Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of Korea
Round 1
Reviewer 1 Report
This was a very interesting and well-written manuscript to review. I have only very minor comments in the attached edited version. Results were clearly presented and the methods were interesting and indicative of the application of AI to data analysis. I recommend accept!
Comments for author File: Comments.pdf
Author Response
- For panels d, e, and f the superscripts are missing - is that intentional and implies no sig, differences? Based on the text in lines 355 and 356 I thought there would be sig. differences in lipids (4d)? Please clarify - i.e if same superscripts indicate non-significant differences then include in panels with no difference or state not included in for all differences are non-significant (same in Fig. 5)
Response: Thanks. We have added superscripts in Figure 4 (d-f) and Figure 5 (e). We have also revised the figure captions and text accordingly (see Lines 359-360).
- Macromolecular - here it looks like a space inserted Macro molecular?
Response: Thanks. According to the reviewer’s comment, we have carefully checked the section. There is no space, rather the word continued to the next line which looks like a space.
- sp. is usually not italicized.
Response: Thanks for checking typo. We have corrected the typo accordingly. (see Line 833).
Reviewer 2 Report
This is a manuscript reporting the results of a sound and sophisticated study focused on relationships among a number of biochemical and physiological features of phytoplankton communities with their taxonomic class composition and estimated cell sizes.
The text is written in relatively very good English, which is grammatically sound and easy to understand. I have no serious reservations about the study. I am sure that there is indeed a lot of work behind this research and the data obtained and their interpretation can be a valuable addition to the scientific literature on the biochemistry and physiology of estuarine phytoplankton. I was disappointed by only one, but in my opinion significant, limitation of the study, which at the same time could have been easily supplemented. Namely, the authors only use the indirectly derived abundances of individual phytoplankton classes obtained from pigment analysis as the basic comparative dataset indicating the abundances of each class. In doing so, this dataset is then a key means for them to interpret the observed dynamics in the measured biochemical and environmental parameters. It is possible, indeed likely, that the observed variability would also have correlations at the level of changes in the abundances of individual dominant genera or species in the phytoplankton community. And it would not be difficult to obtain such data. It would be enough to take a microscope and observe, identify and count the individual dominant species in the community. The marine phytoplankton is, for the most part, composed of notoriously well-identifiable organisms, and identifying them in the microscope is well and reliably possible. It is indeed a pity that the authors did not carry out this part of the research; their study could have been much more valuable, interesting and potentially much more cited in the future.
Nevertheless, I support in principle the acceptance of the manuscript for publication. I have only minor comments and criticisms on the individual sections of the text, which are listed below:
l. 62-63
"species composition and/or cell-size diversity are important functional traits for the determination of biochemical composition, as they vary among the major phytoplankton taxa"
Well, just. That's why it's such a shame that the study did not venture beyond the class level and did not go to the species level.
l. 65-68
"the characterization of the biochemical composition of seston may provide clues to identify the effects of changes in environmental conditions across the land–sea interface and further evaluate its quality and bioavailability for higher trophic organisms"
This is true, but again I have to state here that finding out the actual species or genus composition of the community and its temporal dynamics would be a much simpler and more direct way to identify of "the effects of changes in environmental conditions"... After all, the biochemical composition is only more or less directly derived from the taxonomic one, isn't it?
l. 70-71
"the unique feature of a low particle concentration relative to the huge freshwater discharge from the Seomjin River"
I don't understand this. A strong freshwater inflow should rather lead to higher concentrations of nutrients and particles carried by the river flow, no?
l. 76-77
The input of nutrient-rich freshwater is tightly coupled to seasonal variability in phytoplankton community composition and primary production
If the river is delivering large amounts of nutrients to the estuarine system, then this should lead to high photosynthetic biomass production and therefore seston.
p. 92
longitudinal distribution
This is an obscure phrase. "Longitudinal" would imply that it is geographic variation along a longitude gradient, but it certainly is not. It may be more like "spatial variation".
l. 89, l. 94
"community composition of phytoplankton" ... "taxonomic (i.e., size) composition of phytoplankton"
By "community composition" one cannot imagine anything alse than data on distribution of individual taxa composing the community. However, then the authors seemingly draw an equivalence between "taxonomic" and "size" composition of communities. That would, of course, be wrong! Taxonomic variation has little in common with differential cell and body size of individuals.
l. 117-118
"Three stations (S1–S3) were located in the oligohaline shallow estuarine channel..."
