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Integrating marine landscape classification with Maximum Entropy (MaxEnt) habitat suitability modelling can potentially develop thematic marine habitat models but has yet to be extensively studied. For Marine Protected Area (MPA) spatial planning, the application of such frameworks remains limited, especially in the Coral Triangle region. The absence of a standardised marine habitat mapping framework in this biodiverse area hampers ecosystem-based management for its transboundary MPA networks. This study aims to create a thematic map of potential coral reef habitats in Taman Laut Tioman, Malaysia, combining oceanic data and multiscale high-resolution multibeam echosounder bathymetry and backscatter data for marine landscape classification. Clustered environmental inputs and presence-only data from field surveys and citizen science were then applied in MaxEnt modelling. Despite limitations in spatial resolution, oceanic data—hydrodynamics and ocean colour satellite imagery—notably enhanced the model performance, showcasing the value of these variables even in smaller study areas. The final model identified four distinct marine landscape classes, providing a detailed abiotic profile that surpasses the continuous data controls and establishes a vital baseline for assessing ecological boundaries, serving as a precursor to biodiversity mapping and informing ecosystem-based management. This study provides important insight for developing a standardised framework to establish a transboundary network of MPAs in the Coral Triangle region to conserve its marine biodiversity. [ABSTRACT FROM AUTHOR]

Facetotecta, or “y-larvae”, are mysterious planktonic crustaceans that are known only from their larval instars, but which are often assumed to be endoparasitic as adults. Dozens of mostly undescribed forms occur in the shallow-water plankton over a fringing reef at Sesoko Island, Okinawa, Japan. Recently, it has become possible to discriminate the different forms of their nauplius-stage larvae (“y-nauplii”) in a replicable way. A large year-to-year overlap in morphospecies recovered during fieldwork at Sesoko Island in 2018, 2019, and 2023 suggests that a full inventory is close at hand. To date, 49 morphospecies of y-nauplii (8 planktotrophic, 41 lecithotrophic) have been recognized in the area, among which three have been formally described. A detailed analysis of the temporal fluctuations in abundance during October 2023 showed that most morphospecies were rare, but two were particularly common: Type A*, a planktotroph with a long (> 3 weeks) period of naupliar development allowing for long-distance dispersal, and Type AG*, a lecithotroph with a short (3 days) period of development that implies rapid local recolonization. During the survey, both types showed distinct, largely non-overlapping peaks in abundance, related perhaps to their different dispersal/feeding strategies. An examination of the morphology of the swimming/feeding appendages in y-nauplii of Types A* and AG*, together with a mapping of feeding versus non-feeding nauplii on a recent comprehensive phylogeny of Facetotecta, suggests that broader taxonomic coverage of naupliar feeding structures in this group may provide useful information regarding the evolutionary direction of planktotrophy versus lecithotrophy in marine larvae. [ABSTRACT FROM AUTHOR]

Coral thermal tolerance is intimately linked to their symbiotic relationships with photosynthetic microorganisms. However, the potential compensatory role of symbiotic photosynthetic bacteria in supporting Symbiodiniaceae photosynthesis under extreme summer temperatures remains largely unexplored. Here, we examined the seasonal variations in Symbiodiniaceae and photosynthetic bacterial community structures in Pavona decussata corals from Weizhou Island, Beibu Gulf, China, with particular emphasis on the role of photosynthetic bacteria under elevated temperature conditions. Our results revealed that Symbiodiniaceae density and Chlorophyll a concentration were lowest during the summer and highest in the winter. Notably, the summer bacterial community was predominately composed of the proteorhodopsin bacterium BD 1–7 _clade, alongside a significant increase in Cyanobacteria, particularly Synechococcus_CC9902 and Cyanobium_PCC-6307, which represented 61.85% and 31.48% of the total Cyanobacterial community, respectively. In vitro experiments demonstrated that Cyanobacteria significantly enhanced Symbiodiniaceae photosynthetic efficiency under high-temperature conditions. These findings suggest that the increased abundance of photosynthetic bacteria during summer may mitigate the adverse physiological effects of reduced Symbiodiniaceae density, thereby contributing to coral stability. Our study highlights a potential synergistic interaction between Symbiodiniaceae and photosynthetic bacteria, emphasizing the importance of understanding these dynamic interactions in sustaining coral resilience against environmental stress, although further research is necessary to establish their role in preventing coral bleaching. [ABSTRACT FROM AUTHOR]

The seasonal and interannual temporal variation in the composition, richness, diversity, and similarity of fish larval assemblages associated with an Eastern Tropical Pacific (ETP) coral reef system was studied in March (cold water) and September (warm water) during the years 2017, 2018, and 2019. Throughout the study period, we collected 4779 fish larvae and identified 88 taxa, encompassing 46 families. This increased the total number of recorded fish taxa for the region to 146. Fish larvae were collected by daytime and nighttime surface trawls, using a bongo net 30 cm in diameter and 180 cm in length, equipped with mesh sizes of 300 and 500 μm. The species diversity and abundance of ichthyoplankton over this ETP coral reef changed by intra-annual variation of the hydrological conditions of the upper layer of the sea. Six significant assemblages were identified (SIMPROF, p < 0.05), each one associated with each sampling period (ANOSIM, R = 0.764); Cetengraulis mysticetus, Diaphus pacificus, Anchoa sp., Anisotremus sp., Bremaceros bathymaster, Oligoplites saurus, Caranx sp., Seriola sp., Gobiidae sp., Microgobius sp., and Synodus evermanni were the species that contributed to dissimilitude between groups. Canonical correspondence analysis revealed significant associations between specific larval fish taxa abundance and temperature, salinity, dissolved oxygen, and zooplankton biomass. Overall, the assemblage of ichthyoplankton in this ETP coral reef system is sensitive to seasonal changes in water column hydrographic conditions. [ABSTRACT FROM AUTHOR]

