Recent disturbances augment community shifts in coral assemblages in Moorea, French Polynesia

Coral reefs are often subject to disturbances that can cause enduring changes in community structure and abundance of coral reef organisms. In Moorea, French Polynesia, frequent disturbances between 1979 and 2003 caused marked shifts in taxonomic composition of coral assemblages. This study explores recent changes in live cover and taxonomic structure of coral communities on the north coast of Moorea, French Polynesia, to assess whether coral assemblages are recovering (returning to a previous Acropora-dominated state) or continuing to move towards an alternative community structure. Coral cover declined by 29.7% between July 2003 and March 2009, mostly due to loss of Acropora and Montipora spp. Coral mortality varied among habitats, with highest levels of coral loss on the outer reef slope (7–20 m depth). In contrast, there was limited change in coral cover within the lagoon, and coral cover actually increased on the reef crest. Observed changes in coral cover and composition correspond closely with the known feeding preferences and observed spatial patterns of Acanthaster planci L., though observed coral loss also coincided with at least one episode of coral bleaching, as well as persistent populations of the corallivorous starfish Culcita novaeguineae Muller & Troschel. While climate change poses an important and significant threat to the future structure and dynamics coral reef communities, outbreaks of A. planci remain a significant cause of coral loss in Moorea. More importantly, these recent disturbances have followed long-term shifts in the structure of coral assemblages, and the relative abundance of both Pocillopora and Porites continue to increase due to disproportionate losses of Acropora and Montipora. Moreover, Pocillopora and Porites dominate assemblages of juvenile corals, suggesting that there is limited potential for a return to an Acropora-dominated state, last recorded in 1979.     

Parrotfish predation on massive Porites on the Great Barrier Reef

Parrotfish grazing scars on coral colonies were quantified across four reef zones at Lizard Island, Northern Great Barrier Reef (GBR). The abundance of parrotfish grazing scars was highest on reef flat and crest, with massive Porites spp. colonies having more parrotfish grazing scars than all other coral species combined. Massive Porites was the only coral type positively selected for grazing by parrotfishes in all four reef zones. The density of parrotfish grazing scars on massive Porites spp., and the rate of new scar formation, was highest on the reef crest and flat, reflecting the lower massive Porites cover and higher parrotfish abundance in these habitats. Overall, it appears that parrotfish predation pressure on corals could affect the abundance of preferred coral species, especially massive Porites spp, across the reef gradient. Parrotfish predation on corals may have a more important role on the GBR reefs than previously thought.     

Coral and sea urchin assemblage structure and interrelationships in Kenyan reef lagoons

Patterns of hard coral and sea urchin assemblage structure (species richness, diversity, and abundance) were studied in Kenyan coral reef lagoons which experienced different types of human resource use. Two protected reefs (Malindi and Watamu Marine National Parks) were protected from fishing and coral collection, but exposed to heavy tourist use. One reef (Mombasa MNP) received protection from fishermen for one year and was exploited for fish and corals prior to protection and was defined as a transitional reef. Three reefs (Vipingo, Kanamai, and Diani) were unprotected and experienced heavy fishing and some coral collection. Protected and unprotected reefs were distinct in terms of their assemblage structure with the transitional reef grouping with unprotected reefs based on relative and absolute abundance of coral genera. Protected reefs had slightly higher (p<0.01) coral cover (23.6 ± 8.3 % ± S.D.) than unprotected reefs (16.7 ± 8.5), but the transitional reef had the highest coral cover (30.8 ± 6.4) which increased by 250% since measured in 1987: largely attributable to a large increase inPorites nigrescens cover. Protected reefs had higher coral species richness and diversity and a greater relative abundance ofAcropora, Montipora andGalaxea than unprotected reefs. The transitional reef had high species richness, but lower diversity due to the high dominance ofPorites. Sea urchins showed the opposite pattern with highest diversity in most unprotected reefs. Coral cover, species richness, and diversity were negatively associated with sea urchin abundance, but the relative abundance ofPorites increased with sea urchin abundance to the point wherePorites composed >90% of the coral cover at sites with the highest sea urchin abundance. Effects of coral overcollection was only likely for the genusAcropora (staghorn corals). A combination of direct and indirect effects of human resource use may reduce diversity, species richness, and abundance of corals while increasing the absolute abundance of sea urchins and the relative cover ofPorites.     

