Growth Patterns of Reef-Building Porites Species in the Remote Clipperton Atoll Reef

Abstract

Remote reefs offer insights into natural coral dynamics, influenced by regional environmental factors and climate change fluctuations. Clipperton Atoll is the eastern tropical Pacific’s most isolated reef, where coral reef growth and life strategies have been poorly studied so far. Recognizing the coral species’ growth response might help understand ecological dynamics and the impacts of anthropogenic stressors on coastal reefs. The present study evaluates annual coral growth parameters of the most abundant coral reef-building species, Porites australiensis, Porites arnaudi, Porites lutea, and Porites lobata. The results showed that during 2015–2019, corals exhibited the lowest annual linear extension (0.65 ± 0.29 cm yr⁻¹), skeletal density (1.14 ± 0.32 g cm⁻³), and calcification rates (0.78 ± 0.44 g cm⁻² yr⁻¹) for the genera along the Pacific. Differences in growth patterns among species were observed, with Porites lutea and Porites lobata showing a higher radial extension, developing massive-hemispherical morphologies, and acting as structural stabilizers; meanwhile, P. arnaudi and P. australiensis exhibited more skeletal compaction but also with a high plasticity on their morphologies, contributing to benthic heterogeneity. These differences are particularly important as each species fulfills different ecological functions within the reef, contributing to the ecosystem balance and enhancing the relevance of the massive species in the physical structure of remote reef systems, such as Clipperton Atoll.

1. Introduction

The main attribute of scleractinian corals is their ability to precipitate calcium carbonate exoskeletons in complex shapes, which results in the construction of the physical structure of the reef [1]; however, tropical ecosystems are susceptible to climate change-driven ocean warming, which can constrain coral calcification and the maintenance of reef structure, which is often conflated by local anthropogenic pressures [2,3]. The evaluation of coral growth parameters from different locations can be crucial to distinguish natural environmental variability from human impacts and may even become a reef health and resilience marker [2]; this baseline becomes more relevant when obtained from pristine areas, and in addition to the assessment of reef health, helps identify the effects of natural and anthropogenic disturbances and can even support conservation strategies for coastal or more impacted coralline areas.

The coral species comprising the genus Porites Link, 1807 [4] represent the most abundant massive reef-building corals within coral-reef ecosystems in the Pacific Ocean [5], with a widespread distribution across most reef environments, even in non-optimal conditions, as they can dominate brackish and murky habitats [6,7]. Their physiological plasticity is also demonstrated by their thermal, salinity, and depth range, since they can inhabit intertidal zones, estuaries, or coastal lagoons up to 20 m depth [8]. As previously observed for other coral genera (e.g., Acroporids, Millieporids, and Pocilloporids), Porites corals’ physiological processes respond to fluctuations in sea surface temperature, light intensity, water quality, and local anthropogenic stressors, which overall control high energetic activities such as their growth rate [2,9,10]. The life strategy of the genus Porites has led the species to develop massive, branching, encrusting, plating, columnar forms and even growth as micro atolls and free-living corallites, resulting in high plasticity developed to occupy different environments [11,12,13].

Coral reefs from remote locations, as in the rest of the world, are affected by global environmental fluctuations, but not directly by local anthropogenic stressors [14]. In comparison, near-coast reefs must cope with climate change’s synergic effects, such as urbanization, sedimentation, organic or inorganic nutrient and pollutant spillover, and tourism or fishing activities [15]. Particularly, Clipperton Atoll located in the Eastern Tropical Pacific is an isolated, uninhabited, and relatively pristine system, situated over 1000 km off the coast of Mexico and approximately 5000 km from the central Pacific Islands [16]. The atoll is considered a key stepping stone area in the migration of marine species across the East Pacific Barrier, particularly during ENSO events as the current patterns change, acting as a bridge along the region, which has resulted in the high richness and coverage of hermatypic corals at the ETP, mostly represented by Pocillopora, Pavona, Porites, and Leptoseris [16,17,18]. The isolation also contributes to the presence of endemic species such as Porites arnaudi [17,18,19]. In addition to the structural and environmental conditions, the remote location of Clipperton Atoll provides an ideal scenario for forming a well-developed reef structure and the opportunity to characterize the life history of a hermatypic coral-formed reef in response to regional annual fluctuations and the effect of climate change.

