the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Jul 2026
Constraining planktic foraminiferal depth habitats for improved polar and subpolar paleoreconstructions
Abstract. Planktic foraminifera serve as critical proxy substrates in paleoceanographic reconstructions. However, the vertical structure of foraminiferal assemblages in the water column remains poorly constrained, particularly in the Pacific Ocean, thus impacting paleoceanographic interpretations from this basin. Here we use depth-stratified plankton tows (0–250 m) collected from the Northern California Current (NCC) to investigate spatiotemporal variability in community composition and depth habitat, with particular emphasis on taxa commonly used in polar and subpolar paleoreconstructions, specifically Neogloboquadrina pachyderma, N. incompta, and Turborotalita quinqueloba. Community composition varied significantly across years but not across latitudes, and comparison to previous NCC studies revealed distinct assemblages across end-member states of the Pacific Decadal Oscillation. Spinose species were most abundant in the upper 25 m of the water column and exhibited consistently shallower average living depths (ALD; 24–31 m) and narrower vertical distributions (VD; ± 13–19 m) compared to non-spinose taxa (38–94 m ± 23–49 m). Turborotalita quinqueloba and N. pachyderma displayed greater depth habitat variability across the study interval, whereas N. incompta exhibited a more stable, constrained depth habitat. Depth habitats in the NCC were shallower when compared to previous studies from other ocean basins, likely due to distinct genotypes inhabiting the study region compared to previous studies concentrated in the North Atlantic and Arctic Oceans. Results herein highlight the need to develop a nuanced understanding of the ecological and environmental processes that govern foraminiferal distribution in the water column to better refine proxy interpretations, particularly in climatically sensitive polar and subpolar regions.
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Status: open (until 11 Sep 2026)
- RC1: 'Comment on egusphere-2026-3966', Anonymous Referee #1, 19 Aug 2026 reply
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RC2: 'Comment on egusphere-2026-3966', Anonymous Referee #2, 20 Aug 2026
reply
Miller et al. present apparent living depth estimates for foraminifera from a series of plankton tows from the North California Current spanning nine stations and three years. They found that spinose species consistently plotted shallower than non-spinose species. Community composition was primarily driven by year, rather than location, particularly when compared to other similar studies from nearby locations. For example, Miller et al. found a much higher occurrence of polar and subpolar species at their sites when compared to other studies and attribute this to sampling during a cool phase of the PDO. They also found relatively shallow apparent living depths when compared to other nearby studies, which they suggest may be due to the cold PDO phase, and compared to other ocean basins, which could be the result of their inclusion of smaller individuals in their sample, their exclusion of deeper sampling intervals, or regional, potentially morphotype related differences.
I found the paper well written and easy to follow, with a lot of great and easily interpretable figures. The authors do a great job of boiling down their main points and the data appear to be high quality and very worthy of publication. There are a few topics I would appreciate more discussion of, and I have a few minor disagreements with what the authors see in their data (see the line by line breakdown), but I think the manuscript is essentially ready for publication and is very appropriate for Biogeosciences.
Bigger points:
There is no mention in the methods of discrimination between living vs dead specimens. The topic is brought up near the end of the discussion but considering how impactful this could be for the data, I think it merits mention earlier in the manuscript.
I would appreciate more detail on the sample strategy choices. Specifically, why were only the top 300 m towed when most other studies have deeper intervals. Additionally, why did the authors include a smaller size fraction in their study when this does not seem to be the norm and is used as an explanation between the data presented here and other studies. I think this is particularly relevant to paleoclimate interpretations given that those studies typically utilize larger specimens. On this point, there are several instances where the authors invoke small T. quinqueloba as an explanation for data differences, but don’t provide any data showing the frequency of these small specimens. Is that available?
I have a bit of an issue with how the ALDs and VDs are being treated. It seems the authors are treating the data following the conventions of the field, but given the wide range of the sampling intervals, it seems that many of the VDs are quite small and the ALDs are very specific. I think the impacts of binning that is inherent in plankton tows on these depth estimates merits some mention.
I think a deeper and more specific discussion of the paleoclimate implications of this study would be a valuable addition. For example, what do the magnitude of the VDs and interannual ALD variations actually mean. You have great temperature and salinity profiles and some knowledge of interannual climate variability. Could you put these into that context and evaluate what that might mean for δ18O and Mg/Ca?
