Fade to grey – fish communities become duller as coral reefs die
James Cook University researchers have found brightly coloured fish are becoming increasingly rare as coral declines, with the phenomenon likely to get worse in the future.
Christopher Hemingson, a recent PhD graduate at JCU’s Centre of Excellence for Coral Reef Studies, led the research. He said over the past 30 years, human-induced stressors have caused profound changes to reefs – typically from the loss of corals.
“Reefs these days are becoming increasingly defined by non-coral substrates, especially turf algae. We wanted to investigate what effect this had on the kind of brightly-coloured fish people like and that attract tourists and visitors,” said Dr Hemingson.
The scientists used a new community-level measure of fish colouration and then explored the links between fish community colouration and the environment.
“We found that as the cover of structurally complex corals increases on a reef, so does the diversity and range of colours present on fishes living in and around them. But, as the cover of turf algae and dead coral rubble increases, the diversity of colours declines to a more generalised, uniform appearance,” said Dr Hemingson.
He said it was notable that fish community colouration declined significantly in the years following the 1998 global coral bleaching event – likely driven by the loss of branching corals.
“We found the structure of the sea floor appears to be very important in shaping fish colouration; more so than its composition (that is, its live coral cover). Having places to hide from predators may have allowed reef fishes to evolve unique colourations due to a reduced reliance on camouflage to avoid being eaten.
“Unfortunately, the types of corals most capable of surviving the immediate impacts of climate change (massive and boulder corals) are unlikely to provide these refuges. Fish communities on future reefs may very well be a duller version of their previous configurations, even if coral cover remains high,” said Dr Hemingson.
He said the loss of colourful fishes may not have a huge impact if assessing reefs through a strictly functional or ecological lens.
“But in a human context, loss of these colourful species may trigger a broad range of human responses, including grief.”
Hemingson CR, Mihalitsis M, Bellwood DR 2022. ‘Are fish communities on coral reefs becoming less colourful?’. Global Change Biology. DOI: 10.1111/gcb.16095
A selection of images can be used for media stories with credit to the photographer as stated in the file name. Please note these are for single use with this story only, not for any other story. No archival permissions are granted.
Researchers working with stakeholders in the Great Barrier Reef region have come up with ideas on how groups responsible for looking after the reef can operate more effectively when the next bleaching event arrives.
“Our collaborative research was squarely aimed at improving governance responses to extreme climate events in the GBR region and potentially other regions around the world,” said Dr Barnes.
The team interviewed 32 key individuals representing government, non-profits, research institutions, and the tourism, fishing, and aquaculture industries. The organisations deal with coral health, water quality, tourism and fishing.
“We wanted to understand catalysts and barriers to actions being taken across the region in response to coral bleaching, and participants’ hopes for future action,” said Dr Barnes.
The researchers found five major categories of activity for those involved in the wake of coral bleaching: assessing the scale and extent of bleaching, sharing information, communicating bleaching to the public, building local resilience, and addressing global threats.
“These actions were helped and hindered by a range of factors. For instance, some people were hindered in responding because information on the bleaching was scattered and not well integrated, there were conflicts and a lack of respect across certain groups, and community involvement was lacking in some cases” said co-author Amber Datta, a PhD candidate based at James Cook University and the University of Montana.
Working with a group of local stakeholders in the Great Barrier Reef, the team identified several ways to improve responses to future crises. These improvements include improving coordination, strengthening relationships between groups, and empowering and recognizing Traditional Owners as leaders of their Sea Country rather than stakeholders (see attached graphic for more details).
Dr. Barnes said “The new approaches should help to improve responses to future crisis events, but effective responses will depend on the willingness of diverse groups to negotiate a shared path forward, and ultimately on international and national commitments to address the root cause of climate change”.
Barnes M.L., Datta A., Morris S., Zethoven I. 2022. ‘Navigating climate crises in the Great Barrier Reef’. Global Environmental Change. DOI: 10.1016/j.gloenvcha.2022.102494
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: firstname.lastname@example.org
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: email@example.com
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: firstname.lastname@example.org
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Melissa Lyne (Eastern Australia Time Zone) Media Manager, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0) 415 514 328 Email: email@example.com
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
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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.
Researchers have found that when water temperatures heat up for corals, fish ‘tempers’ cool down, providing the first clear evidence of coral bleaching serving as a trigger for rapid change in reef fish behaviour.
