Despite extensive research on the western Pacific crown-of-thorns starfish (CoTS; Acanthaster cf. solaris), especially from Australia’s Great Barrier Reef (GBR), there are persistent knowledge gaps that constrain understanding and management. Given renewed population irruptions of CoTS on the GBR, alongside escalating climate impacts and direct anthropogenic pressures, a quantitative assessment of knowledge gaps was undertaken to identify research priorities and guide future efforts. In this study, 27 experts independently scored 206 research questions across seven Themes and 39 topics, based on four different criteria (Knowledge gap, Feasibility, Urgency, and Applicability). These questions were ultimately rationalized into 170 distinct questions, with scores aggregated across merged questions. Management was the highest scoring Theme for Urgency, Applicability, and overall. All but six of the 20 top-ranked questions were from the Management Theme and mainly related to Culling and/ or Monitoring. Most questions (158 out of 170) also scored highly for Feasibility, suggesting that there are existing methods and technical capability available to advance the extensive and diverse range of research questions that were posed, if resources were made available. This quantitative assessment provides guidance on the prioritization of potential research that could improve management of CoTS populations to improve coral protection outcomes on the GBR. This study also suggests that there are limited constraints to undertaking necessary research to address many of the persistent knowledge gaps relating to CoTS.

To recast Theodosius Dobzhansky’s famous 1973 quote: ‘nothing in coral taxonomy makes sense except in light of reticulate evolution’. Coral species evolve through the continual intermixing of ancestral lineages forming a network of changing genetic interconnections rather than stable hierarchical trees. Most species are not discrete units but rather are components of continua with variable genetic, morphological, and geographic boundaries. Hybridisation and introgression are key processes maintaining reticulated networks, making polyphyletic species (those with mixed evolutionary origins) potentially the norm. This creates grey zones of speciation where taxonomic divisions are uncertain and gene flow is ongoing. With this understanding, we critically review: (1) Sources of information for taxonomic decisions, including biology, population dynamics and the need for comprehensive field and foundational molecular studies capturing environment-correlated and geographic variations; (2) Nomenclature (a human construct) and taxonomy (which endeavours to reflect nature’s organisation): (3) Synonymy, including serial errors stemming from historical publications; (4) Type specimens, their use and misuse as a basis for taxonomic decisions; (5) Genus and species level agreements and disagreements between morphological and molecular taxonomies; (6) Use of the terms ‘cryptic species’, ‘cryptic variant’ and ‘cryptic lineage’; (7) Taxonomic decisions based on inferences beyond the scope of individual studies, creating nomenclatural instability and concern, not least among those working to address the impacts of climate change. This review also provides context for an extensive array of Factsheets and linked documentation about each of the species included in CoralsOfTheWorld.org (2026 in prep.).

Logging and plantation agriculture are vital to economies and livelihoods in tropical nations, including Papua New Guinea. To meet global demand, hundreds of thousands of ha of diverse natural habitat have been logged, cleared and replaced with monoculture crops. Resulting hydrological changes have increased sediment, nutrient and pesticide runoff, impacting down-stream habitats. Here, case studies from Kimbe Bay (New Britain) and Mullins Harbour (Milne Bay), examine effects on nearshore coral reefs. In both places, logging and oil palm development had destabilized soils and removed or degraded riparian vegetation. Downstream, nearshore reefs had high silt levels, which, coincident with minor coral bleaching and predation by crown-of-thorns starfish, were correlated with high levels of coral mortality and low coral species richness. Sediment and related impacts can be reduced by effective catchment management, such as avoiding steep slopes, expanding stream and coastal buffer zones, minimizing fertilizer and pesticide use, monitoring and reactive management.

Crown-of-thorns sea stars (Acanthaster sp.) are among the most studied coral reef organisms, owing to their propensity to undergo major population irruptions, which contribute to significant coral loss and reef degradation throughout the Indo-Pacific. However, there are still important knowledge gaps pertaining to the biology, ecology, and management of Acanthaster sp. Renewed efforts to advance understanding and management of Pacific crown-of-thorns sea stars (Acanthaster sp.) on Australia's Great Barrier Reef require explicit consideration of relevant and tractable knowledge gaps. Drawing on established horizon scanning methodologies, this study identified contemporary knowledge gaps by asking active and/or established crown-of-thorns sea star researchers to pose critical research questions that they believe should be addressed to improve the understanding and management of crown-of-thorns sea stars on the Great Barrier Reef. A total of 38 participants proposed 246 independent research questions, organized into 7 themes: feeding ecology, demography, distribution and abundance, predation, settlement, management, and environmental change. Questions were further assigned to 48 specific topics nested within the 7 themes. During this process, redundant questions were removed, which reduced the total number of distinct research questions to 172. Research questions posed were mostly related to themes of demography (46 questions) and management (48 questions). The dominant topics, meanwhile, were the incidence of population irruptions (16 questions), feeding ecology of larval sea stars (15 questions), effects of elevated water temperature on crown-of-thorns sea stars (13 questions), and predation on juveniles (12 questions). While the breadth of questions suggests that there is considerable research needed to improve understanding and management of crown-of-thorns sea stars on the Great Barrier Reef, the predominance of certain themes and topics suggests a major focus for new research while also providing a roadmap to guide future research efforts.

