”
L 347. Change “H. azteca” to “Hyalella azteca”
L 372. Change “are expected” to “is expected”
L 373. Change “either results” to “either result”
L 393. Change “1 sites” to “1 site”
L 401. Change “is lower” to “are lower”
L 405. Change “IWBUs” to “Interstitial Water Benchmark Units”
L 408. Change “IWBUs” to “Interstitial Water Benchmark Units”
L 426. Change “oncluded” to “concluded”
L 427. Change “deformity rate” to “deformity rates”
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript presents an analysis of 35 sites for PAH and metals contamination in porewaters. This is predominantly a site survey, which is expanded to report the toxicity of the porewaters to amphipods and zebrafish embryos. The manuscript is long, but well written. There are some areas that need to be clarified before it is ready for publication.
General comments
L75. What do you mean by this sentence? Related to what specifically?
L76 change “involved in the aquatic food chain” to “bioavailable to the aquatic food chain”
Figure 1. It is difficult to read the labels on the map. Can the text be larger?
L105. Is there a pH range for survival, or just not suitable for pH<6?
Section 2.2 were the H. azteca from a culture? Or field collected?
L112 “compared to the control (80%) …” What is the 80%? Please specify if this is the quality assurance for test success or something else? Also, what was the control condition/test water?
L129 What concentrations of the salts were in the control solutions?
Methods. Was the field collected porewater filtered prior to exposure to the test organisms? If so, which filter membrane was used?
Sections 2.4 and 2.5 Can you provide the detection limits for each analyte, either here or in the supplementary material. This is important as many of the analytes reported in the results section are below the limit of detection.
Table 1. Are these results the changes in chemistry over 2 or 4 days? As the test assays differed, one was a 48-h exposure and the other 96-h exposure
Table 1. The pH increased in most of the samples over the acute exposure period. Why do you think this occurred?
Table 1. Please provide details of BK. Is this the blank? Is this the same as control? And were there measurements for 48 or 96 hours?
L163. I assume that you mean the increase in salinity at the field sites.
L180-185 ‘It was suggested …’ Reference? Who suggested that less than 75% survival for the amphipod would also have adverse effects for human health? The following sentences are confusing. They suggest that the more aquatic organisms that survive, the greater the impact on human health. This needs to be clarified. It is a big leap from amphipods to human health and care must be taken not to over-interpret the results without adequate evidence.
Figure 2, and sections 3.2 and 3.1. It would be useful to detail the actual concentrations of contaminants in the porewaters before showing their toxicity. This would give better context to the amphipod survival results.
L225. What recent research do you refer to? Is this research part of the same study in this manuscript? Need reference here, even if it is referred to as unpublished data from the lab.
L241. This is interesting. When you say the melanin content was more significant in the controls, significant how? Do you mean that there was more melanin present? How was the melanin content assessed?
Figures 6 and 7 could probably be combined, with the caption used to identify level of toxicity of porewater.
L279 delete ‘than’ to read ‘was less in the …’
L300 reword to say ‘was not detected in any of the porewater samples’.
L310 reword ‘was most abundant quantified PAH’ and say ‘was the most abundant PAH quantified in ..’
L313 Why are there high concentrations of PAH in livestock waste?
L317-319. Reconsider significant figures
I would prefer to see section 3.6, 3.7 and 3.8 presented before the organisms exposure tests. This is a preference based on giving context to the bioassay results.
Table 2 and table 3. define ND as not detected in the table captain. This should be reported as BLD – below the limit of detection, with the detection limit reported in methods or the supplementary material.
L339, add the word respectively before the full stop. Also I am not convinced that a r value (correlation) between 0.3 to 0.6 is moderate. My understanding is that 0.3 is saying that 30% of the data points are explained by the correlation. I consider that to be a very weak correlation. Can you provide evidence (references) as to why these boundaries were set for low, moderate and high correlations?
L340 delete the word ‘so’
L360-363. This isn’t quite clear, and I think it is misleading. There can be instances when metals and organic matter are both present, and in those cases the metals (eg copper) may adsorb to the organic matter, but that doesn’t mean that if one is present, so is the other. In the paper cited, there are a lot of factors that are not necessarily relevant to the studies here, such as the exposure route of the contaminants (food, water, skin).
L363-364 is OK
Section 3.9 This is interesting, and relevant for metal contaminated sites. However, the needs to be a statement in the first paragraph that these porewaters are also known to be contaminated with PAHs, so that these metals toxicity screening methods should not be solely relied upon to predict the toxicity of the porewaters.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript “Toxic effects of heavy metals and organic polycyclic aromatic hydrocarbons in sediment porewater on the amphipod Hyalella azteca and zebra fish Brachydanio rerio embryos from different rivers in Taiwan” is interesting and within the scope of the journal but some minor changes should be addressed:
- Please remove the gridlines from figures 2-5.
- In the introduction section it will be interesting to discuss briefly about the assessment of pollutant dynamic evolution of volatile organic compounds and volatile aromatic hydrocarbons in rivers (please see https://doi.org/10.37358/RC.19.10.7575).
- Please try to compare the obtained results with literature (please see https://doi.org/10.37358/RC.19.12.7725).
- I recommend to specify about the repeatability of the tests.
- I didn’t see in the text where are mentioned the figures 3,4 and 5.
- I recommend to short the conclusion section.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
