The unique study measured how many adult corals survived along the length of the world’s largest reef system following extreme heat stress, and how many new corals they produced to replenish the Great Barrier Reef in 2018. The loss of adults resulted in a crash in coral replenishment compared to levels measured in previous years before mass coral bleaching.
“The number of coral larvae that are produced each year, and where they travel to before settling on a reef, are vital components of the resilience of the Great Barrier Reef. Our study shows that reef resilience is now severely compromised by global warming,” said co-author Professor Andrew Baird.
“The biggest decline in replenishment, a 93% drop compared to previous years, occurred in the dominant branching and table coral, Acropora. As adults these corals provide most of the three-dimensional coral habitat that support thousands of other species,” he said.
“The mix of baby coral species has shifted, and that in turn will affect the future mix of adults, as a slower than normal recovery unfolds over the next decade or longer.”
“The decline in coral recruitment matches the extent of mortality of the adult brood stock in different parts of the Reef,” added Professor Hughes. “Areas that lost the most corals had the greatest declines in replenishment.”
“We expect coral recruitment will gradually recover over the next five to ten years, as surviving corals grow and more of them reach sexual maturity, assuming of course that we don’t see another mass bleaching event in the coming decade,” he said.
So far, the Great Barrier Reef has experienced four mass bleaching events due to global warming, in 1998, 2002, and back-to-back in 2016 and 2017. Scientists predict that the gap between pairs of coral bleaching events will continue to shrink as global warming intensifies.
“It’s highly unlikely that we could escape a fifth or sixth event in the coming decade,” said co-author Professor Morgan Pratchett.
“We used to think that the Great Barrier Reef was too big to fail – until now,” he said.
“For example, when one part was damaged by a cyclone, the surrounding reefs provided the larvae for recovery. But now, the scale of severe damage from heat extremes in 2016 and 2017 was nearly 1500km—vastly larger than a cyclone track.”
Professor Pratchett added that the southern reefs that escaped the bleaching are still in very good condition, but they are too far away to replenish reefs further north.
“There’s only one way to fix this problem,” says Hughes, “and that’s to tackle the root cause of global heating by reducing net greenhouse gas emissions to zero as quickly as possible.”
Hughes T, Kerry J, Baird A, Connolly S, Chase T, Dietzel A, Hill T, Hoey A, Hoogenboom M, Jacobson M, Kerswell A, Madin J, Mieog A, Paley A, Pratchett M, Torda G, & Woods R (2019). ‘Global warming impairs stock–recruitment dynamics of corals’. Nature: http://dx.doi.org/10.1038/s41586-019-1081-y
PHOTOS & VIDEO
A selection of photos and videos relating to the study is available here. Please note that any use of this imagery MUST carry the credit given. In addition, permission must be obtained from the ARC Centre of Excellence for Coral Reef Studies for any use beyond this story.
The Australian Academy of Science have produced a video based on the study. The files are available to embed in online stories at the Dropbox hyperlink above, and the YouTube embed link is here.
CONTACTS FOR INTERVIEWS
Prof Terry Hughes (Pacific Coast Time Zone, USA) Director, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0)400 720 164 Email: email@example.com
Prof Andrew Baird (Eastern Australia Time Zone) ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0)7 4781 4857 Mobile: +61 (0)400 289 770 Email: firstname.lastname@example.org
Prof Morgan Pratchett (Eastern Australia Time Zone) ARC Centre of Excellence for Coral Reef Studies Phone: + 61 (0)7 4781 5747 Mobile: +61 (0)488 112 295 Email: email@example.com
FOR FURTHER INFORMATION
Melissa Lyne (Eastern Australia Time Zone) Media Manager, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0) 415 514 328 Email: firstname.lastname@example.org
A glimmer of hope for the world’s coral reefs
The future of the world’s coral reefs is uncertain, as the impact of global heating continues to escalate. However, according to a study published today in Nature Climate Change, the response of the Great Barrier Reef to extreme temperatures in 2017 was markedly different to one year earlier, following two back-to-back bouts of coral bleaching. Remarkably, corals that bleached and survived 2016 were more resistant in 2017 to a recurrence of hot conditions.
