Two time losers: selective feeding by crown-of-thorns starfish on corals most affected by successive coral-bleaching episodes on western Australian coral reefs (original) (raw)
Related papers
Crown-of-thorns starfish impede the recovery potential of coral reefs following bleaching
Marine Biology, 2019
High densities of the corallivorous crown-of-thorns starfish (CoTS; Acanthaster sp.) have occurred throughout the Indo-Pacific often resulting in widespread coral loss. Whilst CoTS have previously been recorded at Barrow and the Montebello Islands, in the Pilbara offshore bioregion of northwestern Australia, their densities were relatively low. Outbreak densities of CoTS have been described as the level at which the rate of coral consumption by the starfish is equal to or greater than rate at which the coral grows. In 2014, we recorded densities as high as 320 ± 58 CoTS ha −1 in the region which is well above recognised outbreak densities. Whilst there is little terrestrial runoff and agriculture in the Pilbara region, both temperature and chlorophyll-α levels appear to be sufficient to allow a high degree of CoTS larval success in most years. The region was subjected to anomalously high water temperatures during the summers of 2010-2011 and particularly 2012-2013 which resulted in the mortality of almost 70% of live coral. We hypothesise that the high densities of CoTS observed are a result of CoTS responding to a reduced food supply and aggregating around the remaining live coral resulting in outbreak densities rather than a significant increase in the number of CoTS in the area. The small amount of remaining live coral is concentrated in a few areas and this, combined with high densities of CoTS in these areas, suggest that CoTS represent a significant threat to the recovery of the coral communities of the region.
Culling corallivores improves short-term coral recovery under bleaching scenarios
Nature Communications
Management of coral predators, corallivores, is recommended to improve coral cover on tropical coral reefs under projected increasing levels of accumulated thermal stress, but whether corallivore management can improve coral cover, which is necessary for large-scale operationalisation, remains equivocal. Here, using a multispecies ecosystem model, we investigate intensive management of an invertebrate corallivore, the Crown-of-Thorns Starfish (Acanthaster cf. solaris), and show that culling could improve coral cover at sub-reef spatial scales, but efficacy varied substantially within and among reefs. Simulated thermal stress events attenuated management-derived coral cover improvements and was dependent on the level of accumulated thermal stress, the thermal sensitivity of coral communities and the rate of corallivore recruitment at fine spatial scales. Corallivore management was most effective when accumulated thermal stress was low, coral communities were less sensitive to heat st...
Refugia under threat: Mass bleaching of coral assemblages in high‐latitude eastern Australia
Global Change Biology
Environmental anomalies that trigger adverse physiological responses and mortality are occurring with increasing frequency due to climate change. At species' range peripheries, environmental anomalies are particularly concerning because species often exist at their environmental tolerance limits and may not be able to migrate to escape unfavourable conditions. Here, we investigated the bleaching response and mortality of 14 coral genera across high-latitude eastern Australia during a global heat stress event in 2016. We evaluated whether the severity of assemblage-scale and genus-level bleaching responses was associated with cumulative heat stress and/or local environmental history, including long-term mean temperatures during the hottest month of each year (SSTLTMAX), and annual fluctuations in water temperature (SSTVAR) and solar irradiance (PARZVAR). The most severely-bleached genera included species that were either endemic to the region (Pocillopora aliciae) or rare in the tropics (e.g. Porites heronensis). Pocillopora spp., in particular, showed high rates of immediate mortality. Bleaching severity of Pocillopora was high where SSTLTMAX was low or PARZVAR was high, whereas bleaching severity of Porites was directly associated with cumulative heat stress. While many tropical Acropora species are extremely vulnerable to bleaching, the Acropora species common at high latitudes, such as A. glauca and A. solitaryensis, showed little incidence of bleaching and immediate mortality. Two other regionally-abundant genera, Goniastrea and Turbinaria, were also largely unaffected by the thermal anomaly. The severity of assemblage-scale bleaching responses was poorly explained by the environmental parameters we examined. Instead, the severity of assemblage-scale bleaching was associated with local differences in species abundance and taxon-specific bleaching responses. The marked taxonomic disparity in bleaching severity, coupled with high mortality of high-latitude endemics, point to climate-driven simplification of assemblage structures and progressive homogenisation of reef functions at these high-latitude locations.