I would be interested in seeing a figure similar to figure 6, but with absolute species abundance as opposed to relative abundance. I think this would benefit the readers’ interpretations of the ALDs and VDs as relative abundances are controlled by absolute abundance of the species of interest and the other species.
Line by line comments:
Line 18: numbers to back up the more vs less varied habitats?
Line 67: I agree that there are caveats to using δ18O, but there are also caveats to using plankton tows that are worth mentioning, most notably to me, that they only capture a snapshot of each individual’s life cycle.
Figure 1: Maybe this is the whole sample area/map, arrows indicating the location of the NCC would be helpful.
Section 3.2: did you assume that all specimens were caught alive?
Eq 3 and 4: are you using the mean depth of the depth interval for Di?
Line 222: Based on the next two citations, I think you meant (1995, 1996)
Section 3.4.3: Could you plot the locations of the sites from the other studies alongside your study sites, so they are easy to compare? Doing so in the supplement would be fine.
Line 260: Why did you limit your collection depths to the top 300 m of the water column?
Figure 6: I would like to see this figure reproduced in absolute abundances as well. While I see the value in comparing relative abundances, they make it difficult to compare abundance of one species within a site across depths since relative abundances could be impacted by the absolute abundance of the species being looked at or the abundance of the other species.
Line 351: Could this spinose vs non-spinose signal just be a signal of where T. quinqueloba live? Figure 10 seems to answer this question. Maybe somehow that information could be added here.
Line 372: To me, only 0-25 m stands out for 2022, and the rest of the depths show a similar lack of pattern to the other years.
Line 405: A VD of 13 m or 27 m doesn’t really make sense to me when half your sampling intervals are 25 m wide and the other 50 m wide. I understand how the math works and this seems to be the convention, but I think this is worth a mention somewhere.
Line 412: What is the R-squared and p-value for the non-significant species? Would the falconensis and scitula fits be significant without the three outliers? It seems like those could just be weird stations, particularly for falconensis.
Line 454: Is there any statistical significance to the latitudinal trend? To me it seems to be dominated by the deepest two sites for quiqueloba and the farthest north sites for pachyderma and not really existent otherwise.
Figure S2: not sure which is the right word in the sentence starting with “A blue asterisk …”
Line 485: What are the maximum depths that are pulling the Ortiz 1996 averages so deep?
Figure 14: I’m not sure this is fixable given you have so many studies relative to regions/provinces, but my eye finds it much harder to see if there is a grouping trend by symbol shape as opposed to by symbol color, so for me at least, I think it would be easier to draw conclusions of the meaning of symbol shape and color were flipped. That being said, I appreciate that there are way more usable colors than shapes, so this may not be possible.
Figure 14: The province/region seems to change for pachyderma for this study. Is that because the site weighting is changing? I could also be confusing the colors.
Lines 532-541: I think I see the VD trends your describing, but not the ALD trends. Transitional incompta makes up one of the two deepest points. One transitional quinqueloba is shallow, but the other two are fairly deep.
Line 547: saying there is no consistent latitudinal trend doesn’t feel very nuanced. Maybe reiterating that the visual trend isn’t statistically significant would make sense. The next paragraph covers this, but amending this sentence probably makes sense is it is a bit at odds with how you talk about figure 4 in the results section.
Lines 570-576: How are the Ortiz warm PDO data significantly different from your data when the Lane MHW data are not? The Lane MHW data look more different from your data than the Ortiz warm PDO data. This deserves a bit more explanation.
Lines 592-600: I don’t necessarily disagree with the point that your data provide valuable interannual comparisons, I think the comparison to sediment traps needs to be elaborated. Single tows are literally a <1 hour snapshot whereas plankton traps typically capture a longer time interval but have so much flexibility in that regard. I think it’s the sampling interval this paragraph should address more so than the sampling technique.
Line 605: supports or is consistent with? And I think better wording would be “supports the hypothesis of the use of spines….”
Line 628: between “some” depth intervals?
Line 652: Do you have any data to support the large quantity of small specimens claim?
