Thank you for the constructive review. We will attempt to improve the data analysis and its interpretation. The detailed modifications are described below.

Introduction

Part of the introduction discusses carbon sequestration in freshwater wetlands, whereas your study focuses on the shallow littoral areas of Finnish lakes. Did you take sediment samples from lacustrine wetlands?

Reply: For this manuscript, we analysed samples only from sediment cores retrieved from the shallow littoral areas.

Materials and Methods

90-92. Please specify whether the sampled lacustrine zones (i.e. the shallow vegetated littoral zone, called teal carbon environments) represent large or weak surfaces on the scale of the lake.

Reply: We can calculate an estimate of how much these shallow vegetated littoral areas represent of each lake, but it will be an approximation since they vary annually due to natural variability in the vegetation growth and anthropogenic interference.

96. What is the trophic state of the Olujarvi lake? Could you explain in more detail why you chose these three lakes?

Reply: Oulujärvi is dysoligotrophic, and we will include this information in the text. We chose these lakes because we had evidence of the existence of large shallow vegetation patches and because they have been sampled before for other projects. So, there is data regarding their overall water and sediment quality. However, we focused on areas that had less sampling coverage based on existing data and covering different regions (sub-basins) of each lake.

110. If surficial deposits influence OC accumulation, then add this information to Table 1 by adding a row to better distinguish the variability between the lakes.

Reply: The surficial deposits around each lake will influence the type of sediment found in each lake, which we found that is a key factor influencing the OC accumulation. We will add this information in Table 1.

123-126. You can add in parenthesis the range of the standing water depth for each shoreline zone to better distinguish your three sampling areas. From 0.15 to 0.60 m in the landside zones, from 0.29 to 1.13 m in the transitional zones and from 0.37 to 1.23 m in the waterside zones (from Table S2).

Reply: We will add this information as suggested.

179. There is an inconsistency between the text (L174-178) and equation 4a. TOC inventory for a given sample [g] was calculated multiplying the TOC content [%] by the DBD [g cm-3] and the sample volume [cm3]. However, in the equation 4a, TOC inventory is: (TOC x DBD x depth) x 1000.

Reply: We will correct the formula. The correct parameter is sample volume, and not only sample depth.

Results

Figure 3. Could you add the Tukey test results in the graphs using letters (and the number of samples per group)? Same comment for the figure 5.

In the figure 3, can you add below two other boxplots for TOC distribution grouped by lakes and shoreline zones?

Reply: We will make the suggested modifications.

247. Could you add in parenthesis the shoreline zone and grain size class for the minimum and maximum values of SOC stocks?

Reply: We will add the information as suggested.

249-254. Could you provide the results of the ANOVA tests for the comparison between lakes and shoreline zones?

Are you able to provide a more accurate statistical analysis in order to rank the contribution of different environmental predictors (lakes, shoreline zones, plant species and grain size class) to SOC stocks using a multiple factor analysis of variance per example?

The results of the generalized linear model can be added to the manuscript (table S6) to strengthen your findings.

Reply: We will add the ANOVA results, including from the multiple factor analysis, in the Supplementary Material. We can move the results of the GLM to the main text.

Discussion

285-287. The strong relationship between TOC content and grain size is the first clear finding in your study and this deserves to be included as a figure. I suggest that the authors insert Figure S23 into the manuscript, probably near the Figure 3. Can you study this relationship in more detail using a non-linear equation?

Reply: We will include the plots of Figure S23 in Figure 3, making it a 6-panel figure, and increase the discussion about this relationship using a gamma regression.

297-298. This statement is not very detailed and deserves further discussion.

Reply: We can improve the explanation of the effect of water regulation on sediment input to Oulujärvi.

300. I encourage the authors to complete this sentence in order to provide greater precision. “As pointed out by Tangen and Bansal (2020) in inland freshwater wetlands, SOC stocks are highly variable …”

Reply: We will modify the text as suggested.

302. Please replace “ranging from zero to more 40 kg m-2 ” by “ranging from 0 to 40.8 kg m-2 ” for more precision.

Reply: We will modify the text as suggested.

303. To tie in with the previous paragraph, please indicate that fine-grained sediments are rich in organic matter such as: “Several environmental parameters could influence the entrapment of organic-rich fine-grained sediments, such as…”.

Reply: We will modify the text as suggested.

309-311. The strength of this statement is not fully supported by your data. From a statistical point of view, we can observe significantly higher SOC stock values without Phragmites compared to the Phragmite group in the Figure 5-e. We can observe this statistical result in the Table S5 and in lines 249-250-251. The type of vegetation is probably not a major factor in SOC stocks compared to sediment size, but you cannot ignore it.

Reply: We understand the reviewer comment. We did not put too much emphasis on the relationship between the vegetation type and SOC stocks because the 2nd and 3rd highest SOC stocks were observed in sites with Phragmites even though the median is much lower. But we will modify the text to reflect that the vegetation might have an impact of SOC accumulation.

313-317. Please provide means and standard deviations of SOC stocks for average fetch length < 500 m and for average fetch length > 500 m to strengthen your statement. Please specify whether the trend is similar for SOC stocks (0-20 cm).

Reply: We will modify the text as suggested.

319-320. Please add here that vegetation density plays a significant role in SOC stocks in exposed conditions (c.f., figure S25).

Reply: We will modify the text as suggested.

339- 345. Please clearly conclude concerning the effects of bathymetry and shoreline’s slope on SOC stocks. Have you tested the influence of bathymetry, shoreline’s slope and stem density on SOC stocks in conditions where the shoreline is protected (average fetch length < 500 m)? 

For each lake, you present the ecological status, the main land use type and the main anthropogenic pressures (Table 1). Do these factors influence the grain size distribution and the lake SOC stock?

Reply: We will add a clear conclusion about the effects of bathymetry and shoreline’s slope on SOC stocks. We did not test their influence in only protected sites because the sampled “n” would be too small (only 3 sites, with their zones) to make any inference with confidence.

Regarding the ecological status, the main land use type and the main anthropogenic pressures, they probably don’t play a significant role in controlling grain size distribution in these teal carbon environments. If they did, we would have seen significant differences between the lakes but not between the sites within each lake, what did not happen (Figure 4).

375-410. The authors have correctly compared their results with SOC values from freshwater marshes, coastal lagoons, and blue carbon environments in marine areas. However, the authors should also compare their results with similar studies in lakes worldwide. Could the difference in magnitude be related to a difference in sampling strategy? Please discuss the inclusion of shallow vegetated coastal areas in the organic carbon stocks of lakes. Please discuss the importance of sampling shallow coastal areas of lakes in order to obtain a realistic estimate of organic carbon stocks, unlike certain studies that have conducted sediment core sampling in the deepest part of the lake.

Reply: Because the focus of this research was on vegetated areas, we preferred not to compare with data from deeper areas of lakes, as it would lead to a whole new discussion about the controlling factors affecting both areas. But we will emphasize the importance of shallow areas to obtain realistic lacustrine OC stock estimates.