Applying Generic Water Quality Criteria to Cu and Zn in a Dynamic Aquatic Environment—The Case of the Brackish Water Formation Strömmen-Saltsjön
Round 1
Reviewer 1 Report
Reviewer: The manuscript encompasses descriptive Cu and Zn water quality criteria guidelines and demonstrative approaches to improve and reach the ecological status of water bodies in Sweden. The manuscript is well written with extensive literature details. Clear take-home messages were generated in the conclusion part for edification and public awareness. However, reading your research article gives the impression of reading a thesis, please sharpen the objectivity of this work and be concise in sections 1 and 2. A major revision is requested for this manuscript.
Line 3: Title, <<Applying generic water quality criteria to Cu and Zn in a dynamic aquatic environment – the case of brackish the water formation Strömmen-Saltsjön>> Please revise the title, I think <<the>> of line 3 need to be removed.
Line 54-55: The sentence is not clear, please revise.
Line 61-64: The sentence is not clear, please revise.
Line 61-64: What are the end-points and conditions you mention here?
Line 81-84: Why this trend in marine versus freshwater conditions?
Line 109-110: Please use the same decimal digits for pH values and Ca2+ concentrations.
Line 127-132: Please add a reference to this claim.
Line 148-151: The sentence is difficult to understand, please rephrase.
Line 188: The Sub-title numbering should be 2.2.
Table 1: Please arrange the data from percentile 10th to 90th.
Line 253-255: The sentence is difficult to understand, please rephrase.
Line 255-258: The first statement was made on cations and the following one was quoted ions chloride (Cl-), which is inconsistent, please revise.
Line 357-358: Please rephrase the sentence.
Figure 3: How did you evaluate the lability of the complexes in this work?
Author Response
See attache file
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper presents an attempt at finding an optimal method to assess a possible threat posed by trace metals to a brackish-water ecosystem with complex interactions between fresh- and marine water masses. The Authors concentrated on chemical methods only, and chose copper and zinc as their “model” metals. In my opinion this was not the best choice, because the two metals in question play important roles in the physiological processes of many aquatic (and not only aquatic) organisms. This complicates the assessment of the impact of their bioavailable fraction as measured by chemical methods.
Already in the Introduction (lines 36/37) the Authors state that “studies exist that generally conclude that neither Cu nor Zn pose any threat to the aquatic environment”. It would be enough to put “zinc (or copper) contamination in aquatic environment” into e.g., Google Scholar to find out that this is definitely too strong a statement.
Towards the end of the Introduction (lines 137ff) the Authors describe difficulties of assessing trace metal impact upon an environment with changeable salinity conditions. This fragment should be concluded with discussion on the applicability of biomonitoring methods in such circumstances. The Authors do this farther in the paper, devoting a short chapter (3.5) to the necessity of employing biomonitoring methods, and rightly stating that these should concentrate on macrobenthic organisms. Unfortunately, they provide no references to relevant literature.
In short, discussing the applicability of chemical monitoring, the Authors should have devoted more attention to showing that biomonitoring is a necessary complement.
Some other points worth considering:
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The Authors have erroneously departed from the current rule of reporting salinity as a unitless value, without the “PSU”.
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Latin names (genera and species) should be in italics.
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Lines 212/213: Potential readers may be interested what is the origin of Cu and Zn in the Lake Mälaren?
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Line 232: The reference to figure 1 is irrelevant — one would expect a graph comparing sediment burial rates.
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Lines 263 ff (chapter 2.3) — The description of the Strömmen-Saltsjön water body is far from satisfactory. Judging from the description of the fish fauna (especially the abundant population of common bream), one can expect benthic fauna fairly abundant perhaps not in species, but in the biomass/number of individuals.
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Figure 2, upper graph: “freshwater inflow”, not “in low”.
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Table 4: Column headings are too complex, please, try to simplify.
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Do not split tables between pages!
Minor points have been marked directly in the text – see enclosed file.
Comments for author File: Comments.pdf
Author Response
See attached file
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The comments were well observed and responded to by the authors; the manuscript has also been greatly improved. I recommend the publication of the article.
