Invertebrate and Microbial Response to Hyporheic Restoration of an Urban Stream

Round 1

Reviewer 1 Report

The authors report about the biological response to restoration of river systems respectively the hyporheic zone. Over 4 years, 8 L interstitial water samples and 2 L surface water were taken always in November. Beside environmental relevant parameters like DOC, DO, nutrients the biological community is determined. The paper presents a lot of data which are evaluated by statistical approaches. The data and results are definitely very interesting but the presentation of the results should be cut/shorten. There are 8 Figures and 2 extensive Tables. Please try to shorten and summarize the result.  In chapter 3.1 there is a refer to Figure 3a and 3b but not to Figure 3c to 3d. Figure 3c is used in chapter 3.2 and Figure 3d in chapter 3.3., it is not nice that the reader has to turn the pages forward and backward. There is no refer to Figure 3e. Rearrange the text and all the figures in the hole manuscript. If possible combine result and discussion and make a chapter conclusion at the end.  

In the title you write “hyporheic restoration”, in the abstract “new urban floodplain restoration” and in the Introduction you write a lot about green storm water infrastructure. I think you report about changes after river restoration- please clarify and be consistent.

 

Please give some information about the new “urban floodplain restoration technique”, and define what you understand under hyporheic zone.

It seems (Fig 1) that the restored and unrestored sampling points are not so far away from each other. How far is it? How long are the restored and the unrestored parts of the rivers.

The samples were always taken in November. Are the same results expected for summer samples?

How long did it take to collect the 8 L interstitial water? How did you manage that the water just comes from a defined depth. 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,
your paper does a good job evaluating an engineered hyporheic zone on a urban floodplain. This is an interesting topic and the paper provides a scientific perspective on a field (restoration and hyporheic zone) that has only recently boomed. Please find below some comments that would improve the readability of the paper.

line 70: there is no need of Figure 1. if you really want to refer to a graphical representation of the hyporheic zone (HZ9, please choose one already published (e.g. Figure 1, Lewandowski et al., 2020 DOI 10.3390/w11112230).
line 73-95: please summarize the paragraphs considering only the information key to hypotheses testing. Refer to Figure 2 only in the material and methods.

line 97-98: add more recent reference e.g. Magliozzi et al 2019 (https://www.sciencedirect.com/science/article/pii/S1364815218301476), Mendoza-lera et al. 2017 (https://www.sciencedirect.com/science/article/pii/S0048969716326316)

line 101: Please rephrase. I'd recommend clarifying about the specific biological response or organisms you are referring to. What are the hypothesis for the processes/responses you are considering? There are several studies reporting on changes in taxonomic and functional
metrics to hyporheic flow, driven by in-channel structure often used in river restoration (e.g. bedforms, large wood), both field and modelling studies.
For example:
- Blaen et al 2018 https ://doi. org/10.1002/eco.1952
- Descloux et al 2013, 2014 https :// doi.org/10.1007/s00027-013-0295-6 , https ://doi.org/10.1016/j.scito tenv.2013.06.082
- Flores et al 2018 https ://doi.org/10.1016/j.ecole ng.2017.05.036
- Larsen et al 2011 https ://doi.org/10.1002/rra.1361
- Mathers et al 2014 https ://doi.org/10.1111/fwb.12430
- Magliozzi et al 2019, 2020 https://link.springer.com/article/10.1007/s00027-020-00745-9, https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.13381

line 103-110: I'd state the processes and related hypotheses addressed by the study
line 106: add more recent references

line 128: please be more specific, what do you mean by biological health?
line 145. why did you decide to install piezometer near riffle tail-out? there is surely an effect due to the riffle-pool. Please detail if there are sediment differences between sites
line 163-167: please add some info on sampling collection of pore water for chemical analyses as concentration of micropollutants decreases while out of the HZ (e.g. https ://doi.org/10.1016/j. scito tenv.2011.01.028)

section 2.4: I would clarify this section and explain sequentially and separately biotic from abiotic analysis. Did you carry out the same analysis for hyporheic and benthic invertebrates?
please refer to packages and functions for R software that were used. Please also report the formula for the two-way fixed effects approach and R packages /functions

Table 1: better to info on e.g. Bonferroni or Tukey test or log trsformation in Section 2.4 and keep the caption only to explain what reported in the table. Missing comment on "a", "b", "c" and combinations. Check also other captions

language: please avoid using so often the pronoun "we" in the methodology and results sections.

discussion:
would be good to reword the discussion thinking about the expected processes trigged by restoration and so the biological responses.
- discuss the limiting factors operating at this urban watershed in relation to the restoration actions carried out at sites,
- link to research studies that, although not addressing restored sites, have investigate biological responses to urban processes (e.g. sediment transport, wood, floodplain connection)

Author Response

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Author Response File: Author Response.docx