Article Monitoring Coral Health to Determine Coral Bleaching Response at High Latitude Eastern Australian Reefs: An Applied Model for A Changing Climate (original) (raw)
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Diversity, 2011
Limited information is available on the bleaching susceptibility of coral species that dominate high latitude reefs along the eastern seaboard of Australia. The main aims of this study were to: (i) monitor coral health and spatial patterns of coral bleaching response at the Solitary Islands Marine Park (SIMP) and Lord Howe Island Marine Park (LHIMP), to determine variability of bleaching susceptibility among coral taxa; (ii) predict coral bleaching thresholds at 30 °S and 31.5 °S, extrapolated from published bleaching threshold data; and (iii) propose a subtropical northern New South Wales coral bleaching model from biological and physical data. Between 2005 and 2007 minor bleaching was observed in dominant coral families including Pocilloporidae, Poritidae and Dendrophylliidae in the SIMP and Pocilloporidae, Poritidae and Acroporidae (Isopora and Montipora spp.) in the LHIMP, with a clear difference in bleaching susceptibility found between sites, both within and between locations. Bleaching susceptibility was highest in Porites spp. at the most offshore island site within the SIMP during summer 2005. Patterns of subtropical family bleaching susceptibility within the SIMP and LHIMP differed to those previously reported for the central Great Barrier Reef (GBR). These differences may be due to a number of factors, including temperature history and/or the coral hosts association with different zooxanthellae clades, which may have lower thermal tolerances. An analysis of published estimates of coral bleaching thresholds from the Caribbean, South Africa, GBR and central and northern Pacific regions suggests that the bleaching threshold at 30-31.5 °S ranges between 26.5-26.8 °C. This predicted threshold was confirmed by an extensive coral
Bleaching susceptibility of aquarium corals collected across northern Australia
Coral Reefs, 2020
There are a wide range of Scleractinian corals that are collected for the global reef aquarium market, often from non-reefal environments. The sustainability of coral harvesting is potentially threatened by increasing anthropogenic disturbances and climate change, though it is unknown to what extent many commonly harvested corals are susceptible to environmental change, or actually bleach during marine heatwaves. In this study, we experimentally tested the temperature sensitivity and bleaching susceptibility of six coral species (Homophyllia australis, Micromussa lordhowensis, Catalaphyllia jardinei, Trachyphyllia geoffroyi, Duncanopsammia axifuga, and Euphyllia glabrescens), which are important components of the aquarium coral fisheries across northern Australia, in Western Australia, the Northern Territory, and/or Queensland. Interspecific differences were evident in the temperature sensitivity and bleaching susceptibility among the study species. Homophyllia australis, and M. lordhowensis were found to be particularly susceptible to elevated temperatures, whereby all corals subjected to elevated temperatures died within the course of the experimental treatment (75 d). Catalaphyllia jardinei and E. glabrescens also exhibited significant increases in mortality when exposed to elevated temperatures, though some of the corals did survive, and C. jardinei mostly died only after exposure to elevated temperatures. The other species (T. geoffroyi and D. axifuga) exhibited marked bleaching when exposed to elevated temperatures, but mortality of these corals was similar to that of conspecifics held at ambient temperatures. This study highlights the potential for environmental change to impact the sustainability and viability of Australian coral harvest fisheries. More importantly, this study highlights the need for specific and targeted in situ monitoring for important stocks of coral fishery target species, to assess their vulnerability to fishery and fisheryindependent effects.
Time-integrated thermal bleaching thresholds of reefs and their variation on the Great Barrier Reef
Marine Ecology Progress Series, 2002
Knowledge of the critical levels for key environmental variables that are likely to cause bleaching in reef corals is of fundamental importance in conducting risk assessments of potential climate-change effects on coral reefs. Such knowledge can also be used to provide early warning of mass bleaching events. A number of factors have contributed to the difficulty in determining critical levels for coral bleaching. These factors include the fact that multiple stressors may be involved in bleaching, the duration of stress required to elicit a bleaching response varies with temperature, and bleaching triggers are known to be variable in space, time and by species. In this study, I identify sea surface temperature (SST) as the most important parameter for predicting coral bleaching from 4 possible environmental variables collected over 10 to 12 yr from weather stations at 2 locations on the Great Barrier Reef (GBR): temperature, wind speed, solar radiation and barometric pressure. Predicted bleaching-response curves are constructed from high-resolution in situ temperature records and historical observations of coral bleaching for 13 locations. These curves approximate reef-wide stress-response thresholds for bleaching of thermally sensitive (and often dominant) coral species. Distinct spatial trends exist in the thermal sensitivity of coral populations that correspond with position across the shelf and latitude in the case of mid-and outer-shelf reefs. This suggests that considerable thermal adaptation has taken place over small (10s of km) and large (100s to 1000s of km) spatial scales. Bleaching curves for inshore reefs do not correspond with latitude and are more variable, reflecting greater local-scale variability in temperature regimes.
