Species Composition and New Records of Epiphytic Diatoms on Seagrass Zostera marina from Qingdao Bay, China
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study focuses on the taxa richness of epiphytic diatoms living on Z. marina in Qingdao Bay, China. It is a new study in addition to two previous ones, which, besides reporting high taxa richness of diatoms, also record some new species in China. The study is promising but needs to be revised in terms of the classification system, which would affect the Results and Discussion sections.
Line 87: If I understand correctly, you sampled Z. marina at only one location in triplicate? So you have a total of six plants sampled across both years?
Line 95: Please cite the method according to which the cleaning of organic matter was performed.
Line 97: Please provide the name of the manufacturer of Mountmedia.
Table 1: Are some of these taxa characteristics only for 2022 and others for 2023? Did you examine them seasonally, since you refer to autumn and winter?
Line 101, Table 1: I understand this classification is given by Round et al. (1990). However, the classification system is constantly changing, and it would be best to adopt the latest one represented in Algaebase. In addition, all taxa names should be checked to see if they have changed (e.g. Cyclotella ocellata is currently regarded as a synonym of Pantocsekiella ocellata).
Author Response
Comment 1: This study focuses on the taxa richness of epiphytic diatoms living on Z. marina in Qingdao Bay, China. It is a new study in addition to two previous ones, which, besides reporting high taxa richness of diatoms, also record some new species in China. The study is promising but needs to be revised in terms of the classification system, which would affect the Results and Discussion sections.
Response 1: We greatly appreciate your careful review of our manuscript. We agree that adopting an up-to-date and widely accepted classification system is crucial for scientific accuracy. In the revised manuscript, we have updated the taxonomic framework for all identified diatom taxa to align with the current system presented in AlgaeBase (Guiry 2024). We have carefully verified the current taxonomic status and accepted names of each taxon listed in Table 1. Where necessary, we have updated species names, corrected synonyms, and adjusted higher-level classifications (e.g., order, family) accordingly. All changes are reflected in the revised Table 1, the systematic list in the Results section, and the associated abstract and conclusions where taxonomic affiliations are mentioned.
Comment 2: Line 87: If I understand correctly, you sampled Z. marina at only one location in triplicate? So you have a total of six plants sampled across both years?
Response 2: Yes, this is correct. Sampling was conducted at a single location within the Zostera marina bed near Zhanqiao Pier in Qingdao Bay. During each sampling time (autumn 2022 and winter 2023), three replicate leaf samples were collected randomly from different Z. marina shoots. Therefore, a total of six samples (3 replicates × 2 seasons) were obtained overall.
Comment 3: Line 95: Please cite the method according to which the cleaning of organic matter was performed.
Response 3: We have added the relevant citation for the oxidation method used to clean diatom frustules. The procedure followed the standard acid oxidation technique widely used in diatom studies, as referenced in our previous work (Li et al., 2024).
Comment 4: Line 97: Please provide the name of the manufacturer of Mountmedia.
Response 4: Thank you for reminding us of our oversight. We have updated the text to specify the manufacturer of Mountmedia. The revised sentence (Line 99‒101) now reads: “The materials were then washed with distilled water, dried onto coverslips and mounted on glass slides with Mountmedia (Wako Pure Chemical Industries, Ltd. Osaka, Japan).
Comment 5: Table 1: Are some of these taxa characteristics only for 2022 and others for 2023? Did you examine them seasonally, since you refer to autumn and winter?
Response 5: Yes, Table 1 presents the seasonal occurrence of each diatom taxon. The columns “Autumn” and “Winter” indicate whether a taxon was present (+) in samples collected in October 2022 (autumn) or January 2023 (winter), respectively. Some taxa were found only in autumn, some only in winter, and others in both seasons. This seasonal comparison is summarized in the Results section (Lines 127‒130): “Moreover, it should be noted that 36 taxa of epiphytic diatoms were recorded exclusively in autumn, 43 taxa found exclusively in winter, and 33 taxa were observed in both seasons (Table 1).” We have ensured that Table 1 clearly reflects this seasonal distinction and have added a brief explanatory note in the table caption for clarity.
Comment 6: Line 101, Table 1: I understand this classification is given by Round et al. (1990). However, the classification system is constantly changing, and it would be best to adopt the latest one represented in Algaebase. In addition, all taxa names should be checked to see if they have changed (e.g. Cyclotella ocellata is currently regarded as a synonym of Pantocsekiella ocellata).
Response 6: We sincerely appreciate this critical suggestion. We have comprehensively revised the taxonomic framework of our study to align with the current system in AlgaeBase (Guiry 2024). The following major changes have been implemented:
(1) Updated Higher-Level Classification: The classification of all taxa (Division, Classes, Orders, Families) has been updated to reflect the current consensus in AlgaeBase, moving away from the older system (e.g., Round et al., 1990).
