Unraveling Aquatic Quality Controls of a Nearly Undisturbed Mediterranean Island (Samothraki, Greece)
Round 1
Reviewer 1 Report
Review of the manuscript
Unraveling aquatic quality controls of a nearly undisturbed Mediterranean island (Samothraki, Greece)
This manuscript presents an overview of the status of the aquatic ecosystems of Samothraki island in Greece, a unique environment that has been proposed to be a Biosphere Reserve. Samothraki is also an emerging site of the LTER network in Greece. The authors present the geomorphology, hydrogeology and aquatic quality of the streams and attempts to synthesize the existing knowledge. The work is of interest to the audience of STOTEN. The data presented and analysis represent a preliminary assessment of the observatory and establish initial hypothesis that should be tested as part of the long-term ecosystem research. I recommend publication after the authors addressing the following four major comments:
Content of the manuscript – The manuscript is very long (34 pages) and has 13 tables and figures and it is written like a book chapter rather than emphasizing the research results and the innovative aspects of the research. I recommend that the manuscript be shortened, repetition to be eliminated and several tables and figures to be moved to supplementary information. A few examples Figs 1 and 3, the photographs do not add information to the manuscript and can be removed. Figure 5 is also not necessary; the results can be seen in Table 7. Also, I do not see the need for the comparison of Samothraki’s cold spring average chemistry to the average of 73 Greek bottled water chemistry (table 4) or the box plots of TDI (Figure 4) comparing with bottled spring water of other countries. Finally, I suggest that Figure 6 is not necessary to be shown, the discussion is sufficient. I recommend that the authors shorten the text and remove unnecessary repetition. There is a lot of repetition between site description, results and discussion. If reduced it will sharpen the manuscript and the main messages will not be lost. Weathering rates – The section around line 600 about weathering rates is confusing. Line 604 and 605) state “the long-term capacity of the river to transport bedload (ie erosion) exceeds the long-term capacity of bed load (ie weathering)”. Later “weathering is also intense”. Neither statements make sense. Erosion is different from chemical weathering which can be quantified with the data they have and establish the export rates of Ca and Mg. At the same time in line 596, the manuscript states “weathering resistant bedrock” and then in line 806 (Conclusions), “weathering rates are negligible”. I cannot see an analysis on chemical weathering rates presented in the manuscript and that would be of interest. It would require continuous flow measurements and measurements of Ca and Mg on monthly basis and then normalize them to the watershed area. Ca and Mg measurements presented in Table 3a ha a high variability ranging from Ca from a few mg/L to 768 mg/L and for Mg from less than 1 mg/L to 76 mg/L. These data are not sufficient to discuss weathering rates from the sub-basins. The reason we might have or not weathering is related to the acidity of the rainfall as well as the existence of vegetation and the organic acids they produce. Flow from fog condensation – The authors claim that the summer low flows of the springs and streams are due to fog condensation at higher elevation and that flow at night was higher than the day. The claim was justified based on the flow measurements of the summer of 2019 and the observations of the local shepherds. No data were presented or calculations made to elaborate on the possibility that fog condensation is the cause of this flow diurnal variation. I suggest that the authors present the diurnal signal and quantify the amplitude of the change of flow for the region. Then estimates can be made using atmospheric science to estimate the potential amount of condensation for typical summer conditions to establish if the numbers are consistent and justify in this way the process that accounts for the diurnal flow variation. Ophiolitic rocks – It appears that a significant percentage of many sub-basins are predominantly covered by ophiolitic bedrock. This type of environment in Greece and many other places of the world has a distinct chemical signature of chromium, nickel and manganese. In fact, in some areas the dissolved chromium concentration in the streams and groundwaters exceeds the standards. It would be interesting if the authors have such data to report them in the manuscript. Flow measurements – it is not clear how were the flow measurements made, in what frequency, distribution, duration of data etc.
