The footprint of endolithic algae in shaping the skeletal structure of massive coral skeletons: insights into micro and macro-porosity

The footprint of endolithic algae in shaping the skeletal structure of massive coral skeletons: insights into micro and macro-porosity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The footprint of endolithic algae in shaping the skeletal structure of massive coral skeletons: insights into micro and macro-porosity Edwin S. Uribe, Amalia Murgueitio, Carlos E. Gómez, Alberto Acosta, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5054349/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted 14 You are reading this latest preprint version Abstract Coral skeletons provide habitat for a euendolithic community, forming a green band within the skeleton, where Ostreobium spp. is the dominant group. Euendoliths, actively penetrate live coral skeletons, but how they use and modify skeletal structure is not properly understood. This study explores the microstructural characteristics of skeletal microenvironments through a micro-CT technique that analyzes the "footprint" of the euendolithic community on the porosity of coral skeleton. We compared three Porites species based on the percentage of the relative volume of microporosity, macroporosity, total porosity, and solid volume fraction of CaCO 3 among three distinct zones within the coral colony: coral tissue, the green band (characterized by eundolithic community) and the bare skeletal region. We found a significant increase in microporosity within the green band, while the opposite occurs for macroporosity that decreased within this zone, for all analyzed species. We describe a model to explain the porosity gradient along the vertical axis for Porites coral colonies, and suggests that within the “green band” microenvironment, the metabolic activity of the community is the responsible for this pattern. Our findings provide insights on the ecological relationship with the coral holobiont: macroerosion mitigation and microporosity filling. Biological sciences/Ecology Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Ocean sciences Intracolonial analysis coral skeleton microenvironments coral-reef porosity microboring micro-CT Porites spp Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. INTRODUCTION There has been growing interest in understanding the ecological role of microborers in coral skeletons. For instance, microbioerosion has been identified as the primary agent of bioerosion during the initial stages of colonizing dead coral substrates 1 , with erosion rates reaching up to 1 kg m − 2 year 2 , 3 , where the endolithic community is the primarily responsible for this process 4 . Coral skeletons provide vital niches for the survival of microorganisms, which vary in response to physical and chemical gradients such as oxygen, light, pH, and porosity, among others 4 – 6 . It has been observed that algae from the genus Ostreobium (Chlorophyta: Ulvophyceae: Bryopsidales) are the dominant group in the endolithic community of coral skeletons and other marine substrates 7 . Morphologically, euendoliths create green bands beneath live coral tissues that are visible in cross-sectional cuts of the skeletons 8 , 9 . While recent research has focused on Ostreobium , there are still many gaps in our understanding of the biology and their intricate relationships with corals 9 . The ecological role of Ostreobium spp. within the coral holobiont emphasize both beneficial and potentially harmful interactions for the host. On one hand, Ostreobium is thought to engage in mutualistic symbiosis with corals, transferring photo-assimilates and receiving shelter in return 10 , 11 . Likewise, these algae can offer an alternative source of energy to bleached corals (with live polyps), facilitating recovery by reducing light stress 6 , 12 , 13 . On the other hand, Ostreobium significantly contributes to microbioerosion in dead coral skeletons, dissolving up to 20% of deposited CaCO 3 2,3 . As other euendoliths, it actively penetrates live coral skeletons, potentially weakening them and increasing vulnerability to mechanical damage 14 . Nevertheless, the balance of beneficial and detrimental roles of boring microalgae, as well as the exact characteristics of the microenvironments they use or create are not fully understood, and are still a matter of active research 4 , 9 , 15 . Micro-CT (X-ray microtomography) porosity analysis is proposed as an innovative tool for studying micro and macrobioerosion in corals 16 – 18 . This technique utilizes X-ray beams to scan the three-dimensional structure of coral colonies at a micron-scale resolution 19 . Calcium carbonate's X-ray attenuation properties distinguish the solid coral skeleton from its macro and micropores, facilitating quantitative porosity analysis 17 , 20 . In contrast with other techniques, micro-CT offers several advantages, including 3D mapping, high resolution, non-destructive sample handling, and versatile scale assessments 18 , 21 . There are several studies utilizing micro-CT to analyze the porosity microenvironments of stony coral colonies 16 , 18 , 22 , but no one investigated the impact of the green band on coral skeleton porosity. Corals with massive growth, such as Porites genus, serve as excellent models for studying intra-colonial microenvironments 3 – 5 , 23 . These growth forms usually stratify into different zones along a vertical profile, ranging from the outermost part of the colony (the polyps or living tissue zone) to the base, where the bare skeleton is located. However, since in many cases these skeletons exhibit a green band containing Ostreobium spp. 24 , 25 and other endolithic microorganisms (e.g., cyanobacteria, fungi and green algae), this band can be delineated as a third zone. These three zones (coral tissue, green band and skeleton) have been proposed and used in various studies, revealing significant changes in physicochemical variables along this vertical gradient 6 , 26 . For instance, some studies have identified microenvironmental gradients, with higher oxygen levels and pH in the green band and a decreasing pattern toward the base of the skeleton 5 , 14 , 27 . These gradients can be influenced by various factors, such as light availability, nutrient availability, pCO 2 , and water flow 14 . Colombia has two oceanic basins (Pacific and Caribbean) that exhibit a wide variety of marine environments with contrasting characteristics. In the Caribbean Sea, high impact anthropogenic activities have significantly altered the natural conditions of coral ecosystems 28 , 29 . Conversely, in the Pacific, anthropogenic impacts have been lower, but environmental conditions are naturally more variable and abrupt, including lower pH conditions and temperature changes due to ENSO 29 , 30 . In this context, Caribbean reefs are geographically more widespread, with broad bathymetric ranges with a wide diversity of coral species, but generally have low coral cover in most locations 29 , 31 . In contrast, the Colombian Pacific hosts coral reefs with a more limited geographical distribution and bathymetric range, featuring less diverse reef-forming assemblages, but a generally high coral cover 32 , 33 . Despite these known differences, exploration of potential variations in the intra-colonial physical structure of corals in both Colombian regions remains uncharted. Given the ecological and economic significance of coral ecosystems 34 and the context of accelerated coral reef degradation 35 , as well as the previously identified knowledge gaps that hinder the understanding of intracolonial microenvironments and the role of the endolithic community in bioeroding corals, this study aims to characterize and to compare the porosity of the internal skeletal areas of Porites lobata and P. panamensis from the Colombian Pacific and P. astreoides from the Caribbean, using the micro-CT technique. Specifically, the objective was to compare the vertical porosity profile of skeletal fragments, to determine whether these patterns vary with interspecific factors like location and coral species and finally to propose a model describing intracolonial variation. Additionally, Scanning Electron Microscopy (SEM) was employed to explore the morphology of pores and traces of bioerosion in these coral skeletal fragments. 2. MATERIALS AND METHODS 2.1 Sample collection Thirty (30) samples of coral skeletons corresponding to Porites astreoides (Lamarck, 1816 ), P. lobata (Dana, 1846) and P. panamensis (Verrill, 1866) were selected from the Natural History Museum at Universidad de Los Andes (Bogota, Colombia). Porites astreoides samples (n = 10) were collected in 2018 from West View, San Andres Island (Caribbean Sea) (12°31'15.45"N, 81°43'48.60"W) from a bathymetric range between 5-35m. Porites lobata (n = 10) and P. panamensis (n = 10) were collected in 2019 from Gorgona Island (Colombian Pacific) at a depth of 12m (2°59'24.19"N, 78°10'7.12"W) (Figure S1 ). Using SCUBA, all samples were extracted with hammer and chisel, placed in plastic bags, and labelled for subsequent morphological identification based on the characteristics described in the literature 48 , 49 . 2.2. Porosity Analysis 2.2.1. Sample Preparation Fragments of ~ 1cm³ were cut using a Proxxon MBS 240/E diamond micro bandsaw. Photographs of all faces of the fragments were taken with Lumenera's INFINITY1-1M camera integrated with a JSZ6 stereoscope. A scale was included in each image to provide a reference for the fragment size. ImageJ software was employed for all measures such as polyp zone, green band and skeleton (Fig. 6 ). The samples were labeled and grouped in 50ml Falcon tubes, with 5 to 6 fragments separated by a plastic layer. These samples were subsequently sent to the X-ray Micro-CT Laboratory at the Australian National University (ANU, Canberra, Australia) for processing with a Micro-CT scanner (CITES permit #46697). 2.2.2. Tomography Processing Each tomography produced a three-dimensional (3-D) NetCDF format (.nc) that had an original dimension of 1400 x 1400 x 3280 voxels (three-dimensional pixels) and a minimum resolution of 24.3µm (Fig. 6 C). Subsequently, 3-D images were uploaded to the WebMango platform (Australian National University), that facilitates tomographic modifications through a system of image filters. The sequence of this process involved three general steps: i) masking filter (removal of artifacts such as the Falcon tube and fragment separators) (Fig. 6 D), ii) segmentation filter (division of the image into phases or materials) (Fig. 6 E), and iii) porosity analysis (quantitative estimation of in the skeletal structure) (Fig. 6 F) 17 . Each voxel in the tomography belongs to one of four categories (colors). Red voxels denote areas where the skeleton is dense and solid. Black voxels represent air or embedded void spaces (macropores). Green areas represent an intermediate phase between the solid (red) and air (black) and they are technically termed micropores; those pores with sizes smaller than the tomographic resolution (24.3µm), which influence tomographic intensity and are thus quantifiable 17 . Gray-colored voxels are referred to as mask, primarily indicating the volume within the tomography that does not belong to the colony. However, in specific cases, they may denote voids within the skeletal structure, which, due to their significant size, are connected to the exterior of the colony and are not considered as pores. Using the volumes of the segmented image phases, a porosity analysis was performed to calculate four variables related to the total volume of the colony: i) the relative volume (%) of microporosity (MiP), ii) macroporosity (MaP), iii) the total volume (%) of porosity (TP), which is the sum of macro and microporosity percentages, and iv) the solid volume fraction (SVF), representing the relative volume (%) of the solid skeletal structure (CaCO 3 ). Calculations were conducted along all three axes of the fragment-3D (X, Y, Z) at 0.9*0.9*0.9mm distance intervals. Thus, this process generated a porosity map that replicated the original fragment's shape, overlaying it with numerical values for the estimated variables (Fig. 6 F). This approach facilitated the observation of changes or gradients in these four variables (MiP, MaP, TP and SVF) along all three axes (X, Y, Z) of each fragment, enabling the assessment of skeletal variation, as well as the general differences among fragments from different species or locations in the Caribbean and the Pacific. 2.3. Intra-colonial scale The Z-axis is referred to as the vertical profile (Fig. 6 F), enabling the examination of patterns within skeletal microenvironments. Notably, not all vertical profiles of the fragments were suitable for intraspecific analysis due to physical damage. Nevertheless, the fragments excluded from this analysis were still useful for interspecific comparisons (next section). Consequently, four fragments without physical damage were selected for each species (12 analyzed fragments). The zones observed in the stereoscope for the three microenvironments (coral tissue, green band & skeleton) along the vertical profile were assigned to each fragment based on measurements taken in ImageJ (see section 2.2.1 ). For every fragment, average porosity (± S.E.) was graphed for the different coordinates along the vertical profile. 2.3.1. Coordinates Transformation To compare skeletal variation among selected fragments, the coordinates of the three axes (X, Y, Z) of the porosity maps were transformed into a relative scale using Eq. 1 (Zjinorm). This transformation allowed for comparisons of fragment sizes and facilitated locating porosity data within the intra-colonial space with a common origin for all fragments. After this normalization, the scale was transformed into millimeters (mm) (Zjimm) (Eq. 1) based on a conversion factor (8mm), representing the length of the largest porosity map sampled in the Z-axis, and a correction factor (0.45mm), since each porosity point better represents the middle of the range sample interval of 0.9mm (see section 2.2.2 ). For the Z-axis, the coordinate scale ranged between 0 and 10mm for better visualization, where the limit of 10 referred to the most basal region of the skeleton, and the limit of 0 indicated the apical areas of the colony where living tissue (polyps) was situated. The same transformation was applied to the X and Y axes, but no clear porosity patterns were expected among fragments, as the most common stratification mentioned in the literature occurs along the vertical axis (Z-axis) 4 , 38 . However, some results for these two axes are briefly discussed in the present study. Eq. 1 represents coordinate transformation to mm for each fragment along the Z axis (Zjimm): $$\:{Zji}_{mm}=\:{(Zji}_{norm}*\:8\:mm)+0.45\:mm\:;{\:Zji}_{norm}=\:\frac{Zji-{Zji}_{min}\:}{\:{ZI}_{max}-\:{ZI}_{min}}$$ Where Zjinorm represents the normalized j-coordinate for fragment i, dependent on the minimum coordinate value of the i fragment (Zimin) as well as the maximum (ZImax) and minimum (ZImin) coordinates of the largest selected fragment I. It is important to note that the denominator is relative to the largest fragment (I) for standardized size comparisons among all selected fragments. 