Two decades of coral carbonate production within and across geomorphic zones

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Diederiks, Nicola K. Browne, David E. Carrasco Rivera, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6668724/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 31 Aug, 2025 Read the published version in Coral Reefs → Version 1 posted 9 You are reading this latest preprint version Abstract While reef resilience is widely studied, there is increasing recognition of the need to assess it through carbonate production estimates. This study investigated gross carbonate production on Heron Reef (southern Great Barrier Reef) over a 20-year period, examining responses to environmental disturbances and the role of key benthic taxa. Drawing on data from over 30 sites across four geomorphic zones, we identified branching Acropora , tabular Acropora , and Montipora as the primary contributors to carbonate production due to their high abundance, fast growth rates, and elevated CaCO₃ output. Heron Reef’s average annual production rate of 18.45 kg CaCO₃/m²/year places it among the more productive clear-water reefs in the Indo-Pacific. A strength of this study lies in its spatial and temporal scope, providing a refined understanding of how disturbances shape reef-building capacity across zones. Heron Reef showed strong resilience, with rapid carbonate production recovery following major events, although sharp declines were recorded during severe bleaching, such as in 2024. This analysis focused on carbonate production and does not incorporate direct bioerosion measurements, which are necessary to calculate full carbonate budgets and long-term reef accretion potential. Future work should address this gap by integrating erosion data to improve estimates of net production. Nonetheless, this study offers valuable insight into the ecological processes supporting reef resilience. It underscores the importance of high-resolution, long-term datasets for understanding carbonate dynamics and informing targeted conservation strategies in the face of accelerating climate change. Coral reef resilience carbonate production benthic composition environmental disturbance geomorphic zones ecological time series Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Recent studies suggest that reef resilience and functioning is declining (Tebbett et al., 2023) and, as such, reefs are struggling to recover from cumulative impacts such as climate change (Wilkinson, 2006), pollution (Bartley et al., 2014), and over-exploitation (Wolff et al., 2018). Resilience is a crucial concept in ecosystem management, defined as an ecosystem’s capacity to absorb disturbances and adapt to change while maintaining ecosystem functions (Unsworth et al., 2015). Repetitive disturbances result in significant reductions in coral cover, biodiversity, and reef-building capacity (De'ath et al., 2012). For example, the Great Barrier Reef (GBR), despite being one of the most well-managed coral reef systems (Hughes et al., 2017), has experienced decreased resilience to repetitive disturbance, as evidenced from significant reductions in coral cover since the 1990s (De'ath et al., 2012). Coral composition is also changing as disturbances and global climate change lower diversity and shift assemblages to more stress-tolerant, slow-growing species (Mellin et al., 2019). Since the 1980s, the GBR has experienced eight mass bleaching events, resulting in declining coral cover as well as decreased rates of coral recruitment, both of which limit capacity for recovery and increase vulnerability to future disturbances (Henley et al., 2024). As climate change exacerbates these stressors, understanding reef resilience across spatial and temporal scales is crucial. Large-scale field datasets that monitor coral reef health are essential for protecting and managing reef health through repetitive disturbances (Souter et al., 2021; Tebbett et al., 2023). Key metrics for assessing reef resilience include coral abundance, community composition, and reef carbonate production (Perry et al., 2018). While these metrics are essential to understanding reef resilience, our study uniquely highlighted the role of carbonate production across time and space, offering a new perspective in resilience assessments. Carbonate production reflects coral growth and productivity, and is a key indicator of long-term reef structure viability (Januchowski-Hartley et al., 2017). Coral reef growth relies on a positive balance between gross calcium carbonate (CaCO₃) production and erosion (Uthicke et al., 2014). This "carbonate budget" requires CaCO₃ production rates from corals and crustose coralline algae (CCA) to exceed erosion rates to maintain or increase reef structure (Brown et al., 2020). The quantification of CaCO₃ production can provide crucial insights into the reef’s long-term stability and, therefore, resilience (Chave et al., 1972; Contreras-Silva et al., 2020). Recently, the application of the carbonate budget method has become increasingly popular for assessing reef resilience, by quantifying the impact of disturbance events and tracking carbonate production over several years (Ryan et al., 2019). For example, carbonate budgets have been used to evaluate the impact of bleaching events, storm damage, and anthropogenic stressors on coral cover and composition, and how these changes translate to net carbonate production and long-term reef stability (Lange et al., 2020). Such an approach integrates traditional benthic assessments with productivity data, thereby offering insights into reef productivity and resilience beyond standard in-water assessments (Browne et al., 2021). However, as with most methodologies, limitations exist when assessing carbonate budgets both spatially and temporally. One of the key limitations of carbonate budgets relates to the scale of application. Typically, data for carbonate budgets are collected along a small number of transects from which data is then extrapolated to cover entire geomorphic zones (Silbiger et al., 2017). This likely oversimplifies spatial variations, thereby missing important within and between zone variations (Perry et al., 2015). Understanding benthic community changes and carbonate production requires examination at the geomorphic scale (Vercelloni et al., 2023), which to date has rarely been conducted in carbonate budget studies (Lange et al., 2020). Variations in carbonate production within geomorphic zones are influenced by depth, disturbance history, and exposure (Brown et al., 2018). To address this issue, carbonate budgets require higher spatial and temporal resolution data sets, as well as the integration of data from multiple sites over extended periods of time (Cornwall et al., 2021). Long-term datasets are critical for identifying historical baselines, tracking trends and predicting future changes in carbonate production. Importantly, such datasets are rare due to time and financial constraints (Reverter et al., 2022). This study aimed to assess the dynamics of gross carbonate production using benthic community data collected over two decades within and across coral reef geomorphic zones. We utilised the annual benthic dataset from Heron Reef, which offers a 20-year record for over 30 data collection sites across four geomorphic zones (Roelfsema et al., 2021a). This dataset allowed us to explore coral community dynamics and carbonate production during a period of significant environmental change, including chronic stressors and acute disturbances such as disease outbreaks (2004-2008) (Haapkylä et al., 2010; Roff et al., 2011), extreme weather events (2019) (Mellin et al., 2019), and coral bleaching (2016, 2017, 2024) (Hughes et al., 2017; Henley et al., 2024). Therefore, the objectives of this paper were: (1) to evaluate the benthic composition over time and space; (2) to identify the community driving carbonate production over time; (3) to examine spatial variations in carbonate production across geomorphic zones; and (4) to explore the potential implications of these changes for management and conservation. This comprehensive analysis provided new insights into the short-term recovery potential and long-term stability of coral reefs such as Heron Reef. Methods Study Site Heron Reef, located in the Capricorn-Bunker group on the southern GBR (23.4425° S, 151.9144° E), was chosen for its unique benthic dataset. The reef is divided into four geomorphic zones: inner and outer reef flats, as well as northern and southern reef slopes (Phinn et al., 2012). The northern reef slope experiences higher wave intensity compared to the southern slope, which is typically sheltered. Slope data was collected at 4-7 m depth (Roelfsema et al., 2021b), whereas reef flat data was collected at 0-2 m depth. These geomorphic zones offer unique benthic characteristics, providing valuable data for studying reef carbonate dynamics (Vercelloni et al., 2023; Carrasco Rivera et al., 2025). The middle lagoon area was excluded, due to lack of data points and low coral cover. Benthic Composition Over Space and Time Benthic composition data collection and analysis has previously been described in detail by Roelfsema et al. (2021a) and Vercelloni et al. (2023). In short, from 2002 to 2024 (excluding 2003 and 2004), georeferenced photo quadrats were taken annually at 2-3 m intervals along stratified random transects across Heron Reef. Each quadrat represents a 1 x 1 m area and transects were positioned to capture representative habitats across and within geomorphic zones. Transects within each geomorphic zone were defined as hexagons (100 m 2 ) surveyed each year, generated using hierarchal clustering based on Euclidean distances between geo-located photo quadrats (Vercelloni et al., 2023). Benthic community composition in photo quadrats were analysed using CoralNet (2002-2018) (González-Rivero et al., 2020) and ReefCloud (2019-2024) ((AIMS), 2024) machine learning algorithms. An associated label set (Appendix A) was used for annotating photo quadrats, as determined by Roelfsema et al. (2021a). This resulted in the identification of coral cover down to family and/or genus level. Here, plate/encrusting Acroporidae corals were merged as the software was not able to distinguish between them. Dead hard coral (DHC) was classified as “turf algae/DHC” due to the widespread presence of algae on it, and all algae that did not fit an established label were classified as “Algae Other”. CCA and Halimeda can often be important sources of carbonate production on reefs, and hence their specific abundance was recorded. For all benthic communities, annual percentage cover was calculated per geomorphic zone by attributing all transects to their associated zone(s) and divided by the total area of each zone to compare them on the same scale. Carbonate Production Over Space and Time Gross carbonate production was calculated using a multi-step process. Planimetric area provided a measure of size of the coral habitat (m 2 ), which was then adjusted by a rugosity factor (Table 1, equation 1). Rugosity is a measure of the complexity of the reef structure and plays a crucial role in accurately estimating carbonate production rates. Given that no in-situ data for rugosity was available, we developed a proxy measurement using total hard coral cover data. Specifically, we applied the software WebPlotDigitizer to estimate rugosity values based on reconstructed trajectories of percentage coral cover and reef rugosity from Bozec et al. (2015) (Appendix B). The underlying assumption driving this approach is that as coral cover increases, it correlates with changes in reef complexity, as reflected by increases in rugosity (Bozec et al., 2015). Area covered (cm 2 ) by calcifiers was determined by multiplying the calcifier average percentage cover by zone habitat area, as previously calculated (m 2 ; Equation 2). Calcification rates for hard corals were sourced from literature (Appendix C), incorporating factors like linear extension and carbonate density (Equation 3) (Dove et al., 2020). Different rates were applied per zone to account for environmental variability (Appendix C) (D'Olivo et al., 2013). A conversion factor was used to adjust for volumetric growth, and aid in quantifying adjusted carbonate production over time (Equation 4) (Silbiger et al., 2017). Subsequently, total mass carbonate (kg/year) was