Examining the multi-scale dynamics of reefs, from population dynamics to macroevolution
Advancing the fundamental understanding of the key processes underpinning reef resilience.
James Cook University Townsville
Queensland 4811 Australia
Phone: 61 7 4781 4000
Corals know how to attract good company. New research finds that corals emit an enticing fluorescent green light that attracts the mobile microalgae, known as Symbiodinium, that are critical to the establishment of a healthy partnership.
The study led by researchers at Japan’s National Institute for Basic Biology and the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE) sheds new light on the mechanism that brings corals and Symbiodinium together, for example, following a bleaching episode.
“Most reef corals can not function without Symbiodinium,” said Shunichi Takahashi from the National Institute of Basic Biology.
“Following the back-to-back mass bleaching events, images of bleached white coral contrasted with healthy, vibrantly coloured coral were widespread. The key difference between the two is the abundance of Symbiodinum in the coral’s tissue. Without sufficient Symbiodinum, which provide corals with nutrients via photosynthesis, the coral will starve.”
“Thirty percent of corals receive their Symbiodinium from their parents, the other seventy percent, need a different mechanism” said co-author Professor Andrew Baird of Coral CoE.
But what brings the two organisms together? Corals are stationary creatures, however Symbiodinium can move freely through the water column.
The study reveals that corals have evolved a cunning ability to draw the Symbiodinium to them.
The researchers used the chalice coral, Echinophyllia aspera, to test whether the green fluorescent light emitted by corals under certain conditions can signal the Symbiodinium in the water column to move towards them: a process known as “positive phototaxis.”
“Our research identifies a novel biological signaling tool that underlies the success of a relationship essential for healthy coral reef ecosystems, ” said Prof Baird.
The paper “Green fluorescence from cnidarian hosts attracts symbiotic algae” is published in the journal Proceedings of the National Academy of Sciences.
Aihara Y, Maruyama S, Baird AH, Iguchi A, Takahashi S, Minagawa J (2019) Green fluorescence from cnidarian hosts attracts symbiotic algae. Proceedings of the National Academy of Sciences 116 (6): 2118-2123
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CONTACT FOR INTERVIEW
Prof Andrew Baird
ARC Centre of Excellence for Coral Reef Studies at James Cook University
Phone: +61 (0) 400 289 770, +61 (0)7 4781 4857 (AEST/UTC +10)
FOR FURTHER INFORMATION
Catherine Naum, Communications Manager
ARC Centre of Excellence for Coral Reef Studies
Townsville, QLD AUSTRALIA
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Corals growing in high-latitude reefs in Western Australia can regulate their internal chemistry to promote growth under cooler temperatures, according to new research at the ARC Centre of Excellence for Coral Reef Studies at The University of Western Australia.
The study, published today in Proceedings of the Royal Society B, suggests that ocean warming may not necessarily promote faster rates of calcification of corals on sub-tropical reefs where temperatures are currently cool (lower than 18C).
Lead author Claire Ross said the study was carried out over two years in Western Australia’s Bremer Bay, 515km south-east of Perth in the Great Southern region. Bremer Bay is a renowned diving, snorkelling and tourism hot spot due to its stunning crystal clear waters, white sand and high marine biodiversity.
“For two years we used cutting-edge geochemical techniques to link the internal chemistry of the coral with how fast the corals were growing in a high-latitude reef,” Ms Ross said.
“These high-latitude reefs (above 28 degrees north and below 28 degrees south) have less light and lower temperatures compared to the tropics, and essentially they provide natural laboratories for investigating the limits for coral growth.”
Ms Ross said the researchers expected the corals to grow slower during winter because the water was colder and light levels lower but they were surprised to find the opposite pattern.
“We were able to link the remarkable capacity for cold-water corals to maintain high growth during winter to the regulation of their internal chemistry,” she said.
“We also found that there was more food in the water for corals during winter compared to summer, indicating that (in addition to internal chemical regulation) corals may feed more to sustain growth.”
Coral reefs are one of world’s most valuable natural resources, providing a habitat for many ocean species, shoreline protection from waves and storms, as well as being economically important for tourism and fisheries.
However, the capacity for corals to build their skeletons is under threat due to CO2-driven climate change. The effects of climate change on coral reefs are likely to vary geographically, but relatively little is known about the growth rates of reefs outside of the tropics.
“Our study is unique because it is among the first to fully decipher the corals’ internal chemistry,” Ms Ross said. “The findings of this study help better understand and predict the future of high-latitude coral reefs under CO2-driven climate change.”