Coral reef sponges efficiently take up particulate and dissolved organic matter (DOM) from the water column and release compounds such as nucleosides, amino acids, and other dissolved metabolites to the surrounding reef via their exhalent seawater, but the influence of this process on reef picoplankton and nutrient processing is relatively unexplored. Here we examined the impact of sponge exhalent on the reef picoplankon community and subsequent alterations to the reef dissolved metabolite pool. We exposed reef picoplankton communities to a sponge exhalent water mixture (Niphates digitalis and Xestospongia muta) or filtered reef seawater (control) in closed, container-based dark incubations. We used 16S rRNA gene sequencing and flow cytometry-based cell counts to examine the picoplankton community and metabolomics and other analyses to examine the dissolved metabolite pool. The initial sponge exhalent was enriched in adenosine, inosine, chorismate, humic-like and amino acid-like components, and ammonium. Following 48 h of exposure to sponge exhalent, the picoplankton differed in composition, were reduced in diversity, showed doubled (or higher) growth efficiencies, and harbored increased copiotrophic and denitrifying taxa (Marinomonas, Pontibacterium, Aliiroseovarius) compared to control, reef-water based incubations. Alongside these picoplankton alterations, the sponge treatments, relative to seawater controls, had decreased adenosine, inosine, tryptophan, and ammonium, metabolites that may support the observed higher picoplankton growth efficiencies. Sponge treatments also had a net increase in several monosaccharides and other metabolites including anthranilate, riboflavin, nitrite, and nitrate. Our work demonstrates a link between sponge exhalent-associated metabolites and the picoplankton community, with exhalent water supporting an increased abundance of efficient, copiotrophic taxa that catabolize complex nutrients. The copiotrophic taxa were often different from those observed in previous algae and coral studies. These results have implications for better understanding the multifaceted role of sponges on picoplankton biomass with subsequent potential impacts to coral and other planktonic feeders in oligotrophic reef environments. [ABSTRACT FROM AUTHOR]

Coral populations are being progressively thinned by climate change, which elevates the risk of reproductive failure from Allee effects during fertilization. Studies have shown that fertilization success improves during more intense and synchronized spawning, but the local dependence of fertilization on coral density remains unknown in wild populations. Here, we measure the fertilization success of individual colonies of the common table coral, Acropora hyacinthus in Palau, Micronesia. We find strong evidence of spatial Allee effects such that fertilization averaged 30% when colonies were in close proximity (<0.5 m), but this declined rapidly to less than 10% at a separation of 10 m and virtually zero by 15 to 20 m. The distance of a nearest neighbor conspecific, gravid colony is a better predictor of observing Allee effects than local colony density measured at several alternative scales (2 to 10 m). Spawning synchrony increases when corals are in close proximity, which may reinforce Allee effects as reproductive colonies become further separated. Fertilization success declined nearly threefold on a second night of spawning with higher wind despite there being more intensive spawning of colonies, highlighting the potential importance of prevailing weather in driving the outcome of mass spawning events. Overall, we find that the local population of A. hyacinthus achieved 71% of its fertilization potential. Further studies of spatial patchiness in coral populations are needed to generalize the likelihood of Allee effects, how climate change impacts reproductive function on reefs, and opportunities for restoration to safeguard reproductive success by reconnecting depleted coral populations. [ABSTRACT FROM AUTHOR]

The response of beach sedimentary geomorphology to consecutive storms is a complex process, especially for beaches surrounding an island. Variations in coastal sedimentary landforms, dynamic environments and levels of development and utilization lead to non-uniformity in storm response, which may become more pronounced when influenced by continuous storms. This study focuses on the beaches around Weizhou Island to investigate this non-uniformity. Based on the topographic, surface sediment and hydrodynamic data collected on site before and after the consecutive typhoons (Typhoons Lionrock and Kompasu), the study examines the characteristics of beach geomorphology and surface sediment. The results show significant differences in the geomorphological responses between the four zones along the island. On the plane, the deposition degree of Zone I beach gradually weakened from west to east, and most areas of Zone III beach appeared in an alternating state of erosion and deposition. The beaches of Zone II and Zone IV showed the characteristics of dramatic changes in the northern and central beaches and relatively stable in the southern beaches. On the profile, the beach deformation area mainly occurs in the middle and upper parts of foreshore and berm. The response intensity of beaches in zone I is the weakest, the response intensity of beaches in zone III is the most intense, and the response intensity of beaches in zone II and zone IV is relatively close. However, the performance of beach sediments in different regions before and after continuous typhoons is less different. Except that the beach sediments in Zone I were mainly refined, the beach sediments in other zones of Weizhou Island were relatively coarse, and the sediments in the middle and upper parts of the foreshore were the coarsest, with the sorting being the worst. The different combinations of incident waves and storm surges during the typhoons are the primary factors that lead to various geomorphological responses in different zones. The antecedent beach status, distributions of rock and coral reefs, and anthropogenic activities further exacerbate these differences. This work can provide reference for island beach protection and management. [ABSTRACT FROM AUTHOR]