2.3.2. Variable transformation The intra-colonial analysis for MiP, MaP, TP and SVF involved transforming the values and constructing models to explain the vertical profile of the selected fragments. Two transformations were applied to the response variables, involving the calculation of deltas (∆) and data normalization (Eq. 2). The purpose of this equation is to preserve intra-colonial variation since statistics with raw (non-normalized) values tend to homogenize profile gradients, which would result in a vertical profile that becomes linear and fails to display the porosity fluctuations in the intra-colonial environments. Eq. 2 represents transformation of response variables (MiP, MaP) for Intra-specific analysis: $$\:{Vji}_{norm}=\:\frac{\varDelta\:\:}{{\varDelta\:}_{max}}\:;\:\varDelta\:\:=\:Vji-{Vi}_{min}\:;\:\:{{\varDelta\:}_{max}\:=Vi}_{max}-{Vi}_{min\:}$$ Where, Vjinorm represents the normalized j-value of fragment i for the variable V. It is calculated as the delta between the unnormalized value (Vji) and its corresponding minimum value within the same fragment (Vimin) divided by the difference between the maximum value (Vimax) and the minimum value (Vimin). 2.4. Inter-specific scale The total number of samples analyzed (n = 30) were used to ensure a more robust statistical analysis. The response variables were not transformed, as intra-colonial gradients were not considered at this scale. Consequently, each fragment had only one porosity value, as opposed to a porosity map per fragment. To achieve this, the porosity map values of each fragment were averaged into a single value for MiP, MaP, TP and SVF. At this inter-specific scale, the goal was to identify differences among all fragments between locations (Caribbean and Pacific) and species. 2.5. Statistical analysis 2.5.1. Intra-colonial statistics Local Polynomial Regression (LOESS) models were used to elucidate intra-colonial variation of the skeletal fragments, which consider local variation within a data series, based on a span of analyzed data points regarded as neighbors. The specific variation of intra-colonial porosity data points (e.g., Fig. 2 F) was fitted into single curve across the axes of the fragments (X, Y, Z). Descriptive statistics, encompassing means and standard errors, were computed for the 12 samples. ANOVA and Tukey’s Honestly Significant Difference (HSD) test were performed to assess statistical differences between the three microenvironment zones (polyps, green band, and skeleton), following verification of normality and homoscedasticity assumptions. Finally, Spearman Correlation test was conducted between pairs of groups of response variables along the Z-axis of each fragment. 2.5.2. Inter-specific statistics ANOVA and the Tukey’s Honestly Significant Difference (HSD) test for the response variables MiP, MaP, TP and SVF were performed for species-level comparisons with balanced n-values, after verifying the assumptions of normality and homoscedasticity. For comparing locations, a non-parametric Kruskal-Wallis’s test was used, taking into account the imbalance in sample sizes between the Caribbean (n = 10) and the Pacific (n = 20), following inter-specific Spearman correlation test among response variables. 2.6. Scanning Electron Microscopy Additional fragments (n = 19) of ~ 1.5cm long of the same coral colonies used for micro-CT analysis were obtained by fracturing them (hammer and chisel). The objective was to secure a vertical profile like the one illustrated in Fig. 1 A, encompassing tissue, the green band, and the base. The samples underwent a hydrogen peroxide treatment to eliminate any remaining tissue in the colony, followed by rinsing with distilled water and overnight drying. To enhance conductivity, the unobserved faces of the fragments were covered with aluminum foil and affixed to a metallic surface using SEM conductive double-sided carbon tape. Additionally, a layer of gold was applied via vacuum coating prior to examination with a Tescan Vega 4 Scanning Electron Microscope. For each fragment, a general image was captured at 30X, followed by higher magnification close-ups in each of the three microenvironments (Coral tissue, green band & skeleton) at 100X, 500X, 1000X, 5000X, and 10000X to capture the porosity, micropore morphology, and bioerosion traces in the samples based on previous descriptions found in the literature 36 , 38 . 3. RESULTS Clear patterns were identified for microporosity-MiP, macroporosity-MaP, solid volume fraction-SVF, and total porosity-TP, at different scales of analysis. At the intra-colonial scale, MiP and MaP proved to be more relevant. Conversely, in the inter-specific scale, which involves the comparison between species and geographical locations, the variables SVF and TP gained more significance. 3.1. Intra-colonial porosity The average MiP across fragments indicates that micropores represent less than 11% of the total volume, while MaP accounts for up to 47% (Table 1 ). The mean SVF (overall 52%) exceeded TP (overall 42.7%) for most fragments (except for 15G and 28G), indicating that the percentage of CaCO 3 is higher than the air spaces. Figure 1 shows the vertical profiles of fragments where the apical zone corresponds to the coral tissue at 0 mm, and the basal zone corresponds to the skeleton at approximately 10 mm (samples were cut at this size). However, the common total vertical length recorded by the porosity map (Z length Table 1 ) ranged between ~ 5 mm to ~ 9 mm because not all fragments had the same vertical length, due to variations in the cuts and segmentation results. Additionally, the observed green band locations varied between 1.1 mm and 3.9 mm along the vertical profile. Thus, this amplitude was used to distinguish the green band microenvironment from other zones within the fragment. Table 1 Average ± standard errors (s.e.m) for the calculated response variables (MiP, MaP, TP, SVF) of the selected coral skeletal fragments: green band width (GB) in the vertical profile, microporosity (MiP), macroporosity (MaP), total porosity (TP) and solid volume fraction (SVF). Notably, the percentages provided here are averages, thus, the sum of TP and SVF does not necessarily equal 100%. P = Porites panamensis; L = P. lobata ; A = P. astreoides. ID Depth (m) Species Location Z length (mm) GB (mm) MiP % MaP % TP % SVF % 15G 12 P Pacific 7 1.1–2.2 5.7 ± .08 44.4 ± .43 50.1 ± .40 44.2 ± .46 28G 12 P Pacific 9 1.7–2.9 10.9 ± .12 34.9 ± .39 45.8 ± .40 46.1 ± .51 36G 12 P Pacific 7 1.6–2.3 5.7 ± .74 47.0 ± .80 52.7 ± .69 42.6 ± 1.14 47G 12 P Pacific 7 1.4–2.6 7.9 ± .12 35.6 ± .71 43.5 ± .62 50.3 ± .68 10G 12 L Pacific 7 2.3–3.2 6.8 ± .11 35.5 ± .43 42.3 ± .37 53.1 ± .39 19G 12 L Pacific 8 1.5–3.6 3.9 ± .06 44.0 ± .28 47.9 ± .24 48.5 ± .23 26G 12 L Pacific 8 1.9–3.9 7.6 ± .11 29.8 ± .43 37.4 ± .38 57.5 ± .42 39G 12 L Pacific 7 1.7–3.4 5.7 ± .09 36.8 ± .46 42.5 ± .38 52.9 ± .39 A10 35 A Caribbean 5 1.8–2.8 7.3 ± .14 36.5 ± .43 43.8 ± .35 51.8 ± .38 A11 35 A Caribbean 7 1.5–1.9 5.8 ± .09 35.5 ± .33 41.3 ± .28 55.7 ± .29 A3 9 A Caribbean 7 2.3–3.8 7.2 ± .07 27.5 ± .21 34.6 ± .17 61.9 ± .14 A5 10 A Caribbean 6 2.2–3.2 10.7 ± .14 20.1 ± .47 30.8 ± .37 64.0 ± .36 Overall 1.1–3.9 7.1 ± .05 35.6 ± .18 42.7 ± .15 52.2 ± 0.17 Repeated patterns of both variables (MiP and MaP) were observed along the vertical axis of the 12 analyzed fragments (Fig. 1 ). The % of MiP exhibits a monomodal curve with MiP peaks (zones of high MiP) related to the observed green band and an asymmetric shape towards the apical regions of the fragment. Conversely, MaP curves tend to decrease in the areas near the green band for the majority of the profiles. For the later variable, the monomodal behavior is not as evident as in MiP, but the asymmetry of the valleys towards the apical regions is preserved. Regarding the vertical profiles of TP and SVF (Fig. 1 ), the curve shapes do not exhibit the prominent peaks and valleys observed in MiP and MaP. However, a strong similarity between TP and MaP profiles is apparent, with some curves almost mirroring each other in shape (e.g., 47G P. panamensis , Fig. 1 ). Additionally, for SVF, the notable pattern observed is its inverse graphical correlation with MaP and TP. The location (note that location ≠ magnitude) of peaks and valleys of the response variables in the vertical profile was correlated (Spearman correlation test) with the observed location of the green band in the stereoscope (solid horizontal green lines Fig. 1 ). A positive and significant correlation was found between MiP peaks and the observed green band location (ρ = 0.66, P < 0.05) and between MaP valleys and the green band location (ρ = 0.72, P 0.05) / MaP valleys (ANOVA: F = 0.9, P > 0.05). Spearman correlation across the fragment's vertical profile (Table 2 ) detected an inverse relationship between MiP and MaP (ρ=-0.67, P < 0.05), where MiP increases as MaP decreases in the vertical profile (e.g., 10G P. lobata Fig. 1 ). The other variables exhibit the expected correlations, with TP being inversely correlated with SVF (ρ=-0.98, P < 0.05), and MaP positively correlated with TP (ρ = 0.96, P < 0.05). The MaP–TP correlation indicates that macropores, due to their large size, have the greatest influence on changes in the total porosity (TP) of the fragment, emphasizing the similarity between the vertical profiles of these two variables. Table 2 Intra-colonial scale Spearman correlations. Groups between response variables in the vertical profile (Z) of the fragments. The Asterisks represent significant correlations with p-value < 0.001). Micro.Porosity Macro.Vol.Fraction Porosity Solid.Vol.Fraction Microporosity (MiP) 1 Macroporosity (MaP) -0.67*** 1 Total porosity (TP) -0.46*** 0.96*** 1 Solid volume fraction (SVF) 0.32*** -0.90*** -0.98*** 1 Based on the LOESS model for microporosity for each species and an overall model (Fig. 2 A-B), there is evidence for the influence of the endolithic community on coral skeletal structure, albeit some variation in peak height and amplitude. Porites panamensis exhibited the highest peak (∆ max = 5.61%), followed by P. lobata (∆max = 4.65%), and P. astreoides (∆ max = 3.93%). The overall model shows a maximum peak of 4.42% compared to the reference minimum value. The final pattern maintains the relationship observed, where there is an asymmetry towards the apices of the skeleton (vertical profile < 5 mm). Considering that the average MiP of all fragments is ~ 7% (Table 1 ), the microporosity in the green band accounts for more than half of the average microporosity that can be present in colonies of these species. Significant differences were found for the three zones of coral fragments (Tukey HSD test) for all species and in the overall model. The microporosity of the green band zone is significantly different from the microporosity of the most extreme zones of living tissue and skeleton (supplementary material) (Fig. 2 C). Likewise, the single model maintains statistical differences between the three zones (Fig. 2 D). These results indicate that the mean and median values found in the green band are significantly higher than those at the opposite ends of the other zones, thus, there is more similarities at the boundaries of the zones, and therefore, the changes between the different bands of the fragment are gradual across the vertical profile. The LOESS model of MaP (Fig. 3 A-B) shows low ∆ values forming valleys in the regions of the green band. The largest difference (∆max - ∆min) between the valleys of the green bands and the other zones of the vertical profile (skeleton and living tissue) was found in P. lobata (~ 12%) with a ∆min of ~ 12% and a ∆max of ~ 24%. In P. panamensis the difference was 10% with ∆min of ~ 12% and a ∆max of ~ 22%. Lastly, P. astreoides had a total difference of 9.5% with a ∆min and ∆max of 9.3% and 18.8%, respectively. The overall model showed a MaP valley with a ∆min of 12.8% in the green band and an increase in MaP (∆max of ~ 19%) towards the basal zones of the fragment, i.e., a total difference of 6.2%. Like the peaks of microporosity, the Map valleys of the general and species-specific models are located towards the apical regions of the fragments (vertical profile < 5 mm). The MaP in the different zones (Fig. 3 C-D) shows the variations in the proposed LOESS models (Fig. 3 A-B). For P. panamensis , the green band zone did not show significant differences for MaP compared to the other zones of the fragment ( P > 0.05). Similarly, in P. astreoides , MaP values of the green band are not different from those of the living tissue, but they are different from the more basal zones ( P < 0.01). Only for P. lobata , the significant differences of the green band are clear compared to the other zones ( P < 0.001). The overall model maintains the variations seen at the species level; however, the most basal extreme of the fragment, at the 8.45mm band in the vertical profile, are not different from the green band, mainly due to the high dispersion of values in this zone (whisker amplitude). In this case, it was compared with the previous band (7.45 mm), where significant differences are found ( P < 0.001), as is also the case when comparing the green band to the living tissue ( P < 0.001). For SVF and TP, the intra-colonial results from both the overall and species models display inconsistencies. While the models exhibit some variations along the vertical profile, these variations do not consistently repeat in the same manner among the species models (supplementary material). Consequently, the overall LOESS model exhibited a vertical profile that is predominantly linear, with no significant differences observed between the three microenvironments ( P > 0.05) (supplementary material). Despite the lack of consistent intra-specific variation, these variables are retained in the analysis because their significance becomes more apparent when discussing inter-specific differences. The SEM images revealed traces of the endolithic community in the selected colonies and in different zones of the fragments. Figure 4 A displays the typical structural differences between macro and micropores. The macropores are evident over the minimum resolution of micro-CT analysis (24.5 µm) and are even recognizable without any special equipment, as they comprise a significant proportion of the fragment volume. Conversely, the micropores, especially those related to the endolithic community, can be seen with a frequent diameter < 10 µm (Fig. 4 A-B). Additionally, these are connected to tunnels that resemble the microborers’ filaments (Fig. 4 A green bars) of the same diameter as the micropores. Even when the micro-CT analysis revealed that MiP is higher in the green band, traces of these micro tunnels or sinuous branching tracks 36 were seen qualitatively with SEM in all fragment zones, although less frequently in the coral tissue. The latter means that the euendolithic community is present along the vertical profile although in lower densities than the green band. However, one particularity is that these micropores were commonly surrounded by crystal-shaped structures in the skeleton zone (Fig. 4 C) compared to a flatter surface in the green band micropores (Fig. 4 B). In some cases, these crystals cover a large part of the pore space (Fig. 4 D). 