Publishing in Nature Climate Change this week, researchers from Lancaster University and collaborating institutes including the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University show how the iconic butterflyfish, considered to be sensitive indicators of reef health, can offer an early warning sign that reef fish populations are in trouble.
The international team of researchers spent more than 600 hours underwater observing butterflyfish over a two-year period encompassing the unprecedented mass coral bleaching event of 2016.
Led by Dr. Sally Keith of Lancaster University, previously Center for Macroecology, Evolution and Climate, the team examined 17 reefs across the central Indo-Pacific in Japan, the Philippines, Indonesia and Christmas Island (Indian Ocean).
During the initial data collection, the researchers were unaware that the catastrophic bleaching event was on the horizon. Once underway, the researchers realised that this serendipitous ‘natural experiment’ placed them in a unique position to see how fish changed their behaviour in response to large-scale bleaching disturbance.
The team sprang into action to repeat their field observations, collecting a total of 5,259 encounters between individuals of 38 different butterflyfish species. Within a year after the bleaching event it was clear that, although the same number of butterflyfishes continued to reside on the reefs, they were behaving very differently.
“We observed that aggressive behaviour had decreased in butterflyfish by an average of two thirds, with the biggest drops observed on reefs where bleaching had killed off the most coral,” said Dr Keith. “We think this is because the most nutritious coral was also the most susceptible to bleaching, so the fish moved from a well-rounded diet to the equivalent of eating only lettuce leaves – it was only enough to survive rather than to thrive.”
Such changes in behaviour may well be the driver behind more obvious changes such as declining numbers of fish individuals and species. The finding has the potential to help explain the mechanism behind population declines in similarly disrupted ecosystems around the world.
Co-author Dr. Erika Woolsey of Stanford University said: “By monitoring behaviour, we might get an early warning sign of bigger things to come.”
“Our work highlights that animals can adjust to catastrophic events in the short term through flexible behaviour, but these changes may not be sustainable in the longer-term,” added co-author Prof Andrew Baird of Coral CoE at James Cook University.
The paper “Synchronous behavioural shifts in reef fishes linked to mass coral bleaching” is available online here.
An international team of researchers has mapped Nemo’s genome, providing the research community with an invaluable resource to decode the response of fish to environmental changes, including climate change.
“For example, the clownfish is a model for studying sex change in fishes. It has also helped us understand patterns of larval dispersal in reef fishes and it’s the first fish species for which it was demonstrated that predator avoidance behaviour could be impaired by ocean acidification.”
The team used state-of-the-art technology to sequence the clownfish’s genome. Their genomic and transcriptomic data is now available via the Nemo Genome DB database.
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.
Dr Juan Ortiz, lead author from the Australian Institute of Marine Sciences and UQ’s School of Biological Sciences, said that during this time, average coral recovery rates showed a six-fold decline across the Great Barrier Reef.
“This is the first time a decline in recovery rate of this magnitude has been identified in coral reefs,” he said.
The decline is driven by a combination of the legacy effect of acute disturbances like coral bleaching and cyclones and the ongoing effect of chronic pressures like poor water quality and climate change.
Professor Peter Mumby of Coral CoE at The University of Queensland, said that this was serious cause for concern, particularly given the accelerating impacts of climate change on reefs, but it is important to stress that not all reefs are failing.
“I believe there is scope for management to help remedy the situation,” he said.
“Our results indicate that coral recovery is sensitive to water quality, and is suppressed for several years following powerful cyclones.
“Some reefs could improve their recovery ability if the quality of the water entering the reef is actively improved.”
“While there was variability among regions, the decline in recovery rate was consistent in all coral types included in the study,” he said.
Dr Ortiz said that the frequency of acute disturbances was predicted to increase, making careful management key.
“The future of the Great Barrier Reef is threatened without further local management to reduce chronic disturbances and support recovery, and strong global action to limit the effect of climate change.”
The research, based on long-term monitoring data collected by AIMS on more than 90 reefs across the Great Barrier Reef Marine Park, is published in the journal Science Advances (DOI: 10.1126/sciadv.aar6127).
Ortiz, J-C, Wolff, NH, Anthony, KRN, Devlin, M, Lewis S and Mumby, PJ (2018) Impaired recovery of the Great Barrier Reef under cumulative stress. Science Advances. Vol. 4, no. 7,DOI: 10.1126/sciadv.aar6127
Coral reefs losing ability to keep pace with sea-level rise
Many coral reefs will be unable to keep growing fast enough to keep up with rising sea levels, leaving tropical coastlines and low-lying islands exposed to increased erosion and flooding risk, new research suggests.