“Dead corals don’t bleach for a second time. The north lost millions of heat-sensitive corals in 2016, and most of the survivors were the tougher species. As a result of bleaching, the mix of species is changing very rapidly,” said lead author Prof Terry Hughes, Director of the Australian Research Council Centre of Excellence for Coral Reef Studies (Coral CoE), headquartered at James Cook University.
“We were astonished to find less bleaching in 2017, because the temperatures were even more extreme than the year before,” he said.
The new research highlights the extent of damage, or “geographic footprint” of multiple coral bleaching events across the 2,300 km length of the world-heritage listed area.
The back-to-back heatwaves bring the total number of mass bleaching events on the Great Barrier Reef to four over the past two decades (in 1998, 2002, 2016 and 2017). The scientists found that only 7% of the Great Barrier Reef escaped bleaching entirely since 1998, and after the 2017 event, 61% of reefs have now been severely bleached at least once.
“We found, using the National Oceanic and Atmospheric Administration’s (NOAA) satellite-based coral bleaching tools, that corals in the north of the Great Barrier Reef were exposed to the most heat stress in 2016. A year later, the central region saw the most prolonged heating,” said co-author Dr Mark Eakin, from NOAA’s Coral Reef Watch program, in Maryland, USA.
The southern third of the Great Barrier Reef was cooler in both years due to local weather conditions, and escaped with only minor bleaching.
“It’s only a matter of time before we see another mass-bleaching event, triggered by the next marine heatwave, driven by global heating,” said co-author Dr Andrew Hoey of Coral CoE at James Cook University. “One of the worst possible scenarios is we’ll see these southern corals succumb to bleaching in the near future.”
“The outcome in 2017 depended on the conditions experienced by the corals one year earlier. We called that ‘ecological memory,’ and show that these repeating events are now acting together in ways that we didn’t expect,” said Prof Hughes.
“We’ve never seen back-to-back mass coral bleaching before on the Great Barrier Reef, in two consecutive summers. The combined footprint has killed close to half of the corals on two-thirds of the world’s largest reef system,” said Dr Hoey.
“We need urgent global action on greenhouse emissions to save the world’s coral reefs. Australia should be – but regrettably isn’t – at the forefront of tackling global heating,” said Prof Hughes.
Citation: Hughes TP, Kerry JT, Connolly SR, Baird AH, Eakin CM, Heron SF, Hoey AS, Hoogenboom MO, Jacobson M, Liu G, Pratchett MS, Skirving W & Torda G (2019). Ecological memory modifies the cumulative impact of recurrent climate extremes. Nature Climate Change Vol 9, pp 40–43
Link to video and images here.
Please credit as marked.
Melissa Lyne, acting Communications Manager
ARC Centre of Excellence for Coral Reef Studies
P: +61 (0) 428 785 895 (AEDT/UTC +11)
Friends matter in climate change response
A James Cook University scientist is investigating how people’s social networks prompt them to take action on climate change – or discourage them from doing so – in an attempt to help communities and government adapt in response to calamitous predictions of global warming.
Dr Michele Barnes, Research Fellow at JCU’s ARC Centre of Excellence for Coral Reef Studies, is leading the project.
Dr Barnes said that the relationships we have with others – our social networks – can profoundly influence our behaviour and our capacity for action.
“What our friends and acquaintances think, say and do can have important effects on our thoughts and actions. Yet while these connections can be reliably mapped, understanding how they prompt action in response to climate change is still in its infancy.”
“It’s usually assumed that capacity to act automatically translates into action, but that’s not necessarily true. So, I’m aiming to uncover the key social factors that help or hinder action. This will be the first study to track individuals and a governance institution both before and after a coral bleaching event,” she said.
The research will focus on the Great Barrier Reef and communities based around reefs in Kenya.
“The project will significantly improve our understanding of how adaptive capacity – the ability of a system to adapt when its environment is changing – translates into adaptive action, or how it fails to do that.”
Dr Barnes said that even under the most optimistic greenhouse gas emissions scenario from the Intergovernmental Panel on Climate Change, the future of biodiversity and ecosystems is under serious threat and that researchers needed to look at how both people and institutions will react.
“Considering the scope and intensity of climate change, it’s vital people can make informed decisions to reduce their vulnerability. Likewise, building flexible governance institutions with the capacity to adapt is crucial.”