The Xisha Islands constitute the largest coral reef archipelago on the northern margin of the Coral Triangle and are the largest coral reef archipelago among the islands in the South China Sea. This study employed various survey methods including underwater spearfishing, gill netting, handline fishing, longlining fishing, underwater visual surveys, and environmental DNA (eDNA). Additionally, historical data from 1956 to 2023 were reviewed to comprehensively analyze the adaptation characteristics of the fish community structure in the Xisha Islands. The Xisha Islands have documented a total of 874 coral reef fish species, categorized into 27 orders, 102 families, and 337 genera. Of these species, the order Perciformes demonstrated the greatest species richness, which represents 71.05% of the total fish species documented. The structure of coral reef fish communities in the Xisha Islands has undergone significant changes. Firstly, a significant decline in the population of large-sized and carnivorous fish species was observed. The proportion of large-sized fish species diminished by 6.02% (62 species), and the medium-sized fish species saw a reduction of 3.09% (51 species). In contrast, there was a surge of 9.12% in the small-sized fish species population. The carnivorous fish species experienced a decrease of 4.73% (102 species), while an increase was noted in the population of herbivorous and omnivorous fish species. Secondly, the numbers of orders, families, and genera have also significantly decreased, with noticeable declines in the average taxonomic distinctness (Delta +), the variation taxonomic distinctness (Lambda +), functional richness (FRic), and quadratic entropy (RaoQ). Thirdly, the similarity between fish species at different time periods is relatively low. Among different functional groups, large-sized and carnivorous fish species exhibit the lowest similarity, whereas herbivorous fish species exhibit the highest. The turnover of live coral fish species is also evident. Overall, the coral reef fish in the Xisha Islands are showing a trend towards herbivory, miniaturization, and a simplification in species composition and functionality. This study contributes to a better understanding and prediction of the adaptation trends in fish species composition in the Xisha Islands, which is crucial for ensuring the ecosystem services of coral reefs and for the conservation and restoration of ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Identifying the maximum coral cover that a coral community can sustain (i.e., its 'upper limit') is important for predicting community dynamics and improving management strategies. Here, we quantify the relationship between estimated upper limits and key environmental factors on coral reefs: hard substrate availability, temperature and water clarity. Location: Great Barrier Reef (GBR), Australia (over 1400 km). Time Period: 1990 to 2022. Major Taxa Studied: Scleractinian corals. Methods: We used 32 years of data on coral cover around reef perimeters. Each reef was divided into four wave‐exposure habitats depending on prevailing wind conditions. For each site, we determined if hard coral cover had reached a plateau or upper limit. Next, we extracted existing estimates of hard substrate availability, modelled water temperature and Secchi depth. Then, we quantified the relationship between these environmental variables and the upper limits. Results: We found varying upper limits across the GBR, with a median of 33% coral cover and only 17% of the estimated upper limits exceeded 50% coral cover. Upper limits increased towards the southern reefs. Our results show that upper limits increased with increasing hard substrate availability and decreased with temperature and, to a lesser extent, with water clarity. Main Conclusions: The upper limits estimated in this study are much lower than what is commonly assumed when modelling ecological dynamics, most likely resulting in predicted recovery rates being inappropriately high. Although hard substrate ultimately restricted upper limits, there are mechanisms constraining the proportion of hard substrate that is covered by hard corals. The negative relationship between temperature and upper limits cannot be explained by changes in macroalgal abundance but may be related to changes in species composition. The quantitative relationships between the upper limits of coral cover and environmental variables will provide critical information to prioritise sites for management interventions. [ABSTRACT FROM AUTHOR]

The sea bivalve clam Tridacna crocea inhabiting the shallow sea of tropical and subtropical zones lives with the symbiotic alga zooxanthella in its mantle. Zooxanthellae algae perform photosynthesis and supply nutrients to T. crocea. Recently, the abundance of T. crocea has decreased rapidly due to overfishing in coastal areas in Okinawa, Japan. T. crocea culture systems for mass production will contribute to the conservation of T. crocea and thus marine ecosystems. Environmental control methods for T. crocea culture have not been established because of a lack of knowledge about the appropriate environmental conditions for T. crocea growth. The present study was initiated to obtain basic data for developing environmental control methods for T. crocea land-based aquaculture. The effects of water temperature, dissolved oxygen concentration, and photosynthetic photon flux density (PPFD) on the O2 exchange rates of the symbiotic system of T. crocea and zooxanthella, which are indicators of photosynthesis and respiration in the system, and the effect of daily integrated PPFD on T. crocea growth were investigated. Basic knowledge was obtained for the development of optimal environmental control technology for T. crocea clam culture. The optimum water temperature and dissolved oxygen concentration for photosynthesis in this symbiotic system were 28 °C, 5–6 mgO2 L−1 and 500 μmol m−2 d−1, respectively. The optimum daily integrated PPFD for clam growth was 20 mol m−2 d−1. [ABSTRACT FROM AUTHOR]

The Andaman and Nicobar Islands are rimmed by discontinuous fringing reef that is in general wider on western margin vs the eastern margin. This study characterizes the facies updip from the modern fringing reefs to the present shoreline of south Andaman and Swaraj Dweep, and describes in detail the coral terraces/carpets within and above the inter-tidal zone representing the Holocene Fringing reef. Field studies, satellite, and drone datasets have been utilized to map different facies, that include: coralgal boundstone, biodetrital-grainstone, beachrock, and coralgal rudstone. Multiple exposed microatolls as well as coral terraces (coral carpets) of Acropora and Porites (dated 8.7-8.4 ka BP) have been identified within the intertidal zone (Radhanagar Beach, Swaraj Dweep) indicating that Holocene fringing reef have down-stepped offshore to the current location of modern fringing reefs owing to either tectonics or eustasy. The eustatic sea-level fluctuations are relatively well established for the Holocene and we compute the tectonic uplift rates utilizing the stream-power-incision and linear-inversion model. A tectonic uplift rate of ~ 0.05 mm/yr (for Swaraj Dweep) during the past 100 ka is estimated, while taking into account a wide range of erodibility indexes and response time intervals. It is identified that the computed uplift rate is an amalgamation of the coseismic deformation along with the interseismic and aseismic surface deformation. Thus, not all exposed coral terraces/microatolls are exposed due to coseismic deformation (for example uplift in parts of Andaman due to earthquake in 2004). The average long-term uplift rates are a magnitude lower than the eustatic sea-level fall rates during Holocene, thus, we suggest that most of the Holocene fringing reefs are exposed due to eustatic sea-level fall and down-stepped to the current location of the modern fringing reefs. This would entail that the eustatic sea-level change rates would play a significant role in determining future of the modern fringing reef (catch-up vs keep up vs give up), and the coastal morphology of south Andaman and Swaraj Dweep, with implications for coastal inundation and stability in the scenario of climate change. [ABSTRACT FROM AUTHOR]

Macroalgal beds are increasingly recognised as nursery habitats for coral reef fish; however, the extent to which they are used as a source of food and/or a refuge from predation remains largely unexplored. Here, we investigate the distribution, feeding behaviour, diet, and predation risk for juvenile rabbitfish in macroalgal habitats on Orpheus Island, Great Barrier Reef. Visual surveys revealed that juvenile and adult Siganus doliatus had different among-habitat distributions with juveniles being largely restricted to the reef flat and positively associated with macroalgal cover, while adults were abundant on the reef crest. Focal feeding observations show that within macroalgal habitats, juvenile S. doliatus targeted epiphytes on Sargassum (80% of bites), with relatively few bites taken on turfs or the Sargassum itself (27% and 8%, respectively). These observations were supported by stomach content analyses with filamentous algae being the dominant item in the stomach content of both small (< 4 cm total length, TL; 58%) and large juvenile S. doliatus (> 4 cm TL; 47%). The stomach content of juvenile S. doliatus, S. canaliculatus, and S. spinus collected from macroalgal habitats was similar, consisting primarily of filamentous algae and detritus. We found no relationship between the abundance of potential predators and juvenile rabbitfishes across the study sites. Collectively, our results suggest that juvenile rabbitfishes are using macroalgal habitats on this, and potentially other, inshore reefs as a food source and add to a growing body of literature highlighting the importance of these habitats for the early life stages of reef fish. [ABSTRACT FROM AUTHOR]