The growth of coral reefs is strongly influenced by the amount and types of coral living on the reef surface. This growth is now being hampered by combinations of coral disease, deteriorating water quality and fishing pressure, along with severe impacts from “coral bleaching” caused by climate change.
“For many reefs across the Caribbean and Indian Ocean regions, where the study focused, rates of growth are slowing due to coral reef degradation,” said lead author Professor Chris Perry, of the University of Exeter.
“Meanwhile, rates of sea-level rise are increasing – and our results suggest reefs will be unable to keep up. As a result, water depths above most reefs will increase rapidly through this century.”
“Even under modest climate change prediction scenarios (RCP4.5) only about 3% of Indian Ocean reefs will be able to track local sea-level rise projections without sustained ecological recovery, whilst under continued high emission scenarios (RCP8.5) most reefs will experience water depth increases in excess of half a metre,” added co-author Dr Aimée Slangen of NIOZ, Royal Netherlands Institute for Sea Research.
“This is now of critical concern because reefs play a key role as natural sea defences by limiting coastal wave energy exposure,” commented Professor Nick Graham, of Lancaster University, another co-author of the study.
“Efforts to tackle climate change must therefore be coupled with careful management of fishing and water quality protection to prevent widespread submergence through this century.”
The researchers calculated growth rates for more than 200 tropical western Atlantic and Indian Ocean reefs.
“Now more than ever, we must limit global greenhouse gas emissions. Our predictions, even under the best case scenarios, suggest that by 2100 the inundation of reefs will expose coastal communities to significant threats of shoreline change,” said co-author Professor Peter Mumby of Coral CoE at The University of Queensland. “Healthier coral reefs will reduce the rate of seawater inundation.”
Professor Perry concluded: “The most worrying end-point scenario in this respect is that if predictions of increasing bleaching frequency are realised, many reefs may become locked into permanent low growth rate states, leading to more submergence under all future sea-level rise scenarios.”
The paper, published in the journal Nature, is entitled: “Loss of coral reef growth capacity to track sea-level rise under climate change.”
Citation: Perry, CT, Lorenzo, A-F, Graham, NAJ, Mumby, PJ, Macdonald, C et al. (2018). Loss of coral reef growth capacity to track future increases in sea level. Nature, 1476-4687 DOI – 10.1038/s41586-018-0194-z
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Study finds marine protected areas can help coral reefs
Reports in recent years that marine protected areas (MPAs) aren’t effective in saving coral reefs from the damaging effects of global climate change have led some to argue that such expensive interventions are futile. But a study that spanned 700 kilometers of the eastern Caribbean reveals that MPAs can, indeed, help coral reefs.
Local fisheries management resulted in a 62 percent increase in the density of young corals, which improves the ecosystem’s ability to recover from major impacts like hurricanes and coral bleaching, according to the team’s findings, published in Science Advances, a journal of the American Association for the Advancement of Science.
“The idea behind MPAs is that, by reducing fishing pressure, you increase the number of seaweed-eating fish, and they decrease the amount of harmful seaweed, which makes it easier for baby corals to get started and thrive on the reef. But coral reefs are complicated, and lots of other things can affect fish numbers, their ability to control the growth of algae and the ability of corals to take advantage of this.”
“Taking field measurements on coral reefs is time consuming, so many researchers are forced to take shortcuts and use simple, widely available data to analyse how reefs respond to protection,” says study co-author Professor Peter Mumby of Coral CoE.
“While it sounds obvious, we show that our ability to detect the benefits of MPAs on corals improves dramatically when you take more detailed measurements,” Prof Mumby says.
“For example, a simple option is to count the number of herbivorous fishes. But if, instead, you estimate how intensively these fishes feed, you obtain a much clearer and compelling insight.”
There is no management panacea for any ecosystem, and especially not for coral reefs, Prof Steneck notes.
“Certainly, stresses on coral reefs from climate and atmospheric changes are serious and beyond direct management control. However, we suggest that local management measures can bolster the recovery of corals after damaging events and, eventually, improve their overall condition.”
Doug Rasher of Bigelow Laboratory for Ocean Science in East Boothbay, Maine, adds: “What we show is that relatively small changes can nudge this ecosystem toward one that can maintain and sustain itself.”