Changes in Bleaching Susceptibility among Corals Subject to Ocean Warming and Recurrent Bleaching in Moorea,French Polynesia

Background

Climate-induced coral bleaching poses a major threat to coral reef ecosystems, mostly because of the sensitivities of key habitat-forming corals to increasing temperature. However, susceptibility to bleaching varies greatly among coral genera and there are likely to be major changes in the relative abundance of different corals, even if the wholesale loss of corals does not occur for several decades. Here we document variation in bleaching susceptibility among key genera of reef-building corals in Moorea, French Polynesia, and compare bleaching incidence during mass-bleaching events documented in 1991, 1994, 2002 and 2007.

Methodology/Principal Findings

This study compared the proportion of colonies that bleached for four major genera of reef-building corals (Acropora, Montipora, Pocillopora and Porites), during each of four well-documented bleaching events from 1991 to 2007. Acropora and Montipora consistently bleached in far greater proportions (up to 98%) than Pocillopora and Porites. However, there was an apparent and sustained decline in the proportion of colonies that bleached during successive bleaching events, especially for Acropora and Montipora. In 2007, only 77% of Acropora colonies bleached compared with 98% in 1991. Temporal variation in the proportion of coral colonies bleached may be attributable to differences in environmental conditions among years. Alternately, the sustained declines in bleaching incidence among highly susceptible corals may be indicative of acclimation or adaptation.

Conclusions/Significance

Coral genera that are highly susceptible to coral bleaching, and especially Acropora and Montipora, exhibit temporal declines in their susceptibility to thermal anomalies at Moorea, French Polynesia. One possible explanation for these findings is that gradual removal of highly susceptible genotypes (through selective mortality of individuals, populations, and/or species) is producing a coral assemblage that is more resistant to sustained and ongoing ocean warming.     

Recurrent disturbances, recovery trajectories, and resilience of coral assemblages on a South Central Pacific reef

Coral reefs are increasingly threatened by various disturbances, and a critical challenge is to determine their ability for resistance and resilience. Coral assemblages in Moorea, French Polynesia, have been impacted by multiple disturbances (one cyclone and four bleaching events between 1991 and 2006). The 1991 disturbances caused large declines in coral cover (~51% to ~22%), and subsequent colonization by turf algae (~16% to ~49%), but this phase-shift from coral to algal dominance has not persisted. Instead, the composition of the coral community changed following the disturbances, notably favoring an increased cover of Porites, reduced cover of Montipora and Pocillopora, and a full return of Acropora; in this form, the reef returned to pre-disturbance coral cover within a decade. Thus, this coral assemblage is characterized by resilience in terms of coral cover, but plasticity in terms of community composition.     

广西涠洲岛造礁珊瑚种群结构的空间分布

对2007年和2008年调查的涠洲岛沿岸海域垂直海岸方向的6条主剖面上20条分断面的影像资料、样品鉴定等资料的分析,涠洲岛石珊瑚共出现10科22属46种,9个未定种;角蜂巢珊瑚属(Favites)、滨珊瑚属(Porites)、蔷薇珊瑚属(Montipora)为优势类群,其属级重要值百分比分别为25.78%、17.47%、15.11%;各主剖面珊瑚种群优势类群分布各有差异,以西南部的W2、东北部的W5的珊瑚属种为较多,均为8科13属,其石珊瑚属种分布均匀度略高;涠洲岛珊瑚分布自岸向海分为砂砾及珊瑚断枝带、石珊瑚稀疏带、石珊瑚繁盛带、柳珊瑚繁盛带4 个生物地貌带,石珊瑚分布较多的石珊瑚繁盛带主要分布于-1.39--5 m的水深范围内。石珊瑚形态组合以块状/亚块状与板块状为主要类型,覆盖程度以块状/亚块状占优。调查区受1998年的"厄尔尼诺现象"引起的全球性极高温事件和2008年1-2月的极低温气候事件及地域性不合理人类活动胁迫影响较大,枝状形态石珊瑚覆盖度、优势程度下降,已退出属种优势组合。     