Most comparative studies assessing reef health focus on living hard coral cover as the key metric. In Indonesia, in situ monitoring of coral cover has been ongoing for over five decades. However, as monitoring data and research findings are predominantly published in the local language (Bahasa Indonesia), local data often escape global attention, resulting in Indonesian coral reefs receiving less scientific attention despite accounting for ~ 15% of all coral reef area globally. Here, we systematically compiled both globally and locally published data on coral cover across Indonesia to assess changes over recent decades. We analysed 7,614 data entries extracted from 621 publications and found that the majority (79.1%) of the publications were written in Bahasa Indonesia, constituting 63.4% of the total data entries. Our dataset revealed limited evidence of net declines in coral cover over the last three decades (1994–2022). There was also no clear relationship between coral cover and human density, as well as with the thirteen environmental/anthropogenic drivers examined. We discuss several factors that may contribute to this lack of detectable large-scale change including: recent data potentially representing a 'shifted baseline'; the 'averaging out' of localised changes in coral cover dynamics at a broad scale; sampling biases; and/or the potential resilience of Indonesian coral reefs compared to other regions. This study highlights the wealth of accessible local coral reef data published in languages other than English and emphasises the importance of using such data to enhance our understanding of the long-term dynamics of coral reef ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Owing to the high spatial heterogeneity of substrate types and terrain, the present satellite-derived bathymetry (SDB) methods have low accuracy in deriving large-scale bathymetry in coral reef habitats. Taking 11 coral reefs of Xisha Islands (ocean area of 607 km2) in the South China Sea as the study area, a parametric multimodel combination approach based on geomorphic segmentation (PMCGS) for obtaining bathymetry was constructed by combining the Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) data with Gaofen-1 (GF-1) medium- and Worldview-2/3 (WV-2/3) high-resolution multispectral images. In this approach, five parametric SDB models were trained in each geomorphic zone by combining ICESat-2 and multispectral satellite images. Then, the optimal SDB models of each geomorphic zone were combined and extrapolated to other coral reefs in the same geomorphic zone. Results showed that the multiple ratios model was optimal for the reef flat, shallow lagoon, and patch reef zones. The binomial model was optimal for the reef slope and deep lagoon zones. Validated by the in situ bathymetric data and ICESat-2 data, the bathymetry inverted using the PMCGS had an RMSE of 0.91 m in GF-1 image and 0.70–0.88 m in WV-2/3 images when extrapolated to other reefs, which is significantly more accurate than active–passive one entire model methods with the same resolution. Our method performed better at 0–10 m and 15–25 m depth than the results obtained from previous studies, especially in the shallow water areas of the reef flat and shallow lagoon. The proposed PMCGS can efficiently improve the bathymetry inversion accuracy of medium- and high-resolution satellite images and it has great potential applications in deriving large-scale bathymetry, especially in Indo-Pacific coral reef habitats.

Abstract Stony coral tissue loss disease (SCTLD) has swept through Florida reefs and caused mass mortality of numerous coral species. In the wake of these losses, efforts are underway to propagate coral species impacted by SCTLD and promote population recovery. However, numerous knowledge gaps must be addressed to effectively grow, outplant, and restore populations of the slower growing, massive species that were lost. Here, we used sexual recruits of Diploria labyrinthiformis spawned in captivity to understand how conditioning, coral size, and nutritional status at outplanting affect coral survivorship, growth, and susceptibility to predation. We found that ex situ conditioning with supplemental feeding increased coral growth rates, resulting in larger sized corals at the time of outplanting. In turn, these corals had higher growth rates in the field and a lower probability of being removed by predators than outplants that were conditioned in in situ nurseries. Additionally, we found that coral size was an important predictor of survivorship, suggesting that hastening the speed at which young corals grow and outplanting larger juveniles can improve restoration outcomes. Taken together, our results suggest that providing supplemental food to corals at ex situ facilities confers benefits that could help restore populations of massive coral species impacted by SCTLD.

Evaluating the effects of environmental events across both biophysical and social dimensions is important in establishing a holistic view of such events. This study focuses on the impact of a devastating heat stress incident that occurred in many locations across the Caribbean region and South Atlantic during the 2023 summer season. The survey and focus of data collection was within Monroe County, a unique nature-based setting south of Miami, Florida, USA. The impact of the heat wave is still being calculated at the time of submission of this paper, but indications are that there was a major negative impact. The survey and data collection sought to understand recreationists’ perceptions, knowledge, and behavior changes as result of the heat stress impact in the Florida Keys. Respondents were interviewed during community workshops in person and through an online sample of boating/angler license holders. The results indicated a change in behavior by some respondents, which may have a longer-term economic impact, along with trends of satisfaction with outdoor recreation over time. This rapid survey method can be applied to future scenarios where social and economic data are needed to fully contextualize environmental impacts in addition to biological endpoints.