PLoS ONE, 2012
Outbreaks of the coral-killing seastar Acanthaster planci are intense disturbances that can decimate coral reefs. These events consist of the emergence of large swarms of the predatory seastar that feed on reef-building corals, often leading to widespread devastation of coral populations. While cyclic occurrences of such outbreaks are reported from many tropical reefs throughout the Indo-Pacific, their causes are hotly debated, and the spatio-temporal dynamics of the outbreaks and impacts to reef communities remain unclear. Based on observations of a recent event around the island of Moorea, French Polynesia, we show that Acanthaster outbreaks are methodic, slow-paced, and diffusive biological disturbances. Acanthaster outbreaks on insular reef systems like Moorea's appear to originate from restricted areas confined to the ocean-exposed base of reefs. Elevated Acanthaster densities then progressively spread to adjacent and shallower locations by migrations of seastars in aggregative waves that eventually affect the entire reef system. The directional migration across reefs appears to be a search for prey as reef portions affected by dense seastar aggregations are rapidly depleted of living corals and subsequently left behind. Coral decline on impacted reefs occurs by the sequential consumption of species in the order of Acanthaster feeding preferences. Acanthaster outbreaks thus result in predictable alteration of the coral community structure. The outbreak we report here is among the most intense and devastating ever reported. Using a hierarchical, multi-scale approach, we also show how sessile benthic communities and resident coral-feeding fish assemblages were subsequently affected by the decline of corals. By elucidating the processes involved in an Acanthaster outbreak, our study contributes to comprehending this widespread disturbance and should thus benefit targeted management actions for coral reef ecosystems. Citation: Kayal M, Vercelloni J, Lison de Loma T, Bosserelle P, Chancerelle Y, et al. (2012) Predator Crown-of-Thorns Starfish (Acanthaster planci) Outbreak, Mass
Coral community response to bleaching on a highly disturbed reef
Scientific Reports, 2016
While many studies of coral bleaching report on broad, regional scale responses, fewer examine variation in susceptibility among coral taxa and changes in community structure, before, during and after bleaching on individual reefs. Here we report in detail on the response to bleaching by a coral community on a highly disturbed reef site south of mainland Singapore before, during and after a major thermal anomaly in 2010. To estimate the capacity for resistance to thermal stress, we report on: a) overall bleaching severity during and after the event, b) differences in bleaching susceptibility among taxa during the event, and c) changes in coral community structure one year before and after bleaching. Approximately two thirds of colonies bleached, however, post-bleaching recovery was quite rapid and, importantly, coral taxa that are usually highly susceptible were relatively unaffected. Although total coral cover declined, there was no significant change in coral taxonomic community structure before and after bleaching. Several factors may have contributed to the overall high resistance of corals at this site including Symbiodinium affiliation, turbidity and heterotrophy. Our results suggest that, despite experiencing chronic anthropogenic disturbances, turbid shallow reef communities may be remarkably resilient to acute thermal stress. Coral bleaching refers to the paling or whitening of shallow water reef corals that results from the loss of symbiotic dinoflagellate algae (known as zooxanthellae) or their algal pigments 1. Bleaching is a stress response, leading to sub-lethal damage and/or partial or whole colony mortality for the coral host, and can be induced by several factors 1. Large-scale bleaching episodes, however, are strongly correlated with elevated sea temperatures and may be exacerbated by high irradiance 2. Major bleaching events driven by thermal anomalies have caused widespread and catastrophic mortality of corals and are considered one of the main drivers of global reef degradation 3. Bleaching severity, at the level of the coral assemblage, varies substantially as a consequence of the severity of thermal stress 4 , the thermal history of the site e.g. 5 , local environmental factors that affect irradiance (such as cloud cover and turbidity) 6,7 ,the type and diversity of symbiotic algae present in the coral host tissue 8,9 and the taxonomic community structure of the coral assemblage 10. Of these factors, the role of the symbiont is probably one of the most intensively researched areas in climate change studies of corals, because certain zooxanthellae types are associated with greater thermal tolerance 9. The taxonomic composition of the coral assemblage is another strong driver of variation in bleaching at a reef scale 10. This is because consistent differences have been documented in the susceptibility of coral taxa to bleaching 10-12 ; but see Guest et al. (2012) 13. For example, in most studies to date, branching colonies of the genera Acropora and Pocillopora have been reported to bleach much more severely relative to other growth forms and coral genera, particularly slow growing massive species 10-12. This observation has led to the widespread classification of fast growing branching species as "losers" in the face of global warming 11 , at least in the short term 14. The classification of corals as winners or losers does not, however, take into consideration the capacity for normally susceptible
Oceanography and Marine Biology, 2008