Overall, I believe that the manuscript has significant information justifying publication pending the revisions of the comments above.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
The submitted manuscript is presenting a nice geochemical study on the origin of water composition and factors influencing its quality across the Samothraki island in Greece. The approach is generally OK. However I have found some deficiencies in presented data, not statistically verified (eg. no ANOVA between groups of water ecosystems compared). The use of Person’s correlation coefficients with no information on the dataset distribution seems not methodologically correct. In case of a number of factors analysed (or even groups of factors: geochemical, geological, morphological etc.) a bit of chaos appeared in the sections of Results and Discussion, what made the text difficult to follow. Some parts of the text need to be moved to another place, and some re-thinking. I had the impression that the work consists of fragments that do not always match each other. This can be seen in the table numbering and data analysis. The use of multivariate analysis such as PCA or RDA would be welcome. Some parts of the text are redundant ( eg. related to macrozoobenthos), which are not analysed although mentioned among methods or so basic and commonly known (eg. DO solubility related to water temperature).
Detail comments:
Abstract should be rewritten in such a way to expose the core conclusions from obtained data.
Introduction: No water quality mentioned, quite shallow description, not related to the subject. Chemical composition (hydrochemical water typology) review or Mediterranean zone would be welcome.l.19 Flashy – small f.
2.1. Study area: Cultural aspects need to be shortened significantly (eg. 99-102 + 110-112 – what is common with the aim of the paper?); please give place to hydrological and climatological issues, water circulation processes etc.
l.130 It should be problably figure 2.
Figure numbering and their location should be corrected and follow the text.
Fig 2 is not readable, please make it clearer.
l.138 master.
l.139 please be precise: how many field surveys have been carried out on Samothraki Island? What does it mean they were preformed mainly in May 2014? What was the reason that the survey performed in May 2014 was so particular?
l.144 please list the studied chemical elements in water: major ions and nutrients.
l.145- what is the role of macrozoobenthos in this study? It is not mentioned in the further sections...
l.153 please explain S/W.
l.157 please reconsider company name (did you mean: Global Water Instrumentation?, Hanna Instruments?), add city and country.
l.152 and other: please correct subscripts in the entire text.
l.161 -162 remove comma after “hardness” and use it before “and”.
l.183-185 What was the reason to install meteorological station in September 2018 if the field survey took place in 2013-14?
l.204-206 Please provide a source of catchment characteristics and applied methods. ArcGIS software is rather not a method of their gathering.
l.216 How many samples were collected? How often the water samples were taken. Any seasonal changes were considered and why?
l.220-227 What is the reason to compare spring water in bottles in Europe for the presented text?
l.238 and other: cluster
Results
245 – 355 3.1. move this section to the study area (2.1) and create there a core text!
398- 404 Fig 4 requires proper legend: what does the box plot mean? What are brand numbers mentioned in the figure subtitle? And at last: where is the the Samotraki data (also statistical justification of this comparison is lacking)?
403- Poland
413 -418 – “On the average, physicochemical parameters were lower in springs, compared to streams...” – were these differences statistically significant? Please complete it with statistical tests.
420- Table 5a 5b 4 – please provide n- number of samples, and a relevant statistical test
449 -458 It is not understandable that the description of Table 3b is placed after table 6. Please move the paragraph to a right place.
Please correct table numbers. The use of multiple numbers is hard to follow in the text. Please use consecutive numbers and use them properly in the text.
Some factors are not analysed in this sector as the residence time of surface and subsurface flow (but discussed!). Hydrological aspects are underestimated, also in the Discussion section.
Discussion: Although this section is well written, some part of the discussion (eg. 685-687) are however astonishing as this one: “ The relationship between grain size composition of stream reaches and WT is triggered by morphological factors; in lowland riverbeds (with higher WTs) low grain size material predominates. Do really authors correlate grain size of the river material with temperature (on the Samotraki island >O oC)? How?!
Some parts of the text related to widely known relationships (DO solubility and water temp.) should be omitted, or at least significantly shortened.
Fig 6 can be neglected at the present as it is presenting widely known relationship Na and CL ions. No significant input or new knowledge is provided.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The manuscript has been substantially corrected. I have got no further remarks. At the present form, it seems a good contribution to Water journal.
