Long Term (1998–2019) Changes in Water Quality Parameters as a Function of Freshwater Inflow in a River–Bay Continuum
Round 1
Reviewer 1 Report
The paper aims to identify the distribution of water quality parameters in the Delaware Inland Bays watersheds and the potential sources of the nutrient load in the freshwater inflows. The authors succeeded showing how concentration of the parameters in the different basins vary but they did not provide detailed information on the long-term temporal change. Judging from the title, one would assume the change in agricultural territories (one of the main point the authors bring up at the beginning) would be discussed with relevance of time and the temporal change in the concentrations.
To improve the practical application of the results the authors should revise the sections considering the source identification of the nutrients. What can be done to achieve the desired water quality based on the findings?
Some other comments considering the so
Considering both agriculture and wastewater, excluding substantial technological improvements, ammonium, nitrate (and nitrite) and phosphorous have a well distinguishable discharge patterns. In the winter nitrification slows down therefore ammonium concentration increases and parallel to that nitrate concentration will somewhat decrease. The authors mention that the ammonium concentration is is positive correlation with the temperature which is in contrast to what is normally seen in a municipal wastewater treatment plant. Could the authors go into more detail about what the type of wastewater treatment plants are they write about to resolve this contradiction? What is the source of the airborne ammonium contamination mention in l. 449?
The statistical analysis pointed out that the water quality parameters are a factor of freshwater/brackish water but only the wastewater treatment plants were pointed out as identified sources. The change in phosphorous correlating with chlorophyll-A is to be expected, but does not tell about what the source exactly is. The improvements of the wastewater treatment plants are mentioned but it is not elaborated whether that included only P removal enhancement or by any chance N removal was also improved. It is suggested to revisit the values between 2003-2019 to see whether the correlation results change.
Nitrite and nitrite are on the other hand are thought to be a result of agricultural activities. What are the differences between the watersheds considering agriculture? Which basins are more affected by poultry? Can this be linked to the results?
Other comments in the order of reading:
Highlights - the journal does not have criteria for highlights or the number of characters, therefore abbreviations can be fully omitted - Ag is confusing for the first read, based on the logic of using N and P in the next paragraphs one might think that silver dominates the Delaware Inland Bay watersheds instead of agriculture
Abstract is started very abruptly, one or two sentences of introducing the topic importance and/or the area in question would help the reader position themselves. Are the nitrate-nitrite values in nitrogen equivalent? Then please include the N in the abbreviation. Ammonia is most likely present in the water courses in ammonium form therefore it would be better to use ammonium and NH4-N.
It would be better if the font size in Figure 1 was larger.
Lines 124-126: Please check and rephrase the sentence, it seems like something is missing.
Statistical analysis: what level of r do the authors consider as significant correlation? Please include that in the methods section.
The tables should include the units either in the caption or after the parameter in the table (e.g. Q in table 1)
All of the notations and abbreviations should be explained before using them in the short form. E.g. PC1, PC2 and PC3 are explained in the text paragraph later than their first appearance.
Figure 4 is impossible to decipher. Maybe larger figure size with smaller markers and possibly dashed lines connecting the markers could improve the clarity of the chart.
Lines 314-319: there are two sentences here that mean the same.
Author Response
Reviewer 1:
The paper aims to identify the distribution of water quality parameters in the Delaware Inland Bays watersheds and the potential sources of the nutrient load in the freshwater inflows. The authors succeeded showing how concentration of the parameters in the different basins vary but they did not provide detailed information on the long-term temporal change. Judging from the title, one would assume the change in agricultural territories (one of the main point the authors bring up at the beginning) would be discussed with relevance of time and the temporal change in the concentrations.
To improve the practical application of the results the authors should revise the sections considering the source identification of the nutrients. What can be done to achieve the desired water quality based on the findings?
Response: Our goal for this paper is to present role of freshwater inflow in transporting nutrients. Source tracking of nutrients is not the scope of this study. We agree the word “poultry dominated” and “agricultural” in the title is confusing hence we have edited our title and highlights following your suggestion.
Some other comments considering the so
Considering both agriculture and wastewater, excluding substantial technological improvements, ammonium, nitrate (and nitrite) and phosphorous have a well distinguishable discharge patterns. In the winter nitrification slows down therefore ammonium concentration increases and parallel to that nitrate concentration will somewhat decrease. The authors mention that the ammonium concentration is is positive correlation with the temperature which is in contrast to what is normally seen in a municipal wastewater treatment plant. Could the authors go into more detail about what the type of wastewater treatment plants are they write about to resolve this contradiction? What is the source of the airborne ammonium contamination mention in l. 449?