Line 660 to 670: What patterns? This paragraph is an awkward transition from the previous one and feels a bit out of place.
Line 671-678: I’m curious to hear the implications of this discussed in the context of the water column structure. A large VD is more impactful where that spans a wide range of oceanographic controls, whereas a wide VD in the mixed layer or below the thermocline could still capture the same conditions throughout the depth range meaning it wouldn’t matter as much.
Line 738: Are there Arctic quinqueloba or incompta studies? I don’t see them in the plot.
Line 760: Erez et al 1991 is cited in the text, but not in the references.
Citation: https://doi.org/10.5194/egusphere-2026-3966-RC2 -
RC3: 'Comment on egusphere-2026-3966', Lukas Jonkers, 22 Aug 2026
reply
Miller et al present planktonic foraminifera abundance data from stratified plankton tows taken in the Northern California current and compare their observations on depth habitat and community composition with previous work in the region and beyond. Their aim is to provide more insights into the ecology of planktonic foraminifera in this region in order to improve palaeoceanographic reconstructions. The authors conclude that community composition varies temporally, but not spatially (latitudinally) and suggest a role for the Pacific Decadal Oscillation in this pattern. The authors also investigate depth habitat of selected species and find that in comparison to other studies, depth habitat of the studied species were shallower than elsewhere. They attribute this to the presence of genetically different species with distinct ecological preferences.
The data appear of high quality and the aim of the study is relevant (if perhaps a bit narrowly focussed on just palaeoceanography). The manuscript is long and seems to want to deliver too many things at the same time. Importantly, it fails in its objective (according to the title) to provide tangible ways how palaeoreconstructions should be improved, especially with regard to the community composition aspects. This is perhaps because in this study the authors demonstrate variability in the ecology of planktonic foraminifera, but do not really attempt to explore what drives the observed variability. That leaves palaeoceanographers (and others interested in the ecology of this group) with relatively little to work with, because it remains unclear to what degree (time, space) the observations from this study can be extrapolated. The authors at some places in the manuscript mention that we need a mechanistic understanding of what drives depth habitat variability within and among species and what drives community composition in the plankton. I agree, but this study makes no attempt at linking the observations on foraminifera to the actual environment, which really is a missed opportunity. Instead, the authors make some inferences about possible drivers of the observed variability and often rely on a “black-box” explanation of cryptic species. Given that the potential role of environmental or other biotic factors is not assessed at all and that the evidence that cryptic species indeed have distinct ecological preferences is weak (Morard et al., 2024), this attribution to cryptospecies remains speculative. That means that I am left with the question about what I have really learned beyond that there is variability in foraminifera habitat and species composition. Thus, I encourage the authors to streamline the manuscript (perhaps even cut in two) and make a clear choice between documenting variability or trying to explain the observed variability. If the palaeoceanographic focus is to remain, then a section with explicit recommendations on what to do with these new observations is needed.
In addition, I also have several methodological issues that prevent me from recommending publication at this stage. They centre on the fact that the authors group their observations, or weigh observations to abundance in their analysis. This grouping or weighting is not always warranted and likely ignores real (ecological) variability. I detail these concerns below and provide line by line comments at the end of this review.
Lukas Jonkers
Community analysis
The conclusion that there is no compositional variability with latitude seems to be based on only the Shannon indices that are arbitrarily binned. However, the SH index is only one dimension of diversity and may be completely decoupled from community composition. This needs to be made clearer in the text and other dimensions of community composition (like the NMDS) should be explored.
The analysis of the vertical changes in the community composition (in R, SH and NMDS) also groups the observations, seemingly assuming that the observations are replicates and thus ignoring real variability. (I think that also means that the statistical tests are not meaningful.) Why are these analyses not done on a per profile basis? This is especially relevant since very few of the profiles are taken at the same site. The conclusions about vertical patterns (or the absence thereof) in community composition (Fig. 9) are illustrative in this regard as observations are grouped temporally, and all spatial variability in the vertical community composition is obscured.
Figure 7 summarises all observations in a single figure, but it remains unclear how the observations were actually grouped (the mean of all profiles, or by weighting to abundance). And what exactly do we learn? Average composition in spring? That spinose species are in relative terms more abundant near the surface? What are the implications for palaeoceanographic reconstructions beyond what is already known?
