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I am satisfied with the changes that you have made to the manuscript and am recommending that it be accepted for publication. Please note that during production on L119 (clean version) Vermij should be changed to Vermeij. Congratulations.
[# PeerJ Staff Note - this decision was reviewed and approved by Xavier Pochon, a PeerJ Section Editor covering this Section #]
I have read over your manuscript and have found that many errors have not been corrected and some new ones were introduced when modiftying the manuscript. This list is not necessarily complete. The line numbers refer to the track changes version.
L18: Does “They” refer to coral reefs or Diadema?
L24-25 addressing barriers … is also implemented. Sounds odd. Perhaps change sentence to say Additionally, barriers to natural recovery such as suitable settlement substrate availability have also been addressed.
L30 … peaked should read peaked in
L33 suggests should read suggest (referring to high rates)
L83 D. antillarum were should read D. antillarum was
L102 recovering is unnecessary in this sentence
L104 algae should read algal
L107 “is considered as a means to” should read “may”
L275 depend should read depends (referring to effectiveness
L287 latitude should read latitudinal
L294 nature should read behaviour
L299 indicates should read indicate
L304 “have observed some settlement collection locations with rates of settlement comparable to settlement measured in” sounds awkward. Perhaps … have shown that some settlement collection locations have comparable settlement rates to those measure in …
L311 Processes of large spatial scale should read Large spatial scale processes
L313 nearshores should read nearshore
L313 transpire later is vague. Please be more specific or delete this phras.
L395 for monthly for should read monthly for
L398 east should read eastern
L474 remaine should read remained
L478 In regional analysis both month … does not make sense. Perhaps A regional analysis showed that both month …
L484 May 2020 (P=0.008). should read May 2020 (P=0.008) was found.
L541 analysis month should read analysis, month
L585 ath should read at the
L746 rate should read rates
L755 is should read has been
L755 fr should read from
L775 location is situated … should read location which is situated …
L827 likely is unnecessary here
L840 effect Sargassum should read effect of Sargassum
L982 for should read of
I have received the comments back from one of the reviewers, who is satisfied that all their suggestions have been incorporated. However, there are many grammatical and spelling errors that need to be corrected before the manuscript can be accepted.
**Language Note:** The Academic Editor has identified that the English language must be improved. PeerJ can provide language editing services - please contact us at [email protected] for pricing (be sure to provide your manuscript number and title). Alternatively, you should make your own arrangements to improve the language quality and provide details in your response letter. – PeerJ Staff
There are still quite a few grammatical and spelling errors (see 'Additional comments'), as well as issues with phrasing throughout the manuscript that make it difficult to understand at times (e.g., some sentences are too long and different tenses are used in a single sentence). I recommend going over the entire text again to rectify these issues or availing of the services of a professional English editor.
The authors have addressed my comments on the experimental design and have now clearly stated the objectives of the study.
The authors have now addressed my comments by revising statistical analyses and figures.
L.22: [laboratory] reared juveniles
L.122: delete the word "include" in this sentence
L.125: [can be a result of] physical transport
L.126: significant effects [on] larval accumulation
L.131: [antillarum]
L.134: what is meant by "settlement peaks" here? Temporally or spatially?
L.188: [Akaike] Information Criterion
I have received evaluations from three expert reviewers. Two of the reviewers have relatively minor, but nevertheless important comments and one reviewer has some more major concerns. I agree with all of the suggestions that have been made. Please provide more background information on the Diadema reproductive cycle and in particular on the factors that may play a role in success or failure of the different stages and the seasonal variation in the introduction. This should nicely set the scene for the discussion of natural recovery and restoration efforts.
