Silting Process and Loss of Posidonia oceanica Meadows in the Tyrrhenian Waters of Calabria (Southern Italy)

Round 1

Reviewer 1 Report

Check the alphabetical order in the references

Comments for author File: Comments.pdf

Author Response

Pag. 2 Line 51. We have deleted the following statement: L. (Delile)

Reviewer 2 Report

This paper presents an interesting study on the burial process of Posidonia in the Mediterranean Sea. In my opinion this research is very valuable in a context of rapid recent changes in the Mediterranean Sea areas due to both human and climatological factors. However, I believe that the manuscript should be improved in several aspects before its publication for an international audience.

Above all, the methodology and results of the Case study: Marine Regional Park “Scogli di Isca” must be revised, e.g., the monitoring program (granulometric analysis and the silting rates) should be better detailed. Thus, both sections 2 and 3 should be rewritten in more detail.

Why the Calabria Tyrrhenian coasts represent a favourable setting to study the resilience of Posidonia oceanica Meadows to silting process? This important statement must be justified and explained to understand why this area, and in particular the case study area, has been chosen. It is not clear the relationships between the geomorphological features of the debris source areas, represented by fluvial basins, and the distribution of Posidonia meadows in the monitored area.

Other aspects that need to be completed/modified are listed below.

 

Lines 93-97 about the geomorphological features of fluvial catchments place the region in a high state of landslide risk is poorly described. Most of the introduction explains various aspects of Posidonia decline but does not have a background on the research done on fluvial aspects.

Line 114 The Fig. 1 Geological map showing the main lithologies is not cited in the text and must be moved to the 2.1 Study area.

Lines 145-148 Must be completed with the physical factors drive the hydrodynamics in this coastal area, for example detailing the   currents near the coast and the littoral drift, which is in the Fig. 1, but isn’t described in the text. The coastal drift current may be a decisive factor and has not been indicated in the work, although it is marked in the figure by black arrows.

 

Lines 238-234 Must be completed.  The monitoring program conducted as citizen science by separate stages, but when and where the locations? A map or diagram (or table) with the monitoring program including sample locations and periods it would be necessary to illustrate and clarify the methodology followed between 2000-2010

Lines 315-323 A graph showing the evolution of the average silting rates cm/year values would help to better understand these results.

Lines 331-334: Authors must locate Fig.4 pictures on a map and indicate the sediment rate of each of them.

Lines 393-412 This section should be rewritten to better understand the relationship between grain size and geomorphological features. As detailed in the text, it is a theoretical hypothesis but not very well supported by the data and results obtained in this research work.

Lines 419-423 “The geomorphological study highlighted a high predisposition from the fluvial basin areas to undergo erosion processes and to furnish abundant debris materials that the fluvial waters carry in shelf areas. For these reasons, a monitoring program was planned in 2000-2010, with the scope to assess the increasing burial level at the base of a Posidonia oceanica meadow. Several detritus samples were analysed to study their composition and provenance.”

In my opinion, the outcome introduced by the authors at conclusions is not supported by the results obtained by them. On the other hand, the conclusions include methodological aspects that should not be in this section. Thus, the Conclusion should be rewritten highlighting instead the results obtained by the authors in this study.

 

Author Response

Please, see the file attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Well, I think that my recommendations in the table are clear enough.

Only a minor revision

row 104 I suggest: on the study of the features of the sampled sediments...

Author Response

Pag. 3 Line 116 - In the new version of the revised manuscript, we have added, at pag. 3 line 116, the following statement: "on the study of the features of sampled sediments...."  

Reviewer 4 Report

The study about Posidonia beds is of importance, since around the world coastal areas are suffering from human impacts, pollutants are most often measured but sedimentation rates in highly populated areas are of importance since human related activities such as industry, tourism and the construction of housing itself conveys changes to the environment and the associated watershed.

Overall, the paper is very well written and the structure is easy to read, figures, tables and pictures are clear and provide enough information as to the points of the study, I only have few comments that are down below. I am not attaching any document file.

Line 64 I would place citations after Posidonia decline topic…also it says several authors and there are only three named, you could probably say (e.g. Boudouresque et al. 2012; Marbà et al. 2014; Roca et al. 2014)

Line 210, it is not so clear why this site was chosen as representative of the whole coast, maybe one or two lines describing why it was chosen as representative would suffice, since it is a National park, and I understand it is protected, why all the other Posidonia beds could be represented here? Is it because of the surrounding activities? Are the other Posidonia beds not protected?

The box corers were placed at the same depth, positioned 20 cm above the sea-bed and strictly approached at least 1 m apart. What do you mean with strictly approached at least 1 m apart?

Secondly, it was analysed yearly the ecological conditions of the meadow through diving activities. I think it should say: Secondly, the ecological conditions of the meadow were analysed through diving activities.

Then, personal diving activities verified and examined every notification to check the meadows' position, extent and limits. I do not understand what do this means, do you mean that the diving logs once uploaded? were verified and then the notification of the coordinates, extension and limits of the meadow were examined and registered in a data base?

I believe that at some point some precisions need to be done, as a I am reading further in material and methods section and then results, divers and fishermen collected data from a data card along the coast, is this correct? And divers from the local dive center at the “experimental” meadow collected data on seagrass? If this is correct it is not clear enough, some notation should suffice. Also, were divers counting the leaves always the same? How do you ensure that the measurements were done correctly?

I have no further comments.

Author Response

Please, see the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

the authors have improved the article following the recommendations, so in my opinion, the research can be published in the present state.