Predictive Modeling of Coral Disease Distribution within a Reef System

Diseases often display complex and distinct associations with their environment due to differences in etiology, modes of transmission between hosts, and the shifting balance between pathogen virulence and host resistance. Statistical modeling has been underutilized in coral disease research to explore the spatial patterns that result from this triad of interactions. We tested the hypotheses that: 1) coral diseases show distinct associations with multiple environmental factors, 2) incorporating interactions (synergistic collinearities) among environmental variables is important when predicting coral disease spatial patterns, and 3) modeling overall coral disease prevalence (the prevalence of multiple diseases as a single proportion value) will increase predictive error relative to modeling the same diseases independently. Four coral diseases: Porites growth anomalies (PorGA), Porites tissue loss (PorTL), Porites trematodiasis (PorTrem), and Montipora white syndrome (MWS), and their interactions with 17 predictor variables were modeled using boosted regression trees (BRT) within a reef system in Hawaii. Each disease showed distinct associations with the predictors. Environmental predictors showing the strongest overall associations with the coral diseases were both biotic and abiotic. PorGA was optimally predicted by a negative association with turbidity, PorTL and MWS by declines in butterflyfish and juvenile parrotfish abundance respectively, and PorTrem by a modal relationship with Porites host cover. Incorporating interactions among predictor variables contributed to the predictive power of our models, particularly for PorTrem. Combining diseases (using overall disease prevalence as the model response), led to an average six-fold increase in cross-validation predictive deviance over modeling the diseases individually. We therefore recommend coral diseases to be modeled separately, unless known to have etiologies that respond in a similar manner to particular environmental conditions. Predictive statistical modeling can help to increase our understanding of coral disease ecology worldwide.     

Coral frameworks revisited–reefs and coral carpets in the northern Red Sea

 Coral communities were investigated in the northern Red Sea, in the Gulfs of Suez and Aqaba, for their framework building potential. Five types of coral frameworks were differentiated: Acropora reef framework, Porites reef framework, Porites carpet, faviid carpet, and Stylophora carpet. Two non-framework community types were found: the Stylophora-Acropora community, and soft coral communities. Reef frameworks show a clear ecological zonation along depth and hydrodynamic exposure gradients, with clear indicator communities for each zone. By definition, coral carpets build a framework but lack distinct zonation patterns since they grow only in areas without pronounced gradients. In the northern Red Sea they show a gradual change with depth from Porites to faviid dominance. A Stylophora carpet is restricted to shallow water in the northern Gulf of Suez. Although growth rates of carpets may be somewhat less than those of reefs, the carbonate accumulation is considered to be higher in carpet areas due to their significantly higher areal extension. In addition, reefs and carpets have different sediment retention characteristics – the carpet retains, the reef exports. The in situ fossilization potential of coral carpets is expected to be higher than that of reef frameworks. Accepted: 25 May 1999     

Herbivory versus corallivory: are parrotfish good or bad for Caribbean coral reefs?

