Instability is not the only driver of rubble impacts on coral settlement and recruitment

Instability is not the only driver of rubble impacts on coral settlement and recruitment | 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 Research Article Instability is not the only driver of rubble impacts on coral settlement and recruitment Roima Paewai-Huggins, Tania M. Kenyon, Peter J. Mumby This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7993495/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Beds of dead coral rubble are widely reported to impede coral recovery, and causation has been linked to rubble instability. However, additional environmental factors, including flow and sedimentation, may also impact coral recruitment in this habitat. Indeed, the drivers of coral recruitment likely differ with the type of rubble. Here, we experimentally remove the influence of rubble mobility and evaluate how different rubble environments influence the process of coral settlement and recruitment (a loose vs. interlocked rubble habitat). Stabilised rubble recruitment tiles were deployed both flush with the substrate and elevated 20 cm above the substrate to separate substrate/environmental effects from differential larval supply among treatments. Coral settlement was greatest on stabilised tiles deployed in the more structurally complex habitat (reef carbonate without rubble). Settlement declined by 2 to 4-fold in rubble habitats with high interlocking structure and declined even further (8-fold) in structurally simple, loose rubble. These trends reflect environmental drivers rather than any differences in rubble stability. Post-settlement mortality was high across stabilised tiles regardless of habitat. While recruitment tracked the improvement in settlement from loose to interlocked rubble, recruitment from interlocked rubble to reef habitat became comparable, 12 months post-deployment. Even if stabilised, loose rubble beds are likely to have low recovery prospects, whereas interlocked rubble beds can provide suitable coral substrates under the right environmental conditions. Rubble stabilisation alone will not increase coral recovery within certain types of rubble beds, and this should be considered when determining how or if restoration intervention is required. rubble coral settlement post-settlement survival substrates Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Reefs are in constant flux between bioconstruction and erosion through the biological growth of corals, coral mortality, and physical and biological erosion of the framework, whereby corals transition from dead coral to rubble and sand (Wolfe et al., 2021 ). The balance of reef building and erosion is driven by the frequency and severity of disturbances and the tolerance of the coral assemblage experiencing the disturbance (Dollar & Tribble, 1993 ; Fox & Caldwell, 2006 ; Rasser & Riegl, 2002 ). Overfishing, mass bleaching events, disease, and ocean acidification are impacting coral reefs on a global scale (Roth et al., 2018 ; Salinas-de-León et al., 2013 ; Sánchez-Quinto & Falcón, 2019 ; Viehman et al., 2018 ; A. Wakwella et al., 2020 ). Specific impacts can diminish the structural complexity of reefs by breaking up and eroding the coral framework into rubble. Wave energy from storm disturbances such as cyclones, hurricanes, and tsunamis has resulted in vast rubble beds (Blanchon et al., 1997 ; Viehman et al., 2018 ). Similarly, coral bleaching, ship groundings, and coral disease can reduce reefs to rubble (Ceccarelli et al., 2020 ). Though rubble production is part of the natural cycle of reef accretion and erosion, the rate of conversion of living coral reefs into rubble beds is increasing as impacts amplify in severity and frequency on a global scale (Ceccarelli et al., 2020 ; Sánchez-Quinto & Falcón, 2019 ). Repeated or chronic disturbances, both natural and anthropogenic, can have long-lasting effects and hinder the recovery of coral cover (Fox et al., 2003 ; Rasser & Riegl, 2002 ; Viehman et al., 2018 ). Coral rubble, as a settlement substrate, is considered suitable for both coral settlement and many other sessile marine invertebrates due to microscale rugosity and the presence of necessary biofilms (Harrington et al., 2004 ; Heyward & Negri, 1999 ; Lee et al., 2009 ; Mundy, 2000 ). However, depending on the type, intensity, and time since disturbance, generated rubble can vary in size, morphology, and bed depth, affecting the stability of rubble pieces and the physical characteristics of the rubble bed (Wolfe et al., 2021 ). Rubble has been termed as ‘killing fields’ for corals due to the unconsolidated nature of the rubble substrate and its mobilisation with waves and currents (Ceccarelli et al., 2020 ; Fox 2002) Low levels of post-settlement survival for coral settlers in rubble beds have been attributed primarily to the instability of rubble pieces (Fox, 2004 ; Fox & Caldwell, 2006 ; Raymundo et al., 2007 ). Yet, many other environmental and ecological factors might vary among rubble bed typologies and could contribute to decreased coral recruitment in rubble beds. Examples include increased sedimentation rates, increased competition from other sessile benthic organisms, or decreased settlement-inducing chemical cues from groups such as crustose coralline algae (Doropoulos et al., 2016 ; A. Wakwella et al., 2020 ). Because rubble beds have a dramatically different structure than healthy reefs, many of the key studies on rubble function have focused on the contrast between ‘rubble beds’ and coral-dominated reefs (Chong-Seng et al., 2014 ; Fox, 2004 ). With renewed interest in the role of rubble and a potential increase in rubble generation, it is important to disaggregate the types of rubble habitats and explore their dynamics explicitly. This study includes two types of rubble beds. The first is composed of smaller, non-branched rubble pieces (herein referred to as the loose rubble bed). The size and morphology of these rubble pieces create a more densely packed and flat rubble substrate, and are likely more prone to rubble mobility (Kenyon et al., 2020 ; Kenyon et al., 2024 ) (Fig. 1 b). The second is composed of large, branched rubble pieces (herein referred to as the interlocked rubble bed). The size and morphology create an interlocking configuration of rubble, resulting in a relatively stable and structurally complex substrate (Kenyon et al., 2024 ) (Fig. 1 c). Here, we wish to understand how the environment associated with different rubble beds influences coral settlement and recruitment (i.e., to remove the influence of rubble mobility). In doing so, our study examines associations between benthic habitats and their immediate environment (flow, sedimentation, etc.) and how these affect coral recruitment. Moreover, our results may provide insight into the potential benefits of ‘rubble stabilisation methods’, because while they may solve the mobility problem, they are less likely to alter other environmental drivers that might still constrain coral recovery. We examine the importance of rubble stability in a separate study (Paewai-Huggins et al., 2025b ). Methods 3.1. Study sites This study was carried out at two reefs -Heron and Wistari (Fig. 1 a) – in the vicinity of Heron Island, in the sea country of the Gooreng Gooreng, Gurang, Bailai and Taribelang Bunda peoples of the Southern Great Barrier Reef. A significant limitation of studying rubble beds in the Heron reef complex is that patches of rubble are infrequent and widely separated. This makes it difficult to identify replicate rubble treatments in the same overall physical wave environment, and allowing treatments to occur in different environments is likely to impact their stability and biology (Wolfe et al., 2023). Therefore, it was necessary to identify two locations (Heron and Wistari Reefs) where at least two rubble substrates could be compared within a similar physical environment. Yet even holding wave exposure similar – by choosing sites within ca 200 m – there is a significant likelihood that local hydrodynamic processes would alter larval supply to the vicinity of substrates being compared (e.g., loose rubble vs interlocked rubble at Heron Reef). Thus, we have two tile height treatments, benthic tiles, deployed to be flush with the substrate in each habitat and elevated tiles, raised 20 cm above the substrate. Benthic tiles allow us to investigate impacts influencing settlement and recruitment rates, directly related to differences between the benthic substrates of each habitat. While the elevated tiles allowed us to quantify varying patterns in larval supply between habitats, not associated with the composition of the substrate, and if necessary, adjust our interpretation of the settlement on benthic tiles. Though the exact type of disturbance that created either the loose or interlocked rubble beds of Heron Reef is unknown, it is presumed that much of the rubble production within this region is a result of cyclone activity passing through the channel between Heron Reef and Wistari Reef (Connell et al., 1997 ). The difference in the typology of either rubble bed is hard to determine accurately. Still, it could be an accumulation of a variety of factors, such as the type of predominant coral cover within each area prior to any disturbance or perhaps the geomorphological structure of the reef pre-disturbance, causing the smaller non-branched rubble of the loose bed to accumulate in between areas comprised of the larger, branched rubble of the interlocked bed. The first site, Heron Reef, was located at 8–9 m depth and included rubble substrates of two types, located 200 m apart: 1) an unstable rubble bed (Fig. 1 b) due to the composition of loose and largely unbound rubble pieces (‘loose’ rubble bed) and 2) a relatively more stable rubble bed (Fig. 1 c) with larger, interlocked and commonly bound pieces (‘interlocked’ rubble bed). The rubble in the loose rubble bed is relatively small in length and diameter, i.e., 7.6cm ± 0.74 (mean ± SE) and 1cm ± 0.11 (mean ± SE), respectively. Most pieces in this bed do not have branches, are more densely packed, have small gaps/void spaces between the individual pieces, and are easily picked up from the substrate without interference from interlocking or burial, indicating they are vulnerable to mobilisation (Kenyon et al., 2020 ; Kenyon et al., 2024 ) (Fig. 1 b). The interlocked rubble bed includes large, branching rubble pieces averaging 15.9cm ± 1.2 (mean ± SE) in length and 1.7cm ± 0.22 (mean ± SE) in diameter. Individual pieces are more challenging to pick up, often needing to be twisted carefully or broken to separate them from other pieces with which they are interlocked. Due to the size and branching morphology of the rubble pieces, there are larger void spaces between individual pieces, creating a more structurally complex rubble bed (Fig. 1 c). The site on Wistari Reef, also at an 8–9 m depth, comprised two different substrates: 1) an interlocked rubble bed (See Appendix Fig. 1) like that found at the Heron site and 2) a stable hard carbonate reef, located within 100 m of one another (See Appendix Fig. 1). The interlocked rubble bed at Wistari Reef has similar physical attributes to the interlocked rubble bed at Halfway, with large, branched rubble pieces. The hard carbonate reef habitat is a stable substrate that is part of the coral reef framework. 3.1.2. Recruitment tile construction and deployment Rubble recruitment tiles were produced to mimic the rubble substrate faithfully. These comprised 180mm x 180mm stainless steel mesh onto which rubble pieces collected from the field were cable-tied in pairs. Before attachment, rubble pieces were cleaned with fresh water, bleached overnight to remove living material, rinsed again, and dried in sunlight. Rubble pieces were placed to cover the tiles comprehensively, and, because their size varied, the number of rubble pieces used per tile ranged from 10–24. Each tile was given a unique ID tag. To allow the rubble tiles to be conditioned and develop a biofilm, they were deployed over 3 days from October 13–15, 2021, ~ 4.5 weeks before the spawning event at Heron and Wistari reefs. Within each substrate, 40 tiles were deployed, totalling 160. At each substrate, 20 tiles were placed flush with the substrate (herein referred to as benthic tiles) (Fig. 1 d), and 20 of the tiles were raised 20cm above the substrate (herein referred to as elevated tiles) (Fig. 1 e). Tiles were deployed and attached to the substrate using basalt reinforcing bar stakes (1m), in an area that measured 5m x 5m. Elevated tiles acted as controls to detect potential differences in larval supply between the rubble bed (e.g., loose vs interlocked rubble vs. interlocked rubble) that would influence coral settlement. For example, if larval supply, measured on the elevated tiles, was comparable between loose and interlocked rubble beds, then any difference in settlement observed on benthic tiles placed directly on the rubble benthos could be attributed to differences in the local rubble environment (rather than external differences in access to larvae because of, say, flow). 3.1.3. Rubble tile collection and inspection The first collection of rubble tiles occurred in January 2022, ~ 4 months after deployment, to determine coral settlement (within three months of the 2021 spawning event). The collection of tiles took a total of nine days from January 12th to the 20th. Rubble tiles were collected and returned to the lab, and held in tanks with flow-through ambient seawater. Coral settlers were observed using an Olympus SZ dissection microscope while held in shallow seawater. Each piece of rubble was removed from the metal mesh grid, both sides were photographed, and the piece was measured (the diameter of the centre and length, from which we used to calculate the surface area of each rubble piece). Each rubble piece was assigned a reference point, i.e., one end of the rubble piece, so that the distance from the reference point to each coral settler could be recorded. The settler’s location on either the topside, sides, or underside of the rubble piece was noted, as well as the condition of the coral settler, as alive, dead, or partially dead. The presence of any other sessile organisms growing near, touching, or covering the coral settler was also noted. Before inspection, each tile was photographed, and the top and underside were mapped with a unique letter and number code for each rubble piece so that rubble pieces could be reattached precisely in the exact location and orientation. Pieces of rubble were kept in seawater during the entirety of the inspection. The rubble tiles were redeployed to their original stakes, where they remained until recollection, which occurred in September and October 2022, to investigate post-settlement survival and recruitment within 12 months of the 2021 spawning event. The investigation of coral recruitment followed the same procedures as above. Using the maps of the rubble tiles and the documented location of each coral settler in January/February 2022, the presence or absence of the settler in September/October was documented. Photos of rubble pieces were also used to identify the percentage cover of sessile invertebrates and algal species that encrusted rubble pieces and to determine any potential competitors for space that may impact corals' settlement or recruitment rates. This study separated the rubble-encrusting organisms into three categories: ‘bare space’ (space on the rubble that was covered only by endolithic algal biofilm, but otherwise bare from any other benthic sessile colonisers), ‘CCA’ (crustose coralline algae), and lastly ‘competitors’. This category included a range of benthic sessile organisms, including turf algae, macroalgae, sponges, ascidians, bryozoans, tunicates, as well as various bivalve species and worm cases, which were determined to be too difficult to distinguish. In comparison to competitors, which likely inhibit coral settlement and possible survival, we reasoned that bare space and CCA acted instead as coral settlement facilitators. 3.1.4. Sedimentation To characterise sedimentation rates within the different substrates, ‘turfpods’ were deployed in each substrate. These turfpods are modified sediment pods, (Field et al., 2013 ; Storlazzi et al., 2011 ). Turfpods were designed using a 9 cm diameter PVC pipe cut to lengths of 7cm, filled with concrete, and topped with a circle of 3mm long plastic turf grass (modified after (Babcock & Smith, 2002 ; Latrille et al., 2019 ; Stewart et al., 2006 ). Four turfpod deployments took place: the first was in September 2022, the second in February 2023, the third in August 2023, and the fourth in September 2023 to increase our sample size and temporal representation. In the 2022 deployment, three turfpods were deployed per substrate at both the Heron Reef and the Wistari Reef substrates. In the 2023 trials, five turfpods were deployed, but only within the two rubble beds at the Heron Reef site (i.e., the loose rubble bed and interlocked rubble bed). Since no new studies of settlement and recruitment (Paewai-Huggins et al., 2025) occurred at Wistari Reef in 2023, no sedimentation measurements were taken at this time. Deployment duration, collection, and lab processing methodologies were the same in each trial. After six days of deployment, the turfpods were carefully collected and placed into plastic bags, taking caution not to disturb any sediment on the pod tops. In the lab, each plastic bag was emptied into a large container, and turfpods were rinsed thoroughly with fresh water to move sediment into the container. The sediment sample was rinsed with fresh water to remove salt before being emptied into a 50 ml Falcon tube. Sediment samples were left to settle, and excess water was poured off; this was repeated twice. Each tube was dried at 60° C for 24 hours and weighed. Data were standardised to grams of sediment accumulated per m 2 per day (Field, 2013). 3.1.5. Flow Using plaster-of-Paris (UniPro), we made 4cm 3 flow cubes to test water flow differences between the two rubble bed substrates located on Heron Reef, using the dissolution rates of cubes as a proxy for flow (Fox, 2004 ). A higher dissolution rate indicated greater exposure to water flow. Three deployments of cubes took place in February, August, and September 2023. Two treatments were used to determine how the differences in rubble composition between the two rubble beds influenced the flow of water. The 'surface' treatments functioned as a proxy to determine how flow travelling across the two rubble beds varies due to differences in the compositing of either rubble bed substrate. The ‘buried’ treatment was used to determine if flow can penetrate deeper into the rubble bed, depending on the void spaces between individual rubble pieces. In February, a total of 8 cubes were deployed in the rubble beds; four of the flow cubes were placed directly on the surface of the in situ surrounding rubble (‘surface’ treatment), and the last four were placed buried within the in-situ rubble (‘buried’ treatment). In August and September, replication was increased. In each rubble bed, 12 cubes were deployed. Six cubes were deployed directly on the in-situ rubble (‘surface’ treatment), and six were deployed in the in-situ rubble (‘buried’ treatment). 