3.2. Inter-specific porosity Figure 5 shows the most relevant results conducted for the overall sample fragments (n = 30). Between locations (Caribbean and Pacific), significant differences (Kruskal-Wallis) were found only for SVF (Fig. 5 A) ( P < 0.01) and TP (Fig. 5 B) ( P < 0.05), indicating that fragments from the Caribbean have a higher solid volume (mean SVF ~ 60%) and a lower total porosity volume (mean TP ~ 40%) than in the Pacific (mean SVF ~ 50% and TP ~ 45%). Although, no significant differences were detected between locations for MaP and MiP ( P > 0.05), the values indicate that, on average, Pacific fragments exhibit MiP equivalent to 7.2% of the total colony volume, compared to 6.1% for the Caribbean. Concerning MaP, the mean value for the Pacific species (36.7%) is higher than the mean value of the Caribbean species (33%). These percentages align closely with the averages observed (MiP ~ 7%, MaP ~ 36%) for the 12 selected fragments from the intra-colonial models. The comparison between species shows significant differences for SVF (Fig. 5 C) and MiP (Fig. 5 F), where P. lobata and P. panamensis were not statistically different to each other but different from P. astreoides. For the variable TP (Fig. 5 D) and MaP (Fig. 5 E), only P. lobata is statistically different from P. astreoides , which has the highest average value of SVF (58%), and the lowest values of TP (39%) and MaP (33%), followed by P. panamensis (SVF = 51%, TP = 41%, MaP = 32%) and P. lobata with the lowest values of SVF (49%) but the highest values of TP (46%) and MaP (40%). These results indicate that species from the Pacific are more porous than species from the Caribbean. However, in the case of MiP (Fig. 5 F), the differences between species do not align with the locations, as the two Pacific species are statistically different from each other ( P < 0.05) but not different from P. astreoides . For MiP, P. panamensis has the highest value (9.3%), followed by P. astreoides (6.1%), and P. lobata (5.3%). The inverse relationship (Pearson correlation) between MaP and MiP at the inter-specific level (Fig. 5 G), where higher MiP values coincide with lower MaP values (R=-0.77) are in accordance with the intra-colonial results (R=-0.6), indicating that it operates at different scales of analysis. The remaining results demonstrate the expected typical relationship, such as SVF being inversely correlated with TP (R=-0.96) (Fig. 5 H) and the positive correlation between TP and MaP (R = 0.98) (supplementary material). 4. DISCUSSION Our findings revealed that average microporosity values (~ 7%) were consistent with those reported for coral fragments of Pocillopora (~ 5–10%) and Acropora (~ 12–15%) under normal growth conditions 37 . However, the average macroporosity of 36% was higher than the ~ 15– 25% reported by Leggat et al. 37 . This might be attributed to the massive growth form of our coral skeletal fragments. Similarly, Krause et al. 38 documented a higher total porosity of ~ 51% for Porites , exceeding the average TP of ~ 43% in our study. This observation aligns with previous findings indicating that massive growth species like Porites spp., tend to exhibit higher porosity (i.e., less dense skeletons) compared to branched and foliaceous species 39 . The observed differences could also be related to the life-history of our coral fragments, as species-specific biogeographical settings and associated environmental conditions can influence skeletal density and porosity 37 . Further comparative studies utilizing micro-CT porosity analysis across diverse coral species are needed to elucidate these relationships. The position of the green band, indicative of mobile phototrophic community, was generally observed near the apical zones of the fragments, consistent with their light-seeking behavior. In our study, the green band in Porites species was located between 1 mm and 5 mm from the apical zone (living tissue), with a maximum thickness of 4mm. While Kühl et al. 5 reported a slightly deeper green band position in Porites (5–10 mm from the apical perimeter), their measured thicknesses (3–5 mm) align with our results. Similarly, other studies have documented green band positions ranging from 2mm to 6mm below the coral surface, with widths between 2 mm and 4 mm 26 , further supporting our observations. The asymmetry of porosity curves and the apical positions of the green band suggest a correlation between porosity peaks and valleys and areas of higher light intensity within the colony, as previously documented 14 , 40 . This alignment between asymmetric micro- and macroporosity curves within the green band is also consistent with reported patterns of intra-colonial gradients 4 . The observed positive correlation and non-significant differences between the peak/valley’s locations of micro- and macroporosity, and the locations of the green band observed with the stereoscope method, indicate a consistent alignment between the two methodologies. However, stereoscopic measurements capture only surface features. While the green band thickness and position may differ between the surface and the interior of the coral skeleton, micro-CT provides a more precise 3-D analysis 17 . Furthermore, the coral skeleton itself acts as a record keeper, increasing the uncertainty regarding the exact position of the green band 41 . Traces of the green band, such as elevated microporosity, may persist in the skeleton even after the endolithic community has migrated, for example, as the colony grows and the community shifts towards areas of higher light intensity near the polyps 6 . Despite these potential sources of variations, our results show strong correlations between the positions and amplitudes (in mm) of the green band and the vertical profiles of micro- and macroporosities, supporting the use of micro-CT for delineating intra-colonial variation. The consistent intra-colonial porosity patterns observed across sampled fragments and species, provide insights into the microenvironments of massive Porites species. The areas with a high concentration of the endolithic community (green band) exhibited significantly higher microporosity values compared to other microenvironments within coral skeleton. These observations align with other studies in which the metabolic activity within the green band leads to the formation of channels less than 10µm in diameter 23 , 42 , classified as micropores in tomographic analysis 17 , 37 . Our micro-CT values revealed an average microporosity increase of approximately 4% within the green band. While this suggests a low overall influence of the endolithic community in the skeletal porosity, it is important to note that this increase represents a substantial proportion of the total average microporosity (7%) observed in the analyzed fragments. Therefore, the green band represents the zone with the maximum achievable microporosity within analyzed colonies. While the coral skeleton preserves traces of past endolithic activity 41 , the observed decrease in microporosity below the green band suggests an active modification of the skeletal structure. Although microbioerosion by the endolithic community initially increases this value, why does not this increase persist below the green band? This process appears to be counteracted by secondary reprecipitation of calcium carbonate. SEM images (e.g., Fig. 4 ) reveal crystals characteristics of this secondary precipitation within the green band, supporting findings from other studies 36 , 38 , 43 . These studies demonstrate that endolithic algae, such as Ostreobium , can transport micro-eroded calcium from apical tips to the thallus base, where it re-precipitates as secondary aragonite along the pore edges. This "porosity filling" process, involves the cementation and compaction of crystals of less than 10µm in width, in a form of early diagenesis, leading to observable changes within the coral skeleton as observed in our study and elsewhere 36 , 38 , 44 . This phenomenon likely contributes significantly to the gradual decrease in microporosity observed below the peak. Such evidence suggests new indirect relationship between endolithic community and coral host, supporting the mutualistic hypothesis proposed by Schlichter et al. 10 , and corroborated by more recent studies 6 , 45 , 46 . This hypothesis proposed that while endolithic activity can initially increase porosity, it also triggers secondary processes that ultimately enhance skeletal density and potentially benefit the coral holobiont. Unexpectedly, the green band zone exhibits significantly lower macroporosity values compared to the coral tissue and skeleton. The minimum values observed across the entire vertical profile were consistently located within the green band, with an approximately 13% decrease, which represents a substantial mitigation of macroerosion, equivalent to approximately one-third of the typical macroporosity value (47%). In this context, our findings support new evidence of the role of the endolithic community to the coral skeletal matrix and coral-reef framework. The observed macroporosity valleys within the green band, suggest that the endolithic community, through direct and/or indirect mechanisms, actively influences the physical structure of the macropores within this skeletal region. Furthermore, the negative correlations between micro- and macroporosity, and to a lesser extent between micro- and total porosity, suggest a potential link between the increased microporosity and a reduction in both macropore size and overall skeletal porosity. This reduction in porosity could be attributed to the infilling of larger pores by secondary aragonite precipitation, as evidenced by the previously discussed SEM images and supporting literature. While the specific mechanisms by which the green band is related to macropore reduction in the CaCO 3 skeleton are beyond the scope of this article, existing research suggest a complex interplay between endolithic activity and skeletal porosity. This is achieved through a mechanism of enhanced photosynthetic activity within the green band, which captures CO 2 increasing the pH, thereby diminishing chemical erosion by CaCO 3 dissolution 5 , 46 . This pH increase potentially minimizes acidification-induced erosion, resulting in fewer air spaces and lower overall porosity within the skeleton. However, this apparent beneficial effect is offset by the increased metabolic activity and population density of the endolithic community that leads to greater microbioerosion in the form of tunnels, potentially causing skeletal damage (up to 7%) 14,36,38,43,46 . Essentially, the benefit of acidification mitigation also implies potential structural weakening through microboring. This idea is supported by observations of species inhabiting different pH environments 35 . For example, we found Pacific species like P. lobata , which typically experience lower pH and different carbonate chemistry conditions than the Caribbean Sea 30 , 47 , exhibited more macropores within the skeletons compared to Caribbean species like P. astreoides (Fig. 5 B-E) as has been found in other studies 35 . This suggests a potential link between pH, endolithic activity, and porosity, although further research is needed to confirm a direct cause-effect relationship. Examining the precise effect of endolithic community on coral colonies using true colonial controls (fragments lacking a visible green band) presents significant challenges. Firstly, endolithic algae, such as Ostreobium spp., colonize coral skeletons early in the life cycle 42 . This early colonization makes it difficult to find coral fragments devoid of a green band for control groups, as colonization is likely throughout the coral’s lifespan 42 . Secondly, the absence of a visible green band does not guarantee the absence of endolithic activity. While chlorophyll pigmentation might fade over time (weak signal), the physical marks of microerosion, such as peaks in porosity and endolithic channels seen in SEM, persist 36 . This makes coral skeletons a valuable historical record of past endolithic activity 41 . As a point of comparison, rhodolite fragments were also analyzed in this study and exhibited no clear zonation or patterns in their vertical profiles, indicating that the observed patterns in the coral skeletons are indeed species-specific (supplementary material). The interspecific analysis further provides evidence for the relationship between coral species, geographic location and skeletal porosity, which helps to support the intra-colonial analysis. Although solid volume fraction (SVF), total porosity (TP), and macroporosity values support this interspecific pattern linked to acidification and geographic variation (Caribbean vs Pacific), microporosity values surprisingly do not. This suggests that microporosity unlike the other porosity measures, is less influenced by locations or species. Instead, it appears more sensitive at the microenvironmental factors or gradients within the coral colony (intra-colonial scale). This further supported by the observations that microporosity exhibits most distinct patterns within the vertical profile analyzed in this study. In conclusion, our study provides insights into the relationship between endolithic community and skeletal porosity of massive Porites species, revealing distinct porosity patterns across three intra-colonial zones, suggesting a key role for endolithic metabolic activity in shaping the skeletal structure. Specifically, we observed a consistent increase in microporosity and a decrease in macroporosity within the green zone across all three studied