It is crucial for reef revetments to respond dynamically to rigorous wave actions for structural stability and safety. A comprehensive analysis of the interaction between the wave force and wave overtopping in a reef revetment project was conducted based on wave flume experiments. This study explored how wave conditions, the water depth along the reef flat, and the proximity of the reef edge to the revetment project influenced wave overtopping and wave force patterns. The results indicate that as the incident wave height, period, and water depth along the reef flat increased, the average wave overtopping within the revetment project also increased. Additionally, higher levels of average wave overtopping occurred with the decrease in the distance between the revetment project and the reef edge. The peak wave force on the seawall of the revetment project was studied in response to various factors, including wave period, wave height, water depth along the reef flat, and distance to the reef edge. The changes in the maximum wave force reflected those of the average wave overtopping, with a strong linear correlation. The quantitative relationship between these variables was determined, and the wave forces on the seawall could be indirectly estimated using the average wave overtopping volume. This study provides an efficient methodology for assessing the dynamic attributes of revetment projects and the disaster risk of these structures. [ABSTRACT FROM AUTHOR]

Earth's ecological assemblages are rapidly being driven towards unprecedented, novel states. We know little about ecological novelty in our oceans, limiting our ability to detect, contextualise, and manage substantive anthropogenic change. This is especially true for novel states with altered functional compositions. Here, we provide a quantitative assessment of taxonomic and functional ecological novelty in historical coral communities across the east Australian coast, capturing changes in the composition of coral taxa and their traits over the past 1500 years. Taxonomically novel communities emerged more frequently and often unaccompanied by substantial trait compositional change while functional novelty was commonly observed alongside significant genus turnover. Novel coral communities themselves were rare, context‐dependent, and often associated with transitions in dominant genera. Our preliminary trait‐based community classifications complement classical taxonomic methods to uncover a history of ecological change in east Australian coral communities, helping provide important context for their present states and inform future responses under ongoing and intensifying human‐driven change. [ABSTRACT FROM AUTHOR]

Coral reefs are among the most sensitive ecosystems affected by ocean warming and acidification, and are predicted to collapse over the next few decades. Reefs are predicted to shift from net accreting calcifier-dominated systems with exceptionally high biodiversity to net eroding algal-dominated systems with dramatically reduced biodiversity. Here, we present a two-year experimental study examining the responses of entire mesocosm coral reef communities to warming (+2 ℃), acidification (-0.2 pH units), and combined future ocean (+2 ℃, -0.2 pH) treatments. Contrary to modeled projections, we show that under future ocean conditions, these communities shift structure and composition yet persist as novel calcifying ecosystems with high biodiversity. Our results suggest that if climate change is limited to Paris Climate Agreement targets, coral reefs could persist in an altered state rather than collapse. [ABSTRACT FROM AUTHOR]

Population surges of crown‐of‐thorns starfish (COTS) (Acanthaster spp.) are a leading cause of coral cover loss on Australia's Great Barrier Reef (GBR). While COTS culling has been undertaken since 2012 little is known about how the public perceive COTS culling or how perceptions vary among social groups. Drawing on survey data collected in 2018 and 2022 we test the relative influence of demographic variables, social and institutional variables, and beliefs concerning the risks and benefits of culling, on public acceptance for the culling of COTS on the GBR. In contrast with previous research suggesting a polarization of views, we found limited opposition to culling (12% in 2018 and 8% in 2022). Remaining respondents, however, were almost equally divided between those who agreed or strongly agreed with culling and those who were neutral or only slightly in agreement. The strongest predictors of support, in terms of standardized mean odds ratios, were the perceived social, environmental, and ethical responsibility of culling (1.57), the manageability of culling risks (1.46), the personal importance of the GBR to the respondent (1.33), trust in science to deliver solutions (1.30), confidence in management of the GBR (1.26), and how much of a threat respondents believed COTS posed to the Reef (1.25). These findings suggest public communications about COTS culling might usefully focus on how scientific understanding, ongoing research, ecosystem monitoring, and partnerships with Reef Traditional Owners and stakeholders guide operations. [ABSTRACT FROM AUTHOR]

The die‐off of the long‐spined sea urchin Diadema antillarum in the 1980s highlighted its crucial role as a primary grazer in tropical western Atlantic coral reefs. However, natural recovery has been slow, exacerbated by a new die‐off in 2022. Interest in actively restoring D. antillarum populations has grown with the emergence of culture and rearing techniques. Restocking reefs with laboratory‐reared urchins shows potential for enhancing coral reef resilience by reducing algal cover and promoting coral settlement, but success rates vary. Predation and migration contribute to low retention rates, with distinguishing between them is challenging. In this study near Saba, Caribbean Netherlands, we released 200 laboratory‐reared D. antillarum on a reef and monitored for D. antillarum retention and potential D. antillarum predator presence and interaction for 35 days. Only 40% of the urchins were still present on the reef after day one. The Spanish hogfish Bodianus rufus was identified as the primary daytime predator, responsible for nine direct predation events. No nighttime predation was observed, but interaction with a batwing coral crab Carpilius corallinus was noted. These insights can help optimize future restocking attempts and emphasize the importance of assessing predator presence beforehand. Reefs with high abundances of predators such as Spanish hogfish should be avoided for D antillarum restocking. In addition, before being released, lab‐reared animals should be given time to acclimate to conditions in the wild by being placed in protected in situ cages. Here, they could also grow to larger sizes that are less vulnerable to predation. [ABSTRACT FROM AUTHOR]

Fertile hybrids can enhance the adaptive capacity and resilience of species under stress by increasing genetic diversity within populations, masking the effects of deleterious recessive alleles, and facilitating the introgression of beneficial genetic variants into parental species. However, many hybrids are infertile. We compared the fertility of aquarium‐reared F1 hybrid and purebred corals of the species Acropora loripes and Acropora kenti and examined the viability of early life stages of second‐generation (F2) hybrid and back‐crossed planula larvae and recruits. The F1 hybrids spawned viable gametes and the F2 hybrid and back‐crossed embryos developed into planula larvae and settled to become sessile coral recruits. The F1 hybrids had greater reproductive fitness than the F1 A. loripes purebred stock in an aquarium environment based on their probability of spawning and their fertilization success in crosses using their gametes. Interspecific coral hybrids can therefore be fertile and have high reproductive fitness, which could benefit the persistence of threatened coral reefs. [ABSTRACT FROM AUTHOR]