Dr Barnes said national and local governments, development agencies, and non-governmental organisations urgently need the knowledge the research will produce.
“Without a thorough understanding of what aspects of social networks translate into adaptive action, and the role of powerful groups and individuals in shaping these outcomes, their efforts risk being unproductive or harmful,” she said.
Coral bleaching on the Great Barrier Reef not limited to shallow depths
A team of international marine scientists working with the ARC Centre of Excellence for Coral Reef Studies at The University of Queensland (Coral CoE) has found evidence to suggest the 2016 coral bleaching on the Great Barrier Reef also affected deep reefs.
Although deep reefs are often considered a refuge from thermal anomalies caused by global ocean warming, the new research highlights limitations to this role and argues that both shallow and deep reefs are under threat of mass bleaching events.
Published in the journal Nature Communications, the new study focuses on the 2016 mass bleaching event that caused the death of 30 per cent of shallow-water corals on the Great Barrier Reef.
The study, details how the impacts of this bleaching did lessen over depth, but were still substantial even on the deep reef.
“It was a shock to see that the impacts extended to these dimly-lit reefs, as we were hoping that their depth may have provided protection from this devastating event,” he said.
The Great Barrier Reef is known to harbor extensive areas of deep coral reefs, however given their depth these reefs are notoriously difficult to study. Using remotely operated vehicles, the team deployed sensors down to 100 metres to characterise how temperature conditions at depth differ from those in the shallow reef.
UQ Global Change Institute Director and Coral CoE’s Deputy Director, Professor Ove Hoegh-Guldberg said the study had emphasised the unfortunate vulnerability of the Great Barrier Reef.
“We already established that the refuge role of deep reefs is generally restricted by the limited overlap in species with the shallow reef,” he said.
“However, this adds an extra limitation by demonstrating that the deep reefs themselves are also impacted by higher seawater temperatures.”
“However, when this upwelling stopped towards the end of summer, temperatures rose to record-high levels even at depth,” he said.
A team of divers then conducted surveys during the height of bleaching, across several sites on the northern Great Barrier Reef.
They noted that overall, major bleaching and mortality affected almost a quarter of corals at 40 metres, while confirming previous reports of nearly half the corals being severely affected at the shallower depths.
The researchers have now gone on to study how the process of recovery varies between shallow and deep reefs.
The scientists mapped the geographical pattern of heat exposure from satellites, and measured coral survival along the 2,300-km length of the Great Barrier Reef following the extreme marine heatwave of 2016.
The amount of coral death they measured was closely linked to the amount of bleaching and level of heat exposure, with the northern third of the Great Barrier Reef being the most severely affected. The study found that 29 per cent of the 3,863 reefs comprising the world’s largest reef system lost two-thirds or more of their corals, transforming the ability of these reefs to sustain full ecological functioning.
“The coral die-off has caused radical changes in the mix of coral species on hundreds of individual reefs, where mature and diverse reef communities are being transformed into more degraded systems, with just a few tough species remaining,” said co-author Prof Andrew Baird of Coral CoE at James Cook University.
“But, that still leaves a billion or so corals alive, and on average, they are tougher than the ones that died. We need to focus urgently on protecting the glass that’s still half full, by helping these survivors to recover,” said Prof Hughes.
The scientists say these findings reinforce the need for assessing the risk of a wide-scale collapse of reef ecosystems, especially if global action on climate change fails to limit warming to 1.5‒2 °C above pre-industrial levels.
“The Great Barrier Reef is certainly threatened by climate change, but it is not doomed if we deal very quickly with greenhouse gas emissions. Our study shows that coral reefs are already shifting radically in response to unprecedented heatwaves,” said Prof Hughes.
The researchers warn that failure to curb climate change, causing global temperatures to rise far above 2 °C, will radically alter tropical reef ecosystems and undermine the benefits they provide to hundreds of millions of people, mostly in poor, rapidly-developing countries.”
Citation: Hughes, TP, Kerry, JT, Baird, AH,Connolly, SR, Dietzel, A, Eakin, CM, Heron, SF, Hoey, AS, Hoogenboom, MO, Liu, G, McWilliam, MJ, Pears, R., Pratchett, MS, Skirving, WJ, Stella, JS and Torda, G (2018). Global warming transforms coral reef assemblages. Naturedoi:10.1038/s41586-018-0041-2
Link to video and images here. Please credit as marked.