Indonesia is one of the most diverse nations in the world in terms of terrestrial and marine species. Many of these species and their habitats are, however, threatened by human activities. In marine ecosystems, the major perturbations to ecosystem health include coral mining, dredging and resort construction, industrial and agricultural effluents and oil spills, and fishing. Human activities have also been implicated in aggravating natural ecosystem stressors such as biotic erosion and coral predation and even climatic factors such as the frequency and intensity of El Niño Southern Oscillation (ENSO) events. In terrestrial ecosystems, the major disturbances include logging, forest fires, and deforestation due to agriculture. Adverse climactic conditions related to ENSO events have also been implicated in the occurrence of large-scale forest fires. Although a number of measures have been undertaken to stem the loss of marine and terrestrial habitats, these have often proved insufficient. To ensure the maintenance of a healthy natural environment in Indonesia, it is important to address the causes of habitat destruction and implement effective measures to mitigate the damage.

Species composition, habitat preferences, and community structure of zooxanthellate scleractinian corals in the upper mesophotic zone (UMZ, 30-60 m depth) of the central Indo-West Pacific (IWP) are described. A total of 340 species were recorded from 287 sites from the Andaman Sea across the Coral Triangle to Micronesia and Solomon Islands. This represents almost half of the reef-building coral species present in the central IWP, yet is far from complete. Species were categorized as either UMZ specialists (9 spp.), depth generalists (57 spp.), or with habitat preferences for the lower reef slope (63 spp.), mid-lower slope (172 spp.), or shallow slope (39 spp.). The five most common species in the UMZ were depth generalists (massive Porites spp.) or species that more commonly occur on mid-lower or lower reef slopes above the UMZ, such as Pachyseris speciosa, Acropora granulosa, Oxypora lacera, and Seriatopora hystrix. Only one of the ten most common corals, Acropora elegans, is an UMZ specialist. Percentages of species occurring in the UMZ ranged widely among genera, being highest in Euphyllia (100%), Leptoseris (92%), and Cycloseris (90%) and lower for speciose IWP genera Acropora (47%), Montipora (53%), and Porites (46%). Five broad, mid-lower slope coral communities extended into the UMZ, where seven coral assemblages were defined, each with greater or lesser biogeographic fidelity. We assess our findings in relation to the life histories of the species present and place these in the broader context of the "deep reef refugia" hypothesis.

Scleractinian corals, the main framework builders of coral reefs, are in serious global decline, although there remains significant uncertainty as to the consequences for individual species and particular regions. We assessed coral species richness and ranked relative abundance across 3075 depth-stratified survey sites, each < 0.5 ha in area, using a standardized rapid assessment method, in 31 Indo-West Pacific (IWP) coral ecoregions (ERs), from 1994 to 2016. The ecoregions cover a significant proportion of the ranges of most IWP reef coral species, including main centres of diversity, providing a baseline (albeit a shifted one) of species abundance over a large area of highly endangered reef systems, facilitating study of future change. In all, 672 species were recorded. The richest sites and ERs were all located in the Coral Triangle. Local (site) richness peaked at 224 species in Halmahera ER (IWP mean 71 species Standard Deviation 38 species). Nineteen species occurred in more than half of all sites, all but one occurring in more than 90% of ERs. Representing 13 genera, these widespread species exhibit a broad range of life histories, indicating that no particular strategy, or taxonomic affiliation, conferred particular ecological advantage. For most other species, occurrence and abundance varied markedly among different ERs, some having pronounced “centres of abundance”. Conversely, another 40 species, also with widely divergent life histories, were very rare, occurring in five or fewer sites, 14 species of which are ranked as “Vulnerable” or “Endangered” on the International Union for Conservation of Nature (IUCN) Red List. Others may also qualify in these Threatened categories under criteria of small geographic range and population fragmentation, the utility of which is briefly assessed.

