Planci Outbreaks Research Articles

Marine Biodiversity of Coral Reef Fishes in Pieh Marine Recreational Park After Bleaching and Acanthaster Outbreaks

Highlight ResearchAfter bleaching disturbance and Acanthaster planci outbreaks, herbivore fishes species were dominated in MRP PiehThis explains the marine recreational activities in utilization zone MRP Pieh have no impact on reducing fish biomassAfter disturbance in MRP Pieh shows the coral reef fishes still endurance on bleaching event, and Acanthaster planci outbreak after disturbance in MRP Pieh shows the coral reef fishes still endurance on bleaching event and Acanthaster planci outbreak. However, the composition of corallivorous has decreased but has been an increase in herbivorous and carnivorous fish populationsAbstractPieh MRP encountered non-anthropogenic phenomena, precisely massive coral bleaching in 2016, 2017, and massive predators from Acanthaster planci outbreaks in 2018. This study aimed to understand the pattern of coral reef diversity in the core zone and utilization in the MRP area and compare it to non-MRPS locations that accept the same non-anthropogenic pressure conditions. Coral fish sampling using a UVC is categorized into three zones: the core zone, the utilization zone, and outside the MRP area. 8 Families of coral reef fishes were counted based on categories of level function in ecologies and economy. Taxonomic distinctiveness estimates were calculated mathematically for each sample, including species richness and taxonomic diversity were compared among zonation area. Pearson’s Coefficient Correlation Matrix was used to measure the correlation relationship between zonation areas. There are 91 species of fish and 3002 individuals found. The richest family in the MRP Core Zone and MRP Utility Zone was Acanthuridae with 20 species and non-MRP has a lower species richness and abundance of fish communities. The dominant species in Pieh MRP was Ctenochaetus striatus with average abundant per site (21.3 ± 7.62, n = 3). Acanthuridae represents 55.98% of the total biomass in MRP-Core Zone, 63.13% in MRP-Utility Zone, and 41.55% in Non-MRP Area. This study showed the number of species and populations from corallivores fishes have decreased but has been an increase in herbivorous and carnivore diversity. The diversity indices (H’) and ENS also shows no differ significantly between zonation.

A snapshot of reef conditions in North Ari Atoll (Maldives) following the 2016 bleaching event and Acanthaster planci outbreak

Coral reefs are degrading worldwide. This study explored the benthic community structure (biotic and abiotic benthic cover and coral composition) at three islands (Rasdhoo, Maayafushi and Vihamaafaru) in the central Maldivian archipelago, 2 years after the 2016 El Nino–Southern Oscillation (ENSO) and the associated mass-bleaching events. Hence, we assessed benthic cover on the same GPS sites and depth (10m) of a subset of reefs that had been previously studied. The islands represent a range of management categories and oceanic influence. Average live coral cover in 2018 was lowest on Maayafushi reefs (0.65±0.41%), a resort island with minimal exposure to oceanic influence. At Rasdhoo, a community island with south-eastern oceanic exposure, live coral cover was 14.70±3.20% and 90% of the colonies were less than 20cm in diameter. At Vihamaafaru, an uninhabited island with oceanic exposure from the west, reefs assessed had a live coral cover of 17.9±6.80%, Acropora spp. remained the dominant taxa, and 35% of colonies were 20cm or greater in diameter. This evident trend, in variation of live coral cover and size of the coral colonies, among the three island settings indicates the greatest potential for recovery of coral cover on reefs with more exposure to oceanic influence.

Extensive coral reef decline in Nha Trang Bay, Vietnam: Acanthaster planci outbreak: the final event in a sequence of chronic disturbances

Nha Trang Bay (NTB), located off the south-east coast of Vietnam, is a famous tropical tourist site. In the past, the bay was characterised by flourishing coral reefs but, by the end of 2019, more than 90% of the corals were gone. In addition to chronic and complex anthropogenic effects, there was an extensive outbreak of crown-of-thorns starfish (Acanthaster planci), the main natural predator of reef-building corals in the Indo-Pacific, among the remnant coral communities in NTB. By 2019, the mean abundance of A. planci in NTB reached 4.2 starfish per 100m2. Coral surveys conducted on 10 target sites over a 3-year period ending in 2019 revealed that mean coral cover decreased by 64.4% (coral loss varied from 43 to 95%). The greatest declines were in Acropora and Montipora, with 80.6 and 82.3% reductions in the coverage of these taxa respectively. The combination of nutrient enrichment and predator removal is thought to determine the extent of the outbreak of A. planci in the bay. The present trends in environmental conditions in NTB do not indicate a positive outcome for coral reef recovery in in this area in the near future.