Can you supplement the actual salinity levels of individual stations? This would make the assessment of the gradient much more easier.
l. 275-276
"22 variables x 36 samples in this study"
So, does this also include the abundances of individual photosynthetic pigments that were used as a proxy for estimating the biomass of individual algal classes? This should be explicitly stated in the text at this point.
Author Response
- This is a manuscript reporting the results of a sound and sophisticated study focused on relationships among a number of biochemical and physiological features of phytoplankton communities with their taxonomic class composition and estimated cell sizes.
The text is written in relatively very good English, which is grammatically sound and easy to understand. I have no serious reservations about the study. I am sure that there is indeed a lot of work behind this research and the data obtained and their interpretation can be a valuable addition to the scientific literature on the biochemistry and physiology of estuarine phytoplankton. I was disappointed by only one, but in my opinion significant, limitation of the study, which at the same time could have been easily supplemented. Namely, the authors only use the indirectly derived abundances of individual phytoplankton classes obtained from pigment analysis as the basic comparative dataset indicating the abundances of each class. In doing so, this dataset is then a key means for them to interpret the observed dynamics in the measured biochemical and environmental parameters. It is possible, indeed likely, that the observed variability would also have correlations at the level of changes in the abundances of individual dominant genera or species in the phytoplankton community. And it would not be difficult to obtain such data. It would be enough to take a microscope and observe, identify and count the individual dominant species in the community. The marine phytoplankton is, for the most part, composed of notoriously well-identifiable organisms, and identifying them in the microscope is well and reliably possible. It is indeed a pity that the authors did not carry out this part of the research; their study could have been much more valuable, interesting and potentially much more cited in the future.
Nevertheless, I support in principle the acceptance of the manuscript for publication. I have only minor comments and criticisms on the individual sections of the text, which are listed below:
Response: Thanks for the positive feedback on our manuscript. We totally agree with the reviewer that the inclusion of phytoplankton community composition based on microscopic observation would have increased the quality and scope of our paper. However, it was not possible to include in our current paper. We will certainly consider the reviewer’s suggestion in our future studies.
- l. 62-63
"species composition and/or cell-size diversity are important functional traits for the determination of biochemical composition, as they vary among the major phytoplankton taxa"
Well, just. That's why it's such a shame that the study did not venture beyond the class level and did not go to the species level.
Response: Thanks for this critical comment. As supported by our results, taxonomic composition and thereby cell-size variation may determine sestonic biochemical composition in association with varying environmental conditions. In order to understand the effects of different species on changes in sestonic biochemical composition it may be needed further laboratory-manipulated experiments because we could not observe a predominance of one single species in the field. Accordingly, we could not extract information of the effects of the species level in our study. We expect that this subject may provide a further research hypothesis about the dynamics of seston in coastal systems.
- l. 65-68
"the characterization of the biochemical composition of seston may provide clues to identify the effects of changes in environmental conditions across the land–sea interface and further evaluate its quality and bioavailability for higher trophic organisms"
This is true, but again I have to state here that finding out the actual species or genus composition of the community and its temporal dynamics would be a much simpler and more direct way to identify of "the effects of changes in environmental conditions"... After all, the biochemical composition is only more or less directly derived from the taxonomic one, isn't it?
Response: Agree and thans for really useful comment. Although data at species level provide fine scale determination of interspecific variation, there is an evidence which report that spices belonging to the same group (e.g., Diatoms) demonstrate considerable similarities in their biochemical properties under a set of environmental conditions. Therefore, we are convinced that pigment based classification of seston could sufficiently explain our study objectives. We will certainly consider including the suggested approach to enhance and widen up the scope of our future studies.
- l. 70-71
"the unique feature of a low particle concentration relative to the huge freshwater discharge from the Seomjin River"
I don't understand this. A strong freshwater inflow should rather lead to higher concentrations of nutrients and particles carried by the river flow, no?
