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Coral species at Christmas and Cocos Islands that are listed as Vulnerable to extinction this century on the IUCN Red List of threatened species. List of Vulnerable to extinction coral species
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Very little is known about the coral biodiversity in Australia’s remote Indian Ocean Territories; hence it is not possible to detect extinctions, depletions or to quantify changes in the coral fauna. Here we document the results of rapid visual assessment surveys of hard coral biodiversity at Christmas Island. This study provides a much-needed upda...
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... are classified as Least Concern (55%, 108 species) according to global IUCN red list categories and criteria ( Fig. 7; Appendix 1). 14% of the corals in the community (n = 27) are listed as Vulnerable to extinction this century (Table 4). Twenty-seven percent of the community (n = 54) are classified as Near Threatened, three species are Data Deficient and 5 species have not been assessed. ...
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... The CKI lie in a suture zone along the marine biogeographic boundaries of the Indian and Pacific Oceans and as such are comprised of species of Indo-West Pacific origin, with little endemism Woodroffe & Berry, 1994). The islands are renowned for their marine biodiversity; with a total of 602 recorded fish species , over 100 species of hard coral (Richards & Hobbs, 2014), 700 mollusc species (Tan & Low, 2014) and 200 crustacean species (Mendoza, Lasley, & Ng, 2014;Morgan, 1994). ...
Environmental DNA (eDNA) metabarcoding, a technique for retrieving multi‐species DNA from environmental samples, can detect a diverse array of marine species from filtered seawater samples. There is a growing potential to integrate eDNA alongside existing monitoring methods in order to establish or improve the assessment of species diversity. Remote island reefs are increasingly vulnerable to climate‐related threats and as such there is a pressing need for cost‐effective whole‐ecosystem surveying to baseline biodiversity, study assemblage changes and ultimately develop sustainable management plans. We investigated the utility of eDNA metabarcoding as a high‐resolution, multi‐trophic biomonitoring tool at the Cocos (Keeling) Islands, Australia (CKI) – a remote tropical coral reef atoll situated within the eastern Indian Ocean. Metabarcoding assays targeting the mitochondrial 16S rRNA and CO1 genes, as well as the 18S rRNA nuclear gene, were applied to 252 surface seawater samples collected from 42 sites within a 140 km2 area. Our assays successfully detected a wide range of bony fish and elasmobranchs (244 taxa), crustaceans (88), molluscs (37) and echinoderms (7). Assemblage composition varied significantly between sites, reflecting habitat partitioning across the island ecosystem and demonstrating the localisation of eDNA signals, despite extensive tidal and oceanic movements. In addition, we document putative new occurrence records for 46 taxa and compare the efficiency of our eDNA approach to visual survey techniques at CKI. Our study demonstrates the utility of a multi‐marker metabarcoding approach in capturing multi‐trophic biodiversity across an entire coral reef atoll and sets an important baseline for ongoing monitoring and management.
... The CKI is an Australian external territory located within the Indian Ocean and comprises 27 islands and associated fringing reefs within a coral atoll. They are located approximately 1080 km from Java and 2100 km from Western Australia, residing within the South equatorial current, making it a contact point for both Indian and Pacific Ocean fauna (Brewer et al. 2009;Hobbs and Allen 2014) and home to a diverse assemblage of corals, with a recorded total of 99 scleractinian coral species (Richards and Hobbs 2014). ...
Cumulative anthropogenic pressures have triggered a global decline in the health of marine ecosystems, and coral reefs, in particular, are in crisis. With climate and population-related pressures predicted to intensify in the coming decades, it is increasingly crucial to develop cost-effective and accurate monitoring tools to document changes to these important ecosystems. Environmental DNA (eDNA) coupled with metabarcoding is a powerful tool for surveying a wide variety of biota. Here, we develop a baseline eDNA toolkit targeting scleractinian corals and validate its performance in conjunction with data derived on traditional diver-based visual surveys at the Cocos (Keeling) Islands. Three assays targeting the ITS2 and 16S barcoding regions were designed, which broadly detected diversity within Scleractinia and Porifera. Our eDNA assays recovered 78 ITS2 operational taxonomic units (OTUs) from 25 scleractinian genera which is comparable to the level of diversity recorded on visual surveys (68 species from 26 genera). There were some notable differences in the species detected using eDNA versus visual records that may relate to either misidentifications, intragenic variation, differential assay performance or cryptic species. Our data demonstrate that a multi-assay eDNA analytical approach, applied on surface water collections, represents a powerful and complementary way to survey diversity that can also reveal fine scale spatial differentiation in community composition. With further refinement and improved reference databases, we envisage eDNA to become a powerful complement to visual surveys and to play a key role in monitoring the health and diversity of complex coral reefs ecosystems.