Global climate change is having devastating effects on habitat structure in coralreef ecosystems owing to extreme environmental sensitivities and consequent bleaching of reefbuilding scleractinian corals. coral bleaching frequently causes immediate loss of live coral and may lead to longer-term declines in topographic complexity. This review identifies coral cover and topographic complexity as critical and distinct components of coral-reef habitats that shape communities of coral-reef fishes. coral loss has the greatest and most immediate effect on fishes that depend on live corals for food or shelter, and many such fishes may face considerable risk of extinction with increasing frequency and severity of bleaching. coral loss may also have longer-term consequences for fishes that require live corals at settlement, which are compounded by devastating effects of declining topographic complexity. Topographic complexity moderates major biotic factors, such as predation and competition, contributing to the high diversity of fishes on coral reefs. Many coral-reef fishes that do not depend on live coral are nonetheless dependent on the topographic complexity provided by healthy coral growth. Ecological and economic consequences of declining topographic complexity are likely to be substantial compared with selective effects of coral loss but both coral cover and topographic complexity must be recognised as a critical component of habitat structure and managed accordingly. urgent action on the fundamental causes of climate change and appropriate management of critical elements of habitat structure (coral cover and topographic complexity) are key to ensuring long-term persistence of coral-reef fishes. 65742_C006.indd 252 2/4/08 10:01:58 AM 253 EFFEcTs oF cliMATE-iNDucED coRAl blEAchiNG oN coRAl-REEF FishEs increasingly exceed thermal tolerances of corals, resulting in more frequent and severe episodes of coral bleaching (hoegh-Guldberg 1999, stone et al. 1999). While linkages between global climate change, thermal stress and coral bleaching have been well studied and are becoming better understood (reviewed by b.E. brown 1997, Douglas 2003, hughes et al. 2003, hoegh-Guldberg 2004), the ecological ramifications of climate-induced coral bleaching for fishes and other coral-reef organisms are only just beginning to become apparent (e.g., G.P. Jones et al. 2004, Aronson & Precht 2006, Graham et al. 2006). corals (especially, reefbuilding scleractinian corals) are fundamental to the functioning of coral-reef ecosystems, contributing to primary production, nutrient recycling, and reef growth (hoegh-Guldberg 2004, Wild et al. 2004). scleractinian corals are also the primary habitat-forming species (foundation species; Dayton 1972) in coral-reef habitats (e.g., connell et al. 1997). Removal or destruction of corals will therefore profoundly alter the structure and dynamics of coral-reef habitats, with potentially significant effects on highly diverse assemblages of species that associate with coral reefs (e.g., Wilson et al. 2006, Munday et al. 2007, Pratchett et al. 2007). This review considers the effects of climate-induced coral bleaching on coral-reef fishes, which are an important component of coralreef ecosystems, in terms of both their economic value (Westmacott et al. 2000a) and ecological function (bellwood et al. 2004, hughes et al. 2007). More than one quarter of known fish species are strongly associated with coral reefs (spalding et al. 2001) and will be increasingly affected by ongoing degradation of coral-reef habitats caused or exacerbated by climate-induced coral bleaching (G.P. Jones et al. 2004, Munday 2004a, Pratchett et al. 2006). This review provides the first comprehensive assessment of effects of climate-induced coral bleaching on coral-reef fishes. climate-induced coral bleaching has had major effects on the biological and physical structure of coral-reef habitats in recent years (mostly since 1998; e.g., Wilkinson 2000a,b) and numerous studies have documented concomitant changes in the abundance, diversity or composition of fishes (
Oceanography and Marine Biology - An Annual Review, 2008
Global climate change is having devastating effects on habitat structure in coralreef ecosystems owing to extreme environmental sensitivities and consequent bleaching of reefbuilding scleractinian corals. coral bleaching frequently causes immediate loss of live coral and may lead to longer-term declines in topographic complexity. This review identifies coral cover and topographic complexity as critical and distinct components of coral-reef habitats that shape communities of coral-reef fishes. coral loss has the greatest and most immediate effect on fishes that depend on live corals for food or shelter, and many such fishes may face considerable risk of extinction with increasing frequency and severity of bleaching. coral loss may also have longer-term consequences for fishes that require live corals at settlement, which are compounded by devastating effects of declining topographic complexity. Topographic complexity moderates major biotic factors, such as predation and competition, contributing to the high diversity of fishes on coral reefs. Many coral-reef fishes that do not depend on live coral are nonetheless dependent on the topographic complexity provided by healthy coral growth. Ecological and economic consequences of declining topographic complexity are likely to be substantial compared with selective effects of coral loss but both coral cover and topographic complexity must be recognised as a critical component of habitat structure and managed accordingly. urgent action on the fundamental causes of climate change and appropriate management of critical elements of habitat structure (coral cover and topographic complexity) are key to ensuring long-term persistence of coral-reef fishes.
