the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Jul 2026
Plankton resistance and resilience through intervals of extreme Cenozoic climate change
Abstract. Earth’s biosphere has undergone major changes through the last 66 million years, first as terrestrial and marine ecosystems recovered from the devastating Cretaceous/Paleogene (K/Pg; 66 Ma) mass extinction and second as life responded to the profound greenhouse to icehouse climate shift across the Eocene/Oligocene transition (EOT; ~34 Ma). This step change in global climate, saw a switch from warm, high CO2 greenhouse conditions of the early Paleogene to cooler temperatures, ice sheets and frigid polar water masses of the Oligocene coolhouse. Despite these profound changes we have limited understanding of the relationships between climate and biosphere and in detail how key ecosystem services and functions respond over different timescales of environmental change. Here we use the fossil remains of primary producer ocean plankton (calcareous nannoplankton) to reconstruct community dynamics across this pivotal interval of Earth history. We present a new high-resolution long-time-series middle Eocene to Lower Miocene (45–21 Ma) nannoplankton dataset, combined with complementary published Paleocene to lower Eocene data, to provide a high-fidelity record of biotic response from the base of the marine food web. This 44-million-year record demonstrates a remarkably enduring ‘background’ state of nannoplankton community stability that emerged around two million years after the K/Pg mass extinction event. This stable state was then only periodically interrupted by short lived excursions of high variance that occurred during geologically rapid warming and cooling events. These ephemeral community perturbations show threshold and scaling relationships, triggered by environmental events broadly equivalent to >~2–3 °C of warming or cooling, with volatility of temperature sensitive taxa underpinning the above-background responses regardless of the background climate state (i.e., greenhouse or icehouse). Community stability, resilience and function are likely sustained through high levels of taxonomic redundancy and the long-term dominance of several key species-complexes that have high adaptive genetic potential across vast global populations, which are maintained in their superabundant extant counterparts.
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- CC1: 'Comment on egusphere-2026-3455', Giacomo Medici, 21 Jul 2026 reply
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RC1: 'Comment on egusphere-2026-3455', Anonymous Referee #1, 03 Sep 2026
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General Comments
This manuscript presents an interesting high-resolution, long-time-series dataset of calcareous nannoplankton community dynamics spanning 44 million years of Cenozoic history, integrating new middle Eocene to Lower Miocene data from the Northwest Atlantic with existing Paleocene–lower Eocene records from the Pacific. By applying the summed coefficient of variation () metrics, the authors evaluate how calcareous nannoplankton responded to major climatic shifts, ranging from Paleocene hyperthermals to the Eocene–Oligocene cooling and Antarctic glaciation.
The overall quality and scope of the manuscript are very good. The core conceptual finding of plankton communities exhibiting a persistent baseline of ecological stability only periodically disrupted when environmental stress exceeds a clear threshold is an interesting contribution withn the palaeoecological palaeoceanographic fields. The manuscript is well-structured and thoroughly illustrated. Although, the manuscript would benefit from some improvement in the discussion and from some clarification along the text. Thus, I recommend the publication in Biogeosciences following moderate revisions addressing the specific comments detailed below.
Specific comments
- I appreciated the usage and discussion of both resistance and resilience in the manuscript, since I believe it is very interesting and still less studied in the nannoplankton record. Although, I encourage the authors to double check the usage of the two terms along the text and carefully use one or the other depending on the context. For example, in lines 325-326 the ability to resist and the recover seems to be subsumed under the term resilience. Please also rephrase these lines.
- The manuscript, specifically the discussion sections, would benefit from a deepening on the comparison of the displayed data with other previously published work worldwide distributed. In fact, the Shatsky Rise and the NW Atlantic have a very different oceanography and hydrography that are not mentioned in the manuscript. Although, especially the NW Atlantic is strongly influenced by local currents and productivity shifts that can affect the data displayed. I suggest to expand in this direction the discussion including also other sites drilled in different areas highlighting better in this way how the baseline threshold of remains constant across different depositional settings. This deeper discussion would also document better, for example during the EOT, that the nannoplankton response was more a synchronized phenomenon in the Atlantic instead to be related to a specific local setting (see e.g. Bordiga et al., 2015 https://doi.org/10.5194/cp-11-1249-2015, Henderiks and Pagani 2008; https://doi.org/10.1016/j.epsl.2008.03.016 and Viganò et al. (2024; https://doi.org/10.1029/2023pa004738).
- Intervals with poorer preservation, especially in the NW Atlantic and in the MECO, can artificially altering relative percentage abundances and influencing by removing the more fragile species? Pleas add a brief comment clarifying and discussing how the sample spacing and visual preservation evaluation through the MECO and along other significantly affected intervals would rule out any artifacts potentially altering the .
Introduction
- Since the manuscript cover very well the different aspect of resistance and resilience, the introduction would benefit from a clearer highlight of both "resistance" and "resilience" definition and how they are operationally distinguished using fossil data.
- State clearly what are the scopes of the manuscript at the end of the introduction, without overstating a linkages to the ecosystem “services and functions” which would include defining more deeply, for example, the carbon export fluxes.