3.2. Statistical Analysis In summary, we first compared the absolute levels of coral settlement and recruitment among treatments, both of which involve count data. We then compared the rates of post-settlement mortality, which accounts for the difference between settlement and recruitment. These latter analyses use binomial data (survived or not). To attempt to understand why any differences among treatments occurred, we also compare the community structure of fouling organisms on the rubble over time and attempt to relate this to settlement and recruitment. Similarly, we evaluate patterns of sedimentation among treatments. For each model, backward stepwise model fitting was conducted; non-significant model terms were removed, and the best model was selected using the Akarike Information Criterion (AICc) with package “MuMIn” (Barton, 2009 ). Statistical analyses were performed using R Team (RStudio, 2020) for all analyses. 3.2.1. Coral settlement (Three months post-deployment) To analyse the effects of substrate and tile height on coral settlement rates generalized linear mixed-effects models were run using the package ‘glmmTMB’ (CRAN) for each reef. The response variable was settlement (i.e., the count of coral settlers per rubble piece); the predictor variables were the substrate type (loose rubble vs. interlocked rubble for Heron Reef and interlocked rubble vs. hard carbonate for Wistari Reef), tile height (benthic vs. elevated), and their interaction, and a random effect of tile ID was included to account for multiple rubble pieces per tile. We also analysed settlement in response to the microhabitat of the rubble piece (topside, side, and bottom side) for each rubble piece to determine any settling preference of coral larvae in relation to exposed or sheltered surfaces of the rubble. However, those data are not presented in the main results, as here we were less interested in the location of settlement onto rubble, but rather more interested in the general rate of settlement onto rubble. However, those results are located in the Appendix. A negative binomial distribution was used for the count response, employing a log link function. The surface area of rubble of each piece was also included as an offset to standardise the recruit count to rubble size. 3.2.2. Coral recruitment (12 months post-deployment) To analyse the abundance of corals that survived from three months to 12 months, generalised linear mixed-effects models were run using the package ‘glmmTMB’ for each reef. The response variable was coral recruitment (i.e., the count of settled corals per rubble piece that were still alive 12 months post-deployment). The predictor variables were the substrate type, tile height, and their interaction, and a random effect of tile ID was again included. 3.2.3. Post-settlement mortality rate (12 months post-deployment) To determine how the probability of mortality occurring from three months to 12 months differed between substrates and tile heights at each reef, two generalised linear mixed-effects models were run using the package ‘glmmTMB’. For both, a binomial error structure was used with a logit link function, as the response variable was binary (i.e., 1 for a coral that had settled at three months and was no longer present at 12 months and 0 for a coral settled at three months and was still present at 12 months); the predictor variables were the substrate type, tile height, and their interaction, and a random effect of tile ID was included. 3.2.4. Community structure on rubble and its link to coral settlement and recruitment To determine the overall effect of competitors and facilitators on coral settlement and recruitment rates, a generalised mixed-effects model was run for each reef. The percentage cover of each of the three categories of rubble encrusters, i.e. bare space, CCA, and competitors, was included as explanatory variables. Interactions between each category and substrate were also included, as the effect of each encrusting category might vary with substrate. A Poisson distribution was used for the response variable (count data), employing a log link function. The rubble surface area of each piece was also included as an offset. This analysis was completed on a subset of the rubble pieces (253/1869 pieces), for which we had confidence in the photo quality and identification of the encrusting community. For each reef, a PERMANOVA was conducted to determine whether the community composition (3 categories) of the rubble pieces varied between substrates, tile heights or time of deployment (3 months vs. 12 months), including the explanatory factors. To downweigh the importance of the dominant space occupiers, percentage covers were square-root transformed prior to the construction of a dissimilarity matrix using Bray-Curtis. SIMPER (Similarity Percentage analysis) was then utilised to determine the top contributing categories to significant differences in community composition between levels of the explanatory factors. Community analyses were conducted in PRIMER7 (PRIMER-e). 3.2.5. Sedimentation Two linear mixed-effects models were run. One for the two rubble beds of Heron Reef and one for the two substrates (interlocked rubble and hard carbonate) of Wistari Reef. Based on the structural composition of rubble comprising the interlocked rubble bed, we hypothesised that sediment deposition would be lower compared to the other two substrates. Therefore, we employed a one-tailed test to assess this directional effect with date included as a random effect (for the Heron Reef model) to account for temporal variation (i.e. deployment trials from September 2022 to September 2023). The comparison between the interlocked rubble and hard carbonate at Wistari was left as 2-tailed as we did not have an a priori hypothesis. The models used the total amount of deposited sediment collected as the response variable and substrate as the predictor variable. 3.2.6. Flow A linear mixed-effects model was used to assess the rate of dissolution (flow) across combinations of substrate type (loose vs. interlocked rubble bed) and cube treatment (surface vs. buried), with month included as a random effect to account for temporal variation, rate of dissolution as the response variable and substrate and cube treatments as the predictor variables. We again employed a one-tailed test to evaluate our hypotheses: i) flow was greater in the loose rubble compared to the interlocked, therefore surface cubes deployed in the loose bed would have a greater dissolution rate; ii) due to greater void space present in the interlocked bed, buried cubes would have a greater dissolution rate compared to those buried in the densely packed rubble comprising the loose rubble bed; iii) surface cubes in the loose bed would have a greater dissolution rate compared to those buried in the loose rubble; and iv) surface cubes and buried cubes in the interlocked rubble bed would result in comparable rates of dissolution. Results 4.1. Coral settlement and recruitment 4.1.1. Loose rubble vs. Interlocked rubble (Heron) Settlement to benthic tiles was higher in the interlocked rubble than in the loose rubble ( P <0.0001). The settlement of corals on control (elevated) tiles did not differ between substrates ( P = 0.07), implying a similar supply of larvae to both substrates. Although the primary purpose of the elevated tiles was to test for differences in larval supply between rubble treatments, it is interesting to compare settlement patterns to those on the benthos. The difference in settlement between elevated and benthic tiles differed between substrates but was always greater on elevated tiles (Figure 2a). Within the loose rubble bed, settlement to benthic tiles was approximately one-quarter that of the elevated tiles ( P <0.0001) (Figure 2a). In the interlocked rubble, settlement on benthic tiles comprised less than half the level observed on elevated tiles in the same substrate ( P 90% across all substrates and tile height treatments over the 9 months (Figure 3b). Though the probability of mortality on benthic tiles between the two rubble substrates was comparable (Figure 2b), the number of coral recruits was still marginally greater on benthic tiles within the interlocked rubble compared to the loose rubble ( P = 0.05, Figure 2c). For elevated tiles, the probability of mortality was higher in interlocked rubble than loose rubble ( P = 0.006, Figure 2b), but the number of coral recruits remained comparable on the elevated tiles across the two rubble beds ( P = 0.06, Figure 2c). 4.1.2. Interlocked rubble vs Hard carbonate-(Wistari) Settlement within the interlocked rubble and hard carbonate substrates of Wistari was once again higher in the more stable substrate. There was 1 more settler per rubble piece on tiles within the hard carbonate than in the interlocked rubble ( P = 0.008, Figure 3a). Like Heron, the settlement of corals on control (elevated) tiles was similar between substrates ( P = 0.8, Figure 3a), suggesting similar larval supply rates, and coral settlement was greater on elevated than benthic tiles in both substrates (interlocked: P 90%) across tile heights and substrates (Figure 3b). Unlike Heron, where recruitment on benthic tiles was higher in the more stable substrate, coral recruitment was similar on benthic tiles between interlocked rubble and hard carbonate (Figure 3c). 4.3. Community structure on rubble concerning coral settlement and recruitment The relationship between coral settlement and the cover of either CCA or bare space varied among habitat types ( P = 0.03) and ( P = 0.001), respectively (Figure 4a&b). Coral settlement was weakly associated with CCA in the interlocked rubble bed and hard carbonate (Figure 4a). However, settlement increased strongly in the loose rubble bed as the coverage of CCA increased (Figure 4a). Positive associations between settlement and bare space were found in the loose rubble bed and hard carbonate (Figure 4b), but settlement declined with greater bare space in the interlocked rubble substrate. Across all substrates, tile heights, and periods of deployment, space on rubble pieces was dominated by coral competitors (Figures 5 and 6). Bare space (with biofilms) was the biggest contributing factor to the difference in the rubble-encrusting community between benthic and elevated tiles at three months post-deployment in each of the substrates (Tables 1 and 2). Availability of bare space at three months was more prevalent on benthic tiles compared to elevated tiles, regardless of substrate (Tables 1 and 2). At 12 months post-deployment, crustose coralline algae (CCA) colonisation was the main factor differentiating rubble-encrusting communities on benthic and elevated tiles in all substrates except in the loose rubble bed. 4.3.1. Loose rubble vs. Interlocked rubble (Heron) At the three-month timepoint, communities were similar between benthic and elevated tiles in the loose rubble bed (Table 1). In the loose rubble bed, the main contributor to the difference in the community on benthic tiles over time ( P ( perm ) = 0.03) was CCA (Contributions = 47% and the cover of CCA on these tiles increased from three to 12 months (Table 1). Community composition in the interlocked rubble bed differed between benthic and elevated tiles at both time points (three months, P(perm) = 0.001), 12 months (P(perm) = 0.043, Table S1). At 3 months, bare space (contribution = 50%) was the primary contributor to differences in the encrusting community and had higher coverage on benthic tiles (Table 1). Table 1. Pair-wise test analysis of the difference in the composition of the rubble encrusting community per rubble piece as a response to the 3-way interaction of (rubble substrate x tile height x time of deployment) concerning each variable individually in the loose and interlocked rubble bed of Heron Reef. Where a significant difference in the encrusting community occurs between the interaction and specific variable is denoted with an asterisk (*) and in bold under the P-value column. The column furthest to the right includes results from the SIMPER analysis for each Pair-wise significant interaction. Given from top to bottom in this column is the rubble encrusting category that drove the difference in the composition of the community, the tile height, time of deployment, or substrate habitat where the greater average abundance of said rubble encrusting category occurred and the contribution of said rubble encrusting category driving the difference in the composition. PAIR-WISE TEST 3 WAY INTERACTION x Tile height HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Loose rubble bed Benthic Vs. Elevated tiles 3 months post-deployment 0.166 NA Interlocked rubble bed Benthic Vs. Elevated tiles 3 months post-deployment 0.001* Bare space Higher on: Benthic tiles Contribution: 50.7% 3 WAY INTERACTION x Time period HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Loose rubble bed Benthic 3 months Vs. 12 months 0.031* CCA Higher at: 3 months Contribution: 47.4% Interlocked rubble bed Benthic 3 months Vs. 12 months 0.001* Bare space Higher at: 3 months Contribution: 42% 3 WAY INTERACTION x Habitat HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Loose Vs. Interlocked rubble Benthic 3 months post-deployment 0.509 NA Loose Vs. Interlocked rubble Benthic 12 months post-deployment 0.001* CCA Higher in: Loose rubble Contribution: 39.6% Loose Vs. Interlocked rubble Elevated 3 months post-deployment 0.001* CCA Higher in: Loose rubble Contribution: 38.6% At three months, there was no difference in the rubble encrusting community on benthic tiles between rubble substrates. At 12 months, the difference in the community on benthic tiles between the loose and interlocked rubble beds was significant (P(perm) = 0.001) (Table 1). CCA colonisation was the largest contributor (contribution = 39%) to this difference, with a higher cover of CCA on benthic tiles in the loose rubble bed than in the interlocked rubble bed (Table 1). In contrast, at three months, the difference in encrusting communities on elevated tiles between the two rubble substrates was significant ( P ( perm) = 0.001) (Table 1), but not at 12 months (Table S1). 4.3.2. Interlocked rubble vs. Hard carbonate (Wistari) PERMANOVA and pair-wise tests analysis showed significant differences in the rubble-encrusting communities on benthic and elevated tiles in both the interlocked rubble bed and hard carbonate reef at three- and 12-month post-deployment, except for within the hard carbonate reef at three months. At three months, the encruster communities differed significantly between benthic and elevated tiles in both substrates (P(perm) = 0.004 within interlocked rubble and ( P(perm) = 0.001 within hard carbonate reef) (Table 2). The main factor driving these differences was the abundance of bare space, which was more abundant on benthic tiles in either substrate (46.4% contribution in interlocked rubble and 47% in hard carbonate) (Table 2). By twelve months, the community difference in the hard carbonate reef persisted (P(perm) = 0.002) (Table 2), with the primary factor being the colonisation of coralline algae (CCA), which was more abundant on benthic tiles (contribution = 40%) (Table 2). Apart from benthic tiles in the hard carbonated reef, the timing of tile deployment significantly affected the rubble-encrusting communities on different tile heights in each substrate. In the interlocked rubble bed, the community composition on benthic tiles differed significantly between three and 12 months ( P(perm) = 0.03) (Table 2), with the colonisation of CCA as the main contributor (contribution = 41%), the abundance was greater at 12 months than at three months post-deployment (Table 2). For the elevated tiles in both substrates, the communities also differed significantly between three and 12 months (P(perm) = 0.004) within interlocked rubble and ( P(perm) = 0.002) within hard carbonate reef) (Table 2), with bare space as the leading contributor (37% and 40%, respectively) (Table 2). Bare space was more abundant at 12 months compared to three months for the elevated tiles in both substrates. Table 4. Pair-wise test analysis of the difference in the composition of the rubble encrusting community per rubble piece as a response to the 3-way interaction of (rubble substrate x tile height x time of deployment) concerning each variable individually in the interlocked rubble bed and hard carbonate reef of Wistari Reef. Where a significant difference in the encrusting community occurs between the interaction and specific variable is denoted with an asterisk (*) and in bold under the P-value column. The column furthest to the right includes results from the SIMPER analysis for each Pair-wise significant interaction. Given from top to bottom in this column is the rubble encrusting category that drove the difference in the composition of the community, the tile height, time of deployment, or substrate habitat where the greater average abundance of said rubble encrusting category occurred and the contribution of said rubble encrusting category driving the difference in the composition. PAIR-WISE TEST 3 WAY INTERACTION x Tile height HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Interlocked rubble bed Benthic Vs. Elevated 3 months post- deployment 0.004* Bare space Higher on: Benthic tiles Contribution: 46.4% Hard carbonate reef Benthic Vs. Elevated 3 months post-deployment 0.001* Bare space Higher on: Benthic tiles Contribution: 47.8% 3 WAY INTERACTION x Time period HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Interlocked rubble bed Benthic 3 months Vs. 12 months 0.033* CCA Higher at: 3 months Contribution: 41.9% Hard carbonate reef Benthic 3 months Vs. 12 months 0.08 NA 3 WAY INTERACTION x Habitat HABITAT TILE HEIGHT TIME OF DEPLOYMENT P-VALUE SIMPER Interlocked rubble Vs. Hard carbonate reef Benthic 3 months post-deployment 0.091 NA Interlocked rubble Vs. Hard carbonate reef Benthic 12 months post-deployment 0.017* CCA Higher in: Interlocked rubble Contribution: 43.2% Interlocked rubble Vs. Hard carbonate reef Elevated 3 months post-deployment 0.04* CCA Higher in: Interlocked rubble Contribution: 40.5% In both the interlocked rubble bed and hard carbonate reef the rubble encrusting communities were significantly different between three- and 12 months post-deployment ( P(perm) = 0.004) and ( P(perm) = 0.002), respectively (Table 2), and bare space in both habitats was the leading contributor (contribution = 37%) and (contribution = 40%), respectively (Table 2). Bare space was more abundant at 12 months post-deployment than three for the elevated tiles in each substrate. From the PERMANOVA and pair-wise test analysis, substrate appeared to have a significant impact on the difference in the rubble encrusting communities on the tiles across each substrate at both three- and 12-months post-deployment except for the benthic tiles at three months (Table 2). However, as time progressed the difference in the rubble-encrusting communities on the benthic tiles in either substrate did become more variable. The rubble-encrusting community composition on benthic tiles across the interlocked rubble bed and hard carbonate reef significantly differed at 12 months post-deployment ( P(perm) = 0.017) (Table 2). 