Coral Predators Research Articles

Genomic Single Nucleotide Polymorphism (SNP) markers and mitochondrial haplotypes illuminate the origins of Crown-of-Thorns Starfish (Acanthaster solaris) outbreaks in the South China Sea

BackgroundOutbreaks of the coral predator Crown-of-Thorns Starfish (CoTS) pose a severe threat to coral reefs in the Indo-Pacific Ocean. In 2018, the South China Sea (SCS) experienced significant CoTS outbreaks, leading to extensive coral mortality across the Xisha, Zhongsha, Dongsha, and Nansha Islands, severely impacting the coral reef ecosystem.ResultsTo explore the origins of these outbreaks, we conducted a comprehensive genomic analysis using data from genomic single nucleotide polymorphism sites (SNPs) and mitochondrial haplotypes. Our analysis reveals that CoTS populations in the SCS, which exhibit moderate genetic diversity and may have undergone positive selection or population expansion. There was limited genetic differentiation among CoTS populations from XS, ZS, and NS groups. Especially between the XS and ZS groups, there was almost no genetic differentiation. The populations from XS, ZS, and NS groups have strong genetic connections with populations in Vietnam and the Philippines. There was high gene flow from Vietnam to the Xisha Islands and from the Philippines to the Nansha Islands, suggesting that the CoTS populations in these regions primarily originate from these neighboring countries.ConclusionThe comprehensive analyses of SNP and mitochondrial genomes have provided valuable insights into the population genetics of CoTS. This research has generated significant genomic resources and facilitated important studies on the genetics of the CoTS species. By identifying potential source populations and understanding the genetic basis of their spread, managers can develop more effective conservation strategies to protect vulnerable coral reef ecosystems in the SCS.

Predicting 3D and 2D surface area of corals from simple field measurements

The structural architecture of coral reefs is a known predictor of species richness, fish biomass and reef resilience. At a smaller scale, three-dimensional (3D) surface area of corals is a fundamental determinant of physical and biological processes. Quantifying the 3D surface area of corals has applications for a broad range of scientific disciplines, including carbonate production estimates, coral predation studies, and assessments of reef growth. Here, we present morphotaxon-specific conversion metrics to estimate total 3D surface area and projected 2D surface area of individual colonies from simple field measurements of colony maximum diameter. Underwater photogrammetry techniques were used to quantify surface area and estimate conversion metrics. Bayesian models showed strong non-linear (power) relationships between colony maximum diameter and both total 3D surface area and projected 2D surface area for 13 out of 15 morphotaxa. This study presents a highly resolved and efficient method for obtaining critical surface area assessments of corals for various applications, including assessments of biotic surface area, tissue biomass, calcification rates, coral demographic rates, and reef restoration monitoring.

Ecological drivers of parrotfish coral predation vary across spatial scales

Parrotfishes (Labridae: Scarini) are widely recognized for their important functional role in reducing coral-algae competition by grazing algae, yet some species are also coral predators (corallivores) and thereby have direct negative impacts on corals they prey upon. To better understand the ecological drivers of parrotfish corallivory intensity, we compared patterns of relative predation scar size and abundance across spatial scales from individual coral colonies (<1 to several meters in size), to reefs within islands (1 to 10s of km), to 4 regions across the Greater Caribbean (100s to 1000s of km) including Panamá, Florida, St. Croix, and Bonaire. Across reef sites, there was a positive correlation of both parrotfish density and biomass with the relative coral area preyed upon, but not predation scar abundance. While there was no apparent site-level effect of coral cover on corallivory intensity, we found that the abundance of colonies preyed upon was positively correlated with both coral diversity and the proportional cover of frequently targeted coral taxa within localized 30 m2 reef areas. At the scale of individual coral colonies, we found that while numerous coral taxa were preyed upon, corallivory was concentrated on a few species across regions, such as Orbicella spp., Porites spp., and Stephanocoenia intersepta. Our findings suggest that while increased parrotfish densities may result in an increased coral area preyed upon across reefs, corallivory intensity within reefs may decrease in response to declines in the cover of frequently targeted coral taxa and overall coral diversity.Spanish and Papiamentu versions of the abstract are provided in the Supplement at www.int-res.com/articles/suppl/m740p145_supp.pdf