calculated by multiplying the adjusted calcification rate by the area occupied, (Equation 5). This value was then normalised by dividing the total mass carbonate by zone habitat area (Equation 6). Finally, to determine gross carbonate framework production, all normalised coral carbonate production rates were compiled (Equation 7). To determine CCA carbonate production rates, we included parameters related to surface area and coverage, which relates to their distinct growth patterns and calcification mechanisms. Table 1 : Equations used for calculating metrics of interest, including the relevant variables and their respective units. Equation Variable Units Equation 1 Zone habitat area m 2 Planimetric area (m 2 ) x rugosity 2 Area occupied cm 2 Zone habitat area x (coral % cover / 100) x 10000 3 Calcification rate g/cm 2 /year Linear extension (cm/year) x density (g/cm 3 ) 4 Adjusted calcification rate g/cm 2 /year Calcification rate(g/cm 2 /year) x conversion factor 5 Total mass carbonate kg/year Adjusted calcification rate (g/cm 2 /year) x area occupied (cm 2 ) / 1000 6 Normalised coral carbonate production rate kg/m 2 /year Total mass carbonate (kg/year) / zone habitat area (m 2 ) 7 Gross carbonate framework production kg/m 2 /year ∑ Normalised coral carbonate production rate (kg/m 2 /year) Using this multi-step methodology, we assessed total gross annual carbonate production rates to understand both overall spatial trends in reef carbonate production and how it has varied over time. Specifically, we reviewed the spatial variation between reef zones to understand the contribution of different geomorphic zones to carbonate production, and as well as identifying which calcifiers had the greatest inputs. Additionally, we identified temporal trends and key contributors to assess how disturbances, including coral disease outbreaks and bleaching events, have affected the reef's ability to recover and maintain its carbonate production over time. Results Benthic Composition Over Space and Time Differences Across Geomorphic Zones Sand dominated the inner reef flat (mean = 53.6%) across the study period. Initially, sand cover was low (27.8% ± 2.28 SE) in 2002, before increasing to a maximum of 66.3% (± 0.09 SE) in 2007 (Figure 2a) after which cover remained relatively stable. Turf algae/DHC cover exhibited an inverse relationship to sand, but generally remained stable, averaging 32.8% across the study period. Turf algae/DHC cover was initially observed to be at 67.2% (± 3.73 SE) in 2002, reaching 19.9% (± 0.03 SE) in 2007, often increasing in years when sand cover declined. Hard coral cover was consistently low (<10%), but gradually increased over time, peaking in 2019 at 15% (± 0.04 SE). On the outer reef flat, turf algae/DHC was the dominant benthic category, which remained relatively stable over time (~75%) except for a decline to 47.1% (± 0.03 SE) in 2005 (Figure 2b). Similarly, hard coral cover experienced gradual fluctuations from 12.7% (± 0.13 SE) to 14.1% (± 0.19 SE) over the same period. Algal cover remained consistently low, ranging between 0.2% and 4.0%, while soft coral cover was negligible (<2%). In both the northern and southern reef slopes, hard coral cover was considerably higher than on the reef flats (averaging 39.3 and 42.5%, respectively), exhibiting inverse trends with turf algae/DHC (Figure 2c and 2d). On the northern reef slope, hard coral cover decreased from 45.3% (± 0.05 SE) in 2002 to 12.9% (± 0.07 SE) in 2010, followed by a steady increase of approximately 5% per year, reaching 54.8% (± 0.41 SE) in 2023, and then falling to 26.2% (± 0.66 SE) in 2024 (Figure 2c). Conversely, turf algae/DHC cover decreased from 48.4% (± 0.49 SE) in 2002 to 32% (± 0.33 SE) in 2023, before doubling to 64.1% (± 0.63 SE) in 2024. Similarly, on the southern slope, hard coral cover increased from 34.8% (± 0.86 SE) in 2002 to 48.3% (± 0.01 SE) in 2023, dropping again to 32.1% (± 0.07 SE) in 2024 (Figure 2d). Turf algae/DHC exhibited an inverse relationship with hard coral, decreasing over time to 44.9% (± 0.88 SE) in 2023, and increasing to 61.3% (± 0.07 SE) in 2024. Coral Community Composition Branching Acropora was the primary contributor to hard coral cover, followed by ‘Tabulate and Corymbose Acropora’ (hereafter referred to as tabular Acropora ) and Plate/ Encrusting Acroporidae (hereafter referred to as Montipora ) (Figure 3). Each zone exhibited unique trends, with the southern reef slope exhibiting the most fluctuations in branching Acropora (Figure 3d). On the inner reef flat, branching Acropora cover rose from 0.1% (± 0.01 SE) in 2002 to 3.4% (± 0.08 SE) in 2016, before dropping to 1.9% (± 0.04 SE) in 2024 (Figure 3a). On the outer reef flat, branching Acropora fluctuated around 10% cover, dropping to ~5% in 2011, 2015, 2017 and 2024. On the northern reef slope, pre-2007 branching Acropora was greater than 20%, before declining rapidly from 2008 to 2010 to between 5-10%. Since 2010, cover has gradually increased peaking in 2023 at 26.8% % (± 0.04 SE), before declining to 12.7% (± 0.05 SE) in 2024. (Figure 3c). The southern reef slope experienced marked fluctuations in branching Acropora as well, with cover dropping sharply from 35.7 (± 0.45 SE) in 2005 to 1.2% (± 0.02 SE) in 2008, peaking at 39% (± 0.25 SE) in 2013, then gradually decreasing to 33.7% (± 0.13 SE) by 2023 (Figure 3d). In 2024, branching Acropora cover fell to 25% (± 0.13 SE). Tabular Acropora and Montipora showed less variability. On the inner reef flat, tabular Acropora increased from 0.72% (± 0.12 SE) in 2002 to 1.4% (± 0.01 SE) in 2016, then declined to 0.7% (± 0.02 SE) by 2024 (Figure 3a). Northern reef slope tabular Acropora and Montipora cover increased from 11.1% (±0.61 SE) in 2002 to 18.3% (± 0.04 SE) by 2023 but then dropped to 9.7% (± 0.02 SE) in 2024 (Figure 3c). On the southern reef slope, tabular Acropora and Montipora cover fell from 19.8% (± 0.65 SE) in 2002 to 1.8% (± 0.17 SE) in 2006, then rose to 6% (± 0.62 SE) by 2023, and dropped further to 2.8% (± 0.02 SE) in 2024 (Figure 3d). Montipora , the third-largest group, showed distinct trends: northern reef slope cover decreased from 9.1% (± 0.18 SE) in 2002 to 5.6% (± 0.06 SE) in 2023, and dropped to 1.6% (± 0.01 SE) in 2024 (Figure 3c). On the southern reef slope , Montipora rose from 2.3% (± 0.3 SE) in 2002 to 4.3% (± 0.23 SE) in 2023, but then halved to 2% (± 0.01 SE) in 2024 (Figure 3d). Algal Community Composition Dominant algal groups on Heron Reef consisted of Halimeda, 'Algae Other’, and CCA (Figure 4). On the northern reef slope, Halimeda increased over time, from 0.1% (± 0.01 SE) in 2002, to 5.1% (± 0.01 SE) in 2024 (Figure 4c). CCA increased from 0.1% (± 0.12 SE) in 2002 to 4.4% (± 0.14 SE) in 2024. Other algal cover was generally low, remaining under 3%, although there were some observable fluctuations in 'Algae Other.' For instance, on the inner reef flat, 'Algae Other' cover rose from 0.5% (± 0.13 SE) in 2002 to 7.8% (± 0.29 SE) in 2007, before gradually decreasing to 0.8% (± 0.07 SE) by 2023 (Figure 4a). A similar increase was observed on the outer reef flat, with ‘Algae Other’ peaking at 2.5% (± 1.67 SE) in 2007 and then declining to 1.2% (± 0.04 SE) in 2024 (Figure 4b). Carbonate Production Over Space and Time Total Gross Annual Carbonate Production During the study period, average total gross annual carbonate production displayed significant variations (Figure 5). From 2002 to 2005, reef carbonate production rose from 15.8 kg/m²/year (± 0.08 SE) to 20.1 kg/m²/year (± 0.11 SE), driven primarily by branching Acropora , tabular Acropora , and Montipora , especially on the reef slopes. However, in 2008, carbonate production dropped to 9.2 kg/m²/year (± 0.05 SE). From 2008 to 2015, production rebounded at a rate of approximately 3 kg/m²/year, driven largely by the rapid recovery of branching Acropora. A decline in carbonate production in 2018 followed the bleaching events of 2016 and 2017, but the reef recovered relatively rapidly, reaching a peak production of 22 kg/m²/year (± 0.11 SE) by 2023, but then dropped to 14 kg/m²/year (± 0.07 SE) in 2024 following the mass bleaching event. Differences Across Geomorphic Zones The northern reef slope was the most productive zone (Figure 6), dominated by branching Acropora , Montipora , and tabular Acropora . In this area, branching Acropora contributed an average of 3.34 kg/m²/year (± 0.21 SE), while Montipora and tabular Acropora contributed 2.76 kg/m²/year (± 0.18 SE) and 1.89 kg/m²/year (± 0.15 SE), respectively. The 2017 data showed some singular high values for groups like ‘massive other’ (1.12 ± 0.11 SE), encrusting Porites (1.05 ± 0.1 SE), Pocillopora (1.01 ± 0.09 SE), and ‘plate other’ (0.78 ± 0.03 SE). In contrast, the southern reef slope was dominated by branching Acropora , contributing an average of 4.55 kg/m²/year (± 0.23 SE), followed by Montipora at 0.88 kg/m²/year (± 0.17 SE) (Figure 6d). The reef flats had lower carbonate production, with the outer reef flat being more productive than the inner reef flat due to more branching Acropora (Figures 6a and b). Carbonate production was increased slightly in the inner reef flat by the contribution of ‘Algae Other’, whereas the production on the reef slope was raised by increases in key algae such as Halimeda and CCA. Over the course of the study, significant contributors on the inner reef flat included branching Acropora (0.98 ± 0.18 SE), and Pocillopora (0.51 ± 0.11 SE). The outer reef flat had key contributors such as branching Acropora (2.11 ± 0.41 SE), Montipora (1.15 ± 0.21 SE), and tabular Acropora (0.99 ± 0.08 SE). Discussion This study provided a multi-decadal and high-resolution assessment of carbonate production, derived from benthic community dynamics. Spatially, our findings demonstrated distinct differences in gross carbonate production across four geomorphic zones (inner and outer reef flat, northern and southern reef slope). Differences in gross carbonate production were driven by coral cover and benthic composition, while temporal changes in gross carbonate production likely resulted from benthic community responses to acute disturbances such as disease outbreaks, thermal stress, and extreme weather events. Importantly, our approach demonstrated the long-term implications of disturbance events on a reef’s carbonate production potential and stability. Benthic Composition over Space and Time Our analysis revealed strong spatial and temporal variability in benthic composition across Heron Reef, shaped by both geomorphic setting and disturbance history. Hard coral cover was consistently higher on the reef slopes compared to the flats, with the southern slope showing the highest overall values and most pronounced fluctuations—largely driven by the dominance and instability of branching Acropora . In contrast, reef flats were dominated by sand and turf algae/DHC, with limited coral cover and minimal recovery across the study period. A marked decline in hard coral cover and corresponding rise in turf algae/DHC in 2024—particularly on the slopes—suggests acute sensitivity to the recent bleaching event (Nyberg and Wright, 2024). Notably, branching and tabular Acropora , key contributors to reef accretion potential, experienced substantial post-disturbance declines. The increase in CCA and Halimeda on the northern slope over time may indicate a shift in the reef's calcifying community, with implications for carbonate production dynamics (Kennedy et al., 2017). These spatial patterns highlight the importance of accounting for geomorphic context when assessing reef condition, resilience, and contributions to carbonate budgets (Cornwall et al., 2021). Gross Carbonate Production Over Time On average, annual gross carbonate production rates on Heron Reef were 18.45 kg CaCO₃/m²/year, which is high compared to many other clearwater reefs in the Indo-Pacific. Our values are also potentially more accurate compared to previous studies, due to the fine spatial scale of our data (Browne et al., 2025). For example, average gross carbonate production on the remote Chagos atolls was 4.1 kg/m²/year in 2021 (Lloyd Newman et al., 2023), in the Maldives it was 5.9 kg/m²/year in 2018 (Ryan et al., 2019) and in Western Australia on Ningaloo reef, rates of 5.23 kg/m²/year were recorded (Perry et al., 2018). Since 2002, gross carbonate production rates on Heron Reef have increased over time despite numerous acute