4.4. Sedimentation The linear mixed-effects model regarding the rubble beds of Heron Reef indicated that deposited sediment was greater in the loose rubble bed (mean = 8.13 g m² d⁻¹) compared to the interlocked rubble bed (mean = 7 g m² d⁻¹) ( P = 0.04) (Figure 7). The fixed effect estimate for the interlocked rubble bed was -1.16, indicating a decrease in sediment deposition relative to the loose bed. This supports our expectation that the interlocked rubble bed captures less sediment than the loose rubble bed. In contrast, sediment deposition did not differ significantly between the interlocked rubble and hard carbonate reef of Wistari ( P = 0.75) (Figure 7). The model estimated a mean sediment value of 11.2 g m² d⁻¹ collected on turfpods in the interlocked rubble bed and a mean of 13.2 in the hard carbonate, which was indistinguishable. 4.5. Flow The flow results did not support our initial hypothesis that flow would be greater in the loose rubble bed compared to the interlocked bed. As the mean dissolution of surface cubes in either bed was comparable (2.5 g in loose rubble and 2.4 g in interlocked rubble bed) ( P = 0.07) (Figure 8). Furthermore, the dissolution between buried cubes in either rubble bed was also comparable (2.2 g in loose rubble and 2.3 g in interlocked rubble bed) ( P = 0.4) (Figure 8). However, our hypothesis concerning the difference in flow exposure between surface cubes and buried cubes in the loose rubble bed was supported by our results. On average, the dissolution of surface cubes (2.5 g) was greater than that of the buried cubes (2.2 g) in the loose rubble bed ( P < 0.001) (Figure 8). Furthermore, our hypothesis that surface and buried cubes in the interlocked rubble bed would experience similar flow exposure was also supported by flow results. The average dissolution of surface cubes (2.4 g) was similar to that of the buried cubes (2.3 g) in the interlocked bed ( P = 0.07) (Figure 8). Discussion We examined how the environment associated with different substrates – loose rubble, interlocked rubble and hard carbonate - influences coral settlement and recruitment on the southern Great Barrier Reef (GBR). We find a distinct environmental effect associated with these substrates, particularly at the settlement stage at both Heron and Wistari Reefs; substrates of greater stability and complexity have higher settlement. Since the direct effects of rubble mobility were excluded by the experimental design, our results imply that the environments associated with reef and rubble substrates are sufficiently different to impacts of coral settlement and recruitment. Specifically, settlement was lower in the loose rubble than in the interlocked rubble of Heron Reef, and lower in the interlocked rubble than the hard carbonate of Wistari Reef. These patterns occur despite tiles in more stable substrates having equal or a higher cover of competing taxa encrusting the rubble. While there was high mortality at the post-settlement stage, coral recruitment remained higher on interlocked than loose rubble, suggesting that the interlocked rubble bed is more favourable. But recruitment to even more stable – hard carbonate- substrate appeared to offer no further benefit, as there was no difference in recruitment between interlocked and hard carbonate substrates at Wistari Reef. We conclude that the effects of loose and interlocked rubble beds on coral recruitment are not limited to rubble mobility and highlight that these effects are less pronounced for more stable interlocked beds. Similar settlement rates on elevated tiles in each substrate suggest that larval supply is comparable across substrates at both Heron and Wistari Reefs. This is important for our experimental inference. The lack of significant difference across elevated tile treatments, despite there being far higher settlement than on benthic tiles means that inferences on rubble habitats could be drawn directly from the settlement rates to benthic tiles. Settlement rates were higher on elevated tiles than benthic tiles regardless of substrate type, indicating that effects on settlement are greater at the substrate level and that rubble beds are unlikely to be recruitment-limited. The structural complexity of a rubble bed or hard carbonate reef is determined by rubble size, morphology, configuration, the reef rock structure, and coral cover. Reefs with low structural complexity have reduced turbulence in the boundary layer at the substrate level, while healthy, structurally complex reefs can have high drag coefficients and heightened turbulence and mixing water flow (Guihen et al., 2013 ). These hydrodynamic variations can have various flow-on effects that further impact the success of coral settlement, such as: inhibiting a coral larva’s ability to access the substratum (Hata et al., 2017), influencing sediment retention (Jones et al., 2015; Moeller et al., 2017 ), and affect access to nutrients of settled corals and other sessile marine organisms, impacting their growth and survival (Kenyon et al., 2023 ). The loose rubble bed has reduced structural complexity compared to the interlocked beds and hard carbonate reef due to differences in the rubble size, morphology, configuration, and the paucity of adult coral colony abundancies (Paewai-Huggins, pers. obvs. ). There may thus be a higher free-stream flow of water travelling across the low-rugosity, loose bed, but lower turbulence (Kenyon et al., 2023 ), leading to lower retention of coral larvae closer to the substrate (Sebens et al., 1998), ultimately reducing settlement. Dissolution measurements indicate that the loose rubble bed was at least occasionally exposed to higher flow conditions than those in the interlocked bed. Our results suggest that flow within the loose bed has the potential to exceed that of the interlocked bed, likely driven by differences in the configuration between rubble beds. Future studies would benefit from investigating flow differences at the time of spawning and settlement to better identify how flow influences larval settlement between rubble beds of varying configuration and complexity. Sedimentation can inhibit coral settlement or smother already settled corals, inhibiting post-settlement survival and growth (Babcock & Davies, 1991 ; Humanes et al., 2017 ; Moeller et al., 2017 ; Ama Wakwella et al., 2020 ) and is likely to differ between rubble bed types. The size and configuration of rubble pieces in beds create variation in void space (i.e., the size variation in the gaps between pieces) (Kenyon et al., 2024 ). Compared to the densely packed pieces in the loose bed, the larger void spaces in the interlocked beds may enable sediment to fall between rubble and away from settlers on the benthic tiles. Trapped deep in the interlocked matrix, less sediment would be resuspended here compared to the loose rubble bed. Coral settlement on rubble in loose rubble may be more exposed to deposited sediment on the topsides and the resuspension of sediment on the undersides, resulting in lower settlement and increased mortality. Our sedimentation results support this hypothesis, that the composition of the rubble comprising the loose bed makes sediment retention a more prominent concern for this type of rubble bed, likely negatively impacting coral settlement. In addition to sedimentation, the reduced turbulence and water flow around loose rubble compared to interlocked rubble might restrict particle capture and the mass transfer of nutrients reaching settlers. Flow is essential for coral metabolism (Blanchon et al., 1997 ; Nakamura et al., 2009 ; Wolfe et al., 2021 ) and provides planktonic food for heterotrophic feeding (Borell et al., 2008 ). Benthic tiles were positioned to be flush with the surrounding rubble. However, in the interlocked rubble bed, the larger void spaces allowed greater flow between rubble pieces and between the tile and the benthos, while the densely packed loose bed offered little space below the tiles. While our results don’t represent a strong difference in flow experienced by buried cubes between the two rubble beds, there is evidence to support that flow exposure was different for surface and buried cubes in the loose bed. Surface cubes experienced a significant increase in flow compared to those buried within the in-situ rubble. Suggesting the densely packed nature of the rubble may have prevented oxygen and nutrient-rich waters from passing across the underside of tiles, stunting the growth and survival of settled corals within the loose rubble bed, and leading to a higher probability of mortality and lower recruitment. In contrast, flow was comparable between buried and surface cubes in the interlocked rubble bed. Suggesting that the substrate configuration may improve flow penetration, delivering oxygen and nutrients to a larger surface area of the rubble, including the undersides of tiles, which may support increased survival and recruitment. In addition to flow, sedimentation, and nutrient transfer, competition with other sessile organisms can negatively impact coral settler growth and survival (Chong-Seng et al., 2014 ; Doropoulos et al., 2016 ; Gouezo et al., 2020). Ascidians and bryozoans are major rubble-dwelling taxa (Wolfe et al., 2021 ), taking advantage of the cryptic substrate provided by rubble (Wolfe et al., 2021 ) and have the potential to outcompete coral larvae for space, inhibiting settlement or increasing rates of mortality (Doropoulos et al., 2015). However, the composition of the rubble encrusting community appeared to have little influence on coral settlement and coral recruitment across all substrates. Thus, while rates of settlement and recruitment varied among treatments, rubble was always dominated by competitors, including ascidians, bryozoans, and sponges. Furthermore, settlement was always greater on elevated tiles, yet these consistently had less available settlement space (bare space). It appears that the role of competition is highly context dependent. For example, a Caribbean study found higher mortality of coral settlers with an increase in sessile invertebrate coverage (Arnold and Steneck, 2011), whereas a study in Palau found that competition from other benthic organisms tends to be less important than avoiding areas of high corallivory (Doropoulos et al., 2016 ). While mortality rates were similar between rubble beds (> 95%), settlement was still greater in the interlocked rubble compared to the loose rubble bed. Similarities among the mortality rates of corals across the two rubble beds suggest that the bottleneck to coral growth and survival in loose rubble occurs earlier, in the first three months. Though previous studies in rubble beds have also pointed to bottlenecks occurring in the early life stages (Cameron et al, 2016; Chong-Seng et al., 2014 ), causation was linked to high rubble mobility. However, in the present study, lower settlement and higher post-settlement mortality were still observed on rubble pieces despite the stable nature of the tiles. Stability is indeed important (Paewai-Huggins et al., 2025), but we reveal here that environmental effects also occur. The rubble configuration within the loose bed appears to pose challenges for larvae reaching and/or surviving on the tiles, through restricted turbulence, increased sediment retention, and/or limited nutrient transfer and anoxia. These factors likely contribute to significant setbacks in the early stages of settlement. Furthermore, they appear to disproportionately affect smaller, newly settled corals rather than later-stage recruits, as evidenced by the comparable survival rates between loose and interlocked beds for larger corals (between 3 and 12 months). These early-stage bottlenecks are likely to lead to lower coral cover in loose beds over time. Indeed, there were fewer larger coral colonies in the loose rubble bed. Interpreting coral recruitment rates between the interlocked rubble bed and the hard carbonate of Wistari is less straightforward. Though coral settlement was lower in the interlocked rubble than in the hard carbonate, coral recruitment was comparable after 12 months. Considering that sediment and the rubble encrusting community compositions were similar between substrates, greater settler abundance on benthic tiles in the hard carbonate than the interlocked bed may be related to a difference in the abundance of macroalgal cover on the in-situ rubble comprising the interlocked bed (Paewai-Huggins, pers. obs.) . Macroalgae can have several inhibiting mechanisms that negatively affect coral settler growth and survival (Chong-Seng et al., 2014 ), including via abrasion (Box & Mumby, 2007 ), reduced oxygen exchange (Finelli et al., 2006 ), and shading, which impacts the photosynthetic processes of zooxanthellae (Box & Mumby, 2007 ; Mundy & Babcock, 1998 ). Settling coral larvae have been shown to move away from local patches of brown macroalga Lobophora spp. (Evensen et al., 2019 ) and in some cases fail to settle on an entire ref when dominated by algae (Doropoulos et al., 2014 ). Conclusion Rubble mobility is the leading theory explaining low rates of survival and growth of corals in rubble beds. We do not attempt to challenge that notion, and indeed find evidence of important mobility effects (Paewai-Huggins et al., 2025). However, we also find that settlement bottlenecks appear to exist regardless of whether the rubble is stable. Thus, the surrounding rubble environment has important impacts on coral recruitment. The drivers of such recruitment failure are clearly influenced by the typology of rubble, and likely involve factors associated with flow and sedimentation. Yet understanding of these mechanisms remains in its infancy. Our results do, however, have implications for the likely success of restoration. Rubble stabilisation is a widely used approach to facilitate coral recovery (Ceccarelli et al., 2020 ). While promoting stability is indeed important, we also find that merely stabilising rubble will not guarantee success in rubble beds whose environment remains hostile to coral settlement and survival (e.g., where the rubble comprises small, loose pieces). Rubble characteristics beyond mobility should be considered when contemplating the utility of restoration methods for coral recovery. A standardised methodology for categorising rubble now exists (Kenyon et al., 2024 ), and its usage will help researchers synthesise outcomes clearly. Our study is far from globally representative, but it points to a wider issue that can be built on by the great diversity of restoration practitioners. Indeed, much can be learnt if practitioners take and report field measurements of flow and sedimentation to help interpret the outcomes of their interventions and collectively obtain a holistic understanding of the drivers of coral recruitment on rubble. Declarations Author Contribution P. M. assisted in the conception, experimental design, analysis and interpretation. P.M. was also involved in the revisions and assisted in data collection.T. K. assisted in the conception, design, analysis and interpretation. T.K. was also involved in the revisions and assisted in data collection. R.P.H. lead experimental design, deployment, data collection, analysis and interpretation. R.P.H. also wrote the main manuscript text and prepared figures 1-8. Acknowledgement We'd firstly like to acknowledge the Gooreng Gooreng, Gurang, Bailai and Taribelang Bunda peoples in the sea country of the Southern Great Barrier Reef, where this fieldwork took place. We'd like to also acknowledge the staff and team of the Heron Island Research center for their support and assistance in the field and laboratory. Data Availability All data analysis files and corresponding datasets have been deposited in GitHub: https://github.com/Roima25/FirstPaper_Data References Babcock, R., & Davies, P. (1991). Effects of sedimentation on settlement of Acropora millepora. Coral reefs , 9 , 205-208. Babcock, R., & Smith, L. (2002). Effects of sedimentation on coral settlement and survivorship. Proceedings of the Ninth International Coral Reef Symposium, Bali, 23-27 October 2000, Barton, K. (2009). MuMIn: multi-model inference. http://r-forge . r-project. org/projects/mumin/ . Blanchon, P., Jones, B., & Kalbfleisch, W. (1997). Anatomy of a fringing reef around Grand Cayman; storm rubble, not coral framework. Journal of Sedimentary Research , 67 (1), 1-16. Borell, E. M., Yuliantri, A. R., Bischof, K., & Richter, C. (2008). The effect of heterotrophy on photosynthesis and tissue composition of two scleractinian corals under elevated temperature. Journal of Experimental Marine Biology and Ecology , 364 (2), 116-123. Box, S. J., & Mumby, P. J. (2007). Effect of macroalgal competition on growth and survival of juvenile Caribbean corals. Marine Ecology Progress Series , 342 , 139-149. Ceccarelli, D. M., McLeod, I. M., Boström-Einarsson, L., Bryan, S. E., Chartrand, K. M., Emslie, M. J., Gibbs, M. T., Gonzalez Rivero, M., Hein, M. Y., & Heyward, A. (2020). Substrate stabilisation and small structures in coral restoration: State of knowledge, and considerations for management and implementation. Plos one , 15 (10), e0240846. Chong-Seng, K. M., Graham, N. A. J., & Pratchett, M. S. (2014). Bottlenecks to coral recovery in the Seychelles. Coral reefs , 33 (2), 449-461. https://doi.org/10.1007/s00338-014-1137-2 Connell, J. H., Hughes, T. P., & Wallace, C. C. (1997). A 30‐year study of coral abundance, recruitment, and disturbance at several scales in space and time. Ecological monographs , 67 (4), 461-488. Dollar, S. J., & Tribble, G. W. (1993). Recurrent Storm Disturbance and Recovery - a Long-Term Study of Coral Communities in Hawaii. Coral reefs , 12 (3-4), 223-233. https://doi.org/Doi 10.1007/Bf00334481 Doropoulos, C., Roff, G., Bozec, Y. M., Zupan, M., Werminghausen, J., & Mumby, P. J. (2016). Characterizing the ecological trade-offs throughout the early ontogeny of coral recruitment. Ecological monographs , 86 (1), 20-44. https://doi.org/10.1890/15-0668.1 