(2) Verification and Update of All Taxon Names: We have meticulously checked the current taxonomic status of every diatom name listed in Table 1 against AlgaeBase. Accepted names have been confirmed, and synonyms have been updated. In our revised table, we have used the currently accepted names, such as Neodelphineis silenda, Monoalveoneis convexa, Pseudoplanothidium delicatulum and Pseudofallacia tenera.
(3) Revision of Text: The Abstract, Results and Conclusions sections have been revised to reflect these taxonomic updates. For instance, references to class-level distributions (Bacillariophyceae, Mediophyceae, Coscinodiscophyceae) have been reviewed and adjusted according to the updated system, and the composition of dominant families/genera has been re-evaluated under the new framework.
These revisions ensure that our study contributes data that is fully compatible with contemporary diatom research and nomenclature.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study investigated the species composition and taxonomic characteristics of epiphytic diatoms inhabiting Zostera marina in Qingdao Bay, China. Through two surveys conducted in October 2022 and January 2023, a total of 112 diatom species (28 families, 55 genera) were identified, including 16 species newly recorded for the Chinese coast. The results showed that the genera Navicula, Amphora, and Nitzschia exhibited the highest diversity, while the genus Cocconeis was confirmed as a ubiquitous species found in all samples. The authors suggest that the epiphytic diatoms do not exhibit strong host-specificity towards their host, the sea squirt, concluding that the diatoms simply utilize the sea squirt as an attachment substrate.
However....there are several weakness in this manuscript.
Major revision.
1. Limited Sampling Period: Data is restricted to autumn/winter months (October and January), making it difficult to fully reflect seasonal changes. Why only there are two samples?
--> The absence of spring and summer data should be clearly stated as a limitation in the Discussion section.
2. Lack of quantitative analysis: The study focuses primarily on species checklists, lacking statistical analysis of dominant species' relative abundance or community indices (e.g., Shannon-Wiener index).
3. Weak basis for host specificity conclusions: Rather than simply concluding lack of specificity through literature comparison, the study would have been more persuasive with comparative data from surrounding sediments or other substrates.
*The conclusions are disappointing compared to the diligently analyzed environmental data. The discussion must be strengthened to derive more meaningful results.
If these concerns are modified and strengthened, we expect it to be published in Diversity.
Minor revision.
Review the entire paper for typos and grammar.
Line 33. 74 seagrass species is -> 74 seagrass species are
Line 43. contributed greater productivity rather than seagrass itself -> contribute more productivity than the seagrass itself
Line 47. reports... varies greatly -> reports... vary greatly
Line 68. knowledge of diversity... are very limited -> knowledge of diversity... is very limited
Line 94. the removal epiphytes -> the removed epiphytes
Line 126. * = are new records -> * = new records
Line 171. distinctly differ from -> distinctly different from
Line 172. studies which only shares -> studies which only share
Line 197. C. convex -> C. convexa
Line 234. 16 new records taxa -> 16 newly recorded taxa
Author Response
Comment 1: Major revision. 1. Limited Sampling Period: Data is restricted to autumn/winter months (October and January), making it difficult to fully reflect seasonal changes. Why only there are two samples?
--> The absence of spring and summer data should be clearly stated as a limitation in the Discussion section.
Response 1: We understand the reviewer’s concern and fully agree that adding the samples mentioned by the reviewer would help us reach a more robust conclusion and enhance the quality of this paper. Please be gently reminded that the aim of this study, as explicitly stated in the Introduction (Lines 75‒77), was to preliminary explore the species composition and taxonomic information of diatoms living on Zostera marina, rather than to compare the epiphytic diatom communities among seasonal changes or fully characterize their seasonal dynamics. To gain insight into the potential seasonal succession pattern, year-round sampling coupled with DNA barcoding will certainly be applied to our future studies. In response to the reviewer’s suggestion, we have stated this limitation in the first paragraph of the Discussion section to avoid overinterpreting our conclusions, as shown in Lines 184‒186: “It should be acknowledged, however, that these comparisons are subject to certain limitations due to the absence of spring and summer data in our study”.
Comment 2: Major revision. 2. Lack of quantitative analysis: The study focuses primarily on species checklists, lacking statistical analysis of dominant species' relative abundance or community indices (e.g., Shannon-Wiener index).
Response 2: Thank you for your valuable comment. We appreciate your constructive feedback regarding the lack of quantitative analysis and statistical evaluation of the community structure. We acknowledge that statistical analysis of relative abundance or diversity indices (such as Shannon-Wiener) would provide additional ecological insights. However, we would like to explain the primary objective of this study, which was to conduct a baseline taxonomic survey of the epiphytic diatom flora on Z. marina in a previously unstudied region of the Yellow Sea. As such, the study was designed to document species composition, identify new records for China, and provide a morphological inventory supported by light micrographs.