Acoustic tracking of a large predatory marine gastropod, Charonia tritonis, on the Great Barrier Reef

Crown-of-thorns starfish Acanthaster planci (COTS) outbreaks are a major cause of coral cover loss on the Great Barrier Reef (GBR), with manual culling having only localised success. The endangered giant triton snail Charonia tritonis is a natural predator of COTS, although aquarium and field observations indicate the intensity of direct predation may be inadequate to significantly mediate outbreaks. However, their mere presence can elicit a chemically induced sensory behavioural response which may suppress COTS populations when in non-outbreak status. While there is increasing knowledge of the sensory biology of both species, little is known regarding giant triton snail numbers on the GBR or about how they move and occupy space, making it difficult to determine their true zone of influence and thus their capacity to disrupt COTS behaviour. We used passive acoustic telemetry to establish short-term activity space and movement patterns of giant triton snails on the GBR. Individuals were tracked for up to 41 d, were observed to travel 234.24 m d-1, with a mean total cumulative distance travelled at night (1923.19 m) nearly double that observed during the day (1014.84 m). These distances encompass those reported for COTS (10.3 m d-1) and align with COTS nocturnal behaviour. Space utilisation distributions (UDs) revealed a mean (±SD) home range of 1179.40 ± 659.40 m2 (95% UD) and a core area of 195.68 ± 141.31 m2 (50% UD). Revealing the short-term movement patterns of this natural COTS predator within a reef environment advances knowledge of its spatial ecology and will provide information for its future conservation and for COTS management efforts.

Analysis on the outbreak period and cause of <italic>Acanthaster planci</italic> in Xisha Islands in recent 15 years

Outbreaks of the crown-of-thorns starfish Acanthaster planci have received increasing attention due to their negative impacts on coral reefs. However, outbreaks of A. planci in Chinese seas are still poorly understood. Coral reefs in the Xisha Islands (Paracel Islands), South China Sea, have been monitored during 2005 and 2019, including hard coral coverage, larval recruitment rates, density of coral reef fish and the populations of A. planci . This study aims to analyse the regular pattern regarding outbreaks of A. planci in the main islands of Xisha Islands, the causes of outbreaks of the crown-of-thorns starfish Acanthaster planci , and the solutions for controlling the outbreaks of the crown-of-thorns starfish Acanthaster planci . Monitoring coral reef ecosystems on the main islands of Xisha Islands from 2005 to 2019 showed that the cycle of Acanthaster planci outbreaks in Xisha Islands is about 15 years. These 15 years can be divided into two phases, in which the period of A. planci outbreak is about 5 years, and the recovery period of coral reefs is about 10 years. When A. planci outbreak from 2006 to 2010, the coral reef cover rate decreased from more than 60% to less than 5%. During the recovery period from 2011 to 2019, the coverage of coral reefs gradually increased to around 15%, at the same time the coral recruitment and coral reef fish increased. Further analysis showed that the occurrence of A. planci in Xisha Islands is mainly related to typhoon weather, reduction of coral reef fish, global warming and human activities. The passage of the typhoon brought a large number of nutrients, which led to the increase of plankton, leading to the survival rate of larvae of A. planci . Global warming and a decline in coral reef fish could lead to a greater percentage of the eggs of A. planci hatching and surviving. Based on 15-years monitoring data, it is highly possible that Xisha Islands are entering the next outbreak cycle of A. planci , and therefore measures should be taken to prevent the coral reef ecosystem from being destroyed again. Outbreaks of the crown-of-thorns starfish A. planci should be controlled in several ways. Direct control methods including physical removal of individual starfish and cutting individuals into multiple pieces were most often used methods to kill starfish. The most effective methods to control A. planci require injecting individual starfish with lethal chemicals, including sodium bisulfate, powdered citric acid, vinegar and thiosulfate-citrate-bile-sucrose agar (TCBS). Releasing the predator of A. planci of their different life cycle was also an effective way to control A. planci . The Giant Triton Shells ( Charonia tritonis ), the Napoleon Maori Wrasse ( Cheilinus undulatus ), Starry Puffer ( Arathron stellatus ) and Titan Trigger Fish ( Ballistoides viridescens ) were the main predator of the crown-of-thorns starfish A. planci . Moreover, regular monitoring of the starfish A. planci should be conducted in the Xisha Islands for early warning of outbreaks.