The real four-dimensional variability in the assemblages (Fig. 6) is only shown and the case is made that the largest variability is in time. If that is true (and the variation is not caused by spatial aliasing), then the logical question is: what are the environmental differences in time that could explain the differences?
Comparison with previous work on community composition
The authors combine the data after grouping them by calendar year “due to differences in sampling sites” (L231). In the presence of real spatial gradients in the assemblages (as demonstrated here and by the studies by Lane and Ortiz) that were heterogeneously sampled, this approach does not overcome this problem and risks confusing spatial variability with temporal variability.
The approach also ignores seasonal variation in the species assemblages as not all observations were made during the same time of the year (this study spring, the others autumn), without demonstrating whether this is warranted or not (e.g. using sediment trap time series (Ortiz and Mix, 1992)). By design, the comparison also misses any potential changes in the vertical community structure. The latter is perhaps not crucial, but because of the two other reasons the conclusions about temporal changes in the community composition warrant further scrutiny. Would a more fruitful approach not be to do this comparison in environmental space, rather than strictly in time? This is now sort of done indirectly by grouping the data in warm and cold years and then inferring some relationship with the PDO.
The grouping by year is also poorly described. There is mention of the need for raw counts (L231, which in itself might be based on aliquots/splits), which suggests that the groups may be weighted by abundance.
Very late in the discussion (L758) it becomes apparent that some of the profiles contained many small individuals. This not only affects the estimates of ALD and VD, but also the community composition. Please deal with this upfront and not almost near the end of the study.
(Meta) analysis of depth habitat
Throughout their analysis the authors weigh their estimates of the depth habitat of the species to the abundance of the species. They do so based on the assumption that an estimate of the depth habitat based on more specimens is more representative of the true depth habitat. I can to some degree follow the reasoning that higher counts have smaller uncertainty, but the chosen approach also downgrades potentially real ecological variability. Given that we don’t know the uncertainty on the ALD estimates (but the authors could try to estimate this using some sort of rarefaction approach) I think that more discussion about this approach is warranted. I realise that the effect is small (Table 2), but so are some of the differences among the studies (Fig. 14).
How were the datasets included in the meta analysis selected? Were there any spatial constraints? Was the FORCIS database (Chaabane et al., 2023) consulted?
Finally, why are the data grouped by study? It seems more insightful to show the individual observations and cluster/analyse by things like region, environmental variables, and/or (assumed) genotype. Right now this study only demonstrates that depth habitat in these species is variable, but does not quantitatively explore what could cause this variability.
Abundance data
I missed an analysis (and figure) of the abundance/concentration data themselves. Depth-integrated abundances are shown in some places and it is clear that they vary a lot. However, this variability and its causes are not analysed even though population size is an important aspect of ecology.
Line by line comments
Title: There are several reasons why I think the title should be reonsidered:
- The manuscript presents much more than just constraining the depth habitats.
- It takes a large leap of faith to apply the observations from the NCC to polar environments.
- The study does not demonstrate how the insights from this study improve paleoreconstructions.
L26: “crucial role in marine ecosystems”. Do we really know? They are (extremely) rare, have low biomass and we don’t know their position in the food web. Please back up with references or remove.
L42: “having appeared …” make this a separate sentence or remove. Like it is now, this part of the sentence between commas has no connection to the sentence as a whole.
L56: The example is not entirely correct in my view. It’s not that the reconstructions underestimate the temperature, it is only the interpretation that is wrong. Please reword to better reflect this nuance.
L60: “underestimate true variability” see e.g. (Jonkers and Kučera, 2017)
L65: the two avenues mentioned here do not represent the same aspects. Abundance data from tows provide information about where foraminifera occur, geochemical data provide information about the apparent calcification depth. Those two things are not identical (Rebotim et al., 2019). Please make that clear from the beginning to avoid any confusion. It is also worthwhile to return to this point later in the discussion because by constraining the habitat depth, we have not (necessarily) constrained the (apparent or real) calcification depth.
L78: “ecology” please be specific what aspects are alluded to here.