Comment 3: Major revision. 3. Weak basis for host specificity conclusions: Rather than simply concluding lack of specificity through literature comparison, the study would have been more persuasive with comparative data from surrounding sediments or other substrates.
*The conclusions are disappointing compared to the diligently analyzed environmental data. The discussion must be strengthened to derive more meaningful results.
Response 3: Thank you very much for your constructive and valuable comments. As suggested, we have thoroughly revised the Discussion section (second paragraph) to address your concerns. Specifically, we have moved away from a simplistic conclusion of “no host specificity” and compared our epiphytic diatom list with that reported from seaweeds in the same coastal waters. This revealed 19 overlapping species, which provides stronger, locally-relevant evidence supporting the idea that sediment acts as a common species pool for epiphytic communities on different substrates. We believe these revisions have significantly strengthened the discussion and derived more meaningful ecological insights from our data.
The revised text now reads: “In a survey of epiphytic diatoms associated with seaweeds, a total of 62 diatom species, belonging to 36 genera, were identified in the coastal waters of Qingdao [33]. The overlap of 19 species with diatoms characterized in this study suggests that these epiphytic diatoms originate, at least in part, from the sediment. In light of this, our results are consistent with the previous observation that epiphytic diatoms on seagrasses generally resemble those found in adjacent meadow sediments.”
Comment 4: Minor revision. 1. Review the entire paper for typos and grammar.
Response 4: We greatly appreciate your careful review of our manuscript. Without altering the original meaning, we have corrected vocabulary and grammar, and enhanced fluency and accuracy to eliminate ambiguities. For example:
Line 35‒36: “Currently, a total of 74 seagrass species is globally recognized, which belong to 13 genera and 6 families” has been revised as “Currently, a total of 74 seagrass species are globally recognized, belonging to 13 genera and 6 families”.
Line 50‒51: “Meanwhile, new diatom species were continuously described from seagrasses…” has been revised as “Meanwhile, new diatom species have been continuously described from seagrasses…”.
Line 70‒71: “However, knowledge of diversity of seagrass epiphytic diatoms are very limited in China as well” has been revised as “However, knowledge on the diversity of seagrass epiphytic diatoms is also very limited in China”.
Comment 5: Minor revision. 2. Line 33. 74 seagrass species is -> 74 seagrass species are
Response 5: Thank you for your reminder. We have revised this accordingly.
Comment 6: Minor revision. 3. Line 43. contributed greater productivity rather than seagrass itself -> contribute more productivity than the seagrass itself
Response 6: Thank you for correcting this detail. We have revised this accordingly.
Comment 7: Minor revision. 4. Line 47. reports... varies greatly -> reports... vary greatly
Response 7: Thank you for your correction. We have revised this accordingly.
Comment 8: Minor revision. 5. Line 68. knowledge of diversity... are very limited -> knowledge of diversity... is very limited
Response 8: Thank you for pointing out this detail. We have revised this accordingly.
Comment 9: Minor revision. 6. Line 94. the removal epiphytes -> the removed epiphytes
Response 9: Thank you for your correction. We have revised this accordingly.
Comment 10: Minor revision. 7. Line 126. * = are new records -> * = new records
Response 10: Thank you for your correction. We have revised this accordingly.
Comment 11: Minor revision. 8. Line 171. distinctly differ from -> distinctly different from
Response 11: Thank you for your correction. We have revised this accordingly.
Comment 12: Minor revision. 9. Line 172. studies which only shares -> studies which only share
Response 12: Thank you for your correction. We have revised this accordingly.
Comment 13: Minor revision. 10. Line 197. C. convex -> C. convexa
Response 13: As this species has been reclassified into another genus, we have removed it here.
Comment 14: Minor revision. 11. Line 234. 16 new records taxa -> 16 newly recorded taxa
Response 14: Thank you for your correction. We have revised this accordingly.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis paper presents a list of diatoms identified in the intertidal zone of the Yellow Sea at a single site on a single species of macrophyte, Zostera. The list is accompanied by light micrographs. The authors cite literature on macrophyte epiphytes. However, a number of comments are needed to ensure the paper meets the standards and quality of the journal Diversity. The micrographs are of poor quality. There is no quantitative assessment of the macrophyte cover species. Handbooks for morphological identifications are not provided. There is no data on the ecology of the species or on the environment in which the communities were discovered. There is no data on the seasonality, abundance, or biomass of epiphytes. Ecological analysis, statistical methods, and comparative floristry are lacking. The mention of pioneer species of the genus Cocconeis is not accompanied by experimental data. However, the authors announce future expansion of their work.
Unfortunately, I believe that due to the limitations of the analysis, the article is not suitable in its current form for publication in Diversity.