Priority sites for coral aquaculture in Kume Island based on numerical simulation

Global and local stresses such as increased water temperature and terrestrial sediment runoff significantly affect coral reef ecosystems. Over the past three decades, the increase in the intensity and frequency of coral bleaching has been a significant problem in tropical and subtropical coastal seas, and maintaining healthy coral reef ecosystems has long been a challenge. Coral cover in Shimajiri Bay on Kume Island, located in the Nansei Islands (Okinawa Prefecture, southern Japan), has declined due to exposure to high water temperatures, an outbreak of coral predators, and sediment (red soil) inflow from the land. From such a background, coral aquaculture has been implemented at a few stations in the bay. Therefore, it is essential to conduct aquaculture in suitable locations for coral growth and survival. This study aimed to select suitable locations for coral culture with high spatial resolution in an enclosed bay that was greatly affected by red soil runoff, mainly from a sugarcane field. A freshwater and red soil runoff model for the watershed was merged with a coastal hydrodynamic, red soil dispersal, and accumulation model at a spatial resolution of 75 m for Shimajiri Bay. The simulation results were validated using in situ continuous and routine observations. Simulations were conducted over ten years. Locations not subjected to high water temperature in the bay or river loading were selected based on topography, simulated water temperature, salinity, and red soil content of sea sediment. This coupled model enables us to evaluate the growth and survival conditions of cultured corals with high spatiotemporal resolution and quantitatively consider the reduction target of red soil runoff to realize robust coral growth and survival.

Chemosensory behaviour of juvenile crown-of-thorns sea star (Acanthaster sp.), attraction to algal and coral food and avoidance of adult conspecifics.

Intraspecific and habitat-mediated responses to chemical cues play key roles in structuring populations of marine species. We investigated the behaviour of herbivorous-stage juvenile crown-of-thorns sea stars (COTS; Acanthaster sp.) in flow-through choice chambers to determine if chemical cues from their habitat influence movement and their transition to become coral predators. Juveniles at the diet transition stage were exposed to cues from their nursery habitat (coral rubble-crustose coralline algae (CCA)), live coral and adult COTS to determine if waterborne cues influence movement. In response to CCA and coral as sole cues, juveniles moved towards the cue source and when these cues were presented in combination, they exhibited a preference for coral. Juveniles moved away from adult COTS cues. Exposure to food cues (coral, CCA) in the presence of adult cues resulted in variable responses. Our results suggest a feedback mechanism whereby juvenile behaviour is mediated by adult chemical cues. Cues from the adult population may deter juveniles from the switch to corallivory. As outbreaks wane, juveniles released from competition may serve as a proximate source of outbreaks, supporting the juveniles-in-waiting hypothesis. The accumulation of juveniles within the reef infrastructure is an underappreciated potential source of COTS outbreaks that devastate coral reefs.

New Goniasteridae and in situ observations significant to deep-sea coral predation

Eight new species, including one new genus, Armaster chondros n. gen. sp., Atheraster luma n. sp., Atheraster phaeos n. sp., Atheraster umbo n. sp., Circeaster dux n. sp., Evoplosoma besseyae n. sp., Evoplosoma mystrion n. sp. and Evoplosoma pharos n. sp. are newly described from Australian waters. Atheraster, Circeaster and Evoplosoma have been reported previously as predators on deep-sea octocorals. Evoplosoma, Gilbertaster and Hippasteria are members of the Hippasterinae, which have also been reported as predators on deep-sea corals and other cnidarians, suggesting that this interaction occurs in Australian deep-sea settings. Atheraster, Circeaster and Armaster are referred to a new subfamily, the Circeasterinae. Ecological and systematic implications for the Goniasteridae are discussed. An in situ observation of a myxasterid predating upon an octocoral is also reported.

High germline mutation rates, but not extreme population outbreaks, influence genetic diversity in a keystone coral predator.