Besides their ecological relevance as health indicators and as markers for understanding the geo-ecological dynamics of coral reef communities [20], massive reef-building Porites species archive historical climatic data within their calcium carbonate skeletons, enabling retrospective analyses of environmental conditions during their growth. Local environmental variability influences the formation of distinct high- and low-density skeletal bands, visible through X-radiographic imaging of their skeletal structures [2,9,10]. However, until now, there has been no information on historical coral calcification rates and species growth responses of coral reefs in remote and low-impacted environments. The present study analyzes the annual extension rate, skeletal density, and calcification rates over five years (2015–2019) of the main massive reef-building species: Porites australiensis, P. arnaudi, P. lutea, and P. lobata in the remote Clipperton Atoll reef. The data of this study provide insight into the natural dynamics of coral growth traits and determine the vulnerability of a pristine reef’s functionality under the current climate change scenario.

2. Materials and Methods

2.1. Study Area

Clipperton Atoll is the easternmost atoll (10°20′09.4″ N—109°10′51.1″ W, 10°15′53.8″ N—109°10′41.0″ W, and 10°15′49.2″ N—109°15′15.3″ W, 10°20′06.2″ N—109°15′19.2″ W) in the Pacific Ocean within the Northeastern Tropical Pacific [16]. The area is influenced seasonally by the North Equatorial Current (NEC) and the Equatorial Counter Current (ECC), promoting an annual mean sea surface temperature (SST) of 27.9 ± 0.23 °C and a seasonal SST range of 1.5 ± 0.28 °C with homogeneous thermal patterns along 60 m depth [16,21,22]. Clipperton Atoll is also periodically affected by North Pacific tropical cyclones from May to October [23], and the global effect of positive and negative thermal anomalies associated with the El Niño Southern Oscillation event [16]. The atoll presents a 3.5 km² well-developed fringing reef around the atoll, segmented by irregular spurs and grooves, characterized by reef platforms and frontal slopes at depths of 10 to 30 m, respectively [24] (Figure 1). The benthic reef area mainly comprises hermatypic corals of the genus Porites (n = 4 species), Pocillopora (n = 7 species), Pavona (n = 6 species), and low abundances of Leptoseris (n = 2 species) in deeper zones [16]. Particularly, the genus Porites is represented by four dominant species: Porites australiensis Vaughan 1918, Porites arnaudi Reyes-Bonilla and Carricart-Ganivet 2000, Porites lutea Mine Edwards and Haime 1851, and Porites lobata Dana 1846 [17,24].

2.2. Sample Collection

A total of 25 adult Porites colonies (≥1 m in diameter) were selected from a depth range of 10–20 m. All colonies showed no signs of disease or bleaching and were visually identified. A small fragment (100 cm²) was collected from each colony using a hammer and chisel, following the maximum growth axis section. Samples were classified by species based on morphological characteristics, following previous descriptions of each species [25,26,27,28]. Coral slabs between 7–10 mm were obtained from each coral fragment using a diamond-edged saw (Qep^®, Raton, FL, USA). All coral samples were cut following the vertical growth of the colonies to represent a section of the colony’s center. The resulting coral slabs were washed with fresh water to eliminate particles and dried for 4 h at 75 °C in a conventional oven. Each coral slab was classified by species and thickness to be radiographed with conventional radiography equipment (GE Hungay Rt. Medical Systems^®, Delhi, India) at 65 kV for 6.0 mAs at 1.80 m from the radiation source. An aragonite wedge of Tridacna maxima species was included as the carbonate density standard [29]. The radiographs were digitized at 75 dpi (Kodak Direct View Classic Cr System, Nagpur, Maharashtra, India). The resulting images were corrected following the technique described by Duprey et al. [30], to avoid bias in the overestimation of density values related to changes in radiation intensity that produce heterogeneous irradiation, also known as the heel effect or the inverse square law (Figure 2). The growth parameters (skeletal density, extension rate, and calcification rate) were obtained using the ImageJ 1.46 Software (http://rsb.info.nih.gov/ij/ (accessed on 13 March 2024)). All images were processed following the optical densitometry method described by Carricart-Ganivet and Barnes [29]. For each coral sample, the high- and low-density growth bands were identified from the outside to the inside of the slab, following the major growth line of one of the corallites observed in the slab (growth track). This procedure was repeated in triplicate per slab to reduce intracolonial variability in growth parameters [31]. The skeletal density (g cm⁻³) was estimated by averaging the values between each pair of low-density bands along the growth track. Extension rate (cm yr⁻¹) was measured as the linear distance between two low-density bands, and the product of the extension rate and skeletal density calculated the calcification rate (g cm⁻² yr⁻¹). The growth parameter results are presented as mean values ± standard deviation ($\overline{\mathrm{x}}$ ± SD).

