Contemporary Sedimentation in Lake Onego: Geochemical Features of Water, Suspended Matter, and Accumulation Rate

Round 1

Reviewer 1 Report

The aim of this study was to investigate the contemporary sedimentation process in Lake Onego. The tasks included the study of the sedimentation environment, quantitative and qualitative composition of the suspended load being deposited into the sediment using sediment traps (manufactured by authors.

The text only need some minor retifications namely:

In the phase: ....results of the above methods of setting up, spotting, and removing the traps can beregarded as satisfactory: to wit, in 2019, after a year of exposure, 17 of the 20 traps wereretrieved during suitable weather conditions and in three cases the search for the traps had to be
postponed because of high wind and waves. In 2020, traps were lifted at 12 and in 2021 – at 19stations" refer to Table 2.

....The material composition of sediments from the STs was studied by the following methods. How the separation of the various aliquotas was carried out?
...dominant large particles are quartz, alibite, and aggregates of illite...Error Albite.

The discussion was further enriched if there was a comparison with geochemical data of suspended material from other lakes in the region or similar.

Author Response

Dear reviewer, thank you for your careful reading of our work. Your comments have been taken into account in the new edition of the manuscript.

We have supplemented the text with a reference to Table 2 in the phase: «....results of the above methods of setting up, spotting, and removing the traps can be regarded as satisfactory: to wit, in 2019, after a year of exposure, 17 of the 20 traps were retrieved during suitable weather conditions and in three cases the search for the traps had to be postponed because of high wind and waves. In 2020, traps were lifted at 12 and in 2021 – at 19 stations»

Manipulations with the substance from the traps were clarified in the text. «Bottles with water and sediment were taken to the laboratory. Then, their content was transferred to a graduated cylinder, the sediment was stirred up and left to settle for 24 h, after which the sediment column height was measured (with correction to the trap diameter) and liquid was siphoned out, then the sediments was dried for analyses »

We have corrected a typo in the name of the mineral «Albite»

Unfortunately, there is no data on the geochemical composition of the suspended matter of other lakes in the region. Therefore, the article provides comparisons of substances from traps with river suspension and with bottom sediments of Lake Onego and other regions.

Reviewer 2 Report

The article “Contemporary sedimentation in Lake Onegо: geochemical features of water,

suspended matter and accumulation rate” is devoted to the study of the contemporary continental

sedimentogenesis in a large lake of northern humid zone. The stable functioning of lake

ecosystems in a situation of constant transformation of the catchment under climate fluctuation

and anthropogenic presser is important civilization problem. Sedimentation processes are a good

indicator of any changes in the lake.

The study required considerable preparation from the authors. They created a research

program that included: (1) selection and approval of the sedimentation monitoring network in the

local sedimentation basins in the lake, (2) invention design of sedimentation traps and the

method of their installation and lifting (3) unification of method for sample preparation of

sedimentary matter for analysis. The authors are of the opinion about comprehensive

methodological approach to solving the problem. They study the sedimentation environment,

quantitative and qualitative composition of suspended matter, using modern methods of analysis

of geochemistry, mineralogy and micropaleontology. All this allowed scientists to achieve

significant results. The authors demonstrate that the sedimentation process in the Lake Onego is

non-uniform. Variations in the sedimentary matter chemical composition across the lake are due

to natural causes and to unevenly distribute anthropogenic pressure.

A very interesting point in the work is the proof of the hypothesis about the significant

role of intra - reservoir processes in the formation of bottom sediments. The authors have shown

that the transformation of suspended solids occurs in Lake Onego in a complex biogeochemical

way, which leads to the formation of new mineral phases of iron, manganese and silicon. The

contribution of lake processes accounts for more than 50% of the mass of substances entering the

bottom.

Author Response

Dear reviewer, thank you for your careful reading of our work. We have taken your comment into account.

A professional translator checked our text.

Reviewer 3 Report

I appreciate the amount effort that went into the development of this work. Unfortunately, I believe that the manuscript needs to be completed and corrected.

11.  It would be interesting to compare more the results obtained with those of the scientific literature (more articles from outside the circle of authors of this publication should be cited). I believe that the ratio of self-citations (20 articles out of 37 references) to citations of other scientists was not maintained.

22.  There are no specific scientific goals stated. What research hypotheses have the authors assumed?

33. Were there any significant differences in the geochemistry of Lake Onega sediments compared to the sediments of other lakes (of similar genesis and climatic conditions)?

44. What is the practical significance of the research results?

55. The authors often emphasize the role of the anthropogenic factor, but apart from single examples, they do not provide specific sources of the analyzed sediment components. Characteristics of land use are definitely missing here.