Lewontin's paradox, the observation that levels of genetic diversity (π) do not scale linearly with census population size (Nc) variation, is an evolutionary conundrum. The most extreme mismatches between π and Nc are found for highly abundant marine invertebrates. Yet, the influences of new mutations on π relative to extrinsic processes such as Nc fluctuations are unknown. Here, we provide the first germline mutation rate (μ) estimate for a marine invertebrate in corallivorous crown-of-thorns sea stars (Acanthaster cf. solaris). We use high-coverage whole-genome sequencing of 14 parent-offspring trios alongside empirical estimates of Nc in Australia's Great Barrier Reef to jointly examine the determinants of π in populations undergoing extreme Nc fluctuations. The A. cf. solaris mean μ was 9.13 x 10-09 mutations per-site per-generation (95% CI: 6.51 x 10-09 to 1.18 x 10-08), exceeding estimates for other invertebrates and showing greater concordance with vertebrate mutation rates. Lower-than-expected Ne (~70,000-180,000) and low Ne/Nc values (0.0047-0.048) indicated weak influences of population outbreaks on long-term π. Our findings are consistent with elevated μ evolving in response to reduced Ne and generation time length, with important implications for explaining high mutational loads and the determinants of genetic diversity in marine invertebrate taxa.

Moving towards local participation and comanagement of Tioman Island Marine Park

Tioman Archipelago is a Marine Protected Area (MPA) off the coast of Pahang, Malaysia. It is inhabited by a small local population that depends on tourism as its main source of income. Its rich biodiversity is the main attraction to visitors, yet it is threatened by the growing tourism market. In 1994 the waters extending 3.7 km from the shore surrounding the island were gazetted as an MPA under the provisions of the Fisheries Act of 1985. The Department of Fisheries Malaysia (DoF) is responsible for the management and enforcement of the MPA, with minimal or no involvement of the local communities. A study conducted by Reef Check Malaysia (RCM) in 2014 with the local communities revealed that the vast majority showed an interest in being involved in management and conservation efforts but did not have the qualifications or the means to do so. In 2015, the Tioman Marine Conservation Group (TMCG) was formalized as a platform for interested local communities to undergo a series of training programs to empower them in building ecological resilience and marine resource management processes. The TMCG has since executed many conservation programs including ghost net removals, mooring buoy management, coral predator control, coral rehabilitation, reef monitoring surveys, community consultations, promotion of responsible tourism standards, and cleanups. RCM provided training, oversight, and funding. As of 2023, there are 80 members from each of the island’s seven villages. In 2019 the TMCG was officially recognized by the DoF as one of its strategic partners under its Reef Care program. This paper details how Tioman Island Marine Park moves from a top-down management approach towards local participation and a comanagement approach.

Effects of territorial damselfish on corallivorous fish assemblage composition and coral predation in the Mauritian lagoon

Predation is a significant stressor for many coral species. Understanding how predation interacts with factors such as climate change is key to coral conservation. Territorial damselfish of the genus Stegastes form territories on branching corals (genus Acropora) on which they cultivate algae, and while defending these territories, provide corals with indirect protection from predation. However, it is not known how the protection afforded by Stegastes spp. varies with corallivorous fish assemblage composition, nor whether corallivore assemblages themselves may be affected by the presence of Stegastes spp. and their associated Acropora spp. habitats. This study examined relationships among predation protection by Stegastes spp., branching Acropora coral cover, and the number and species richness of corallivorous fish present within a given area, namely the Mauritian lagoon in the western Indian Ocean. Predation on bleaching-resilient massive Porites lutea corals within and outside Stegastes territories was surveyed at sites around Mauritius island. Corallivorous fish assemblages, branching coral cover, and Stegastes spp. density were also surveyed at each site visit. Results show that high predation was correlated with the presence of high numbers of corallivores, but predation was lower within Stegastes spp. territories irrespective of all observed corallivore densities. Greater numbers of Stegastes spp. were correlated with increasing density of obligate corallivores. Non-Acroporid coral cover was positively correlated with species richness of obligate corallivores, while branching Acropora coral cover was negatively correlated with overall corallivore density. This study shows for the first time that predation on bleaching-resilient massive corals is lower within Stegastes spp. territories regardless of the number of corallivores present, adding to the growing body of knowledge on the complex relationships between Stegastes spp. and their environment. The findings also indicate possible effects of the presence of Stegastes spp. and their branching Acropora habitats on corallivorous fish density in areas with low coral diversity, which may warrant further study.

Juvenile waiting stage crown-of-thorns sea stars are resilient in heatwave conditions that bleach and kill corals.