CONTACTS FOR INTERVIEWS
Prof Terry Hughes
Director, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0) 400 720 164 (AEST/UTC +10)
Prof Sean Connolly
ARC Centre of Excellence for Coral Reef Studies at James Cook University
Phone: +61 (0)7 4781 4242 (AEST/UTC +10)
Prof Andrew Baird
ARC Centre of Excellence for Coral Reef Studies at James Cook University
Phone: +61 (0) 400 289 770 (AEST/UTC +10)
C. Mark Eakin, Ph. D.
U.S. National Oceanic & Atmospheric Administration
College Park, MD U.S.A.
Phone: +1 (301) 502 8608 (EST/UTC -5)
FOR FURTHER INFORMATION
ARC Centre of Excellence for Coral Reef Studies at James Cook University
Phone: +61 (0)7 4781 6067, +61 (0) 428 785 895 (AEST/UTC +10)
Isolated coral reefs not immune to local human activity
Marine scientists at The University of Queensland’s Global Change Institute and the ARC Centre for Excellence in Coral Reef Studies have shown that local human activities negatively influence coral reef ecosystems in a series of complex interactions, some of which are poorly understood by science.
A detailed underwater study was undertaken at 26 sites across the Maldives, south-west of India, as part of a XL Catlin Seaview Survey.
The scientists investigated coral reef communities adjacent to human populations ranging from zero to more than 150,000 people.
PhD candidate Kristen Brown said although marine scientists already knew human activity placed pressure on coastal reef systems, the extent to which these impacts were translated to impacts on coral reefs via changes to coral-algal competition had rarely been investigated.
“We’ve demonstrated that local human populations have a strong influence on coral reefs,” Ms Brown said.
“Many people believe that isolated reefs, near relatively small human populations, are healthier.
“Our study, however, noted a decline in certain categories of reef-building corals and an increase in dead coral and filamentous algae on reefs adjacent the densest human communities.
“Importantly, this study only provides a snapshot into the interactive dynamics of coral and algae, and seasonal and long-term investigations should be implemented.
“The results of our study have implications for the effects of human populations on coral reef communities, drawing attention to how these drivers influence reef processes such as coral-algal competition,” Ms Brown said.
Associate Professor Sophie Dove from the ARC Centre for Excellence in Coral Reef Studies at The University of Queensland said understanding these changes was becoming more and more important as global changes due to ocean warming and acidification increase.
“Understanding how these changes interact is going to be increasingly important especially as we see more frequent impacts like that of the mass coral bleaching across the Maldives in 2016,” Dr Dove said.
“This may help coral reef managers target their interventions with better outcomes.”
XL Catlin Seaview Survey Chief Scientist Professor Ove Hoegh-Guldberg said the project had enabled some of the largest ecological measurements of reef health.
“Projects such as this will allow us to put down important baselines against which we can measure progress against goals,” he said.
The XL Catlin Seaview Survey began on the Great Barrier Reef in September 2012. Following successful Great Barrier Reef and Coral Sea surveys, the project was rolled out globally thanks to the ongoing support of founding sponsor, global insurance group – XL Catlin Group Limited.
In 2014 the major campaign area was the waters of South-East Asia, while in 2015 the reefs of the Indian Ocean, including the Maldives, were surveyed. The team has recorded additional survey areas, including the Galapagos Islands, and temperate water locations including Monaco and Sydney.
Who cares about the Great Barrier Reef? Many people, and according to a paper published today in the journal Proceedings of the National Academy of Sciences, some of the most passionately connected individuals can come from far away places, across the globe.
This is good news for the Reef. Blighted by bleaching, the Great Barrier Reef needs all the help it can get. The findings published today suggest that resource managers should draw on the support of the global community, not only locals living adjacent to the Reef, when engaging the public.
“It’s widely acknowledged that successful environmental management requires strong community engagement and support, but current approaches tend to only target locals. Our findings reveal that this view is too narrow,” says Dr Gurney.
For the many ecosystems that are increasingly affected by global-scale threats, such as climate change, these results are empowering.