species, regardless of their location, depth, or environment. This suggests a universal influence of endolithic communities on Porites skeletal structure. The green band is of particular interest, potentially mitigating total porosity by re-mineralization and porosity filling activity. Our findings highlight the influence of multiple intracolonial gradients playing a crucial role in the final distribution of porosity along the vertical profile. Therefore, we propose that endolithic communities exert a significant influence on the structural properties of the coral skeleton (i.e., macroporosity and total porosity), extending beyond the previously documented mutualistic benefits. Declarations AUTHOR CONTRIBUTIONS STATEMENT JAS, CEG, AA conceived de study and refined the methods for analyzing the data. ESU, AM obtained and analyzed the data and wrote the first draft of the manuscript. ESU, AM, JAS, CEG, AA provided general feedback for the manuscript. All authors approved the final version of the manuscript. COMPETING INTEREST The authors declare no competing interest. Author Contribution JAS, CEG, AA conceived de study and refined the methods for analyzing the data. ESU, AM obtained and analyzed the data and wrote the first draft of the manuscript. ESU, AM, JAS, CEG, AA provided general feedback for the manuscript. All authors approved the final version of the manuscript. Acknowledgement The authors acknowledge the instruments and scientific and technical assistance of the MicroCore Microscopy Core at the Universidad de Los Andes, a facility that is supported by the vice presidency for research and creation. We acknowledge the help from Valentina Echeverry, Manuela Cortés and Alejandro Preciado (Jovenes Investigadores del programa UniAndes-PUJ), for the cuts, stereoscope method and preliminary analysis. Lydia Knuefing helped in the thomography processing and WebMango platform. This study was funded by the Ministerio de Ciencia y Tecnología – Minciencias, Colombia, through the grant # 1204-852-70251 “Observatorio de la microbioerosión, acidificación oceánica y disolución de arrecifes coralinos”. Data Availability Some data are available in the main text or the supplementary materials. Raw data from Microtomography are all found in Figshare.com project 220825: DOI: 10.6084/m9.figshare.27041776 (https://figshare.com/account/projects/220825/articles/27041776) References Tribollet, A. & Golubic, S. Cross-shelf differences in the pattern and pace of bioerosion of experimental carbonate substrates exposed for 3 years on the northern Great Barrier Reef, Australia. 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Supplementary Files 1.UribeetalmicroCTSupplementarymaterialSR.pdf Cite Share Download PDF Status: Published Journal Publication published 24 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 19 Mar, 2025 Reviews received at journal 18 Mar, 2025 Reviewers agreed at journal 13 Mar, 2025 Reviewers agreed at journal 13 Feb, 2025 Reviews received at journal 04 Feb, 2025 Reviewers agreed at journal 04 Jan, 2025 Reviewers agreed at journal 14 Dec, 2024 Reviewers agreed at journal 13 Nov, 2024 Reviewers agreed at journal 11 Nov, 2024 Reviewers invited by journal 01 Oct, 2024 Editor assigned by journal 01 Oct, 2024 Editor invited by journal 17 Sep, 2024 Submission checks completed at journal 17 Sep, 2024 First submitted to journal 08 Sep, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5054349","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":360993978,"identity":"edbef3d2-38e7-4070-8a50-d305d426db3e","order_by":0,"name":"Edwin S. 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Data (points) represent average (± S.E.) for each sampled vertical coordinate, from the apical regions of the living tissue (vertical profile = 0 mm, dashed horizontal blue line, near the polyps) to the basal zone of the skeleton for each fragment (vertical profile = 10 mm, solid blue line and the green band location between them (solid green horizontal lines extracted from Table 1). Curves fitted from LOESS (local regression) and shades represent confidence intervals of the regressions.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/a6841de2259fec75b2fe08d6.png"},{"id":66845625,"identity":"4665c3d9-8df5-4e6c-92e4-b941315c4431","added_by":"auto","created_at":"2024-10-17 05:59:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":146774,"visible":true,"origin":"","legend":"\u003cp\u003eIntra-colonial variation overall and by species for % microporosity (MiP). Loess model by species (A) and overall (B) based on ∆ microporosity (Equation 2). Boxplots by zones for species (C) and overall (D) derived from transformed microporosity (Equation 2). Red dots and vertical lines inside the boxes represent the mean and median, respectively. Asterisks denote significant differences **(p \u0026lt; 0.01) and ***(p \u0026lt; 0.001).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/2e13fd2032706732e91153ae.png"},{"id":66845941,"identity":"001e02c5-c1f0-458f-adae-9ce5c9b1acb6","added_by":"auto","created_at":"2024-10-17 06:07:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":149442,"visible":true,"origin":"","legend":"\u003cp\u003eIntra-colonial variation overall and by species for % macroporosity (MaP). LOESS model by species (A) and overall (B) based on ∆ macroporosity (Equation 1). Boxplots by zones for species (C) and overall (D) derived from transformed macroporosity (Equation 1). Each red dot and vertical line inside the boxes refer to the mean and median, respectively. Asterisks denote significant differences ** (p \u0026lt; 0.01) and *** (p \u0026lt; 0.001), NS denotes no significant differences\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/90b46bda33d959c39b66f311.png"},{"id":66845628,"identity":"e38e6030-e279-4c6e-af4e-ce1c0ef45b3d","added_by":"auto","created_at":"2024-10-17 05:59:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2230976,"visible":true,"origin":"","legend":"\u003cp\u003eSEM Images showing a close-up of micropores (red arrows) and sinuous branching tracks (green lines) in comparison to macropores (blue asterisk) (A). Micropores observed in the green band zone (B), while in some areas, they are surrounded (C) or partially covered (D) by secondary precipitation crystals at the base of the skeleton.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/3c15aea8595538f99dbd662b.png"},{"id":66845627,"identity":"6690c114-773f-4bc4-b321-47e1189b2f27","added_by":"auto","created_at":"2024-10-17 05:59:18","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":114895,"visible":true,"origin":"","legend":"\u003cp\u003ePercentage values of the inter-specific porosity (n=30) for location comparisons in SVF (A) and TP (B) and species comparisons for SVF (C), TP (D), MaP (E), and MiP (F). Correlations for different response variables (G \u0026amp; H). Asterisks denote significant differences * (p \u0026lt; 0.05), ** (p \u0026lt; 0.01).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/3612b9983c8e4d23dcde19eb.png"},{"id":66845629,"identity":"d731b747-76f7-4323-9ed5-fb13d393e951","added_by":"auto","created_at":"2024-10-17 05:59:18","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1629310,"visible":true,"origin":"","legend":"\u003cp\u003eImage and Data Processing. Intra-colonial microenvironments viewed through the stereoscope (A) and measurements taken using ImageJ (B) (note the green zone where the euendolithic community is present within the coral skeleton and the three fragment microenvironments compared (polyps-pink, green band-green \u0026amp; skeleton-gray). \u0026nbsp;Examples for two fragments include: raw tomographies (C), artifact-free images (D), segmentation results (E), and a porosity map depicting 3D axis coordinates (X, Y, Z) and TP values (dark tones means lower TP) (F).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/ed7250ef3261c6d1b8c0efba.png"},{"id":87756837,"identity":"5ef0197b-2f2f-441f-ade0-49cc117a1c44","added_by":"auto","created_at":"2025-07-28 16:09:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5428988,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/599ed79e-4167-4ebe-b95f-fded994b3f02.pdf"},{"id":66845632,"identity":"df22c5ca-dc06-4e58-a330-eaf3aa326ff3","added_by":"auto","created_at":"2024-10-17 05:59:19","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":30858472,"visible":true,"origin":"","legend":"","description":"","filename":"1.UribeetalmicroCTSupplementarymaterialSR.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5054349/v1/c5cf3146474304bfa291c8aa.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The footprint of endolithic algae in shaping the skeletal structure of massive coral skeletons: insights into micro and macro-porosity","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eThere has been growing interest in understanding the ecological role of microborers in coral skeletons. For instance, microbioerosion has been identified as the primary agent of bioerosion during the initial stages of colonizing dead coral substrates\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, with erosion rates reaching up to 1 kg m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e year\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e, where the endolithic community is the primarily responsible for this process\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Coral skeletons provide vital niches for the survival of microorganisms, which vary in response to physical and chemical gradients such as oxygen, light, pH, and porosity, among others\u003csup\u003e\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. It has been observed that algae from the genus \u003cem\u003eOstreobium\u003c/em\u003e (Chlorophyta: Ulvophyceae: Bryopsidales) are the dominant group in the endolithic community of coral skeletons and other marine substrates\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Morphologically, euendoliths create green bands beneath live coral tissues that are visible in cross-sectional cuts of the skeletons\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. While recent research has focused on \u003cem\u003eOstreobium\u003c/em\u003e, there are still many gaps in our understanding of the biology and their intricate relationships with corals\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe ecological role of \u003cem\u003eOstreobium\u003c/em\u003e spp. within the coral holobiont emphasize both beneficial and potentially harmful interactions for the host. On one hand, \u003cem\u003eOstreobium\u003c/em\u003e is thought to engage in mutualistic symbiosis with corals, transferring photo-assimilates and receiving shelter in return\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Likewise, these algae can offer an alternative source of energy to bleached corals (with live polyps), facilitating recovery by reducing light stress \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. On the other hand, \u003cem\u003eOstreobium\u003c/em\u003e significantly contributes to microbioerosion in dead coral skeletons, dissolving up to 20% of deposited CaCO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2,3\u003c/sup\u003e. As other euendoliths, it actively penetrates live coral skeletons, potentially weakening them and increasing vulnerability to mechanical damage\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Nevertheless, the balance of beneficial and detrimental roles of boring microalgae, as well as the exact characteristics of the microenvironments they use or create are not fully understood, and are still a matter of active research\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eMicro-CT (X-ray microtomography) porosity analysis is proposed as an innovative tool for studying micro and macrobioerosion in corals\u003csup\u003e\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. This technique utilizes X-ray beams to scan the three-dimensional structure of coral colonies at a micron-scale resolution\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Calcium carbonate's X-ray attenuation properties distinguish the solid coral skeleton from its macro and micropores, facilitating quantitative porosity analysis\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. In contrast with other techniques, micro-CT offers several advantages, including 3D mapping, high resolution, non-destructive sample handling, and versatile scale assessments\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. There are several studies utilizing micro-CT to analyze the porosity microenvironments of stony coral colonies\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e, but no one investigated the impact of the green band on coral skeleton porosity.\u003c/p\u003e \u003cp\u003eCorals with massive growth, such as \u003cem\u003ePorites\u003c/em\u003e genus, serve as excellent models for studying intra-colonial microenvironments\u003csup\u003e\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. These growth forms usually stratify into different zones along a vertical profile, ranging from the outermost part of the colony (the polyps or living tissue zone) to the base, where the bare skeleton is located. However, since in many cases these skeletons exhibit a green band containing \u003cem\u003eOstreobium\u003c/em\u003e spp.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e and other endolithic microorganisms (e.g., cyanobacteria, fungi and green algae), this band can be delineated as a third zone. These three zones (coral tissue, green band and skeleton) have been proposed and used in various studies, revealing significant changes in physicochemical variables along this vertical gradient\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. For instance, some studies have identified microenvironmental gradients, with higher oxygen levels and pH in the green band and a decreasing pattern toward the base of the skeleton\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. These gradients can be influenced by various factors, such as light availability, nutrient availability, pCO\u003csub\u003e2\u003c/sub\u003e, and water flow\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eColombia has two oceanic basins (Pacific and Caribbean) that exhibit a wide variety of marine environments with contrasting characteristics. In the Caribbean Sea, high impact anthropogenic activities have significantly altered the natural conditions of coral ecosystems\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. Conversely, in the Pacific, anthropogenic impacts have been lower, but environmental conditions are naturally more variable and abrupt, including lower pH conditions and temperature changes due to ENSO\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. In this context, Caribbean reefs are geographically more widespread, with broad bathymetric ranges with a wide diversity of coral species, but generally have low coral cover in most locations\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. In contrast, the Colombian Pacific hosts coral reefs with a more limited geographical distribution and bathymetric range, featuring less diverse reef-forming assemblages, but a generally high coral cover\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Despite these known differences, exploration of potential variations in the intra-colonial physical structure of corals in both Colombian regions remains uncharted.