This publication is an overview of a detailed study of coral distribution, diversity and affinities worldwide. The species distribution maps in www.coralsoftheworld.com are based on comprehensive global assessments of the world’s 150 coral ecoregions. Original surveys by the authors cover 4941 sites in 85 ecoregions worldwide. These are combined with a thorough summation of all biogeographic, taxonomic and related literature as well as an extensive review of museum and photographic collections worldwide and extensive inter-personal communications. Species occurrences in ecoregions are recorded as confirmed, strongly predicted, uncertain or absent. These data are used to present global maps of diversity and affinity at species level. There are two templates of Indo-Pacific diversity and affinity: one dominated by the Coral Triangle and one created by poleward continental boundary currents. There is a high degree of uniformity within the main body of the Coral Triangle; diversity and affinities both decrease in all directions. The Sunda Shelf ecoregion now qualifies for inclusion in the Coral Triangle and the Java Sea ecoregion is borderline. There is very little Indo-Pacific provincialism. Two separate centres of diversity occur in the Indian Ocean: the subequatorial west, and the Red Sea. Most species of the far eastern Pacific occur in the central Pacific. The Caribbean dominates Atlantic distribution and affinities and also has high uniformity. Individual ecoregions have very varying data comprehensiveness. Distribution patterns that distinguish between geographic variation within a species and the geographic overlap of sister species support the concept of reticulate evolution

Reef geomorphology, species composition and community structure of reef-building corals of Ninh Hai (south central Vietnam) were investigated from 2003-2011, contributing towards development of an integrated, representative national and regional network of Marine Protected Areas. Ninh Hai hosts extensive and diverse fringing coral reefs covering more than 2,300ha, the result of favourable physico-chemical conditions of sea temperature, water clarity, and sediment levels. These well-developed fringing reefs are rare or absent in other parts of Vietnam, and hence provide a high degree of complementarity to the developing national MPA network. The fringing reefs of Ninh Hai are in relatively good condition (average live coral cover > 25%), comprised of some 310 species from 60 genera of reef-building coral, including 11 species and one genus (Scapophyllia) previously unknown from the western South China Sea. Coral community structure shows considerable differences with other reefs in Vietnam. With the adjacent dry coastal forest ecosystem, these reefs are now protected within the Nui Chua National Park, one of very few examples of integrated conservation management of a terrestrial-coastal marine ecosystem in Vietnam or indeed Southeast Asia. The regular presence of cool water upwelling during the summer months may provide a "refuge" against future reef degradation from extensive coral death from 'bleaching' during episode of elevated sea temperatures. These reefs may thus aid in replenishment of other reefs, via dispersal and recruitment of corals locally and regionally.

This report describes the results of surveys of biodiversity and status of coral communities of Bali, surveyed in November 2008 (Nusa Penida area) and April-May 2011 (main island).This area forms part of the Nusa Tenggara region of the Lesser Sunda Islands, at the southern edge of the Coral Triangle (CT), earth's most diverse tropical marine province.The surveys were designed to assess biodiversity and ecological condition and identify sites of conservation priority, towards expanding and improving functionality of the Marine Protected Areas network.The surveys formed part of a collaborative project between Conservation International and partners, including the Indonesian Department of Nature Conservation (PHKA), the Indonesian Ministry of Marine Affairs and Fisheries (MMAF), the Indonesian Institute of Sciences (LIPI).A total of 85 stations (adjacent deep and shallow areas) at 48 sites (individual GPS locations) were surveyed.Coral communities were assessed in a broad range of wave exposure, current and sea temperature regimes, and included all main habitat types: cool water rocky shores, cool water reefs with broad flats, warm water reefs with broad to narrow flats, and coral communities developed on predominantly soft substrate.The survey area is characterized by highly localized, consistent variation in several key parameters for coral growth and reef development: current flow (ranging from ca < 1 knot to > 4 knots), temperature regime (ranging during this study from ca 23-30 C, but declining to 16 C at times) and wave energy regime (ranging from ca < 1 m -5 m), associated respectively with exposure to the Indonesian Throughflow in Lombok Strait, localized upwellings and long-period ocean swells from the Indian Ocean. Species richness and undescribed speciesBali host a diverse reef coral fauna, with a confirmed total of 406 reef-building (hermatypic) coral species.An additional 13 species were unconfirmed, requiring further taxonomic study.At least one species, Euphyllia spec.nov. is new to science, and a second, Isopora sp., shows significant morphological difference from described species, such that there are likely to be more than 420 hermatypic Scleractinia present, in total.Notably, several widespread species exhibit consistent local morpho-types around Bali.Within-station (point) richness around Bali averaged 112 species (s.d.42 spp.),ranging from a low of just two species (at site B22, a muddy non-reefal location) to a high of 181 species at B16 (Jemeluk, Amed).Other species-rich sites included Menjangan N (168 spp., site B26) and Penutukang (164 spp., site B21).These results for site and overall richness are similar to those from Bunaken National Park and Wakatobi (392 and 396 spp.respectively), higher than for Komodo and Banda Islands (342 and 301 spp.), and lower than Derewan, Raja Ampat, Teluk Cenderwasih, Fak-Fak/Kaimana and Halmahera (all with more ca 450 spp.or more). Community structureAt site level, 5 major coral community types were identified, related to levels of exposure to waves, currents -upwelling, substrate type and geographic location.These five communities were further sub-divided into 10 main coral assemblages.Each of the five communities was characterized by a more-or-less distinctive suite of species and benthic attributes.

