1

People and ecosystems

Understanding of the links between coral reef ecosystems, the goods and services they provide to people, and the wellbeing of human societies.

2

Ecosystem dynamics: past, present and future

Examining the multi-scale dynamics of reefs, from population dynamics to macroevolution

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Responding to a changing world

Advancing the fundamental understanding of the key processes underpinning reef resilience.

Coral Bleaching

Coral Bleaching

Coral Reef Studies

ARC Centre of Excellence for Coral Reef Studies
James Cook University Townsville
Queensland 4811 Australia

Phone: 61 7 4781 4000
Email: info@coralcoe.org.au

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A new study suggests sharks will need to adapt, move or die as climate change could soon render their nurseries uninhabitable.

Baby sharks rely on coastal nursery-like spaces such as shallow lagoons and mangroves for food as well as protection from predators. But they also need to be robust enough to cope with the challenging conditions these environments throw at them—conditions that may soon become unbearable in a warming world.

“In shallow coastal habitats, baby sharks already have to tolerate the strain of high temperatures,” said the study’s lead author Dr Ian Bouyoucos, from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (Coral CoE at JCU).

“The temperatures can also fluctuate dramatically on a daily basis. It’s the constant change that makes these environments ‘extreme’.”

Dr Bouyoucos said nursery areas are important for sustaining the local shark populations by serving as ‘safe havens’ for newborns and juveniles to learn critical survival and foraging skills. But the impacts of climate change are increasingly becoming a problem for their survival.

“We don’t know if sharks can adapt and can continue to use these important habitats early in life, or whether they will be able to find new nurseries, or whether populations will die off” he said.

Co-author Associate Professor Jodie Rummer, also from Coral CoE at JCU, says this is a case of adapt, move or die.

“Heatwaves due to climate change are becoming more frequent and severe, and lasting longer with climate change,” Dr Rummer said.

She said more work is needed to find current tolerance limits for newborn sharks to survive and thrive in shallow, warm nursery habitats.

“The temperature thresholds that limit their performance today can help us predict how future populations might fare as the waters continue to warm with climate change,” she said.

“But adaptation—changes in DNA over generations to accommodate new conditions—may not be possible. This is because sharks are slow to reach sexual maturity compared to most other fishes and do not reproduce as often or have as many babies. Therefore, not enough generations can go by fast enough to keep pace with the rate at which we—humans—are changing their habitats.”

Dr Rummer said there was a possibility newborn sharks could move to new nursery-like areas that are not as warm.

“Or, we might just see these shark populations disappear,” she said.

“This is a real risk. We know sharks are tolerating a lot already. The oceans, their habitats, are getting warmer, lower in oxygen, and lower in pH with climate change.”

As predators, sharks are essential for healthy ocean ecosystems. Without predators, whole ecosystems can collapse.

“We need to keep studying and protecting sharks,” Dr Bouyoucos said.

“Our sharks, ecosystems, and our futures all depend on us urgently cutting greenhouse gas emissions to curb climate change.”

PAPER

Bouyoucos I, Simpfendorfer C, Planes S, Schwieterman G, Weideli O, Rummer J. 2022. ‘Thermally insensitive physiological performance allows neonatal sharks to use coastal habitats as nursery areas’. Marine Ecology Progress Series. DOI: 10.3354/meps13941

IMAGES

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.

CONTACT

Ian Bouyoucos (Manitoba, CST)
E: ian.bouyoucos@umanitoba.ca

Jodie Rummer (Townsville, AEST)
P: +61 (0)439 166 171
E: jodie.rummer@jcu.edu.au

A massive study of nearly 1800 tropical coral reefs around the world has found that marine reserves near heavily populated areas struggle to do their job – but are a vast improvement over having no protection at all.

Professor Josh Cinner from the ARC Centre of Excellence for Coral Reef Studies at James Cook University led a team of 37 scientists examining the effectiveness of different reef conservation strategies.

“Fish stocks were extremely depleted on reefs that were accessible to large human populations. Compared to marine reserves far from these human pressures, reserves near high human pressure had only a quarter of the fish and were a hundred times less likely to have top predators such as sharks,” said Professor Cinner.

The scientists also studied how differences in ecological conditions between marine reserves, where fishing is prohibited, and places open to fishing changed as human pressures increased. “This tells you where you can get the biggest impact from implementing conservation,” said Professor Cinner.

“A really novel and exciting part of our study found that the greatest difference in fish biomass between marine reserves and places open to fishing was in locations with medium to high human pressure. This means that, for most fisheries species, marine reserves have the biggest bang where human pressures are medium to high,” he said.

For example, on reefs subject to high human pressure, marine reserves had five times more fish than openly fished reefs – a benefit that can spillover into the depleted fisheries in surrounding areas.

“However, top predators such as sharks were a different kettle of fish,” said co-author Dr Aaron MacNeil from Dalhousie University.

The scientists encountered top predators on less than 30% of their surveys conducted all across the globe, and very rarely in locations where human pressures were high.

“You’d have to do about 200 dives to see a top predator in reserves with the highest human pressure. But where human pressure was low, you’d be likely to see predators more than half the time,” said Dr MacNeil.

Dr Michele Barnes from the ARC Centre of Excellence for Coral Reef Studies at JCU said that in many places, social, economic, and cultural realities mean that marine reserves that entirely prohibit fishing are not an option.