The research team, which also included researchers from James Cook University (Australia) and RARE (USA), concludes that the best way to measure the effectiveness of reef conservation is by using a suite of metrics, including the number of fish, amount of seaweed and the number of baby corals, rather than just one indicator of reef health.
Thanks to mom and dad, baby reef fish may have what it takes to adjust to hotter oceans.
In a rapidly changing climate, the decline of animal populations is a very real concern. Today, an international team of researchers report new evidence of reef fish adjusting to global warming conditions at the genetic level.
Epigenetic change refers to chemical modifications in the DNA that signals genes to be switched on or off. A range of factors, including disease, famine, or in the case of this research, heat stress, can stimulate these subtle changes.
In this study, when both parent and offspring experienced the same elevated water temperatures, responsive changes in their epigenome, via selective DNA methylation, were observed that enhanced the next generation’s ability to cope with the new, warmer temperatures.
“We reared spiny chromis damselfish, a common Indo-Pacific reef fish, for two generations under three different water temperatures, up to 3 degrees Celsius warmer than current-day ocean temperatures,” explained co-author Prof Timothy Ravasi of KAUST.
“The next generation appeared to be advantaged by parental exposure to elevated temperatures. The offspring’s altered gene expression, also referred to as ‘acclimation,’ allowed them to maximise oxygen consumption and energy use.”
“Acclimation may buffer populations against the impacts of rapid environmental change and provide time for genetic adaptation to catch up over the longer term,” said Prof Munday.
The authors of the study note that while this is good news for reef fish, the decline of their coral habitat, as a result of climate change, will continue to be an overriding concern for their survival.
The paper “The epigenetic landscape of transgenerational acclimation to ocean warming” is published in Nature Climate Change.
Citation: Ryu, T, Veilleux, H, Donelson, JM, Munday, PL, and Ravasi, T (2018). The epigenetic landscape of transgenerational acclimation to ocean warming. Nature Climate Change. DOI: 10.1038/s41558-018-0159-0
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The study was conducted by researchers at James Cook University and Lancaster University, U.K., who examined 16 reefs off Lizard Island, in the northern section of the GBR. The quantity and types of coral and fish species were surveyed before, during and after the 2016 mass bleaching event caused by a global heatwave.
“The widespread impacts of heat stress on corals have been the subject of much discussion both within and outside the research community. We are learning that some corals are more sensitive to heat-stress than others, but reef fishes also vary in their response to these disturbances,” said lead author Ms Richardson.
“Fish assemblages are significantly impacted by loss of coral cover as a result of bleaching events, and some fishes are more sensitive than others,” said co-author Prof Nick Graham of Lancaster University.
The loss of corals affected some types of fish more than others. Following the bleaching event, researchers recorded a sharp drop in the diversity of fish communities as the mix or species changed.
Fish that are highly dependent on branching corals, such as butterflyfish, declined the most.
“Also known as ‘biotic homogenisation,’ this tendency towards individual and community similarity is increasingly considered one of the most pressing, but largely unrecognised, biodiversity crises faced globally.”
Citation: Richardson, LE, Graham, NAJ, Pratchett, MS, Eurich, JG, and Hoey, AS (2018). Mass coral bleaching causes biotic homogenization of reef fish assemblages. Global Change Biology, doi:10.1111/gcb.14119
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Coral reefs are in trouble – how can people adapt?
An international team of scientists has developed a strategy to boost people’s ability to adapt to climate change, revealed in a new study published today in the prestigious journal, Nature Climate Change.
A group of social scientists from the USA, Australia, UK, and Chile, led by Prof. Cinner, have pooled their experience, and lessons from hundreds of research and development projects, to highlight five keys ways to build up the adaptive capacity of people living in the coastal tropics. These include:
1. Ensuring that people have the assets to draw upon in times of need. These assets can include household wealth or public goods such as health services, but they need to be developed in ways that don’t exacerbate existing inequalities;
2. Providing the flexibility to change. “Having some flexibility can enable people to minimise losses or even take advantage of climate-related change,” said Prof. Eddie Allison from the University of Washington, USA. “For example, fishers might need to change fishing grounds or target new species.”
3. Learning about climate change and adaptation options. “People need to learn about new techniques and strategies that can help them cope with changing circumstances,” said Prof. Katrina Brown at the University of Exeter, UK.
4. Investing in social relationships. “The formal and informal relationships that people have with each other and their communities can help them deal with change by providing social support and access to both knowledge and resources,” said Prof. Cinner.