disturbance events, except for a sharp decline in 2024. These disturbances included outbreaks of coral diseases (2004-2008) (Haapkylä et al., 2010; Roff et al., 2011), extreme weather events (2019) (Mellin et al., 2019), and coral bleaching (2016, 2017, 2024) (Hughes et al., 2017; Henley et al., 2024). The most significant declines in coral cover (and therefore carbonate production) occurred in 2018 and 2024, when gross carbonate production declined by 24% and 43%, respectively, and were likely due to bleaching. However, the only time during this period when gross carbonate values dropped below the high gross carbonate production values of 10 kg/m²/year was in 2008, after four consecutive years of coral disease outbreaks. Recovery following these events has been rapid, with the most rapid recovery in 2019. Taken together, our data indicated that not only is gross carbonate production on Heron Reef consistently high, but environmental conditions on the reef also facilitated rapid recovery following disturbance events. A reef’s accretionary capacity is the product of both gross carbonate production and erosion (Browne et al., 2021). Our study only tells half the story and, as such, to understand the long-term trajectory of a reef, data on rates of erosion are required (Lange et al., 2020). Brown et al. (2021) completed a net carbonate budget assessment of eight sites across the different reef habitats on Heron Reef. Gross carbonate production values ranged from 15 to 26 kg/m 2 /year on the reef slopes to 2.3 kg/m 2 /year on the reef flat. Our carbonate production rates on the reef flat and slope were comparable to values recorded by Brown et al., in 2015/2016, suggesting that these data sets are compatible. Hence, by applying bioerosion rates measured in Brown et al. (2021), we can estimate net carbonate production values for Heron Reef over 22 years. Gross framework bioerosion rates measured by Brown et al. (2021) were generally low, ranging from 0.19 to 4.11 kg/m 2 /year. However, on average bioerosion was ~2 kg/m 2 /year within the reef slope and flat zones. Bioerosion rates are expected to vary spatially and temporarily (Cornwall et al., 2021). However, since gross carbonate production rates in our study rarely fell below 10 kg/m 2 /year, it suggests that net carbonate production values have consistently remained high over the last 22 years. Additionally, mean gross carbonate production per zone typically exceeded 1-7 kg/m 2 /year, further indicating that all zones, including the less productive reef flats, have remained in a positive reef accretionary state despite several disturbance events. On Heron Reef, coral cover was the primary driver of carbonate production. Among the hard corals, the largest contributor to carbonate production was branching Acropora , followed by tabular Acropora , and Montipora , collectively accounting for 87% of total reef carbonate production. The loss of these genera following a disturbance event considerably reduced gross carbonate production. Genus-specific life history traits provide key insight into temporal trends in carbonate production and reef resilience during disturbance events (Wolff et al., 2018). In cases where recovery was evident, increased carbonate production corresponded to the resurgence of branching Acropora ; a genus characterised by rapid growth but high vulnerability to stressors (Ortiz et al., 2021). This pattern aligns with studies suggesting that reefs dominated by fast-growing species can recover relatively quickly if environmental conditions remain favourable (Reverter et al., 2022). Conversely, slower-growing genera like Montipora tend to be more resistant to stressors (Browne et al., 2019). However, Montipora produce less calcium carbonate, which can slow reef growth and reduce habitat complexity potentially leading to biodiversity loss (Lendo et al., 2024). A shift from high-diversity coral assemblages towards fast-growing, disturbance-prone species could weaken the reef’s ability to recover from future disturbances, making it more vulnerable to long-term decline (Browne et al., 2015). This is evidenced from the 2024 bleaching event, when coral cover decreased by 54%, with Acropora on the reef slopes declining by 47%. As such, it is important to track not only gross carbonate production values, but to identify the key drivers of production over time and within different geomorphic zones to improve our forecasts of stability at a reef scale. Gross Carbonate Production Over Space Our analysis revealed considerable spatial variations in gross carbonate production, driven by differences in coral cover. Carbonate production was more variable on the reef slopes than on the reef flats, primarily because the slope had the highest hard coral cover, and fluctuated more readily than other reef components. Reef slopes provide a more favourable environment for coral growth and recovery, with optimal light availability and more stable temperatures compared to reef flats (Roelfsema et al., 2021b). Yet, even within reef slope environments, there are important environmental differences influencing coral composition. In a previous carbonate budget study at Heron Reef, the authors found the southern reef slope had higher gross carbonate production (~25 kg/m 2 /year) when compared to the northern reef slope (~17 kg/m 2 /year; Brown et al. (2021)). We estimated the same trend here, with mean gross carbonate production values of 10 and 8 kg/m 2 /year in 2021 for the southern and northern slope, respectively. This trend is likely due to the sheltered environment and higher concentration of branching Acropora corals on the southern slope (Vercelloni et al., 2023). In contrast, the northern reef slope was dominated by plating Acropora and Montipora and thus had a lower gross carbonate production. However, these zones also experienced the sharpest declines following disturbances, as Acropora -dominated communities are vulnerable to stressors such as coral disease and bleaching, and extreme weather events (Ortiz et al., 2021). This aligns with previous studies showing the disproportionate impact of disease and bleaching on Acropora communities (Roff et al., 2011; Henley et al., 2024). Most gross carbonate production on tropical reefs is generated by hard corals, although CCA in some reef settings have been shown to provide up to 18% of total gross carbonate (Cornwall et al., 2023). At Heron reef, CCA typically remained <1%, but increased in all four zones over the course of the study. However, the authors suspect this to be an under-representation of true CCA contributions to the gross carbonate budget due to the method of data collection used here. Most carbonate budgets employed over the last 20 years use in-situ data collection technique along transects (Perry et al., 2012), which allows for the observation of cryptic cover (e.g., on vertical angles) and is therefore more likely to note CCA cover and better quantify its contribution to gross carbonate production (Browne et al., 2025). Another algal contributor to reef carbonates, which also increased in cover over the study period, is Halimeda , which can contribute significant amounts of material to reef sediments and framework infilling (Rees et al., 2007). The observed increases in Halimeda and CCA on the reef slope may reflect a stabilising influence, providing a potential “backup” carbonate source in areas where coral cover is in decline. In contrast to the reef slopes, the inner and outer reef flats had consistently low coral cover, likely due to greater exposure to physical stress through tide and temperature differences (Roelfsema et al., 2021b). Turf algae/DHC and sand cover fluctuated over time, often inversely related to coral cover, suggesting that shifts in benthic composition were driven by disturbance-recovery cycles, and space availability (Fine et al., 2019). Despite lower coral cover and gross carbonate production, key sources of carbonate were still branching and tabular Acropora, and Montipora , with greater cover and production on the outer compared to the inner reef flat. Lower coral cover in inner reef flats is not unusual (Bellwood et al., 2018), previously attributed to higher temperatures and sand scouring (Albright et al., 2013). In more recent years, Halimeda cover increased across both reef flats from 0 to 1%. Potential reasons for the increase in Halimeda cover could relate to changes in coral composition (Brown et al., 2020). Halimeda prefer growing within branching Acropora, where they are protected from predation and strong currents (Castro-Sanguino et al., 2020). We observed that higher branching coral cover on the reef flats coincided with increased Halimeda cover. Despite spatial and temporal variations in carbonate production, our data suggests that Heron Reef is a resilient reef system. Previous studies on coral recovery indicate that it can take approximately four years after a disturbance for recovery to begin, followed by a gradual increase of 1-2% in coral cover per year (Vercelloni et al., 2023). The probability of recovery varies across coral genera, and across geomorphic zones (Vercelloni et al., 2017). However, coral cover on Heron Reef rebounded at approximately 5% per year, typically returning to pre-disturbance coral cover by four years. Recovery was notably faster on the southern slope than the northern slope, likely due to more sheltered conditions that facilitate coral establishment and growth, as well as the dominance of branching corals, which have been shown to rapidly recover (Roelfsema et al., 2021b; Vercelloni et al., 2023). Although carbonate production rates nearly halved from 2023 to 2024 in response to the widespread bleaching and substantial declines in coral cover across all geomorphic zones, production remained just above the high production threshold of 10 kg CaCO₃/m²/year, underscoring the severity of the event while highlighting the system's limited but persistent capacity for carbonate accumulation. Our findings emphasised that different geomorphic zones uniquely contribute to overall reef carbonate production, indicating that extrapolating data from a single zone can lead to significant misrepresentations (Hart and Kench, 2007; Browne et al., 2013). For example, relying solely on reef flat data could underestimate production, while exclusive use of reef slope data might result in overestimation (Perry et al., 2012). Many previous carbonate production studies have focused on reef flats due to their accessibility, but this underrepresents actual carbonate states when extrapolated across the entire reef, especially when there is high coral cover on the reef slopes (Lange et al., 2020). By capturing the full reef geomorphic variation, our approach revealed differences in gross carbonate production between reef flats and slopes that have been overlooked in prior studies, likely leading to a more accurate representation of gross carbonate production over time. Management Implications Understanding the patterns and drivers of carbonate production over time provides essential insights into reef resilience. As carbonate budgets capture various aspects of reef ecology (i.e., abundance, composition and productivity), these budgets can provide important insights into reef resilience, particularly when conducted across multiple sites and years. Previous studies have identified hard corals as the key drivers of both gross and net carbonate production (Januchowski-Hartley et al., 2017). Therefore, studies focusing on spatial and temporal changes in coral cover alone can still provide important insights into the net carbonate budget. We encourage researchers with access to long-term coral cover data to calculate gross and net carbonate production rates using published coral growth rates (as per Perry et al. (2012)) to further understand reef accretionary state and resilience. Studies on gross carbonate production facilitate the identification of key coral genera and geomorphic zones that could be targeted for protection and/or restoration efforts (Lendo et al., 2024). For example, at Heron Reef, the importance of fast-growing Acropora for rapid recovery is evident. However, reefs dominated by a limited coral species may become more susceptible to future disturbance regimes. Combining fast-growing corals with more disturbance-resistant genera, such as Montipora , can occupy complementary niches and enhance