Climate change will have far-reaching impacts on biodiversity, including increasing extinction rates. Current approaches to quantifying such impacts focus on measuring exposure to climatic change and largely ignore the biological differences between species that may significantly increase or reduce their vulnerability. To address this, we present a framework for assessing three dimensions of climate change vulnerability, namely sensitivity, exposure and adaptive capacity; this draws on species' biological traits and their modeled exposure to projected climatic changes. In the largest such assessment to date, we applied this approach to each of the world's birds, amphibians and corals (16,857 species). The resulting assessments identify the species with greatest relative vulnerability to climate change and the geographic areas in which they are concentrated, including the Amazon basin for amphibians and birds, and the central Indo-west Pacific (Coral Triangle) for corals. We found that high concentration areas for species with traits conferring highest sensitivity and lowest adaptive capacity differ from those of highly exposed species, and we identify areas where exposure-based assessments alone may over or under-estimate climate change impacts. We found that 608-851 bird (6-9%), 670-933 amphibian (11-15%), and 47-73 coral species (6-9%) are both highly climate change vulnerable and already threatened with extinction on the IUCN Red List. The remaining highly climate change vulnerable species represent new priorities for conservation. Fewer species are highly climate change vulnerable under lower IPCC SRES emissions scenarios, indicating that reducing greenhouse emissions will reduce climate change driven extinctions. Our study answers the growing call for a more biologically and ecologically inclusive approach to assessing climate change vulnerability. By facilitating independent assessment of the three dimensions of climate change vulnerability, our approach can be used to devise species and area-specific conservation interventions and indices. The priorities we identify will strengthen global strategies to mitigate climate change impacts.

Euphyllia baliensis sp. nov. (Hexacorallia: Scleractinia: Euphylliidae) is described from 10 specimens from Bali, Indone-sia. This species forms phaceloid colonies, and is distinguished morphologically from others in its genus by its compara-tively very small corallites (averaging 3 mm diameter) and much shorter, thinner, lightly calcified branches. It also exhibitsan unusual pattern for Hexacorallia in having four or eight primary and secondary septa. Living corals typically havefleshy polyps extended during the day. Tentacles are ‘anchor’, ‘kidney’ or ‘hammer’ shaped at their tips, occasionally withadditional smaller bulbous protuberances, the latter resembling ‘mittens’ or ‘gloves’. Tentacles are dull to dark reddish-brown with lime green bases and cream tips, becoming bluish on retraction. Type specimens were collected from 27-37 m depth off the central eastern coast of Bali, Indonesia. To date the species has not been reported from any other locality.

Hong Kong's coastal waters afford a marginal environment for coral reef growth, with high seasonal and short-term variability in water temperatures (ranging from < 14 degrees C in winter to 31 degrees C in summer), and low summer salinity (as low as 15 psu) due to runoff associated with the Asian wet monsoon season and the Pearl River Delta. Yet Hong Kong hosts 84 reef-building coral species in 28 genera of 12 families of the Scleractinia, distributed in 5 broad communities with strong geographic and environmental affinities and key indicator species. Coral communities farthest from the influence of the Pearl River Delta have relatively high sea bed coverage and species diversity (30 to 50% coverage, and > 30 spp. per site), and also host some large, old corals. X-radiographs of a core of one massive Porites colony confirms similar to 200 yr of growth, with 2 short-term periods of mortality, hidden in the skeleton by overgrowth. Very low linear extension rates (< 4 mm yr(-1)) in this coral and 2 others are anomalous for Porites corals and are indicative of the high-stress environment. Low growth rates suggest that other Hong Kong corals, despite the harsh environmental conditions, may also live for centuries, contributing to the development of 'incipient reefs'.