Response: The seasonal discharges of wastewater from wastewater treatment plants to the Canal is higher during summer season compared to winter, which can be seen from the correlation between NH4-N and temperature. We have added text to clarify this in line 454.
The statistical analysis pointed out that the water quality parameters are a factor of freshwater/brackish water but only the wastewater treatment plants were pointed out as identified sources. The change in phosphorous correlating with chlorophyll-A is to be expected, but does not tell about what the source exactly is. The improvements of the wastewater treatment plants are mentioned but it is not elaborated whether that included only P removal enhancement or by any chance N removal was also improved. It is suggested to revisit the values between 2003-2019 to see whether the correlation results change.
Response: Developments (Introduction: 2nd para, Discussion first para), Agricultural land (Intro: 3rd para and in others), and wastewater treatment plants are the major sources in Sussex County. Factor analysis identified freshwater inflow are altering water quality parameters, which is because of the transport of surface runoff to the Bays. This is discussed in Discussion (…). As there are not much study in the Bays’ hydrodynamics and processes regarding Chl-P relationship that relationship in the Bays cannot be explained. However, the positive relationship was identified in other Bays/Estuaries system, which is cited in line 434-442. We thought over explanation the reason of that relationship based on other systems’ data would be vague and kept it simple by recommending that type of study in the future (with a sentence line 440-442)
Also, there is no explanation on N or P removal enhancement by wastewater treatment plant.
Nitrite and nitrite are on the other hand are thought to be a result of agricultural activities. What are the differences between the watersheds considering agriculture? Which basins are more affected by poultry? Can this be linked to the results?
Response: Agricultural land and Poultry are dominant in Sussex County as a whole (discussed in Intro para 3) and all of the bay systems mentioned here are located in that County. We have identified dissolved nitrogen are transporting through surface runoff and stated that the surface runoff would have major fractions of dissolved nutrients. Also, we have identified these dissolved nutrients are higher than the growing season’s applicable standard (discussed in Discussion 2nd and 3rd para) in most of the Bays. From the water quality stand point, we think sustainable management of nutrients in these ag land is important for the healthy Bays and have reiterated by means of this paper.
Other comments in the order of reading:
Highlights - the journal does not have criteria for highlights or the number of characters, therefore abbreviations can be fully omitted - Ag is confusing for the first read, based on the logic of using N and P in the next paragraphs one might think that silver dominates the Delaware Inland Bay watersheds instead of agriculture
Response: “Ag” is deleted. We have added one bullet in the highlight.
Abstract is started very abruptly, one or two sentences of introducing the topic importance and/or the area in question would help the reader position themselves. Are the nitrate-nitrite values in nitrogen equivalent? Then please include the N in the abbreviation. Ammonia is most likely present in the water courses in ammonium form therefore it would be better to use ammonium and NH4-N.
Response: Added a sentence in abstract and made suggested changes.
It would be better if the font size in Figure 1 was larger.
Response: Fixed
Lines 124-126: Please check and rephrase the sentence, it seems like something is missing.
Response: Fixed
Statistical analysis: what level of r do the authors consider as significant correlation? Please include that in the methods section.
Response: We have considered significant based on p-value. We know with this type of multivariate data r of 0.2-0.3 also considered significant as with the existence of dependency on multiple variables, and we are aware r in that range for water quality variables are available in literatures. A sentence explaining that has been added in line 183-184.
The tables should include the units either in the caption or after the parameter in the table (e.g. Q in table 1)
Response: Unit of measurement for flow is mentioned earlier in the caption, we have moved so that it is easily visible.
All of the notations and abbreviations should be explained before using them in the short form. E.g. PC1, PC2 and PC3 are explained in the text paragraph later than their first appearance.
Response: PCA components are discussed in 3.2 Statistical analysis section prior to mentioning in the result section
Figure 4 is impossible to decipher. Maybe larger figure size with smaller markers and possibly dashed lines connecting the markers could improve the clarity of the chart.
Response: Fixed. This figure is improved. As dissolved N has more effect of freshwater inflow, with the use of that, figure is improved in clarity.
Lines 314-319: there are two sentences here that mean the same.
Response: Fixed
Reviewer 2 Report
The manuscript explores a very important and urgent problem of water quality. The main advantage of the work is a 20-year monitoring period, during which it was possible to statistically reliably assess the direction and obtain quantitative characteristics of changes in the hydrochemical characteristics of watersheds intensively used in agriculture.