Biennium horribile: very high mortality in the reef coral Acropora millepora on the Great Barrier Reef in 2009 and 2010

Coral cover has declined markedly in the recent past in many regions of the world, including the Great Barrier Reef (GBR), Australia. The major causes of this decline are generally considered to be mortality associated with large-scale severe disturbances (i.e. catastrophic mortality), such as Acanthaster planci outbreaks, cyclones and bleaching. However, background rates of mortality (i.e. not associated with catastrophic disturbance), are rarely quantified, but without these it is difficult to assess the relative importance of these 2 types of mortality (catastrophic and background). We quantified spatial and temporal variation in catastrophic and background whole-colony mortality of the common reef coral Acropora millepora over 24 mo at 2 sites in 3 regions separated by 700 km along the GBR. The study period included 2 cyclones and a flood. Overall mortality rates were exceptionally high. Of 180 colonies tagged in April 2009, only 36 (20%) were alive in April 2011, and 68% of this mortality occurred in intervals following the 3 large disturbances. Background mortality rates were also high in the Palm Islands, where they approached 40% yr-1 compared to <5% in the Whitsunday and Keppel Islands. These results support the hypothesis that catastrophic mortality has been the major cause of coral loss in recent years on the GBR and also suggest that background rates of mortality are increasing at some locations. Projected increases in the agents of catastrophic mortality, such as cyclones and bleaching, as a result of global warming are likely to threaten the persistence of many coral species.

Informing coral reef management decisions at four U.S. National Parks in the Pacific using long‐term monitoring data

AbstractEffective management of coral reefs is challenging because of local and global stressors. Robust monitoring data are critical to managing these resources. Between 2006 and 2008, the Pacific Island Network Inventory and Monitoring Program of the U.S. National Park Service implemented monitoring protocols at four national parks in Hawai'i (Kaloko‐Honokōhau National Historical Park [KAHO], Kalaupapa National Historical Park [KALA]), Guam (War in the Pacific National Historical Park [WAPA]), and American Samoa (National Park of American Samoa [NPSA]). Benthic marine community, marine fish, and land‐based surface and groundwater quality monitoring protocols used a split‐panel sampling design to collect data on ecosystem “vital signs” and processes. Vital signs included coral species richness, percent coverage of benthic community types, fish abundance and biomass, rugosity, and a suite of surface and groundwater quality parameters. Data on key processes included top‐down (e.g., fish trophic structure, bleaching, and disease) and bottom‐up (e.g., coral larval settlement, turbidity, pH, temperature, nitrogen, phosphorus, salinity, groundwater levels) controls. The importance of these monitoring data is highlighted in four case studies that described how the information was used to manage a diverse array of issues at the parks. First, coral reef areas vulnerable to Acanthaster planci (crown‐of‐thorns sea star) outbreaks at NPSA and WAPA were identified to determine whether, and where, to focus culling efforts. Second, data were used at KALA to delineate zones with high fish biomass that were sensitive to fishing activities and warranted increased management. Third, coral settlement data at KALA identified sensitive regions within the park. Fourth, land‐based surface water quality and groundwater dynamics monitoring data at KAHO were used to support management actions that mitigate land‐based threats to park coral reefs. Advantages of the monitoring program included the split‐panel sampling design, which provided a more complete picture of the resources with statistically robust data, and the efficacy of colocating and covisiting sites for multiple protocols. The case studies demonstrated the usefulness of these data in the short term. In the long term, these data will continue to yield significant information about ecosystem responses to anthropogenic impacts and natural events, vital to park planning processes.

Larval starvation to satiation: influence of nutrient regime on the success of Acanthaster planci.