\u003c/p\u003e \u003cp\u003eGiven the ecological and economic significance of coral ecosystems\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e and the context of accelerated coral reef degradation\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, as well as the previously identified knowledge gaps that hinder the understanding of intracolonial microenvironments and the role of the endolithic community in bioeroding corals, this study aims to characterize and to compare the porosity of the internal skeletal areas of \u003cem\u003ePorites lobata\u003c/em\u003e and \u003cem\u003eP. panamensis\u003c/em\u003e from the Colombian Pacific and \u003cem\u003eP. astreoides\u003c/em\u003e from the Caribbean, using the micro-CT technique. Specifically, the objective was to compare the vertical porosity profile of skeletal fragments, to determine whether these patterns vary with interspecific factors like location and coral species and finally to propose a model describing intracolonial variation. Additionally, Scanning Electron Microscopy (SEM) was employed to explore the morphology of pores and traces of bioerosion in these coral skeletal fragments.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Sample collection\u003c/h2\u003e \u003cp\u003eThirty (30) samples of coral skeletons corresponding to \u003cem\u003ePorites astreoides\u003c/em\u003e (Lamarck, 1816\u003cem\u003e), P. lobata\u003c/em\u003e (Dana, 1846) and \u003cem\u003eP. panamensis\u003c/em\u003e (Verrill, 1866) were selected from the Natural History Museum at Universidad de Los Andes (Bogota, Colombia). \u003cem\u003ePorites astreoides\u003c/em\u003e samples (n\u0026thinsp;=\u0026thinsp;10) were collected in 2018 from West View, San Andres Island (Caribbean Sea) (12\u0026deg;31'15.45\"N, 81\u0026deg;43'48.60\"W) from a bathymetric range between 5-35m. \u003cem\u003ePorites lobata\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;10) and \u003cem\u003eP. panamensis\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;10) were collected in 2019 from Gorgona Island (Colombian Pacific) at a depth of 12m (2\u0026deg;59'24.19\"N, 78\u0026deg;10'7.12\"W) (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Using SCUBA, all samples were extracted with hammer and chisel, placed in plastic bags, and labelled for subsequent morphological identification based on the characteristics described in the literature\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e,\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Porosity Analysis\u003c/h2\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1. Sample Preparation\u003c/h2\u003e \u003cp\u003eFragments of ~\u0026thinsp;1cm\u0026sup3; were cut using a Proxxon MBS 240/E diamond micro bandsaw. Photographs of all faces of the fragments were taken with Lumenera's INFINITY1-1M camera integrated with a JSZ6 stereoscope. A scale was included in each image to provide a reference for the fragment size. ImageJ software was employed for all measures such as polyp zone, green band and skeleton (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The samples were labeled and grouped in 50ml Falcon tubes, with 5 to 6 fragments separated by a plastic layer. These samples were subsequently sent to the X-ray Micro-CT Laboratory at the Australian National University (ANU, Canberra, Australia) for processing with a Micro-CT scanner (CITES permit #46697).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2. Tomography Processing\u003c/h2\u003e \u003cp\u003eEach tomography produced a three-dimensional (3-D) NetCDF format (.nc) that had an original dimension of 1400 x 1400 x 3280 voxels (three-dimensional pixels) and a minimum resolution of 24.3\u0026micro;m (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC). Subsequently, 3-D images were uploaded to the WebMango platform (Australian National University), that facilitates tomographic modifications through a system of image filters. The sequence of this process involved three general steps: i) masking filter (removal of artifacts such as the Falcon tube and fragment separators) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eD), ii) segmentation filter (division of the image into phases or materials) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eE), and iii) porosity analysis (quantitative estimation of in the skeletal structure) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eF)\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Each voxel in the tomography belongs to one of four categories (colors). Red voxels denote areas where the skeleton is dense and solid. Black voxels represent air or embedded void spaces (macropores). Green areas represent an intermediate phase between the solid (red) and air (black) and they are technically termed micropores; those pores with sizes smaller than the tomographic resolution (24.3\u0026micro;m), which influence tomographic intensity and are thus quantifiable\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Gray-colored voxels are referred to as mask, primarily indicating the volume within the tomography that does not belong to the colony. However, in specific cases, they may denote voids within the skeletal structure, which, due to their significant size, are connected to the exterior of the colony and are not considered as pores.\u003c/p\u003e \u003cp\u003eUsing the volumes of the segmented image phases, a porosity analysis was performed to calculate four variables related to the total volume of the colony: i) the relative volume (%) of microporosity (MiP), ii) macroporosity (MaP), iii) the total volume (%) of porosity (TP), which is the sum of macro and microporosity percentages, and iv) the solid volume fraction (SVF), representing the relative volume (%) of the solid skeletal structure (CaCO\u003csub\u003e3\u003c/sub\u003e). Calculations were conducted along all three axes of the fragment-3D (X, Y, Z) at 0.9*0.9*0.9mm distance intervals. Thus, this process generated a porosity map that replicated the original fragment's shape, overlaying it with numerical values for the estimated variables (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eF). This approach facilitated the observation of changes or gradients in these four variables (MiP, MaP, TP and SVF) along all three axes (X, Y, Z) of each fragment, enabling the assessment of skeletal variation, as well as the general differences among fragments from different species or locations in the Caribbean and the Pacific.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Intra-colonial scale\u003c/h2\u003e \u003cp\u003eThe Z-axis is referred to as the vertical profile (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eF), enabling the examination of patterns within skeletal microenvironments. Notably, not all vertical profiles of the fragments were suitable for intraspecific analysis due to physical damage. Nevertheless, the fragments excluded from this analysis were still useful for interspecific comparisons (next section). Consequently, four fragments without physical damage were selected for each species (12 analyzed fragments). The zones observed in the stereoscope for the three microenvironments (coral tissue, green band \u0026amp; skeleton) along the vertical profile were assigned to each fragment based on measurements taken in ImageJ (see section \u003cspan refid=\"Sec9\" class=\"InternalRef\"\u003e2.2.1\u003c/span\u003e). For every fragment, average porosity (\u0026plusmn;\u0026thinsp;S.E.) was graphed for the different coordinates along the vertical profile.\u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1. Coordinates Transformation\u003c/h2\u003e \u003cp\u003eTo compare skeletal variation among selected fragments, the coordinates of the three axes (X, Y, Z) of the porosity maps were transformed into a relative scale using Eq.\u0026nbsp;1 (Zjinorm). This transformation allowed for comparisons of fragment sizes and facilitated locating porosity data within the intra-colonial space with a common origin for all fragments. After this normalization, the scale was transformed into millimeters (mm) (Zjimm) (Eq.\u0026nbsp;1) based on a conversion factor (8mm), representing the length of the largest porosity map sampled in the Z-axis, and a correction factor (0.45mm), since each porosity point better represents the middle of the range sample interval of 0.9mm (see section \u003cspan refid=\"Sec10\" class=\"InternalRef\"\u003e2.2.2\u003c/span\u003e). For the Z-axis, the coordinate scale ranged between 0 and 10mm for better visualization, where the limit of 10 referred to the most basal region of the skeleton, and the limit of 0 indicated the apical areas of the colony where living tissue (polyps) was situated. The same transformation was applied to the X and Y axes, but no clear porosity patterns were expected among fragments, as the most common stratification mentioned in the literature occurs along the vertical axis (Z-axis)\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. However, some results for these two axes are briefly discussed in the present study. Eq.\u0026nbsp;1 represents coordinate transformation to mm for each fragment along the Z axis (Zjimm):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{Zji}_{mm}=\\:{(Zji}_{norm}*\\:8\\:mm)+0.45\\:mm\\:;{\\:Zji}_{norm}=\\:\\frac{Zji-{Zji}_{min}\\:}{\\:{ZI}_{max}-\\:{ZI}_{min}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere Zjinorm represents the normalized j-coordinate for fragment i, dependent on the minimum coordinate value of the i fragment (Zimin) as well as the maximum (ZImax) and minimum (ZImin) coordinates of the largest selected fragment I. It is important to note that the denominator is relative to the largest fragment (I) for standardized size comparisons among all selected fragments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e2.3.2. Variable transformation\u003c/h2\u003e \u003cp\u003eThe intra-colonial analysis for MiP, MaP, TP and SVF involved transforming the values and constructing models to explain the vertical profile of the selected fragments. Two transformations were applied to the response variables, involving the calculation of deltas (∆) and data normalization (Eq.\u0026nbsp;2). The purpose of this equation is to preserve intra-colonial variation since statistics with raw (non-normalized) values tend to homogenize profile gradients, which would result in a vertical profile that becomes linear and fails to display the porosity fluctuations in the intra-colonial environments. Eq.\u0026nbsp;2 represents transformation of response variables (MiP, MaP) for Intra-specific analysis:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:{Vji}_{norm}=\\:\\frac{\\varDelta\\:\\:}{{\\varDelta\\:}_{max}}\\:;\\:\\varDelta\\:\\:=\\:Vji-{Vi}_{min}\\:;\\:\\:{{\\varDelta\\:}_{max}\\:=Vi}_{max}-{Vi}_{min\\:}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere, Vjinorm represents the normalized j-value of fragment i for the variable V. It is calculated as the delta between the unnormalized value (Vji) and its corresponding minimum value within the same fragment (Vimin) divided by the difference between the maximum value (Vimax) and the minimum value (Vimin).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Inter-specific scale\u003c/h2\u003e \u003cp\u003eThe total number of samples analyzed (n\u0026thinsp;=\u0026thinsp;30) were used to ensure a more robust statistical analysis. The response variables were not transformed, as intra-colonial gradients were not considered at this scale. Consequently, each fragment had only one porosity value, as opposed to a porosity map per fragment. To achieve this, the porosity map values of each fragment were averaged into a single value for MiP, MaP, TP and SVF. At this inter-specific scale, the goal was to identify differences among all fragments between locations (Caribbean and Pacific) and species.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Statistical analysis\u003c/h2\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e2.5.1. Intra-colonial statistics\u003c/h2\u003e \u003cp\u003eLocal Polynomial Regression (LOESS) models were used to elucidate intra-colonial variation of the skeletal fragments, which consider local variation within a data series, based on a span of analyzed data points regarded as neighbors. The specific variation of intra-colonial porosity data points (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF) was fitted into single curve across the axes of the fragments (X, Y, Z). Descriptive statistics, encompassing means and standard errors, were computed for the 12 samples. ANOVA and Tukey\u0026rsquo;s Honestly Significant Difference (HSD) test were performed to assess statistical differences between the three microenvironment zones (polyps, green band, and skeleton), following verification of normality and homoscedasticity assumptions. Finally, Spearman Correlation test was conducted between pairs of groups of response variables along the Z-axis of each fragment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e2.5.2. Inter-specific statistics\u003c/h2\u003e \u003cp\u003eANOVA and the Tukey\u0026rsquo;s Honestly Significant Difference (HSD) test for the response variables MiP, MaP, TP and SVF were performed for species-level comparisons with balanced n-values, after verifying the assumptions of normality and homoscedasticity. For comparing locations, a non-parametric Kruskal-Wallis\u0026rsquo;s test was used, taking into account the imbalance in sample sizes between the Caribbean (n\u0026thinsp;=\u0026thinsp;10) and the Pacific (n\u0026thinsp;=\u0026thinsp;20), following inter-specific Spearman correlation test among response variables.