Showing papers by "James Cook University published in 2007"
TL;DR: Experimentally manipulated the density of large herbivorous fishes to test their influence on the resilience of coral assemblages in the aftermath of regional-scale bleaching in 1998, the largest coral mortality event recorded to date.
1,427 citations
TL;DR: It is important for the scientific community and conservation agencies to recognize and manage the threat of chytridiomycosis to remaining species of frogs, especially those that are naive to the pathogen.
Abstract: The global emergence and spread of the pathogenic, virulent, and highly transmissible fungus Batrachochytrium dendrobatidis, resulting in the disease chytridiomycosis, has caused the decline or extinction of up to about 200 species of frogs. Key postulates for this theory have been completely or partially fulfilled. In the absence of supportive evidence for alternative theories despite decades of research, it is important for the scientific community and conservation agencies to recognize and manage the threat of chytridiomycosis to remaining species of frogs, especially those that are naive to the pathogen. The impact of chytridiomycosis on frogs is the most spectacular loss of vertebrate biodiversity due to disease in recorded history.
1,137 citations
TL;DR: The plutonic archive is unlocked through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia.
Abstract: Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.
1,086 citations
TL;DR: Seagrass bioregions at the scale of ocean basins are identified based on species distributions which are supported by genetic patterns of diversity, and provide a useful framework for interpreting ecological, physiological and genetic results collected in specific locations or from particular species.
894 citations
TL;DR: Biodiversity is not static in time or space but generated and maintained by natural processes, and humans are altering the planet in diverse ways at ever faster rates.
Abstract: Conservation planning is the process of locating, configuring, implementing and maintaining areas that are managed to promote the persistence of biodiversity and other natural values. Conservation planning is inherently spatial. The science behind it has solved important spatial problems and increasingly influenced practice. To be effective, however, conservation planning must deal better with two types of change. First, biodiversity is not static in time or space but generated and maintained by natural processes. Second, humans are altering the planet in diverse ways at ever faster rates.
870 citations
TL;DR: The results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.
Abstract: Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia's Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef-building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (>50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.
790 citations
TL;DR: In this article, the authors develop an integrative perspective on catch-and-release (C&R) by drawing on historical, philosophical, socio-psychological, biological, and managerial insights and perspectives.
Abstract: Most research on catch-and-release (C&R) in recreational fishing has been conducted from a disciplinary angle focusing on the biological sciences and the study of hooking mortality after release. This hampers understanding of the complex and multifaceted nature of C&R. In the present synopsis, we develop an integrative perspective on C&R by drawing on historical, philosophical, socio-psychological, biological, and managerial insights and perspectives. Such a perspective is helpful for a variety of reasons, such as 1) improving the science supporting successful fisheries management and conservation, 2) facilitating dialogue between managers, anglers, and other stakeholders, 3) minimizing conflict potentials, and 4) paving the path toward sustainable recreational fisheries management. The present work highlights the array of cultural, institutional, psychological, and biological factors and dimensions involved in C&R. Progress toward successful treatment of C&R might be enhanced by acknowledging the complex...
594 citations
TL;DR: If natal homing of larvae is a common life-history strategy, the appropriate spatial scales for the management and conservation of coral reefs are likely to be much smaller than previously assumed.
Abstract: The scale of larval dispersal of marine organisms is important for the design of networks of marine protected areas. We examined the fate of coral reef fish larvae produced at a small island reserve, using a mass-marking method based on maternal transmission of stable isotopes to offspring. Approximately 60% of settled juveniles were spawned at the island, for species with both short ( 1 month) pelagic larval durations. If natal homing of larvae is a common life-history strategy, the appropriate spatial scales for the management and conservation of coral reefs are likely to be much smaller than previously assumed.
568 citations
TL;DR: It was concluded that maximum stomatal apertures could not be obtained in at least one of the species (the grass Triticum aestivum) without a substantial reduction in subsidiary cell osmotic and turgor pressure duringStomatal opening to overcome the large mechanical advantage of subsidiary cells.