Author Response

Dear reviewer, thank you for your careful reading of our work. Your comments have been taken into account in the new edition of the manuscript.

The manuscript was supplemented with articles by other scientists concerning the geochemical composition of suspended matter and the assessment of the sedimentation rate.

The wording of the purpose of the work has been changed.

“The aim of the study was to investigate the contemporary sedimentation process in Lake Onego. The tasks included in the study of the sedimentary environment (geochemistry of water and suspended solid), quantitative and qualitative composition of the suspended load being deposited in the sediment (grain size, geochemistry, mineralogy and diatoms) and estimation of sedimentation rate through in situ surveys with sediment traps. Using the example of Lake Onego, we decided to show that: (1) the accumulation of sedimentary matter in a large lake is a really complex, uneven process controlled by a combination of different factors; (2) a significant proportion of mineral suspended matter entering the bottom of a large lake has an autochthonous genesis”.

Unfortunately, there is no data on the geochemical composition of suspended solids of other lakes in the region. Therefore, in the article we were forced to limit ourselves to a comparison with the river suspension and with the bottom sediments of Lake Onego and other regions.

We have included in the introduction information about the anthropogenic load on Lake Onego and the peculiarities of land use in the catchment area.

The results of the study of sedimentogenesis processes in Lake Onego can be used in predictive models describing the response of the lake ecosystem to climatic and anthropogenic impacts, as well as for detailing the monitoring program.

Reviewer 4 Report

The article is devoted to the study of spatial and temporal variability of the sedimentation process in Onega Lake (Russia) based on the study of the chemical composition of water.

Actuality and scientific significance of the work is obvious - the results and conclusions of this research contribute to the study of regularities and anthropogenic effects on the evolution of ecosystems.

In my opinion, the work is quite interesting and meaningful.

The Introduction shows the main issues raised by this study and provides a good review. Unfortunately, the authors in this manuscript refer mainly to works in Russian, which could potentially significantly reduce the readership of non-Russian readers. My strong recommendation to the authors is to try to add 10-15 international references  to this interesting and important work.

The results of the work are given briefly but comprehensively. The main part of the manuscript is devoted to the Discussion, in which the authors thoroughly and scrupulously discuss the results obtained. The conclusion reflects the main findings of the paper and logically follows from the presented results and their discussion.

I can recommend this paper for publication after correcting several remarks.

1. The text should be modified according to the requirements of the journal

2. If possible, add references to international works.

3. Figure 4 should be changed to color. In black and white the lines are unrecognizable.

Author Response

Dear reviewer, thank you for your careful reading of our work. Your comments have been taken into account in the new edition of the manuscript.

The manuscript was supplemented with articles by other scientists concerning the geochemical composition of suspended matter and the assessment of the sedimentation rate.

Figure 4 has been modified according to your recommendations.

Round 2

Reviewer 2 Report

Author has made the required changes,

So paper should be accepted in current form.

Good Luck

Author Response

Dear reviewer,

thank you so much for your work.

Have a nice day.

Reviewer 3 Report

Dear Authors,

Thank you for considering my comments and clarifying my doubts. Please pay attention to minor proofreading errors, e.g. the chemical formula on page 24.

Author Response

Dear Reviewer,

we would like to thank you for your attention to our work.

All references provided relate to this study. References to previous studies of bottom sediments of Lake Onego and suspended matter of river waters of the region were added to the manuscript on the recommendation of one of the Reviewers. We agreed with the reviewer's opinion that this information will complement the content of our work and will be of interest to specialists. These works are related to the study of suspended matter entering the bottom. Bottom sediments concentrate scattered sedimentary matter, and the material of the surface layer of bottom sediments is usually considered in the scientific literature as a freshly deposited sedimentary matter that underwent changes in early diagenesis. Rivers supply suspended matter to a lake, but in the process of deposition in the water column, this substance undergoes changes. Our method of collecting sedimentary matter in traps allows us to obtain for research a substance that has already changed in the water column, but has not yet entered into diagenetic transformations. In our manuscript, the composition of a substance from the traps is compared with bottom sediments and with river suspensions.

Information about the anthropogenic load on the lake was added, as the article discusses the genesis of sedimentary matter

Also, in the introduction, information was added about existing methods for estimating the sedimentation rate with a brief summary of their disadvantages and advantages, so that the reader would appreciate our choice, namely, the method of estimating the rate from in situ observations.

We have made corrections to the methods section. We have checked and corrected an error in the sedimentation rate calculation formula. We have corrected a formula on page 24.