High density populations of the crown-of-thorns seastar, Acanthaster planci, are a major contributor to the decline of coral reefs, however the causes behind periodic outbreaks of this species are not understood. The enhanced nutrients hypothesis posits that pulses of enhanced larval food in eutrophic waters facilitate metamorphic success with a flow-on effect for population growth. The larval resilience hypothesis suggests that A. planci larvae naturally thrive in tropical oligotrophic waters. Both hypotheses remain to be tested empirically. We raised A. planci larvae in a range of food regimes from starvation (no food) to satiation (excess food). Algal cell concentration and chlorophyll levels were used to reflect phytoplankton conditions in nature for oligotrophic waters (0-100 cells ml-1; 0-0.01 μg chl a L-1), natural background levels of nutrients on the Great Barrier Reef (GBR) (1,000-10,000 cells ml-1; 0.1-1.0 μg chl a L-1), and enhanced eutrophic conditions following runoff events (100,000 cells ml-1; 10 μg chl a L-1). We determine how these food levels affected larval growth and survival, and the metamorphic link between larval experience and juvenile quality (size) in experiments where food ration per larvae was carefully controlled. Phytoplankton levels of 1 μg chl a L-1, close to background levels for some reefs on the GBR and following flood events, were optimal for larval success. Development was less successful above and below this food treatment. Enhanced larval performance at 1 μg chl a L-1 provides empirical support for the enhanced nutrients hypothesis, but up to a limit, and emphasizes the need for appropriate mitigation strategies to reduce eutrophication and the consequent risk of A. planci outbreaks.

The occurrence of an Acanthaster planci outbreak in Ari Atoll, Maldives

The corallivorous crown-of-thorns starfish Acanthaster planci (COTS) is recognized as a major cause of coral reef degradation throughout much of the Indo-Pacific region (Fabricius 2013). In this study, we report a localised outbreak of COTS at Mama Ghiri, Ari Atoll, Republic of Maldives in June 2014 (3°44′40′′ N; 72°49′13′′ E) (Fig. 1a-c). Belt transects (approximately 9×100 m) were used to record COTS density in the shallows (0–5m depth). An average density of 120±51 COTS per transect (mean ± SD; n=6), with a maximum of 222, was recorded around Mama Ghiri. Moreover, coral mortality of approximately 70 % including complete or partial death of nearly 100 % of tabular Acropora (mainly belonging to the species A. cytherea, A. clathrata, and A. hyacinthus), was estimated (Fig. 1c). These data are comparable with those of COTS outbreaks recently reported in other Indo-Pacific regions (Baird et al. 2013). Although A. planci outbreaks were previously observed in the Maldives (Ciarapica and Passeri 1993), this event was more intense in terms of COTS density. As in many other parts of the world, Maldivian reefs are subjected to increasing pressure from natural and direct anthropogenic disturbances (Jaleel 2013). Considering that A. planci outbreaks may represent a significant threat to coral reef health and biodiversity, we stress the urgent need to explore other Maldivian reefs to document the extent of this phenomenon and its effect on corals and their associated fauna.

Osmotic shock as alternative method to control Acanthaster planci

Objective: To test six osmotic stressors as alternative methods to control Acanthaster planci (A. planci) outbreaks by exploiting their incapacity to tolerate drastic changes in osmolarity. Finding more effective ways to control A. planci outbreaks is one of the most immediate and effective ways by which to reverse rapid declines in the abundance of live coral cover in the Indo-Pacific. Methods: A total of 10 mL of each of the following chemicals: sodium chloride, ethylenediaminetetraacetic acid, sodium carbonate, sodium cholate, sodium deoxycholate, urea and mannitol were injected into individual healthy sea stars to examine which chemicals induced disease and death. Results: Four out of six chemicals used in this study induced disease. Sodium chloride, sodium cholate, sodium deoxycholate and ethylenediaminetetraacetic acid are capable of inducing death in injected sea stars offering an alternative option to control A. planci outbreaks. Conclusions: Hyperosmotic stress is a viable alternative to control A. planci outbreaks as massive cell death results when acute hypertonicity exceeds a certain level.

Interspecific transmission and recovery of TCBS-induced disease between Acanthaster planci and Linckia guildingi

The susceptibility of the coral-feeding crown-of-thorns starfish Acanthaster planci to disease may provide an avenue with which to effectively control population outbreaks that have caused severe and widespread coral loss in the Indo-Pacific. Injecting thiosulfate-citrate-bile-sucrose (TCBS) agar into A. planci tissues induced a disease characterized by dermal lesions, loss of skin turgor, collapsed spines, and accumulation of mucus on spine tips. Moreover, the symptoms (and presumably the agent) of this disease would spread rapidly intraspecifically, but interspecific transmission (to other species of echinoderms) is yet to be examined. Vibrio rotiferianus, which was previously reported as a pathogen isolated from lesions of experimentally infected A. planci, was also recovered from Linckia guildingi lesions after several days of direct contact with diseased A. planci, demonstrating disease transmission. However, all L. guildingi fully recovered after 31 ± 16 d. Further studies are in progress to understand the ecology of Vibrio infection in A. planci and the potential transmission risk to corals, fishes, and other echinoderms to evaluate whether injections of TCBS could be a viable tool for controlling A. planci outbreaks.