With coral cover in decline on many Caribbean reefs, any process of coral mortality is of potential concern. While sparisomid parrotfishes are major grazers of Caribbean reefs and help control algal blooms, the fact that they also undertake corallivory has prompted some to question the rationale for their conservation. Here the weight of evidence for beneficial effects of parrotfishes, in terms of reducing algal cover and facilitating demographic processes in corals, and the deleterious effects of parrotfishes in terms of causing coral mortality and chronic stress, are reviewed. While elevated parrotfish density will likely increase the predation rate upon juvenile corals, the net effect appears to be positive in enhancing coral recruitment through removal of macroalgal competitors. Parrotfish corallivory can cause modest partial colony mortality in the most intensively grazed species of Montastraea but the generation and healing of bite scars appear to be in near equilibrium, even when coral cover is low. Whole colony mortality in adult corals can lead to complete exclusion of some delicate, lagoonal species of Porites from forereef environments but is only reported for one reef species (Porites astreoides), for one habitat (backreef), and with uncertain incidence (though likely <<10%). No deleterious effects of predation on coral growth or fecundity have been reported, though recovery of zooxanthellae after bleaching events may be retarded. The balance of evidence to date finds strong support for the herbivory role of parrotfishes in facilitating coral recruitment, growth, and fecundity. In contrast, no net deleterious effects of corallivory have been reported for reef corals. Corallivory is unlikely to constrain overall coral cover but contraints upon dwindling populations of the Montastraea annularis species complex are feasible and the role of parrotfishes as a vector of coral disease requires evaluation. However, any assertion that conservation practices should guard against protecting corallivorous parrotfishes appears to be unwarranted at this stage.     

Temporal variations of macroborers in massive Porites lobata on Moorea,French Polynesia

Massive colonies of Porites lobata on the barrier reef of Tiahura, Moorea, can be divided into four categories: living colonies, colonies consisting of 50% live coral and 50% dead skeleton, 100% dead coral and colonies which have been reduced to a basal plate. Replicate samples of each of these colony types were collected in the same vicinity of the barrier reef during October 1987. The macroborers were extracted, identified, counted and their volumes determined by displacement. Kruskal-Wallis tests showed that three different boring communities occur within these four categories of Porites colonies. Live colonies are characterised by only 3 species, the bivalve, Lithophaga laevigata; the vermetid Dendropoma maximun; and the non boring serpulid polychaete Spirobranchus. The completely dead colonies contain up to 17 boring species, with five to six individuals per 100 cm. Sipunculans are the dominant bioeroders with the most abundant species being Aspidosiphon elegans, sp A and sp B. Colonies of Porites which have been reduced to basal plates contain up to 18 boring species of which the bivalve Lithophaga hanleyana and the sipunculan Aspidosiphon sp. B are the most abundant.The cumulative volume of CaCO₃ lost by boring activity increases from 0.1 cm³ per 100 cm³ in a completely dead Porites colony to 1.4 cm³ per 100 cm³ in the residual basal plates of Porites. These can be extrapolated to minimum losses of 14.2 kg m^-3. We suggest that rates of boring increase with the time which has elapsed since the death of the colony and the dominant agents of boring also change with increasing age of the coral structure. There are significant additional losses of 5.25 kg m^-3 CaCO₃ caused by grazing echinoids and scarids.     

Regional‐scale dominance of non‐framework building corals on Caribbean reefs affects carbonate production and future reef growth

Coral cover on Caribbean reefs has declined rapidly since the early 1980's. Diseases have been a major driver, decimating communities of framework building Acropora and Orbicella coral species, and reportedly leading to the emergence of novel coral assemblages often dominated by domed and plating species of the genera Agaricia, Porites and Siderastrea. These corals were not historically important Caribbean framework builders, and typically have much smaller stature and lower calcification rates, fuelling concerns over reef carbonate production and growth potential. Using data from 75 reefs from across the Caribbean we quantify: (i) the magnitude of non‐framework building coral dominance throughout the region and (ii) the contribution of these corals to contemporary carbonate production. Our data show that live coral cover averages 18.2% across our sites and coral carbonate production 4.1 kg CaCO₃ m^?2 yr^?1. However, non‐framework building coral species dominate and are major carbonate producers at a high proportion of sites; they are more abundant than Acropora and Orbicella at 73% of sites; contribute an average 68% of the carbonate produced; and produce more than half the carbonate at 79% of sites. Coral cover and carbonate production rate are strongly correlated but, as relative abundance of non‐framework building corals increases, average carbonate production rates decline. Consequently, the use of coral cover as a predictor of carbonate budget status, without species level production rate data, needs to be treated with caution. Our findings provide compelling evidence for the Caribbean‐wide dominance of non‐framework building coral taxa, and that these species are now major regional carbonate producers. However, because these species typically have lower calcification rates, continued transitions to states dominated by non‐framework building coral species will further reduce carbonate production rates below ‘predecline’ levels, resulting in shifts towards negative carbonate budget states and reducing reef growth potential.     