L82: VD vertical distribution. We coined this vertical dispersion as it provides a measure of the vertical range in which the foraminifera were found (Rebotim et al., 2017). To avoid confusion (with depth habitat) I recommend sticking to that term. In addition, “methods developed by Rebotim et al” might be better phrased like “methods used by Rebotim et al”, we only calculated a weighted average and a measure of dispersal.
L122: replace “between April 2022 and May 2025” with “between March and July in 2022, 2023 and 2025” to better reflect that the samples were not taken continuously and only during a specific season. Perhaps also spend a few words describing the sampling strategy: Why was the sampling done at this time of the year? Why were these specific stations visited?
L132: “Foraminifera extraction and assemblage analysis” Since there is no mention of separation of cytoplasm-bearing and empty shells I assume this has not been attempted. This has important consequences as living foraminifera tend to be concentrated at shallower depths (Greco et al., 2019) and this should therefore be mentioned here. It also means that use of the term Average Living Depth is not appropriate as it is unknown if the population shown was actually living or not.
L144: can you please clarify if Globigeroines ruber refers to the species proper, or if G. ruber and G. elongatus were lumped?
L181: “per site” suggests that the counts were summed for each site, but some of the analyses and figures do consider the vertical dimension of community structure.
L269: replace “samples” with “profiles” or “casts” and note that the word “including” suggests that there were other species found than the 13 listed.
L386: consider replacing “constrained” with something like “expressed as”
L532: what is reconstructed about these depth habitats?
L560: “likely not captured…” I’d argue, not explored by binning the data. See above.
L563: “provides perhaps the best insights…” please explain why this is the case and why short-term (seasonal) variability can be ignored. By using temporal snapshots at different locations in time it becomes very difficult to disentangle spatial and temporal variability, especially in the light of pronounced intra-annual variability and small-scale spatial variability (patchiness).
L580: “we find that foraminiferal abundance…” where is this shown?
L582: “... difficult to disentangle …” explain why this might be the case. Probably because they are both associated with warmer conditions. The remainder of the paragraph about preservation is all true, but poorly connected to the observations.
L594: “While sediment trap records…” this depends on the length and continuity of the observations, not on the type of observations. I suggest removing this sentence.
L605: “The presence of spinose species at shallower depths …” I don’t follow this reasoning, deeper living/non-spinose species also need to control their buoyancy otherwise they’d sink.
L613: “Chlorophyll a concentrations are highest…” please discuss whether chlorophyll a is the best indicator of the presence of prey of spinose species.
L618: “prefer to stay” reads like this is an active process, whereas in reality it’s probably selective and survival is more difficult elsewhere. Please reword to better reflect this nuance.
L618: “relatively stable” only vertically and within the mixed layer. Please add this as the surface layer is more variable than the deep layers in time. I’m not sure that nutrients and CO2 are important variables for the prediction of foraminifera depth habitat. Please explain or provide references.
L652: The anomalously high concentrations of this species are not visible in this figure.
L660: “Together, these patterns…” seems vague and not backed up by any data. Also what exactly are “patterns in environmental structure” or “gradients in water column stability”?
L672: “... integrate … over a broader range…” only if they calcify everywhere and at the same rate in the water column. See comment about depth habitat and calcification depth above.
L675: “smoothing or dampening” what is the difference? And why “apparent environmental variability” and not real variability? Please clarify.
L683: do the ALD and VD really decrease with latitude every year? The patterns in VD are hard to see, but it seems that the “general” pattern is driven by anomalously deep ALD at 42N in 2023 and that at this station the concentration of N. incompta was too low to yield reliable results. So how robust are these findings? I recommend to analyse ALD and VD separately and as a function of a more meaningful environmental variable than latitude.
L685: “These observations are corroborated…” I’m not sure I follow the reasoning here completely, why is “stability” of the ALD corroborated by a correlation between ALD and VD? ALD and VD could vary tremendously irrespective of their correlation.
L688: “While this variability may …” this sentence and the remainder of the paragraph is speculation. Either provide evidence that there is indeed a relationship between morphotype or genotype and depth habitat or leave out. Better still, try building a model to explain depth habitat variability as a function of environmental data and morpho/genotype.
L707: “While robust statistical modelling…” yes, I absolutely agree!
L711-718: I doubt this section is needed? This study cannot add anything about questions related to trace element incorporation or isotope partitioning.
