Role of Chironomus plumosus (Diptera, Chironomidae) Population in the Central Zone of the Shallow Lake Trasimeno (Italy)

Round 1

Reviewer 1 Report

Dear authors,

 

Thank you for putting up this piece of exciting article. Below please find suggestions for improvement. Other comments are in the PDF file

Writing/English

1.      All other sections are written well, except the introduction, both in flow and structure

2.      The flow of the introduction section needs to be improved. From the write-up, these insects are both beneficial and a nuisance. It would therefore be good to:

3.      Include information on their distribution (global to local), and economic importance

4.      Then zero in on the negative effects. How they have affected residents and tourists; Any quantifiable impacts? How many tourists visit the site? What financial losses are likely to occur  (occurred) as a result of the nuisance?

5.      State the measures that have been initiated to manage them, with their limitations. And state the gaps that have made it impossible to keep them below annoying levels

6.      There is also a mention of negative effects of synthetic insecticides. Please indicate the chemistries that were (are) used and their limitations

 

Materials and methods

Largely okay. Only data analysis section is missing

Results and discussions

1.      The results are adequately discussed

2.      Reduce density figures to one decimal point

 

3.      The discussion flows well

 

Comments for author File: Comments.pdf

Author Response

RESPONSE TO REVIEWER #1 COMMENTS

We would warmly thank the Reviewer for all the kind comments emphasizing that the manuscript is interesting from a scientific point of view, methodologically sound and clearly presented.

Regarding the Introduction, we have rewritten this section, fully agreeing with the suggestions. We have in fact integrated and rearranged it in the logical sequence suggested by the Reviewer. In the current version, the Introduction starts with the information on Diptera-Chironomidae, in particular on Chironomus plumosus, species that generates the greatest disturbance. After, we address the aspects related to its distribution, its ecological importance and the negative effects due to the nuisance that its swarms cause to tourism when in summer evenings they are attracted by the lights of human activities. Finally, we list the measures put in place to contrast them, avoiding the use of synthetic insecticides (pyrethroids, no longer used in the study area since 2012). Regarding the sentence concerning the experimental capture of chironomids with the "ChiroBoat", we rewrote it, and also now the key results of the research project funded by the Brunello and Federica Cucinelli Foundation have been better highlighted.

In the Material and Methods section, we added the Data Analysis paragraph, as required.

With regard to the Results and Discussion section, we agree that in order to make the text easier to read, the best choice was to limit the decimal digits of density data to one.

Finally, we accepted all the corrections noted in the PDF, enhancing the quality of the manuscript text.

Reviewer 2 Report

The manuscript is of interest considering one of the unfavorable consequences of global warming, the increasing of pest species in altered climatic conditions.

The comparison of two distant periods using the same sampling strategy is surely a heavy point enhancing the value of the manuscript.

The addition of some information about water temperature and water levels in the two investigated periods should be useful to better interpret the reasons of the observed differences in years.

The reasons of reduction of aquatic vegetation in the center of lake in years should be better explained

I suggest to separate Results from Discussion. The results are mixed with literature citations, the comparison with other lakes is better included in a Discussion paragraph

A statistical analysis considering different factors (years, seasons, lake depth (littoral-central) could substantially ameliorate the manuscript

Row 142: how were this numbers (10026, 14585, 12) calculated?

Row 224 The low observed numbers of instar II larvae is probably bound to sampling strategy, this instar is not easily sampled with the sampling strategy used in this research

Row 243: reed bed of ? please better formulate this sentence

Author Response

RESPONSE TO REVIEWER #2 COMMENTS

We thank the reviewer for his interesting and valuable comments on the manuscript.

 

Point 1:

The addition of some information about water temperature and water levels in the two investigated periods should be useful to better interpret the reasons of the observed differences in years.

With regard to the suggestions on the analysis of the hydrological levels and on the environmental temperature during these 20 years, we were able to highlight that:

- slightly different is the water level of Lake Trasimeno (with an average level about 20 cm higher in the 2018-2021 period, compared to 2000-2002); in addition, to better understand the hydrological levels of the lake, we added the lake bathymetry in Figure 1;

- while an increase in the average air temperature of about 0.4 °C is observed between the two periods. This could represent one of the causes of the current increase in the Chironomus plumosus populations, which is the most annoying species in the investigated area.

We have documented these data by adding two tables in the Supplementary Material, respectively Table S3 and S4.

 

Point 2:

The reasons of reduction of aquatic vegetation in the center of lake in years should be better explained

Unfortunately, we were not able to find valid references in the scientific literature to explain the causes of the disappearance during the last years of the bottom vegetation in the central area of the lake.

 

Point 3:

I suggest to separate Results from Discussion. The results are mixed with literature citations, the comparison with other lakes is better included in a Discussion paragraph

We thank the reviewer for the suggestion, but we decided to keep the two sections together, in order to make an immediate comparison between the results of the study on chironomid populations in the central area of Lake Trasimeno (present study) with the recently published data regarding the littoral chironomid populations in the same study area (published in Sustainability in January 2023).

 

  Point 4:

A statistical analysis considering different factors (years, seasons, lake depth (littoral-central) could substantially ameliorate the manuscript

We tried some statistical analysis to highlight the temporal variables, but we were unable to express sufficiently clear results. Therefore, for a possible comparison that could be made by readers and other researchers, we added in the Supplementary Material raw tables, that can offer a descriptive analysis of temporal variables, also presenting the data from the central area of the lake sampled in the years 2000-2002 (Tab. S2) and from the littoral area of the lake sampled in the years 2018-2021 (Tab. S5).

 

Point 5:

Row 142: how were this numbers (10026, 14585, 12) calculated?

These numbers are the number of specimens of each group, to better explain these numbers we added the Table S1 in the Supplementary Material.

 

Point 6:

Row 224 The low observed numbers of instar II larvae is probably bound to sampling strategy, this instar is not easily sampled with the sampling strategy used in this research

We corrected this sentence with the reviewer’s suggestion.

 

Point 7:

Row 243: reed bed of? please better formulate this sentence

We corrected the typo.