Response: Agree but our system differs from other river system cases in the world. This is the reason why we need to study seston dynamics in the Gwangyang Bay system to characterize low-turbidity estuarine coastal embayment. Indeed, in most estuarine systems, river water delivers a lot of particulate loads, such as the case in the Gironde Estuary in France, the Peal River Estuary in China and the Chesapeake Bay in USA. However, our study system, the Seomjin River Estuary and Gwangyang Bay, possesses unique feature of low suspended particulate matter load inspite of large river discharge (Bibi et al., 2020; doi.org/10.3389/fmars.2020.580260: Kwon et al., 2002; doi: 10.5657/kfas.2002.35.1.086). It is particularly the loss of intertidal flats for construction of large-scaled port and industry facilities as well as Gwangyang Bay basin is covered by 71% of forests and 22% of agricultural lands and the bay is bounded by steep mountain and hills to the north and Yeosu peninsula and Namhae Island to the southwest and southeast, respectively and shape of the bay is elongated and is very shallow (except the deep bay channel stations) so very weak sediment re-suspension occurs since wind pressure is blocked because of mountain range. bay has a semidiurnal tidal cycle, with a maximum tidal range of 3.40 m and 1.10 m during the spring and neap tides and particles load and gradient is associated with the tidal cycles and since tidal currents show asymmetry and high river discharge so any allochthnous particles load is diluted and transported to deep bay because of short residence time of water (Lee et al., 2018: doi: 10.1007/s12237-018-0404-9). Though the concentrations of suspended particulate matter (SPM) in water column varies with season and along the salinity gradient but phytoplankton production is major contributor to SPM in Gwngyang Bay.
- l. 76-77
The input of nutrient-rich freshwater is tightly coupled to seasonal variability in phytoplankton community composition and primary production
If the river is delivering large amounts of nutrients to the estuarine system, then this should lead to high photosynthetic biomass production and therefore seston.
Response: Thanks. The sentence has been rephrased as follows:
“The seasonal variability in phytoplankton community composition and primary production is tightly coupled to high input of nutrients delivered by freshwater [29, 30, 24].” (see Lines 79-81)
- p. 92
longitudinal distribution
This is an obscure phrase. "Longitudinal" would imply that it is geographic variation along a longitude gradient, but it certainly is not. It may be more like "spatial variation".
Response: Thanks. We have revised as follows:
“The objectives of the present study were to determine the seasonal and spatial variations in the biochemical composition of seston along the estuarine–coastal continuum and identify the major factors that control its spatial distribution.” (see Lines 93-96)
- l. 89, l. 94
"community composition of phytoplankton" ... "taxonomic (i.e., size) composition of phytoplankton"
By "community composition" one cannot imagine anything alse than data on distribution of individual taxa composing the community. However, then the authors seemingly draw an equivalence between "taxonomic" and "size" composition of communities. That would, of course, be wrong! Taxonomic variation has little in common with differential cell and body size of individuals.
Response: Agree. However, we have adopted a generalized cell-size distribution among phytoplankton classes:
"Diatoms and dinoflagellates were grouped as micro-size; cryptophytes, pelagophytes, and prymnesiophytes as nano-size; chlorophytes, cyanobacteria and prasinophytes as pico-size" as described in section 2.3.2. (see Lines 192-196).
- l. 117-118
"Three stations (S1–S3) were located in the oligohaline shallow estuarine channel..."
Can you supplement the actual salinity levels of individual stations? This would make the assessment of the gradient much easier.
Response: Thanks. According to the reviewer’ suggestion, we have made changes as follows:
“Three stations (S1–S3) were located in the oligohaline shallow estuarine channel (salinity 0 to 8), two stations (S4 and S5) were in the mesohaline, or mixing zone (salinity 15-30), and the four remaining stations (S6–S9) were located in the polyhaline deep-bay channel (salinity >30).” (see Lines 120-123).
- l. 275-276
"22 variables x 36 samples in this study"
So, does this also include the abundances of individual photosynthetic pigments that were used as a proxy for estimating the biomass of individual algal classes? This should be explicitly stated in the text at this point.
Response: We described this in data analysis section.
“The input data, i.e., the biogeochemical parameters in this study, were normalized on a scale of 0-1 to reduce the variation and ensure that all variables have equal importance.” (see Lines 280-282)
Further we mentioned this in results section.