Images and video available here
Citation:Ross, CL, Schoepf, V, DeCarlo, TM, McCulloch, MT (2018). Mechanisms and seasonal drivers of calcification in the temperate coral Turbinaria reniformis at its latitudinal limits. Proceedings of the Royal Society B. Volume 285 (1879). DOI: 10.1098/rspb.2018.0215
ARC Centre of Excellence for Coral Reef Studies, UWA School of Earth Sciences
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UWA Media and Public Relations Manager
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Communications Mgr, ARC Centre of Excellence for Coral Reef Studies
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Scientists from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at The University of Western Australia (UWA) have found that some corals are able to combat the effects of ocean acidification by controlling their own chemistry.
Coral reefs play an important role in protecting coastlines from damage caused by waves and storms, but also provide habitat and shelter for many marine organisms. However, major environmental challenges such as climate change, threaten the survival of coral reefs worldwide.
The world-first study is a breakthrough for marine science because the scientists have identified marine species that are resilient to ocean changes, which will help better understand how to protect coral reefs in the future.
Lead author Dr Thomas DeCarlo said rising carbon dioxide (CO2) levels in the atmosphere were reflected in the ocean, which leads to ocean acidification.
“Acidification hampers the ability of the coral to form skeletons and shells which are the building blocks of reefs,” Dr DeCarlo said.
“In the past few decades, hundreds of experiments have shown that corals have a highly diverse response to ocean acidification depending on the species. However, the reasons why some are more tolerant than others are not clearly understood.
Dr DeCarlo and his team developed a new method to understand the internal chemistry of corals by using specialised equipment that measures the characteristics of the molecules in coral.
“The method showed corals with the most resistance are tolerant because of the way they are able to regulate their calcium levels,” Dr DeCarlo said. “This technique means scientists can identify species that are relatively resistant to ocean acidification.”
“However, we are also looking at the costs associated with resisting acidification, which may potentially make acidification-resistant corals more vulnerable to other stressors.”
Co-author Professor Malcolm McCulloch said previous studies found that even the more hardy coral species lose their ability to adapt to ocean acidification when they bleach under extreme heat events, as experienced in 2016.
“When a coral bleaches, it expels its ‘powerhouse’ – zooxanthellae symbionts, and loses the energy needed to keep its internal mechanisms running,” he said. ”The longer corals stay bleached, the less likely they are to recover.”
The paper, Coral resistance to ocean acidification linked to increased calcium at the site of calcification is published in Proceedings of the Royal Society B
Citation: DeCarlo, TM, Comeau, S, Cornwall, CE, and McCulloch, MT (2018). Coral resistance to ocean acidification linked to increased calcium at the site of calcification. Proc. R. Soc. B 20180564. DOI: http://dx.doi.org/10.1098/rspb.2018.0564
Images available here.
Thomas DeCarlo (UWA Research Fellow) (+61 4) 09 895 484 (AWST)
Catherine Naum (CoralCoE Communications Mgr) (+61 4) 28 785 895 / (+61 7) 4781 6067 (AEST)
Jess Reid (UWA Media and PR Advisor) (+61 8) 6488 6876 (AWST)
Researchers from The University of Western Australia (UWA), ARC Centre of Excellence for Coral Reef Studies (Coral CoE), and Western Australian Marine Science Institution have examined the impact of the 2016 mass bleaching event on reefs in Western Australia (WA). They found significant bleaching occurred in the inshore Kimberley region, despite Kimberley corals being known as exceptionally stress resistant. They also found mild bleaching at Rottnest Island and that the Ningaloo Reef escaped bleaching.
The 2016 mass bleaching event is the most severe global bleaching event to ever be recorded.
Coral bleaching occurs as the result of abnormal environmental conditions, such as heightened sea temperatures that cause corals to expel tiny photosynthetic algae, called ‘zooxanthellae.’ The loss of these colourful algae causes the corals to turn white, and ‘bleach’. Bleached corals can recover if the temperature drops and zooxanthellae are able to recolonise the coral, otherwise the coral may die.
The researchers, led by Coral CoE’s Dr Verena Schoepf and UWA Masters student Morane Le Nohaïc, conducted surveys on the health of coral reefs along the Western Australian coastline from tropical to temperate locations.
“We found a concerning 57 to 80 per cent of corals on inshore Kimberley reefs were bleached in April 2016 – this included Montgomery Reef, Australia’s largest inshore reef,” Dr Schoepf said.