Doropoulos, C., Roff, G., Zupan, M., Nestor, V., Isechal, A. L., & Mumby, P. J. (2014). Reef-scale failure of coral settlement following typhoon disturbance and macroalgal bloom in Palau, Western Pacific. Coral reefs , 33 (3), 613-623. Evensen, N. R., Doropoulos, C., Morrow, K. M., Motti, C. A., & Mumby, P. J. (2019). Inhibition of coral settlement at multiple spatial scales by a pervasive algal competitor. Marine Ecology Progress Series , 612 , 29-42. Field, M. E., Chezar, H., & Storlazzi, C. D. (2013). SedPods: a low-cost coral proxy for measuring net sedimentation. Coral reefs , 32 (1), 155-159. https://doi.org/10.1007/s00338-012-0953-5 Finelli, C. M., Helmuth, B. S., Pentcheff, N. D., & Wethey, D. S. (2006). Water flow influences oxygen transport and photosynthetic efficiency in corals. Coral reefs , 25 , 47-57. Fox, H. E. (2004). Coral recruitment in blasted and unblasted sites in Indonesia: assessing rehabilitation potential. Marine Ecology Progress Series , 269 , 131-139. https://doi.org/DOI 10.3354/meps269131 Fox, H. E., & Caldwell, R. L. (2006). Recovery from blast fishing on coral reefs: A tale of two scales. Ecological Applications , 16 (5), 1631-1635. https://doi.org/Doi 10.1890/1051-0761(2006)016[1631:Rfbfoc]2.0.Co;2 Fox, H. E., Pet, J. S., Dahuri, R., & Caldwell, R. L. (2003). Recovery in rubble fields: long-term impacts of blast fishing. Marine Pollution Bulletin , 46 (8), 1024-1031. https://doi.org/10.1016/S0025-326x(03)00246-7 Google Earth. (2021). Heron Island Reef. Heron Island - Bing Maps Guihen, D., White, M., & Lundälv, T. (2013). Boundary layer flow dynamics at a cold-water coral reef. Journal of sea research , 78 , 36-44. Harrington, L., Fabricius, K., De'Ath, G., & Negri, A. (2004). Recognition and selection of settlement substrata determine post-settlement survival in corals. Ecology , 85 (12), 3428-3437. https://doi.org/Doi 10.1890/04-0298 Heyward, A., & Negri, A. (1999). Natural inducers for coral larval metamorphosis. Coral reefs , 18 (3), 273-279. Humanes, A., Fink, A., Willis, B. L., Fabricius, K. E., de Beer, D., & Negri, A. P. (2017). Effects of suspended sediments and nutrient enrichment on juvenile corals. Marine Pollution Bulletin , 125 (1-2), 166-175. Kenyon, T. M., Doropoulos, C., Dove, S., Webb, G. E., Newman, S. P., Sim, C. W., Arzan, M., & Mumby, P. J. (2020). The effects of rubble mobilisation on coral fragment survival, partial mortality and growth. Journal of Experimental Marine Biology and Ecology , 533 , 151467. Kenyon, T. M., Doropoulos, C., Wolfe, K., Webb, G. E., Dove, S., Harris, D., & Mumby, P. J. (2023). Coral rubble dynamics in the Anthropocene and implications for reef recovery. Limnology and Oceanography , 68 (1), 110-147. Kenyon, T. M., Eigeland, K., Wolfe, K., Paewai‐Huggins, R., Rowell, D., Dodgen, T., & Mumby, P. J. (2024). Material Legacies on Coral Reefs: Rubble Length and Bed Thickness Are Key Drivers of Rubble Bed Recovery. Global change biology , 30 (11), e17574. Latrille, F. X., Tebbett, S. B., & Bellwood, D. R. (2019). Quantifying sediment dynamics on an inshore coral reef: putting algal turfs in perspective. Marine Pollution Bulletin , 141 , 404-415. Lee, C. S., Walford, J., & Goh, B. P. L. (2009). Adding coral rubble to substrata enhances settlement of Pocillopora damicornis larvae. Coral reefs , 28 (2), 529-533. https://doi.org/10.1007/s00338-009-0467-y Moeller, M., Nietzer, S., Schils, T., & Schupp, P. J. (2017). Low sediment loads affect survival of coral recruits: the first weeks are crucial. Coral reefs , 36 , 39-49. Mundy, C., & Babcock, R. (1998). Role of light intensity and spectral quality in coral settlement: implications for depth-dependent settlement? Journal of Experimental Marine Biology and Ecology , 223 (2), 235-255. Mundy, C. N. (2000). An appraisal of methods used in coral recruitment studies. Coral reefs , 19 (2), 124-131. https://doi.org/DOI 10.1007/s003380000081 Nakamura, Y., Shibuno, T., Lecchini, D., Kawamura, T., & Watanabe, Y. (2009). Spatial variability in habitat associations of pre-and post-settlement stages of coral reef fishes at Ishigaki Island, Japan. Marine Biology , 156 , 2413-2419. Paewai-Huggins, R., Kenyon, T.M., & Mumby, P.J., (2025b). The effect of rubble stability on coral settlement and recruitment. Pre-print, Research Sqaure, 10.21203/rs.3.rs-7974089/v1 Rasser, M. W., & Riegl, B. (2002). Holocene coral reef rubble and its binding agents. Coral reefs , 21 (1), 57-72. https://doi.org/10.1007/s00338-001-0206-5 Raymundo, L., Maypa, A., Gomez, E., & Cadiz, P. (2007). Can dynamite-blasted reefs recover? A novel, low-tech approach to stimulating natural recovery in fish and coral populations. Marine Pollution Bulletin , 54 (7), 1009-1019. Roth, F., Saalmann, F., Thomson, T., Coker, D. J., Villalobos, R., Jones, B., Wild, C., & Carvalho, S. (2018). Coral reef degradation affects the potential for reef recovery after disturbance. Marine Environmental Research , 142 , 48-58. Salinas-de-León, P., Dryden, C., Smith, D., & Bell, J. (2013). Temporal and spatial variability in coral recruitment on two Indonesian coral reefs: consistently lower recruitment to a degraded reef. Marine Biology , 160 (1), 97-105. Sánchez-Quinto, A., & Falcón, L. I. (2019). Metagenome of Acropora palmata coral rubble: Potential metabolic pathways and diversity in the reef ecosystem. Plos one , 14 (8), e0220117. Stewart, H. L., Holbrook, S. J., Schmitt, R. J., & Brooks, A. J. (2006). Symbiotic crabs maintain coral health by clearing sediments. Coral reefs , 25 , 609-615. Storlazzi, C. D., Field, M. E., & Bothner, M. H. (2011). The use (and misuse) of sediment traps in coral reef environments: theory, observations, and suggested protocols. Coral reefs , 30 (1), 23-38. https://doi.org/10.1007/s00338-010-0705-3 Viehman, S., Hench, J. L., Griffin, S. P., Malhotra, A., Egan, K., & Halpin, P. N. (2018). Understanding differential patterns in coral reef recovery: chronic hydrodynamic disturbance as a limiting mechanism for coral colonization. Marine Ecology Progress Series , 605 . https://doi.org/10.3354/meps12714 Wakwella, A., Mumby, P. J., & Roff, G. (2020). Sedimentation and overfishing drive changes in early succession and coral recruitment. Proceedings of the Royal Society B , 287 (1941), 20202575. Wakwella, A., Mumby, P. J., & Roff, G. (2020). Sedimentation and overfishing drive changes in early succession and coral recruitment. Proceedings of the Royal Society B-Biological Sciences , 287 (1941). https://doi.org/ARTN 20202575 10.1098/rspb.2020.2575 Wolfe, K., Kenyon, T. M., & Mumby, P. J. (2021). The biology and ecology of coral rubble and implications for the future of coral reefs. Coral reefs , 40 (6), 1769-1806. Additional Declarations No competing interests reported. Supplementary Files Appendix.docx Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-7993495","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":542307513,"identity":"da7e3dc0-9d4b-4cd5-be40-0609d8147fca","order_by":0,"name":"Roima Paewai-Huggins","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABEElEQVRIiWNgGAWjYBADHgMQmcDAIAfhkqLFmGgtDAZQOrGBkBbzBt6DHz622cmYS6RffvFwR136huMJjA/etjHIGxzArkXmAF+y5My2ZB7LGTllFolnDuduOPOA2XBuG4PhBhxaJIC+kObdxsxjcCMnzSCx7UDuhhsJbNK8bQyMeLQY//67rR6mpS7d4EYC+2+gFns8WsykGbcdBmpJP/wgsY05AaiFjRmoJRGnFma+NMvef8d5DM68YWNIbDtsOPPMw2bJOeckkmfi0sLee/jGjzPV9gbH0x9//NlWJ893PPnghzdlNrZ9OLQwMMOjgMdMAsIAR40EDvVglTAG++MPEEYCHtWjYBSMglEwEgEAAVNeRFaCIqgAAAAASUVORK5CYII=","orcid":"","institution":"The University of Queensland","correspondingAuthor":true,"prefix":"","firstName":"Roima","middleName":"","lastName":"Paewai-Huggins","suffix":""},{"id":542307514,"identity":"fcb5fd0f-0cbb-4162-a5d3-9f8149c7d033","order_by":1,"name":"Tania M. 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1","display":"","copyAsset":false,"role":"figure","size":610121,"visible":true,"origin":"","legend":"\u003cp\u003eFieldwork sites, rubble beds, and rubble tiles: a) Heron Island Reef and Wistari Reef (Google Earth, 2021). The Heron Reef site contains a loose and interlocked rubble bed. The Wistari Reef site contains the second interlocked rubble bed and the hard carbonate reef; b) a close-up of the loose rubble, and c) a close-up of the interlocked rubble; d) the benthic rubble tiles (flush with the underlying substrate); and e) the elevated tiles (raised 20cm above the underlying substrate).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/8dac68ad0c565a1f358573a7.png"},{"id":95929971,"identity":"4e181bd7-2b84-4917-bda7-2dc645a14a1b","added_by":"auto","created_at":"2025-11-14 14:22:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":193983,"visible":true,"origin":"","legend":"\u003cp\u003eCoral settlement (mean ± SE) (a) at three months post-deployment; (b) the probability of post-settlement mortality (mean ± SE) of coral settlers from three to 12 and (c) coral recruitment (mean ± SE) at 12 months post-deployment, on the benthic and elevated tiles in the loose and interlocked rubble bed, Heron Reef. Differing letters indicate significance.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/8e21167c0ed926ef303d5cb8.png"},{"id":96245202,"identity":"d85a30a1-5567-4a0f-b338-7ba9104ae157","added_by":"auto","created_at":"2025-11-19 07:20:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":191902,"visible":true,"origin":"","legend":"\u003cp\u003eCoral settlement (mean ± SE) (a) at three months post-deployment; (b) the probability of post-settlement mortality (mean ± SE) of coral settlers from three to 12 and (c) coral recruitment (mean ± SE) at 12 months post-deployment, on the benthic and elevated tiles in the interlocked rubble bed and hard carbonate of Wistari Reef. Differing letters indicate significance.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/fb18fe98df808a883ec60c07.png"},{"id":95929970,"identity":"10818c64-7681-4bec-8202-23a4aed26464","added_by":"auto","created_at":"2025-11-14 14:22:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":134015,"visible":true,"origin":"","legend":"\u003cp\u003eCoral settlement per rubble piece comprising the rubble recruitment tiles in response to the interaction between the amount (%) of a) CCA coverage and b) bare space coverage pooled across tiles (benthic and elevated) in each of the three substrates.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/40404c805b728c4ae0f27ae4.png"},{"id":95929974,"identity":"ea9462c1-e86b-4331-ad93-3fa4f0f4b43a","added_by":"auto","created_at":"2025-11-14 14:22:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":230471,"visible":true,"origin":"","legend":"\u003cp\u003eThe percentage of space colonized by rubble encrusting organisms: bare space, CCA, and competitors on the rubble pieces comprising the benthic and elevated tiles in the loose and interlocked rubble beds at three months post-deployment and 12 months post-deployment on Heron Reef.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/1a7394e629e3889d76ef4793.png"},{"id":95929984,"identity":"f0b0e6cd-66db-499a-ad66-4b8133173db3","added_by":"auto","created_at":"2025-11-14 14:22:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":207795,"visible":true,"origin":"","legend":"\u003cp\u003eThe percentage of space colonized by rubble encrusting organisms: bare space, CCA, and competitors on the rubble pieces comprising the benthic and elevated tiles in the interlocked rubble bed and hard carbonate reef at three months post-deployment and 12 months post-deployment on Wistari Reef.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/56465954eb3994fda0e01d0c.png"},{"id":96244319,"identity":"aa51e072-b68b-4488-b2a7-dab7d9424960","added_by":"auto","created_at":"2025-11-19 07:18:07","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":146179,"visible":true,"origin":"","legend":"\u003cp\u003eDeposited sediment (mean ± SE) collected on the turfpods in the loose and interlocked rubble beds at Heron Reef and in the interlocked bed and hard carbonate reef at Wistari Reef.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/5ef240c98ad1b12b479cc034.png"},{"id":96245262,"identity":"7c953a60-a606-4213-8057-14fd2c73d7e4","added_by":"auto","created_at":"2025-11-19 07:20:10","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":136273,"visible":true,"origin":"","legend":"\u003cp\u003eAverage (mean ± SE) dissolution (g) of plaster-of-Paris flow cube treatments (buried and surface) in the loose rubble bed and interlocked rubble bed at Heron Reef.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/1ed8a1076242d3bfd5eb6ee7.png"},{"id":100807109,"identity":"5b25e89c-c751-44fc-9ebb-27a044d4e946","added_by":"auto","created_at":"2026-01-21 14:57:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2941997,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/e111ea50-13b0-4f91-941f-b68e98268374.pdf"},{"id":96245540,"identity":"0313aa95-16cd-4751-bafe-46e5b78ec382","added_by":"auto","created_at":"2025-11-19 07:20:53","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2041343,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix.docx","url":"https://assets-eu.researchsquare.com/files/rs-7993495/v1/8f18c81db3eef0c64d237b08.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Instability is not the only driver of rubble impacts on coral settlement and recruitment","fulltext":[{"header":"Introduction","content":"\u003cp\u003eReefs are in constant flux between bioconstruction and erosion through the biological growth of corals, coral mortality, and physical and biological erosion of the framework, whereby corals transition from dead coral to rubble and sand (Wolfe et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The balance of reef building and erosion is driven by the frequency and severity of disturbances and the tolerance of the coral assemblage experiencing the disturbance (Dollar \u0026amp; Tribble, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Fox \u0026amp; Caldwell, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Rasser \u0026amp; Riegl, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Overfishing, mass bleaching events, disease, and ocean acidification are impacting coral reefs on a global scale (Roth et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Salinas-de-Le\u0026oacute;n et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; S\u0026aacute;nchez-Quinto \u0026amp; Falc\u0026oacute;n, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Viehman et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; A. Wakwella et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Specific impacts can diminish the structural complexity of reefs by breaking up and eroding the coral framework into rubble. Wave energy from storm disturbances such as cyclones, hurricanes, and tsunamis has resulted in vast rubble beds (Blanchon et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Viehman et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Similarly, coral bleaching, ship groundings, and coral disease can reduce reefs to rubble (Ceccarelli et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThough rubble production is part of the natural cycle of reef accretion and erosion, the rate of conversion of living coral reefs into rubble beds is increasing as impacts amplify in severity and frequency on a global scale (Ceccarelli et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; S\u0026aacute;nchez-Quinto \u0026amp; Falc\u0026oacute;n, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Repeated or chronic disturbances, both natural and anthropogenic, can have long-lasting effects and hinder the recovery of coral cover (Fox et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Rasser \u0026amp; Riegl, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Viehman et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Coral rubble, as a settlement substrate, is considered suitable for both coral settlement and many other sessile marine invertebrates due to microscale rugosity and the presence of necessary biofilms (Harrington et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Heyward \u0026amp; Negri, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Lee et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Mundy, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). However, depending on the type, intensity, and time since disturbance, generated rubble can vary in size, morphology, and bed depth, affecting the stability of rubble pieces and the physical characteristics of the rubble bed (Wolfe et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Rubble has been termed as \u0026lsquo;killing fields\u0026rsquo; for corals due to the unconsolidated nature of the rubble substrate and its mobilisation with waves and currents (Ceccarelli et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Fox 2002)\u003c/p\u003e\u003cp\u003eLow levels of post-settlement survival for coral settlers in rubble beds have been attributed primarily to the instability of rubble pieces (Fox, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Fox \u0026amp; Caldwell, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Raymundo et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Yet, many other environmental and ecological factors might vary among rubble bed typologies and could contribute to decreased coral recruitment in rubble beds. Examples include increased sedimentation rates, increased competition from other sessile benthic organisms, or decreased settlement-inducing chemical cues from groups such as crustose coralline algae (Doropoulos et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; A. Wakwella et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Because rubble beds have a dramatically different structure than healthy reefs, many of the key studies on rubble function have focused on the contrast between \u0026lsquo;rubble beds\u0026rsquo; and coral-dominated reefs (Chong-Seng et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Fox, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). With renewed interest in the role of rubble and a potential increase in rubble generation, it is important to disaggregate the types of rubble habitats and explore their dynamics explicitly.