“So, we also looked at how effective other forms of reef conservation were, such as restricting the types of fishing gear that people use. Our results were promising – these restrictions certainly had better outcomes than doing nothing, but not as good as marine reserves. They were a sort of compromise,” she said.

Professor Cinner said the study makes clear the benefits and limitations of implementing key coral reef conservation strategies in different types of locations. “Our research shows where managers will be able to maximise certain goals, such as sustaining top predators or improving the biomass of key fisheries species, and likewise, where they will be wasting their time,” he said.

Citation: Cinner JE, Maire E, Huchery C, MacNeil MA, Graham NAJ, Mora C, McClanahan TR, Barnes ML, Kittinger JN, Hicks CC, D’Agata S, Hoey AS, Gurney GG, Feary DA, Williams ID, Kulbicki M, Vigliola L, Wantiez L, Edgar GJ, Stuart-Smith RD, Sandin SA, Green A, Hardt MJ, Beger M, Friedlander AM, Wilson SK, Brokovich E, Brooks AJ, Cruz-Motta JJ, Booth DJ, Chabanet P, Gough C, Tupper M, Ferse SCA, Sumaila UR, Pardede S, Mouillot D (2018) Gravity of human impacts mediates coral reef conservation gains. Proceedings of the National Academy of Sciences 115:E6116-E6125

Video: here.

 

Contacts:                  

Professor Josh Cinner, CoralCoE at JCU

Mobile +61 417714138 (AEST/UTC +10)

Email: joshua.cinner@jcu.edu.au

 

Dr Michele Barnes, CoralCoE at JCU

Mobile: +61 (0)408677570 (AEST/UTC +10)

Email: michele.barnes@jcu.edu.au

 

Dr Aaron MacNeil, Dalhousie University

Office: +1 (902) 402-1273 (ADT/UTC -3)

Email: a.macneil@Dal.Ca

 

For More Information:

Catherine Naum

Communications Manager, ARC Centre of Excellence for Coral Reef Studies

Office: +61 (0)7 4781 6067 (AEST/UTC +10)

Mobile: +61 (0) 428 785 895

 

Background

The researchers evaluated fish biomass and the presence of top predators on coral reef sites across 41 countries, states, and territories. They used a new way of measuring the human pressures, such as fishing and pollution, to study the effects these are having on fish on the world’s reefs. They developed a ‘human gravity’ scale that calculates factors such as human population size, distance to reefs, and the transport infrastructure on land – which can determine reefs’ accessibility to fishermen and markets.

 

A shark’s habitat can reduce its sensitivity to rising CO2 levels, according to Australian scientists.

Globally, ocean acidification – linked to emissions of greenhouse gases – remains a major concern and scientists say it will harm many marine species over the next century.

Researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University have found that the epaulette shark, a species that shelters within reefs and copes with low oxygen levels, is able to tolerate increased carbon dioxide in the water without any obvious physical impact.

“As part of the study we exposed the sharks to increased CO2 for more than two months, mirroring the levels predicted for the end of the century,” says study co-author Dr Jodie Rummer from Coral CoE.

“We then tested the sharks’ respiratory system, measuring how much oxygen it needed to maintain basic function under the experimental conditions.”

The researchers found the sharks were regulating their systems to counter the higher levels of acid in their bodies. Importantly, Dr Rummer explains, the sharks’ ability to cope with low oxygen levels – similar to that found in its natural habitat – was unaffected by high CO2 levels.

Study co-author, Professor Philip Munday from the Coral CoE says the sharks’ physiological adaptations, which enables it to cope with the conditions within reefs, makes them better able to tolerate ocean acidification.

“Species that live in shallow reef environments, where they can experience naturally high CO2 levels on a regular basis, may have adaptations that make them more tolerant to future rises in CO2 levels than other species.”

Professor Munday says the next critical step is to test the sensitivity of other shark species to ocean acidification.

“Species that live in the open ocean may be more susceptible to future acidification than those that naturally live in shallow reef environments where they already experience a variable environment.”

Dr Rummer adds that by determining which animals are more and less susceptible to high CO2 than others, scientists will be better able to predict the future consequences of ocean acidification on marine ecosystems.

Paper

A product of its environment: The epaulette shark (Hemiscyllium) exhibits physiological tolerance to elevated environmental CO2 by Dennis D.U Heinrich, Jodie Rummer, Andrea J. Morash, Sue-Ann Watson, Colin A. Simpfendorfer, Michelle R Heupel and Philip L. Munday is published in the journal Conservation Physiology.

Link to paper: http://conphys.oxfordjournals.org/content/2/1/cou047.full

Images

Epaulette shark sheltering in reef – image credit: M.Heupel.

Contact

Dr Jodie Rummer, Coral CoE – +61 7 4781 5300, +61 (0) 439 166 171
jodie.rummer@jcu.edu.au

Professor Philip Munday, Coral CoE – +61 7 4781 5341
philip.munday@jcu.edu.au

Eleanor Gregory, Coral CoE Media – +61 (0) 428 785 895
eleanor.gregory@jcu.edu.au

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Coral Reef Studies

ARC Centre of Excellence for Coral Reef Studies
James Cook University Townsville
Queensland 4811 Australia

Phone: 61 7 4781 4000
Email: info@coralcoe.org.au