... Christmas Island's remote location lies 350 km south of Java and 1550 km north-west of mainland Australia. These isolated reefs are characterised by a rich diversity of reef fish and corals (Allen et al., 2007;Hobbs et al., 2014;Richards and Hobbs, 2014). Currents on the reef are dominated by the South Equatorial Current which originates from the east via the Indonesian Throughflow and a weaker anticyclonic gyre from north-west Australia (Davies and Beckley, 2010). ...
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-> Phosphate mining activities on Christmas Island began in the late 1800's providing a unique, long-term case study in which to assess the impacts of mining on coral reef development. Watershed modelling was used to identify potential “hotspots” of mining runoff on to adjacent reefs. Pollution hotspots were also confirmed by analysis of reef sediment. Phosphate rich mining runoff flowed from local watersheds onto nearshore coral reefs with levels of up to 54,000 mg/kg of total phosphate recorded in reef sediment at the Dryers reef site adjacent to the main phosphate storage facility. Using this combination of watershed modelling and in-situ sediment contamination data we identified six coral reef sites along an environmental impact gradient. In-situ benthic transects were paired with a new rubble-encruster method enabling the analysis to combine large scale transect information alongside fine-scale data on epibenthic and encruster assemblages. Results demonstrate that phosphate rich sediment loading negatively impacted coral reef building communities, in particular, branching corals and calcareous encrusting organisms, critical to the future survival of coral reef ecosystems. These findings highlight the importance of curtailing runoff and pollution from catchment based mining activities and protecting reefs for the future.
... The surface of Christmas Island is dominated by limestone karst that was built in part by coral growth over millions of years, and living corals are obviously essential elements of existing coral reefs, but ironically, the Cnidaria of Christmas Island are largely neglected (Beeton et al. 2010). Hard corals have received some little attention recently (Done and Marsh 2000;Richards and Hobbs 2014) but other Cnidarians are barely documented. Richards and Hobbs (2014) listed 169 known species of Scleractinia coral and five species of non-scleractinian coral (three Hydrozoa and two Octocoralia). ...
... Hard corals have received some little attention recently (Done and Marsh 2000;Richards and Hobbs 2014) but other Cnidarians are barely documented. Richards and Hobbs (2014) listed 169 known species of Scleractinia coral and five species of non-scleractinian coral (three Hydrozoa and two Octocoralia). Their species accumulation curves were close to asymptotic, although the southern coast was not surveyed. ...
... Planktonic forms were reported by Davies and Beckley (2010) only as 'Cnidaria'. There is no evidence that Christmas Island has any endemic species of Cnidaria (Richards and Hobbs 2014), with the possible exception of the Edwardsiella sp. Nevertheless, the composition of the coral community is biogeographically unique, but it is threatened by local pollution and invasive species (Richards and Hobbs 2014). ...
... Nevertheless, these data can provide insights into t e m p o r a l t r e n d s o f b i o d i v e r s i t y ( S h a ff e r e t a l . 1998; Hoeksema et al. 2011;Richards and Hobbs 2014). ...
Coral reefs worldwide are facing multiple severe stressors leading to ecosystem degradation, but local extinctions of species are not well documented. Here, we track the diversity of Pocilloporidae Gray, 1840 coral species—many of which are known to be sensitive to environmental disturbances—on Singapore reefs through time, integrating information from taxonomically verified museum specimens, careful examination of the literature, and DNA sequences. We found that more Pocilloporidae species were detected in the past than at present. A total of five species were historically recorded under Pocillopora Lamarck, 1816; Seriatopora Lamarck, 1816; and Stylophora Schweigger, 1820. Among the five species, only Pocillopora acuta Lamarck, 1816 appears to remain on Singapore reefs. The absence of Seriatopora for over half a century and the recent losses of Stylophora and the other species of Pocillopora are likely caused by habitat loss and other stressors associated with coastal urbanization, which have been further exacerbated by recent bleaching events.