5. Empowering people to have a say in what happens to them. “We also need to ensure that people have the ability to determine what is right for them,” said Prof. Brown.
The paper “Building adaptive capacity to climate change in tropical coastal communities,” will be published in the February 1 issue of Nature Climate Change, and is available online today.
Citation: Cinner JE, Adger WN, Allison EH, Barnes ML, Brown K, Cohen PJ, Gelcich S, Hicks CC, Hughes TP, Lau J, Marshall NA, Morrison TH (2018) Building adaptive capacity to climate change in tropical coastal communities. Nature Climate Change 8:117-123
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Study urges global-change researchers to embrace variability
Scientists typically make every effort to keep all factors but one constant when doing an experiment. Global-change scientists might move a coral from a reef to an aquarium whose water is held 1°C higher to test the effects of the ocean warming predicted for the end of the century. Or they might decrease the water’s pH by 0.4 units to study the effects of ocean acidification.
But a new review article presents evidence that argues for a more nuanced approach to the design of these experiments–one that acknowledges and purposefully incorporates the variability inherent in nature.
The article, in the latest issue of Current Climate Change Reports, focuses on studies examining how ocean warming and acidification might affect corals and coralline algae. Lead author Emily Rivest of William & Mary’s Virginia Institute of Marine Science (VIMS) says its findings are also likely applicable to other foundational reef species such as oysters.
“The range of pH and temperature that some organisms experience on a daily basis exceeds the changes we expect to see in the global ocean by the end of the century,” notes Rivest, an assistant professor at VIMS. “But we don’t really know how this variability affects their physiology and their ability to respond to future change. The papers we reviewed suggest this variability is important, and we need to incorporate it into our experiments.”
Indeed, there’s a growing consensus that the degree of variability in temperature and pH an organism faces in its current environment will likely influence its response to future warming and acidification. For instance, a coral growing in a back-reef lagoon–whose restricted waters may warm drastically each afternoon under the blazing sun–may be less susceptible to long-term warming than a coral growing in the more open, temperate waters of the reef face. The same may hold true for entire species or populations of warmth-adapted corals.
The experiments that incorporated variability fell into two categories. “One type was studies where you collect corals from a high-variability site and a low-variability site and see how they do under controlled laboratory conditions,” says Rivest. “If the variability is important in shaping their response to environmental change, then their response will depend on the site they are from.”
The second type “looked at the variability within laboratory treatments–taking corals into the lab and raising them under constant or variable conditions, then providing them with an additional stress and seeing if the variability they experienced in the lab influences their response to that stress.”
Rivest and her colleagues found that incorporating variability into an experiment’s design produced ambiguous and intriguing results.
“Corals from habitats with more temperature variability generally exhibit greater thermotolerance,” says Rivest, “but the effects of past pH variability are less clear.” On the other hand, she says, “In laboratory studies, pH variability often limited the effects of ocean acidification, but the effects of temperature variability on responses to warming were equivocal.”
Rivest, Comeau, and Cornwall say their findings warrant additional research. “We want our paper to signal the start of a new era in studies of how climate change affects foundation species,” says Rivest. “We really need to consider an animal’s current environment as a starting point for how it will respond in the future–we want this to be a point of discussion in our field, for how we should be designing experiments and thinking about these questions moving forward.”
The team says their findings could also lead to practical applications. “If we know better how environmental variability affects the ability of animals to tolerate future environmental change, then we can think about it in a restoration and conservation context,” says Rivest. “For example, if you target a reef for restoration, we could start a training program for corals where you culture them in the lab under variable conditions so they would be ready to perform well out in the reef environment.” This approach is already being applied at the Hawai’i Institute of Marine Biology, the Australian Institute of Marine Science, and other research labs worldwide.
The paper “The Role of Natural Variability in Shaping the Response of Coral Reef Organisms to Climate Change” is now available online.
CONTACTS FOR INTERVIEWS
Mr David Malmquist
Virginia Institute of Marine Science, VA USA
P: +1 804-684-7011
Dr Chris Cornwall
University of Western Australia, Perth Australia
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Climate’s profound impact on marine biodiversity
New research into the impact of climate change has found that warming oceans will cause profound changes in the global distribution of marine biodiversity.
In a study published in the journal Nature Climate Change an international research team modelled the impacts of a changing climate on the distribution of almost 13 thousand marine species, more than twelve times as many species as previously studied.