Stony coral tissue loss disease (SCTLD) has swept through Florida reefs and caused mass mortality of numerous coral species. In the wake of these losses, efforts are underway to propagate coral species impacted by SCTLD and promote population recovery. However, numerous knowledge gaps must be addressed to effectively grow, outplant, and restore populations of the slower growing, massive species that were lost. Here, we used sexual recruits of Diploria labyrinthiformis spawned in captivity to understand how conditioning, coral size, and nutritional status at outplanting affect coral survivorship, growth, and susceptibility to predation. We found that ex situ conditioning with supplemental feeding increased coral growth rates, resulting in larger sized corals at the time of outplanting. In turn, these corals had higher growth rates in the field and a lower probability of being removed by predators than outplants that were conditioned in in situ nurseries. Additionally, we found that coral size was an important predictor of survivorship, suggesting that hastening the speed at which young corals grow and outplanting larger juveniles can improve restoration outcomes. Taken together, our results suggest that providing supplemental food to corals at ex situ facilities confers benefits that could help restore populations of massive coral species impacted by SCTLD. [ABSTRACT FROM AUTHOR]

AbstractPorous coral reef limestone (CRL) is characterized by the low strength and developed pore structure, so improving its physico-mechanical properties is important for marine engineering construction work. Chemically consolidated porous CRL was prepared by taking a non-granular chemical grout (sodium silicate) as the main consolidation material. Then, the chemical consolidation effect was evaluated from two aspects (both the physical and mechanical properties) by conducting computed tomography (CT) scanning and quasi-static uniaxial compression tests. The results indicate that the consolidation material can fill the pores in the CRL, which reduces the porosity of specimens by more than 50%. In addition, the peak strength under quasi-static compression is increased by about 20%. The fragments decrease at failure, and fracture plane slip and crack opening are inhibited. Finally, influences of the special banded shape of consolidation material retained in the specimens on the failure process and failure mode of specimens were investigated. The chemical consolidation mechanism of porous CRL was revealed by combining with the scanning electron microscope (SEM) images. Research results indicate that the non-granular chemical material (sodium silicate) improves the physico-mechanical properties of porous CRL. The research provides reference for the foundation treatment in coral reefs and the design of consolidation schemes for surrounding rocks of underground spaces in marine engineering operations. [ABSTRACT FROM AUTHOR]

Understanding the wave and current conditions of coral reef ecosystems is essential for maintaining their health, as many reef processes are controlled by these hydrodynamic conditions. In this study, high-frequency measurements of tides, waves, and currents were made using acoustic, electromagnetic, and pressure instruments over a 28-d period on the fore-reef and reef flat of a coral reef atoll in the South China Sea. The research revealed wave transformation, tidal and wave modulation of flow, and wave setup conditions for the first time at this typical atoll. Three large wave processes dominated by gravity waves (GWs) are observed in the fore-reef. The GWs are significantly attenuated on the reef flat, whereas infragravity (IG) waves strengthened. The tidal modulation of GWs and IG waves on the reef flat is significant when the incident wave height exceeded 1 m. In the fore-reef, the modulation of progressive tidal waves and large waves leads to relatively stronger upper-layer currents, and weak near-bottom currents are primarily attributed to the dissipation of tidal wave energy by the rough coral terrain. In calm conditions, flow variations on the reef flat are modulated by tides, thereby allowing seawater flow to pass through the reef flat during spring tides. Conversely, during periods with large waves, tidal modulation of flow on the reef flat is less significant, and the cross-reef flow velocity increases with increasing incident wave height. The occurrence of wave setup on the reef flat enhances cross-reef flow towards the lagoon. The wave setup is positively linearly correlated with the incident wave height. The magnitude of wave setup is associated with the distance between the measurement sites on the fore-reef and reef flat. [ABSTRACT FROM AUTHOR]

Describing living community compositions is essential to monitor ecosystems in a rapidly changing world, but it is challenging to produce fast and accurate depiction of ecosystems due to methodological limitations. Morphological methods provide absolute abundances with limited throughput, whereas metabarcoding provides relative abundances of genes that may not correctly represent living communities from environmental DNA assessed with morphological methods. However, it has the potential to deliver fast descriptions of living communities provided that it is interpreted with validated species‐specific calibrations and reference databases. Here, we developed a quantitative approach to retrieve from metabarcoding data the assemblages of living large benthic foraminifera (LBF), photosymbiotic calcifying protists, from Indonesian coral reefs that are under increasing anthropogenic pressure. To depict the diversity, we calculated taxon‐specific correction factors to reduce biological biases by comparing surface area, biovolume and calcite volume, and the number of mitochondrial gene copies in seven common LBF species. To validate the approach, we compared calibrated datasets of morphological communities from mock samples with bulk reef sediment; both sample types were metabarcoded. The calibration of the data significantly improved the estimations of genus relative abundance, with a difference of ±5% on average, allowing for comparison of past morphological datasets with future molecular ones. Our results also highlight the application of our quantitative approach to support reef monitoring operations by capturing fine‐scale processes, such as seasonal and pollution‐driven dynamics, that require high‐throughput sampling treatment. [ABSTRACT FROM AUTHOR]

The elemental composition of coral skeletons supplies essential information about palaeoceanographic reconstructions. The present work aims to optimize the neutron activation analysis (NAA) protocol for determining Ca-substituting elements in coral skeletons, which can be considered as a potential indicator for reconstructing past climate variability. Conventional and epithermal NAA schemes have been applied to determine 22 elements. The results reveal that the use of epithermal NAA significantly improved the limits of detection, up to 10 times, for specific elements, e.g. As, Ba, Cd, Mn, Sr, etc. The Compton suppression counting regime yielded an additional improvement in the limits of detection. [ABSTRACT FROM AUTHOR]

Many studies related to marine ecotourism and coral reefs have been carried out in several locations in Indonesia. In TWP Gitanada, West Lombok, NTB coral reef habitat inventory and mapping was conducted in June 2021 by using Sentinel 2A satellite imagery and field observation. Geomorphologically, the TWP Gitanada area consisted of fringing reefs made of reef flat, fore reef/reef crest, reef slope, reef wall, and patch reef. The coral reef area is 450 ha and consists of > 200 types of coral reef benthic habitat, dominated by scleractinian corals (Acropora, Montipora, Porites and their associations with less dominant genera). All coral reef habitat data is presented here in a format which is suitable to attract the attention of visitors or tourists in understanding and supporting ecotourism development, which uses TWP Gitanada as a general case study which is relevant for all marine conservation and potential marine conservation throughout Indonesia. The information is helpful to identify which areas could be prioritized for conservation under the criteria of habitat richness or for further development by relevant stakeholders. [ABSTRACT FROM AUTHOR]