ecological stability (Ortiz et al., 2021). Thus, our carbonate production findings emphasise the need for multi-species restoration initiatives. Moreover, the observed differences in carbonate production across geomorphic zones underscores the need for zone-specific conservation strategies. Since reef slopes contribute the most to carbonate production, their protection should be a management priority to maintain reef framework integrity. Future Research Future research should integrate advanced remote sensing and machine learning techniques to enhance monitoring capabilities and expand the spatial coverage for calculating carbonate estimates (Lange et al., 2024; Pilly et al., 2025). Additionally, research should aim to address gaps in our understanding of reef carbonate budgets. An important knowledge gap (as outlined in Browne et al. (2021)), is accurate assessments of bioerosion dynamics over time and space, which is required to construct complete carbonate budgets. The authors acknowledge that accurate assessments of bioerosion are more complex than those for gross carbonate production and may require novel methodological approaches. It is also critical to investigate the implications of live coral mortality and associated reef rubble formation on carbonate budgets, particularly following major cyclone and bleaching events. For example, if live coral is replaced by dead coral or rubble due to continued disturbances, gross carbonate production values may significantly decline due to both reduced live coral cover and decreased successful coral recruitment due to a less stable reef benthos (Lendo et al., 2024). Conclusion This study provided a unique timeseries analysis of gross carbonate production across different geomorphic zones. Carbonate production on Heron Reef was high compared to other Indo-Pacific reefs, showing a general increase in gross production over time despite multiple disturbance events. Following a 40% increase between 2010 and 2023, the 2024 bleaching event caused a 25% decrease in coral cover, which will directly impact carbonate production. The southern reef slope exhibited the highest gross production rates, primarily driven by branching and tabular Acropora and Montipora . These findings highlight the importance of structurally complex coral assemblages in maintaining positive carbonate production states and enhancing reef resilience, while also providing critical habitats for other organisms. Across the study period, repeated environmental disturbances—most recently the 2024 bleaching event—drove significant declines in coral cover and carbonate production. Despite these pressures, carbonate production mostly remained just above the critical threshold of 10 kg CaCO₃/m²/year, reflecting both the ongoing vulnerability and underlying resilience of the reef system. Although Heron Reef has historically recovered from disturbance events, it is likely to face increased frequency and/or severity of such events in the future. By identifying key contributors to carbonate budgets, this study offered valuable insights for reef management, emphasising the need to protect high-production coral groups and geomorphic zones. Future research should expand to include assessments of bioerosion processes and improve the spatial coverage of carbonate estimates to provide a more comprehensive understanding of reef accretionary states amid escalating environmental pressures Declarations Conflict of interest On behalf of all authors, the corresponding author states that there is no conflict of interest. Funding Funding was provided by the University of Queensland (UQ); the Global Change Institute at UQ; the Commonwealth Scientific and Industrial Research Organisation; the Australian Research Council (ARC) Laureate Fellowship to Professor Ove Hoegh-Guldberg; the ARC Linkage Grant to Prof. J Marshall and Prof. S Phinn; World Bank Global Environment Fund; ARC Linkage Innovative Coral Reef Monitoring; the Allen Coral Atlas; Australian Lotto; the Great Barrier Reef Foundation; SmartSat; and the Great Barrier Marine Park Authority. Author Contribution N.K.B. and C.M.R. supervised the project. F.D., N.K.B., and C.M.R. designed the study. J.V. provided assistance with statistical methodologies and preparing the scripts for figures. F.D., N.K.B., D.E.C.R., E.K., K.M., and C.M.R processed the data. F.D., N.K.B., D.E.C.R., N.M.H., and C.M.R. all worked on the analysis and interpretation of results, and wrote the manuscript text. C.R. acquired all funding. All authors provided input on and reviewed the manuscript. Acknowledgement We acknowledge the traditional owners of Heron Reef Sea country, the Bailai, Gurang, Gooreng, and Taribelang peoples, on whose land we conduct fieldwork with their consent. We express our respect for their Elders past, present and emerging. Fieldwork support was provided by CoralWatch, Reef Check Volunteers, and staff and students at UQ and Heron Island Research Station. 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This is overlayed on a Planet Dove satellite image from the 30\u003c/em\u003e\u003csup\u003e\u003cem\u003eth \u003c/em\u003e\u003c/sup\u003e\u003cem\u003eof October 2022.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/e7928d292fafd163f38ab7e5.png"},{"id":84081291,"identity":"cb36e3c8-8ddd-486f-84c7-30473f771aca","added_by":"auto","created_at":"2025-06-06 14:14:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":342151,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ePercentage benthic cover for each geomorphic zone over time: (a) Inner reef flat, (b) Outer reef flat, (c) Northern reef slope, and (d) Southern reef slope. Dashed lines denote disturbance events, and symbols represent disease outbreaks, bleaching events, and storms (from left to right). Error bars show SE.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/2f0a9e75b7a0d579a8d0869c.png"},{"id":84081293,"identity":"ba370cc4-116c-459a-bcee-f68fb4283911","added_by":"auto","created_at":"2025-06-06 14:14:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":352327,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ePercentage coral genera/taxon cover over time for each geomorphic zone of Heron Reef: (a) Inner reef flat, (b) Outer reef flat, (c) Northern reef slope, and (d) Southern reef slope. Error bars show SE.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/6a0980e7f31e335ec63f494f.png"},{"id":84080686,"identity":"0ef5a765-bbfc-4282-bb44-b5ff4c66a34e","added_by":"auto","created_at":"2025-06-06 14:06:55","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":249881,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ePercentage algal cover over time for each geomorphic zone of Heron Reef: (a) Inner reef flat, (b) Outer reef flat, (c) Northern reef slope, and (d) Southern reef slope. Error bars show SE.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/c272e8e69af4feb1f2502c5c.png"},{"id":84080688,"identity":"0f8dd0ca-9027-46bf-b1ba-d38b54df7419","added_by":"auto","created_at":"2025-06-06 14:06:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":190440,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eGross carbonate production across Heron Reef, pooling all geomorphic zones over time to display total reef production, as well as that of the three dominant carbonate-producing coral groups. Dashed lines denote disturbance events, and symbols represent disease outbreaks, bleaching events, and storms (from left to right). Error bars represent standard error (SE).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/75bd42c5f87535a696da204d.png"},{"id":84080695,"identity":"497444c5-0e52-4afe-ba73-a2887437ce83","added_by":"auto","created_at":"2025-06-06 14:06:55","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":167377,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eHeat maps depicting normalised carbonate production (total mass carbonate normalised by area), showing darker colours for higher values across Heron Reef’s geomorphic zones.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/c20b2cb2ead6cce1dd4b12f1.png"},{"id":90345042,"identity":"7b2b9662-dc02-4221-9cd9-19fdc2350ffe","added_by":"auto","created_at":"2025-09-01 16:09:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3030660,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/47b16a07-2964-4da9-ac90-068c18904751.pdf"},{"id":84081903,"identity":"d3a59aa9-fc0a-4959-8919-b8b337b4e7ed","added_by":"auto","created_at":"2025-06-06 14:22:55","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":168752,"visible":true,"origin":"","legend":"","description":"","filename":"Appendices.docx","url":"https://assets-eu.researchsquare.com/files/rs-6668724/v1/ad6fe128a2daff06b20eca67.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Two decades of coral carbonate production within and across geomorphic zones","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRecent studies suggest that reef resilience and functioning is declining (Tebbett et al., 2023) and, as such, reefs are struggling to recover from cumulative impacts such as climate change (Wilkinson, 2006), pollution (Bartley et al., 2014), and over-exploitation (Wolff et al., 2018). Resilience is a crucial concept in ecosystem management, defined as an ecosystem\u0026rsquo;s capacity to absorb disturbances and adapt to change while maintaining ecosystem functions (Unsworth et al., 2015). Repetitive disturbances result in significant reductions in coral cover, biodiversity, and reef-building capacity (De\u0026apos;ath et al., 2012). For example, the Great Barrier Reef (GBR), despite being one of the most well-managed coral reef systems (Hughes et al., 2017), has experienced decreased resilience to repetitive disturbance, as evidenced from significant reductions in coral cover since the 1990s (De\u0026apos;ath et al., 2012). Coral composition is also changing as disturbances and global climate change lower diversity and shift assemblages to more stress-tolerant, slow-growing species (Mellin et al., 2019). Since the 1980s, the GBR has experienced eight mass bleaching events, resulting in declining coral cover as well as decreased rates of coral recruitment, both of which limit capacity for recovery and increase vulnerability to future disturbances (Henley et al., 2024). As climate change exacerbates these stressors, understanding reef resilience across spatial and temporal scales is crucial. Large-scale field datasets that monitor coral reef health are essential for protecting and managing reef health through repetitive disturbances (Souter et al., 2021; Tebbett et al., 2023). Key metrics for assessing reef resilience include coral abundance, community composition, and reef carbonate production (Perry et al., 2018). While these metrics are essential to understanding reef resilience, our study uniquely highlighted the role of carbonate production across time and space, offering a new perspective in resilience assessments.\u003c/p\u003e\n\u003cp\u003eCarbonate production reflects coral growth and productivity, and is a key indicator of long-term reef structure viability (Januchowski-Hartley et al., 2017). Coral reef growth relies on a positive balance between gross calcium carbonate (CaCO₃) production and erosion (Uthicke et al., 2014). This \u0026quot;carbonate budget\u0026quot; requires CaCO₃ production rates from corals and crustose coralline algae (CCA) to exceed erosion rates to maintain or increase reef structure (Brown et al., 2020). The quantification of CaCO₃ production can provide crucial insights into the reef\u0026rsquo;s long-term stability and, therefore, resilience (Chave et al., 1972; Contreras-Silva et al., 2020). Recently, the application of the carbonate budget method has become increasingly popular for assessing reef resilience, by quantifying the impact of disturbance events and tracking carbonate production over several years (Ryan et al., 2019). For example, carbonate budgets have been used to evaluate the impact of bleaching events, storm damage, and anthropogenic stressors on coral cover and composition, and how these changes translate to net carbonate production and long-term reef stability (Lange et al., 2020). Such an approach integrates traditional benthic assessments with productivity data, thereby offering insights into reef productivity and resilience beyond standard in-water assessments (Browne et al., 2021).