The disadvantage of the manuscript is the vagueness of the designations used for the forms of nutrients, which should be brought to the standard for hydrochemical studies: PO4-P should be replaced with P-PO4, NO2_3 should be replaced with N-NO2_3, NH3-N should be replaced with N-NH4. Then it will be clear that the concentrations in mg/L are calculated for the elements P and N, and not for their oxygen or hydrogen forms. The concentration units also need to be corrected: mgL-1 and μgL-1 should be replaced with more traditional mg/L and μg/L, salinity in parts per thousand should be replaced with ‰. It is also necessary to clarify which fractions of biogenic elements were measured: dissolved or total (dissolved + suspended). If dissolved forms were measured, the designations should be: dissolved nitrite+nitrare, dissolved ammonium, dissolved phosphate. This is of fundamental importance for the interpretation of the results. In Table 2, the chloride concentration should be rounded to whole numbers (for example, 9818.8 ® 9819), and dissolved oxygen and pH, if data allow, one decimal place more accurate (for example, 8.1 ® 8.10, 7.6 ® 7.62).
Comments for author File: 
Comments.pdf
Author Response
Reviewer 2:
The manuscript explores a very important and urgent problem of water quality. The main advantage of the work is a 20-year monitoring period, during which it was possible to statistically reliably assess the direction and obtain quantitative characteristics of changes in the hydrochemical characteristics of watersheds intensively used in agriculture.
The disadvantage of the manuscript is the vagueness of the designations used for the forms of nutrients, which should be brought to the standard for hydrochemical studies: PO4-P should be replaced with P-PO4, NO2_3 should be replaced with N-NO2_3, NH3-N should be replaced with N-NH4. Then it will be clear that the concentrations in mg/L are calculated for the elements P and N, and not for their oxygen or hydrogen forms. The concentration units also need to be corrected: mgL-1 and μgL-1 should be replaced with more traditional mg/L and μg/L, salinity in parts per thousand should be replaced with ‰. It is also necessary to clarify which fractions of biogenic elements were measured: dissolved or total (dissolved + suspended). If dissolved forms were measured, the designations should be: dissolved nitrite+nitrare, dissolved ammonium, dissolved phosphate. This is of fundamental importance for the interpretation of the results. In Table 2, the chloride concentration should be rounded to whole numbers (for example, 9818.8 ® 9819), and dissolved oxygen and pH, if data allow, one decimal place more accurate (for example, 8.1 ® 8.10, 7.6 ® 7.62).
Response: Surface water samples were analyzed for dissolved ammonia for the entire 20 years, we have provided EPA method for the dissolved ammonia analysis, lab has not analyzed ammonium form, hence we have reported ammonia nitrogen as suggested as N-NH3. Authors have agreed to all other suggestions mentioned by Reviewer 2 and made changes accordingly.
Reviewer 3 Report
The authors examined the relationship between freshwater inflow and water quality parameters in five watersheds draining to the Inland Bays using 22 years of long-term flow and water quality data. The objective of the paper is clear, and the methods are adequately applied to test research hypotheses. The following issues need to be addressed before the manuscript can be accepted for publication.
Major comments
- The manuscript can be tightly organized. In particular, I encourage the authors to create subheadings for both results and discussion sections to summarize the main findings of the research more succinctly.
- While generally well-written, the authors need to proofread the manuscript before resubmission as there are some formatting inconsistencies (e.g., space between sentences and missing punctuation marks). Also, please avoid using colloquial words (e.g., get).
- The results section needs close examination. I found that the reporting of the results is inconsistent with the information in Tables. See my comments below.
- The discussion section should not repeat the information found in the results section. Some sentences can be omitted for cogent discussion. See my comments below.
- The authors better display the information shown in the Tables. Table 1: p values can be shown in parenthesis. Alternatively, the authors can use “*” to show statistically significant p values. In Table 2, the authors better use the same decimal points for consistency. Additionally, it is easier for readers to read if all decimal points are lined up in the same place. Table 4 does not report show significance values.
- Some figures can be updated to improve readability. In Figure 1, the place names are too small to read. The inset map could focus on the USA rather than showing the entire world. Also, Subtable numbers (A) and (B) can be placed in the upper left corner of each figure without overlapping with the figure lines. Report salinity unit in Figure 2. What does the length of the whisker represent? One legend box can be removed since both legends are identical.
Other comments
Line 111. Change “gets” to either “obtains” or “receives”.
Line 142. Remove extra space between sentences.
Line 179. Need a citation for modified Anderson Classification System
Lines 188 and 189: To be more precise it should refer to Table 1 (B).
Lines 192-193. The range of NO2_3 is based on average values.