The effect of substratum on the growth of Terpios,an encrusting sponge which kills corals

The effects of substratum on the growth of Terpios was demonstrated using experimental and observational data at Guam, Mariana Islands. Terpios growth was measured on live coral, reef rock, and red calcareous algae in the field. In addition, Terpios was transplanted onto live coral, air-blasted (clean) coral, reef rock, and plexiglass plates, and subsequent growth measured. Terpios grows fastest on clean substrata followed by live coral, reef rock and red calcareous algae in decreasing order. Terpios is sometimes overgrown by Montipora, Porites and red calcareous algae. Since Terpios grows fastest when living coral tissue is removed, it is not likely that Terpios ingests coral tissue as previously suggested in the literature. Instead, Terpios is probably an efficient competitor of corals for space. Terpios overgrows most hard, stable reef substrata, and the growth rate on all sample substrata is substantial. Therefore Terpios has a great potential for covering a reef and may be one of the most important causes of disturbance on some coral reefs.Contribution no. 206 from the University of Guam Marine Laboratory     

Coral reefs in a high-latitude,siliciclastic barrier island setting: reef framework and sediment production at Inhaca Island,southern Mozambique

Inhaca Island (southern Mozambique) is located in a high-latitude setting along the seaward margins of the estuarine Maputo Bay and is subject to fluctuations in temperature and salinity, and high sedimentation and turbidity levels. Coral reefs are developed sporadically along the margins of intertidal channels, but framework development is severely restricted. Coral growth is bathymetrically limited (never exceeding 6-m depth), and framework accumulation is only present in the upper 1–2 m. Massive Porites sp. produce a basic reef structure, with other coral genera (mainly Acropora sp., Favia sp., Platygyra sp., Pocillopora sp., and Montipora sp.) colonizing available substrata. Sediment samples also indicate restricted carbonate sediment production, with siliciclastics (mainly quartz) a major sediment contributor (often >90%) and carbonate grain assemblages differing from those normally associated with lower-latitude reefs. Although corals, molluscs and coralline algae (including rhodoliths) represent dominant grain constituents, Halimeda is absent and there is a low diversity (four species identified) of benthic foraminifera (mainly Amphistegina sp.). Grain associations are therefore somewhat transitional in character, comprising elements of both tropical (chlorozoan) and temperate (foramol) grain assemblages. These patterns of reef and associated carbonate production emphasize the marginal character of these reef environments, which form one end member in a broad spectrum of marginal reef systems that are now being identified in a range of both high- and low-latitude settings.     

Relative sensitivity of five Hawaiian coral species to high temperature under high-pCO2 conditions

Coral reef ecosystems are presently undergoing decline due to anthropogenic climate change. The chief detrimental factors are increased temperature and increased pCO₂. The purpose of this study was to evaluate the effect of these two stressors operating independently and in unison on the biological response of common Hawaiian reef corals. Manipulative experiments were performed using five species (Porites compressa, Pocillopora damicornis, Fungia scutaria, Montipora capitata, and Leptastrea purpurea) in a continuous-flow mesocosm system under natural sunlight conditions. Corals were grown together as a community under treatments of high temperature (2 °C above normal maximum summer temperature), high pCO₂ (twice present-day conditions), and with both factors acting in unison. Control corals were grown under present-day pCO₂ and at normal summer temperatures. Leptastrea purpurea proved to be an extremely hardy coral. No change in calcification or mortality occurred under treatments of high temperature, high pCO₂, or combined high temperature–high pCO₂. The remaining four species showed reduced calcification in the high-temperature treatment. Two species (L. purpurea and M. capitata) showed no response to increased pCO₂. Also, high pCO₂ ameliorated the negative effect of high temperature on the calcification rates of P. damicornis. Mortality was driven primarily by high temperature, with a negative synergistic effect in P. compressa only in the high-pCO₂–high-temperature treatment. Results support the observation that biological response to temperature and pCO₂ elevation is highly species-specific, so generalizations based on response of a single species might not apply to a diverse and complex coral reef community.