- Line 68-69: “we extend the range of comparable data by 24 Myr, adding new middle Eocene through Lower Miocene records from the North Atlantic Ocean” it is not so clear to which previous data the studied record is adding new outcomes. Please add references of the dataset previously studied and to which the authors are here referring to.
Methods
- Add specifics on the time interval covered by the stratigraphic sequences, or refer more appropriately in the supplementary material, indicating both time interval and also the depth, cm.
- Please add a map with the location of the studied sites, both new ones and those used for comparison. Include the map either in the main text or as supplementary figure.
Results and Discussions
- Line 224-229: cite also Bordiga et al., 2015 (https://doi.org/10.5194/cp-11-1249-2015) since this paper record in the Atlantic Ocean the size reduction in reticulofenstrids across the EOT and the nannofossil assemblage size rapid shift across the EOT together with the trophic/threshold responses across the EOT at ODP Site 1263 (Walvis Ridge), as the authors in this paper and as the other two cited papers. Also Henderiks and Pagani (2008; https://doi.org/10.1016/j.epsl.2008.03.016) and Viganò et al. (2024; https://doi.org/10.1029/2023pa004738) should be cited for similar reasons. Moreover, adding these papers would widen the discussions to a broader and more global context, as suggested above.
Detailed comments
- Line 14: remove “in detail”
- Line 17: define here million year as Ma, and not after in Line 19
- Line 18-19: “of biotic response from the base of the marine food web.” Be more specific referring only to nannoplakton. The presented data are exclusively from the nannofossil community and thus referring to the whole base of the marine food web is widening the concept too much in my opinion.
- Line 34: change “initiation” with a more technical term such as onset or establishment.
- Line 44: change “exoskeletons that provide an abundant and continuous fossil record stretching back over 240 Myr” with “exoskeletons that can be preserved in the deep-sea sediments, providing…”. Otherwise a logical step is missing in the sentence.
- Line 48: remove “mass extinction” it is redundant.
- Line 51: define “a/yrs”
- Line 54: change “asses” with “assessing”
- Line 79: redefine here the IODP acronym.
- Line 81: change “intensity” with “resolution”
- Line 82-83: state clearly which “two events”, also in the introduction they have not been stated so clearly, only in the abstract.
- Line 92: change “%relative abundance” with “relative abundance (%)”
- Line 100: specify the interval both in depth and time.
- Line 123: when stating “several statistically relevant peaks specify better to which peaks you are referring, or make it visually clearer using the figure. Which kind of statistics has been applied to define the statistical relevance? Please specify.
- Line 361-363: do not refer to the evidence on the global warming with “we” as it may seems that this findings come from this manuscript, whereas they come from the previously published papers.
- Figure 1: specify in the caption the presence of hiatuses for those intervals where there are no data reported.
- Probably for the references Newsam (2016) and Routledge (2021) it needs to be added in the refs that they are PhD thesis? This would calrify the sentence in the supplementary information “The middle Eocene to lowermost Oligocene (45.26–32.02 Ma) nannofossil data comes from Newsam (2016), and the lower Oligocene to Lower Miocene (31.90–21.77 Ma) from Routledge (2021), but are previously unpublished.”
- Line 504: fix the typo “eEnvironmental change”.
- Line 5 in supplementary information: change precision with resolution.
- Figure S1: to help the reader, in the caption please make explicit all the symbols and abbreviation, do not refer to them as “in Fig. 1”.
- Table S4: specify from which site those data are from in the caption.
- Table S3: specify in the caption all the acronyms for completeness.
Citation: https://doi.org/10.5194/egusphere-2026-3455-RC1
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- 1
General comments
Very good and novel research on the Eocene – Oligocene boundary with link on a global paleoclimate event. Please, look at my comments to improve the manuscript.
Specific comments
Lines 29-35. Insert these two recent papers on the Eocene – Oligocene boundary and related changes to the paleoenvironment:
Medici, G., Marianelli, D., Cornacchia, I., Gori, F., Brandano, M. 2026. Multi-disciplinary approach to paleokarst occurrence in the Eocene–Oligocene succession of the Apulia Carbonate Platform (Salento, Italy). Facies, 72(2), 17, https://doi.org/10.1007/s10347-026-00729-5 .
Jaramillo-Vogel, D., Bover-Arnal, T., Strasser, A. 2016. Bryozoan beds in northern Italy as a shallow-water expression of environmental changes during the Oligocene isotope event 1. Sedimentary Geology, 331:148–161
Line 76. Describe the specific objectives of your research by using numbers (e.g., i, ii, and iii) at the end of your introduction.
Line 78. Do you need a map for the location of the samples?
Lines 78-104. The methodology needs to be subdivided in 2/3 subparagraphs.
Line 369. "phytoplankton community steady state perturbation". Be more specific on the transient variations of the paleoenvironment. The current statement is incomplete. Please, expand the sentence to fix the issue
Lines 370-373. Sentence too long. Split in two parts?
Lines 365-380. Conclusions too short expand.
Figures
Figure 2. Report the equations for the linear regressions not only R2.
Figure 2. Increase the graphic resolution rising the dpi of the image.
Figure 2. Vertical axes not clear. Do you need adding some detail?
Figure 3. Make numbers and letters larger.
Figure 3. Increase graphic resolution increasing the number of dpi.