Coral reefs face a critical crisis worldwide because of rising ocean temperature, excessive use of resources and soil erosion. As reefs have great recreational and tourism value, the degradation of their quality may have a significant effect on tourism. This study employs a contingent behaviour approach to estimate the effect of reef extinction on the recreational demand for Kume Island, Okinawa, Japan. We propose a Poisson‐inverse Gaussian (PIG) model with correction for on‐site sampling issues to derive a more accurate estimate of consumer surplus (CS). The results show that the annual CS per‐person trip is 5898 yen (US$ 49.15 in 2015 currency) according to the random‐effects PIG model. [ABSTRACT FROM AUTHOR]

Coral reefs are exposed to various environmental stressors that cause bleaching events, whereby endosymbiotic microalgae (Symbiodiniaceae) disassociate from coral hosts. Bleached corals are compromised and face mortality. The combination of high-light exposure and elevated seawater temperature often lead to coral bleaching. The physiological properties of the Symbiodiniaceae within the coral tissues contribute to the thermal tolerance of the holobiont (the host and all its symbionts). The present study aimed to investigate the effects of light and temperature stress on four Symbiodiniaceae species from three genera with respect to photosynthetic oxygen production and consumption. Under control conditions, the species displayed predominantly low-to-moderate light requirements for photosynthesis with increased photoinhibition at higher photon flux rates. After 30 days of heat acclimation at 32 °C, maximum photosynthetic activity declined in Effrenium voratum, doubled in Fugacium kawagutii, and remained unchanged in Breviolum psygmophilum. In subsequent acute heating assays, species-specific effects on maximum photosynthetic activity were observed. Photosynthesis in all species declined across a temperature gradient between 25 and 39 °C in the acute heating assays; full inhibition occurred at 37 °C in B. psygmophilum and E. voratum and at 39 °C in B. aenigmaticum and F. kawagutii. In contrast, respiration remained largely constant in all species across temperatures. Our data point to species-specific photophysiological traits that lead to different thermal tolerances among Symbiodiniaceae. [ABSTRACT FROM AUTHOR]

The spatial distribution of coral reef biodiversity is regulated by a series of natural variables and human-induced factors such as depth, habitat availability, spatial variation, and management policies. However, spatial distribution patterns and management zoning strategy outcomes of coral reefs biodiversity are still scarce in several areas, such as Southwestern Atlantic Ocean Marine Protected Areas (MPAs). It has been previously demonstrated that better management strategies worldwide could be supported by better species distribution data. In the present study, a total of 94 reefs spatially distributed around the MPA Costa dos Corais (Northeastern Brazil) under different zoning strategies and ranging from 1 to 30 m depth were sampled. Our study is the first one to characterize biodiversity spatial distribution of the largest Brazilian coastal MPA Costa dos Corais biodiversity and the importance of management zoning as a major coral reef conservation strategy in Brazil. Highest coral cover (48.33%) and coral richness (6.31 species/20 m) have been recorded for North of Alagoas (NAL), and highest fish abundance (75.22 individuals/100 m2), richness (11.45 species/100 m2) and biomass (395.60 g/100 m2) were recorded for South of Alagoas (SAL). Yet, only fish richness and biomass were significantly different compared with other regions. Compared to other management zones, no-take zones had the highest coral cover and richness, and fish abundance, richness and biomass. Additionally, our findings have shown that depth positively influences fish and negatively influences coral biodiversity. Hence, management and zoning strategies have influenced the structure of coral reef communities with a series of different ecological effects highlighting the importance of those strategies for Southwestern Atlantic Ocean MPAs. [ABSTRACT FROM AUTHOR]

This editorial titled "Restoration of coastal marine ecosystems" discusses the importance of ecosystem restoration in coastal marine habitats and the goals set by the United Nations to protect and restore degraded ecosystems. It highlights the challenges and uncertainties associated with large-scale restoration efforts in marine ecosystems and presents new insights and achievements in marine ecosystem restoration. The document covers various topics and ecosystems, including seagrass beds, macroalgal forests, estuarine wetlands, oyster reefs, and coral reefs, and provides successful restoration case studies. The article emphasizes the importance of stakeholder involvement, long-term monitoring, and measures to improve the resilience of restored ecosystems in the face of climate change. It concludes by calling for intensified and scaled-up restoration efforts, supported by government actions and partnerships with commercial and industrial sectors. [Extracted from the article]

The achievements in successfully establishing coral nurseries using asexually reproduced transplants in Kavaratti Island, Lakshadweep archipelago are presented. During the present study, the survival and growth of 180 fragments of corals fixed on concrete blocks with iron frames laid over a 40 m2 area near reefs inside the lagoon of Kavaratti atoll were assessed. Significant differences in growth were observed between acroporid and non-acroporid corals after two years of transplantation. Acropora muricata (31.1 ± 0.4 cm) and Isopora palifera (15.9 ± 3.4 cm) displayed the highest and lowest growth rates among acroporid corals and Pocillopora damicornis (481.9 ± 68.4 cm3) and Hydnophora microconos (33.4 ± 15.7 cm3) had the highest and lowest rates, among non-acroporid corals. A diverse fish assemblage comprising 21 species belonging to 10 families was observed at the transplantation site, with Chromis viridis and Dascyllus aruanus being the dominant species. The success achieved in this study makes it an ideal approach to be used elsewhere in the Lakshadweep archipelago and the wider Indian Ocean region to develop underwater tourism and promote science-based management and restoration of coral reefs. [ABSTRACT FROM AUTHOR]