     

Observations of a new source of coral mortality along the Kenyan coast

In early 2002 coral mortality occurred along 600 km of coastline from Tanzania to Kenya. Astreopora, Echinopora , and Montipora species were severely affected, with Montipora being nearly eliminated from Kenyan reefs. Acropora , Platygyra , Goniopora , and massive Porites were also affected; however, Porites and Goniopora rarely died and often recovered, whereas death for most other species occurred within 2 weeks. In Echinopora and Montipora , a dull ashy tissue color and brittle skeletons characterized the early stages of this event with a mucus layer on the tissue surface in intermediate stages. Mucus and embedded debris then disappeared and surfaces were left covered in a white calcareous dust that sometimes capped a black layer. Astreopora tissues became dull and pale, and seldom produced mucus; eventually the skeleton became bare and white. Either a colorless translucent or brownish thin margin of tissue was visible between living tissue and bare skeleton, depending on species. Scanning electron micrographs of affected corals revealed the presence of fungi. Histology and staining showed that the fungi were mostly in the three genera that died from the syndrome and it may be that fungi invaded and killed corals weakened by another unidentified pathogen.     

Geographical variation in reproductive biology is obscured by the species problem: a new record of brooding in Porites cylindrica,or misidentification?

Little is known about the reproductive biology of corals from the Philippines, despite this archipelago being at the center of coral reef biodiversity. Here, we report on the reproductive biology of a branching poritid species provisionally identified as Porites cf. cylindrica in the Bolinao‐Anda reef complex (BARC), northwestern Philippines. Histological examination and ex situ planulation observations reveal P.cf. cylindrica colonies to be gonochoric brooders that release actively swimming zooxanthellate larvae. Planulation appeared to occur throughout the year and there was significant lunar periodicity in planular release. The mean peak of release occurred from the 25th to 29th lunar day or just before the new moon, while peak in diel timing in planulation occurred during daytime between 08:00–11:00 h. Elsewhere in the Pacific, Porites cylindrica colonies are reported to broadcast spawn. If our species identification is correct, then this is the first report of brooding in P. cylindrica. Although there are no apparent morphological differences between the coral in this study and P. cylindrica reported from other sites, an alternative explanation for our findings is that our provisionally identified Porites cf. cylindrica is a different species. If so, our findings further highlight how difficulties with species identification in corals can influence our understanding of geographical variation in reproductive biology.     

Coral communities and reef growth in the southern Great Barrier Reef

 Fringing reef development is limited around 22° S along the inner Great Barrier Reef, although there is substantial development north and south of this latitude. This study examined the relationships among coral communities and the extent of reef development. Reefs were examined to determine coral composition, colony abundance, colony size and growth form between the latitudes 20°S and 23°S. Major reef framework builders (scler- actinian genus Acropora and families Faviidae and Poritidae) dominated reefs north and south of 22°S, but declined significantly at 22°S where foliose and encrusting corals (Turbinaria and Montipora spp.) were most common. Porites spp. were present at 22° S but had encrusting morphologies. Consistently high turbidity at this latitude, caused by a 10 m tidal range and strong tidal flows, resuspends silts from the shallow shelf, and appears to have precluded reef development throughout the Holocene, by limiting the abundance, stunting the growth, and shortening the life expectancies of reef framework corals. The distinctions between ‘natural’ and ‘human-induced’ degradation may be interpreted on the basis of the relationship between Holocene development and current benthic community longevity. A mismatch between substantial past reef building capacity (a broad and/or thick reef) and non-existent or limited present reef-building capacity could signify anything from a long-period, natural cycle to an unprecedented deterioration in ecosystem function caused by human influence. Accepted: 29 July 1996     