\u003c/p\u003e\n\u003cp\u003eHowever, as with most methodologies, limitations exist when assessing carbonate budgets both spatially and temporally. One of the key limitations of carbonate budgets relates to the scale of application. Typically, data for carbonate budgets are collected along a small number of transects from which data is then extrapolated to cover entire geomorphic zones \u0026nbsp;(Silbiger et al., 2017). This likely oversimplifies spatial variations, thereby missing important within and between zone variations (Perry et al., 2015). Understanding benthic community changes and carbonate production requires examination at the geomorphic scale (Vercelloni et al., 2023), which to date has rarely been conducted in carbonate budget studies (Lange et al., 2020). Variations in carbonate production within geomorphic zones are influenced by depth, disturbance history, and exposure (Brown et al., 2018). To address this issue, carbonate budgets require higher spatial and temporal resolution data sets, as well as the integration of data from multiple sites over extended periods of time (Cornwall et al., 2021). \u0026nbsp;Long-term datasets are critical for identifying historical baselines, tracking trends and predicting future changes in carbonate production. Importantly, such datasets are rare due to time and financial constraints (Reverter et al., 2022).\u003c/p\u003e\n\u003cp\u003eThis study aimed to assess the dynamics of gross carbonate production using benthic community data collected over two decades within and across coral reef geomorphic zones. We utilised the annual benthic dataset from Heron Reef, which offers a 20-year record for over 30 data collection sites across four geomorphic zones (Roelfsema et al., 2021a). This dataset allowed us to explore coral community dynamics and carbonate production during a period of significant environmental change, including chronic stressors and acute disturbances such as disease outbreaks (2004-2008) (Haapkyl\u0026auml; et al., 2010; Roff et al., 2011), extreme weather events (2019) (Mellin et al., 2019), and coral bleaching (2016, 2017, 2024) (Hughes et al., 2017; Henley et al., 2024). Therefore, the objectives of this paper were: (1) to evaluate the benthic composition over time and space; (2) to identify the community driving carbonate production over time; (3) to examine spatial variations in carbonate production across geomorphic zones; and (4) to explore the potential implications of these changes for management and conservation. This comprehensive analysis provided new insights into the short-term recovery potential and long-term stability of coral reefs such as Heron Reef.\u003c/p\u003e"},{"header":"Methods","content":"\u003ch2\u003eStudy Site\u003c/h2\u003e\n\u003cp\u003eHeron Reef, located in the Capricorn-Bunker group on the southern GBR (23.4425\u0026deg; S, 151.9144\u0026deg; E), was chosen for its unique benthic dataset. The reef is divided into four geomorphic zones: inner and outer reef flats, as well as northern and southern reef slopes (Phinn et al., 2012). The northern reef slope experiences higher wave intensity compared to the southern slope, which is typically sheltered. Slope data was collected at 4-7 m depth (Roelfsema et al., 2021b), whereas reef flat data was collected at 0-2 m depth. These geomorphic zones offer unique benthic characteristics, providing valuable data for studying reef carbonate dynamics (Vercelloni et al., 2023; Carrasco Rivera et al., 2025). The middle lagoon area was excluded, due to lack of data points and low coral cover.\u003c/p\u003e\n\u003ch2\u003eBenthic Composition Over Space and Time\u003c/h2\u003e\n\u003cp\u003eBenthic composition data collection and analysis has previously been described in detail by Roelfsema et al. (2021a) and Vercelloni et al. (2023). In short, from 2002 to 2024 (excluding 2003 and 2004), georeferenced photo quadrats were taken annually at 2-3 m intervals along stratified random transects across Heron Reef. Each quadrat represents a 1 x 1 m area and transects were positioned to capture representative habitats across and within geomorphic zones. Transects within each geomorphic zone were defined as hexagons (100 m\u003csup\u003e2\u003c/sup\u003e) surveyed each year, generated using hierarchal clustering based on Euclidean distances between geo-located photo quadrats (Vercelloni et al., 2023).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBenthic community composition in photo quadrats were analysed using CoralNet (2002-2018) (Gonz\u0026aacute;lez-Rivero et al., 2020) and ReefCloud (2019-2024) ((AIMS), 2024) machine learning algorithms. An associated label set (Appendix A) was used for annotating photo quadrats, as determined by Roelfsema et al. (2021a). This resulted in the identification of coral cover down to family and/or genus level. Here, plate/encrusting \u003cem\u003eAcroporidae\u003c/em\u003e corals were merged as the software was not able to distinguish between them. Dead hard coral (DHC) was classified as \u0026ldquo;turf algae/DHC\u0026rdquo; due to the widespread presence of algae on it, and all algae that did not fit an established label were classified as \u0026ldquo;Algae Other\u0026rdquo;. CCA and \u003cem\u003eHalimeda\u003c/em\u003e can often be important sources of carbonate production on reefs, and hence their specific abundance was recorded. For all benthic communities, annual percentage cover was calculated per geomorphic zone by attributing all transects to their associated zone(s) and divided by the total area of each zone to compare them on the same scale.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eCarbonate Production Over Space and Time\u003c/h2\u003e\n\u003cp\u003eGross carbonate production was calculated using a multi-step process. Planimetric area provided a measure of size of the coral habitat (m\u003csup\u003e2\u003c/sup\u003e), which was then adjusted by a rugosity factor (Table 1, equation 1). Rugosity is a measure of the complexity of the reef structure and plays a crucial role in accurately estimating carbonate production rates. Given that no in-situ data for rugosity was available, we developed a proxy measurement using total hard coral cover data. Specifically, we applied the software WebPlotDigitizer to estimate rugosity values based on reconstructed trajectories of percentage coral cover and reef rugosity from Bozec et al. (2015) \u0026nbsp;(Appendix B). The underlying assumption driving this approach is that as coral cover increases, it correlates with changes in reef complexity, as reflected by increases in rugosity (Bozec et al., 2015).\u003c/p\u003e\n\u003cp\u003eArea covered (cm\u003csup\u003e2\u003c/sup\u003e) by calcifiers was determined by multiplying the calcifier average percentage cover by zone habitat area, as previously calculated (m\u003csup\u003e2\u003c/sup\u003e; Equation 2). Calcification rates for hard corals were sourced from literature (Appendix C), incorporating factors like linear extension and carbonate density (Equation 3) (Dove et al., 2020). Different rates were applied per zone to account for environmental variability (Appendix C) (D\u0026apos;Olivo et al., 2013). A conversion factor was used to adjust for volumetric growth, and aid in quantifying adjusted carbonate production over time (Equation 4) (Silbiger et al., 2017). Subsequently, total mass carbonate (kg/year) was calculated by multiplying the adjusted calcification rate by the area occupied, (Equation 5). This value was then normalised by dividing the total mass carbonate by zone habitat area (Equation 6). Finally, to determine gross carbonate framework production, all normalised coral carbonate production rates were compiled (Equation 7). To determine CCA carbonate production rates, we included parameters related to surface area and coverage, which relates to their distinct growth patterns and calcification mechanisms.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eTable 1\u003c/em\u003e\u003c/strong\u003e\u003cem\u003e: Equations used for calculating metrics of interest, including the relevant variables and their respective units.\u003c/em\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"623\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eEquation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003eUnits\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eEquation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eZone habitat area\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003em\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003ePlanimetric area (m\u003csup\u003e2\u003c/sup\u003e) x rugosity\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eArea occupied\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003ecm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eZone habitat area x (coral % cover / 100) x 10000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eCalcification rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003eg/cm\u003csup\u003e2\u003c/sup\u003e/year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eLinear extension (cm/year) x density (g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eAdjusted calcification rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003eg/cm\u003csup\u003e2\u003c/sup\u003e/year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eCalcification rate(g/cm\u003csup\u003e2\u003c/sup\u003e/year) x conversion factor\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eTotal mass carbonate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003ekg/year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eAdjusted calcification rate (g/cm\u003csup\u003e2\u003c/sup\u003e/year) x area occupied (cm\u003csup\u003e2\u003c/sup\u003e) / 1000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eNormalised coral carbonate production rate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003ekg/m\u003csup\u003e2\u003c/sup\u003e/year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003eTotal mass carbonate (kg/year) / zone habitat area (m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 130px;\"\u003e\n \u003cp\u003eGross carbonate framework production\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 87px;\"\u003e\n \u003cp\u003ekg/m\u003csup\u003e2\u003c/sup\u003e/year\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 331px;\"\u003e\n \u003cp\u003e\u0026sum; Normalised coral carbonate production rate (kg/m\u003csup\u003e2\u003c/sup\u003e/year)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eUsing this multi-step methodology, we assessed total gross annual carbonate production rates to understand both overall spatial trends in reef carbonate production and how it has varied over time. Specifically, we reviewed the spatial variation between reef zones to understand the contribution of different geomorphic zones to carbonate production, and as well as identifying which calcifiers had the greatest inputs. Additionally, we identified temporal trends and key contributors to assess how disturbances, including coral disease outbreaks and bleaching events, have affected the reef\u0026apos;s ability to recover and maintain its carbonate production over time.\u003c/p\u003e"},{"header":"Results","content":"\u003ch2\u003eBenthic Composition Over Space and Time\u003c/h2\u003e\n\u003ch3\u003eDifferences Across Geomorphic Zones\u003c/h3\u003e\n\u003cp\u003eSand dominated the inner reef flat (mean = 53.6%) across the study period. Initially, sand cover was low (27.8% \u0026plusmn; 2.28 SE) in 2002, before increasing to a maximum of 66.3% (\u0026plusmn; 0.09 SE) in 2007 (Figure 2a) after which cover remained relatively stable. Turf algae/DHC cover exhibited an inverse relationship to sand, but generally remained stable, averaging 32.8% across the study period. Turf algae/DHC cover was initially observed to be at 67.2% (\u0026plusmn; 3.73 SE) in 2002, reaching 19.9% (\u0026plusmn; 0.03 SE) in 2007, often increasing in years when sand cover declined. Hard coral cover was consistently low (\u0026lt;10%), but gradually increased over time, peaking in 2019 at 15% (\u0026plusmn; 0.04 SE). On the outer reef flat, turf algae/DHC was the dominant benthic category, which remained relatively stable over time (~75%) except for a decline to 47.1% (\u0026plusmn; 0.03 SE) in 2005 (Figure 2b). Similarly, hard coral cover experienced gradual fluctuations from 12.7% (\u0026plusmn; 0.13 SE) to 14.1% (\u0026plusmn; 0.19 SE) over the same period. Algal cover remained consistently low, ranging between 0.2% and 4.0%, while soft coral cover was negligible (\u0026lt;2%).