**PeerJ Staff Note:** Please ensure that all review, editorial, and staff comments are addressed in a response letter and any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
The manuscript is well written, with relevant background information regarding the status of D. antillarum as a key grazing species for coral reef ecosystems. However, I consider there is not enough background information in relation to D. antillarum reproductive cycle variability under the present conditions of increasing sea surface temperature and the likely role of the drifted Sargassum, which could be considered limiting factors for both, the reproductive success and the survival of larvae at the planktonic phase. See for example, (Karlson and Levitan, 1990. Recruitment limitation in open populations of D. antillarum: An Evaluation. OECOLOGIA and Feehan et al. 2019. The larval influx of D. antillarum to the Florida Keys linked to passage of a Tortugas eddy. Coral Reefs) for background information on dispersal time, distance and oceanographic processes.
The manuscript conforms to the journal standards, and the figures presented are relevant and of adequate quality. Raw data is also supplied.
The experimental design is sound and clear and takes advantage of the appropriate spatial scales of physical and oceanographic varying conditions around Saba Island. The method applied is supported by background information, and the selected temporal replication (monthly samples) takes into consideration the intra-annual variation for larval supply and settlement. The description is clear and sufficient to replicate. The approach provides sufficient and solid data to address the stated question.
The results provide additional evidence of the likely seasonality of D. antillarum spatial and temporal settlement. The findings are in accordance with a higher settlement under relatively calm conditions such as the leeward side of the Island. Despite that the temporal scale of the studies only allows the unravelling of intra-annual variation, the results support a seasonality pattern for D. antillarum larval settlement when contrasted with the literature.
I found the discussion section somewhat speculative in relation to the role of oceanographic processes and predation since there is no evidence gathered during to study that supports those statements. I suggest the authors to provide more literature background such as those references noted in the additional comments. Aspects related to supply-side ecology for D. antillarum such as the time the larvae can stay and travel to figure out likely sources, or the role of eddies where local populations are present. I wonder about the likely influences of higher sea surface temperatures and the massive sargassum drift present around and in the Caribbean in relation to D. antillarum larvae dispersal and survival, does it play a role in the reproduction success and the seasonal variation of larval supply?
The reviewed manuscript described the spatial and temporal (intra-annual) settlement patterns of D. antillarum under different spatial oceanographic settings around Saba Island. The experimental approach is based on artificial collectors distributed quasi-systematically and sampled monthly. The findings support evidence of a likely seasonal settlement pattern, albeit with considerable variation over the years. The results are clear and unambiguous. The analysis strategy clearly expresses the significant spatial and temporal differences. These results are discussed under a number of assumptions 1) Seasonality of settlement (although the actual data does not represent seasonality, rather intra-annual variability), 2) the role of oceanographic features such as currents and eddies at various spatial scales, and their interaction with reef topography, that favors settlement under calm conditions, and 3) predation during the planktonic phase.
This is a well written manuscript that provides valuable data in relation to spatial and temporal settlement patterns of D. antillarum, a key species for controlling macroalgae overgrowth in coral reef ecosystems. I recommend its publication after reviewing the mentioned aspects for the introduction and the discussion sections. The PDF has some annotations of minor corrections.
This short paper is an important contribution to our knowledge of the settlement dynamics of sea urchin populations and has potential implications for the management and restoration of Diadema antillarum populations in the Caribbean. There are some sections where the phrasing is awkward and confusing, and I have pointed these out in the attached document with annotations. Check journal guidelines and follow format for in-text citations and bibliographic entries.
While the experimental design is sound, in general, the submission is too short, and is more of a 'Note' rather than a full research article. Essentially, this study has one objective, addressed by doing one experiment, with one figure showing results. The research question needs to be explicitly defined at the end of the Introduction. More details are required in the methods, particularly on the data analysis section.
Based on the statistical analyses conducted, it seemed like there was no attempt at all to test for interactive effects between predictors (i.e., Month * Location * Depth). Since a significant distinction has been made between "leeward" and "windward" sites in the Results and Discussion sections, it seems imperative to test this statistically (e.g., by pooling data and explicitly comparing settlement rates in 'leeward' versus 'windward' sites. The single Figure showing the results of the study also does not clearly represent what is stated in the Results. I suggest revising this Figure altogether to clearly show the pairwise differences. The line graphs are not necessary especially because 'Month' was treated as categorical predictor in the analysis.