Global Change Biology, 2006
Increased frequency of disturbances and anthropogenic activities are predicted to have a devastating impact on coral reefs that will ultimately change the composition of reef associated fish communities. We reviewed and analysed studies that document the effects of disturbance-mediated coral loss on coral reef fishes. Meta-analysis of 17 independent studies revealed that 62% of fish species declined in abundance within 3 years of disturbances that resulted in 410% decline in coral cover. Abundances of species reliant on live coral for food and shelter consistently declined during this time frame, while abundance of some species that feed on invertebrates, algae and/or detritus increased. The response of species, particularly those expected to benefit from the immediate loss of coral, is, however, variable and is attributed to erratic replenishment of stocks, ecological versatility of species and sublethal responses, such as changes in growth, body condition and feeding rates. The diversity of fish communities was found to be negatively and linearly correlated to disturbance-mediated coral loss. Coral loss 420% typically resulted in a decline in species richness of fish communities, although diversity may initially increase following small declines in coral cover from high coverage. Disturbances that result in an immediate loss of habitat complexity (e.g. severe tropical storms), have a greater impact on fishes from all trophic levels, compared with disturbances that kill corals, but leave the reef framework intact (e.g. coral bleaching and outbreaks of Acanthaster planci). This is most evident among small bodied species and suggests the long-term consequences of coral loss through coral bleaching and crown-ofthorn starfish outbreaks may be much more substantial than the short-term effects currently documented.
The cumulative impact of annual coral bleaching can turn some coral species winners into losers
Global Change Biology, 2014
Mass coral bleaching events caused by elevated seawater temperatures result in extensive coral loss throughout the tropics, and are projected to increase in frequency and severity. If bleaching becomes an annual event later in this century, more than 90% of coral reefs worldwide may be at risk of long-term degradation. While corals can recover from single isolated bleaching and can acclimate to recurring bleaching events that are separated by multiple years, it is currently unknown if and how they will survive and possibly acclimatize to annual coral bleaching. Here, we demonstrate for the first time that annual coral bleaching can dramatically alter thermal tolerance in Caribbean corals. We found that high coral energy reserves and changes in the dominant algal endosymbiont type (Symbiodinium spp.) facilitated rapid acclimation in Porites divaricata, whereas low energy reserves and a lack of algal phenotypic plasticity significantly increased susceptibility in Porites astreoides to bleaching the following year. Phenotypic plasticity in the dominant endosymbiont type of Orbicella faveolata did not prevent repeat bleaching, but may have facilitated rapid recovery. Thus, coral holobiont response to an isolated single bleaching event is not an accurate predictor of its response to bleaching the following year. Rather, the cumulative impact of annual coral bleaching can turn some coral species 'winners' into 'losers', and can also facilitate acclimation and turn some coral species 'losers' into 'winners'. Overall, these findings indicate that cumulative impact of annual coral bleaching could result in some species becoming increasingly susceptible to bleaching and face a long-term decline, while phenotypically plastic coral species will acclimatize and persist. Thus, annual coral bleaching and recovery could contribute to the selective loss of coral diversity as well as the overall decline of coral reefs in the Caribbean.