\u003c/p\u003e\u003cp\u003eThis study includes two types of rubble beds. The first is composed of smaller, non-branched rubble pieces (herein referred to as the loose rubble bed). The size and morphology of these rubble pieces create a more densely packed and flat rubble substrate, and are likely more prone to rubble mobility (Kenyon et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Kenyon et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The second is composed of large, branched rubble pieces (herein referred to as the interlocked rubble bed). The size and morphology create an interlocking configuration of rubble, resulting in a relatively stable and structurally complex substrate (Kenyon et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Here, we wish to understand how the environment associated with different rubble beds influences coral settlement and recruitment (i.e., to remove the influence of rubble mobility). In doing so, our study examines associations between benthic habitats and their immediate environment (flow, sedimentation, etc.) and how these affect coral recruitment. Moreover, our results may provide insight into the potential benefits of \u0026lsquo;rubble stabilisation methods\u0026rsquo;, because while they may solve the mobility problem, they are less likely to alter other environmental drivers that might still constrain coral recovery. We examine the importance of rubble stability in a separate study (Paewai-Huggins et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025b\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Study sites\u003c/h2\u003e\u003cp\u003eThis study was carried out at two reefs -Heron and Wistari (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) \u0026ndash; in the vicinity of Heron Island, in the sea country of the Gooreng Gooreng, Gurang, Bailai and Taribelang Bunda peoples of the Southern Great Barrier Reef. A significant limitation of studying rubble beds in the Heron reef complex is that patches of rubble are infrequent and widely separated. This makes it difficult to identify replicate rubble treatments in the same overall physical wave environment, and allowing treatments to occur in different environments is likely to impact their stability and biology (Wolfe et al., 2023). Therefore, it was necessary to identify two locations (Heron and Wistari Reefs) where at least two rubble substrates could be compared within a similar physical environment. Yet even holding wave exposure similar \u0026ndash; by choosing sites within ca 200 m \u0026ndash; there is a significant likelihood that local hydrodynamic processes would alter larval supply to the vicinity of substrates being compared (e.g., loose rubble vs interlocked rubble at Heron Reef). Thus, we have two tile height treatments, benthic tiles, deployed to be flush with the substrate in each habitat and elevated tiles, raised 20 cm above the substrate. Benthic tiles allow us to investigate impacts influencing settlement and recruitment rates, directly related to differences between the benthic substrates of each habitat. While the elevated tiles allowed us to quantify varying patterns in larval supply between habitats, not associated with the composition of the substrate, and if necessary, adjust our interpretation of the settlement on benthic tiles.\u003c/p\u003e\u003cp\u003eThough the exact type of disturbance that created either the loose or interlocked rubble beds of Heron Reef is unknown, it is presumed that much of the rubble production within this region is a result of cyclone activity passing through the channel between Heron Reef and Wistari Reef (Connell et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). The difference in the typology of either rubble bed is hard to determine accurately. Still, it could be an accumulation of a variety of factors, such as the type of predominant coral cover within each area prior to any disturbance or perhaps the geomorphological structure of the reef pre-disturbance, causing the smaller non-branched rubble of the loose bed to accumulate in between areas comprised of the larger, branched rubble of the interlocked bed.\u003c/p\u003e\u003cp\u003eThe first site, Heron Reef, was located at 8\u0026ndash;9 m depth and included rubble substrates of two types, located 200 m apart: 1) an unstable rubble bed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) due to the composition of loose and largely unbound rubble pieces (\u0026lsquo;loose\u0026rsquo; rubble bed) and 2) a relatively more stable rubble bed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ec) with larger, interlocked and commonly bound pieces (\u0026lsquo;interlocked\u0026rsquo; rubble bed).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe rubble in the loose rubble bed is relatively small in length and diameter, i.e., 7.6cm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74 (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE) and 1cm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE), respectively. Most pieces in this bed do not have branches, are more densely packed, have small gaps/void spaces between the individual pieces, and are easily picked up from the substrate without interference from interlocking or burial, indicating they are vulnerable to mobilisation (Kenyon et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Kenyon et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The interlocked rubble bed includes large, branching rubble pieces averaging 15.9cm\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE) in length and 1.7cm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE) in diameter. Individual pieces are more challenging to pick up, often needing to be twisted carefully or broken to separate them from other pieces with which they are interlocked. Due to the size and branching morphology of the rubble pieces, there are larger void spaces between individual pieces, creating a more structurally complex rubble bed (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003eThe site on Wistari Reef, also at an 8\u0026ndash;9 m depth, comprised two different substrates: 1) an interlocked rubble bed (See Appendix Fig.\u0026nbsp;1) like that found at the Heron site and 2) a stable hard carbonate reef, located within 100 m of one another (See Appendix Fig.\u0026nbsp;1). The interlocked rubble bed at Wistari Reef has similar physical attributes to the interlocked rubble bed at Halfway, with large, branched rubble pieces. The hard carbonate reef habitat is a stable substrate that is part of the coral reef framework.\u003c/p\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003e3.1.2. Recruitment tile construction and deployment\u003c/h2\u003e\u003cp\u003eRubble recruitment tiles were produced to mimic the rubble substrate faithfully. These comprised 180mm x 180mm stainless steel mesh onto which rubble pieces collected from the field were cable-tied in pairs. Before attachment, rubble pieces were cleaned with fresh water, bleached overnight to remove living material, rinsed again, and dried in sunlight. Rubble pieces were placed to cover the tiles comprehensively, and, because their size varied, the number of rubble pieces used per tile ranged from 10\u0026ndash;24. Each tile was given a unique ID tag.\u003c/p\u003e\u003cp\u003eTo allow the rubble tiles to be conditioned and develop a biofilm, they were deployed over 3 days from October 13\u0026ndash;15, 2021, ~\u0026thinsp;4.5 weeks before the spawning event at Heron and Wistari reefs. Within each substrate, 40 tiles were deployed, totalling 160. At each substrate, 20 tiles were placed flush with the substrate (herein referred to as benthic tiles) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ed), and 20 of the tiles were raised 20cm above the substrate (herein referred to as elevated tiles) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003ee). Tiles were deployed and attached to the substrate using basalt reinforcing bar stakes (1m), in an area that measured 5m x 5m. Elevated tiles acted as controls to detect potential differences in larval supply between the rubble bed (e.g., loose vs interlocked rubble vs. interlocked rubble) that would influence coral settlement. For example, if larval supply, measured on the elevated tiles, was comparable between loose and interlocked rubble beds, then any difference in settlement observed on benthic tiles placed directly on the rubble benthos could be attributed to differences in the local rubble environment (rather than external differences in access to larvae because of, say, flow).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3. Rubble tile collection and inspection\u003c/h2\u003e\u003cp\u003eThe first collection of rubble tiles occurred in January 2022, ~\u0026thinsp;4 months after deployment, to determine coral settlement (within three months of the 2021 spawning event). The collection of tiles took a total of nine days from January 12th to the 20th. Rubble tiles were collected and returned to the lab, and held in tanks with flow-through ambient seawater. Coral settlers were observed using an Olympus SZ dissection microscope while held in shallow seawater. Each piece of rubble was removed from the metal mesh grid, both sides were photographed, and the piece was measured (the diameter of the centre and length, from which we used to calculate the surface area of each rubble piece). Each rubble piece was assigned a reference point, i.e., one end of the rubble piece, so that the distance from the reference point to each coral settler could be recorded. The settler\u0026rsquo;s location on either the topside, sides, or underside of the rubble piece was noted, as well as the condition of the coral settler, as alive, dead, or partially dead. The presence of any other sessile organisms growing near, touching, or covering the coral settler was also noted. Before inspection, each tile was photographed, and the top and underside were mapped with a unique letter and number code for each rubble piece so that rubble pieces could be reattached precisely in the exact location and orientation. Pieces of rubble were kept in seawater during the entirety of the inspection.\u003c/p\u003e\u003cp\u003eThe rubble tiles were redeployed to their original stakes, where they remained until recollection, which occurred in September and October 2022, to investigate post-settlement survival and recruitment within 12 months of the 2021 spawning event. The investigation of coral recruitment followed the same procedures as above. Using the maps of the rubble tiles and the documented location of each coral settler in January/February 2022, the presence or absence of the settler in September/October was documented.\u003c/p\u003e\u003cp\u003ePhotos of rubble pieces were also used to identify the percentage cover of sessile invertebrates and algal species that encrusted rubble pieces and to determine any potential competitors for space that may impact corals' settlement or recruitment rates. This study separated the rubble-encrusting organisms into three categories: \u0026lsquo;bare space\u0026rsquo; (space on the rubble that was covered only by endolithic algal biofilm, but otherwise bare from any other benthic sessile colonisers), \u0026lsquo;CCA\u0026rsquo; (crustose coralline algae), and lastly \u0026lsquo;competitors\u0026rsquo;. This category included a range of benthic sessile organisms, including turf algae, macroalgae, sponges, ascidians, bryozoans, tunicates, as well as various bivalve species and worm cases, which were determined to be too difficult to distinguish. In comparison to competitors, which likely inhibit coral settlement and possible survival, we reasoned that bare space and CCA acted instead as coral settlement facilitators.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e3.1.4. Sedimentation\u003c/h2\u003e\u003cp\u003eTo characterise sedimentation rates within the different substrates, \u0026lsquo;turfpods\u0026rsquo; were deployed in each substrate. These turfpods are modified sediment pods, (Field et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Storlazzi et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Turfpods were designed using a 9 cm diameter PVC pipe cut to lengths of 7cm, filled with concrete, and topped with a circle of 3mm long plastic turf grass (modified after (Babcock \u0026amp; Smith, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Latrille et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Stewart et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Four turfpod deployments took place: the first was in September 2022, the second in February 2023, the third in August 2023, and the fourth in September 2023 to increase our sample size and temporal representation. In the 2022 deployment, three turfpods were deployed per substrate at both the Heron Reef and the Wistari Reef substrates. In the 2023 trials, five turfpods were deployed, but only within the two rubble beds at the Heron Reef site (i.e., the loose rubble bed and interlocked rubble bed). Since no new studies of settlement and recruitment (Paewai-Huggins et al., 2025) occurred at Wistari Reef in 2023, no sedimentation measurements were taken at this time. Deployment duration, collection, and lab processing methodologies were the same in each trial.\u003c/p\u003e\u003cp\u003eAfter six days of deployment, the turfpods were carefully collected and placed into plastic bags, taking caution not to disturb any sediment on the pod tops. In the lab, each plastic bag was emptied into a large container, and turfpods were rinsed thoroughly with fresh water to move sediment into the container. The sediment sample was rinsed with fresh water to remove salt before being emptied into a 50 ml Falcon tube. Sediment samples were left to settle, and excess water was poured off; this was repeated twice. Each tube was dried at 60\u0026deg; C for 24 hours and weighed. Data were standardised to grams of sediment accumulated per m\u003csup\u003e2\u003c/sup\u003e per day (Field, 2013).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e3.1.5. Flow\u003c/h2\u003e\u003cp\u003eUsing plaster-of-Paris (UniPro), we made 4cm\u003csup\u003e3\u003c/sup\u003e flow cubes to test water flow differences between the two rubble bed substrates located on Heron Reef, using the dissolution rates of cubes as a proxy for flow (Fox, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). A higher dissolution rate indicated greater exposure to water flow.\u003c/p\u003e\u003cp\u003eThree deployments of cubes took place in February, August, and September 2023. Two treatments were used to determine how the differences in rubble composition between the two rubble beds influenced the flow of water. The 'surface' treatments functioned as a proxy to determine how flow travelling across the two rubble beds varies due to differences in the compositing of either rubble bed substrate. The \u0026lsquo;buried\u0026rsquo; treatment was used to determine if flow can penetrate deeper into the rubble bed, depending on the void spaces between individual rubble pieces.\u003c/p\u003e\u003cp\u003eIn February, a total of 8 cubes were deployed in the rubble beds; four of the flow cubes were placed directly on the surface of the in situ surrounding rubble (\u0026lsquo;surface\u0026rsquo; treatment), and the last four were placed buried within the in-situ rubble (\u0026lsquo;buried\u0026rsquo; treatment). In August and September, replication was increased. In each rubble bed, 12 cubes were deployed. Six cubes were deployed directly on the in-situ rubble (\u0026lsquo;surface\u0026rsquo; treatment), and six were deployed in the in-situ rubble (\u0026lsquo;buried\u0026rsquo; treatment).\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Statistical Analysis\u003c/h2\u003e\u003cp\u003eIn summary, we first compared the absolute levels of coral settlement and recruitment among treatments, both of which involve count data. We then compared the rates of post-settlement mortality, which accounts for the difference between settlement and recruitment. These latter analyses use binomial data (survived or not). To attempt to understand why any differences among treatments occurred, we also compare the community structure of fouling organisms on the rubble over time and attempt to relate this to settlement and recruitment. Similarly, we evaluate patterns of sedimentation among treatments. For each model, backward stepwise model fitting was conducted; non-significant model terms were removed, and the best model was selected using the Akarike Information Criterion (AICc) with package \u0026ldquo;MuMIn\u0026rdquo; (Barton, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Statistical analyses were performed using R Team (RStudio, 2020) for all analyses.\u003c/p\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1. Coral settlement (Three months post-deployment)\u003c/h2\u003e\u003cp\u003eTo analyse the effects of substrate and tile height on coral settlement rates generalized linear mixed-effects models were run using the package \u0026lsquo;glmmTMB\u0026rsquo; (CRAN) for each reef. The response variable was settlement (i.e., the count of coral settlers per rubble piece); the predictor variables were the substrate type (loose rubble vs. interlocked rubble for Heron Reef and interlocked rubble vs. hard carbonate for Wistari Reef), tile height (benthic vs. elevated), and their interaction, and a random effect of tile ID was included to account for multiple rubble pieces per tile. We also analysed settlement in response to the microhabitat of the rubble piece (topside, side, and bottom side) for each rubble piece to determine any settling preference of coral larvae in relation to exposed or sheltered surfaces of the rubble. However, those data are not presented in the main results, as here we were less interested in the location of settlement onto rubble, but rather more interested in the general rate of settlement onto rubble. However, those results are located in the Appendix. A negative binomial distribution was used for the count response, employing a log link function. The surface area of rubble of each piece was also included as an offset to standardise the recruit count to rubble size.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2. Coral recruitment (12 months post-deployment)\u003c/h2\u003e\u003cp\u003eTo analyse the abundance of corals that survived from three months to 12 months, generalised linear mixed-effects models were run using the package \u0026lsquo;glmmTMB\u0026rsquo; for each reef. The response variable was coral recruitment (i.e., the count of settled corals per rubble piece that were still alive 12 months post-deployment). The predictor variables were the substrate type, tile height, and their interaction, and a random effect of tile ID was again included.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.2.3. Post-settlement mortality rate (12 months post-deployment)\u003c/h2\u003e\u003cp\u003eTo determine how the probability of mortality occurring from three months to 12 months differed between substrates and tile heights at each reef, two generalised linear mixed-effects models were run using the package \u0026lsquo;glmmTMB\u0026rsquo;. For both, a binomial error structure was used with a logit link function, as the response variable was binary (i.e., 1 for a coral that had settled at three months and was no longer present at 12 months and 0 for a coral settled at three months and was still present at 12 months); the predictor variables were the substrate type, tile height, and their interaction, and a random effect of tile ID was included.