Since temperature is an environmental variable that has previously been reported to influence the growth of Porites species [9,32,33], monthly sea surface temperature (SST) data were obtained from 4 × 4 km resolution Aquamodis^® satellite imagery (https://oceancolor.gsfc.nasa.gov (accessed on 5 August 2024)) level 3 and analyzed using Statitist^® ver. 6.33 Wimsoft. These data were averaged to calculate the annual mean SST (± SD) and subsequently determine its relationship with the growth parameters (skeletal density, extension rate, and calcification rate) of the Porites species (Porites lutea, P. lobata, P. arnaudi, and P. australiensis).

2.3. Data Analysis

The database was constructed using annual growth parameter values (skeletal density, extension rate, and calcification rate) calculated from three replicate tracks analyzed for each coral colony. A draftsman plot routine was generated to assess multicollinearity among the growth parameters, considering an absolute correlation coefficient (r) threshold of 0.70. As no significant collinearity was detected among the growth parameters, all of them were included in the multivariate analysis.

Variations in growth parameters among species over the studied period (2019–2015) were assessed using a permutational multivariate analysis of variance (PERMANOVA), which was based on a two-way crossover experimental design with fixed factors (type I model) and a covariable. This design was expressed as a multifactorial linear model:

$$Y={Co}_i+S_j+Y_k+{S·Y}_{ij}+{\epsilon }_{ijk}$$

where Y is the multivariate matrix of response variables (i.e., skeletal density, extension rate, and calcification rate), ${Co}_i$ is the covariable representing the temperature effect on the growth parameters, $S_j$ is the species factor (n = 4), $Y_k$ is the year factor n = 5), ${S·Y}_{ij}$ is the term of the interaction between species and year factors, and ${\epsilon }_{ijk}$ is the cumulative error. The PERMANOVA model and pairwise comparisons were based on a Euclidean distance matrix constructed from the normalized data (Z values) and tested with 10,000 permutations of residuals, under a reduced model with a type I sum of squares. PERMDISP was used to verify the homogeneity of dispersions between species and years. To visualize changes in the growth parameters of the species (P. australiensis, P. arnaudi, P. lutea, and P. lobata) during the period studied (2015–2019), a principal coordinate analysis (PCO) was performed using a Euclidean distance matrix on average and normalized data of the growth parameters per year. To visualize the individual relationship between growth parameters and SST as well as the growth strategy of each species, simple linear regressions were performed between each growth parameter and the mean annual SST (skeletal density vs. mean annual SST, extension rate vs. mean annual SST, and calcification rate vs. annual SST), as well as between the growth parameters (calcification rate vs. skeletal density, calcification rate vs. extension rate, and skeletal density vs. extension rate). Simple linear regression analysis was performed separately for each species. All statistical analyses were performed using PRIMER v.6 and PERMANOVA+, and graphics were designed using SigmaPlot software V. 11.0.

3. Results

A total of 45 growth tracks corresponding to the four species (Porites lutea, Porites lobata, Porites arnaudi, and Porites australiensis) were analyzed (

Table 1. Mean growth parameters ($\overline{\mathrm{x}}$ ± SD) of the skeletal density, extension rate, and calcification rate for Porites lutea, Porites lobata, Porites arnaudi, and Porites australiensis over a year period.

Specie	No. Colonies	No. Tracks	Growth Parameters
			Density (g cm−3)	Extension (cm yr−1)	Calcification (g cm−2 yr−1)
P. lutea	6	10	0.96 ± 0.19	0.65 ± 0.33	0.62 ± 0.33
P. lobata	5	9	0.91 ± 0.27	0.73 ± 0.33	0.71 ± 0.45
P. arnaudi	8	16	1.30 ± 0.31	0.69 ± 0.28	0.95 ± 0.50
P. australiensis	6	10	1.22 ± 0.27	0.55 ± 0.23	0.70 ± 0.37
Total number	25	45

