the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Jan 2026
Paleoecology indicates wave climate as key factor in coral reef development
Abstract. The Last Interglacial (~125,000 years ago) experienced global temperatures warmer than today, making it a natural analog for future climate scenarios. Contemporary coral reefs preserve ecological signals that offer valuable insights into past climate dynamics. Here, we examine the fossil reefs of Aruba, Bonaire, and Curaçao to reconstruct wind and wave conditions during this period. While modern reefs across all three islands are confined predominantly to leeward coasts, paleo reefs flourished on both windward and leeward coasts during the Last Interglacial – raising questions as to what mechanisms underlie the spatial asymmetry in reef development through time. Using quantitative analyses of hard coral cover and changes in coral community composition across the Last Interglacial, we document a transition from a well-developed reef dominated by large colonies of Orbicella spp. and Acropora palmata to a less structurally complex system characterized by smaller Orbicella spp. and Diploria spp. colonies, mirroring a ~20 % reduction in hard coral cover by the end of the Last Interglacial. Despite this decline, coral cover remained substantial and did not resemble the Sargassum-dominated nearshore environment observed today. Atmospheric circulation and hydrodynamic models indicate that substantially weaker easterly trade winds and reduced significant wave height at 127 ka initiated robust reef development, which still persisted despite a dramatic increase in wave energy at 124 ka. By highlighting how variations in wave and wind regimes have shaped coral reef growth and resilience in the past, these findings underscore the value of integrating paleoecology and hydrodynamics to advance our understanding of reef stability under future climate change.
Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-6122', Anonymous Referee #1, 17 Aug 2026
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RC2: 'Comment on egusphere-2025-6122', Anonymous Referee #2, 04 Oct 2026
The manuscript “Paleoecology indicates wave climate as key factor in coral reef development” by Boyden et al. explores why the windward coasts of the ABC Islands showed coral reef growth during the Last Interglacial, whereas the windward side of the islands lacks modern coral reef development. They concluded that weaker trade winds and associated lower wave energy were the key factors that explain this different pattern by integrating fossil reef ecology, atmospheric and hydrodynamic models and coastal geomorphology.
Overall, I think the manuscript is well written, has a clear structure, and presents an interesting scientific question and valuable results. I really enjoyed reading the manuscript.
I have provided both major and minor comments below. The comments mainly concern aspects of the methodology and interpretation that I believe would benefit from further clarifications.
Major comments:
1) In the introduction, the authors indicate that accommodation space and relative sea level could not be primary drivers for the absence of Holocene windward reef development, noting that the Holocene RSL rise was slower than that of the LIG. However, my opinion is that the connection between the slower rate of rise and the conclusion that accommodation space is insufficient to explain the current reef distribution is not fully elaborated. I would suggest the authors could provide more detailed justification, perhaps discussing modern bathymetric data for the Holocene and inferred bathymetric constraints for the LIG (perhaps using the fossil record?). This may help provide a clearer comparison of the available accommodation space between the two periods. They can also more effectively exclude accommodation space as a possible cause.
2) In the methodology section “Paleowave generation”: the authors have used two different climate models (CESM and iCESM1.2) to derive wind fields for the LIG127 and LIG 124 time intervals. Could the authors clarify why they used different models for these periods, perhaps in the methodology section? Furthermore, the authors should explain how they verify that the differences observed between the LIG127 and LIG 124 intervals are not artifacts of the different model configurations.
3) If I understood correctly, during the Upper LIG the decline in hard coral cover is also accompanied by a shift towards smaller sub-massive colonies (specifically Diploria spp., Siderastrea spp., Porites spp., and Orbicella spp.) and a notable absence of Acropora spp. I wonder if differential preservation (taphonomic bias) could have played a role in the absence of Acropora in the upper LIG, given its relative fragility compared with the other genera identified by the authors? Thus, can preservation also partly explain the reduction in coral hard cover for this interval? I think it would be beneficial if the authors address this point in the manuscript.
4) The authors provide a very well-reasoned argument for the role of wind-driven wave energy as the primary driver of the reef distribution(absence). However, the discussion of other key ecological factors remains limited. I suggest the authors could expand their discussion to address other potential limiting factors that can explain the reef windward development for the LIG and the modern coral reefs. Specifically, a more detailed comparison and, ideally, quantification of SST, nutrient levels, and turbidity, and surface ocean circulation patterns would help clarify whether these factors can alternatively explain or work alongside wave energy to prevent windward reef development.
Minor comments:
Line 3: It would be helpful to include the exact location of the islands you are studying in the abstract for clarity. I would suggest adding “(Southern Caribbean”) after Curaçao.
Line 26: Add a reference to Figure 1 when introducing the islands and their location. For example “hereafter referred to as the ABC Islands; Fig. 1 ").
Line 243: There is a question mark (?) in the text. Is this a typo or a missing citation?
Line 243: There seems to be a typo in the wind speed units, listed as 0.6 kyr-1 instead of 0.6 m s-1?
Citation: https://doi.org/10.5194/egusphere-2025-6122-RC2 -
RC3: 'Comment on egusphere-2025-6122', Anonymous Referee #3, 08 Oct 2026
This topic is of scientific relevance, identification of paleoecology and hydrodynamics in fossil coral reef growth on the southern Caribbean Islands across the last Interglacial (MIS 5e). Here I draw my comments as follows.
- Local or global event?
In the ms, the authors mentioned that the relationship existing between the coverage of fossil coral development and wave energy/trade wind. However, the spatial asymmetry of the occurrence of coral reefs on the southern Caribbean Islands is a signal (or local event) or global issue. Could we observe a similar pattern in other areas, such as western Pacific Ocean or tropical Indian Ocean? If no, why the southern Caribbean Islands is so special. - Other possibilities and climate mechanisms?