Abstract: Given that stomatal movement is ultimately a mechanical process and that stomata are morphologically and mechanically diverse, we explored the influence of stomatal mechanical diversity on leaf gas exchange and considered some of the constraints. Mechanical measurements were conducted on the guard cells of four different species exhibiting different stomatal morphologies, including three variants on the classical "kidney" form and one "dumb-bell" type; this information, together with gas-exchange measurements, was used to model and compare their respective operational characteristics. Based on evidence from scanning electron microscope images of cryo-sectioned leaves that were sampled under full sun and high humidity and from pressure probe measurements of the stomatal aperture versus guard cell turgor relationship at maximum and zero epidermal turgor, it was concluded that maximum stomatal apertures (and maximum leaf diffusive conductance) could not be obtained in at least one of the species (the grass Triticum aestivum) without a substantial reduction in subsidiary cell osmotic (and hence turgor) pressure during stomatal opening to overcome the large mechanical advantage of subsidiary cells. A mechanism for this is proposed, with a corollary being greatly accelerated stomatal opening and closure. Gas-exchange measurements on T. aestivum revealed the capability of very rapid stomatal movements, which may be explained by the unique morphology and mechanics of its dumb-bell-shaped stomata coupled with "see-sawing" of osmotic and turgor pressure between guard and subsidiary cells during stomatal opening or closure. Such properties might underlie the success of grasses.
471 citations
TL;DR: This work investigated the role of animal behavior in retention and homing of coral reef fish larvae resulting in two important discoveries: (i) Settling larvae are capable of olfactory discrimination and prefer the odor of their home reef, thereby demonstrating to us that nearby reefs smell different.
Abstract: Many marine fish and invertebrates show a dual life history where settled adults produce dispersing larvae. The planktonic nature of the early larval stages suggests a passive dispersal model where ocean currents would quickly cause panmixis over large spatial scales and prevent isolation of populations, a prerequisite for speciation. However, high biodiversity and species abundance in coral reefs contradict this panmixis hypothesis. Although ocean currents are a major force in larval dispersal, recent studies show far greater retention than predicted by advection models. We investigated the role of animal behavior in retention and homing of coral reef fish larvae resulting in two important discoveries: (i) Settling larvae are capable of olfactory discrimination and prefer the odor of their home reef, thereby demonstrating to us that nearby reefs smell different. (ii) Whereas one species showed panmixis as predicted from our advection model, another species showed significant genetic population substructure suggestive of strong homing. Thus, the smell of reefs could allow larvae to choose currents that return them to reefs in general and natal reefs in particular. As a consequence, reef populations can develop genetic differences that might lead to reproductive isolation.
444 citations
TL;DR: In this paper, an oil-in-water nano-emulsion by microfluidization and ultrasonication for spray drying encapsulation was produced, where Maltodextrin combined with a surface-active biopolymer (Hi-Cap) at a ratio of 3:1 were used as the continuous phase, while dispersed phase consisted of d-limonene.
TL;DR: The reductionist approach taken in some lines of investigation of EAE resulted in a reliance on results obtained under a narrow range of conditions, and although such studies made important contributions to molecular understanding of inflammation, T-cell activation, and MHC restriction, they did not advance as effectively the authors' knowledge of the polyantigenic responses that usually occur in CNS immunopathology and autoimmunity.
Abstract: Experimental autoimmune encephalomyelitis (EAE) is a model of the neuroimmune system responding to priming with central nervous system (CNS)-restricted antigens. It is an excellent model of post-vaccinal encephalitis and a useful model of many aspects of multiple sclerosis. EAE has been established in numerous species and is induced by priming with a large number of CNS-derived antigens. As a consequence, the pathogenesis, pathology and clinical signs vary significantly between experimental protocols. As I describe in this Timeline article, the reductionist approach taken in some lines of investigation of EAE resulted in a reliance on results obtained under a narrow range of conditions. Although such studies made important contributions to our molecular understanding of inflammation, T-cell activation, and MHC restriction, they did not advance as effectively our knowledge of the polyantigenic responses that usually occur in CNS immunopathology and autoimmunity.
TL;DR: A series of conceptual models are presented describing the factors driving the light climate and seagrass responses under current and future conditions, with special attention on the deepest edge of the meadow.
TL;DR: In this article, the authors synthesize the literature on the customary management of coral reefs emerging from diverse disciplines including anthropology, common property economics, and ecology, and conclude that practical and conceptual differences exist between customary management and contemporary conservation which have often led to failed attempts to hybridize these systems.
TL;DR: It is therefore important that dentists remain constantly informed regarding up-to-date measures on how to deal with newer technologies and dental materials.
Abstract: Despite numerous technical advances in recent years, many occupational health problems still persist in modern dentistry. These include percutaneous exposure incidents (PEI); exposure to infectious diseases (including bioaerosols), radiation, dental materials, and noise; musculoskeletal disorders; dermatitis and respiratory disorders; eye injuries; and psychological problems. PEI remain a particular concern, as there is an almost constant risk of exposure to serious infectious agents. Strategies to minimise PEI and their consequences should continue to be employed, including sound infection control practices, continuing education and hepatitis B immunisation. As part of any infection control protocols, dentists should continue to utilise personal protective measures and appropriate sterilisation or other high-level disinfection techniques. Aside from biological hazards, dentists continue to suffer a high prevalence of musculoskeletal disorders (MSD), especially of the back, neck and shoulders. To fully understand the nature of these problems, further studies are needed to identify causative factors and other correlates of MSD. Continuing education and investigation of appropriate interventions to help reduce the prevalence of MSD and contact dermatitis are also needed. For these reasons, it is therefore important that dentists remain constantly informed regarding up-to-date measures on how to deal with newer technologies and dental materials.
TL;DR: Consideration of these patterns of gene distribution underscores the likely significance of gene loss during animal evolution whilst indicating ancient origins for many components of the vertebrate innate immune system.
Abstract: Background
Characterization of the innate immune repertoire of extant cnidarians is of both fundamental and applied interest - it not only provides insights into the basic immunological 'tool kit' of the common ancestor of all animals, but is also likely to be important in understanding the global decline of coral reefs that is presently occurring. Recently, whole genome sequences became available for two cnidarians, Hydra magnipapillata and Nematostella vectensis, and large expressed sequence tag (EST) datasets are available for these and for the coral Acropora millepora.
TL;DR: It is suggested that many remaining Australian mammals would benefit from the positive management of dingoes, and a strong positive relationship between the survival of marsupials and the geographical overlap with high-density dingo populations is shown.
Abstract: Top predators in terrestrial ecosystems may limit populations of smaller predators that could otherwise become over abundant and cause declines and extinctions of some prey. It is therefore possible that top predators indirectly protect many species of prey from excessive predation. This effect has been demonstrated in some small-scale studies, but it is not known how general or important it is in maintaining prey biodiversity. During the last 150 years, Australia has suffered the world's highest rate of mammal decline and extinction, and most evidence points to introduced mid-sized predators (the red fox and the feral cat) as the cause. Here, we test the idea that the decline of Australia's largest native predator, the dingo, played a role in these extinctions. Dingoes were persecuted from the beginning of European settlement in Australia and have been eliminated or made rare over large parts of the continent. We show a strong positive relationship between the survival of marsupials and the geographical overlap with high-density dingo populations. Our results suggest that the rarity of dingoes was a critical factor which allowed smaller predators to overwhelm marsupial prey, triggering extinction over much of the continent. This is evidence of a crucial role of top predators in maintaining prey biodiversity at large scales in terrestrial ecosystems and suggests that many remaining Australian mammals would benefit from the positive management of dingoes.
TL;DR: In this article, an oil-in-water nano-emulsion with different compositions of the continuous and dispersed phases through microfluidization was produced, and it was found that a d-limonene volume fraction of 0.10 was the optimum dispersed-phase concentration in terms of emulsion droplet size.
Abstract: The purpose of this study was to produce an oil-in-water nano-emulsion with different compositions of the continuous and dispersed phases through microfluidization. The aqueous phase was a solution of maltodextrin with five different emulsifying ingredients including modified starch (Capsul and Hi-Cap), sodium caseinate (SC), whey protein hydrolysate (WPH), or whey protein concentrate (WPC), while the oil phase consisted of d-limonene or fish oil. Results showed that micofluidizer was capable of producing nano-emulsions (D32 as small as 150 nm) with a narrow size distribution. Generally, moderate microfluidization pressures (42–63 MPa) and cycles (1–2) were the optimum conditions beyond which, there were adverse changes in the emulsion size. For the two oils tested as the dispersed phase, fish oil emulsions had lower Sauter mean diameters (D32) but with wider size distributions than d-limonene. When different emulsifying ingredients were compared, Hi-Cap produced nano-emulsions with the narrowest distribution but highest D32 (about 600 nm). Nano-emulsions with WPC had the smallest D32 (about 200 nm) but the widest size distribution. It was found that a d-limonene volume fraction of 0.10 was the optimum dispersed-phase concentration in terms of emulsion droplet size (D32). Also, adding a surfactant (Tween 20) helped to reduce the emulsion size significantly during microfluidization, but it lead to extensive flocculation of emulsion droplets because of surfactant–biopolymer interactions and emulsifier displacement.
TL;DR: In this article, the authors present an updated compilation of marine carbonate δ18O from around the world, covering the Phanerozoic and Precambrian rock records.
TL;DR: Differences in susceptibility to chytridiomycosis among four Australian species after experimental infection with B. dendrobatidis are demonstrated, and it is observed that circulating granulocyte, but not lymphocyte, counts differed between infected and uninfected Lit.
Abstract: Innate immune mechanisms of defense are especially important to ectothermic vertebrates in which adaptive immune responses may be slow to develop. One innate defense in amphibian skin is the release of abundant quantities of antimicrobial peptides. Chytridiomycosis is an emerging infectious disease of amphibians caused by the skin fungus, Batrachochytrium dendrobatidis. Susceptibility to chytridiomycosis varies among species, and mechanisms of disease resistance are not well understood. Previously, we have shown that Australian and Panamanian amphibian species that possess skin peptides that effectively inhibit the growth of B. dendrobatidis in vitro tend to survive better in the wild or are predicted to survive the first encounter with this lethal pathogen. For most species, it has been difficult to experimentally infect individuals with B. dendrobatidis and directly evaluate both survival and antimicrobial peptide defenses. Here, we demonstrate differences in susceptibility to chytridiomycosis among four Australian species (Litoria caerulea, Litoria chloris, Mixophyes fasciolatus and Limnodynastes tasmaniensis) after experimental infection with B. dendrobatidis, and show that the survival rate increases with the in vitro effectiveness of the skin peptides. We also observed that circulating granulocyte, but not lymphocyte, counts differed between infected and uninfected Lit. chloris. This suggests that innate granulocyte defenses may be activated by pathogen exposure. Taken together, our data suggest that multiple innate defense mechanisms are involved in resistance to chytridiomycosis, and the efficacy of these defenses varies by amphibian species.
TL;DR: In this article, a survey of 480 tourists was conducted adjacent to the Great Barrier Reef in Northern Australia to gather data about the destination image attributes of two regional destinations that were branded by a state destination marketing organization.
Abstract: Destination branding is growing rapidly as an approach to tourism destination promotion. While this concept has been borrowed from the world of general consumer goods and applied in a number of national tourism destinations, academic analysis of the value and effectiveness of destination branding has emerged more slowly. The present article addresses this paucity of academic scrutiny by examining the value of the destination brand personality construct in distinguishing between two regional tourism destinations. A survey of 480 tourists was conducted adjacent to the Great Barrier Reef in Northern Australia to gather data about the destination image attributes of two regional destinations that were branded by a state destination marketing organization. The results indicated that tourists were able to articulate different destination brand personalities for each region. The results also indicated that more work might need to be done to adapt existing frameworks of brand personality to the tourism context.
TL;DR: This unusual pattern of hydraulic regulation, referred to here as isohydrodynamic, is explained by a hydromechanical stomatal control model where plant hydraulic conductance is dependent on transpiration rate.
Abstract: Isohydric and anisohydric regulations of plant water status have been observed over several decades of field, glasshouse and laboratory studies, yet the functional significance and mechanism of both remain obscure. We studied the seasonal trends in plant water status and hydraulic properties in a natural stand of Eucalyptus gomphocephala through cycles of varying environmental moisture (rainfall, groundwater depth, evaporative demand) in order to test for isohydry and to provide physiological information for the mechanistic interpretation of seasonal trends in plant water status. Over a 16 month period of monitoring, spanning two summers, midday leaf water potential (Ψleaf) correlated with predawn Ψleaf, which was correlated with water table depth below ground level, which in turn was correlated with total monthly rainfall. Eucalyptus gomphocephala was therefore not seasonally isohydric. Despite strong stomatal down-regulation of transpiration rate in response to increasing evaporative demand, this was insufficient to prevent midday Ψleaf from falling to levels below −2 MPa in the driest month, well into the region likely to induce xylem air embolisms, based on xylem vulnerability curves obtained in the study. However, even though midday Ψleaf varied by over 1.2 MPa across seasons, the hydrodynamic (transpiration-induced) water potential gradient from roots to shoots (ΔΨplant), measured as the difference between predawn and midday Ψleaf, was relatively constant across seasons, averaging 0.67 MPa. This unusual pattern of hydraulic regulation, referred to here as isohydrodynamic, is explained by a hydromechanical stomatal control model where plant hydraulic conductance is dependent on transpiration rate.
TL;DR: The properties of LA are explored with particular emphasis on how this agent, particularly the R-alpha-enantiomer, may be effective to treat AD and related dementias.
TL;DR: A survivorship model using coral energy status (lipid stores) as a predictor variable provided an excellent fit to the data, suggesting that much of the variation in survivorship among treatments and over time can be explained by colony energetics.
Abstract: The most severe outcome of coral bleaching is colony mortality. However, the risk of mortality is one of the least understood consequences for reef corals under climate-change scenarios. Specifically, links among combinations of temperature anomalies, varying solar irradiance, reduced water quality, and mortality risks are unclear. Here, we analyze the effects of high temperature, irradiance, and sediment loading on coral survivorship in a controlled tank experiment using Acropora intermedia from the inner Great Barrier Reef lagoon. Survival analyses based on the fate of 1600 subcolonies revealed that temperature and sediment exerted strong effects on coral mortality risk. As expected, high temperature increased mortality risk at all light and sediment levels. However, high sediment reduced mortality under high temperature and/or high light, potentially by alleviating light pressure and by providing an alternative food source for bleached corals. A survivorship model using coral energy status (lipid stores) as a predictor variable provided an excellent fit to the data, suggesting that much of the variation in survivorship among treatments and over time can be explained by colony energetics. Our study provides a new framework for predicting coral mortality risk under complex bleaching scenarios in which multiple environmental variables are involved.
TL;DR: In this paper, the authors argue that an econometric definition of endogeneity clarifies its meaning in empirical research, and present a series of basic issues that concern endogeneity and theory construction.
Abstract: A current issue of potential concern in theory-based management accounting research is the extent to which endogeneity limits the validity of empirical testing of models. This paper aims to stimulate debate as to the meaning of endogeneity as it applies to (management) accounting research. The paper explains what endogeneity is, its causes and consequences, and potential ways of managing the problem. Specifically, the paper argues that an econometric definition of endogeneity clarifies its meaning in empirical research. A series of basic issues that concern endogeneity and theory construction are presented. These include omitted variables, simultaneity, equilibrium conditions and issues concerning choice variables. Finally, possible approaches for dealing with endogeneity are presented.
TL;DR: The authors explored the links among four key constructs proposed for the destination branding and choice process-tourist needs, destination brand personality, self-congruity, and intentions to visit and satisfaction with a visit.
Abstract: Despite a growing body of work on destination branding, there has been little investigation of whether or not tourists attribute brand personality characteristics to tourism destinations and whether or not an emotional connection exists based on tourists' perceived self-image and the 'brand personality' of destinations. The aim of this study is to explore the links among four key constructs proposed for the destination branding and choice process-tourist needs, destination brand personality, self-congruity, and intentions to visit and satisfaction with a visit. The results indicate that where tourists can make an association between a destination and a destination brand personality, and where this association is consistent with their desired holiday experience, a high level of congruity will exist between the tourists' self-image and their perceptions of the destination. In turn this self-congruity was related to satisfaction with a visit to the destination but not to intention to travel to the destination.
TL;DR: The validation algorithm developed in this paper aims to localize and quantify segmentation inaccuracies; and allow the assessment of segmentation results on the whole.
TL;DR: In this paper, a conceptual model of resource dependency is developed in terms of occupational attachment, attachment to place, employability, family attitude to change, business size, business approach, financial situation, level of specialisation, time spent harvesting, and interest in and knowledge of the environment.
Abstract: Maintaining a healthy balance between human prosperity and environmental integrity is at the core of the principles of Ecological Sustainable Development. Resource-protection policies are frequently implemented so as to regulate the balance between resource access and use, however, they can inadvertently compromise the ability of resource users to adapt and be resilient. Resource users who are especially dependent on a resource are more seriously compromised. But how do we define and measure resource dependency? And how do we assess its ability to influence social resilience? In this study, a conceptual model of resource dependency is developed in terms of: (i) occupational attachment, (ii) attachment to place, (iii) employability, (iv) family attitude to change, (v) business size, (vi) business approach, (vii) financial situation, (viii) level of specialisation, (ix) time spent harvesting, and (x) interest in and knowledge of the environment. The model of resource dependency and its effect on social resilience are (quantitatively and qualitatively) tested and explored using the commercial fishing industry in North Queensland, Australia. Results show that occupational attachment and employability were important influences as were business size and approach. Results can be used to identify vulnerability to institutional change and guide policy development processes.
TL;DR: In this article, the authors examined the differing influences of friends and relatives vs other travellers on the travel choices and behaviours of 412 visitors to the North Queensland Region in Australia, and found that there were significant differences across the four groups with respect to demographic characteristics, other information sources used, accommodation and transportation used, and travel activities in the destination.
Abstract: Travel research consistently shows the importance of word-of-mouth (WOM) information sources in the travel decision-making process. Friends and relatives have been identified as organic image-formation agents, and it has been emphasized that this WOM information is one of the most relied-upon sources of information for destination selection. While there has been recognition of the importance of WOM information sources on consumer behaviour in tourism, little has been performed to understand more specifically how and what behaviour is influenced. This study examined the differing influences of friends and relatives vs. other travellers on the travel choices and behaviours of 412 visitors to the North Queensland Region in Australia. More specifically, the present study compared the following four groups of respondents: those who indicated that they obtained travel information from friends/relatives and other travellers (n = 70); those who obtained information from friends/relatives only (n = 121); those who obtained information from other travellers only (n = 105); and those who obtained information from neither (i.e. no WOM) (n = 116). The results indicated that there were significant differences across the four groups with respect to demographic characteristics, other information sources used, accommodation and transportation used, and travel activities in the destination. However, the groups did not differ in their image of the destination.
TL;DR: The results of the current study provide support for the hypothesis that algal community structure is shaped by levels of herbivory, as shown in the example of the Great Barrier Reef, Australia.
Abstract: Despite the widely accepted importance of herbivory as a determinant of reef benthic community structure, few studies have examined the relative contributions of individual species to ecosystem processes at the whole reef scale. This study quantifies the grazing impact of individual species of roving herbivorous fishes across an inner shelf fringing reef at Orpheus Island, Great Barrier Reef, Australia. Estimates of roving herbivore impact based on dawn to dusk observations of feeding rates, measurement of bite sizes and relative abundance revealed that the Orpheus Island system was dominated by 3 species: Scarus rivulatus, Chlorurus microrhinos and Siganus doliatus. The estimated impact of all 3 species varied significantly across the reef depth gradient, with the rate of disturbance peaking at the crest and decreasing significantly down the slope and across the reef flat. The estimated species-specific disturbance levels suggested that during the course of a single month 104% of a square metre area of the reef crest is grazed by S. rivulatus while 40% is subject to grazing by C. microrhinos. A total of 26 cm3 of algal material is removed from the same area by S. doliatus. Overall, there was a 240-fold decrease in grazing activity across the reef flat from that at the crest. The pattern of grazing impact of the numerically dominant siganid and scarid fishes was negatively correlated with the distribution of macroalgae across the same reef gradient. The results of the current study provide support for the hypothesis that algal community structure is shaped by levels of herbivory.