\u003c/p\u003e\n\u003cp\u003eIn both the northern and southern reef slopes, hard coral cover was considerably higher than on the reef flats (averaging 39.3 and 42.5%, respectively), exhibiting inverse trends with turf algae/DHC (Figure 2c and 2d). On the northern reef slope, hard coral cover decreased from 45.3% (\u0026plusmn; 0.05 SE) in 2002 to 12.9% (\u0026plusmn; 0.07 SE) in 2010, followed by a steady increase of approximately 5% per year, reaching 54.8% (\u0026plusmn; 0.41 SE) in 2023, and then falling to 26.2% (\u0026plusmn; 0.66 SE) in 2024 (Figure 2c). Conversely, turf algae/DHC cover decreased from 48.4% (\u0026plusmn; 0.49 SE) in 2002 to 32% (\u0026plusmn; 0.33 SE) in 2023, before doubling to 64.1% (\u0026plusmn; 0.63 SE) in 2024. Similarly, on the southern slope, hard coral cover increased from 34.8% (\u0026plusmn; 0.86 SE) in 2002 to 48.3% (\u0026plusmn; 0.01 SE) in 2023, dropping again to 32.1% (\u0026plusmn; 0.07 SE) in 2024 (Figure 2d). Turf algae/DHC exhibited an inverse relationship with hard coral, decreasing over time to 44.9% (\u0026plusmn; 0.88 SE) in 2023, and increasing to 61.3% (\u0026plusmn; 0.07 SE) in 2024.\u0026nbsp;\u003c/p\u003e\n\u003ch3\u003eCoral Community Composition\u003c/h3\u003e\n\u003cp\u003eBranching \u003cem\u003eAcropora\u003c/em\u003e was the primary contributor to hard coral cover, followed by \u0026lsquo;Tabulate and Corymbose\u003cem\u003e\u0026nbsp;Acropora\u0026rsquo;\u0026nbsp;\u003c/em\u003e(hereafter referred to as tabular \u003cem\u003eAcropora\u003c/em\u003e) and Plate/ Encrusting \u003cem\u003eAcroporidae\u0026nbsp;\u003c/em\u003e(hereafter referred to as \u003cem\u003eMontipora\u003c/em\u003e) (Figure 3). Each zone exhibited unique trends, with the southern reef slope exhibiting the most fluctuations in branching \u003cem\u003eAcropora\u0026nbsp;\u003c/em\u003e(Figure 3d). On the inner reef flat, branching \u003cem\u003eAcropora\u003c/em\u003e cover rose from 0.1% (\u0026plusmn; 0.01 SE) in 2002 to 3.4% (\u0026plusmn; 0.08 SE) in 2016, before dropping to 1.9% (\u0026plusmn; 0.04 SE) in 2024 (Figure 3a). On the outer reef flat, branching \u003cem\u003eAcropora\u003c/em\u003e fluctuated around 10% cover, dropping to ~5% in 2011, 2015, 2017 and 2024. On the northern reef slope, pre-2007 branching \u003cem\u003eAcropora\u003c/em\u003e was greater than 20%, before declining rapidly from 2008 to 2010 to between 5-10%. Since 2010, cover has gradually increased peaking in 2023 at 26.8% % (\u0026plusmn; 0.04 SE), before declining to 12.7% (\u0026plusmn; 0.05 SE) in 2024. (Figure 3c). The southern reef slope experienced marked fluctuations in branching \u003cem\u003eAcropora\u0026nbsp;\u003c/em\u003eas well, with cover dropping sharply from 35.7 (\u0026plusmn; 0.45 SE) in 2005 to 1.2% (\u0026plusmn; 0.02 SE) in 2008, peaking at 39% (\u0026plusmn; 0.25 SE) in 2013, then gradually decreasing to 33.7% (\u0026plusmn; 0.13 SE) by 2023 (Figure 3d). In 2024, branching \u003cem\u003eAcropora\u0026nbsp;\u003c/em\u003ecover\u003cem\u003e\u0026nbsp;\u003c/em\u003efell to 25% (\u0026plusmn; 0.13 SE).\u003c/p\u003e\n\u003cp\u003eTabular \u003cem\u003eAcropora\u003c/em\u003e and \u003cem\u003eMontipora\u003c/em\u003e showed less variability. On the inner reef flat, tabular \u003cem\u003eAcropora\u003c/em\u003e increased from 0.72% (\u0026plusmn; 0.12 SE) in 2002 to 1.4% (\u0026plusmn; 0.01 SE) in 2016, then declined to 0.7% (\u0026plusmn; 0.02 SE) by 2024 (Figure 3a). Northern reef slope tabular \u003cem\u003eAcropora\u003c/em\u003e and \u003cem\u003eMontipora\u003c/em\u003e cover increased from 11.1% (\u0026plusmn;0.61 SE) in 2002 to 18.3% (\u0026plusmn; 0.04 SE) by 2023 but then dropped to 9.7% (\u0026plusmn; 0.02 SE) in 2024 (Figure 3c). On the southern reef slope, tabular \u003cem\u003eAcropora\u003c/em\u003e and \u003cem\u003eMontipora\u003c/em\u003e cover fell from 19.8% (\u0026plusmn; 0.65 SE) in 2002 to 1.8% (\u0026plusmn; 0.17 SE) in 2006, then rose to 6% (\u0026plusmn; 0.62 SE) by 2023, and dropped further to 2.8% (\u0026plusmn; 0.02 SE) in 2024 (Figure 3d). \u003cem\u003eMontipora\u003c/em\u003e, the third-largest group, showed distinct trends: northern reef slope cover decreased from 9.1% (\u0026plusmn; 0.18 SE) in 2002 to 5.6% (\u0026plusmn; 0.06 SE) in 2023, and dropped to 1.6% (\u0026plusmn; 0.01 SE) in 2024 (Figure 3c). On the southern reef slope\u003cem\u003e,\u003c/em\u003e \u003cem\u003eMontipora\u003c/em\u003e rose from 2.3% (\u0026plusmn; 0.3 SE) in 2002 to 4.3% (\u0026plusmn; 0.23 SE) in 2023, but then halved to 2% (\u0026plusmn; 0.01 SE) in 2024 (Figure 3d).\u003c/p\u003e\n\u003ch3\u003eAlgal Community Composition\u003c/h3\u003e\n\u003cp\u003eDominant algal groups on Heron Reef consisted of \u003cem\u003eHalimeda,\u003c/em\u003e \u0026apos;Algae Other\u0026rsquo;, and CCA (Figure 4). On the northern reef slope, \u003cem\u003eHalimeda\u003c/em\u003e increased over time, from 0.1% (\u0026plusmn; 0.01 SE) in 2002, to 5.1% (\u0026plusmn; 0.01 SE) in 2024 (Figure 4c). CCA increased from 0.1% (\u0026plusmn; 0.12 SE) in 2002 to 4.4% (\u0026plusmn; 0.14 SE) in 2024. Other algal cover was generally low, remaining under 3%, although there were some observable fluctuations in \u0026apos;Algae Other.\u0026apos; For instance, on the inner reef flat, \u0026apos;Algae Other\u0026apos; cover rose from 0.5% (\u0026plusmn; 0.13 SE) in 2002 to 7.8% (\u0026plusmn; 0.29 SE) in 2007, before gradually decreasing to 0.8% (\u0026plusmn; 0.07 SE) by 2023 (Figure 4a). A similar increase was observed on the outer reef flat, with \u0026lsquo;Algae Other\u0026rsquo; peaking at 2.5% (\u0026plusmn; 1.67 SE) in 2007 and then declining to 1.2% (\u0026plusmn; 0.04 SE) in 2024 (Figure 4b).\u003c/p\u003e\n\u003ch2\u003eCarbonate Production Over Space and Time\u003c/h2\u003e\n\u003ch3\u003eTotal Gross Annual Carbonate Production\u003c/h3\u003e\n\u003cp\u003eDuring the study period, average total gross annual carbonate production displayed significant variations (Figure 5). From 2002 to 2005, reef carbonate production rose from 15.8 kg/m\u0026sup2;/year (\u0026plusmn; 0.08 SE) to 20.1 kg/m\u0026sup2;/year (\u0026plusmn; 0.11 SE), driven primarily by branching \u003cem\u003eAcropora\u003c/em\u003e, tabular \u003cem\u003eAcropora\u003c/em\u003e, and \u003cem\u003eMontipora\u003c/em\u003e, especially on the reef slopes. However, in 2008, carbonate production dropped to 9.2 kg/m\u0026sup2;/year (\u0026plusmn; 0.05 SE). From 2008 to 2015, production rebounded at a rate of approximately 3 kg/m\u0026sup2;/year, driven largely by the rapid recovery of branching \u003cem\u003eAcropora.\u003c/em\u003e A decline in carbonate production in 2018 followed the bleaching events of 2016 and 2017, but the reef recovered relatively rapidly, reaching a peak production of 22 kg/m\u0026sup2;/year (\u0026plusmn; 0.11 SE) by 2023, but then dropped to 14 kg/m\u0026sup2;/year (\u0026plusmn; 0.07 SE) in 2024 following the mass bleaching event.\u003c/p\u003e\n\u003ch3\u003eDifferences Across Geomorphic Zones\u003c/h3\u003e\n\u003cp\u003eThe northern reef slope was the most productive zone (Figure 6), dominated by branching \u003cem\u003eAcropora\u003c/em\u003e, \u003cem\u003eMontipora\u003c/em\u003e, and tabular \u003cem\u003eAcropora\u003c/em\u003e. In this area, branching \u003cem\u003eAcropora\u003c/em\u003e contributed an average of 3.34 kg/m\u0026sup2;/year (\u0026plusmn; 0.21 SE), while \u003cem\u003eMontipora\u003c/em\u003e and tabular \u003cem\u003eAcropora\u003c/em\u003e contributed 2.76 kg/m\u0026sup2;/year (\u0026plusmn; 0.18 SE) and 1.89 kg/m\u0026sup2;/year (\u0026plusmn; 0.15 SE), respectively. The 2017 data showed some singular high values for groups like \u0026lsquo;massive other\u0026rsquo; (1.12 \u0026plusmn; 0.11 SE), encrusting \u003cem\u003ePorites\u003c/em\u003e (1.05 \u0026plusmn; 0.1 SE), \u003cem\u003ePocillopora\u003c/em\u003e (1.01 \u0026plusmn; 0.09 SE), and \u0026lsquo;plate other\u0026rsquo; (0.78 \u0026plusmn; 0.03 SE). In contrast, the southern reef slope was dominated by branching \u003cem\u003eAcropora\u003c/em\u003e, contributing an average of 4.55 kg/m\u0026sup2;/year (\u0026plusmn; 0.23 SE), followed by \u003cem\u003eMontipora\u003c/em\u003e at 0.88 kg/m\u0026sup2;/year (\u0026plusmn; 0.17 SE) (Figure 6d).\u003c/p\u003e\n\u003cp\u003eThe reef flats had lower carbonate production, with the outer reef flat being more productive than the inner reef flat due to more branching \u003cem\u003eAcropora\u0026nbsp;\u003c/em\u003e(Figures 6a and b). Carbonate production was increased slightly in the inner reef flat by the contribution of \u0026lsquo;Algae Other\u0026rsquo;, whereas the production on the reef slope was raised by increases in key algae such as \u003cem\u003eHalimeda\u003c/em\u003e and CCA. Over the course of the study, significant contributors on the inner reef flat included branching \u003cem\u003eAcropora\u003c/em\u003e (0.98 \u0026plusmn; 0.18 SE), and \u003cem\u003ePocillopora\u003c/em\u003e (0.51 \u0026plusmn; 0.11 SE). The outer reef flat had key contributors such as branching \u003cem\u003eAcropora\u003c/em\u003e (2.11 \u0026plusmn; 0.41 SE), \u003cem\u003eMontipora\u003c/em\u003e (1.15 \u0026plusmn; 0.21 SE), and tabular \u003cem\u003eAcropora\u003c/em\u003e (0.99 \u0026plusmn; 0.08 SE).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study provided a multi-decadal and high-resolution assessment of carbonate production, derived from benthic community dynamics. Spatially, our findings demonstrated distinct differences in gross carbonate production across four geomorphic zones (inner and outer reef flat, northern and southern reef slope). Differences in gross carbonate production were driven by coral cover and benthic composition, while temporal changes in gross carbonate production likely resulted from benthic community responses to acute disturbances such as disease outbreaks, thermal stress, and extreme weather events. Importantly, our approach demonstrated the long-term implications of disturbance events on a reef\u0026rsquo;s carbonate production potential and stability.\u003c/p\u003e\n\u003ch2\u003eBenthic Composition over Space and Time\u003c/h2\u003e\n\u003cp\u003eOur analysis revealed strong spatial and temporal variability in benthic composition across Heron Reef, shaped by both geomorphic setting and disturbance history. Hard coral cover was consistently higher on the reef slopes compared to the flats, with the southern slope showing the highest overall values and most pronounced fluctuations\u0026mdash;largely driven by the dominance and instability of branching \u003cem\u003eAcropora\u003c/em\u003e. In contrast, reef flats were dominated by sand and turf algae/DHC, with limited coral cover and minimal recovery across the study period. A marked decline in hard coral cover and corresponding rise in turf algae/DHC in 2024\u0026mdash;particularly on the slopes\u0026mdash;suggests acute sensitivity to the recent bleaching event (Nyberg and Wright, 2024). Notably, branching and tabular \u003cem\u003eAcropora\u003c/em\u003e, key contributors to reef accretion potential, experienced substantial post-disturbance declines. The increase in CCA and \u003cem\u003eHalimeda\u003c/em\u003e on the northern slope over time may indicate a shift in the reef\u0026apos;s calcifying community, with implications for carbonate production dynamics (Kennedy et al., 2017). These spatial patterns highlight the importance of accounting for geomorphic context when assessing reef condition, resilience, and contributions to carbonate budgets (Cornwall et al., 2021).