“Based on 36 datasets (9 stations × 4 seasons) of 22 physical and biogeochemical variables (Tables S1–S3), we trained the SOM and condensed it onto a 5 ´ 6 rectangular-grid map (Figure 2a and Supplementary Figure 1).” (see Lines 321-323)
Physical and biogeochemical parameters were used in the SOM training and phytoplankton community composition was interpreted based on cluster assemblage since each cluster was robust representation of specific environmental conditions.
Reviewer 3 Report
The paper: “Biochemical composition of seston reflecting the physiological status and community composition of phytoplankton in a temperate coastal embayment of Korea” presents the seasonal and spatial variations in the biochemical composition of seston along the estuarine–coastal continuum and identify the major factors that control its longitudinal distribution.
Some minor comments:
The authors should better explain how this study contributes to the scientific literature in the field.
Please further explain why this Study site is representative and how it was selected for the locations of the sampling stations / data collection.
In the discussion section, results should be better compared with other results obtained in other studies.
Quality of figure 3 should be improved.
Author Response
- The authors should better explain how this study contributes to the scientific literature in the field.
Response: Thanks for valuable comments. According to the reviewer’s suggestion, we have added some relevant explanation in the ‘Introduction’ section. (see Lines 43-49, 69-72, 81-88).
“Therefore, despite the large variety of processes (e.g., tidal resuspension, riverine loads, and turbidity maximum zone) that control the quantity and composition of seston in estuarine and coastal systems [9, 10], variations in the biochemical composition of seston can yield valuable information about the biogeochemical factors that control the spatiotemporal distribution, sources, transport, and degradation of POM, as well as phytoplankton growth, total biomass, production, and community composition characteristics [11, 12].”
“Therefore, the characterization of the biochemical composition of seston may provide clues to identify the effects of changes in environmental conditions across the land–sea interface and further evaluate its quality and bioavailability for higher trophic organisms.”
“Furthermore, recent evidence demonstrates that in situ primary production, principally phytoplankton, serves as the prevalent contributor of SPM and POM in this embayment system, thus providing a major trophic base to the benthic and pelagic food web [26, 5, 31]. For this reason, Gwangyang Bay provides an excellent test bed system to examine the spatiotemporal variations in the biochemical composition of seston, which may provide insight into the major biogeochemical processes linked to the high biological activity (i.e., phytoplankton biomass and primary production) observed in the phytoplankton-based coastal ecosystem.”
We further described in the last paragraph of the ‘Conclusion’ as follows:
“Our findings will be potentially useful to understand the metabolic variability of phytoplankton in response to environmental stressors and the allocation of phytoplanktonic carbon to different biochemical compounds of the seston pools in low-turbidity estuarine embayment systems.” (see Lines 591-594)
- Please further explain why this Study site is representative and how it was selected for the locations of the sampling stations / data collection.
Response: Thanks for the comment. We have described in details about the study-site characteristics and sampling stations (see Lines 106-123)
- In the discussion section, results should be better compared with other results obtained in other studies.
Response: Agree and thanks. As can be seen in Figure 4, annual ranges of concentrations of individual biochemical compounds are relatively large so that we cannot make direct comparisons with concentrations in other systems. Instead, in the ‘Discussion’ section, we have discussed some results by comparisons of data between the present and other studies.
- Quality of figure 3 should be improved.
Response: Thanks. We have regenerated ‘Figure 3’ accordingly.
Reviewer 4 Report
The manuscript presents a study of phytoplankton composition and phytoplankton from biochemical components in a Korean bay. The paper is interesting, although I consider that it might be more appropriate for the Journal of Marine Systems and Engineering. In any case, the editor should decide this issue.
The abstract is well presented, but it does need to define what POC is that you have not described (lines 20 and 22).
The keywords are all two or three words. It is desirable not to repeat words from the title in the keywords. It is intended that the search engines have the possibility of having more words to relate the work. Repeating the title does not contribute anything.
In the introduction, paragraph 36-42 is written in such a way that the explanation lacks ecological sense. It should be explained that production only comes from primary producers and decomposers; the phytodetritus does not produce anything, it is the phytoplankton and the microbial loop that provide the energy to the food webs.