). At the genus level, Porites showed a skeletal density of 1.14 ± 0.32 g cm⁻³, a skeletal extension of 0.65 ± 0.29 cm yr⁻¹, and a calcification rate of 0.78 ± 0.44 g cm⁻² yr⁻¹. The species P. arnaudi presented the highest skeletal density of 1.30 ± 0.31 g cm⁻³, and P. lobata presented the lowest (0.91 ± 0.27 g cm⁻³). In terms of the extension growth rate, P. lobata showed the highest values (0.73 ± 0.33 cm yr⁻¹), and P. australiensis the lowest (0.55 ± 0.23 cm yr⁻¹). For annual calcification, P. arnaudi showed the highest calcification rate along the studied period, resulting in 0.95 ± 0.50 g cm⁻² yr⁻¹, and P. lutea the lowest of 0.62 ± 0.33 g cm⁻² yr⁻¹ (Table 1 and Figure 3). The statistical analysis showed no significant differences in temperature, growth parameters among years, the interaction of the species x years, and the absence of a relationship between growth parameters and temperature (p > 0.001;

Table 2. PERMANOVA, pair-wise comparisons, and PERMDISP outputs of the comparison of temperature, growth parameters per species, year, and interaction. Codes are: CV% is the variation component represented as percentage, P. lutea = Porites lutea, P. lob = Porites lobata, P. arn = Porites arnaudi, and P. aus = Porites australiensis. Significant differences (p ≤ 0.05) are marked in bold. Note: The term related to temperature represents the covariate (Co) of the model.

PERMANOVA				PERMDISP	Pairwise Comparison
Source	Pseudo-F	p	CV%	p	Groups	p (perm)
Temperature	0.8	0.3962	2.07		P. lut, P.aus	0.0001
Species	10.6	0.0001	33.2	0.184	P. lut, P. lob	0.3186
Year	1.4	0.2029	8.02	0.1091	P. lut, P. arn	0.0001
Species x Year	0.4	0.9876	18.4	0.3	P. lob, P. arn	0.0001
					P. lob, P. aus	0.0004
					P. arn, P. aus	0.0091

and Figure S1). However, differences were determined at the species level (p < 0.001), where only Porites lutea and Porites lobata presented similar density, extension, and calcification rate (p = 0.3186) over the years; these results coincide with the PCO (Figure 4), where it is observed that these species invest calcification energy in skeletal extension, which is supported by the skeletal density observed in the low-density records, especially in P. lobata and P. lutea, which presented the lowest density values, 0.80 ± 0.32 g cm⁻³ in 2015 and 0.91 ± 0.11 g cm⁻³ in 2016, respectively (

Table 3. Growth parameters ($\overline{\mathrm{x}}$ ± SD). Skeletal density, extension rate, and calcification rate for Porites lutea, Porites lobata, Porites arnaudi, and Porites australiensis, per year (2019–2015).

Specie	Year (Yr)	Density (g cm−3)	Extension (cm yr−1)	Calcification (g cm−2 yr−1)
P. lutea	2019	0.96 ± 0.25	0.44 ± 0.10	0.42 ± 0.14
	2018	0.99 ± 0.24	0.68 ± 0.30	0.68 ± 0.33
	2017	0.92 ± 0.17	0.58 ± 0.20	0.54 ± 0.19
	2016	0.91 ± 0.11	0.77 ± 0.51	0.70 ± 0.46
	2015	0.96 ± 0.17	0.75 ± 0.37	0.72 ± 0.39
P. lobata	2019	1.00 ± 0.19	0.54 ± 0.14	0.55 ± 0.20
	2018	0.97 ± 0.26	0.77 ± 0.46	0.80 ± 0.58
	2017	0.94 ± 0.26	0.82 ± 0.44	0.81 ± 0.55
	2016	0.84 ± 0.32	0.80 ± 0.29	0.74 ± 0.49
	2015	0.80 ± 0.32	0.70 ± 0.25	0.62 ± 0.43
P. arnaudi	2019	1.36 ± 0.33	0.62 ± 0.18	0.89 ± 0.42
	2018	1.33 ± 0.26	0.71 ± 0.33	1.01 ± 0.63
	2017	1.28 ± 0.33	0.69 ± 0.27	0.95 ± 0.49
	2016	1.28 ± 0.32	0.65 ± 0.31	0.90 ± 0.51
	2015	1.22 ± 0.35	0.77 ± 0.27	0.98 ± 0.49
P. autraliensis	2019	1.28 ± 0.25	0.55 ± 0.20	0.72 ± 0.33
	2018	1.23 ± 0.31	0.52 ± 0.17	0.67 ± 0.32
	2017	1.23 ± 0.31	0.55 ± 0.24	0.71 ± 0.40
	2016	1.22 ± 0.29	0.57 ± 0.30	0.75 ± 0.47
	2015	1.17 ± 0.24	0.61 ± 0.29	0.74 ± 0.40

and Figures S2 and S3).