\u003c/p\u003e\n\u003ch2\u003eGross Carbonate Production Over Time\u003c/h2\u003e\n\u003cp\u003eOn average, annual gross carbonate production rates on Heron Reef were 18.45 kg CaCO₃/m\u0026sup2;/year, which is high compared to many other clearwater reefs in the Indo-Pacific. Our values are also potentially more accurate compared to previous studies, due to the fine spatial scale of our data (Browne et al., 2025). For example, average gross carbonate production on the remote Chagos atolls was 4.1 kg/m\u0026sup2;/year in 2021 (Lloyd Newman et al., 2023), in the Maldives it was 5.9 kg/m\u0026sup2;/year in 2018 (Ryan et al., 2019) and in Western Australia on Ningaloo reef, rates of 5.23 kg/m\u0026sup2;/year were recorded (Perry et al., 2018). Since 2002, gross carbonate production rates on Heron Reef have increased over time despite numerous acute disturbance events, except for a sharp decline in 2024. These disturbances included outbreaks of coral diseases (2004-2008) (Haapkyl\u0026auml; et al., 2010; Roff et al., 2011), extreme weather events (2019) (Mellin et al., 2019), and coral bleaching (2016, 2017, 2024) (Hughes et al., 2017; Henley et al., 2024). The most significant declines in coral cover (and therefore carbonate production) occurred in 2018 and 2024, when gross carbonate production declined by 24% and 43%, respectively, and were likely due to bleaching. However, the only time during this period when gross carbonate values dropped below the high gross carbonate production values of 10 kg/m\u0026sup2;/year was in 2008, after four consecutive years of coral disease outbreaks. Recovery following these events has been rapid, with the most rapid recovery in 2019. Taken together, our data indicated that not only is gross carbonate production on Heron Reef consistently high, but environmental conditions on the reef also facilitated rapid recovery following disturbance events.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA reef\u0026rsquo;s accretionary capacity is the product of both gross carbonate production and erosion (Browne et al., 2021). Our study only tells half the story and, as such, to understand the long-term trajectory of a reef, data on rates of erosion are required (Lange et al., 2020). Brown et al. (2021) completed a net carbonate budget assessment of eight sites across the different reef habitats on Heron Reef. Gross carbonate production values ranged from 15 to 26 kg/m\u003csup\u003e2\u003c/sup\u003e/year on the reef slopes to 2.3 kg/m\u003csup\u003e2\u003c/sup\u003e/year on the reef flat. Our carbonate production rates on the reef flat and slope were comparable to values recorded by Brown et al., in 2015/2016, suggesting that these data sets are compatible. Hence, by applying bioerosion rates measured in Brown et al. (2021), we can estimate net carbonate production values for Heron Reef over 22 years. Gross framework bioerosion rates measured by Brown et al. (2021) were generally low, ranging from 0.19 to 4.11 kg/m\u003csup\u003e2\u003c/sup\u003e/year. However, on average bioerosion was ~2 kg/m\u003csup\u003e2\u003c/sup\u003e/year within the reef slope and flat zones. Bioerosion rates are expected to vary spatially and temporarily (Cornwall et al., 2021). However, since gross carbonate production rates in our study rarely fell below 10 kg/m\u003csup\u003e2\u003c/sup\u003e/year, it suggests that net carbonate production values have consistently remained high over the last 22 years. Additionally, mean gross carbonate production per zone typically exceeded 1-7 kg/m\u003csup\u003e2\u003c/sup\u003e/year, further indicating that all zones, including the less productive reef flats, have remained in a positive reef accretionary state despite several disturbance events.\u003c/p\u003e\n\u003cp\u003eOn Heron Reef, coral cover was the primary driver of carbonate production. Among the hard corals, the largest contributor to carbonate production was branching \u003cem\u003eAcropora\u003c/em\u003e, followed by tabular \u003cem\u003eAcropora\u003c/em\u003e, and \u003cem\u003eMontipora\u003c/em\u003e, collectively accounting for 87% of total reef carbonate production. The loss of these genera following a disturbance event considerably reduced gross carbonate production. Genus-specific life history traits provide key insight into temporal trends in carbonate production and reef resilience during disturbance events (Wolff et al., 2018). In cases where recovery was evident, increased carbonate production corresponded to the resurgence of branching \u003cem\u003eAcropora\u003c/em\u003e; a genus characterised by rapid growth but high vulnerability to stressors (Ortiz et al., 2021). This pattern aligns with studies suggesting that reefs dominated by fast-growing species can recover relatively quickly if environmental conditions remain favourable (Reverter et al., 2022). Conversely, slower-growing genera like \u003cem\u003eMontipora\u003c/em\u003e tend to be more resistant to stressors (Browne et al., 2019). However, \u003cem\u003eMontipora\u003c/em\u003e produce less calcium carbonate, which can slow reef growth and reduce habitat complexity potentially leading to biodiversity loss (Lendo et al., 2024). A shift from high-diversity coral assemblages towards fast-growing, disturbance-prone species could weaken the reef\u0026rsquo;s ability to recover from future disturbances, making it more vulnerable to long-term decline (Browne et al., 2015). This is evidenced from the 2024 bleaching event, when coral cover decreased by 54%, with \u003cem\u003eAcropora\u0026nbsp;\u003c/em\u003eon the reef slopes declining by 47%. As such, it is important to track not only gross carbonate production values, but to identify the key drivers of production over time and within different geomorphic zones to improve our forecasts of stability at a reef scale.\u003c/p\u003e\n\u003ch2\u003eGross Carbonate Production Over Space\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eOur analysis revealed considerable spatial variations in gross carbonate production, driven by differences in coral cover. Carbonate production was more variable on the reef slopes than on the reef flats, primarily because the slope had the highest hard coral cover, and fluctuated more readily than other reef components. Reef slopes provide a more favourable environment for coral growth and recovery, with optimal light availability and more stable temperatures compared to reef flats (Roelfsema et al., 2021b). Yet, even within reef slope environments, there are important environmental differences influencing coral composition. In a previous carbonate budget study at Heron Reef, the authors found the southern reef slope had higher gross carbonate production (~25 kg/m\u003csup\u003e2\u003c/sup\u003e/year) when compared to the northern reef slope (~17 kg/m\u003csup\u003e2\u003c/sup\u003e/year; Brown et al. (2021)). We estimated the same trend here, with mean gross carbonate production values of 10 and 8 kg/m\u003csup\u003e2\u003c/sup\u003e/year in 2021 for the southern and northern slope, respectively. This trend is likely due to the sheltered environment and higher concentration of branching \u003cem\u003eAcropora\u003c/em\u003e corals on the southern slope (Vercelloni et al., 2023). In contrast, the northern reef slope was dominated by plating \u003cem\u003eAcropora\u003c/em\u003e and \u003cem\u003eMontipora\u0026nbsp;\u003c/em\u003eand thus had a lower gross carbonate production. However, these zones also experienced the sharpest declines following disturbances, as \u003cem\u003eAcropora\u003c/em\u003e-dominated communities are vulnerable to stressors such as coral disease and bleaching, and extreme weather events (Ortiz et al., 2021). This aligns with previous studies showing the disproportionate impact of disease and bleaching on \u003cem\u003eAcropora\u003c/em\u003e communities (Roff et al., 2011; Henley et al., 2024). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMost gross carbonate production on tropical reefs is generated by hard corals, although CCA in some reef settings have been shown to provide up to 18% of total gross carbonate (Cornwall et al., 2023). At Heron reef, CCA typically remained \u0026lt;1%, but increased in all four zones over the course of the study. However, the authors suspect this to be an under-representation of true CCA contributions to the gross carbonate budget due to the method of data collection used here. Most carbonate budgets employed over the last 20 years use in-situ data collection technique along transects (Perry et al., 2012), which allows for the observation of cryptic cover (e.g., on vertical angles) and is therefore more likely to note CCA cover and better quantify its contribution to gross carbonate production (Browne et al., 2025). Another algal contributor to reef carbonates, which also increased in cover over the study period, is \u003cem\u003eHalimeda\u003c/em\u003e, which can contribute significant amounts of material to reef sediments and framework infilling (Rees et al., 2007). The observed increases in \u003cem\u003eHalimeda\u003c/em\u003e and CCA on the reef slope may reflect a stabilising influence, providing a potential \u0026ldquo;backup\u0026rdquo; carbonate source in areas where coral cover is in decline.\u003c/p\u003e\n\u003cp\u003eIn contrast to the reef slopes, the inner and outer reef flats had consistently low coral cover, likely due to greater exposure to physical stress through tide and temperature differences (Roelfsema et al., 2021b). Turf algae/DHC and sand cover fluctuated over time, often inversely related to coral cover, suggesting that shifts in benthic composition were driven by disturbance-recovery cycles, and space availability (Fine et al., 2019). Despite lower coral cover and gross carbonate production, key sources of carbonate were still branching and tabular \u003cem\u003eAcropora,\u003c/em\u003e and \u003cem\u003eMontipora\u003c/em\u003e, with greater cover and production on the outer compared to the inner reef flat. Lower coral cover in inner reef flats is not unusual (Bellwood et al., 2018), previously attributed to higher temperatures and sand scouring (Albright et al., 2013). In more recent years, \u003cem\u003eHalimeda\u003c/em\u003e cover increased across both reef flats from 0 to 1%. Potential reasons for the increase in \u003cem\u003eHalimeda\u003c/em\u003e cover could relate to changes in coral composition (Brown et al., 2020). \u003cem\u003eHalimeda\u003c/em\u003e prefer growing within branching \u003cem\u003eAcropora,\u003c/em\u003e where they are protected from predation and strong currents (Castro-Sanguino et al., 2020). We observed that higher branching coral cover on the reef flats coincided with increased \u003cem\u003eHalimeda\u003c/em\u003e cover.\u003c/p\u003e\n\u003cp\u003eDespite spatial and temporal variations in carbonate production, our data suggests that Heron Reef is a resilient reef system. Previous studies on coral recovery indicate that it can take approximately four years after a disturbance for recovery to begin, followed by a gradual increase of 1-2% in coral cover per year (Vercelloni et al., 2023). The probability of recovery varies across coral genera, and across geomorphic zones (Vercelloni et al., 2017). However, coral cover on Heron Reef rebounded at approximately 5% per year, typically returning to pre-disturbance coral cover by four years. Recovery was notably faster on the southern slope than the northern slope, likely due to more sheltered conditions that facilitate coral establishment and growth, as well as the dominance of branching corals, which have been shown to rapidly recover (Roelfsema et al., 2021b; Vercelloni et al., 2023). Although carbonate production rates nearly halved from 2023 to 2024 in response to the widespread bleaching and substantial declines in coral cover across all geomorphic zones, production remained just above the high production threshold of 10 kg CaCO₃/m\u0026sup2;/year, underscoring the severity of the event while highlighting the system\u0026apos;s limited but persistent capacity for carbonate accumulation.\u003c/p\u003e\n\u003cp\u003eOur findings emphasised that different geomorphic zones uniquely contribute to overall reef carbonate production, indicating that extrapolating data from a single zone can lead to significant misrepresentations (Hart and Kench, 2007; Browne et al., 2013). For example, relying solely on reef flat data could underestimate production, while exclusive use of reef slope data might result in overestimation (Perry et al., 2012). Many previous carbonate production studies have focused on reef flats due to their accessibility, but this underrepresents actual carbonate states when extrapolated across the entire reef, especially when there is high coral cover on the reef slopes (Lange et al., 2020). By capturing the full reef geomorphic variation, our approach revealed differences in gross carbonate production between reef flats and slopes that have been overlooked in prior studies, likely leading to a more accurate representation of gross carbonate production over time.