... The surface of Christmas Island is dominated by limestone karst that was built in part by coral growth over millions of years, and living corals are obviously essential elements of existing coral reefs, but ironically, the Cnidaria of Christmas Island are largely neglected (Beeton et al. 2010). Hard corals have received some little attention recently (Done and Marsh 2000;Richards and Hobbs 2014) but other Cnidarians are barely documented. Richards and Hobbs (2014) listed 169 known species of Scleractinia coral and five species of non-scleractinian coral (three Hydrozoa and two Octocoralia). ...
... Hard corals have received some little attention recently (Done and Marsh 2000;Richards and Hobbs 2014) but other Cnidarians are barely documented. Richards and Hobbs (2014) listed 169 known species of Scleractinia coral and five species of non-scleractinian coral (three Hydrozoa and two Octocoralia). Their species accumulation curves were close to asymptotic, although the southern coast was not surveyed. ...
... Planktonic forms were reported by Davies and Beckley (2010) only as 'Cnidaria'. There is no evidence that Christmas Island has any endemic species of Cnidaria (Richards and Hobbs 2014), with the possible exception of the Edwardsiella sp. Nevertheless, the composition of the coral community is biogeographically unique, but it is threatened by local pollution and invasive species (Richards and Hobbs 2014). ...
... In addition, SST anomalies associated with other climate change modes like the Indian Ocean Dipole (IOD), Madden-Julian Oscillations (MJO) and Interdecadal Pacific Oscillation (IPO) can also dampen or exacerbate the ENSO thermal stress levels in the SEIO [18][19][20][21][22][23] . Some reefs in the SEIO experienced bleaching during both ENSO polarities, such as the Cocos Keeling Island 24,25 . ...
Episodic anomalously warm sea surface temperature (SST) extremes, or marine heatwaves (MHWs), amplify ocean warming effects and may lead to severe impacts on marine ecosystems. MHW-induced coral bleaching events have been observed frequently in recent decades in the southeast Indian Ocean (SEIO), a region traditionally regarded to have resilience to global warming. In this study, we assess the contribution of El Niño-Southern Oscillation (ENSO) to MHWs across the mostly understudied reefs in the SEIO. We find that in extended summer months, the MHWs at tropical and subtropical reefs (divided at ~20°S) are driven by opposite ENSO polarities: MHWs are more likely to occur at the tropical reefs during eastern Pacific El Niño, driven by enhanced solar radiation and weaker Australian Monsoon, some likely alleviated by positive Indian Ocean Dipole events, and at the subtropical reefs during central Pacific La Niña, mainly caused by increased horizontal heat transport, and in some cases reinforced by local air-sea interactions. Madden-Julian Oscillations (MJO) also modulate the MHW occurrences. Projected future increases in ENSO and MJO intensity with greenhouse warming will enhance thermal stress across the SEIO. Implementing forecasting systems of MHWs can be used to anticipate future coral bleaching patterns and prepare management responses.
... Taxonomic surveys conducted by the Western Australian Museum in 1987 identified 88 species of scleractinian corals across 38 genera at Christmas Island (Done & Marsh 2000). More recently, Richards & Hobbs (2014) documented 145 species of scleractinian coral from 51 genera, bringing the total number of sclerac-tinian corals known from the island to 169. However, these benthic and taxonomic surveys did not assess the spatial variation in coral community composition or structure around the island. ...