“We need to look beyond our backyards for solutions to protect the Great Barrier Reef. Climate change, for example, is one of the biggest threats to the Reef and tackling it requires the support of the global community, not only those living close to the Reef.”
The study redefines the meaning of ‘community’ and, in doing so, identifies four new sub-communities, each with a different form of attachment to the Reef.
“Our study includes interviews with a diverse group of people – from fishers to international tourists. We found there are generally four types of communities who express ‘attachment’ for the Great Barrier Reef,” says co-author, Professor Neil Adger of the University of Exeter, U.K. “For example, we identified an ‘Armchair Enthusiast’ community. This group of individuals unexpectedly exhibits strong emotional bonds with the Reef, despite the fact that many live outside the Reef region and even outside of Australia.”
The authors say that the evidence suggests new types of bonds between people and iconic natural places are emerging that transcend traditional geographic boundaries. If targeted effectively, these bonds may be useful in building the transnational support required for successfully protecting the Reef.
“Modern-day problems, need modern-day solutions,” says co-author Dr Nadine Marshall of the Commonwealth Science and Industry Research Organisation (CSIRO). “Addressing global-scale threats requires engaging people from all over the world who care about the Reef through modern communication channels, such as social media.”
“Our results show that declines in the Reef’s health may affect people across the globe. So, we suggest that resource managers consider the untapped potential of emerging transnational communities to build broad public support for protecting the Reef.”
The paper “Redefining community based on place attachment in a connected world” is now available online.
Two-thirds of Great Barrier Reef hit by back-to-back mass coral bleaching
For the second time in just 12 months, scientists have recorded severe coral bleaching across huge tracts of the Great Barrier Reef after completing aerial surveys along its entire length. In 2016, bleaching was most severe in the northern third of the Reef, while one year on, the middle third has experienced the most intense coral bleaching.
“The combined impact of this back-to-back bleaching stretches for 1,500 km (900 miles), leaving only the southern third unscathed,” says Prof. Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies, who undertook the aerial surveys in both 2016 and 2017.
“The bleaching is caused by record-breaking temperatures driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions.”
The aerial surveys in 2017 covered more than 8,000 km (5,000 miles) and scored nearly 800 individual coral reefs closely matching the aerial surveys in 2016 that were carried out by the same two observers.
Dr. James Kerry, who also undertook the aerial surveys, explains further, “this is the fourth time the Great Barrier Reef has bleached severely – in 1998, 2002, 2016, and now in 2017. Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss.”
“It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016.”
Coupled with the 2017 mass bleaching event, Tropical Cyclone Debbie struck a corridor of the Great Barrier Reef at the end of March. The intense, slow-moving system was likely to have caused varying levels of damage along a path up to 100 km in width. Any cooling effects related to the cyclone are likely to be negligible in relation to the damage it caused, which unfortunately struck a section of the reef that had largely escaped the worst of the bleaching.
“Clearly the reef is struggling with multiple impacts,” explains Prof. Hughes. “Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years.”
“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.”
Key graphic 2016 -2017_GBRbleaching.jpg (high and low res versions available)
This composite map shows surveyed coral reefs in 2016 (left panel) and 2017 (right panel).
Not all data is shown, only reefs at either end of the bleaching spectrum: Red circles indicate reefs undergoing most severe bleaching (60% or more of visible corals bleaching) Green circles indicate reefs with no or only minimal bleaching (10% or less of corals bleaching).
Prof. Terry Hughes
Director, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)400 720 164, +61 (0)7 4781 4000
Dr. James Kerry
Senior Research Officer, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)407 475 576, +61 (0)7 4781 4823
Prof. Sean Connolly
Chief Investigator, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)7 4781 4242
Communications Manager, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)415 514 328
Note for editors
The two observers: Prof Terry Hughes and Dr. James Kerry work at the ARC Centre of Excellence for Coral Reef Studies at James Cook University in Townsville, Australia. The Centre for World University Rankings recently ranked this institution number 1 globally for Marine and Freshwater biology research.