\u003c/p\u003e\n\u003ch2\u003eManagement Implications\u003c/h2\u003e\n\u003cp\u003eUnderstanding the patterns and drivers of carbonate production over time provides essential insights into reef resilience. As carbonate budgets capture various aspects of reef ecology (i.e., abundance, composition and productivity), these budgets can provide important insights into reef resilience, particularly when conducted across multiple sites and years. Previous studies have identified hard corals as the key drivers of both gross and net carbonate production (Januchowski-Hartley et al., 2017). Therefore, studies focusing on spatial and temporal changes in coral cover alone can still provide important insights into the net carbonate budget. We encourage researchers with access to long-term coral cover data to calculate gross and net carbonate production rates using published coral growth rates (as per Perry et al. (2012)) to further understand reef accretionary state and resilience.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStudies on gross carbonate production facilitate the identification of key coral genera and geomorphic zones that could be targeted for protection and/or restoration efforts (Lendo et al., 2024). For example, at Heron Reef, the importance of fast-growing \u003cem\u003eAcropora\u003c/em\u003e for rapid recovery is evident. However, reefs dominated by a limited coral species may become more susceptible to future disturbance regimes. Combining fast-growing corals with more disturbance-resistant genera, such as \u003cem\u003eMontipora\u003c/em\u003e, can occupy complementary niches and enhance ecological stability (Ortiz et al., 2021). Thus, our carbonate production findings emphasise the need for multi-species restoration initiatives. Moreover, the observed differences in carbonate production across geomorphic zones underscores the need for zone-specific conservation strategies. Since reef slopes contribute the most to carbonate production, their protection should be a management priority to maintain reef framework integrity.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eFuture Research\u003c/h2\u003e\n\u003cp\u003eFuture research should integrate advanced remote sensing and machine learning techniques to enhance monitoring capabilities and expand the spatial coverage for calculating carbonate estimates (Lange et al., 2024; Pilly et al., 2025). Additionally, research should aim to address gaps in our understanding of reef carbonate budgets. An important knowledge gap (as outlined in Browne et al. (2021)), is accurate assessments of bioerosion dynamics over time and space, which is required to construct complete carbonate budgets. The authors acknowledge that accurate assessments of bioerosion are more complex than those for gross carbonate production and may require novel methodological approaches. It is also critical to investigate the implications of live coral mortality and associated reef rubble formation on carbonate budgets, particularly following major cyclone and bleaching events. For example, if live coral is replaced by dead coral or rubble due to continued disturbances, gross carbonate production values may significantly decline due to both reduced live coral cover and decreased successful coral recruitment due to a less stable reef benthos (Lendo et al., 2024).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study provided a unique timeseries analysis of gross carbonate production across different geomorphic zones. Carbonate production on Heron Reef was high compared to other Indo-Pacific reefs, showing a general increase in gross production over time despite multiple disturbance events. Following a 40% increase between 2010 and 2023, the 2024 bleaching event caused a 25% decrease in coral cover, which will directly impact carbonate production. The southern reef slope exhibited the highest gross production rates, primarily driven by branching and tabular \u003cem\u003eAcropora\u003c/em\u003e and \u003cem\u003eMontipora\u003c/em\u003e. These findings highlight the importance of structurally complex coral assemblages in maintaining positive carbonate production states and enhancing reef resilience, while also providing critical habitats for other organisms. Across the study period, repeated environmental disturbances\u0026mdash;most recently the 2024 bleaching event\u0026mdash;drove significant declines in coral cover and carbonate production. Despite these pressures, carbonate production mostly remained just above the critical threshold of 10 kg CaCO₃/m\u0026sup2;/year, reflecting both the ongoing vulnerability and underlying resilience of the reef system. Although Heron Reef has historically recovered from disturbance events, it is likely to face increased frequency and/or severity of such events in the future. By identifying key contributors to carbonate budgets, this study offered valuable insights for reef management, emphasising the need to protect high-production coral groups and geomorphic zones. Future research should expand to include assessments of bioerosion processes and improve the spatial coverage of carbonate estimates to provide a more comprehensive understanding of reef accretionary states amid escalating environmental pressures\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of interest\u003c/h2\u003e\n\u003cp\u003eOn behalf of all authors, the corresponding author states that there is no conflict of interest.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eFunding was provided by the University of Queensland (UQ); the Global Change Institute at UQ; the Commonwealth Scientific and Industrial Research Organisation; the Australian Research Council (ARC) Laureate Fellowship to Professor Ove Hoegh-Guldberg; the ARC Linkage Grant to Prof. J Marshall and Prof. S Phinn; World Bank Global Environment Fund; ARC Linkage Innovative Coral Reef Monitoring; the Allen Coral Atlas; Australian Lotto; the Great Barrier Reef Foundation; SmartSat; and the Great Barrier Marine Park Authority.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eN.K.B. and C.M.R. supervised the project. F.D., N.K.B., and C.M.R. designed the study. J.V. provided assistance with statistical methodologies and preparing the scripts for figures. F.D., N.K.B., D.E.C.R., E.K., K.M., and C.M.R processed the data. F.D., N.K.B., D.E.C.R., N.M.H., and C.M.R. all worked on the analysis and interpretation of results, and wrote the manuscript text. C.R. acquired all funding. All authors provided input on and reviewed the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe acknowledge the traditional owners of Heron Reef Sea country, the Bailai, Gurang, Gooreng, and Taribelang peoples, on whose land we conduct fieldwork with their consent. We express our respect for their Elders past, present and emerging. Fieldwork support was provided by CoralWatch, Reef Check Volunteers, and staff and students at UQ and Heron Island Research Station. We also wish to thank those who provided field assistance: Rodney Borrego, Ian Leiper, Douglas Stetner, Josh Passenger, Megan Saunders, Robert Canto, Peran Bray, Meredith Roe, Jeremy Wolf.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe datasets generated and/or analysed during this study are not publicly available but are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003e(AIMS), A. I. o. M. S. (2024). \u0026quot;ReefCloud.\u0026quot;10.25845/g5gk-ty57\u003c/li\u003e\n\u003cli\u003eAlbright, R., et al. (2013). \u0026quot;Dynamics of seawater carbonate chemistry, production, and calcification of a coral reef flat, central Great Barrier Reef.\u0026quot; \u003cu\u003eBiogeosciences\u003c/u\u003e 10(10): 6747-6758.https://doi.org/10.5194/bg-10-6747-2013\u003c/li\u003e\n\u003cli\u003eBartley, R., et al. 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(2018). \u0026quot;Vulnerability of the Great Barrier Reef to climate change and local pressures.\u0026quot; \u003cu\u003eGlobal Change Biology\u003c/u\u003e 24(5): 1978-1991.https://doi.org/10.1111/gcb.14043\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"coral-reefs","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"core","sideBox":"Learn more about [Coral Reefs](http://link.springer.com/journal/338)","snPcode":"338","submissionUrl":"https://submission.nature.com/new-submission/338/3","title":"Coral Reefs","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Coral reef resilience, carbonate production, benthic composition, environmental disturbance, geomorphic zones, ecological time series","lastPublishedDoi":"10.21203/rs.3.rs-6668724/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6668724/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWhile reef resilience is widely studied, there is increasing recognition of the need to assess it through carbonate production estimates. This study investigated gross carbonate production on Heron Reef (southern Great Barrier Reef) over a 20-year period, examining responses to environmental disturbances and the role of key benthic taxa. Drawing on data from over 30 sites across four geomorphic zones, we identified branching \u003cem\u003eAcropora\u003c/em\u003e, tabular \u003cem\u003eAcropora\u003c/em\u003e, and \u003cem\u003eMontipora\u003c/em\u003e as the primary contributors to carbonate production due to their high abundance, fast growth rates, and elevated CaCO₃ output. Heron Reef\u0026rsquo;s average annual production rate of 18.45 kg CaCO₃/m\u0026sup2;/year places it among the more productive clear-water reefs in the Indo-Pacific. A strength of this study lies in its spatial and temporal scope, providing a refined understanding of how disturbances shape reef-building capacity across zones. Heron Reef showed strong resilience, with rapid carbonate production recovery following major events, although sharp declines were recorded during severe bleaching, such as in 2024. This analysis focused on carbonate production and does not incorporate direct bioerosion measurements, which are necessary to calculate full carbonate budgets and long-term reef accretion potential. Future work should address this gap by integrating erosion data to improve estimates of net production. Nonetheless, this study offers valuable insight into the ecological processes supporting reef resilience. It underscores the importance of high-resolution, long-term datasets for understanding carbonate dynamics and informing targeted conservation strategies in the face of accelerating climate change.\u003c/p\u003e","manuscriptTitle":"Two decades of coral carbonate production within and across geomorphic zones","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-06 14:06:50","doi":"10.21203/rs.3.rs-6668724/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-05T00:36:52+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-03T03:29:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-26T19:04:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"1394064354364110733825457197289867110","date":"2025-06-18T21:13:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"317497892282071790743035538819943190995","date":"2025-06-05T17:55:21+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-03T19:57:07+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-02T22:17:21+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-15T15:33:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Coral Reefs","date":"2025-05-15T04:30:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"coral-reefs","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"core","sideBox":"Learn more about [Coral Reefs](http://link.springer.com/journal/338)","snPcode":"338","submissionUrl":"https://submission.nature.com/new-submission/338/3","title":"Coral Reefs","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"279a12c2-8791-4ece-90ab-f2d73cf1a263","owner":[],"postedDate":"June 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-01T16:06:15+00:00","versionOfRecord":{"articleIdentity":"rs-6668724","link":"https://doi.org/10.1007/s00338-025-02736-4","journal":{"identity":"coral-reefs","isVorOnly":false,"title":"Coral Reefs"},"publishedOn":"2025-08-31 15:58:05","publishedOnDateReadable":"August 31st, 2025"},"versionCreatedAt":"2025-06-06 14:06:50","video":"","vorDoi":"10.1007/s00338-025-02736-4","vorDoiUrl":"https://doi.org/10.1007/s00338-025-02736-4","workflowStages":[]},"version":"v1","identity":"rs-6668724","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6668724","identity":"rs-6668724","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}