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Scanning Electron Microscopy\u003c/h2\u003e \u003cp\u003eAdditional fragments (n\u0026thinsp;=\u0026thinsp;19) of ~\u0026thinsp;1.5cm long of the same coral colonies used for micro-CT analysis were obtained by fracturing them (hammer and chisel). The objective was to secure a vertical profile like the one illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA, encompassing tissue, the green band, and the base. The samples underwent a hydrogen peroxide treatment to eliminate any remaining tissue in the colony, followed by rinsing with distilled water and overnight drying. To enhance conductivity, the unobserved faces of the fragments were covered with aluminum foil and affixed to a metallic surface using SEM conductive double-sided carbon tape. Additionally, a layer of gold was applied via vacuum coating prior to examination with a Tescan Vega 4 Scanning Electron Microscope. For each fragment, a general image was captured at 30X, followed by higher magnification close-ups in each of the three microenvironments (Coral tissue, green band \u0026amp; skeleton) at 100X, 500X, 1000X, 5000X, and 10000X to capture the porosity, micropore morphology, and bioerosion traces in the samples based on previous descriptions found in the literature\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. RESULTS","content":"\u003cp\u003eClear patterns were identified for microporosity-MiP, macroporosity-MaP, solid volume fraction-SVF, and total porosity-TP, at different scales of analysis. At the intra-colonial scale, MiP and MaP proved to be more relevant. Conversely, in the inter-specific scale, which involves the comparison between species and geographical locations, the variables SVF and TP gained more significance.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Intra-colonial porosity\u003c/h2\u003e \u003cp\u003eThe average MiP across fragments indicates that micropores represent less than 11% of the total volume, while MaP accounts for up to 47% (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The mean SVF (overall 52%) exceeded TP (overall 42.7%) for most fragments (except for 15G and 28G), indicating that the percentage of CaCO\u003csub\u003e3\u003c/sub\u003e is higher than the air spaces. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the vertical profiles of fragments where the apical zone corresponds to the coral tissue at 0 mm, and the basal zone corresponds to the skeleton at approximately 10 mm (samples were cut at this size). However, the common total vertical length recorded by the porosity map (Z length Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) ranged between ~\u0026thinsp;5 mm to ~\u0026thinsp;9 mm because not all fragments had the same vertical length, due to variations in the cuts and segmentation results. Additionally, the observed green band locations varied between 1.1 mm and 3.9 mm along the vertical profile. Thus, this amplitude was used to distinguish the green band microenvironment from other zones within the fragment.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAverage\u0026thinsp;\u0026plusmn;\u0026thinsp;standard errors (s.e.m) for the calculated response variables (MiP, MaP, TP, SVF) of the selected coral skeletal fragments: green band width (GB) in the vertical profile, microporosity (MiP), macroporosity (MaP), total porosity (TP) and solid volume fraction (SVF). Notably, the percentages provided here are averages, thus, the sum of TP and SVF does not necessarily equal 100%. P\u0026thinsp;=\u0026thinsp;\u003cem\u003ePorites panamensis;\u003c/em\u003e L\u0026thinsp;=\u0026thinsp;\u003cem\u003eP. lobata\u003c/em\u003e; A\u0026thinsp;=\u0026thinsp;\u003cem\u003eP. astreoides.\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eID\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDepth (m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eZ length (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGB (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMiP %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMaP %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eTP %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eSVF %\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePacific\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e 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\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e36G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePacific\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.6\u0026ndash;2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e5.7\u0026thinsp;\u0026plusmn;\u0026thinsp;.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e47.0\u0026thinsp;\u0026plusmn;\u0026thinsp;.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e 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char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.3\u0026ndash;3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e42.3\u0026thinsp;\u0026plusmn;\u0026thinsp;.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e53.1\u0026thinsp;\u0026plusmn;\u0026thinsp;.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e19G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePacific\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.5\u0026ndash;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e3.9\u0026thinsp;\u0026plusmn;\u0026thinsp;.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e44.0\u0026thinsp;\u0026plusmn;\u0026thinsp;.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e47.9\u0026thinsp;\u0026plusmn;\u0026thinsp;.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e48.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePacific\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.9\u0026ndash;3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e7.6\u0026thinsp;\u0026plusmn;\u0026thinsp;.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e29.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e37.4\u0026thinsp;\u0026plusmn;\u0026thinsp;.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e57.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e39G\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePacific\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.7\u0026ndash;3.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e5.7\u0026thinsp;\u0026plusmn;\u0026thinsp;.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e36.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e42.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e52.9\u0026thinsp;\u0026plusmn;\u0026thinsp;.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCaribbean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.8\u0026ndash;2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e7.3\u0026thinsp;\u0026plusmn;\u0026thinsp;.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e36.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e43.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e51.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCaribbean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.5\u0026ndash;1.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e5.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e35.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e41.3\u0026thinsp;\u0026plusmn;\u0026thinsp;.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e55.7\u0026thinsp;\u0026plusmn;\u0026thinsp;.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCaribbean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.3\u0026ndash;3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e7.2\u0026thinsp;\u0026plusmn;\u0026thinsp;.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e27.5\u0026thinsp;\u0026plusmn;\u0026thinsp;.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e34.6\u0026thinsp;\u0026plusmn;\u0026thinsp;.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e61.9\u0026thinsp;\u0026plusmn;\u0026thinsp;.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCaribbean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.2\u0026ndash;3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e10.7\u0026thinsp;\u0026plusmn;\u0026thinsp;.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e20.1\u0026thinsp;\u0026plusmn;\u0026thinsp;.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e30.8\u0026thinsp;\u0026plusmn;\u0026thinsp;.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e64.0\u0026thinsp;\u0026plusmn;\u0026thinsp;.36\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOverall\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.1\u0026ndash;3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e7.1\u0026thinsp;\u0026plusmn;\u0026thinsp;.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e35.6\u0026thinsp;\u0026plusmn;\u0026thinsp;.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e42.7\u0026thinsp;\u0026plusmn;\u0026thinsp;.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e52.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eRepeated patterns of both variables (MiP and MaP) were observed along the vertical axis of the 12 analyzed fragments (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The % of MiP exhibits a monomodal curve with MiP peaks (zones of high MiP) related to the observed green band and an asymmetric shape towards the apical regions of the fragment. Conversely, MaP curves tend to decrease in the areas near the green band for the majority of the profiles. For the later variable, the monomodal behavior is not as evident as in MiP, but the asymmetry of the valleys towards the apical regions is preserved. Regarding the vertical profiles of TP and SVF (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), the curve shapes do not exhibit the prominent peaks and valleys observed in MiP and MaP. However, a strong similarity between TP and MaP profiles is apparent, with some curves almost mirroring each other in shape (e.g., 47G \u003cem\u003eP. panamensis\u003c/em\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Additionally, for SVF, the notable pattern observed is its inverse graphical correlation with MaP and TP.\u003c/p\u003e \u003cp\u003eThe location (note that location\u0026thinsp;\u0026ne;\u0026thinsp;magnitude) of peaks and valleys of the response variables in the vertical profile was correlated (Spearman correlation test) with the observed location of the green band in the stereoscope (solid horizontal green lines Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A positive and significant correlation was found between MiP peaks and the observed green band location (ρ\u0026thinsp;=\u0026thinsp;0.66, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and between MaP valleys and the green band location (ρ\u0026thinsp;=\u0026thinsp;0.72, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). No significant differences were found between the locations of the green band and the locations of MiP peaks (ANOVA: F\u0026thinsp;=\u0026thinsp;0.4, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) / MaP valleys (ANOVA: F\u0026thinsp;=\u0026thinsp;0.9, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Spearman correlation across the fragment's vertical profile (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) detected an inverse relationship between MiP and MaP (ρ=-0.67, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), where MiP increases as MaP decreases in the vertical profile (e.g., 10G \u003cem\u003eP. lobata\u003c/em\u003e Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The other variables exhibit the expected correlations, with TP being inversely correlated with SVF (ρ=-0.98, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and MaP positively correlated with TP (ρ\u0026thinsp;=\u0026thinsp;0.96, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The MaP\u0026ndash;TP correlation indicates that macropores, due to their large size, have the greatest influence on changes in the total porosity (TP) of the fragment, emphasizing the similarity between the vertical profiles of these two variables.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIntra-colonial scale Spearman correlations. Groups between response variables in the vertical profile (Z) of the fragments. The Asterisks represent significant correlations with p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMicro.Porosity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMacro.Vol.Fraction\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePorosity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSolid.Vol.Fraction\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMicroporosity (MiP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMacroporosity (MaP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.67***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal porosity (TP)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.46***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.96***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSolid volume fraction (SVF)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.32***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.90***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.98***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eBased on the LOESS model for microporosity for each species and an overall model (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA-B), there is evidence for the influence of the endolithic community on coral skeletal structure, albeit some variation in peak height and amplitude. \u003cem\u003ePorites panamensis\u003c/em\u003e exhibited the highest peak (∆ max\u0026thinsp;=\u0026thinsp;5.61%), followed by \u003cem\u003eP. lobata\u003c/em\u003e (∆max\u0026thinsp;=\u0026thinsp;4.65%), and \u003cem\u003eP. astreoides\u003c/em\u003e (∆ max\u0026thinsp;=\u0026thinsp;3.93%). The overall model shows a maximum peak of 4.42% compared to the reference minimum value. The final pattern maintains the relationship observed, where there is an asymmetry towards the apices of the skeleton (vertical profile\u0026thinsp;\u0026lt;\u0026thinsp;5 mm). Considering that the average MiP of all fragments is ~\u0026thinsp;7% (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), the microporosity in the green band accounts for more than half of the average microporosity that can be present in colonies of these species. Significant differences were found for the three zones of coral fragments (Tukey HSD test) for all species and in the overall model. The microporosity of the green band zone is significantly different from the microporosity of the most extreme zones of living tissue and skeleton (supplementary material) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). Likewise, the single model maintains statistical differences between the three zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). These results indicate that the mean and median values found in the green band are significantly higher than those at the opposite ends of the other zones, thus, there is more similarities at the boundaries of the zones, and therefore, the changes between the different bands of the fragment are gradual across the vertical profile.