Acanthaster planci Outbreak: Decline in Coral Health, Coral Size Structure Modification and Consequences for Obligate Decapod Assemblages

Although benthic motile invertebrate communities encompass the vast majority of coral reef diversity, their response to habitat modification has been poorly studied. A variety of benthic species, particularly decapods, provide benefits to their coral host enabling them to cope with environmental stressors, and as a result benefit the overall diversity of coral-associated species. However, little is known about how invertebrate assemblages associated with corals will be affected by global perturbations, (either directly or indirectly via their coral host) or their consequences for ecosystem resilience. Analysis of a ten year dataset reveals that the greatest perturbation at Moorea over this time was an outbreak of the corallivorous sea star Acanthaster planci from 2006 to 2009 impacting habitat health, availability and size structure of Pocillopora spp. populations and highlights a positive relationship between coral head size and survival. We then present the results of a mensurative study in 2009 conducted at the end of the perturbation (A. planci outbreak) describing how coral-decapod communities change with percent coral mortality for a selected coral species, Pocillopora eydouxi. The loss of coral tissue as a consequence of A. planci consumption led to an increase in rarefied total species diversity, but caused drastic modifications in community composition driven by a shift from coral obligate to non-obligate decapod species. Our study highlights that larger corals left with live tissue in 2009, formed a restricted habitat where coral obligate decapods, including mutualists, could subsist. We conclude that the size structure of Pocillopora populations at the time of an A. planci outbreak may greatly condition the magnitude of coral mortality as well as the persistence of local populations of obligate decapods.

There's No Place Like Home: Crown-of-Thorns Outbreaks in the Central Pacific Are Regionally Derived and Independent Events

One of the most significant biological disturbances on a tropical coral reef is a population outbreak of the fecund, corallivorous crown-of-thorns sea star, Acanthaster planci. Although the factors that trigger an initial outbreak may vary, successive outbreaks within and across regions are assumed to spread via the planktonic larvae released from a primary outbreak. This secondary outbreak hypothesis is predominantly based on the high dispersal potential of A. planci and the assertion that outbreak populations (a rogue subset of the larger population) are genetically more similar to each other than they are to low-density non-outbreak populations. Here we use molecular techniques to evaluate the spatial scale at which A. planci outbreaks can propagate via larval dispersal in the central Pacific Ocean by inferring the location and severity of gene flow restrictions from the analysis of mtDNA control region sequence (656 specimens, 17 non-outbreak and six outbreak locations, six archipelagos, and three regions). Substantial regional, archipelagic, and subarchipelagic-scale genetic structuring of A. planci populations indicate that larvae rarely realize their dispersal potential and outbreaks in the central Pacific do not spread across the expanses of open ocean. On a finer scale, genetic partitioning was detected within two of three islands with multiple sampling sites. The finest spatial structure was detected at Pearl & Hermes Atoll, between the lagoon and forereef habitats (<10 km). Despite using a genetic marker capable of revealing subtle partitioning, we found no evidence that outbreaks were a rogue genetic subset of a greater population. Overall, outbreaks that occur at similar times across population partitions are genetically independent and likely due to nutrient inputs and similar climatic and ecological conditions that conspire to fuel plankton blooms.