Coral growth with thermal stress and ocean acidification: lessons from the eastern tropical Pacific

The rapid growth of scleractinian corals is responsible for the persistence of coral reefs through time. Coral growth rates have declined over the past 30 years in the western Pacific, Indian, and North Atlantic Oceans. The spatial scale of this decline has led researchers to suggest that a global phenomenon like ocean acidification may be responsible. A multi-species inventory of coral growth from Pacific Panamá confirms that declines have occurred in some, but not all species. Linear extension declined significantly in the most important reef builder of the eastern tropical Pacific, Pocillopora damicornis, by nearly one-third from 1974 to 2006. The rate of decline in skeletal extension for P. damicornis from Pacific Panamá (0.9% year⁻¹) was nearly identical to massive Porites in the Indo-Pacific over the past 20–30 years (0.89–1.23% year⁻¹). The branching pocilloporid corals have shown an increased tolerance to recurrent thermal stress events in Panamá, but appear to be susceptible to acidification. In contrast, the massive pavonid corals have shown less tolerance to thermal stress, but may be less sensitive to acidification. These differing sensitivities will be a fundamental determinant of eastern tropical Pacific coral reef community structure with accelerating climate change that has implications for the future of reef communities worldwide.     

Spatial and temporal variation in coral predation by parrotfishes on the GBR: evidence from an inshore reef

There have been few studies of coral predation by fishes on the Great Barrier Reef (GBR). However, these studies have indicated that it is an important factor that may shape coral demographics. Here, for the first time, we document the spatial and temporal variation in coral predation by parrotfishes on an inshore reef on the GBR. The densities of parrotfish feeding scars on massive Porites spp. were compared within core and non-core areas of three Chlorurus microrhinos home ranges. The density of parrotfish feeding scars on massive Porites is among the highest recorded on the GBR and elsewhere with a higher abundance of excavating feeding scars within core areas, reflecting the higher occupancy of these areas by C. microrhinos. Furthermore, excavating scars were more abundant in October than in April. This may be related to the higher nutritional quality of coral colonies in October, as coral spawning usually occurs in November at this study location. No spatial or temporal variation was noted in the abundance of feeding scars from scraping parrotfishes. The lack of temporal differences may be a result of the shallow scraping scars which would not be able to reach the gonads within coral polyps. The frequency of parrotfish predation on Porites and the spatial and temporal variation recorded herein highlight the potential importance of parrotfish corallivory on the GBR.     

Suppressed recovery of functionally important branching Acropora drives coral community composition changes following mass bleaching in Indonesia

Mass coral bleaching events may have disproportionate effects on branching corals, leading to coral community restructuring, reduced biodiversity, and decreased structural complexity. This affects overall reef health and resilience. Functionally important, fast-growing branching Acropora corals were a historically dominant and vital component of Indonesian reefs throughout the twentieth century, yet the genus is also one of the most vulnerable to external stressors. This study used long-term annual reef monitoring data from Indonesia’s Wakatobi Marine National Park (WMNP) to investigate the effects of a mass bleaching event in 2010 on Acropora and other branching corals, evaluate their post-disturbance recovery trajectories, and analyse shifts in coral community composition. Post-bleaching scleractinian coral cover decreased across study sites, with losses in branching corals especially evident. Long-term branching Acropora cover decreased significantly and failed to demonstrate the significant post-disturbance recovery of other branching corals (especially Porites). In areas characterised by relatively high branching Acropora cover (> 15% mean cover) prior to bleaching, long-term coral community composition changes have trended predominately towards branching and massive Porites and branching Montipora. The novelty and key contribution of this study is that results suggest suppressed recovery of Acropora in the WMNP. Contributing factors may include the Allee effect (inhibition of reproduction at low population densities), other forms of inhibited larval recruitment, direct and indirect spatial competition, and changes in the physical reef habitat. These findings have critical implications for this functionally important taxon, future reef conservation efforts, and overall reef health and resilience in the park.