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe LOESS model of MaP (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-B) shows low ∆ values forming valleys in the regions of the green band. The largest difference (∆max - ∆min) between the valleys of the green bands and the other zones of the vertical profile (skeleton and living tissue) was found in \u003cem\u003eP. lobata\u003c/em\u003e (~\u0026thinsp;12%) with a ∆min of ~\u0026thinsp;12% and a ∆max of ~\u0026thinsp;24%. In \u003cem\u003eP. panamensis\u003c/em\u003e the difference was 10% with ∆min of ~\u0026thinsp;12% and a ∆max of ~\u0026thinsp;22%. Lastly, \u003cem\u003eP. astreoides\u003c/em\u003e had a total difference of 9.5% with a ∆min and ∆max of 9.3% and 18.8%, respectively. The overall model showed a MaP valley with a ∆min of 12.8% in the green band and an increase in MaP (∆max of ~\u0026thinsp;19%) towards the basal zones of the fragment, i.e., a total difference of 6.2%. Like the peaks of microporosity, the Map valleys of the general and species-specific models are located towards the apical regions of the fragments (vertical profile\u0026thinsp;\u0026lt;\u0026thinsp;5 mm).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe MaP in the different zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC-D) shows the variations in the proposed LOESS models (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-B). For \u003cem\u003eP. panamensis\u003c/em\u003e, the green band zone did not show significant differences for MaP compared to the other zones of the fragment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Similarly, in \u003cem\u003eP. astreoides\u003c/em\u003e, MaP values of the green band are not different from those of the living tissue, but they are different from the more basal zones (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Only for \u003cem\u003eP. lobata\u003c/em\u003e, the significant differences of the green band are clear compared to the other zones (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The overall model maintains the variations seen at the species level; however, the most basal extreme of the fragment, at the 8.45mm band in the vertical profile, are not different from the green band, mainly due to the high dispersion of values in this zone (whisker amplitude). In this case, it was compared with the previous band (7.45 mm), where significant differences are found (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), as is also the case when comparing the green band to the living tissue (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eFor SVF and TP, the intra-colonial results from both the overall and species models display inconsistencies. While the models exhibit some variations along the vertical profile, these variations do not consistently repeat in the same manner among the species models (supplementary material). Consequently, the overall LOESS model exhibited a vertical profile that is predominantly linear, with no significant differences observed between the three microenvironments (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (supplementary material). Despite the lack of consistent intra-specific variation, these variables are retained in the analysis because their significance becomes more apparent when discussing inter-specific differences.\u003c/p\u003e \u003cp\u003eThe SEM images revealed traces of the endolithic community in the selected colonies and in different zones of the fragments. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA displays the typical structural differences between macro and micropores. The macropores are evident over the minimum resolution of micro-CT analysis (24.5 \u0026micro;m) and are even recognizable without any special equipment, as they comprise a significant proportion of the fragment volume. Conversely, the micropores, especially those related to the endolithic community, can be seen with a frequent diameter\u0026thinsp;\u0026lt;\u0026thinsp;10 \u0026micro;m (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-B). Additionally, these are connected to tunnels that resemble the microborers\u0026rsquo; filaments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA green bars) of the same diameter as the micropores. Even when the micro-CT analysis revealed that MiP is higher in the green band, traces of these micro tunnels or sinuous branching tracks\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e were seen qualitatively with SEM in all fragment zones, although less frequently in the coral tissue. The latter means that the euendolithic community is present along the vertical profile although in lower densities than the green band. However, one particularity is that these micropores were commonly surrounded by crystal-shaped structures in the skeleton zone (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC) compared to a flatter surface in the green band micropores (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). In some cases, these crystals cover a large part of the pore space (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Inter-specific porosity\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the most relevant results conducted for the overall sample fragments (n\u0026thinsp;=\u0026thinsp;30). Between locations (Caribbean and Pacific), significant differences (Kruskal-Wallis) were found only for SVF (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA) (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and TP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB) (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), indicating that fragments from the Caribbean have a higher solid volume (mean SVF\u0026thinsp;~\u0026thinsp;60%) and a lower total porosity volume (mean TP\u0026thinsp;~\u0026thinsp;40%) than in the Pacific (mean SVF\u0026thinsp;~\u0026thinsp;50% and TP\u0026thinsp;~\u0026thinsp;45%). Although, no significant differences were detected between locations for MaP and MiP (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05), the values indicate that, on average, Pacific fragments exhibit MiP equivalent to 7.2% of the total colony volume, compared to 6.1% for the Caribbean. Concerning MaP, the mean value for the Pacific species (36.7%) is higher than the mean value of the Caribbean species (33%). These percentages align closely with the averages observed (MiP\u0026thinsp;~\u0026thinsp;7%, MaP\u0026thinsp;~\u0026thinsp;36%) for the 12 selected fragments from the intra-colonial models.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe comparison between species shows significant differences for SVF (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC) and MiP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eF), where \u003cem\u003eP. lobata\u003c/em\u003e and \u003cem\u003eP. panamensis\u003c/em\u003e were not statistically different to each other but different from \u003cem\u003eP. astreoides.\u003c/em\u003e For the variable TP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD) and MaP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eE), only \u003cem\u003eP. lobata\u003c/em\u003e is statistically different from \u003cem\u003eP. astreoides\u003c/em\u003e, which has the highest average value of SVF (58%), and the lowest values of TP (39%) and MaP (33%), followed by \u003cem\u003eP. panamensis\u003c/em\u003e (SVF\u0026thinsp;=\u0026thinsp;51%, TP\u0026thinsp;=\u0026thinsp;41%, MaP\u0026thinsp;=\u0026thinsp;32%) and \u003cem\u003eP. lobata\u003c/em\u003e with the lowest values of SVF (49%) but the highest values of TP (46%) and MaP (40%). These results indicate that species from the Pacific are more porous than species from the Caribbean. However, in the case of MiP (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eF), the differences between species do not align with the locations, as the two Pacific species are statistically different from each other (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) but not different from \u003cem\u003eP. astreoides\u003c/em\u003e. For MiP, \u003cem\u003eP. panamensis\u003c/em\u003e has the highest value (9.3%), followed by \u003cem\u003eP. astreoides\u003c/em\u003e (6.1%), and \u003cem\u003eP. lobata\u003c/em\u003e (5.3%).\u003c/p\u003e \u003cp\u003eThe inverse relationship (Pearson correlation) between MaP and MiP at the inter-specific level (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eG), where higher MiP values coincide with lower MaP values (R=-0.77) are in accordance with the intra-colonial results (R=-0.6), indicating that it operates at different scales of analysis. The remaining results demonstrate the expected typical relationship, such as SVF being inversely correlated with TP (R=-0.96) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eH) and the positive correlation between TP and MaP (R\u0026thinsp;=\u0026thinsp;0.98) (supplementary material).\u003c/p\u003e \u003c/div\u003e"},{"header":"4. DISCUSSION","content":"\u003cp\u003eOur findings revealed that average microporosity values (~\u0026thinsp;7%) were consistent with those reported for coral fragments of \u003cem\u003ePocillopora\u003c/em\u003e (~\u0026thinsp;5\u0026ndash;10%) and \u003cem\u003eAcropora\u003c/em\u003e (~\u0026thinsp;12\u0026ndash;15%) under normal growth conditions\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. However, the average macroporosity of 36% was higher than the ~\u0026thinsp;15\u0026ndash; 25% reported by Leggat et al.\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. This might be attributed to the massive growth form of our coral skeletal fragments. Similarly, Krause et al.\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e documented a higher total porosity of ~\u0026thinsp;51% for \u003cem\u003ePorites\u003c/em\u003e, exceeding the average TP of ~\u0026thinsp;43% in our study. This observation aligns with previous findings indicating that massive growth species like \u003cem\u003ePorites\u003c/em\u003e spp., tend to exhibit higher porosity (i.e., less dense skeletons) compared to branched and foliaceous species\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. The observed differences could also be related to the life-history of our coral fragments, as species-specific biogeographical settings and associated environmental conditions can influence skeletal density and porosity\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Further comparative studies utilizing micro-CT porosity analysis across diverse coral species are needed to elucidate these relationships.\u003c/p\u003e \u003cp\u003eThe position of the green band, indicative of mobile phototrophic community, was generally observed near the apical zones of the fragments, consistent with their light-seeking behavior. In our study, the green band in \u003cem\u003ePorites\u003c/em\u003e species was located between 1 mm and 5 mm from the apical zone (living tissue), with a maximum thickness of 4mm. While K\u0026uuml;hl et al.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e reported a slightly deeper green band position in \u003cem\u003ePorites\u003c/em\u003e (5\u0026ndash;10 mm from the apical perimeter), their measured thicknesses (3\u0026ndash;5 mm) align with our results. Similarly, other studies have documented green band positions ranging from 2mm to 6mm below the coral surface, with widths between 2 mm and 4 mm\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, further supporting our observations. The asymmetry of porosity curves and the apical positions of the green band suggest a correlation between porosity peaks and valleys and areas of higher light intensity within the colony, as previously documented\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. This alignment between asymmetric micro- and macroporosity curves within the green band is also consistent with reported patterns of intra-colonial gradients\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe observed positive correlation and non-significant differences between the peak/valley\u0026rsquo;s locations of micro- and macroporosity, and the locations of the green band observed with the stereoscope method, indicate a consistent alignment between the two methodologies. However, stereoscopic measurements capture only surface features. While the green band thickness and position may differ between the surface and the interior of the coral skeleton, micro-CT provides a more precise 3-D analysis\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Furthermore, the coral skeleton itself acts as a record keeper, increasing the uncertainty regarding the exact position of the green band\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Traces of the green band, such as elevated microporosity, may persist in the skeleton even after the endolithic community has migrated, for example, as the colony grows and the community shifts towards areas of higher light intensity near the polyps\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Despite these potential sources of variations, our results show strong correlations between the positions and amplitudes (in mm) of the green band and the vertical profiles of micro- and macroporosities, supporting the use of micro-CT for delineating intra-colonial variation.\u003c/p\u003e \u003cp\u003eThe consistent intra-colonial porosity patterns observed across sampled fragments and species, provide insights into the microenvironments of massive \u003cem\u003ePorites\u003c/em\u003e species. The areas with a high concentration of the endolithic community (green band) exhibited significantly higher microporosity values compared to other microenvironments within coral skeleton. These observations align with other studies in which the metabolic activity within the green band leads to the formation of channels less than 10\u0026micro;m in diameter\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e, classified as micropores in tomographic analysis\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Our micro-CT values revealed an average microporosity increase of approximately 4% within the green band. While this suggests a low overall influence of the endolithic community in the skeletal porosity, it is important to note that this increase represents a substantial proportion of the total average microporosity (7%) observed in the analyzed fragments. Therefore, the green band represents the zone with the maximum achievable microporosity within analyzed colonies.