Coral communities are expected to display predictable patterns of diversity and structure across depth and exposure gradients yet these predictions have rarely been tested at oceanic locations. Here we tested five common ecological predictions about coral community structure at a remote oceanic island in the eastern Indian Ocean. Our results suggest that not all of the predictions hold true at this oceanic location primarily because the community is structured in non-linear ways. Each surveyed depth zone (5, 12, 20 m) supported a distinctive community, yet species diversity and coral abundance did not show the expected linear increase with depth. Habitat complexity was also shown to respond non-linearly with depth, with the highest habitat complexity occurring in the intermediate 12 m zone. We discuss the ‘cliff-edge effect’ as a possible explanation for the high diversity and abundance of corals at 20 m, while physical stress and competitive exclusion may explain the low diversity at 12 m. The cliff edge habitat provides a narrow zone in between the wave swept shallows and the low light/high shade environment of the steep outer reef walls and this zone of heterogeneous environmental conditions supports a wide diversity of corals. If future storm events, bleaching, disease or predator outbreaks were to impact the corals living in the cliff-edge habitat, this may have a disproportionate impact on the coral reef community as a whole. Monitoring the status of corals on the cliff-edge is important to understanding and predicting how oceanic reef systems will be affected by climate change.
... The isolation of CKI reefs compared to other Australian reefs has also been demonstrated with Veron (1990) estimating that 94 days would be required for direct transport of coral propogules from Western Australia. In addition, there is no evidence that Christmas Island acts as a 'stepping stone' for the dispersal of coral to CKI (Richards and Hobbs 2014). The existence of Indonesian or South East Asian hard coral species on the reefs was also reported to be low or not reliable, primarily due to the lack of knowledge of Indonesian corals communities at the time (Veron 1990). ...
... Only four major studies of coral species diversity and distribution have been undertaken at CKI between 1879 and 1994 (Richards and Hobbs 2014). This has included collections for the British Museum in 1879 (see Veron 1990), Wood-Jones in early 1900's (see Wood-Jones 1912), Gibson-Hill in the 1940's (see Wells 1950) and Veron in the 1980's (see Veron 1990). ...
... However, this survey is the first to use diver operated video and point count analysis to provide a percent composition of benthic habitats at CKI. Twenty two genera were observed during the study. Previous studies have reported, 29 genera (Veron 1990) and 33 (Richards and Hobbs 2014). Given that this study was designed to assess and monitor broad level benthic community composition not to document diversity the differences in the number of genera observed in this study in relation to previous studies is comparable. ...
... Few studies deal with historical collection data themselves and only some of these refer to a marine setting, either pointing at local species extinctions or longevity of populations (e.g. Richards et al., 2008Richards et al., , 2009Hoeksema and Koh, 2009;Rainbow, 2009;Van der Meij et al., 2010;Van der Meij and Visser, 2011;Hoeksema and Wirtz, 2013;Richards and Hobbs, 2014). The present study can serve as a baseline for future studies, which is scientifically valuable since it deals with a large area that is renowned for its research and conservation efforts. ...
Based on a study of mushroom coral species of eastern Australia, a decrease in species richness can be discerned from north to south. Eastern Australia, including the Great Barrier Reef (GBR), is one of only few coral reef areas suitable for studies on large-scale latitudinal biodiversity patterns. Such patterns may help to recognize biogeographic boundaries and factors regulating biodiversity. Owing to the eastern Australian long coastline, such studies are a logistic challenge unless reliable distribution data are already available, as in museum collections. A large coral collection predominantly sampled from this area in the 1970s is present in the Museum of Tropical Queensland (MTQ). The scleractinian family Fungiidae (mushroom corals), representing about 10% of Indo-Pacific reef coral species, was selected as proxy. It was represented by 1,289 specimens belonging to 34 species with latitudinal ranges between 09°09´S and 31°28´S. The fauna of the northernmost reefs in the Gulf of Papua and the Torres Strait, and north of the Great Barrier Reef Marine Park (GBRMP), was represented by a maximum of 30 fungiids. From here a southward decline in species number was observed, down to Lord Howe Island with only one species. Together with previous records, the mushroom coral fauna of eastern Australia consists of 37 species, which is more diverse than hitherto known and similar to numbers found in the Coral Triangle. Future field surveys in the GBR should specifically target rarely known species, which are mainly small and found at depths > 25 m. In the light of global climate change, they may also show whether previously recorded species are still present and whether their latitudinal ranges have shifted, using the 1970s records as a baseline.