“Our research also found that there was mild bleaching at Rottnest Island – 29 per cent of corals were moderately bleached.”
“Ningaloo Reef, a UNESCO World Heritage site, escaped bleaching, but had some temperature-unrelated coral mortality. Temperate corals at Bremer Bay (Southwest) experienced no bleaching.”
Dr Schoepf said bleaching patterns were consistent with patterns of heat stress across WA.
“This is the first documented regional-scale bleaching event in WA during an El Nino year and the first time we have been able to measure the percentage of impacted corals in 2016,” she said.
“Coral reefs in WA are now at risk of bleaching during both El Nino years, such as in 2016, and La Nina years, such as 2010/11. But the geographic footprint differs – the northwest is at risk during El Nino years, whereas Ningaloo Reef and reefs further south are at risk during the La Nina cycle.”
“As bleaching events become more common in the future, it is critical to monitor how bleaching events impact coral reef resilience, and how long it takes reefs to recover from such catastrophic events.”
The research paper “Marine heatwave causes unprecedented regional mass bleaching of thermally resistant corals in northwestern Australia” is published today in the journal Scientific Reports.
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FOR INTERVIEWS, PLEASE CONTACT:
Dr Verena Schoepf
ARC Centre of Excellence for Coral Reef Studies at University of Western Australia
Phone: (+61 8) 6488 4596 / (+61 4) 16 540 415
Ms Catherine Naum
ARC Centre of Excellence for Coral Reef Studies
Phone: (+61 7) 4781 6067 / (+61 4) 28 785 895
Scientists at the ARC Centre of Excellence for Coral Reef Studies at James Cook University say more needs to be done to protect vulnerable table corals on the Great Barrier Reef.
Researchers studying the role of table corals have found that they provide vital sun protection for large fish in shallow reef areas.
They found that the corals are so important that if lost, the fish that depend on them will leave the reef.
“The loss of table corals denies fishes important habitat, which they use to shelter from the sun, avoiding harmful UV-radiation, just as we might sit under an umbrella at the beach,” says study lead author James Kerry.
“Large fishes maintain balanced coral reef ecosystems, they’re the predators that help control fish populations,” says study co-author Professor David Bellwood.
“These fish are important for reefs and people; lose your table corals and you lose your coral trout,” Professor Bellwood explains.
The scientists say this is particularly concerning as table corals are especially vulnerable to the pressures currently facing the Great Barrier Reef.
The corals are highly susceptible to ocean acidification and bleaching, and are the preferred meal of the destructive crown of thorns starfish.
Given their shape, table corals are also easily toppled and are often destroyed in cyclones.
“Ultimately we need to conserve table corals because they are the primary structure on the Reef that provides shelter from the sun’s harmful rays. However, because they are so vulnerable to climate change and other growing threats, this is going to be a major challenge,” James Kerry says.
“The research suggests that we need to do everything we can to promote the health of the Great Barrier Reef, and in doing so, reduce the multiple threats facing these valuable corals.”
The functional role of tabular structures for large reef fishes: avoiding predators or solar irradiance? By J.T. Kerry and D.R. Bellwood is published in the journal Coral Reefs.
Do Tabular corals constitute keystone structures for fishes on coral reefs? By J.T Kerry and D.R. Bellwood is published in the journal Coral Reefs
Images and video:
Image credit – James Kerry
A new and significant role for marine reserves on the Great Barrier Reef has been revealed, with researchers finding the reserves reduce the prevalence of coral diseases.
It’s been known for some time that marine reserves are important for maintaining and enhancing fish stocks, but this is the first time marine reserves have been shown to enhance coral health on the Great Barrier Reef.
Researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University found that coral disease levels were four times lower inside no-take marine reserves, where fishing is banned, compared to outside reserves.
“We surveyed more than 80,000 corals around the Whitsunday Islands for six different diseases that commonly harm reef corals around the world,” says study lead author, Dr Joleah Lamb from the Coral CoE.
“We found three coral diseases were more prevalent on reefs outside no-take marine reserves, particularly on reefs with high levels of injured corals and discarded fishing line.”
Wounded corals are more vulnerable to disease. Damaged tissue provides sites where pathogens and parasites can invade, particularly as coral immune responses are lowered while they heal.
Dr Lamb says once a pathogen infects a coral, tissue loss typically spreads from the point of entry.
“It’s like getting gangrene on your foot and there is nothing you can do to stop it from affecting your leg and ultimately your whole body.”