L746: “Distinct differences in depth habitat …” without ruling out the possibility that the observed variability reflects environmental factors, the discussion about possible genotype effects, remains speculative.
L758: “Many previous studies…” this size issue should be mentioned in the methods already and its influence should be assessed for both composition and depth habitat.
I looked at the Raw_counts.csv file as this seemed the most basic data. I am happy to see that the count data are made available, but strongly encourage the authors to include more metadata to make the data better reusable. I missed: full date and time, location (latitude, longitude), net type, net aperture, mesh size. I also encourage the authors to deposit code, rather than inferred variables (for ALD, VD, richness and SH).
I appreciate the work that went into the meta analysis. Are all raw data from these studies available (e.g. in the FORCIS database)? If not, I encourage the authors to make them available so the data can be reused. Whether or not the raw data are available making the code available is better than just inferred variables. I also missed important metadata here: precise date and time, size fraction/mesh size, depth of tow intervals.
Fig 1: add the sampling locations of Lane and Ortiz and colour the dots by year and month or season. Instead of showing bathymetry in the background, SST or chlorophyll (or both) to show to some degree the environmental variability in the region. Consider showing a map with all the data in the meta-analysis.
Fig 2: nice!
Fig. 3/4: use either concentrations (preferred) or number of individuals in both figures for consistency. What is the rationale (here and in other figures) to divide 2022 by month, but not 2023?
Fig. 6: can you put station NH85 in one row?
Fig. 7: clarify how this average composition was determined (and why), but see above.
Fig. 14: are the average ALDs and VDs for each study also weighted? How was the overall weighted mean calculated?
Chaabane, S., de Garidel-Thoron, T., Giraud, X., Schiebel, R., Beaugrand, G., Brummer, G.-J., Casajus, N., Greco, M., Grigoratou, M., Howa, H., Jonkers, L., Kucera, M., Kuroyanagi, A., Meilland, J., Monteiro, F., Mortyn, G., Almogi-Labin, A., Asahi, H., Avnaim-Katav, S., Bassinot, F., Davis, C. V., Field, D. B., Hernández-Almeida, I., Herut, B., Hosie, G., Howard, W., Jentzen, A., Johns, D. G., Keigwin, L., Kitchener, J., Kohfeld, K. E., Lessa, D. V. O., Manno, C., Marchant, M., Ofstad, S., Ortiz, J. D., Post, A., Rigual-Hernandez, A., Rillo, M. C., Robinson, K., Sagawa, T., Sierro, F., Takahashi, K. T., Torfstein, A., Venancio, I., Yamasaki, M., and Ziveri, P.: The FORCIS database: A global census of planktonic Foraminifera from ocean waters, Sci Data, 10, 354, https://doi.org/10.1038/s41597-023-02264-2, 2023.
Greco, M., Jonkers, L., Kretschmer, K., Bijma, J., and Kucera, M.: Depth habitat of the planktonic foraminifera Neogloboquadrina pachyderma in the northern high latitudes explained by sea-ice and chlorophyll concentrations, Biogeosciences, 16, 3425–3437, https://doi.org/10.5194/bg-16-3425-2019, 2019.
Jonkers, L. and Kučera, M.: Quantifying the effect of seasonal and vertical habitat tracking on planktonic foraminifera proxies, Clim. Past, 13, 573–586, https://doi.org/10.5194/cp-13-573-2017, 2017.
Morard, R., Darling, K. F., Weiner, A. K. M., Hassenrück, C., Vanni, C., Cordier, T., Henry, N., Greco, M., Vollmar, N. M., Milivojevic, T., Rahman, S. N., Siccha, M., Meilland, J., Jonkers, L., Quillévéré, F., Escarguel, G., Douady, C. J., de Garidel-Thoron, T., de Vargas, C., and Kucera, M.: The global genetic diversity of planktonic foraminifera reveals the structure of cryptic speciation in plankton, Biol. Rev. Camb. Philos. Soc., 99, 1218–1241, https://doi.org/10.1111/brv.13065, 2024.
Ortiz, J. and Mix, A. C.: The spatial distribution and seasonal succession of planktonic foraminifera in the California Current off Oregon, September 1987 - September 1988, Geological Society, London, Special Publications, 64, 197–213, https://doi.org/10.1144/gsl.sp.1992.064.01.13, 1992.