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.2.4. Community structure on rubble and its link to coral settlement and recruitment\u003c/h2\u003e\u003cp\u003eTo determine the overall effect of competitors and facilitators on coral settlement and recruitment rates, a generalised mixed-effects model was run for each reef. The percentage cover of each of the three categories of rubble encrusters, i.e. bare space, CCA, and competitors, was included as explanatory variables. Interactions between each category and substrate were also included, as the effect of each encrusting category might vary with substrate. A Poisson distribution was used for the response variable (count data), employing a log link function. The rubble surface area of each piece was also included as an offset. This analysis was completed on a subset of the rubble pieces (253/1869 pieces), for which we had confidence in the photo quality and identification of the encrusting community. For each reef, a PERMANOVA was conducted to determine whether the community composition (3 categories) of the rubble pieces varied between substrates, tile heights or time of deployment (3 months vs. 12 months), including the explanatory factors. To downweigh the importance of the dominant space occupiers, percentage covers were square-root transformed prior to the construction of a dissimilarity matrix using Bray-Curtis. SIMPER (Similarity Percentage analysis) was then utilised to determine the top contributing categories to significant differences in community composition between levels of the explanatory factors. Community analyses were conducted in PRIMER7 (PRIMER-e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\u003ch2\u003e3.2.5. Sedimentation\u003c/h2\u003e\u003cp\u003eTwo linear mixed-effects models were run. One for the two rubble beds of Heron Reef and one for the two substrates (interlocked rubble and hard carbonate) of Wistari Reef. Based on the structural composition of rubble comprising the interlocked rubble bed, we hypothesised that sediment deposition would be lower compared to the other two substrates. Therefore, we employed a one-tailed test to assess this directional effect with date included as a random effect (for the Heron Reef model) to account for temporal variation (i.e. deployment trials from September 2022 to September 2023). The comparison between the interlocked rubble and hard carbonate at Wistari was left as 2-tailed as we did not have an a \u003cem\u003epriori\u003c/em\u003e hypothesis. The models used the total amount of deposited sediment collected as the response variable and substrate as the predictor variable.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.2.6. Flow\u003c/h2\u003e\u003cp\u003eA linear mixed-effects model was used to assess the rate of dissolution (flow) across combinations of substrate type (loose vs. interlocked rubble bed) and cube treatment (surface vs. buried), with month included as a random effect to account for temporal variation, rate of dissolution as the response variable and substrate and cube treatments as the predictor variables. We again employed a one-tailed test to evaluate our hypotheses: i) flow was greater in the loose rubble compared to the interlocked, therefore surface cubes deployed in the loose bed would have a greater dissolution rate; ii) due to greater void space present in the interlocked bed, buried cubes would have a greater dissolution rate compared to those buried in the densely packed rubble comprising the loose rubble bed; iii) surface cubes in the loose bed would have a greater dissolution rate compared to those buried in the loose rubble; and iv) surface cubes and buried cubes in the interlocked rubble bed would result in comparable rates of dissolution.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003ch2\u003e4.1. Coral settlement and recruitment\u0026nbsp;\u003c/h2\u003e\n\u003ch2\u003e4.1.1. Loose rubble vs. Interlocked rubble (Heron)\u003c/h2\u003e\n\u003cp\u003eSettlement to benthic tiles was higher in the interlocked rubble than in the loose rubble (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e\u0026lt;0.0001). The settlement of corals on control (elevated) tiles did not differ between substrates (\u003cem\u003eP\u003c/em\u003e = 0.07), implying a similar supply of larvae to both substrates. Although the primary purpose of the elevated tiles was to test for differences in larval supply between rubble treatments, it is interesting to compare settlement patterns to those on the benthos. \u0026nbsp;The difference in settlement between elevated and benthic tiles differed between substrates but was always greater on elevated tiles (Figure 2a). Within the loose rubble bed, settlement to benthic tiles was approximately one-quarter that of the elevated tiles (\u003cem\u003eP\u003c/em\u003e \u0026lt;0.0001) (Figure 2a). In the interlocked rubble, settlement on benthic tiles comprised less than half the level observed on elevated tiles in the same substrate (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001) (Figure 2a).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMortality was high, \u0026gt;90% across all substrates and tile height treatments over the 9 months (Figure 3b).\u0026nbsp;Though the probability of mortality on benthic tiles between the two rubble substrates was comparable (Figure 2b), the number of coral recruits was still marginally greater on benthic tiles within the interlocked rubble compared to the loose rubble (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.05, Figure 2c). For elevated tiles, the probability of mortality was higher in interlocked rubble than loose rubble (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.006, Figure 2b), but the number of coral recruits remained comparable on the elevated tiles across the two rubble beds (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.06, Figure 2c).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4.1.2. Interlocked rubble vs Hard carbonate-(Wistari)\u003c/h2\u003e\n\u003cp\u003eSettlement within the interlocked rubble and hard carbonate substrates of Wistari was once again higher in the more stable substrate. There was 1 more settler per rubble piece on tiles within the hard carbonate than in the interlocked rubble (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.008, Figure 3a). Like Heron, the settlement of corals on control (elevated) tiles was similar between substrates (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.8, Figure 3a), suggesting similar larval supply rates, and coral settlement was greater on elevated than benthic tiles in both substrates (interlocked: \u003cem\u003eP\u003c/em\u003e \u0026lt;.0001; hard carbonate \u003cem\u003eP\u0026nbsp;\u003c/em\u003e=\u003cem\u003e\u0026nbsp;\u003c/em\u003e0.02, Figure 3a).\u003c/p\u003e\n\u003cp\u003eLike Heron, mortality rates were high (\u0026gt;90%) across tile heights and substrates (Figure 3b). Unlike Heron, where recruitment on benthic tiles was higher in the more stable substrate, coral recruitment was similar on benthic tiles between interlocked rubble and hard carbonate (Figure 3c).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4.3. Community structure on rubble concerning coral settlement and recruitment\u003c/h2\u003e\n\u003cp\u003eThe relationship between coral settlement and the cover of either CCA or bare space varied among habitat types (\u003cem\u003eP\u003c/em\u003e = 0.03) and (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.001), respectively (Figure 4a\u0026amp;b). Coral settlement was weakly associated with CCA in the interlocked rubble bed and hard carbonate (Figure 4a). However, settlement increased strongly in the loose rubble bed as the coverage of CCA increased (Figure 4a). Positive associations between settlement and bare space were found in the loose rubble bed and hard carbonate (Figure 4b), but settlement declined with greater bare space in the interlocked rubble substrate.\u003c/p\u003e\n\u003cp\u003eAcross all substrates, tile heights, and periods of deployment, space on rubble pieces was dominated by coral competitors (Figures 5 and 6). Bare space (with biofilms) was the biggest contributing factor to the difference in the rubble-encrusting community between benthic and elevated tiles at three months post-deployment in each of the substrates (Tables 1 and 2). Availability of bare space at three months was more prevalent on benthic tiles compared to elevated tiles, regardless of substrate (Tables 1 and 2). At 12 months post-deployment, crustose coralline algae (CCA) colonisation was the main factor differentiating rubble-encrusting communities on benthic and elevated tiles in all substrates except in the loose rubble bed.\u003c/p\u003e\n\u003ch2\u003e4.3.1. Loose rubble vs. Interlocked rubble (Heron)\u003c/h2\u003e\n\u003cp\u003eAt the three-month timepoint, communities were similar between benthic and elevated tiles in the loose rubble bed (Table 1). In the loose rubble bed, the main contributor to the difference in the community on benthic tiles over time (\u003cem\u003eP\u003c/em\u003e(\u003cem\u003eperm\u003c/em\u003e) = 0.03) was CCA (Contributions = 47% and the cover of CCA on these tiles increased from three to 12 months (Table 1). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCommunity composition in the interlocked rubble bed differed between benthic and elevated tiles at both time points (three months, \u003cem\u003eP(perm)\u0026nbsp;\u003c/em\u003e= 0.001), 12 months \u003cem\u003e(P(perm)\u003c/em\u003e = 0.043, Table S1). At 3 months, bare space (contribution = 50%) was the primary contributor to differences in the encrusting community and had higher coverage on benthic tiles (Table 1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 1. Pair-wise test analysis of the difference in the composition of the rubble encrusting community per rubble piece as a response to the 3-way interaction of (rubble substrate x tile height x time of deployment) concerning each variable individually in the loose and interlocked rubble bed of Heron Reef. Where a significant difference in the encrusting community occurs between the interaction and specific variable is denoted with an asterisk (*) and in bold under the \u003cem\u003eP-value\u0026nbsp;\u003c/em\u003ecolumn. The column furthest to the right includes results from the SIMPER analysis for each Pair-wise significant interaction. Given from top to bottom in this column is the rubble encrusting category that drove the difference in the composition of the community, the tile height, time of deployment, or substrate habitat where the greater average abundance of said rubble encrusting category occurred and the contribution of said rubble encrusting category driving the difference in the composition.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 601px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePAIR-WISE TEST\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 601px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Tile height\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTIME OF DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Loose rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Benthic Vs. \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Elevated tiles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; 0.166\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp;Benthic Vs. Elevated tiles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; 3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Bare space\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Higher on: Benthic tiles\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 50.7%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 601px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Time period\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTIME OF DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Loose rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months Vs. 12 months\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;0.031*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u0026nbsp;CCA \u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Higher at: 3 months\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 47.4%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months Vs. 12 months\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003eBare space\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Higher at: 3 months\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 42%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 601px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Habitat\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTIME OF DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003eLoose\u003c/p\u003e\n \u003cp\u003eVs.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; 0.509\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003eLoose\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eVs.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;12 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003eCCA\u003c/p\u003e\n \u003cp\u003eHigher in: Loose rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 39.6%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003eLoose\u003c/p\u003e\n \u003cp\u003eVs.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 122px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Elevated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 138px;\"\u003e\n \u003cp\u003eCCA\u003c/p\u003e\n \u003cp\u003eHigher in: Loose rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 38.6%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eAt three months, there was no difference in the rubble encrusting community on benthic tiles between rubble substrates. At 12 months, the difference in the community on benthic tiles between the loose and interlocked rubble beds was significant \u003cem\u003e(P(perm)\u003c/em\u003e = 0.001) (Table 1). CCA colonisation was the largest contributor (contribution = 39%) to this difference, with a higher cover of CCA on benthic tiles in the loose rubble bed than in the interlocked rubble bed (Table 1). In contrast, at three months, the difference in encrusting communities on elevated tiles between the two rubble substrates was significant (\u003cem\u003eP\u003c/em\u003e(\u003cem\u003eperm)\u0026nbsp;\u003c/em\u003e= 0.001) (Table 1), but not at 12 months (Table S1).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4.3.2. Interlocked rubble vs. Hard carbonate (Wistari)\u003c/h2\u003e\n\u003cp\u003ePERMANOVA and pair-wise tests analysis showed significant differences in the rubble-encrusting communities on benthic and elevated tiles in both the interlocked rubble bed and hard carbonate reef at three- and 12-month post-deployment, except for within the hard carbonate reef at three months. At three months, the encruster communities differed significantly between benthic and elevated tiles in both substrates \u003cem\u003e(P(perm)\u003c/em\u003e = 0.004 within interlocked rubble and (\u003cem\u003eP(perm)\u0026nbsp;\u003c/em\u003e= 0.001 within hard carbonate reef) (Table 2). The main factor driving these differences was the abundance of bare space, which was more abundant on benthic tiles in either substrate (46.4% contribution in interlocked rubble and 47% in hard carbonate) (Table 2). By twelve months, the community difference in the hard carbonate reef persisted \u003cem\u003e(P(perm)\u0026nbsp;\u003c/em\u003e= 0.002) (Table 2), with the primary factor being the colonisation of coralline algae (CCA), which was more abundant on benthic tiles (contribution = 40%) (Table 2).\u003c/p\u003e\n\u003cp\u003eApart from benthic tiles in the hard carbonated reef, the timing of tile deployment significantly affected the rubble-encrusting communities on different tile heights in each substrate. In the interlocked rubble bed, the community composition on benthic tiles differed significantly between three and 12 months (\u003cem\u003eP(perm) =\u003c/em\u003e 0.03) (Table 2), with the colonisation of CCA as the main contributor (contribution = 41%), the abundance was greater at 12 months than at three months post-deployment (Table 2). For the elevated tiles in both substrates, the communities also differed significantly between three and 12 months \u003cem\u003e(P(perm)\u0026nbsp;\u003c/em\u003e= 0.004) within interlocked rubble and (\u003cem\u003eP(perm)\u0026nbsp;\u003c/em\u003e= 0.002) within hard carbonate reef) (Table 2), with bare space as the leading contributor (37% and 40%, respectively) (Table 2). Bare space was more abundant at 12 months compared to three months for the elevated tiles in both substrates.\u003c/p\u003e\n\u003cp\u003eTable 4. Pair-wise test analysis of the difference in the composition of the rubble encrusting community per rubble piece as a response to the 3-way interaction of (rubble substrate x tile height x time of deployment) concerning each variable individually in the interlocked rubble bed and hard carbonate reef of Wistari Reef. Where a significant difference in the encrusting community occurs between the interaction and specific variable is denoted with an asterisk (*) and in bold under the \u003cem\u003eP-value\u0026nbsp;\u003c/em\u003ecolumn. The column furthest to the right includes results from the SIMPER analysis for each Pair-wise significant interaction. Given from top to bottom in this column is the rubble encrusting category that drove the difference in the composition of the community, the tile height, time of deployment, or substrate habitat where the greater average abundance of said rubble encrusting category occurred and the contribution of said rubble encrusting category driving the difference in the composition.\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"614\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 614px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePAIR-WISE TEST\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 614px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Tile height\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTIME OF DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Benthic Vs.\u003c/p\u003e\n \u003cp\u003eElevated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;3 months post- \u0026nbsp; \u0026nbsp;deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;0.004*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eBare space\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Higher on: Benthic tiles\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Contribution: 46.4%\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Hard carbonate reef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Benthic Vs.