The study found that a rapidly warming climate would cause many species to expand into new regions, which would impact on native species, while others with restricted ranges, particularly those around the tropics, are more likely to face extinction.
Professor John Pandolfi from the ARC Centre of Excellence for Coral Reef Studies at the University of Queensland says global patterns of species richness will change significantly, with considerable regional variability.
“This study was particularly useful because it not only gave us hope that species have the potential to track and follow changing climates but it also gave us cause for concern, particularly in the tropics, where strong biodiversity losses were predicted,” says Professor Pandolfi.
“This is especially worrying, and highly germane to Australia’s coral reefs, because complementary studies have shown high levels of extinction risk in tropical biotas, where localized human impacts as well as climate change have resulted in substantial degradation.”
To model the projected impact of climate change on marine biodiversity, the researchers used climate-velocity trajectories, a measurement which combines the rate and direction of movement of ocean temperature bands over time, together with information about thermal tolerance and habitat preference.
They say the analysis provides the simplest expectation for the future distribution of marine biodiversity, showing recurring spatial patterns of high rates of species invasions coupled with local extinctions.
Professor Elvira Poloczanska from CSIRO says, “This study shows how climate change will mix up biodiversity patterns in the ocean. Ecological communities which are currently distinct, will become more similar to each other in many regions by the end of the century”
Dr David Schoeman from the University of the Sunshine Coast says the model suggests that there is still time to act to prevent major climate-related extinctions outside of the topics.
“Results under a scenario in which we start actively mitigating climate change over the next few decades indicates substantially fewer extinctions than results from a business-as-usual scenario,” Dr Schoeman says.
“Possibly more worrying, though, is the imminent development of novel biotic assemblages. We have little idea of how these new combinations of species in ocean systems around the world will affect ecosystem services, like fisheries. We should be prioritising ecological research aimed specifically at addressing this question.”
Professor Pandolfi warns the resultant novel combinations of resident and migrant species will present unprecedented challenges for conservation planning.
“Above all, this study shows the broad geographic connections of the effects of climate change – conservation efforts need to be facilitated by cooperation among countries to have any real chance of combating the potentially severe biodiversity losses that a changing climate might impose.”
The paper, Climate velocity and the future of global redistribution of marine biodiversity by Jorge Garcia Molinos, Benjamin S. Halpern, David S. Schoeman, Christopher J. Brown, Wolfgang Kiessling, Pippa J. Moore, John M. Pandolfi, Elvira S. Poloczanska, Anthony J. Richardson and Michael T. Burrows is published in the journal Nature Climate Change http://dx.doi.org/10.1038/nclimate2769
Why offspring cope better with climate change – it’s all in the genes!
In a world first study, researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University have unlocked the genetic mystery of why some species are able to adjust to warming oceans.
Adaptation to warmer water happens in the genes. Image: H. Veilleux
In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how reef fish’s genes responded after several generations living at higher temperatures.
“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE.
“But until now, how they do this has been a mystery.”
Using cutting-edge molecular tools the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures.
“By understanding the function of these genes we can understand how fish cope with higher temperatures,” explains Dr Veilleux.
“We found that shifts in energy production are key to maintaining performance at high temperatures,” says Dr Veilleux.
“Immune and stress responses also helped fish cope with warmer water.”
The project involved rearing coral reef fish at different temperatures for multiple generations in purpose-built facilities at James Cook University.
“We then used state-of-the-art genetic methods to examine gene function in the fish,” says Dr Tim Ravasi from KAUST.
“ By matching gene expression to metabolic performance of the fish we were able to identify which genes make acclimation to higher temperatures possible,” adds Professor Philip Munday from the Coral CoE.
The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future.
“Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says.
Molecular processes of transgenerational acclimation to a warming ocean, by Heather D. Veilleux, Taewoo Ryu, Jennifer M. Donelson, Lynne van Herwerden, Loqmane Seridi, Yanal Ghosheh, Michael L. Berumen, William Leggat, Timothy Ravasi and Philip Munday is published in the journal Nature Climate Change. http://dx.doi.org/10.1038/nclimate2724
Professor Timothy Ravasi – firstname.lastname@example.org +966-544700067
KAUST Environmental Epigenetic Program (KEEP) and the Red Sea Research Center
Ocean near tipping point scientists warn
International ocean scientists have issued a blunt warning to world leaders ahead of the November 2015 climate change negotiations in Paris (COP21).