Line 195. Figure S1. The same information is found in Table 2. Ditto for line 198 when referring to Figure S1.
Line 319-321. Check this sentence as the information looks inaccurate.
Line 316. Can the authors report the changes in those areas?
Line 327. Remove extra space between sentences.
Lines 345-346. Any newspaper articles or other information that can substantiate this statement?
Lines 376-378. Any citations to support this statement?
Lines 402-405. This sentence belongs to results.
Author Response
Reviewer 3:
The authors examined the relationship between freshwater inflow and water quality parameters in five watersheds draining to the Inland Bays using 22 years of long-term flow and water quality data. The objective of the paper is clear, and the methods are adequately applied to test research hypotheses. The following issues need to be addressed before the manuscript can be accepted for publication.
Major comments
- The manuscript can be tightly organized. In particular, I encourage the authors to create subheadings for both results and discussion sections to summarize the main findings of the research more succinctly.
Response: We would like to keep the way it is as things are interrelated and there is no strict distinctive parts.
- While generally well-written, the authors need to proofread the manuscript before resubmission as there are some formatting inconsistencies (e.g., space between sentences and missing punctuation marks). Also, please avoid using colloquial words (e.g., get).
Response: Fixed
- The results section needs close examination. I found that the reporting of the results is inconsistent with the information in Tables. See my comments below.
Response: Fixed
- The discussion section should not repeat the information found in the results section. Some sentences can be omitted for cogent discussion. See my comments below.
Response: Fixed
- The authors better display the information shown in the Tables. Table 1: p values can be shown in parenthesis. Alternatively, the authors can use “*” to show statistically significant p values. In Table 2, the authors better use the same decimal points for consistency. Additionally, it is easier for readers to read if all decimal points are lined up in the same place. Table 4 does not report show significance values.
Response: Table 1, we are keeping it as it is, as it is a different way of showing than reviewer suggested. Table 2, we have improved following reviewer’s suggestion, only for DIN and DIP we have high decimal points as these concentration are very small. Table 4, Fixed.
- Some figures can be updated to improve readability. In Figure 1, the place names are too small to read. The inset map could focus on the USA rather than showing the entire world. Also, Subtable numbers (A) and (B) can be placed in the upper left corner of each figure without overlapping with the figure lines. Report salinity unit in Figure 2. What does the length of the whisker represent? One legend box can be removed since both legends are identical.
Response: Figures are improved following reviewer suggestion.
Other comments
Line 111. Change “gets” to either “obtains” or “receives”.
Response: Fixed
Line 142. Remove extra space between sentences.
Response: Fixed
Line 179. Need a citation for modified Anderson Classification System
Response: Fixed. Copied a link.
Lines 188 and 189: To be more precise it should refer to Table 1 (B).
Response: Fixed
Lines 192-193. The range of NO2_3 is based on average values.
Response: Fixed
Line 195. Figure S1. The same information is found in Table 2. Ditto for line 198 when referring to Figure S1.
Response: Fixed
Line 319-321. Check this sentence as the information looks inaccurate.
Response: Fixed. Sentence edited.
Line 316. Can the authors report the changes in those areas?
Response: Not sure where the reviewer is referring to. If this should be line 326, we have a figure in supplementary materials that shows that changes.
Line 327. Remove extra space between sentences.
Response: Fixed
Lines 345-346. Any newspaper articles or other information that can substantiate this statement?
Response: Authors have seen pictures taken from local citizens and recently authors have seen these in the areas frequently
Lines 376-378. Any citations to support this statement?
Response: Estuarine/Bay processes study is very limited in the area.
Lines 402-405. This sentence belongs to results.
Response: It does, I am keeping this there so that it would be easy for reader to better understand the sentences after.
Reviewer 4 Report
1. When studying the impact of biogenic elements on water bodies, for completeness of the study, it is also highly desirable to evaluate the content of silicic acid, dissolved inorganic phosphorus (DIP) and total dissolved phosphorus (TDP), organochlorine and organofluorine pesticides.
2. The conclusions seem more like a summary of the results. Please improve them.
3. Please improve figure 4.
Author Response
Reviewer 4:
1.When studying the impact of biogenic elements on water bodies, for completeness of the study, it is also highly desirable to evaluate the content of silicic acid, dissolved inorganic phosphorus (DIP) and total dissolved phosphorus (TDP), organochlorine and organofluorine pesticides.
Response: The suggested analysis of other biogenic elements were beyond the scope of the present study.
- The conclusions seem more like a summary of the results. Please improve them.
Response: Fixed
- Please improve figure 4.
Response: Fixed