\u003c/p\u003e \u003cp\u003eWhile the coral skeleton preserves traces of past endolithic activity\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e, the observed decrease in microporosity below the green band suggests an active modification of the skeletal structure. Although microbioerosion by the endolithic community initially increases this value, why does not this increase persist below the green band? This process appears to be counteracted by secondary reprecipitation of calcium carbonate. SEM images (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) reveal crystals characteristics of this secondary precipitation within the green band, supporting findings from other studies\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. These studies demonstrate that endolithic algae, such as \u003cem\u003eOstreobium\u003c/em\u003e, can transport micro-eroded calcium from apical tips to the thallus base, where it re-precipitates as secondary aragonite along the pore edges. This \"porosity filling\" process, involves the cementation and compaction of crystals of less than 10\u0026micro;m in width, in a form of early diagenesis, leading to observable changes within the coral skeleton as observed in our study and elsewhere\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. This phenomenon likely contributes significantly to the gradual decrease in microporosity observed below the peak. Such evidence suggests new indirect relationship between endolithic community and coral host, supporting the mutualistic hypothesis proposed by Schlichter et al.\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, and corroborated by more recent studies\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. This hypothesis proposed that while endolithic activity can initially increase porosity, it also triggers secondary processes that ultimately enhance skeletal density and potentially benefit the coral holobiont.\u003c/p\u003e \u003cp\u003eUnexpectedly, the green band zone exhibits significantly lower macroporosity values compared to the coral tissue and skeleton. The minimum values observed across the entire vertical profile were consistently located within the green band, with an approximately 13% decrease, which represents a substantial mitigation of macroerosion, equivalent to approximately one-third of the typical macroporosity value (47%). In this context, our findings support new evidence of the role of the endolithic community to the coral skeletal matrix and coral-reef framework. The observed macroporosity valleys within the green band, suggest that the endolithic community, through direct and/or indirect mechanisms, actively influences the physical structure of the macropores within this skeletal region. Furthermore, the negative correlations between micro- and macroporosity, and to a lesser extent between micro- and total porosity, suggest a potential link between the increased microporosity and a reduction in both macropore size and overall skeletal porosity. This reduction in porosity could be attributed to the infilling of larger pores by secondary aragonite precipitation, as evidenced by the previously discussed SEM images and supporting literature.\u003c/p\u003e \u003cp\u003eWhile the specific mechanisms by which the green band is related to macropore reduction in the CaCO\u003csub\u003e3\u003c/sub\u003e skeleton are beyond the scope of this article, existing research suggest a complex interplay between endolithic activity and skeletal porosity. This is achieved through a mechanism of enhanced photosynthetic activity within the green band, which captures CO\u003csub\u003e2\u003c/sub\u003e increasing the pH, thereby diminishing chemical erosion by CaCO\u003csub\u003e3\u003c/sub\u003e dissolution\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. This pH increase potentially minimizes acidification-induced erosion, resulting in fewer air spaces and lower overall porosity within the skeleton. However, this apparent beneficial effect is offset by the increased metabolic activity and population density of the endolithic community that leads to greater microbioerosion in the form of tunnels, potentially causing skeletal damage (up to 7%)\u003csup\u003e14,36,38,43,46\u003c/sup\u003e. Essentially, the benefit of acidification mitigation also implies potential structural weakening through microboring. This idea is supported by observations of species inhabiting different pH environments\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. For example, we found Pacific species like \u003cem\u003eP. lobata\u003c/em\u003e, which typically experience lower pH and different carbonate chemistry conditions than the Caribbean Sea\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e, exhibited more macropores within the skeletons compared to Caribbean species like \u003cem\u003eP. astreoides\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB-E) as has been found in other studies\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. This suggests a potential link between pH, endolithic activity, and porosity, although further research is needed to confirm a direct cause-effect relationship.\u003c/p\u003e \u003cp\u003eExamining the precise effect of endolithic community on coral colonies using true colonial controls (fragments lacking a visible green band) presents significant challenges. Firstly, endolithic algae, such as \u003cem\u003eOstreobium\u003c/em\u003e spp., colonize coral skeletons early in the life cycle\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. This early colonization makes it difficult to find coral fragments devoid of a green band for control groups, as colonization is likely throughout the coral\u0026rsquo;s lifespan\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Secondly, the absence of a visible green band does not guarantee the absence of endolithic activity. While chlorophyll pigmentation might fade over time (weak signal), the physical marks of microerosion, such as peaks in porosity and endolithic channels seen in SEM, persist\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. This makes coral skeletons a valuable historical record of past endolithic activity\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. As a point of comparison, rhodolite fragments were also analyzed in this study and exhibited no clear zonation or patterns in their vertical profiles, indicating that the observed patterns in the coral skeletons are indeed species-specific (supplementary material).\u003c/p\u003e \u003cp\u003eThe interspecific analysis further provides evidence for the relationship between coral species, geographic location and skeletal porosity, which helps to support the intra-colonial analysis. Although solid volume fraction (SVF), total porosity (TP), and macroporosity values support this interspecific pattern linked to acidification and geographic variation (Caribbean vs Pacific), microporosity values surprisingly do not. This suggests that microporosity unlike the other porosity measures, is less influenced by locations or species. Instead, it appears more sensitive at the microenvironmental factors or gradients within the coral colony (intra-colonial scale). This further supported by the observations that microporosity exhibits most distinct patterns within the vertical profile analyzed in this study.\u003c/p\u003e \u003cp\u003eIn conclusion, our study provides insights into the relationship between endolithic community and skeletal porosity of massive \u003cem\u003ePorites\u003c/em\u003e species, revealing distinct porosity patterns across three intra-colonial zones, suggesting a key role for endolithic metabolic activity in shaping the skeletal structure. Specifically, we observed a consistent increase in microporosity and a decrease in macroporosity within the green zone across all three studied species, regardless of their location, depth, or environment. This suggests a universal influence of endolithic communities on \u003cem\u003ePorites\u003c/em\u003e skeletal structure. The green band is of particular interest, potentially mitigating total porosity by re-mineralization and porosity filling activity. Our findings highlight the influence of multiple intracolonial gradients playing a crucial role in the final distribution of porosity along the vertical profile. Therefore, we propose that endolithic communities exert a significant influence on the structural properties of the coral skeleton (i.e., macroporosity and total porosity), extending beyond the previously documented mutualistic benefits.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eAUTHOR CONTRIBUTIONS STATEMENT\u003c/h2\u003e \u003cp\u003eJAS, CEG, AA conceived de study and refined the methods for analyzing the data. ESU, AM obtained and analyzed the data and wrote the first draft of the manuscript. ESU, AM, JAS, CEG, AA provided general feedback for the manuscript. All authors approved the final version of the manuscript.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCOMPETING INTEREST\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJAS, CEG, AA conceived de study and refined the methods for analyzing the data. ESU, AM obtained and analyzed the data and wrote the first draft of the manuscript. ESU, AM, JAS, CEG, AA provided general feedback for the manuscript. All authors approved the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors acknowledge the instruments and scientific and technical assistance of the MicroCore Microscopy Core at the Universidad de Los Andes, a facility that is supported by the vice presidency for research and creation. We acknowledge the help from Valentina Echeverry, Manuela Cort\u0026eacute;s and Alejandro Preciado (Jovenes Investigadores del programa UniAndes-PUJ), for the cuts, stereoscope method and preliminary analysis. Lydia Knuefing helped in the thomography processing and WebMango platform. This study was funded by the Ministerio de Ciencia y Tecnolog\u0026iacute;a \u0026ndash; Minciencias, Colombia, through the grant # 1204-852-70251 \u0026ldquo;Observatorio de la microbioerosi\u0026oacute;n, acidificaci\u0026oacute;n oce\u0026aacute;nica y disoluci\u0026oacute;n de arrecifes coralinos\u0026rdquo;.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eSome data are available in the main text or the supplementary materials. Raw data from Microtomography are all found in Figshare.com project 220825: DOI: 10.6084/m9.figshare.27041776 (https://figshare.com/account/projects/220825/articles/27041776)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTribollet, A. \u0026amp; Golubic, S. 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(2017).\u003c/span\u003e\u003c/li\u003e\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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Intracolonial analysis, coral skeleton microenvironments, coral-reef porosity, microboring, micro-CT, Porites spp","lastPublishedDoi":"10.21203/rs.3.rs-5054349/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5054349/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCoral skeletons provide habitat for a euendolithic community, forming a green band within the skeleton, where \u003cem\u003eOstreobium\u003c/em\u003e spp. is the dominant group. Euendoliths, actively penetrate live coral skeletons, but how they use and modify skeletal structure is not properly understood. This study explores the microstructural characteristics of skeletal microenvironments through a micro-CT technique that analyzes the \"footprint\" of the euendolithic community on the porosity of coral skeleton. We compared three \u003cem\u003ePorites\u003c/em\u003e species based on the percentage of the relative volume of microporosity, macroporosity, total porosity, and solid volume fraction of CaCO\u003csub\u003e3\u003c/sub\u003e among three distinct zones within the coral colony: coral tissue, the green band (characterized by eundolithic community) and the bare skeletal region. We found a significant increase in microporosity within the green band, while the opposite occurs for macroporosity that decreased within this zone, for all analyzed species. We describe a model to explain the porosity gradient along the vertical axis for \u003cem\u003ePorites\u003c/em\u003e coral colonies, and suggests that within the \u0026ldquo;green band\u0026rdquo; microenvironment, the metabolic activity of the community is the responsible for this pattern. Our findings provide insights on the ecological relationship with the coral holobiont: macroerosion mitigation and microporosity filling.\u003c/p\u003e","manuscriptTitle":"The footprint of endolithic algae in shaping the skeletal structure of massive coral skeletons: insights into micro and macro-porosity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-17 05:59:13","doi":"10.21203/rs.3.rs-5054349/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-19T12:32:15+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-18T16:00:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"215495795511748628915809159533891977382","date":"2025-03-13T09:41:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193342201362038279888030104515150485020","date":"2025-02-13T12:41:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-04T15:39:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"150482622662241036461137046376568801142","date":"2025-01-05T01:02:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"21059168831895786759524987424614824005","date":"2024-12-14T10:59:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"150805715455378632914957275485212393601","date":"2024-11-13T18:41:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"243276516060258957405639022686330194325","date":"2024-11-11T20:57:30+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-10-01T07:50:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-01T07:22:34+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-09-17T19:01:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-09-17T04:22:34+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-09-08T23:57:29+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4821c583-1d9a-489a-a916-1581422b2f2e","owner":[],"postedDate":"October 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":38404712,"name":"Biological sciences/Ecology"},{"id":38404713,"name":"Earth and environmental sciences/Environmental sciences"},{"id":38404714,"name":"Earth and environmental sciences/Ocean sciences"}],"tags":[],"updatedAt":"2025-07-28T16:05:12+00:00","versionOfRecord":{"articleIdentity":"rs-5054349","link":"https://doi.org/10.1038/s41598-025-99374-1","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-07-24 15:57:20","publishedOnDateReadable":"July 24th, 2025"},"versionCreatedAt":"2024-10-17 05:59:13","video":"","vorDoi":"10.1038/s41598-025-99374-1","vorDoiUrl":"https://doi.org/10.1038/s41598-025-99374-1","workflowStages":[]},"version":"v1","identity":"rs-5054349","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5054349","identity":"rs-5054349","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}