The aerial survey techniques used in this study were employed consistently in all four bleaching events on the Great Barrier Reef: 1998, 2002, 2016 and 2017. They were backed up by extensive in-water research during the 2016 event and published in the peer-reviewed journal, Nature. (Link to journal)
Coral bleaching occurs when abnormal environmental conditions, like heightened sea temperatures, cause corals to expel tiny photosynthetic algae, called ‘zooxanthellae’. The loss of these colorful algae causes the corals to turn white, and bleach͛. Bleached corals can recover if the temperature drops and zooxanthellae are able to recolonise them, otherwise the coral may die.
In the six months following the peak of bleaching in March 2016, scientists measured on average 67% loss of corals in the northern 700 km section of the Great Barrier Reef, which was the worst impacted section in that year. An interactive map of images and video of aerial survey footage from the 2016 event can be found here.
Greater protection needed for Great Barrier Reef’s magnificent table corals
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.
Table corals are particularly vulnerable – and are the preferred meal of the Crown of Thorns Starfish. Credits: James Kerry
“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.”
Great Barrier Reef marine reserves combat coral disease
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.
Discarded fishing line caught on Great Barrier Reef coral. Image: Joleah Lamb.
“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.
Researchers survey coral on the Great Barrier Reef. Image: Joleah Lamb.
“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
Leading coral reef scientists say Australia could restore the Great Barrier Reef to its former glory through better policies that focus on science, protection and conservation.
In a paper published in the journal Nature Climate Change, the authors argue that all the stressors on the Reef need to be reduced for it to recover.
An Australian Government report into the state of the Great Barrier Reef found that its condition in 2014 was “poor and expected to further deteriorate in the future”. In the past 40 years, the Reef has lost more than half of its coral cover and there is growing concern about the future impacts of ocean acidification and climate change.
“We need to move beyond the gloom and doom to identify how the decline of the Great Barrier Reef can be turned around,” says co-author Professor Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU).
“Our paper shows that every major stressor on the Reef has been escalating for decades – more and more fishing, pollution, coastal development, dredging, and now for the past 20 years we’re also seeing the impacts of climate change.”
“We now have a very good handle on why the Great Barrier Reef is in trouble,” adds co-author, Jon Brodie from the Centre for Tropical Water and Aquatic Ecosystems Research at JCU.
“The challenge is to use that scientific knowledge to prevent further damage and give the Reef some breathing space that would allow it to recover.
Co-author, Jon Day, also from the ARC Centre for Coral Reef Studies at JCU says an obvious first step is to prevent unsustainable growth in each of the stressors to reduce their cumulative impact.
“If that means less dredging, less coal mining and more sustainable fishing, then that’s what Australia has to do. Business as usual is not an option because the values for which the Reef was listed as World Heritage are already deteriorating, and will only get worse unless a change in policy occurs.”
The authors say that as countries around the world move to curb global carbon emission, Australia has an opportunity to transition away from fossil fuels and to limit the development of huge coal ports alongside the Great Barrier Reef World Heritage Area.
“No-one is saying Queensland should not have ports – however, what we are saying is that all developments within, and adjacent to, the Great Barrier Reef need to be far more sustainable in the way that they are developed and operated, especially because they adjoin a World Heritage Area, “says Jon Day.
The authors agree that no one wants to see the Great Barrier Reef placed on UNESCO’s ‘World Heritage Area In-Danger’ list.
The Great Barrier Reef needs breathing space to recover. Image courtesy of State of Queensland
“The economic case for better protecting the Great Barrier Reef is very clear – it supports more than 60,000 jobs, mostly in Reef-related tourism,” says Professor Hughes.
The scientists have outlined a six-point plan they believe will restore the Great Barrier Reef, including;
A return to the former emphasis on conservation and protection of the Great Barrier Reef.
Australia taking a lead role in tackling climate change by transitioning away from fossil fuels.
Permanent legislative bans on dumping both capital and maintenance dredge spoil within the World Heritage area.
An overhaul of the environmental impact assessment process for new developments
The Great Barrier Reef Marine Park Authority (GBRMPA) reinstated as the agency responsible for all aspects of the Great Barrier Reef, including fishing and ports. A 50-year plan and adequate funding for the use of the catchment designed to reduce greenhouse gas emissions and agricultural run off.