Author Response
Comments: This paper presents a list of diatoms identified in the intertidal zone of the Yellow Sea at a single site on a single species of macrophyte, Zostera. The list is accompanied by light micrographs. The authors cite literature on macrophyte epiphytes. However, a number of comments are needed to ensure the paper meets the standards and quality of the journal Diversity. The micrographs are of poor quality. There is no quantitative assessment of the macrophyte cover species. Handbooks for morphological identifications are not provided. There is no data on the ecology of the species or on the environment in which the communities were discovered. There is no data on the seasonality, abundance, or biomass of epiphytes. Ecological analysis, statistical methods, and comparative floristry are lacking. The mention of pioneer species of the genus Cocconeis is not accompanied by experimental data. However, the authors announce future expansion of their work.
Unfortunately, I believe that due to the limitations of the analysis, the article is not suitable in its current form for publication in Diversity.
Responses: Thank you very much for your careful review and constructive feedback on our manuscript. We appreciate your thorough evaluation and the opportunity to improve our work. Below, we provide a point-by-point response to your comments and outline the revisions we intend to make to enhance the manuscript’s quality and suitability for publication in Diversity.
- Comment on the micrograph quality
We acknowledge that some light micrographs may not meet the highest standards of clarity due to the inherent challenges in imaging densely settled diatom frustules and the limitations of light microscopy for certain small or delicate taxa. However, all micrographs were taken using a Zeiss Imager Z2 microscope equipped with differential interference contrast (DIC) and a Axiocam 512 color camera, following standard diatom slide preparation protocols. In general, most of our micrographs meet the requirements for morphological identification of diatoms.
- Comment on quantitative assessment of macrophyte cover
The study focused on the taxonomic inventory of epiphytic diatoms rather than seagrass meadow structure. However, we recognize that contextual data on seagrass cover could strengthen the ecological relevance of our findings.
- Comment on identification handbooks
In the Materials and Methods section (Line 105), we referenced key taxonomic works: Witkowski et al. (2000) and Chin et al. (1982, 1991) for classification.
- Comment on ecological and environmental data
We agree that ecological and seasonal dynamics are important. Our study was designed as a foundational taxonomic survey, but we did collect some relevant data:
Water temperature and salinity were recorded for both sampling dates (autumn: 24.1℃, 30.3 psu; winter: 10.5℃, 30.7 psu) and are reported in the Results.
Presence/absence data per season are provided in Table 1, showing 36 taxa exclusive to autumn, 43 to winter, and 33 occurring in both.
- Comment on lack of ecological analysis, statistics, and comparative floristics
Our study was designed as a baseline taxonomic inventory focused on species composition and new records of epiphytic diatoms on Zostera marina in Qingdao Bay. The primary objective was to document species occurrence and provide morphological documentation through light micrographs. While we did collect samples in two seasons (autumn and winter) and reported presence/absence data for each taxon (Table 1), we acknowledge that quantitative measures such as abundance (cell counts), biomass, or seasonal dynamics were not included. As a taxonomic inventory, our analysis was primarily descriptive and comparative. We did not perform multivariate statistical analyses (e.g., PERMANOVA, nMDS) or ecological indices because the study did not include environmental variables beyond temperature and salinity. We already compared our species richness and composition with previous studies in the Discussion (first paragraph), noting differences and similarities in species numbers and overlap.
- Comment on pioneer species mention without experimental data
The role of Cocconeis as a pioneer epiphyte is well-established in the literatures (e.g., Prazukin et al. 2022; Kanjer et al. 2019). Our statement was based on our observation that Cocconeis spp. occurred in all samples, consistent with their known ecological role.
- Overall suitability for publication
We understand your concerns and hope that the proposed revisions will significantly strengthen the manuscript. Our study provides a detailed taxonomic account of epiphytic diatoms on Zostera marina in the Yellow Sea, with 16 new records for China—a contribution to marine biodiversity documentation that aligns with the scope of Diversity.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have significantly improved the manuscript compared to the previous version.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis article presents a list of diatoms identified in the intertidal zone of the Yellow Sea at a single site of a single macrophyte species, Zostera. The list is accompanied by light micrographs. The authors cite literature on macrophyte epiphytes. The micrographs are of low but acceptable quality. The quantitative assessment of species on the macrophyte surface is poor. Species occurrence is reported in two seasons, October in autumn and January in winter, but no analysis of seasonality in epiphyte abundance or biomass is provided. However, a numerical calculation of species representation in autumn and winter communities and the number of common species in both seasons is provided. A detailed description of species distribution among higher taxa is provided, but no connection to ecology is discernible, despite supplementary data on differences in average water temperatures and salinity in both seasons. Despite the weakness of this article, the authors nonetheless state plans for further expansion of their work. The article in its current form, supplemented and enriched with environmental data and with valid names of the identified species, can be published in the journal Diversity.