By analyzing of fossil reef ecology and model simulation, the authors infer that wind-driven wave energy would be a key factor on its distribution at MIS 5e. In the ms, lack of other possibilities and climate mechanisms on this issue. Meanwhile, the authors mentioned some climate conditions (e.g., floods, freshwater input) during the time interval. The western tropical Atlantic and the eastern equatorial Pacific warm pool are under the same atmospheric condition. The Intertropical Convergence Zone (ITCZ) migration serves as atmospheric bridge to exchange of water vapors and thermal transports across the isthmus of Panama to both areas. However, in Figure 4, model simulation only focuses on a small area. It’s hard to have a broader discussion on different climate mechanisms. Besides, another possibility of an ENSO-like condition is suggested.
- Other footprints?
In the ms, wind-driven wave energy and trade wind system would play an
important role in controlling fossil reefs at MIS 5e. Wave energy would leave some footprints on terrestrial and marine archives. Could we find any signals (e.g., lithology and sediment composition; grain size, sorting, etc) kept in marine core. Independent index for wave energy is suggested.
Citation: https://doi.org/10.5194/egusphere-2025-6122-RC3 - Local or global event?
Data sets
Electronic Supplementary Material for: "Paleoecology indicates wave conditions as key factor in coral reef development" Patrick Boyden et al. https://doi.org/10.5281/zenodo.15674470
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- 1
I have important methodological questions, specifically relating to the subsection 2.2 “Paleo wave climate generation”
Here are some of my main concerns: (1) Why use multidecadal mean winds as constant 24-h forcing, and what does this imply for extreme-wave events? In order to extend on this topic, it appears that the study uses multidecadal mean wind speed and direction from the paleoclimate simulations and then applies these values as a spatially uniform, constant wind field for 24 hours in Delft3D. Given the nonlinear relationship between wind forcing and wave generation, how representative is this approach of the actual LIG wave climate? Could the use of mean winds underestimate the contribution of episodic high-wind and extreme-wave events to the overall wave climate? Were these limitations considered? (2) How do they separate genuine LIG127–LIG124 climate change from differences between CESM and iCESM1.2? It seems that the LIG127 and LIG124 wind fields were derived from different climate models (CESM and iCESM1.2, respectively), so, how exactly did the authors distinguish genuine temporal changes in LIG atmospheric circulation from structural differences between the two climate models? I think this is particularly important because the study interprets the large increase in wind speed and wave height between 127 and 124 ka as evidence for a change in wave climate and coral structure and cover. (3) Was the 127–124 ka wave change tested across the same climate model or multiple models? Specifically, was the inferred increase in wind and wave energy between 127 and 124 ka reproduced when both LIG time slices were simulated using the same climate model? Alternatively, was the result tested across multiple paleoclimate models or simulations, which would be an appropriate step to follow, right? (and highly recommended in this case)? Without such a sensitivity analysis, how robust do you think is the magnitude and even the direction of the inferred change? Could it be overestimating the inferred change?. (4) How sensitive are the wave results to uncertainty in the paleoclimate-model wind forcing? I believe the use of a spatially uniform wind field assumes that wind speed and direction are homogeneous across the model domain, which is quite unreal. How might this major assumption affect the modeled wave field around Aruba, Bonaire, and Curaçao, particularly given their different orientations, island geometries, and potential wind-channeling effects at these islands? Were these differences even considered or, at least, discussed? (5) How well do offshore modeled wave conditions translate into actual reef-scale exposure, particularly the inferred windward–leeward differences? The wave conditions are extracted at offshore virtual buoy locations specifically to minimize the effects of paleobathymetry and relative sea level. However, the ecological observations concern shallow-water reef development, so how well do offshore significant wave height and peak period represent the wave energy actually experienced at the reef crest? Is there any way to test this important point? Did you guys considered any alternatives? (6) Since the ecological interpretation appears to rely on differences between exposed/windward and sheltered/leeward reef settings, can the modeled wave fields quantitatively reproduce these spatial differences? In other words, does the model independently predict the observed windward–leeward pattern in reef development?
Another quite relevant point is that correlation does not imply causation. The paleoecological record documents substantial changes in reef community composition and development, while the hydrodynamic simulations demonstrate that the LIG climate states could have produced different wave conditions. However, what evidence demonstrates that wave climate was a primary driver of these ecological changes rather than a secondary or interacting driver among multiple co-varying environmental changes? Can the authors quantitatively distinguish the contribution of wave exposure from other potential controls, such as SST, carbonate chemistry, sedimentation, water depth, and circulation?
I believe that If the objective of the study is to attribute reef development specifically to wave exposure, the lack of a leeward fossil (and modern!) comparison is a significant limitation. The paleoecological survey was restricted to fossil reef outcrops on the windward coasts of the ABC islands. Given that the central hypothesis links reef development to wave climate, how can the authors distinguish the effects of wave exposure from other environmental or geomorphic controls in the absence of fossil reef sites from the contrasting leeward environments? Are there any? and, would comparisons with modern windward and leeward reef communities provide an independent test of the proposed relationship between wave exposure and reef development? If such data are available, why were they not incorporated into the analysis, or, at lastly, stated as a study limitation, or suggested as a topic for future study? Lastly, could the restriction to fossil reefs exposed above sea level on windward coasts introduce a preservation or sampling bias? In particular, could differences in erosion, accommodation space, uplift, or exposure potential between windward and leeward settings influence which fossil reefs are preserved and accessible for sampling? Did you guys consider this as well?
Overall, this is a well-written manuscript presenting interesting and potentially important results. I believe, however, that further consideration of the issues raised above, together with additional methodological analyses or sensitivity tests where feasible, would substantially strengthen the study and provide greater support for its main findings and interpretations. I look forward to seeing how the authors address these points.