Long-term impacts of coral bleaching events on the world’s warmest reefs
The southern Arabian Gulf houses some of the most thermally tolerant corals on earth, but severe bleaching in the late 1990s caused widespread mortality. More than a decade later, corals still dominated benthos (mean: 40 3% cover on 10 sites spanning >350 km; range: 11.0e65.6%), but coral communities varied spatially. Sites to the west generally had low species richness and coral cover (mean: 3.2 species per transect, 31% cover), with Porites dominated communities (88% of coral) that are distinct from more diverse and higher cover eastern sites (mean: 10.3 species per transect, 62% cover). These patterns reflect both the more extreme bleaching to the west in the late 1990s as well as the higher faviid dominated recruitment to the east in subsequent years. There has been limited recovery of the formerly dominant Acropora, which now represents <1% of the benthos, likely as a result of recruitment failure. Results indicate that severe bleaching can have substantial long-term impacts on coral communities, even in areas with corals tolerant to environmental extremes.
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
Coral bleaching: Implications for the Great Barrier Reef Marine Park
Proceedings of the …, 1997
INTRODUCTION l Cell biology and causal mechanisms associated with the bleaching phenomenon l What is bleaching and what causes it? l What mechanism explains bleaching? l The influence of coral bleaching on reef systems: chronic versus subchronic impacts l SPATIAL AND TEMPORAL IMPLICATIONS l Corals and temperature l El Niño and coral bleaching: a connection? l Great Barrier Reef and expected temperature changes. l Is the connection between bleaching and upper thermal limits an oversimplification? l Is coral bleaching a sign of global climate change? l What should managers do? l CONCLUSION l
Coral bleaching: causes and consequences
Coral Reefs, 1997
It has been over 10 years since the phenomenon of extensive coral bleaching was first described. In most cases bleaching has been attributed to elevated temperature, but other instances involving high solar irradiance, and sometimes disease, have also been documented. It is timely, in view of our concern about worldwide reef condition, to review knowledge of physical and biological factors involved in bleaching, the mechanisms of zooxanthellae and pigment loss, and the ecological consequences for coral communities. Here we evaluate recently acquired data on temperature and irradiance-induced bleaching, including long-term data sets which suggest that repeated bleaching events may be the consequence of a steadily rising background sea temperature that will in the future expose corals to an increasingly hostile environment. Cellular mechanisms of bleaching involve a variety of processes that include the degeneration of zooxanthellae in situ, release of zooxanthellae from mesenterial ...
Marine Ecology Progress Series, 2006
The ability of corals to cope with environmental change, such as increased temperature, relies on the physiological mechanisms of acclimatisation and long-term genetic adaptation. We experimentally examined the bleaching sensitivity exhibited by 2 species of coral, Pocillopora damicornis and Turbinaria reniformis, at 3 locations across a latitudinal gradient of almost 6 degrees on the Great Barrier Reef (GBR). Target bleaching temperature was reached by using a ramping rate of 0.2°C/h. We found that the bleaching sensitivity and recovery of both species differed between corals with clade D symbionts and those with clade C. However, in P. damicornis bleaching susceptibility corresponded more strongly with latitude than with zooxanthella type and hence, temperature history, suggesting that local adaptation has occurred. The observed bleaching sensitivity was shown by a decrease in photochemical efficiency (F v /F m) in both species of coral. The rate of recovery in T. reniformis was highest in explants containing clade D symbionts. The occurrence of clade D in the northern section of the GBR may reflect a long-term response to high sea water temperatures, while the presence of clade D in low abundance in T. reniformis at Heralds Prong Reef and Percy Island may be a result of recent bleaching events.