The explanation in paragraph 49-69 lacks any reference to the microbial loop, which in environments of this type could be as important as 50% of the food web production via the decomposition of particulate matter from rivers. The explanation offered is simple and does not reflect the reality of a world that is much more complex than what is presented and therefore needs to be improved.
Line 83 should clarify what is meant by the high biological activity of phytoplankton. A reader might think it refers to the movement of living things, for example.
In the methodology, the presentation of the study site is correct.
The analytical methodology is also well described. I consider some points that need to be clarified. The methodology for SPM needs an accredited reference, as it is an unusual procedure (105 ºC temperature is generally used). The procedure described in section 2.3.3 does not have any bibliographic reference, so it is assumed that it is a methodology specific to the research group. If this were the case, this could also be indicated.
The presentation of results could improve Figure 2, placing instead of the numbers in the dendrogram, the same codes of Figure 2 (A1, A2, A3, etc.); it would improve the presentation and does not require an effort to look for a number elsewhere.
Figure 3 is very interesting. Within the figure, some results are in black, green and red font, but it is not indicated what it means.
Section 3.3 surprisingly presents community composition results, because previously, in the methodology it has not been described that samples are taken for this nor the procedure used for identification and counting. This should be explained in section 2 in a section, like the other methods. In Figure 7, the relationship to size groups expressed in biomass is also presented, and there does not appear to be any methodology described for calculating phytoplankton biomass. It is possible that the authors are referring to the photosynthetic pigment equivalent of the size class; but this is not explained anywhere.
In the discussion (paragraph 437-440), the authors proclaim this to be original work in their study area; but they should precisely discuss their results with other work identical to theirs as cited here:
Lewitus, A. J., White, D. L., Tymowski, R. G., Geesey, M. E., Hymel, S. N., & Noble, P. A. (2005). Adapting the CHEMTAX method for assessing phytoplankton taxonomic composition in southeastern US estuaries. Estuaries, 28(1), 160-172.
Irwin, A. J., Finkel, Z. V., Schofield, O. M., & Falkowski, P. G. (2006). Scaling-up from nutrient physiology to the size-structure of phytoplankton communities. Journal of plankton research, 28(5), 459-471.
Then, to point out the coincidences or discrepancies of the results obtained in Korea with other work done previously.
The discussion is well presented with the content. However, it suffers from the defect of not considering the microbial loop in the work. Although the authors present that it is a low turbidity zone (no water transparency measurements), the presence of SPM in numbers of 20 mg/L with chlorophyll values of 3 µg/L indicates that the presence of non-photosynthetic material in suspension is important. The C:N ratio does not conform to Redfield values for phytoplankton, so presumably the non-photosynthetic population must be significant and does not appear to have been assessed. Somehow this shortcoming of the paper should be integrated into the discussion.
Otherwise, a very interesting paper.
The bibliography is well presented, in keeping with the style of the journal.
Supplementary materials are very useful, but are not cited in the main text of the manuscript. It is necessary to refer the materials and tables in the text where convenient.
Author Response
- The manuscript presents a study of phytoplankton composition and phytoplankton from biochemical components in a Korean bay. The paper is interesting, although I consider that it might be more appropriate for the Journal of Marine Systems and Engineering. In any case, the editor should decide this issue.
Response: Thanks for the valuable comments and suggestions made by the reviewer.
- The abstract is well presented, but it does need to define what POC is that you have not described (lines 20 and 22).
Response: Thanks for the critical comment. According to the reviewer’s suggestion, we have revised as follows:
“The low POC:Chla (<200), molar C:N (~7) ratios, and biopolymeric carbon concentrations coupled with high primary productivity indicated a low detrital contribution to the particulate organic carbon pool.” (see Line 22)
- The keywords are all two or three words. It is desirable not to repeat words from the title in the keywords. It is intended that the search engines have the possibility of having more words to relate the work. Repeating the title does not contribute anything.
Response: Thanks. We have added different key words accordingly. (see Lines 29-30)
- In the introduction, paragraph 36-42 is written in such a way that the explanation lacks ecological sense. It should be explained that production only comes from primary producers and decomposers; the phytodetritus does not produce anything, it is the phytoplankton and the microbial loop that provide the energy to the food webs.