\u003c/p\u003e\n \u003cp\u003eElevated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;0.001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eBare space\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Higher on: Benthic tiles\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Contribution: 47.8%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 614px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Time period\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp;TIME OF \u0026nbsp; DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble bed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 3 months Vs. 12 months\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.033*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eCCA\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Higher at: 3 months\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 41.9%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Hard carbonate reef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months Vs. 12 months\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" valign=\"top\" style=\"width: 614px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 WAY INTERACTION x Habitat\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHABITAT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;TILE HEIGHT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTIME OF DEPLOYMENT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;P-VALUE\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSIMPER\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Interlocked rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Vs.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Hard carbonate reef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Interlocked rubble Vs.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Hard carbonate reef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Benthic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;12 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; 0.017*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eCCA\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Higher in: Interlocked rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 43.2%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eInterlocked rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Vs.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Hard carbonate reef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Elevated\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 131px;\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;3 months post-deployment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 80px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; 0.04*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eCCA\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; Higher in: \u0026nbsp; \u0026nbsp;Interlocked rubble\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;Contribution: 40.5%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn both the interlocked rubble bed and hard carbonate reef the rubble encrusting communities were significantly different between three- and 12 months post-deployment (\u003cem\u003eP(perm) =\u0026nbsp;\u003c/em\u003e0.004) and (\u003cem\u003eP(perm) =\u0026nbsp;\u003c/em\u003e0.002), respectively (Table 2), and bare space in both habitats was the leading contributor (contribution = 37%) and (contribution = 40%), respectively (Table 2). Bare space was more abundant at 12 months post-deployment than three for the elevated tiles in each substrate.\u003c/p\u003e\n\u003cp\u003eFrom the PERMANOVA and pair-wise test analysis, substrate appeared to have a significant impact on the difference in the rubble encrusting communities on the tiles across each substrate at both three- and 12-months post-deployment except for the benthic tiles at three months (Table 2). However, as time progressed the difference in the rubble-encrusting communities on the benthic tiles in either substrate did become more variable. The rubble-encrusting community composition on benthic tiles across the interlocked rubble bed and hard carbonate reef significantly differed at 12 months post-deployment (\u003cem\u003eP(perm) =\u0026nbsp;\u003c/em\u003e0.017) (Table 2). \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4.4. Sedimentation\u003c/h2\u003e\n\u003cp\u003eThe linear mixed-effects model regarding the rubble beds of Heron Reef indicated that deposited sediment was greater in the loose rubble bed (mean = 8.13 g m\u0026sup2; d⁻\u0026sup1;) compared to the interlocked rubble bed (mean = 7 g m\u0026sup2; d⁻\u0026sup1;) (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.04) (Figure 7). The fixed effect estimate for the interlocked rubble bed was -1.16, indicating a decrease in sediment deposition relative to the loose bed. This supports our expectation that the interlocked rubble bed captures less sediment than the loose rubble bed.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn contrast, sediment deposition did not differ significantly between the interlocked rubble and hard carbonate reef of Wistari (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.75) (Figure 7). The model estimated a mean sediment value of 11.2 g m\u0026sup2; d⁻\u0026sup1; collected on turfpods in the interlocked rubble bed and a mean of 13.2 in the hard carbonate, which was indistinguishable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4.5. Flow\u003c/h2\u003e\n\u003cp\u003eThe flow results did not support our initial hypothesis that flow would be greater in the loose rubble bed compared to the interlocked bed. As the mean dissolution of surface cubes in either bed was comparable (2.5 g in loose rubble and 2.4 g in interlocked rubble bed) (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.07) (Figure 8). Furthermore, the dissolution between buried cubes in either rubble bed was also comparable (2.2 g in loose rubble and 2.3 g in interlocked rubble bed) (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.4) (Figure 8).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHowever, our hypothesis concerning the difference in flow exposure between surface cubes and buried cubes in the loose rubble bed was supported by our results. On average, the dissolution of surface cubes (2.5 g) was greater than that of the buried cubes (2.2 g) in the loose rubble bed (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e\u0026lt; 0.001) (Figure 8). Furthermore, our hypothesis that surface and buried cubes in the interlocked rubble bed would experience similar flow exposure was also supported by flow results. The average dissolution of surface cubes (2.4 g) was similar to that of the buried cubes (2.3 g) in the interlocked bed (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e= 0.07) (Figure 8).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe examined how the environment associated with different substrates \u0026ndash; loose rubble, interlocked rubble and hard carbonate - influences coral settlement and recruitment on the southern Great Barrier Reef (GBR). We find a distinct environmental effect associated with these substrates, particularly at the settlement stage at both Heron and Wistari Reefs; substrates of greater stability and complexity have higher settlement. Since the direct effects of rubble mobility were excluded by the experimental design, our results imply that the environments associated with reef and rubble substrates are sufficiently different to impacts of coral settlement and recruitment. Specifically, settlement was lower in the loose rubble than in the interlocked rubble of Heron Reef, and lower in the interlocked rubble than the hard carbonate of Wistari Reef. These patterns occur despite tiles in more stable substrates having equal or a higher cover of competing taxa encrusting the rubble. While there was high mortality at the post-settlement stage, coral recruitment remained higher on interlocked than loose rubble, suggesting that the interlocked rubble bed is more favourable. But recruitment to even more stable \u0026ndash; hard carbonate- substrate appeared to offer no further benefit, as there was no difference in recruitment between interlocked and hard carbonate substrates at Wistari Reef. We conclude that the effects of loose and interlocked rubble beds on coral recruitment are not limited to rubble mobility and highlight that these effects are less pronounced for more stable interlocked beds.\u003c/p\u003e\u003cp\u003eSimilar settlement rates on elevated tiles in each substrate suggest that larval supply is comparable across substrates at both Heron and Wistari Reefs. This is important for our experimental inference. The lack of significant difference across elevated tile treatments, despite there being far higher settlement than on benthic tiles means that inferences on rubble habitats could be drawn directly from the settlement rates to benthic tiles. Settlement rates were higher on elevated tiles than benthic tiles regardless of substrate type, indicating that effects on settlement are greater at the substrate level and that rubble beds are unlikely to be recruitment-limited.\u003c/p\u003e\u003cp\u003eThe structural complexity of a rubble bed or hard carbonate reef is determined by rubble size, morphology, configuration, the reef rock structure, and coral cover. Reefs with low structural complexity have reduced turbulence in the boundary layer at the substrate level, while healthy, structurally complex reefs can have high drag coefficients and heightened turbulence and mixing water flow (Guihen et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). These hydrodynamic variations can have various flow-on effects that further impact the success of coral settlement, such as: inhibiting a coral larva\u0026rsquo;s ability to access the substratum (Hata et al., 2017), influencing sediment retention (Jones et al., 2015; Moeller et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and affect access to nutrients of settled corals and other sessile marine organisms, impacting their growth and survival (Kenyon et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe loose rubble bed has reduced structural complexity compared to the interlocked beds and hard carbonate reef due to differences in the rubble size, morphology, configuration, and the paucity of adult coral colony abundancies (Paewai-Huggins, \u003cem\u003epers. obvs.\u003c/em\u003e). There may thus be a higher free-stream flow of water travelling across the low-rugosity, loose bed, but lower turbulence (Kenyon et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), leading to lower retention of coral larvae closer to the substrate (Sebens et al., 1998), ultimately reducing settlement. Dissolution measurements indicate that the loose rubble bed was at least occasionally exposed to higher flow conditions than those in the interlocked bed. Our results suggest that flow within the loose bed has the potential to exceed that of the interlocked bed, likely driven by differences in the configuration between rubble beds. Future studies would benefit from investigating flow differences at the time of spawning and settlement to better identify how flow influences larval settlement between rubble beds of varying configuration and complexity.\u003c/p\u003e\u003cp\u003eSedimentation can inhibit coral settlement or smother already settled corals, inhibiting post-settlement survival and growth (Babcock \u0026amp; Davies, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Humanes et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Moeller et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ama Wakwella et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and is likely to differ between rubble bed types. The size and configuration of rubble pieces in beds create variation in void space (i.e., the size variation in the gaps between pieces) (Kenyon et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Compared to the densely packed pieces in the loose bed, the larger void spaces in the interlocked beds may enable sediment to fall between rubble and away from settlers on the benthic tiles. Trapped deep in the interlocked matrix, less sediment would be resuspended here compared to the loose rubble bed. Coral settlement on rubble in loose rubble may be more exposed to deposited sediment on the topsides and the resuspension of sediment on the undersides, resulting in lower settlement and increased mortality. Our sedimentation results support this hypothesis, that the composition of the rubble comprising the loose bed makes sediment retention a more prominent concern for this type of rubble bed, likely negatively impacting coral settlement.\u003c/p\u003e\u003cp\u003eIn addition to sedimentation, the reduced turbulence and water flow around loose rubble compared to interlocked rubble might restrict particle capture and the mass transfer of nutrients reaching settlers. Flow is essential for coral metabolism (Blanchon et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Nakamura et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Wolfe et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and provides planktonic food for heterotrophic feeding (Borell et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Benthic tiles were positioned to be flush with the surrounding rubble. However, in the interlocked rubble bed, the larger void spaces allowed greater flow between rubble pieces and between the tile and the benthos, while the densely packed loose bed offered little space below the tiles. While our results don\u0026rsquo;t represent a strong difference in flow experienced by buried cubes between the two rubble beds, there is evidence to support that flow exposure was different for surface and buried cubes in the loose bed. Surface cubes experienced a significant increase in flow compared to those buried within the in-situ rubble. Suggesting the densely packed nature of the rubble may have prevented oxygen and nutrient-rich waters from passing across the underside of tiles, stunting the growth and survival of settled corals within the loose rubble bed, and leading to a higher probability of mortality and lower recruitment. In contrast, flow was comparable between buried and surface cubes in the interlocked rubble bed. Suggesting that the substrate configuration may improve flow penetration, delivering oxygen and nutrients to a larger surface area of the rubble, including the undersides of tiles, which may support increased survival and recruitment.\u003c/p\u003e\u003cp\u003eIn addition to flow, sedimentation, and nutrient transfer, competition with other sessile organisms can negatively impact coral settler growth and survival (Chong-Seng et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Doropoulos et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gouezo et al., 2020). Ascidians and bryozoans are major rubble-dwelling taxa (Wolfe et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), taking advantage of the cryptic substrate provided by rubble (Wolfe et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and have the potential to outcompete coral larvae for space, inhibiting settlement or increasing rates of mortality (Doropoulos et al., 2015). However, the composition of the rubble encrusting community appeared to have little influence on coral settlement and coral recruitment across all substrates. Thus, while rates of settlement and recruitment varied among treatments, rubble was always dominated by competitors, including ascidians, bryozoans, and sponges. Furthermore, settlement was always greater on elevated tiles, yet these consistently had less available settlement space (bare space). It appears that the role of competition is highly context dependent. For example, a Caribbean study found higher mortality of coral settlers with an increase in sessile invertebrate coverage (Arnold and Steneck, 2011), whereas a study in Palau found that competition from other benthic organisms tends to be less important than avoiding areas of high corallivory (Doropoulos et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWhile mortality rates were similar between rubble beds (\u0026gt;\u0026thinsp;95%), settlement was still greater in the interlocked rubble compared to the loose rubble bed. Similarities among the mortality rates of corals across the two rubble beds suggest that the bottleneck to coral growth and survival in loose rubble occurs earlier, in the first three months. Though previous studies in rubble beds have also pointed to bottlenecks occurring in the early life stages (Cameron et al, 2016; Chong-Seng et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), causation was linked to high rubble mobility. However, in the present study, lower settlement and higher post-settlement mortality were still observed on rubble pieces despite the stable nature of the tiles. Stability is indeed important (Paewai-Huggins et al., 2025), but we reveal here that environmental effects also occur. The rubble configuration within the loose bed appears to pose challenges for larvae reaching and/or surviving on the tiles, through restricted turbulence, increased sediment retention, and/or limited nutrient transfer and anoxia. These factors likely contribute to significant setbacks in the early stages of settlement. Furthermore, they appear to disproportionately affect smaller, newly settled corals rather than later-stage recruits, as evidenced by the comparable survival rates between loose and interlocked beds for larger corals (between 3 and 12 months). These early-stage bottlenecks are likely to lead to lower coral cover in loose beds over time. Indeed, there were fewer larger coral colonies in the loose rubble bed.\u003c/p\u003e\u003cp\u003eInterpreting coral recruitment rates between the interlocked rubble bed and the hard carbonate of Wistari is less straightforward. Though coral settlement was lower in the interlocked rubble than in the hard carbonate, coral recruitment was comparable after 12 months. Considering that sediment and the rubble encrusting community compositions were similar between substrates, greater settler abundance on benthic tiles in the hard carbonate than the interlocked bed may be related to a difference in the abundance of macroalgal cover on the \u003cem\u003ein-situ\u003c/em\u003e rubble comprising the interlocked bed (Paewai-Huggins, \u003cem\u003epers. obs.)\u003c/em\u003e. Macroalgae can have several inhibiting mechanisms that negatively affect coral settler growth and survival (Chong-Seng et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), including via abrasion (Box \u0026amp; Mumby, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), reduced oxygen exchange (Finelli et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2006\u003c/span\u003e), and shading, which impacts the photosynthetic processes of zooxanthellae (Box \u0026amp; Mumby, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Mundy \u0026amp; Babcock, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Settling coral larvae have been shown to move away from local patches of brown macroalga \u003cem\u003eLobophora spp.