The juveniles of predatory sea stars can remain in their recruitment-nursery habitat for some time before their ontogenetic shift to the adult habitat and diet. These small juveniles are vulnerable to a range of factors with their sensitivity amplified by climate change-driven ocean warming. We investigate the thermal tolerance of the waiting stage herbivorous juveniles of the keystone coral predator, the crown-of-thorns sea star (COTS, Acanthaster sp.), in context with the degree heating weeks (DHW) model that predicts coral bleaching and mass mortality. In temperature treatments ranging from +1 to 3°C in prolonged heatwave acclimation conditions, the juveniles exhibited ~100% survival in DHW scenarios that trigger coral bleaching (4 DHW), resulting in mass mortality of corals (8 DHW) and extreme conditions well beyond those that kill corals (12 DHW). This indicates that herbivorous juvenile COTS are far more resistant to heatwave conditions than the coral prey of the adults. The juveniles exhibited higher activity (righting) and metabolic rate after weeks in increased temperature. In separate acute temperature experiments, the upper thermal limit of the juveniles was 34-36°C. In a warming world, juvenile COTS residing in their coral rubble nursery habitat will benefit from an increase in the extent of this habitat due to coral mortality. The juveniles have potential for long-term persistence as herbivores as they wait for live coral to recover before becoming coral predators, thereby serving as a proximate source of COTS outbreaks on reefs already in a tenuous state due to climate change.

Tracking coral loss in the Spermonde Archipelago of Indonesia: 32 years of satellite monitoring from 1990 to 2022

ABSTRACT An alarming amount of damage has occurred to coral reefs in Indonesia, with the causes of such damage either from human activities (anthropogenic causes) or natural processes. This study investigated the long-term dynamic changes in coral reef habitats in eight selected islands in the Spermonde archipelago, Indonesia, using remote sensing and historical information. A series of Landsat images recorded in different years (i.e. 1990, 1996, 2002, 2008, 2013, 2016, 2018, 2019, and 2022) were used to map the benthic habitats of each island (i.e. live coral, dead coral, seagrass, sand, rubble, mix bottom). The analysis estimated a total of 303.47 hectares or 76.26% loss of live coral in studied islands since 1990. In contrast, there was a substantial increase in dead coral algae and rubble, estimated at around 108.63 and 101.91 hectares, respectively. Strong and similar negative coefficient determination between live coral cover with both dead coral algae (R2 = 0.96, Y = -2.95) and rubble (R2 = 0.94, Y = -2.85) suggested that human activities (e.g. destructive fishing activities, damage from anchors, coral mining) and natural processes (e.g. sedimentation, coral bleaching, coral diseases, and coral predation) played comparable roles in coral reef degradation in Spermonde Archipelago. Furthermore, this study revealed that destructive fishing occurred on the island regardless it was inhabited or uninhabited and was influenced by the extent of its live coral cover. This study overall highlighted the ongoing degradation and factors contributing to coral loss in the Spermonde archipelago. Further research and monitoring efforts are necessary to understand the mechanisms driving the decline in live coral and the factors contributing to increases in dead coral algae and rubble. This knowledge will aid in developing targeted conservation strategies and management plans to protect the coral reef ecosystem in the Spermonde Archipelago and other affected regions in Indonesia.

Improving coral cover using an integrated pest management framework.

Integrated pest management (IPM) leverages our understanding of ecological interactions to mitigate the impact of pest species on economically and/or ecologically important assets. It has primarily been applied in terrestrial settings (e.g., agriculture), but has rarely been attempted for marine ecosystems. The crown-of-thorns starfish (CoTS), Acanthaster spp., is a voracious coral predator throughout the Indo-Pacific where it undergoes large population increases (irruptions), termed outbreaks. During outbreaks CoTS act as a pest species and can result in substantial coral loss. Contemporary management of CoTS on the Great Barrier Reef (GBR) adopts facets of the IPM paradigm to manage these outbreaks through strategic use of direct manual control (culling) of individuals in response to ecologically based target thresholds. There has, however, been limited quantitative analysis of how to optimize the implementation of such thresholds. Here we use a multispecies modeling approach to assess the performance of alternative CoTS management scenarios for improving coral cover trajectories. The scenarios examined varied in terms of their ecological threshold target, the sensitivity of the threshold, and the level of management resourcing. Our approach illustrates how to quantify multidimensional trade-offs in resourcing constraints, concurrent CoTS and coral population dynamics, the stringency of target thresholds, and the geographical scale of management outcomes (number of sites). We found strategies with low target density thresholds for CoTS (≤0.03 CoTS min-1 ) could act as "Effort Sinks" and limit the number of sites that could be effectively controlled, particularly under CoTS population outbreaks. This was because a handful of sites took longer to control, which meant other sites were not controlled. Higher density thresholds (e.g., 0.04-0.08 CoTS min-1 ), tuned to levels of coral cover, diluted resources among sites but were more robust to resourcing constraints and pest population dynamics. Our study highlights trade-off decisions when using an IPM framework and informs the implementation of threshold-based strategies on the GBR.