Reef-building coral populations are at serious risk of collapse due to the combined effects of ocean warming and acidification. Nonetheless, many corals show potential to adapt to the changing ocean conditions. Here we examine the broad sense heritability (H2) of coral calcification rates across an ecologically and phylogenetically diverse sampling of eight of the primary reef-building corals across the Indo-Pacific. We show that all eight species exhibit relatively high heritability of calcification rates under combined warming and acidification (0.23–0.56). Furthermore, tolerance to each factor is positively correlated and the two factors do not interact in most of the species, contrary to the idea of trade-offs between temperature and pH sensitivity, and all eight species can co-evolve tolerance to elevated temperature and reduced pH. Using these values together with historical data, we estimate potential increases in thermal tolerance of 1.0–1.7°C over the next 50 years, depending on species. None of these species are probably capable of keeping up with a high global change scenario and climate change mitigation is essential if reefs are to persist. Such estimates are critical for our understanding of how corals may respond to global change, accurately parametrizing modelled responses, and predicting rapid evolution. [ABSTRACT FROM AUTHOR]

The deployment of engineered substrates seeded with newly settled corals is a technique being developed to increase the numbers of juvenile corals on reefs with the goal of improving reef resilience in response to climate warming. Using a hierarchical sampling design, we explored the spatial scales at which seeded coral (spat) survival and growth varied in situ and investigated the environmental drivers of seeded spat success in the southern inshore Great Barrier Reef. After 10 months, variation in spat survival and size was greatest at the smallest spatial scale (1–2 m) (27 and 11% of variation, respectively), indicating the scale at which the main drivers of post‐settlement survival and growth are occurring. Crustose coralline algae (CCA) cover on seeding units prior to deployment was a significant driver of short‐ and long‐term spat survival (22% of variation). Survival of Acropora millepora and A. muricata spat did not differ according to benthic community variation. Increasing cover of branching Acropora corals was correlated with decreased survival and the size of Montipora aequituberculata spat, although CCA cover on plugs remained the most influential factor determining survival. Interspecific variation in spat survival and size and higher survival and size in the side‐facing orientation of the seeding units suggest natural variation in response to the seeding method, warranting further experiments to refine species selection and deployment methods prior to upscaling. High within‐site variation in seeded spat survival and size highlights the need for future studies of ecological factors driving post‐settlement mortality at fine spatial scales. [ABSTRACT FROM AUTHOR]

Microhabitat associated fishes are expected to be negatively affected by coral reef degradation, given that many species are coral dwellers. However, the factors underlying this negative impact and the spatial scale(s) at which it occurs are poorly understood. We explored how habitat quality metrics and host preferences influence fish abundance across multiple spatial scales, using the functionally important cleaner fish Elacatinus evelynae as a study species. We surveyed fish at 10 sites in Curaçao that varied in coral cover and health. At the microhabitat scale, we found that E. evelynae group size increases on large, healthy corals and on some coral host species, namely Montastraea cavernosa. We also found that, although E. evelynae can occupy at least 10 coral host species, it selectively inhabits just three corals: M. cavernosa, Colpophyllia natans, and Diploria labrynthiformis. Scaling up to explore goby abundance along 30‐m transects, we did not find a clear relationship between live coral cover and goby abundance. However, goby abundance was substantially higher at one location with elevated coral cover and a high relative abundance of E. evelynae host species. Collectively, these results confirm that E. evelynae abundance is impacted by reef health. They also indicate that the species' long‐term persistence may depend on both the maintenance of healthy coral hosts and the gobies' plasticity in host preferences on changing reefscapes. Cryptobenthic fishes such as E. evelynae play a vital role in the ecosystem and understanding drivers of their abundance is important as reefs face increased degradation. [ABSTRACT FROM AUTHOR]

Submarine groundwater discharge (SGD) is a recognized contributor to the hydrological and biogeochemical functioning of coral reef ecosystems located along coastlines. However, the distribution, size, and thermal properties of SGD remain poorly understood at most land–reef margins. We developed, deployed, and demonstrated an operational method for airborne detection and mapping of SGD using the 200 km coastline of western Hawai'i Island as a testing and analysis environment. Airborne high spatial resolution (1 m) thermal imaging produced relative sea surface temperature (SST) maps that aligned geospatially with boat-based transects of SGD presence–absence. Boat-based SST anomaly measurements were highly correlated with airborne SST anomaly measurements (R2 = 0.85; RMSE = 0.04 °C). Resulting maps of the relative difference in SST inside and outside of SGD plumes, called delta-SST, revealed 749 SGD plumes in 200 km of coastline, with nearly half of the SGD plumes smaller than 0.1 ha in size. Only 9% of SGD plumes were ≥1 ha in size, and just 1% were larger than 10 ha. Our findings indicate that small SGD is omnipresent in the nearshore environment. Furthermore, we found that the infrequent, large SGD plumes (>10 ha) displayed the weakest delta-SST values, suggesting that large discharge plumes are not likely to provide cooling refugia to warming coral reefs. Our operational approach can be applied frequently over time to generate SGD information relative to terrestrial substrate, topography, and pollutants. This operational approach will yield new insights into the role that land-to-reef interactions have on the composition and condition of coral reefs along coastlines. [ABSTRACT FROM AUTHOR]

The impacts of (repeat) bleaching events and the differential heat stress susceptibility of hard coral taxa are largely unknown in Malaysia, although it is part of the greater coral triangle. Here we determined bleaching trajectories of 46 hard coral taxa across- and within-reef scales based on data recorded during the first reported back-to-back coral bleaching occurrences in Malaysia between May 2019 and September 2020. Although the severity of coral bleaching in both years did not correspond to the rather small magnitude of heat stress observed, i.e., Degree Heating Weeks (DHW) of 1.05 °C-weeks and 0 °C-weeks in 2019 and 2020 respectively, we observed high levels of bleaching (55.21% and 26.63% of all surveyed colonies in 2019 and 2020, respectively). Notably, the bleaching response for both consecutive years was highly taxon-specific and significantly varied across- and within-reef scales. Mortality rates overall were low following the 2019 event, likely due to a rapid decrease in heat stress. Five of the 46 surveyed hard coral taxa exhibited more severe bleaching in 2020, despite a lower heat stress load. Interestingly, we observed low bleaching of ascribed susceptible taxa such as Acropora and Montipora, while we found taxa considered to be resilient, e.g. Heliopora and Porites, to exhibit severe bleaching, suggesting a reversal of bleaching hierarchies of taxa over time. Our findings provide a foundation for further coral bleaching studies in a region with few published records to enable more accurate regional assessments and to follow the trajectory of future coral bleaching events. [ABSTRACT FROM AUTHOR]