Phosphorus Retention in Treatment Wetlands? A Field Experiment Approach: Part 1, Hydrology

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study focused on the stormwater treatment areas (STAs) in the Everglades Protection Area of Florida, aimed to explore the impact of vegetation resistance on water flow and phosphorus retention. Through field experiments in STAs, the authors utilized sinusoidal discharge perturbations to measure changes in water depth and calculated hydraulic conductivity (K-value) as an indicator of vegetation resistance. It found that K-values can serve as a single parameter independent of vegetation type and flow conditions, effectively representing vegetation resistance. Besides, High K-values indicate low vegetation density and low resistance, while low K-values suggest the opposite. These discoveries are significant for wetland management because it helps optimize phosphorus retention by identifying areas of fast and slow water flow to enhance phosphorus removal. Additionally, this research method provides a cost-effective and practical tool applicable to hydrological models of wetlands with different vegetation types, having a profound impact on environmental restoration and scientific research on wetland ecosystems. However, I argue that some problems existing, additional explanations and modification should be supplemented.

(1) many sentences in the article are too long and contain multiple clauses, which makes it difficult to read. For example, "Field experiments, to seek alternative ways to estimate vegetation resistance in STAs, were conducted by generating small sinusoidal discharge perturbations superimposed on near-steady state flow conditions and measuring in situ water levels inside the wetland." This sentence contains multiple commas and conjunctions, making the sentence structure appear confusing.

(2) The spelling mistakes and inaccurate words in the article should be noticed. For example, ”STAs are large wetlands constructed to reduces phosphorus (P) from agricultural and urban runoff into the Everglades "Protection area." Here the "reduces" should be "reduce".

(3) Although the history and current situation of the Florida Everglades were introduced at the beginning of the article, the seriousness of the phosphorus pollution problem and its specific impact on the ecosystem were not explained in detail. This may make it difficult for the readers to understand the necessity and urgency of the research.

(4) The K value of water permeability mentioned in the paper is calculated through waveform data. Should error analysis be considered in the calculation process?

(5) Please add the explanation of the specific characteristics and differences of these wetlands, as well as the reasons for choosing STA-3/4 and STA-2 for experiments.

(6) The experiment was conducted only during a specific time period, and the hydrological conditions of wetlands can vary significantly with the seasons. As a result, the results may not reflect the full year.

Author Response

Pls see attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Major Comments:

1.      Abstract: Abstract should contain high-level findings of the study.

2.      Introduction:  the Introduction, the problem (line 51) should be better introduced before SFWMD is described. The problem (excess nutrients/P) should also be described in a larger context, for example by describing eutrophication issues worldwide. It would also be helpful for context to use the same units if possible, or related the typical concentrations (line 44) with WQBEL standards.

3.      Methods: This section would benefit from clearer descriptions (and maps) of the experimental site locations. There are two sites identified in the first paragraph, but the second site is not included in Section 2.1 Experimental Location. It would also be helpful to include some more information about the setting for readers not familiar with the Everglades and the SWA.

4.      The Transmissivity results seem to be compared to the vegetation density index visually, by superimposing the two maps. It seems a more rigorous statistical comparison would be warranted.

5.      Discussion: Some of the material in Paragraph 1 explaining the rationale for quantifying vegetation resistance parameters and P uptake dynamics is better suited for the Introduction.

6.      Conclusions: Additional information on how these results can be used by management, and also by managers in different ecological systems would add to the relevance of the paper.

7.      The references are mostly dated, with the most recent reference being from 2021. More recent relevant sources should be referenced.

Minor Comments

Lines 12:13. Sentence reads that STA are designed to (exclusively) remove P from a system. Since STA can also be used to remove for example N, suggest clarifying that STAs are used in the Everglades to remove P.

Lines 14:15. Consider adding how vegetation reduces P in STA (also include uptake?).

Line 42: There seems to be text missing related to P.

Line 44: Are these historic values of P, or current?

Line 47: SFWMD should be defined.

Lines 60-64: The left figure of Figure 1 would benefit from a legend identifying which color is the STAs. Some of the text is too small to be legible.

Line 72: I am not sure I understand this sentence. Is it P level?

Line 110: Cross-reference Figure 1.

Line 113: It is difficult to tell from Figure 1, but STA-3/4 does not look EAV dominated? Perhaps it’s terminology, but looks like maybe slightly over half the area is EAV? Or is it a subcell being used? Are these shown on map?

Lines 116-120: Keep tense consistent.

Lines 132-135: Interesting, looks highly engineered            

Line 127: STA34C3A wetland study. Is this a previous study? If so, reference here. Why is STA2C3 (EAV and SAV) not included in this experimental section?

Lines 154:160: Figure 2B is not very informative in current format. Suggest overlaying locations on a satellite image.

 

 

Comments on the Quality of English Language

The paper would benefit from improved quality of English. 

Author Response

Please see attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The question of reviewer relations was answered