“Disease outbreaks can take a heavy toll, with losses of up to 95 per cent of coral cover on some reefs in the Caribbean.”
Given the difficulty identifying pathogens that cause disease, the researchers say it’s vital to understand which activities increase the risk of coral diseases, and to protect against them.
They say discarded fishing line and levels of coral breakage, potentially from a variety of fishing-related activities, outside the no-take zones on the Great Barrier Reef are indicators of the types of activities that contribute to the problem.
“Fishing line not only causes coral tissue injuries and skeleton damage, but also provides an additional surface for potential pathogens to colonise, increasing their capacity to infect wounds caused by entangled fishing line,” Dr Lamb says.
The researchers hope their findings send a clear message to reef managers about the benefits of marine reserves for coral health.
“No take marine reserves are a promising approach for mitigating coral disease in locations where the concentration or intensity of fishing effort is relatively high,” says Professor Garry Russ from the Coral CoE.
Professor Bette Willis, also from the Coral CoE, says the scientists are now expanding their research to examine other drivers of coral disease.
“We’ve shown that there are strong links between damage and disease in this study, now we’re interested in understanding and managing other potential drivers of diseases that involve injury– such as outbreaks of crown-of-thorns starfish, cyclones, and recreational activities like anchoring.”
Paper: Lamb JB, Williamson DH, Russ GR, and BL Willis (In Press). Protected areas mitigate diseases of reef-building corals by reducing damage from fishing. Ecology. DOI:10.1890/14-1952.1
Dr Joleah Lamb – Joleah.Lamb@my.jcu.edu.au, +61 (0) 4 59 040 091
Professor Bette Willis – Bette.Willis@jcu.edu.au, +61 (0) 7 4781 5349
Researchers in Queensland have found that where baby corals choose to settle is influenced by ocean temperature and the presence of their symbiotic algae in the water.
Warmer than normal maximum temperatures are known to have a negative impact on the reproduction and survival of some corals. The researchers wanted to find out how a cooler climate, similar to that found south of the Great Barrier Reef, would affect coral larvae settlement.
“We were interested to see how temperature influenced the selection of where corals chose to settle,” says Dr Eugenia Sampayo from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at the University of Queensland.
“At colder than average ambient temperatures we found that the larvae settled on more exposed surfaces where they were more likely to be damaged or removed entirely by fish.”
Coral larvae actively search out a place to settle using a range of sensory cues. Once in place they can’t move, so a poor choice of location increases the risk of death.
As part of the experiment researchers exposed larvae from coral commonly found on the Great Barrier Reef, Acropora millepora, to several different temperatures; including normal temperatures for the Great Barrier Reef and cooler temperatures similar to those experienced south of the Great Barrier Reef.
Under normal conditions, the larvae prefer to settle on surfaces covered in crustose coralline algae, but the researchers found larvae in the cooler water were less likely to choose such a surface, reducing their chance of a successful settlement.
The researchers also examined the influence of dinoflagellates (Symbiodinium), microscopic single celled organisms that live inside coral tissue once it has settled. This so-called symbiotic relationship is essential to the survival of corals in tropical oceans.
“Perhaps the most surprising result is that the presence of these symbionts in the water also influenced whether the coral larvae settled on the algae encrusted surfaces or not,” says study lead author, Natalia Winkler from the Coral CoE.
“The fact that the symbionts can influence larval settlement without actually being inside the coral tissue highlights just how important the symbionts are for corals,” Ms Winkler says
Dr Sampayo adds the results suggest a link between crustose coralline algae and the symbionts.
“If symbionts cluster near favorable locations, the coral larvae kill two birds with one stone by finding a good spot to settle and a concentrated source of symbionts, which are normally sparse in the water,” Dr Sampayo says.
“We have discovered a previously unknown biological control over coral settlement, one that is likely to be influenced by warming oceans and that can change how corals select their life-long position on the reef.”
Symbiodinium identity alters the temperature-dependent settlement behaviour in Acropora millepora coral larvae before onset of symbiosis by Winkler NS, Pandolfi JM, Sampayo EM is published in the journal, Proceedings of the Royal Society London B. http://dx.doi.org/10.1098/rspb.2014.2260
Dr Eugenia Sampayo, Coral CoE, +61 (0) 7 3365 2729, firstname.lastname@example.org
Natalia Winkler, Coral CoE, email@example.com
Eleanor Gregory, Communications Manager, +61 (0) 428 785 895,
James Cook University Townsville
Queensland 4811 Australia
Phone: 61 7 4781 4000