Jon Brodie says Australia is starting to reduce runoff of nutrients, sediments and pesticides from land into the World Heritage Area, and is improving regulations for dumping capital dredge-spoil, but much more action is needed.
“These efforts are a welcome step in the right direction, but they will need much better resourcing in order to substantially reduce pressures on the World Heritage Area.”
The authors say the global community must make it clear that they want more effective policy action to ensure the Great Barrier Reef is restored for current and future generations.
“This paper raises awareness of the untapped opportunities to incorporate science into better policy to ensure we still have a magnificent Great Barrier Reef in the future,” Terry Hughes adds.
Twice the coral trout in Great Barrier Reef protected zones
Coral trout in protected ‘green zones’ are not only bigger and more abundant than those in fished ‘blue zones’ of the Great Barrier Reef Marine Park, but they are also better able to cope with cyclone damage, according to a long-term study published today in Current Biology.
Coral trout biomass has more than doubled since the 1980s in the green zones with most of the growth occurring since the 2004 rezoning. These and other changes identified by the study show that the green zones are contributing to the health of the Great Barrier Reef and that similar approaches may be beneficial for coral reefs around the world.
The joint project between the Australian Institute of Marine Science and the ARC Centre of Excellence for Coral Reef Studies at James Cook University combined a vast amount of information from underwater surveys carried out from 1983-2012, on reefs spread across approximately 150,000 km2 (more than 40 per cent) of the Marine Park.
The Marine Park was rezoned in 2004, and marine reserves where fishing is prohibited (called ‘green zones’ because of their colour on the zoning maps of the Marine Park), were expanded to cover about one-third of the total Park area. These green zones previously made up less than five percent of the Park.
The study demonstrated that the Reef’s network of green zones are yielding wide-scale population increases for coral trout, the primary target species of both the commercial and recreational sectors of the hook-line fishery.
It also found that reefs in green zones supported higher numbers of large, reproductively-mature coral trout, even after being damaged by cyclones—such as tropical cyclone Hamish, which hit the reef in 2009.
The findings provide compelling evidence that effective protection within green zone networks can play a critical role in conserving marine biodiversity and enhancing the sustainability of targeted fish populations.
“It’s heartening to know the green zones are working as we had expected,” said lead author Michael Emslie from AIMS.
“Among the world’s coral reefs, fishing on the Great Barrier Reef is relatively light but it has still reduced the number and average size of the few fish species that are taken by fishers. Data since the 1980s show that green zones have been effective in restoring numbers of coral trout to their former levels”.
David Williamson, a co-author from the ARC Centre of Excellence for Coral Reef Studies said “We expected to see some declines in coral trout biomass on reefs that remained open to fishing after the rezoning due to the increased concentration of fishing effort on those reefs, a so-called ‘squeeze effect’. Instead we found that coral trout biomass remained stable on fished reefs in areas that avoided the impacts of Cyclone Hamish, while it increased significantly on green zone reefs. Ultimately it has led to an overall increase in coral trout biomass across those regions. It’s a really positive result for both the fish and the fishery.”
The study suggests that the original Marine Park zoning plan that was put in place in the 1980s began to improve fish stocks, but that the expanded protection in 2004 greatly improved on this.
Hugh Sweatman, also of AIMS and co-author of the paper, said “Australia’s Great Barrier Reef Marine Park is looked upon as a benchmark for large-scale reserve networks around the world. Unlike many places where coral reefs are found, Australia is a developed country where fishing is fairly light and well regulated. Yet even here we see clear effects of fishing – the benefits of no-take reserves would be much more obvious where large coastal populations depend on reefs for their daily food, so fishing is more intense and everything is taken.
The details of our findings suggest that effectively protected networks of no-take reserves will help reef fishes cope with some present and future stresses, and assist in maintaining coral reef fish populations as we know them.”
A glimmer of hope for corals as baby reef-builders cope with acidifying oceans
While the threat of coral bleaching as a result of climate change poses a serious risk to the future of coral reefs world wide, new research has found that some baby corals may be able to cope with the negative effects of ocean acidification.
Ocean acidification, which is a direct consequence of increased atmospheric carbon dioxide levels, is expected to have a deleterious effect on many marine species over the next century.
An international team examining the impact of ocean acidification on coral has found that a key reef-building coral can, over a relatively short period of time, acclimate to a doubling of atmospheric carbon dioxide levels.