Response: Agree and thanks. According to the reviewer’s comment, we have deleted “phytodetritus” in this description. (see line 40)
- The explanation in paragraph 49-69 lacks any reference to the microbial loop, which in environments of this type could be as important as 50% of the food web production via the decomposition of particulate matter from rivers. The explanation offered is simple and does not reflect the reality of a world that is much more complex than what is presented and therefore needs to be improved.
Response: Agree and thanks for the valuable comment. As suggested by the reviewer, we have tried to add an explanation of the importance of microbial decomposition processes loop to sestonic biochemical composition as follows:
“In addition, microbial decomposition processes may also serve as an important role in determining sestonic composition especially in estuarine embayment [9, 10, 17].” (see lines 66-69)
- Line 83 should clarify what is meant by the high biological activity of phytoplankton. A reader might think it refers to the movement of living things, for example.
Response: As suggested by the reviewer, we have revised this sentence as follows:
“For this reason, Gwangyang Bay provides an excellent test bed system to examine the spatiotemporal variations in the biochemical composition of seston, which may provide insight into the major biogeochemical processes linked to the high biological activity (i.e., phytoplankton biomass and primary production) observed in the phytoplankton-based coastal ecosystem.” (Lines 84-88)
- In the methodology, the presentation of the study site is correct.
Response: Thank you for the reviewer’s positive feedback.
- The analytical methodology is also well described. I consider some points that need to be clarified. The methodology for SPM needs an accredited reference, as it is an unusual procedure (105 ºC temperature is generally used). The procedure described in section 2.3.3 does not have any bibliographic reference, so it is assumed that it is a methodology specific to the research group. If this were the case, this could also be indicated.
Response: Agree and thanks. For measurement of SPM concentration, the filters containing SPM samples are dried in an oven at 105°C over night (Pfannkuche and Schmidt, 2003). Instead of drying overnight, some studies applied drying for 24 h at 60°C (Barillé-Boyer et al., 2003) and, more recently, ‘drying for 24 h at 75°C’ has been recommended (Neukermans et al., 2012). This is a procedure to dry SPM samples. We employed the procedure drying for 72 h at 60°C and cooling to room temperature in a vacuumed desiccator before weighing in order to confirm the dryness of samples. We believed that this procedure (drying for 72 h at 60°C) may enable us to do further analysis (i.e., POM measurement, etc.) accurately with no or limited modification of SPM materials.
- Pfannkuche, J., Schmidt, A., 2003. Determination of suspended particulate matter concentration from turbidity measurements: particle size effects and calibration procedures. Process. 17, 1951–1963.
- Barillé-Boyer, A.-L., Barillé, L., Massé, H., Razet, D., Héral, M., 2003. Correction for particulate organic matter as estimated by loss on ignition in estuarine ecosystems. Coast. Shelf Sci.58, 147–153.
- Drying for 24 h at 75°C: Neukermans, G., Ruddick, K., Loisel, H., Roose, P., 2012. Optimization and quality control of suspended particulate matter concentration measurement using turbidity measurements. Oceanogr. Methods. 10, 1011–1023.
For section 2.3.3. (Primary productivity of phytoplankton), we have added references where needed.
- The presentation of results could improve Figure 2, placing instead of the numbers in the dendrogram, the same codes of Figure 2 (A1, A2, A3, etc.); it would improve the presentation and does not require an effort to look for a number elsewhere.
Response: Thanks for the useful suggestions. Unlike hierarchical clustering technique where clusters are visualized through a hierarchical tree, commonly referred to as a dendrogram and figure codes are used, self-organizing maps, analyze high-dimensional input data (where each record corresponds to an input vector) and focuses on topological structure of cluster sets by summarizing groups of strongly related variables by assigning them to node of a two-dimensional grid and each unit represents number of neurons of output layers. So the numbers in dendrogram are the number of neurons (cells) of the output layer of SOM training and standard way of reporting self-organizing maps. Since in SOM maps, the numbers are noted from top to bottom and from left to right on the map so, for example, in cluster I, we have 5 number of neurons (1,2,6,7, 11) and so on and forth. Therefore, instead of numbers assigning A1, A2, etc. could cause confusion to readers.