\u003c/em\u003e (Evensen et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and in some cases fail to settle on an entire ref when dominated by algae (Doropoulos et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eRubble mobility is the leading theory explaining low rates of survival and growth of corals in rubble beds. We do not attempt to challenge that notion, and indeed find evidence of important mobility effects (Paewai-Huggins et al., 2025). However, we also find that settlement bottlenecks appear to exist regardless of whether the rubble is stable. Thus, the surrounding rubble environment has important impacts on coral recruitment. The drivers of such recruitment failure are clearly influenced by the typology of rubble, and likely involve factors associated with flow and sedimentation. Yet understanding of these mechanisms remains in its infancy. Our results do, however, have implications for the likely success of restoration. Rubble stabilisation is a widely used approach to facilitate coral recovery (Ceccarelli et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). While promoting stability is indeed important, we also find that merely stabilising rubble will not guarantee success in rubble beds whose environment remains hostile to coral settlement and survival (e.g., where the rubble comprises small, loose pieces). Rubble characteristics beyond mobility should be considered when contemplating the utility of restoration methods for coral recovery. A standardised methodology for categorising rubble now exists (Kenyon et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and its usage will help researchers synthesise outcomes clearly. Our study is far from globally representative, but it points to a wider issue that can be built on by the great diversity of restoration practitioners. Indeed, much can be learnt if practitioners take and report field measurements of flow and sedimentation to help interpret the outcomes of their interventions and collectively obtain a holistic understanding of the drivers of coral recruitment on rubble.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eP. M. assisted in the conception, experimental design, analysis and interpretation. P.M. was also involved in the revisions and assisted in data collection.T. K. assisted in the conception, design, analysis and interpretation. T.K. was also involved in the revisions and assisted in data collection. R.P.H. lead experimental design, deployment, data collection, analysis and interpretation. R.P.H. also wrote the main manuscript text and prepared figures 1-8.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe'd firstly like to acknowledge the Gooreng Gooreng, Gurang, Bailai and Taribelang Bunda peoples in the sea country of the Southern Great Barrier Reef, where this fieldwork took place. We'd like to also acknowledge the staff and team of the Heron Island Research center for their support and assistance in the field and laboratory.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data analysis files and corresponding datasets have been deposited in GitHub: https://github.com/Roima25/FirstPaper_Data\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBabcock, R., \u0026amp; Davies, P. (1991). Effects of sedimentation on settlement of Acropora millepora. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 9\u003c/em\u003e, 205-208. \u003c/li\u003e\n\u003cli\u003eBabcock, R., \u0026amp; Smith, L. (2002). Effects of sedimentation on coral settlement and survivorship. Proceedings of the Ninth International Coral Reef Symposium, Bali, 23-27 October 2000, \u003c/li\u003e\n\u003cli\u003eBarton, K. (2009). MuMIn: multi-model inference. \u003cem\u003ehttp://r-forge\u003c/em\u003e\u003cem\u003e. r-project. org/projects/mumin/\u003c/em\u003e.\u003c/li\u003e\n\u003cli\u003eBlanchon, P., Jones, B., \u0026amp; Kalbfleisch, W. (1997). Anatomy of a fringing reef around Grand Cayman; storm rubble, not coral framework. \u003cem\u003eJournal of Sedimentary Research\u003c/em\u003e,\u003cem\u003e 67\u003c/em\u003e(1), 1-16. \u003c/li\u003e\n\u003cli\u003eBorell, E. M., Yuliantri, A. R., Bischof, K., \u0026amp; Richter, C. (2008). The effect of heterotrophy on photosynthesis and tissue composition of two scleractinian corals under elevated temperature. \u003cem\u003eJournal of Experimental Marine Biology and Ecology\u003c/em\u003e,\u003cem\u003e 364\u003c/em\u003e(2), 116-123. \u003c/li\u003e\n\u003cli\u003eBox, S. J., \u0026amp; Mumby, P. J. (2007). Effect of macroalgal competition on growth and survival of juvenile Caribbean corals. \u003cem\u003eMarine Ecology Progress Series\u003c/em\u003e,\u003cem\u003e 342\u003c/em\u003e, 139-149. \u003c/li\u003e\n\u003cli\u003eCeccarelli, D. M., McLeod, I. M., Bostr\u0026ouml;m-Einarsson, L., Bryan, S. E., Chartrand, K. M., Emslie, M. J., Gibbs, M. T., Gonzalez Rivero, M., Hein, M. Y., \u0026amp; Heyward, A. (2020). Substrate stabilisation and small structures in coral restoration: State of knowledge, and considerations for management and implementation. \u003cem\u003ePlos one\u003c/em\u003e,\u003cem\u003e 15\u003c/em\u003e(10), e0240846. \u003c/li\u003e\n\u003cli\u003eChong-Seng, K. M., Graham, N. A. J., \u0026amp; Pratchett, M. S. (2014). Bottlenecks to coral recovery in the Seychelles. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 33\u003c/em\u003e(2), 449-461. https://doi.org/10.1007/s00338-014-1137-2 \u003c/li\u003e\n\u003cli\u003eConnell, J. H., Hughes, T. P., \u0026amp; Wallace, C. C. (1997). A 30‐year study of coral abundance, recruitment, and disturbance at several scales in space and time. \u003cem\u003eEcological monographs\u003c/em\u003e,\u003cem\u003e 67\u003c/em\u003e(4), 461-488. \u003c/li\u003e\n\u003cli\u003eDollar, S. J., \u0026amp; Tribble, G. W. (1993). Recurrent Storm Disturbance and Recovery - a Long-Term Study of Coral Communities in Hawaii. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 12\u003c/em\u003e(3-4), 223-233. https://doi.org/Doi 10.1007/Bf00334481 \u003c/li\u003e\n\u003cli\u003eDoropoulos, C., Roff, G., Bozec, Y. M., Zupan, M., Werminghausen, J., \u0026amp; Mumby, P. J. (2016). Characterizing the ecological trade-offs throughout the early ontogeny of coral recruitment. \u003cem\u003eEcological monographs\u003c/em\u003e,\u003cem\u003e 86\u003c/em\u003e(1), 20-44. https://doi.org/10.1890/15-0668.1 \u003c/li\u003e\n\u003cli\u003eDoropoulos, C., Roff, G., Zupan, M., Nestor, V., Isechal, A. L., \u0026amp; Mumby, P. J. (2014). Reef-scale failure of coral settlement following typhoon disturbance and macroalgal bloom in Palau, Western Pacific. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 33\u003c/em\u003e(3), 613-623. \u003c/li\u003e\n\u003cli\u003eEvensen, N. R., Doropoulos, C., Morrow, K. M., Motti, C. A., \u0026amp; Mumby, P. J. (2019). Inhibition of coral settlement at multiple spatial scales by a pervasive algal competitor. \u003cem\u003eMarine Ecology Progress Series\u003c/em\u003e,\u003cem\u003e 612\u003c/em\u003e, 29-42. \u003c/li\u003e\n\u003cli\u003eField, M. E., Chezar, H., \u0026amp; Storlazzi, C. D. (2013). SedPods: a low-cost coral proxy for measuring net sedimentation. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 32\u003c/em\u003e(1), 155-159. https://doi.org/10.1007/s00338-012-0953-5 \u003c/li\u003e\n\u003cli\u003eFinelli, C. M., Helmuth, B. S., Pentcheff, N. D., \u0026amp; Wethey, D. S. (2006). Water flow influences oxygen transport and photosynthetic efficiency in corals. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 25\u003c/em\u003e, 47-57. \u003c/li\u003e\n\u003cli\u003eFox, H. E. (2004). Coral recruitment in blasted and unblasted sites in Indonesia: assessing rehabilitation potential. \u003cem\u003eMarine Ecology Progress Series\u003c/em\u003e,\u003cem\u003e 269\u003c/em\u003e, 131-139. https://doi.org/DOI 10.3354/meps269131 \u003c/li\u003e\n\u003cli\u003eFox, H. E., \u0026amp; Caldwell, R. L. (2006). Recovery from blast fishing on coral reefs: A tale of two scales. \u003cem\u003eEcological Applications\u003c/em\u003e,\u003cem\u003e 16\u003c/em\u003e(5), 1631-1635. https://doi.org/Doi 10.1890/1051-0761(2006)016[1631:Rfbfoc]2.0.Co;2 \u003c/li\u003e\n\u003cli\u003eFox, H. E., Pet, J. S., Dahuri, R., \u0026amp; Caldwell, R. L. (2003). Recovery in rubble fields: long-term impacts of blast fishing. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e,\u003cem\u003e 46\u003c/em\u003e(8), 1024-1031. https://doi.org/10.1016/S0025-326x(03)00246-7 \u003c/li\u003e\n\u003cli\u003eGoogle Earth. (2021). Heron Island Reef. Heron Island - Bing Maps\u003c/li\u003e\n\u003cli\u003eGuihen, D., White, M., \u0026amp; Lund\u0026auml;lv, T. (2013). Boundary layer flow dynamics at a cold-water coral reef. \u003cem\u003eJournal of sea research\u003c/em\u003e,\u003cem\u003e 78\u003c/em\u003e, 36-44. \u003c/li\u003e\n\u003cli\u003eHarrington, L., Fabricius, K., De\u0026apos;Ath, G., \u0026amp; Negri, A. (2004). Recognition and selection of settlement substrata determine post-settlement survival in corals. \u003cem\u003eEcology\u003c/em\u003e,\u003cem\u003e 85\u003c/em\u003e(12), 3428-3437. https://doi.org/Doi 10.1890/04-0298 \u003c/li\u003e\n\u003cli\u003eHeyward, A., \u0026amp; Negri, A. (1999). Natural inducers for coral larval metamorphosis. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 18\u003c/em\u003e(3), 273-279. \u003c/li\u003e\n\u003cli\u003eHumanes, A., Fink, A., Willis, B. L., Fabricius, K. E., de Beer, D., \u0026amp; Negri, A. P. (2017). Effects of suspended sediments and nutrient enrichment on juvenile corals. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e,\u003cem\u003e 125\u003c/em\u003e(1-2), 166-175. \u003c/li\u003e\n\u003cli\u003eKenyon, T. M., Doropoulos, C., Dove, S., Webb, G. E., Newman, S. P., Sim, C. W., Arzan, M., \u0026amp; Mumby, P. J. (2020). The effects of rubble mobilisation on coral fragment survival, partial mortality and growth. \u003cem\u003eJournal of Experimental Marine Biology and Ecology\u003c/em\u003e,\u003cem\u003e 533\u003c/em\u003e, 151467. \u003c/li\u003e\n\u003cli\u003eKenyon, T. M., Doropoulos, C., Wolfe, K., Webb, G. E., Dove, S., Harris, D., \u0026amp; Mumby, P. J. (2023). Coral rubble dynamics in the Anthropocene and implications for reef recovery. \u003cem\u003eLimnology and Oceanography\u003c/em\u003e,\u003cem\u003e 68\u003c/em\u003e(1), 110-147. \u003c/li\u003e\n\u003cli\u003eKenyon, T. M., Eigeland, K., Wolfe, K., Paewai‐Huggins, R., Rowell, D., Dodgen, T., \u0026amp; Mumby, P. J. (2024). Material Legacies on Coral Reefs: Rubble Length and Bed Thickness Are Key Drivers of Rubble Bed Recovery. \u003cem\u003eGlobal change biology\u003c/em\u003e,\u003cem\u003e 30\u003c/em\u003e(11), e17574. \u003c/li\u003e\n\u003cli\u003eLatrille, F. X., Tebbett, S. B., \u0026amp; Bellwood, D. R. (2019). Quantifying sediment dynamics on an inshore coral reef: putting algal turfs in perspective. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e,\u003cem\u003e 141\u003c/em\u003e, 404-415. \u003c/li\u003e\n\u003cli\u003eLee, C. S., Walford, J., \u0026amp; Goh, B. P. L. (2009). Adding coral rubble to substrata enhances settlement of Pocillopora damicornis larvae. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 28\u003c/em\u003e(2), 529-533. https://doi.org/10.1007/s00338-009-0467-y \u003c/li\u003e\n\u003cli\u003eMoeller, M., Nietzer, S., Schils, T., \u0026amp; Schupp, P. J. (2017). Low sediment loads affect survival of coral recruits: the first weeks are crucial. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 36\u003c/em\u003e, 39-49. \u003c/li\u003e\n\u003cli\u003eMundy, C., \u0026amp; Babcock, R. (1998). Role of light intensity and spectral quality in coral settlement: implications for depth-dependent settlement? \u003cem\u003eJournal of Experimental Marine Biology and Ecology\u003c/em\u003e,\u003cem\u003e 223\u003c/em\u003e(2), 235-255. \u003c/li\u003e\n\u003cli\u003eMundy, C. N. (2000). An appraisal of methods used in coral recruitment studies. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 19\u003c/em\u003e(2), 124-131. https://doi.org/DOI 10.1007/s003380000081 \u003c/li\u003e\n\u003cli\u003eNakamura, Y., Shibuno, T., Lecchini, D., Kawamura, T., \u0026amp; Watanabe, Y. (2009). Spatial variability in habitat associations of pre-and post-settlement stages of coral reef fishes at Ishigaki Island, Japan. \u003cem\u003eMarine Biology\u003c/em\u003e,\u003cem\u003e 156\u003c/em\u003e, 2413-2419. \u003c/li\u003e\n\u003cli\u003ePaewai-Huggins, R., Kenyon, T.M., \u0026amp; Mumby, P.J., (2025b). The effect of rubble stability on coral settlement and recruitment. \u003cem\u003ePre-print, Research Sqaure, \u003c/em\u003e\u003cem\u003e10.21203/rs.3.rs-7974089/v1\u003c/em\u003e\u003c/li\u003e\n\u003cli\u003eRasser, M. W., \u0026amp; Riegl, B. (2002). Holocene coral reef rubble and its binding agents. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 21\u003c/em\u003e(1), 57-72. https://doi.org/10.1007/s00338-001-0206-5 \u003c/li\u003e\n\u003cli\u003eRaymundo, L., Maypa, A., Gomez, E., \u0026amp; Cadiz, P. (2007). Can dynamite-blasted reefs recover? A novel, low-tech approach to stimulating natural recovery in fish and coral populations. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e,\u003cem\u003e 54\u003c/em\u003e(7), 1009-1019. \u003c/li\u003e\n\u003cli\u003eRoth, F., Saalmann, F., Thomson, T., Coker, D. J., Villalobos, R., Jones, B., Wild, C., \u0026amp; Carvalho, S. (2018). Coral reef degradation affects the potential for reef recovery after disturbance. \u003cem\u003eMarine Environmental Research\u003c/em\u003e,\u003cem\u003e 142\u003c/em\u003e, 48-58. \u003c/li\u003e\n\u003cli\u003eSalinas-de-Le\u0026oacute;n, P., Dryden, C., Smith, D., \u0026amp; Bell, J. (2013). Temporal and spatial variability in coral recruitment on two Indonesian coral reefs: consistently lower recruitment to a degraded reef. \u003cem\u003eMarine Biology\u003c/em\u003e,\u003cem\u003e 160\u003c/em\u003e(1), 97-105. \u003c/li\u003e\n\u003cli\u003eS\u0026aacute;nchez-Quinto, A., \u0026amp; Falc\u0026oacute;n, L. I. (2019). Metagenome of Acropora palmata coral rubble: Potential metabolic pathways and diversity in the reef ecosystem. \u003cem\u003ePlos one\u003c/em\u003e,\u003cem\u003e 14\u003c/em\u003e(8), e0220117. \u003c/li\u003e\n\u003cli\u003eStewart, H. L., Holbrook, S. J., Schmitt, R. J., \u0026amp; Brooks, A. J. (2006). Symbiotic crabs maintain coral health by clearing sediments. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 25\u003c/em\u003e, 609-615. \u003c/li\u003e\n\u003cli\u003eStorlazzi, C. D., Field, M. E., \u0026amp; Bothner, M. H. (2011). The use (and misuse) of sediment traps in coral reef environments: theory, observations, and suggested protocols. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 30\u003c/em\u003e(1), 23-38. https://doi.org/10.1007/s00338-010-0705-3 \u003c/li\u003e\n\u003cli\u003eViehman, S., Hench, J. L., Griffin, S. P., Malhotra, A., Egan, K., \u0026amp; Halpin, P. N. (2018). Understanding differential patterns in coral reef recovery: chronic hydrodynamic disturbance as a limiting mechanism for coral colonization. \u003cem\u003eMarine Ecology Progress Series\u003c/em\u003e,\u003cem\u003e 605\u003c/em\u003e. https://doi.org/10.3354/meps12714 \u003c/li\u003e\n\u003cli\u003eWakwella, A., Mumby, P. J., \u0026amp; Roff, G. (2020). Sedimentation and overfishing drive changes in early succession and coral recruitment. \u003cem\u003eProceedings of the Royal Society B\u003c/em\u003e,\u003cem\u003e 287\u003c/em\u003e(1941), 20202575. \u003c/li\u003e\n\u003cli\u003eWakwella, A., Mumby, P. J., \u0026amp; Roff, G. (2020). Sedimentation and overfishing drive changes in early succession and coral recruitment. \u003cem\u003eProceedings of the Royal Society B-Biological Sciences\u003c/em\u003e,\u003cem\u003e 287\u003c/em\u003e(1941). https://doi.org/ARTN 20202575 10.1098/rspb.2020.2575 \u003c/li\u003e\n\u003cli\u003eWolfe, K., Kenyon, T. M., \u0026amp; Mumby, P. J. (2021). The biology and ecology of coral rubble and implications for the future of coral reefs. \u003cem\u003eCoral reefs\u003c/em\u003e,\u003cem\u003e 40\u003c/em\u003e(6), 1769-1806. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"rubble, coral settlement, post-settlement survival, substrates","lastPublishedDoi":"10.21203/rs.3.rs-7993495/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7993495/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBeds of dead coral rubble are widely reported to impede coral recovery, and causation has been linked to rubble instability. However, additional environmental factors, including flow and sedimentation, may also impact coral recruitment in this habitat. Indeed, the drivers of coral recruitment likely differ with the type of rubble. Here, we experimentally remove the influence of rubble mobility and evaluate how different rubble environments influence the process of coral settlement and recruitment (a loose vs. interlocked rubble habitat). Stabilised rubble recruitment tiles were deployed both flush with the substrate and elevated 20 cm above the substrate to separate substrate/environmental effects from differential larval supply among treatments. Coral settlement was greatest on stabilised tiles deployed in the more structurally complex habitat (reef carbonate without rubble). Settlement declined by 2 to 4-fold in rubble habitats with high interlocking structure and declined even further (8-fold) in structurally simple, loose rubble. These trends reflect environmental drivers rather than any differences in rubble stability. Post-settlement mortality was high across stabilised tiles regardless of habitat. While recruitment tracked the improvement in settlement from loose to interlocked rubble, recruitment from interlocked rubble to reef habitat became comparable, 12 months post-deployment. Even if stabilised, loose rubble beds are likely to have low recovery prospects, whereas interlocked rubble beds can provide suitable coral substrates under the right environmental conditions. Rubble stabilisation alone will not increase coral recovery within certain types of rubble beds, and this should be considered when determining how or if restoration intervention is required.\u003c/p\u003e","manuscriptTitle":"Instability is not the only driver of rubble impacts on coral settlement and recruitment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-14 14:22:33","doi":"10.21203/rs.3.rs-7993495/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"00f453f8-fc94-4b6f-a294-4ec51a4c613c","owner":[],"postedDate":"November 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-09T23:53:43+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-14 14:22:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7993495","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7993495","identity":"rs-7993495","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}