Coral predation and implications for restoration of Kenyan reefs: The effects of site selection, coral species and fisheries management

Active coral reef restoration is increasingly applied for local reef management, but remains hampered by biological interactions such as coral predation (corallivory). To determine factors that drive corallivory and develop more ecology-based restoration approaches, coral and corallivore communities were characterized and fish bite mark densities quantified on natural coral colonies and fragments outplanted on small artificial structures. Six study sites were distributed equally among three levels of fisheries management at southern Kenyan reefs (fished < reserve < no-take). Obligate corallivorous fish densities strongly correlated with coral cover regardless of fisheries management level, whereas facultative corallivorous fish (mainly parrotfish) were most abundant in no-take zones. High corallivorous snail densities were associated with low coral diversity and corallivorous sea stars were scarce. Bite mark densities on natural reefs were clearly higher for branching corals, but did not correlate to coral cover, coral diversity or corallivorous fish densities. Compared to natural colonies, predation pressure was up to 24-fold greater on outplanted coral fragments and especially fierce inside no-take zones. This high predation pressure correlated with low live tissue cover of outplanted fragments. These results demonstrate that reefs with low coral cover, often targeted for restoration, do not necessarily experience greater coral predation and that improved outplanting methods and species considerations are needed to address high predation pressure on outplanted fragments. The interplay between fisheries management, reef restoration and corallivory warrants further scrutiny: while obligate corallivorous fish are unlikely detrimental to reef recovery, high densities of facultative corallivorous fish could hamper restoration efforts.

Variability in composition of parrotfish bite scars across space and over time on a central Pacific atoll

Parrotfishes are conspicuous herbivores, microvores, and detritivores in coral reef ecosystems, and the impacts of their feeding, particularly their capacity to expose reef carbonate, have received much attention. In many cases, parrotfish assemblages have been shown to control algal proliferation and promote the settlement of corals and crustose coralline algae (CCA). In extreme cases, high densities of parrotfishes may negatively affect net reef accretion through bioerosion and targeted coral predation. Most evidence describing the impacts of parrotfish foraging on benthic community structure is based upon correlations between benthic composition and parrotfish behavior or abundance, with much less known about process-based change of individual parrotfish bite scars through time. Here, we estimated parrotfish bite selectivity and determined the change in benthic composition within parrotfish bite scars relative to change in the overall reefscape using data collected over a 12-month duration from the fore reef habitat at Palmyra Atoll. We identified 2150 parrotfish bite scars which appeared most frequently on turf algae covered substrata but also on coral, CCA, and encrusting macroalgae. Of those bites taken on live coral, 96% of scars returned to live coral within 12 months. Notably, adult coral survivorship in bite scars was higher than at randomly sampled coral-covered locations not affected by parrotfish bites. The exposed substrate within bite scars was most commonly colonized by the dominant benthic functional group in the area immediately surrounding the scar. We found little evidence of coral recruitment to bite scars (1/2150); however, CCA growth on bites initially on turf algae increased from 18.4 to 32.9% across the two time intervals. Our results suggest that benthic areas affected by parrotfish bites were more likely to undergo a successional shift to a more calcified state relative to unaffected benthic areas, indicating that parrotfish grazing helps maintain highly calcified coral reef ecosystems.

Coral reef degradation at an atoll of the Western Colombian Caribbean.