Rebotim, A., Voelker, A. H. L., Jonkers, L., Waniek, J. J., Meggers, H., Schiebel, R., Fraile, I., Schulz, M., and Kucera, M.: Factors controlling the depth habitat of planktonic foraminifera in the subtropical eastern North Atlantic, Biogeosciences, 14, 827–859, https://doi.org/10.5194/bg-14-827-2017, 2017.
Rebotim, A., Voelker, A. H. L., Jonkers, L., Waniek, J. J., Schulz, M., and Kucera, M.: Calcification depth of deep-dwelling planktonic foraminifera from the eastern North Atlantic constrained by stable oxygen isotope ratios of shells from stratified plankton tows, J. Micropalaeontol., 38, 113–131, https://doi.org/10.5194/jm-38-113-2019, 2019
Citation: https://doi.org/10.5194/egusphere-2026-3966-RC3
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General Comments:
This manuscript makes a valuable contribution to our understanding of planktic foraminiferal ecology in the Northern California Current (NCC). The depth-stratified dataset is extensive and provides useful insight into the variability in taxa commonly used in polar and subpolar paleoceanographic reconstructions.
I find the manuscript scientifically sound, and the major conclusions are well supported by the data. The authors have shown that community composition varies among years, that taxa have distinct vertical distributions, and that the depth habitats of commonly used paleoceanographic taxa can vary through time. These results have important implications for interpreting foraminiferal assemblages and associated geochemical proxy records.
The figures are also a particular strength of the manuscript. They are very clear and visually appealing, and the thoughtful use of color and design makes the results and overall story especially easy to follow.
Overall, I find this to be a strong and worthwhile contribution. I recommend publication after technical revisions and do not see a need for major additional analyses or substantial restructuring prior to publication.
Specific Comments:
Throughout the paper hyphens are used for most ranges of values. I would suggest changing these all to en dashes (–) when talking about ranges in numbers, dates, etc.
Make sure to define all acronyms at least once in the paper (m, µm, etc.)
I really like the data layout of Table S1. This is a great resource I would hate for researchers to miss it in the supplemental, perhaps add to the main paper? While comparing this table with Table 2, I noticed one small inconsistency within “this study”: N. pachy 56±39 (table S1) or 57±34 (table 2). Double check all values on tables to make sure correct and consistent.
Why are only 10 species listed in Table 2 and in some figures when 13 different species are identified and talked about throughout the paper?
In Section 5.2 you mentioned the different morphotypes of N. pachyderma and genotypes of T. quinqueloba. Have these been separated and identified in your counts? I agree this would be interesting to go back and see how they differ.
The manuscript would benefit from some stylistic revision to improve the overall flow and readability. Transitional/conjunctive adverbs (e.g., “however,” “therefore,” “thus,” “furthermore,” “conversely,” “herein”, and “as a result”) are used quite frequently. Although these transitions are appropriate, their repeated use can become somewhat distracting as a reader. The authors may wish to use these transitions more selectively to improve readability.
Technical Corrections:
Line 32: Tolderlund spelled incorrectly
Line 41: Havard et al cited 2026 and 2025 in references
Line 50: Spero 1988 not listed in references
Line 67: Mortyn and Charles 2004 not listed in references
Line 70: Davis et al 2020 cited and 2021 in references
Line 102: Define meters (m) at first use
Line 124: Define micron (µm) at first use
Line 211: I would hyphenate species-specific
Line 222: Ortiz reference 1995 listed twice (should be 1995,1996)
Line 235: “to summarize” is used twice in this paragraph. I would rephrase one of those sentences
Line 256: Kretschmer spelled incorrectly
Line 482: Ortiz et al 1990 cited but not in refence list
Line 624: Chaabane cited as 2026 in paper and 2025 in the references
Line 702: Kozdon et al 2009 not listed in references
Line 703: Jonkers et al cited as 2009 and listed in references 2010
Line 743: Greco et al 2021 cited and 2022 in references
Line 750: Darling and Wade 2008 not listed in references
Line 826: I would hyphenate depth-stratified
Line 1095: Morley et al 2017 not cited in the paper