In a paper published in the journal Science, the experts argue that any new global climate agreement must begin to minimise the mounting toll on the world’s oceans to prevent irreversible damage.
ARC Centre of Excellence for Coral Reef Studies Deputy Director and Director of the UQ Global Change Institute Professor Ove Hoegh-Guldberg said the 2009 negotiations in Copenhagen had underestimated the likely impact of climate change on oceans, and a new more intense focus on oceans was urgently needed.
“There’s compelling evidence that increases in the atmospheric concentration of carbon dioxide and other greenhouse gases are already resulting in fundamental changes to the physical, chemical, and biological properties of our planet,” Professor Hoegh-Guldberg said.
“This is posing growing risks to human well-being as well as threatening key industries.
“However, solutions are still possible if we act decisively in Paris,” he said.
French National Center for Scientific Research senior scientist Dr Jean-Pierre Gattuso also voiced his great concern.
“The oceans have been minimally considered at previous climate negotiations. Our study provides compelling arguments for a radical change at COP21,” Dr Gattuso said.
The paper draws on an extensive scientific assessment of the impact of climate change on the world’s oceans completed last year for the Intergovernmental Panel on Climate Change (IPCC).
Professor Hoegh-Guldberg was co-ordinating lead author for the Oceans section of that United Nations study.
He said the chemical and physical conditions of the ocean were changing at rates which were, in some cases, faster than any seen over the past 65 million years.
“There is also high confidence that many marine organisms and their communities and ecosystems are undergoing fundamental change as the world‘s oceans warm, acidify and lose oxygen,” he said.
“While deep cuts in greenhouse gas emissions are a must, we must also agree to rapidly rebuild the resilience of ecosystems and people against the rising tide of change.
“We must work on the urgent issues of adapting to rapid sea level rise, transforming fisheries and the impacts of increasingly strong storms – all of which will help to reduce non-climate stresses on ecosystems and build resilience to climate change-related impacts.”
The Science paper warns that policy options for addressing ocean impacts (mitigate, protect, repair, adapt) are narrowing as the ocean warms and acidifies.
The 21st Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21) will herald a week of climate negotiations in Paris on 30 November.
The Oceans 2015 Initiative was launched to provide COP21 negotiators with key information on what future ocean will look like. The initiative is led by the French National Center for Scientific Research (CNRS), Sorbonne University (Paris) and the French Institute for Sustainable Development and International Relations (IDDRI), and is supported by the Prince Albert II of Monaco Foundation, the Ocean Acidification International Coordination Centre of the International Atomic Energy Agency, the BNP Paribas Foundation and the Monégasque Association for Ocean Acidification.
Australia – Professor Ove Hoegh-Guldberg, (+61 7) 3443 3112, email@example.com, Skype ‘Hoegh-Guldberg’, GCI Communications 0438 285 283; France – Dr Jean-Pierre Gattuso, (+33 4) 93 76 38 59, firstname.lastname@example.org.
Big waves are energetically costly for fish, and there are more big waves than ever. The good news is that fish might be able to adapt.
“There has been a lot of recent work in oceanography documenting the fact that waves are becoming more frequent and more intense due to climate change,” says Mr Dominique Roche, PhD candidate from the Research School of Biology. “The habitats that fish live in are changing.”
“This is not a localised problem, but something that is documented globally,” adds Ms Sandra Binning, also a PhD candidate in the Research School of Biology.
Mr Roche and Ms Binning are co-authors on a study documenting the energy it takes for fish to swim through large, intense waves. Specifically, they focused on fish that swim with their arm, or pectoral fins, which are very common on both rocky and coral reefs.
“By controlling water flow in an experimental chamber with the help of a computer, we were able to replicate oscillations in the water flow like in a wave pool,” explains Mr Roche.
“We looked at how much energy the fish consumed while swimming without waves, in conditions with small waves, and in conditions with large waves. The idea was to compare the amount of energy that fish consume while swimming in these three conditions when their average swimming speed was exactly the same.”
Mr Roche and Ms Binning found that it’s a lot more energetically demanding for fish to deal with large fluctuations in water speed and wave height.
“It’s harder to constantly switch speeds than it is to remain at a constant speed, like a runner changing between running and a walking during interval training versus a steady jog. Well, it’s the same for swimming fish,” says Mr Roche.
“Things could get tough for fish in windy, exposed habitats if waves get stronger with changing climate. But there may be a silver lining,” says Ms Binning.