- Figure 3 is very interesting. Within the figure, some results are in black, green and red font, but it is not indicated what it means.
Response: We have regenerated ‘Figure 3’ and we have unified the font colors in order to avoid any ambiguity.
- Section 3.3 surprisingly presents community composition results, because previously, in the methodology it has not been described that samples are taken for this nor the procedure used for identification and counting. This should be explained in section 2 in a section, like the other methods. In Figure 7, the relationship to size groups expressed in biomass is also presented, and there does not appear to be any methodology described for calculating phytoplankton biomass. It is possible that the authors are referring to the photosynthetic pigment equivalent of the size class; but this is not explained anywhere.
Response: We have described about samples collection for total phytoplanktion biomass and community composition in the ‘Materials and Methods’ section 2.1 Study site and sample collection.
“On each sampling occasion, water samples were collected for the determination of dissolved inorganic nutrients, SPM, POC, PN, C and N stable isotopes (termed d13C and d15N) of POM, phytoplankton biomass (Chla), and community composition and biochemical composition of seston.” (see lines 125-128)
We have also described in detail about photosynthetic pigments and chemotaxonomic composition of phytoplankton in the ‘Materials and Methods’ section 2.3.2. (see lines 171 to 196)
In Figure 7, the relationship to size groups expressed in biomass have also been described in the last paragraph section 2.4 Data analysis. (see lines 303-319).
- In the discussion (paragraph 437-440), the authors proclaim this to be original work in their study area; but they should precisely discuss their results with other work identical to theirs as cited here:
Lewitus, A. J., White, D. L., Tymowski, R. G., Geesey, M. E., Hymel, S. N., & Noble, P. A. (2005). Adapting the CHEMTAX method for assessing phytoplankton taxonomic composition in southeastern US estuaries. Estuaries, 28(1), 160-172.
Irwin, A. J., Finkel, Z. V., Schofield, O. M., & Falkowski, P. G. (2006). Scaling-up from nutrient physiology to the size-structure of phytoplankton communities. Journal of plankton research, 28(5), 459-471.
Then, to point out the coincidences or discrepancies of the results obtained in Korea with other work done previously.
Response: We have taken reviewer’s comments and suggestions in full consideration and have incorporated in the revised version of manuscript. (see References #42 and #94)
- The discussion is well presented with the content. However, it suffers from the defect of not considering the microbial loop in the work. Although the authors present that it is a low turbidity zone (no water transparency measurements), the presence of SPM in numbers of 20 mg/L with chlorophyll values of 3 µg/L indicates that the presence of non-photosynthetic material in suspension is important. The C:N ratio does not conform to Redfield values for phytoplankton, so presumably the non-photosynthetic population must be significant and does not appear to have been assessed. Somehow this shortcoming of the paper should be integrated into the discussion. Otherwise, a very interesting paper.
Response: Agree. According to the reviewer’s comment, we have added the necessity of understanding the microbial loop and further study for better understanding of seston dynamics at the end of the ‘Conclusion’ section as follows:
“Given low SPM concentrations and slightly lower C:N ratios than the Redfield ratio in the study system, further research of microbial loop will help us better understand its role in seston dynamics in this unique coastal embayment.” (see lines 594-597)
- The bibliography is well presented, in keeping with the style of the journal.
Response: We appreciate the positive feedback from the reviewer.
- Supplementary materials are very useful, but are not cited in the main text of the manuscript. It is necessary to refer the materials and tables in the text where convenient.
Response: Thanks for critical comment. We have addressed in the main text according. (see lines 321-323, 410, 415)
Round 2
Reviewer 4 Report
Review only in the supplementary matherials table S1 that the first number in first row (20) is 20.0 or 2.0 to not make confussion.
Author Response
Comment 1: (x) English language and style are fine/minor spell check required.
Response:
Thanks for valuable comments. We have checked English and spellings again and again.
Comment 2: Review only in the supplementary materials table S1 that the first number in first row (20) is 20.0 or 2.0 to not make confusion.
Response:
Thanks for valuable comment. The value is 20. To avoid any confusion, we have revised it to 20.0.