A PCO was built to understand dissimilarities in the growth pattern among the Porites species overall with a perspective of understanding the response as a community. The PCO1 explained 55.22% of the total variation, grouping species across years, observing low variation over the five years, noting the highest values of calcification rate in 2016, extension rate in 2019, and skeletal density in 2015 at genus level; also, it denotes low values of density rate among all species with emphasis on P. lobata and P. lutea. PCO2 explained an additional 44.5% of the total variation, grouping species by growth parameter. The species P. lutea and P. lobata showed similar distribution patterns over the years, with an affinity for skeletal extension, while P. arnaudi and P. australiensis presented a similar pattern, showing minimal variation in growth parameters over the years, driven by calcification and density, respectively (Figure 4).

4. Discussion

Remote coral reefs have long been considered potential refuge areas due to their geographic isolation, limiting land-based human stressors; nevertheless, they also remain vulnerable to regional and global environmental threats [14,34]. Clipperton’s coral reefs possess a high abundance of massive coral species [16], which actively contribute to long-term calcium carbonate accumulation and maintain the structural and functional integrity of coral-reef ecosystems [35]. This can be achieved by Porites’ particular capability to trade strategies and develop reef structures with consistent growth rates. The recorded growth pattern differences among species indicate that even under low-fluctuating environmental conditions that influence the area, each coral species has developed different life traits and, therefore, a specific susceptibility to environmental conditions, which can result in each organism fulfilling a specific ecological function.

Although environmental conditions can be considered optimal for reef development, due to the oligotrophic waters [17,36] and the low variability observed in SST, the analysis at genus level revealed that all three growth parameters (skeletal extension, skeletal density, and calcification rate) were lower than those reported for the Indo-Pacific, Central Pacific, and Eastern Tropical Pacific (

Table 4. Mean (± SD) annual skeletal density, extension rate, and calcification rate obtained by other authors at different sites for Porites, Porites lobata, and Porites lutea. (-) No available data.

Specie	Location	Density (g cm−3)	Extension (cm yr−1)	Calcification (g cm−2 yr−1)	Reference
Porites	Great Barrier Reef, Australia	1.28 ± 0.16	1.3 ± 0.34	1.63 ± 0.38	[6]
Porites	Moorea (French Polynesia)	1.15	1.86	1.25	[37]
P. lobata	Galapagos Islands	-	0.81	-	[38]
P. lobata	Great Barrier Reef, Australia	1.1	-	-	[39]
P. lobata	Australia	1.41 ± 0.13	1.23 ± 0.24	1.71 ± 0.25	[40]
P. lobata	Isla Isabel, Mexico	1.08 ± 0.14	0.47 ± 0.23	0.51 ± 0.26	[41]
P. lobata	Zacatoso, Mexico	1.20 ± 0.07	0.60 ± 0.16	0.72 ± 0.22	[42]
P. lobata	Isla Isabel, Mexico	1.17 ± 0.02	0.57 ± 0.03	0.65 ± 0.03	[43]
P. lutea	Enewetak Atoll	-	1.35	-	[44]
P. lutea	Enewetak Atoll	1–1.40	0.4–0.5 1.35	-	[45]
P. lutea	Enewetak Atoll	-	0.76	-	[46]
P. lutea	South Thailand	-	2.25	-	[47]
P. lutea	Abaiang Atoll, Republic of Kiribat	-	2.12 ± 0.10	-	[48]
P. lutea	Tunda Island, Indonesia	-	0.5–2.2	-	[49]
P. lutea	Pulau Tinggi, Malaysia	1.23 ± 0.04	1.88 ± 0.15	2.01 ± 0.08	[50]

), where skeletal extension is 42% lower; meanwhile, skeletal density and calcification rate also had slightly inferior results by 21% and 22%, respectively. However, this comparison must be interpreted cautiously, as annual variability in growth data could mask differences between reefs from other regions.