This manuscript is generally well-written and the work was properly executed. My main concern is the length of the manuscript and the single data figure did not clearly represent the results. There was a lot of emphasis in the differences of settlement rates between windward and leeward sites in the Results and Discussion, but not much detail in term of how this was explicitly tested statistically. Overall, this is an important contribution, particularly in the design of efforts to restore D. antillarum populations.
Raw data, metadata, and coding for inferential statistical analyses are all shared. Writing is clear and unambiguous. Good background and context provided.
Investigation performed to a very high standard with solid experimental design.
Data are robust, findings are valid, and conclusions are generally well stated and supported by results.
A solid experiment with important implications for Diadema ecology and population recovery/restoration. The question is well-justified, the methods appropriate, and the data interpreted logically. Without knowledge of the conditions around Saba, one aspect potentially affecting settlement rates that I might suggest the authors consider is food availability to the larvae. Diadema larvae are planktotrophic and can persist in that life stage for relatively lengthy and variable periods. Anecdotal observations we have made during larviculture – as well as published data from the paper referenced below – suggest that the availability of a phytoplankton food source can have a major impact on larval development, settlement, and the success of metamorphosis. Settlement and metamorphosis must be energetically taxing parts of urchin life history, and it’s possible that larvae need a nice big meal or two before they are ready to take them on. If this idea makes sense to the authors, it would be great to see it explored a bit in the manuscript. Are any data on chlorophyll a or other indicators of phytoplankton productivity around Saba available? Could a relative lack of phytoplankton in the winter or abundance in the summer/fall potentially contribute to the observed seasonal settlement patterns?
Pilnick, A. R., Petrosino, A., Hassan, M. M., & Patterson, J. T. (2023). Cue selection and ontogeny reveal larval settlement dynamics of the long-spined sea urchin Diadema antillarum, a keystone coral reef herbivore. Marine Biology, 170(11), 139.
Past this, the below comments are suggestions for consideration that I believe would improve the manuscript.
Specific comments:
L31 – The term “recycled waters” seems a bit odd here. Is this potentially referring to a higher residence time, eddy circulation, something else, or a combination of these factors?
L60+61 – Do “Scleractinian” and “Crustose Coralline Algae” need to be capitalized here?
L65+66 – Period after the sentence. And, some additional context might be warranted on the new die-off. It primarily occurred in areas where localized population recovery had happened, correct? Finally, another paper to consider citing here or in the next paragraph:
Levitan, D. R., Best, R. M., & Edmunds, P. J. (2023). Sea urchin mass mortalities 40 y apart further threaten Caribbean coral reefs. Proceedings of the National Academy of Sciences, 120(10), e2218901120.
L72-74 – Restoration is considered more often than what? Perhaps just “…restoration is often considered…”.
L75 – A more recent translocation study to consider citing here:
Pilnick, A. R., Henry, J. A., Hesley, D., Akins, J. L., Patterson, J. T., & Lirman, D. (2023). Long-term retention and density-dependent herbivory from Diadema antillarum following translocation onto a reef restoration site. Coral reefs, 42(3), 629-634.
L84+85 – Suggest deleting “from the equator”.
L101 – Suggest replacing “island” with “coastline”.
L115+116 – Likely my misunderstanding, but these settlement collectors are on the deeper end given that sites were 11-15 m depth. In the abstract and Fig 2 caption, I interpreted “midwater” as being midway between the surface and bottom. Maybe reword to “water column-suspended” or something along those lines?
L128+129 – Maybe include a settler photo? Could make Figure 2 multi-panel.
L152 – This is Figure 3 rather than Figure 2.
L189 – Site names have been capitalized throughout.
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