“In the swim chamber, when the water flow increased, fish had to beat their fins faster to keep up. But when the water flow slowed down, some fish took advantage and rode the wave. Essentially, rather than beating their fins frantically, these fish used the momentum that they had gained while speeding up to glide and save energy.
“This means that some individuals are better at dealing with waves than others, and that there is hope for populations to adapt their swimming behavior to potentially changing conditions in the future,” concludes Mr Roche.
Their research was recently published in the Journal of Experimental Biology. A copy, plus images and video, can be obtained from the ANU Media Office.
For further information contact:
Mr Dominque Roche, PhD Candidate, ARC Centre of Excellence for Coral Reef Studies and ANU, +1-514-482-1805, email@example.com, Skype: dominique.roche
Ms Sandra Binning, PhD Candidate, ARC Centre of Excellence for Coral Reef Studies and ANU, +1-514-291-6005, firstname.lastname@example.org
Please note that Roche and Binning are currently in Montreal, Canada. The time difference is -16hrs.
For media assistance, please call the ANU media hotline: (02) 6125 7979
Marine reserves ‘must adapt to climate change’
Australia can be a world leader in designing marine reserves that keep pace with changes in the climate and human activity and still successfully protect their sea life, a leading marine scientist said today.
Professor Bob Pressey of the ARC Centre of Excellence for Coral Reef Studies and James Cook University told the Australian Academy of Science’s Earth System Outlook Conference in Canberra that developing marine protected areas that can absorb the impact of warming oceans, storms and flood events from the land is ‘doable’.
His comments come as government leaders from around the world meet in Doha for the United Nation’s Climate Conference (Nov 26-Dec7) to try to impart new momentum to stalled efforts to fight climate change.
“The challenge we face is that a marine reserve or park usually covers a fixed geographical area – but bodies of hot ocean water, storms and flood runoff move unpredictably in space and time,” Prof. Pressey explains.
“This means either that the reserve boundaries may have to move as things change – or else they need to located and designed carefully. If they’re fixed reserves, they need to be placed away from frequent disturbances, or configured so that individual disturbance events don’t affect them entirely. That way, we can include areas where sea life may take refuge to be safe from the impact.”
Prof. Pressey says that 25 years of ocean temperature data had given scientists a much better understanding of where on the Great Barrier Reef the impacts of coral bleaching were likely to be most severe – and where corals appeared to be consistently safe from high temperatures.
“While we can’t easily predict when an episode of hot ocean water will move in, we can definitely see some areas which appear to avoid the harshest effects over time – whether because they are shielded in some way or cooled by cold upwelling currents.
“This gives us the ability to design marine protected areas for the GBR and elsewhere that are resilient over time, no matter what changes take place.
“On top of the sea temperatures, we can also potentially factor in historical data from cyclone tracks and flood plumes, or bodies of floodwater with high loads of sediment. By superimposing all these we can identify and be sure to protect those special areas of the reef which are naturally resilient and which can recharge other areas that may be damaged.”
In a separate paper to the conference Professor Geoff Jones of CoECRS and JCU said there was now plenty of evidence that marine reserves work – not only by replenishing fish populations in no-take zones, but also by recharging fish populations in areas open to fishing.
“Our a new application of genetic parentage analysis shows protected populations of coral trout are helping to sustain juvenile recruitment in both reserves and in fished populations,” he says.
“At the Keppel islands, local reserves (about 30% of the reef area) now account for about 60% of juvenile recruitment of coral trout in the region, both in reserves and fished areas. Hence, reserves do have the potential to conserve coral trout and sustain fisheries in the long-term.”
However Prof. Jones cautioned that coral trout populations could still suffer if coral cover on the reef declined – and added that size and catch limits would still be needed in areas outside the reserve to ensure there were enough adult fish to sustain the fishery.
“While no take zones are extremely valuable, we need both them and more traditional fisheries management practices to ensure a healthy fish population on the Great Barrier Reef into the future,” he concluded.
Professor Bob Pressey, CoECRS and JCU +61 7 4781 6194 or +61 0418 387 681
Professor Geoff Jones, CoECRS and JCU, + 61 7 4781 4559 or +61 0435 065 296
Jenny Lappin, CoECRS, +61 7 4781 4222
Jim O’Brien, James Cook University Media Office, +61 7 4781 4822 or +61 0418 892 449
Mona Akbari, Media Officer AAS, ph +61 2 6201 9452