“Our aim was to explore the effect of a more acidic ocean on every gene in the coral genome,” says study lead author Dr Aurelie Moya, a molecular ecologist with the ARC Centre of Excellence for Coral Reef Studies at James Cook University.
The researchers exposed baby corals from the Great Barrier Reef to acidified seawater for varying lengths of time and investigated how they responded at a molecular level.
“We found that, whereas 3 days of exposure to high CO2 disrupts formation of the coral skeleton, within nine days the baby corals had re-adjusted their gene expression to pre-exposure levels. Longer exposure seems to be less detrimental to coral health than we had assumed based on shorter-term studies,” Dr Aurelie Moya says.
“These findings suggest that baby corals have the capacity to acclimate to elevated carbon dioxide.”
“We saw that within a few days juvenile coral adapted to CO2 levels double those experienced today with no obvious disruption to its life processes,” says study co-author, Professor David Miller, who leads the molecular biology group in the Coral CoE.
Professor Miller says the findings are particularly significant as they centred on staghorn coral.
“Staghorn corals are the key reef-building corals throughout the Pacific and Indian oceans. These are traditionally considered to have poor stress tolerance. So this work provides a glimmer of hope that coral reefs can attenuate the effects of ocean acidification.”
The research team examined tens of thousands of coral genes and was able to identify those that were responsible for enabling acclimation to high carbon dioxide.
Dr Moya says the study is an essential first step to better understand how reef-building corals adapt to environmental stress.
However both Dr Moya and Professor Miller remain cautious about the ability of corals to tolerate the combination of increased carbon dioxide and climate change.
“This study focused on one single stressor, ocean acidification, but we must keep in mind that the combination of several stressors, such as ocean acidification and warming could lead to larger impacts on baby corals,” Dr Moya says.
“The next step is to investigate the effect of combined stressors on corals’ gene expression.”
Rapid acclimation of juvenile corals to CO2-mediated acidification by up-regulation of HSP and Bcl-2 genes by Aurelie Moya, Lotte Huisman, Sylvain Foret, Jean-Pierre Gattuso, David Hayward, Eldon Ball and David Miller is published in the journal, Molecular Ecology.
History’s lesson reveals depth of fish catch decline
Scientists in Queensland have used historic media to measure the decline in Queensland’s pink snapper fishery, highlighting a drop of almost 90 per cent in catch rates since the 19th Century.
Researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at the University of Queensland and the Department of Agriculture Fisheries and Forestry examined thousands of newspaper articles dating back to1870 to reveal the historic catch rates for the iconic Queensland fishery.
“We found that 19th century recreational fishers would regularly catch hundreds of fish off the coast of Queensland, often in just a few hours of fishing,” says Dr Ruth Thurstan, a Research Fellow from the Coral CoE.
Combining historical data with statistical analyses allowed the researchers to calculate catch rates, which are the number of fish caught per hour fishing per day, for nearly 300 fishing trips between 1871 and 1939.
When the researchers compared the findings to contemporary fishing trips, they found that recent catch rates averaged just one-ninth of historical levels.
The old news articles have given researchers unparalleled insights into the history of the Queensland snapper fishery.
“When we searched through these old newspapers we were amazed by the level of detail they provided,” Dr Thurstan says.
“They give us a much better understanding of just how rich and productive this fishery used to be, as well as providing us with some fascinating insights into the development of offshore recreational fishing in Queensland.”
“Crucially, these newspaper articles place the modern day fishery into a longer-term perspective that isn’t available using only official records. This helps us understand the changes that have occurred in the fishery over time, and provides an additional piece of the puzzle for those managing this fishery today,” Dr Thurstan says.
Study co-author, Professor John Pandolfi, also from Coral CoE agrees.
“This is one of the most comprehensive perspectives on historical trends in catch rates for Australian fisheries ever compiled,” Professor Pandolfi says.
“We expect similar trends to be uncovered for other Australian fisheries.”
‘Nineteenth century narratives reveal historic catch rates for Australian snapper (Pagrus auratus)’ by Ruth H Thurstan, Alexander B Campbell and John M Pandolfi is published in the journal Fish and Fisheries.