Acanthaster planci preying on soft corals in southern Japan

The crown-of-thorns starfish Acanthaster planci is well known as a destructive predator on shallow water Scleractinia, and in particular Acropora spp. (Pratchett 2007). Outbreaks of Acanthaster planci have caused serious damage to coral reefs. However, it is less well-known that the crown-of-thorns does occasionally prey upon other benthic cnidarians (e.g. zoanthids in Obuchi and Reimer 2011). In October 2011, we observed A. planci preying on soft corals, primarily from the genera Lobophytum and Sarcophyton, at the coast of Ei-cho Town, Kagoshima. The southern Satsuma Peninsula coast has experienced a severe outbreak of A. planci since 2007 (Ministry of the Environment 2008), and it was noted that at the dive site at Ei-cho that there was no live coral cover but many dead scleractinians covered with algae. Many individuals were observed exclusively on soft coral colonies (Fig. 1). The individuals were fully grown, approximately 30-40 cm in diameter. It has previously been observed that in the absence of favored scleractinian prey that A. planci will prey upon soft corals, with reports from Guam (Chesher 1969) and Australia (Laxton 1974), although reports are scarce. De’ath and Moran (1998) theorized that such a situation is most likely to occur at the end of A. planci outbreaks, and given the timing of the A. planci outbreak, the lack of live Scleractinia observed and the presence of recently (e.g. within past 1-2 years) dead corals, this is a likely explanation for the unusual feeding behavior of A. planci in Ei-cho. With the scleractinian community of southern Satsuma already devastated, it appears the remaining benthic soft corals are becoming the next victims of the A. planci outbreak, and continued monitoring should assess if the starfish then move on to decimate the only remaining benthic cnidarians, the sea anemones (Actiniaria). Continued observations could demonstrate if A. planci Acanthaster planci preying on soft corals in southern Japan

Associational refuges among corals mediate impacts of a crown-of-thorns starfish Acanthaster planci outbreak

Interactions among coral populations can moderate the impact of coral predator outbreaks, enhancing community resilience and recovery. This study used predator-exclusion cages and neighbour removals in a field experiment to test how indirect interactions between populations of three coral taxa, Acropora, Pocillopora, and Porites, influenced their survival during an outbreak of the crown-of-thorns starfish, Acanthaster planci, in Moorea, French Polynesia. High densities of corals enhanced survival by generating associational refuges: physical structures that impeded Acanthaster and protected corals, and by simple density-dependent prey dilution that reduced predation rates. Acanthaster showed feeding preferences, resulting in varying intensities of predation on corals, which (1) influenced the type and strength of the associational refuge among corals and (2) resulted in significant loss of the competitive dominants to the benefit of the competitive inferiors. The result was a set of indirect positive interactions (IPIs) that prevented Acanthaster from eradicating Acropora and may have enhanced Porites, a relatively weak competitor among corals. IPIs probably play a key role in many ecosystems, especially in coral reefs in which corals act as engineer species, to reduce impacts of perturbations and enhance community resilience. This study illustrates the importance of IPIs in community regulation with a new conceptual model.

Three lines of evidence to link outbreaks of the crown-of-thorns seastar Acanthaster planci to the release of larval food limitation

Population outbreaks of the coral-eating crown-of-thorns seastar, Acanthaster planci, continue to kill more coral on Indo-Pacific coral reefs than other disturbances, but the causes of these outbreaks have not been resolved. In this study, we combine (1) results from laboratory experiments where larvae were reared on natural phytoplankton, (2) large-scale and long-term field data of river floods, chlorophyll concentrations and A. planci outbreaks on the Great Barrier Reef (GBR), and (3) results from A. planci—coral population model simulations that investigated the relationship between the frequency of outbreaks and larval food availability. The experiments show that the odds of A. planci larvae completing development increases ~8-fold with every doubling of chlorophyll concentrations up to 3 μg l−1. Field data and the population model show that river floods and regional differences in phytoplankton availability are strongly related to spatial and temporal patterns in A. planci outbreaks on the GBR. The model also shows that, given plausible historic increases in river nutrient loads over the last 200 years, the frequency of A. planci outbreaks on the GBR has likely increased from one in 50–80 years to one every 15 years, and that current coral cover of reefs in the central GBR may be 30–40% of its potential value. This study adds new and strong empirical support to the hypothesis that primary A. planci outbreaks are predominantly controlled by phytoplankton availability.

Acanthaster planci outbreaks in Vanuatu coincide with ocean productivity, furthering trends throughout the pacific ocean

This study identifies linkages between regional ocean productivity and the emergence of large Acanthaster planci starfish populations in Vanuatu. Positive correlations were found between wind stress, chlorophyll-a, and upwelling during January–February 2009, corresponding with coral-eating starfish occurrences. Further, temporal associations have existed between monthly wind stress and upwelling since 2000, and were predictors of past starfish events. Links between starfish emergence and oceanographic features are discussed, drawing upon evidence from other asteroid echinoderms. High regional productivity associated with anomalous oceanographic conditions in Vanuatu, and globally, can be used as early warning indicators of probable, future starfish emergence to aid the foundation and success of local management efforts.