It is well-documented that coral growth responds to environmental conditions and extrinsic factors [9,51]. In particular, sea surface temperature (SST) has been considered the most important driver for coral maintenance, mainly influencing linear extension and calcification, as an increase of 3 mm year⁻¹ has been recorded along with a 0.3 g cm⁻² year⁻¹ per +1 °C increase in SST for massive coral species [10,52,53]. Nevertheless, it is important to consider the synergistic effect of other factors, such as hydraulic energy and distance from the coast, with lower skeletal density usually observed in sites inshore compared to offshore reefs [47]. The Clipperton Atoll, and previous records, have shown annual SST of 28.38 ± 0.77 °C, with thermal fluctuations up to ≥1.1 °C only during ENSO events [16,17]. This low SST fluctuation causes no interannual variability in coral growth, contrary to the general pattern for this genus [9,10,54]. The thermal stability of the site is much more relevant as the records coincide with a severe El Niño 2014–2017 event, which caused devastating mortality in reefs worldwide [55]; still, no heatwaves were recorded in the atoll. Therefore, the records obtained provide a valuable and recent life history overview of the role of Porites on Clipperton Reef, and the ability of the coral to respond in conditions where there is no direct anthropogenic intervention [2,56,57]. At reef level, the observed strategy of Porites suggests that the reef is composed of colonies with slow vertical growth but with denser skeletons, conferring resistance to biological, chemical, and even physical bioerosion [58], which is particularly relevant for emerging reefs, such as Clipperton, that need the continuous maintenance of their framework [59,60].

Despite the low growth parameters, the studied Porites species exhibited higher skeletal density, contrary to that commonly reported for the genus from other localities, as it usually shows higher skeletal extension (Table 4). Coral skeleton growth formation and its variations have two main components: the energy available for the active deposition of calcareous material [60] and the pathways where the organism invests this material in extending its skeleton [61]. Porites’ growth strategy usually invests the energy toward skeletal extension [42,62]; however, this overlooks the exposure to long-period swell, high waves, and even storms and hurricanes, which, in atolls, generate beach ridges, reef-front grooves, and spurs [63]. In the last decade, the influence of hurricanes and storms has increased in intensity and frequency, and records showed that, particularly during the period 2015 to 2017, at least two hurricanes of category 4 or higher (Saffir–Simpson Scale) affected the atoll [64]. Clipperton Atoll is located over 1000 km from the continent [18], and therefore, rather than SST, the synergic effect of distance from the coast and meteorological events may become the most significant drivers that modify the growth patterns in Porites, resulting in a strategy focused on skeletal density. As a secondary effect, the shift of growth strategy may be a consequence of the decrease in the calcification and extension rate, which would make it seem that the density is increasing; however, when observing the previous reports for the genus (Table 4), is evident that the skeletal density is not increasing, but rather, like the skeletal extension and the calcification rates, it is decreasing, but to a lesser extent.

At the species level, our results revealed significant variability of the growth parameters between all four species, P. lutea and P. lobata vs. P. arnaudi and P. australiensis (Figure 4). Particularly, P. lutea and P. lobata show variability in their growth parameters over the years, evidencing an affinity for high skeletal extension compared with P. australiensis and P. arnaudi. Differences between species were expected since the genus Porites shows polymorphism due to phenotypic plasticity [65,66]. The similarity in the growth patterns of P. lutea and P. lobata may reflect their closeness in morphology and genetic proximity, developing a hereditary affinity [16,67], and a different pattern was observed in P. arnaudi and P. australiensis, where both species’ growth rates presented low variation over the years compared to the sister species P. lobata and P. lutea, evidencing affinity toward calcification and density. The differences within the Porites genus within the same reef have been previously reported, but still, they have a common pattern of low growth rates compared to other regions [2,68,69,70] (Table 4). The variability of morphologies between species and individuals of the same species is an adaptive strategy in response to local conditions [13,71]; however, this will have implications for their contribution to the three-dimensional structure and ecological functionality traits, such as the availability of shelter protection and substrate stability.

This study highlights the high morphological plasticity of species of the genus Porites, which not only allows each species to contribute particularly to ecological functions, such as heterogeneity and cementation, but also underpins long-term reef accretion and resilience. Meanwhile, P. australiensis and P. arnaudi act as primary stabilizers, contributing cementation and physical consolidation to the reef framework; P. lutea and P. lobata contribute to the three-dimensional complexity. Although they are coral reef-building species of the same genus, their presence and abundance will contribute to the framework’s formation and fulfill different ecological functions, which are key to the ecosystem’s permanence. Due to the unique characteristics of Clipperton Atoll, continuous monitoring of its coral assemblages is essential to understand and predict how pristine reef communities respond to climate change.