Coral reef decline is an issue of concern around the globe. Remote and uninhabited coral areas are not exempt from facing changes in species composition and functionality due to global drivers. Quitasueño is a remote atoll within the Seaflower Biosphere Reserve, in the Southwestern Caribbean Sea. To evaluate the current status of the coral reefs in Quitasueño we sampled 120 stations through Rapid Ecological Assessment and evaluated four stations through Planar Point Intercept to compare the current percent cover of benthic groups with previous studies in the area. We found pronounced changes in coral and macroalgae covers in time, and great conspicuousness of multiple conditions of deterioration along Quitasueño, including diseases, coral predation, and aggression and invasion of coral colonies by macroalgae and sponges. The reef ecosystem seems to be facing a phase shift, in which the benthic cover previously dominated by hard corals is currently dominated by fleshy macroalgae. It is essential to evaluate the possible drivers of the extent of degradation of Quitasueño to understand the process of deterioration and mitigate the impacts.

Novel rubble-dwelling predators of herbivorous juvenile crown-of-thorns starfish (Acanthaster sp.)

Crown-of-thorns starfish (CoTS) are a pervasive coral predator prone to population outbreaks that have damaged coral reefs across Australia and the wider Indo-Pacific. CoTS population control through predation has been suggested as a primary mechanism that suppresses their outbreaks. However, the nature and rates of predation on CoTS are poorly resolved, especially for early life-history stages where they are expected to be most vulnerable. Here, we provide results from the first investigation of predators of CoTS during their rubble-dwelling, herbivorous, juvenile phase. We assessed the capacity of 104 common species of the rubble cryptofauna found across Heron Reef, Great Barrier Reef, Australia, to consume early-stage juvenile CoTS (0.8–3.8 mm) using controlled feeding experiments with laboratory-raised juveniles. We identified 26 novel CoTS predators, but only 10 species that regularly consumed juvenile CoTS in their entirety. Most cases of predation resulted in severed bodies and missing arms (i.e. sublethal predation) but not total consumption. We highlight one crustacean predator, Schizophrys aspera, the red decorator crab, which consumed whole juvenile CoTS in 89% of feeding trials and in excess of 5 CoTS d−1 in natural rubble mesocosms with alternative prey. This work emphasises the importance of predators at the critical juvenile stage that may control the build-up of CoTS populations prior to being detectable as an outbreak population.

Structure and proteomic analysis of the crown-of-thorns starfish (Acanthaster sp.) radial nerve cord

The nervous system of the Asteroidea (starfish or seastar) consists of radial nerve cords (RNCs) that interconnect with a ring nerve. Despite its relative simplicity, it facilitates the movement of multiple arms and numerous tube feet, as well as regeneration of damaged limbs. Here, we investigated the RNC ultrastructure and its molecular components within the of Pacific crown-of-thorns starfish (COTS; Acanthaster sp.), a well-known coral predator that in high-density outbreaks has major ecological impacts on coral reefs. We describe the presence of an array of unique small bulbous bulbs (40–100 μm diameter) that project from the ectoneural region of the adult RNC. Each comprise large secretory-like cells and prominent cilia. In contrast, juvenile COTS and its congener Acanthaster brevispinus lack these features, both of which are non-corallivorous. Proteomic analysis of the RNC (and isolated neural bulbs) provides the first comprehensive echinoderm protein database for neural tissue, including numerous secreted proteins associated with signalling, transport and defence. The neural bulbs contained several neuropeptides (e.g., bombyxin-type, starfish myorelaxant peptide, secretogranin 7B2-like, Ap15a-like, and ApNp35) and Deleted in Malignant Brain Tumor 1-like proteins. In summary, this study provides a new insight into the novel traits of COTS, a major pest on coral reefs, and a proteomics resource that can be used to develop (bio)control strategies and understand molecular mechanisms of regeneration.