Spatial analyses of coral distributions at species level delineate the Coral Triangle and provide new insights into patterns of diversity and endemism around the globe. This study shows that the Coral Triangle, an area extending from the Philippines to the Solomon Islands, has 605 zooxanthellate corals including 15 regional endemics. This amounts to 76% of the world's total species complement, giving this province the world's highest conservation priority. Within the Coral Triangle, highest richness resides in the Bird's Head Peninsula of Indonesian Papua, which hosts 574 species, with individual reefs supporting up to 280 species ha(-1). The Red Sea/Arabian region, with 364 species and 27 regional endemics, has the second highest conservation priority. Reasons for the exceptional richness of the Coral Triangle include the geological setting, physical environment, and an array of ecological and evolutionary processes. These findings, supported by parallel distributions of reef fishes and other taxa, provide a clear scientific justification for the Coral Triangle Initiative, arguably one of the world's most significant reef conservation undertakings.

Three new species of Astreopora (Hexacorallia: Scleractinia: Acroporidae), from Cenderawasih Bay in West Papua, exhibit morphological innovations for this conservative genus, extant since the Cretaceous. Two species are fully branching, a condition never previously described for Astreopora: Astreopora cenderawasih sp. nov. has dendritic branching, also seen in the confamilial genus Montipora, whereas branches of A. acroporina sp. nov. possess an axial corallite, regarded as the key morphological innovation facilitating rapid diversification and dominance of reefs in the younger, confamilial and most diverse genus Acropora (staghorn corals). We propose that these novel characters may be parallelisms indicating deep familial homologies. The third species, Astreopora montiporina sp. nov., has expansive coenosteum, reminiscent of plating Montipora. The new species form part of the most species-rich Astreopora assemblage reported to date, comprising 14 species. The unique tectonic and eustatic history of Cenderawasih Bay may have played a role in the evolution of these new species.

This 14-year study (1989–2003) develops recovery benchmarks based on a period of very strong coral recovery in Acropora-dominated assemblages on the Great Barrier Reef (GBR) following major setbacks from the predatory sea-star Acanthaster planci in the early 1980s. A space for time approach was used in developing the benchmarks, made possible by the choice of three study reefs (Green Island, Feather Reef and Rib Reef), spread along 3 degrees of latitude (300 km) of the GBR. The sea-star outbreaks progressed north to south, causing death of corals that reached maximum levels in the years 1980 (Green), 1982 (Feather) and 1984 (Rib). The reefs were initially surveyed in 1989, 1990, 1993 and 1994, which represent recovery years 5–14 in the space for time protocol. Benchmark trajectories for coral abundance, colony sizes, coral cover and diversity were plotted against nominal recovery time (years 5–14) and defined as non-linear functions. A single survey of the same three reefs was conducted in 2003, when the reefs were nominally 1, 3 and 5 years into a second recovery period, following further Acanthaster impacts and coincident coral bleaching events around the turn of the century. The 2003 coral cover was marginally above the benchmark trajectory, but colony density (colonies.m−2) was an order of magnitude lower than the benchmark, and size structure was biased toward larger colonies that survived the turn of the century disturbances. The under-representation of small size classes in 2003 suggests that mass recruitment of corals had been suppressed, reflecting low regional coral abundance and depression of coral fecundity by recent bleaching events. The marginally higher cover and large colonies of 2003 were thus indicative of a depleted and aging assemblage not yet rejuvenated by a strong cohort of recruits.

Spatial analyses of coral distributions at species level delineate the Coral Triangle and provide new insights into patterns of diversity and endemism around the globe. This study shows that the Coral Triangle, an area extending from the Philippines to the Solomon Islands, has 605 zooxanthellate corals including 15 regional endemics. This amounts to 76% of the world's total species complement, giving this province the world's highest conservation priority. Within the Coral Triangle, highest richness resides in the Bird's Head Peninsula of Indonesian Papua which hosts 574 species, with individual reefs supporting up to 280 species ha-1. Reasons for the exceptional richness of the Coral Triangle include the geological setting, physical environment and an array of ecological processes. These findings, supported by parallel distributions of reef fishes and other taxa, provide a clear scientific justification for the Coral Triangle Initiative, arguably one of the world's most significant reef conservation undertakings.

The conservation status of 845 zooxanthellate reef- building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local- scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle ( western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures.