- James Cook University, ARC CoE Coral Reef Studies, Graduate Studentadd
Research Interests:
Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who... more
Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them1. Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 20162, corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3–4 °C-weeks. After eight months, an exposure of 6 °C-weeks or more drove an unprecedented, regional-scale shift in the composition of coral assemblages, reflecting markedly divergent responses to heat stress by different taxa. Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs comprising the world’s largest coral reef system. Our study bridges the gap between the theory and practice of assessing the risk of ecosystem collapse, under the emerging framework for the International Union for Conservation of Nature (IUCN) Red List of Ecosystems3, by rigorously defining both the initial and collapsed states, identifying the major driver of change, and establishing quantitative collapse thresholds. The increasing prevalence of post-bleaching mass mortality of corals represents a radical shift in the disturbance regimes of tropical reefs, both adding to and far exceeding the influence of recurrent cyclones and other local pulse events, presenting a fundamental challenge to the long-term future of these iconic ecosystems.
Research Interests:
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on... more
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coral-associated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent
of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading
to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences
of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their
contribution to reef resilience and their conservation needs.
of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading
to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences
of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their
contribution to reef resilience and their conservation needs.
Research Interests:
Corals are an essential and threatened habitat for a diverse range of reef-associated animals. Episodes of coral bleaching are predicted to increase in frequency and intensity over coming decades, yet the effects of coral-host bleaching... more
Corals are an essential and threatened habitat for a diverse range of reef-associated animals. Episodes of coral bleaching are predicted to increase in frequency and intensity over coming decades, yet the effects of coral-host bleaching on the associated animal communities remain poorly understood. The present study investigated the effects of host-colony bleaching on the obligate coral-dwelling crab, Trapezia cymodoce, during a natural bleaching event in the lagoon of Lizard Island, Australia. Branching corals, which harbour the highest diversity of coral associates, comprised 13% of live coral cover at the study site, with 83% affected by bleaching. Crabs on healthy and bleached colonies of Pocillopora damicornis were monitored over a 5-week period to determine whether coral bleaching affected crab density and movement patterns. All coral colonies initially contained one breeding pair of crabs. There was a significant decline in crab density on bleached corals after 5 weeks, with many corals losing one or both crabs, yet all healthy colonies retained a mating pair. Fecundity of crabs collected from bleached and healthy colonies of P. damicornis was also compared. The size of egg clutches of crabs collected from bleached hosts was 40% smaller than those from healthy hosts, indicating a significant reduction in fecundity. A laboratory experiment on movement patterns found that host-colony bleaching also prompted crabs to emigrate in search of more suitable colonies. Emigrant crabs engaged in aggressive interactions with occupants of healthy hosts, with larger crabs always usurping occupants of a smaller size. Decreased densities and clutch sizes, along with increased competitive interactions, could potentially result in a population decline of these important coral associates with cascading effects on coral health.
Research Interests:
Although mutualisms are ubiquitous in nature, our understanding of the potential impacts of climate change on these important ecological interactions is deficient. Here, we report on a thermal stress-related shift from cooperation to... more
Although mutualisms are ubiquitous in nature, our understanding of the potential impacts of climate change on these important ecological interactions is deficient. Here, we report on a thermal stress-related shift from cooperation to antagonism between members of a mutualistic coral-dwelling community. Increased mortality of coral-defending crustacean symbionts Trapezia cymodoce (coral crab) and Alpheus lottini (snapping shrimp) was observed in response to experimentally elevated temperatures and reduced coral-host (Pocillopora damicornis) condition. However, strong differential numerical effects occurred among crustaceans as a function of species and sex, with shrimp (75 %), and female crabs (55 %), exhibiting the fastest and greatest declines in numbers. These declines were due to forceful eviction from the coral-host by male crabs. Furthermore, surviving female crabs were impacted by a dramatic decline (85 %) in egg production, which could have deleterious consequences for population sustainability. Our results suggest that elevated temperature switches the fundamental nature of this interaction from cooperation to competition, leading to asymmetrical effects on species and/or sexes. Our study illustrates the importance of evaluating not only individual responses to climate change, but also potentially fragile interactions within and among susceptible species.
Research Interests:
Abstract The high biodiversity of coral reefs is attributable to the many invertebrate groups which live in symbiotic relationships with other reef organisms, particularly those which associate with the living coral habitat. However, few... more
Abstract The high biodiversity of coral reefs is attributable
to the many invertebrate groups which live in
symbiotic relationships with other reef organisms, particularly
those which associate with the living coral habitat.
However, few studies have examined the diversity and
community structure of coral-dwelling invertebrates and
how they vary among coral species. This study quantified
the species richness and composition of animals associated
with four common species of branching corals (Acropora
nasuta, A. millepora, Pocillopora damicornis, and Seriatopora
hystrix) at Lizard Island in the northern Great
Barrier Reef. One hundred and seventy-eight nominal
species from 12 different phyla were extracted across 50
replicate colonies of each coral host. A single coral colony,
approximately 20 cm in diameter, harbored as many as 73
individuals and 24 species. There were substantial differences
in invertebrate species composition among coral
hosts of different families as well as genera. Twenty-seven
species (15% of all taxa collected) were found on only one
of the four different coral species, which may potentially
indicate some level of specialization among coral hosts.
The distinct assemblages on different coral species, and the
presence of potential specialists, suggests invertebrate
communities will be sensitive to the differential loss of branching coral species resulting from coral reef
degradation.
to the many invertebrate groups which live in
symbiotic relationships with other reef organisms, particularly
those which associate with the living coral habitat.
However, few studies have examined the diversity and
community structure of coral-dwelling invertebrates and
how they vary among coral species. This study quantified
the species richness and composition of animals associated
with four common species of branching corals (Acropora
nasuta, A. millepora, Pocillopora damicornis, and Seriatopora
hystrix) at Lizard Island in the northern Great
Barrier Reef. One hundred and seventy-eight nominal
species from 12 different phyla were extracted across 50
replicate colonies of each coral host. A single coral colony,
approximately 20 cm in diameter, harbored as many as 73
individuals and 24 species. There were substantial differences
in invertebrate species composition among coral
hosts of different families as well as genera. Twenty-seven
species (15% of all taxa collected) were found on only one
of the four different coral species, which may potentially
indicate some level of specialization among coral hosts.
The distinct assemblages on different coral species, and the
presence of potential specialists, suggests invertebrate
communities will be sensitive to the differential loss of branching coral species resulting from coral reef
degradation.
Research Interests:
The role of corallivory is becoming increasingly recognised as an important factor in coral health at a time when coral reefs around the world face a number of other stressors. The polyclad flatworm, Amakusaplana acroporae, is a voracious... more
The role of corallivory is becoming increasingly recognised as an important factor in coral health at a time when coral reefs
around the world face a number of other stressors. The polyclad flatworm, Amakusaplana acroporae, is a voracious predator
of Indo-Pacific acroporid corals in captivity, and its inadvertent introduction into aquaria has lead to the death of entire coral
colonies. While this flatworm has been a pest to the coral aquaculture community for over a decade, it has only been found
in aquaria and has never been described from the wild. Understanding its biology and ecology in its natural environment is
crucial for identifying viable biological controls for more successful rearing of Acropora colonies in aquaria, and for our
understanding of what biotic interactions are important to coral growth and fitness on reefs. Using morphological,
histological and molecular techniques we determine that a polyclad found on Acropora valida from Lizard Island, Australia is
A. acroporae. The presence of extracellular Symbiodinium in the gut and parenchyma and spirocysts in the gut indicates that
it is a corallivore in the wild. The examination of a size-range of individuals shows maturation of the sexual apparatus and
increases in the number of eyes with increased body length. Conservative estimates of abundance show that A. acroporae
occurred on 7 of the 10 coral colonies collected, with an average of 2.660.65 (mean 6SE) animals per colony. This
represents the first report of A. acroporae in the wild, and sets the stage for future studies of A. acroporae ecology and life
history in its natural habitat.
around the world face a number of other stressors. The polyclad flatworm, Amakusaplana acroporae, is a voracious predator
of Indo-Pacific acroporid corals in captivity, and its inadvertent introduction into aquaria has lead to the death of entire coral
colonies. While this flatworm has been a pest to the coral aquaculture community for over a decade, it has only been found
in aquaria and has never been described from the wild. Understanding its biology and ecology in its natural environment is
crucial for identifying viable biological controls for more successful rearing of Acropora colonies in aquaria, and for our
understanding of what biotic interactions are important to coral growth and fitness on reefs. Using morphological,
histological and molecular techniques we determine that a polyclad found on Acropora valida from Lizard Island, Australia is
A. acroporae. The presence of extracellular Symbiodinium in the gut and parenchyma and spirocysts in the gut indicates that
it is a corallivore in the wild. The examination of a size-range of individuals shows maturation of the sexual apparatus and
increases in the number of eyes with increased body length. Conservative estimates of abundance show that A. acroporae
occurred on 7 of the 10 coral colonies collected, with an average of 2.660.65 (mean 6SE) animals per colony. This
represents the first report of A. acroporae in the wild, and sets the stage for future studies of A. acroporae ecology and life
history in its natural habitat.
Research Interests:
A number of gastropod species are known to associate with live coral, depending on the coral as a source of food (Robertson 1970). Diodora galeata (Helbling 1779) is a small limpet (up to 20 mm in length; Fig. 1a) belonging to the family... more
A number of gastropod species are known to associate with live coral, depending on the coral as a source of food (Robertson 1970). Diodora galeata (Helbling 1779) is a small limpet (up to 20 mm in length; Fig. 1a) belonging to the family Fissurellidae (keyhole limpets). Although mainly herbivorous, grazing on micro-algae, some fissurellids have also been observed to graze on sponges and detritus (Fretter and Graham 1976). However, little is known about the ecology of this family.
The occurrence of corallivory among this family is now reported for the first time. Recent observations were made in the field of D. galeata occurring on and apparently consuming the tissue of three pocilloporid corals; : Pocillopora damicornis, P. verrucosa (Fig. 1b, c) and Stylophora pistillata. To confirm these observations, 40 colonies of P.ocillopora damicornis were collected from 2-3 m depth within the lagoon of Lizard Island, Australia and examined in the laboratory. They contained 22 specimens of D. galeata ranging from 13-19 mm (Fig. 1c). Although most colonies contained were found to have only one individual, two colonies had two individuals. Only Each coloniesy, on which the animal was present, exhibited areas of recent tissue loss, exposing denuded coral skeleton, usually extending down one or more branches. The animals were located within the margins of these feeding scars and . The animals were observed actively moving over areas of live coral tissue. Some colonies had several feeding scars, resulting in considerable tissue loss (Fig. 1d).
Algae-covered shells render these animals inconspicuous. They were also usually most occurred commonly found deep within the branches of their coral host. As they have not previously been known to consume coral, they may have been overlooked thus far and their feeding scars attributed to other species. It is also unknown if these animals occur on non-pocilloporid corals. Diodora have a long life-span (10-20 years) and do not have a planktonic larval phase, thus dispersion is limited to the immediate vicinity of the adults (i.e., <10 m) (Fretter and Graham 1962) enabling the occurrence of high densities within a given area. They are also attributed a long life-span (10-20yrs). As tThese life history traits could lend this species the potential to be a significant corallivore, future studies need to assess their impact on coral reefs.
The occurrence of corallivory among this family is now reported for the first time. Recent observations were made in the field of D. galeata occurring on and apparently consuming the tissue of three pocilloporid corals; : Pocillopora damicornis, P. verrucosa (Fig. 1b, c) and Stylophora pistillata. To confirm these observations, 40 colonies of P.ocillopora damicornis were collected from 2-3 m depth within the lagoon of Lizard Island, Australia and examined in the laboratory. They contained 22 specimens of D. galeata ranging from 13-19 mm (Fig. 1c). Although most colonies contained were found to have only one individual, two colonies had two individuals. Only Each coloniesy, on which the animal was present, exhibited areas of recent tissue loss, exposing denuded coral skeleton, usually extending down one or more branches. The animals were located within the margins of these feeding scars and . The animals were observed actively moving over areas of live coral tissue. Some colonies had several feeding scars, resulting in considerable tissue loss (Fig. 1d).
Algae-covered shells render these animals inconspicuous. They were also usually most occurred commonly found deep within the branches of their coral host. As they have not previously been known to consume coral, they may have been overlooked thus far and their feeding scars attributed to other species. It is also unknown if these animals occur on non-pocilloporid corals. Diodora have a long life-span (10-20 years) and do not have a planktonic larval phase, thus dispersion is limited to the immediate vicinity of the adults (i.e., <10 m) (Fretter and Graham 1962) enabling the occurrence of high densities within a given area. They are also attributed a long life-span (10-20yrs). As tThese life history traits could lend this species the potential to be a significant corallivore, future studies need to assess their impact on coral reefs.