Impacts of selective feeding of crown-of-thorns starfish on the coral community in the South China Sea

Context Crown-of-thorns starfish (Acanthaster spp., hereafter COTS), the most destructive predator of corals, selectively consume specific corals. However, their feeding selectivity varies among reef regions and differs from their feeding preferences in laboratory experiments. Aims In this study, the impacts of selective feeding of Acanthaster sp. on the coral community in the South China Sea were explored. Methods COTS predation on 701 coral colonies and 24 coral genera during 2018−2019 was evaluated. Key results Montipora had a greater scar cover (57%) than did Pocillopora (27%) because of COTS predation. Additionally, the relative abundance of encrusting Montipora (heat-tolerant corals) decreased from 40 to 14%, whereas that of branching Pocillopora (less heat-tolerant corals) increased from 40 to 60%. Moreover, the rare genera Millepora and Astreopora had the greatest scar cover (from 78 to ~100%) and feeding electivity values (from 0.66 to ~0.98), and were thus positively selected by COTS for predation. Further regional comparisons showed four types of feeding selection worldwide. Conclusions Less heat-tolerant coral became predominant in the coral community owing to selective feeding of COTS. COTS could consume rare, less-preferred corals by changing feeding selections. Implications These findings suggest that COTS not only directly consume coral individuals but also indirectly change the coral community composition, which is potentially related to the vulnerability of the coral community to global warming.

Biochemical metabolomic profiling of the Crown-of-Thorns Starfish (Acanthaster): New insight into its biology for improved pest management

The Crown-of-Thorns Starfish (COTS), Acanthaster species, is a voracious coral predator that destroys coral reefs when in outbreak status. The baseline metabolite and lipid biomolecules of 10 COTS tissues, including eggs from gravid females, were investigated in this study to provide insight into their biology and identify avenues for control. Targeted and untargeted metabolite- and lipidomics-based mass spectrometry approaches were used to obtain tissue-specific metabolite and lipid profiles. Across all COTS tissues, 410 metabolites and 367 lipids were identified. Most abundant were amino acids and peptides (18.7%) and wax esters (17%). There were 262 metabolites and 192 lipids identified in COTS eggs. Wax esters were more abundant in the eggs (30%) followed by triacylglycerols (TG), amino acids, and peptides. The diversity of asterosaponins in eggs (34) was higher than in tissues (2). Several asterosaponins known to modulate sperm acrosome reaction were putatively identified, including glycoside B, asterosaponin-4 (Co-Aris III), and regularoside B (asterosaponin A). The saponins saponin A, thornasteroside A, hillaside B, and non-saponins dictyol J and axinellamine B which have been shown to possess defensive properties, were found in abundance in gonads, skin, and radial nerve tissues. Inosine and 2-hexyldecanoic acid are the most abundant metabolites in tissues and eggs. As a secondary metabolite of purine degradation, inosine plays an important role in purine biosynthesis, while 2-hexyldecanoic acid is known to suppress side-chain crystallization during the synthesis of amphiphilic macromolecules (i.e., phospholipids). These significant spatial changes in metabolite, lipid, and asterosaponin profiles enabled unique insights into key biological tissue-specific processes that could be manipulated to better control COTS populations. Our findings highlight COTS as a novel source of molecules with therapeutic and cosmetic properties (ceramides, sphingolipids, carnosine, and inosine). These outcomes will be highly relevant for the development of strategies for COTS management including chemotaxis-based biocontrol and exploitation of COTS carcasses for the extraction of commercial molecules.

Changing the climate risk trajectory for coral reefs

Coral reefs are extremely vulnerable to climate change and their recent degradation will continue unless we can instigate strong global climate action with effective regional interventions. Many types of intervention have been proposed and some aspects of their deployment are now being tested. However, their long-term efficacy under climate change can only be evaluated using complex biophysical models applied over a range of plausible socio-economic pathways. The associated uncertainties in climate trajectories, ecological responses, and the mitigating effects of interventions, necessitate the use of a risk-based approach to evaluating model results. I show that ensemble modeling can be used to develop rigorous risk assessments suitable for comparing intervention strategies. A major strength of this approach is that all the key elements required for risk assessment (exposure, sensitivity, adaptive capacity, and impacts) can be generated by the model in a dynamically consistent form. This is a major advance on semi-quantitative climate change vulnerability risk assessments that estimate these quantities independently and then combine them under additional assumptions. Applying ensemble modeling risk assessment to the Great Barrier Reef (GBR) suggests that regional intervention strategies, such as solar radiation management (SRM) and control of coral predators, can slow the increase in risk and potentially avoid extreme risks predicted for the second half of the century. Model results further suggest that deployments focused within the northern and central GBR will be most effective due to underlying patterns of reef connectivity.