The transition zone chlorophyll front can trigger Acanthaster planci outbreaks in the Pacific Ocean: Historical confirmation

We hypothesize that the North Pacific transition zone chlorophyll front (TZCF) can episodically deliver enhanced phytoplankton levels that are linked to the emergence of adult populations of the coral eating starfish Acanthaster planci. In some years, the seasonally migrating TZCF bathes the northwest Hawaiian Islands with chlorophyll-a rich waters during the winter months that coincide with peak starfish spawning and provide ideal conditions for A. planci larval survival. We found significant relationships between starfish populations in the North Pacific and the southernmost latitude of the TZCF, chlorophyll-a concentrations, sea surface temperature, and Ekman transport indices since 1967. We propose that TZCF-triggered primary outbreaks are followed by secondary outbreaks throughout the region, in accordance with the surface currents and separated by a sequential time lag. Our historical confirmation suggests outbreaks are predictable, which has immediate coral reef conservation and management consequences.

Recovery patterns of corals at Shabror Umm Gam’ar, Hurghada, Red Sea, Egypt, after the 1998 outbreak of Acanthaster planci

Recovery patterns of corals were estimated after the Crown-of-thorns Starfish Acanthaster planci outbreak in 1998 at Shabror Umm Gam’ar, Hurghada, Egyptian Red Sea. The significance of using linear extrapolation was tested at ten sites by comparison with the actual average yearly recovery rates. A total of 15 permanent transects, each 10 m long, was monitored at 10 and 12 m depths at Shabror Umm Gam’ar for three years and the recovery rates were estimated by linear extrapolation. Ten other selected sites around Hurghada were monitored annually for nine years after the complete cessation of severe anchor damage. The recovery rates were estimated both by the actual annual recovery rate and by linear extrapolation. The recovery rate estimated by linear extrapolation did not differ significantly from the recovery rate of stony corals in the ten selected sites. However, an error of +7.69% to +17.5% increase in the extrapolated recovery rate exists and should be considered when handling the extrapolated recovery patterns of corals. Stony corals were characterised by having an extrapolated slow recovery time of 64.9 years in spite of the fast recovery rate (0.67% cover/year), and this is virtually due to the substantial devastation caused by A. planci. By contrast, soft corals were characterised by having a fast recovery time (RT) and recovery rate (RR) as they are not preferred prey of the Crown-of-thorns Starfish. The correlation coefficient is negative between recovery time (RT) and recovery rate (RR), strong between RT and cover required for complete recovery (CR), and weak between CR and RR. Diversity had an estimated fast recovery time (RT) of 4.3 years, indicating that the space cleared by A. planci was utilized by a high number of species (high diversity) having a smaller size (low percent cover).

Detecting the effects of natural disturbances on coral assemblages in French Polynesia: A decade survey at multiple scales

Coral reefs in French Polynesia, just like many others throughout the world, have been subjected to several natural disturbances including 15 cyclones, seven major bleaching events, and several Acanthaster planci outbreaks since the 1980s. In order to document the effects of these perturbations on coral assemblages, we initiated a long-term monitoring program that extended over both local and regional scales. Coral cover was quantified at 20 sites situated on the outer reef slope of 13 islands. The results from the first decade (1992-2002) are analyzed and the adequacy of our approach is discussed in the context of identifying potential indicators of coral reef health. Among 13 islands in French Polynesia, only two were unaffected by natural disturbances. We found important local and regional variation in the impacts of coral bleaching and cyclones, and three major temporal trends were distinguished: 1) 10 sites where coral cover decreased in relation to the occurrence of major disturbances; 2) nine sites where coral cover increased, despite the occurrence of disturbances affecting seven of them; and 3) a site where no significant variation in coral cover was found. The responses to perturbations were different among coral genera: Acropora species were particularly susceptible to bleaching events, whereas physical damages induced by cyclones concerned mainly branching species of Acropora and Pocillopora. Thus, monitoring surveys could be improved by selecting different and complementary indicators (one on the variation in diversity, one estimating changes in the abundance/cover, and one estimating the potential for recovery), by integrating several spatial scales, and by including at least the most informative species. High frequency recordings of environmental parameters (e.g. sea surface temperature) may be also a complementary tools for identifying causal relationships between changes in coral reef community structure and the factors causing the changes.