Phytoplankton–Macrophyte Interaction in the Lagoon of Venice (Northern Adriatic Sea, Italy)
Round 1
Reviewer 1 Report
General remark
The paper involves an analysis of a significant amount of data concerning the phenomenon of water improvement and the shift for phytoplankton to macrophyte primary productivity in the coastal lagoon. It is a complex issue as multiple factors could be involved. Is it a coincidence related to some hydrological effects or a result of management (transplantation of plants, reduction of nutrient discharge to the lagoon)? If it is impossible to identify the driving force than it should be discussed.
Specific comments
In my opinion, the article title is too abstract, could be closer to the topic. The results show competition rather than mutualism, whereas the term ‘co-existence’ doesn’t describe type of ecological interaction.
In the introduction few lines could be dedicated to the Light: nutrient hypothesis explaining the mechanism of light limitation as a primary factor or another theoretic background. It seems to me water transparency and the factors regulating it at a larger scale (riverine runoff, seawater inflow into the lagoon) and local scale (macrophyte stands preventing resuspension and inhibiting phytoplankton growth) should be highlighted and discussed.
Table 1. The reported numbers are moved to the next line. Edit or report one digit after the comma in reported values. The reported mean statistic do not match the applied statistical test, report median values, or min-max values. Explain what is the single number from each year (annual mean, single measurement).
Table 2. Indicate units.
Table 3. Format table. The p values in a single line.
Figures 3-4. Specify what is the confidence limit.
Line 183. Rephrase ‘the data were averaged’
Line 184. I suggest to present Table 2 and Figures 2, 3 and 4 as Supplementary materials, and consider making graphs for different periods (‘regimes’).
Line 210 Consistency in reporting a number of digits after comma for the same parameter over the entire manuscript is lacking.
Line 265-266, 267 The trend could not be reported if not significant. No statistical conclusion could be derived.
Section 4.5 Please add average numbers for the parameters within each cluster to show the magnitude of change (in terms of WFD class?). It is also confusing to relate the overall conclusion of the paper about the improvement of water quality to the result section, could the improvement be seen on annual average parameters or only for the spring period? Macrophyte starts to recolonize the area in 2005, it would be interesting to have some analytical results of what was before and after.
Figure 8, Line 123 Clarify/indicate which station, alternatively add station as a factor. It is confusing to read in the discussion that the environmental pressures and natural conditions are distinct among the stations.
Line 307 ‘north lagoon’ change to ‘northern part of the lagoon’.
Line 308. Rephrase ‘in two of the areas of the three considered for this study’
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In general the manuscript is very well written and informative. Specifically, I have the following suggestions/ question:
- The data in Table 2 is best placed as an appendix. The same for information presented graphically in Figure 2.
- While the authors refer to information derived from Landsat satellite imagery and the BOMBER program, there are no graphical examples to support % coverages discussed in Section 3.3.
- Present data produced by the BOMBER program.
- Please discuss how you distinquished seagrass and macrophyte spectral signals and distribution from the multispectral satellite data?
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
This study is to show relationship between macrophyte, phytoplankton and water quality based on the long-term water sample data. The authors concluded that the increase of macrophyte is correlated with chlorophyll a as a proxy for phytoplankton, however, the presented results do not support this relationship. Even they would extract 2013-2017 data, I think this relationship is not statistically valid, though I am not sure why they did not do show that. I would really like to know why macrophyte coverage dramatically increased in 2013. Also, what made another high macrophyte trend in 2007-2009 as well as the low trend in 2010-2012? In addition, what could be a reason for the spike of chlorophyll a concentration in 2001? The authors do not discuss these interesting points.
The data set is quite valuable, but the main message is not supported by the processed data and analysis, so I cannot recommend the manuscript for publication at this stage.
Additional minor comments:
Line153: Did the authors use their own in-situ data? If so, please describe the sampling/monitoring method. Are the coverage maps validated?
Line289: Rising temperature is not a significant trend except for one location. Please remove this part.
Line 307-314 & 355-357: Please clarify how these findings relate to this study.
Table 1: Column widths should be modified to fit each value in a single line.
Why are the three stations named station 1, 3, and 5, instead of 1, 2, 3, or more descriptive names such as north, middle, south, etc.? If these are proper nouns, “s” needs to be capitalized (i.e., Station 1, St.1).
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Thanks to the authors for revision. The manuscript has been largely improved. It is suitable for publication after proofreading and correcting minor errors (e.g., part of the chlorophyll a plot in Figure 2 is missing).
Author Response
Dear Reviewer,
as you suggested we corrected figure 2 and made other corrections to improve the English (marked in yellow in the text).
Thanks for your comments which improved the manuscript.
With best regards
The authors
