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

3

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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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.

Citation: Keith, SA, Baird, AH, Hobbs, J-PA, Woolsey, ES, Hoey, AS, Fadli, N, Sanders, NJ (2018) Synchronous behavioural shifts in reef fishes linked to mass coral bleaching. Nature Climate Change 8:986-991

Visuals available here.

Video abstract here.

 

CONTACTS

Sally A. Keith, PhD (UNITED KINGDOM)
Lancaster University
E: sally.keith@lancaster.ac.uk
Twitter: @Sal_Keith

Beth Broomby, Head of Press Office
Lancaster University
O: +44 (0) 1524 593719
M: +44 (0) 7881813831

Prof Andrew Baird (AUSTRALIA) – available for comment from 29 October
ARC Centre of Excellence for Coral Reef Studies
James Cook University
E: andrew.baird@jcu.edu.au

Catherine Naum, Communications Manager
ARC Centre of Excellence for Coral Reef Studies
E: catherine.naum1@jcu.edu.au

 

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.

Lead author Dr Pedro Frade from the Center of Marine Sciences, in Portugal, said the scientists were astounded to find bleached coral colonies all the way down to 40 metres.

“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.”

Co-author and Coral CoE alumnus, Dr Pim Bongaerts from the California Academy of Sciences said that during the bleaching event, upwelling cold-water initially provided cooler conditions on the deep reef.

“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.

Frade PR, Bongaerts P, Englebert N, Rogers A, Gonzalez-Rivero M and Hoegh-Guldberg O. (2018). Deep reefs of the Great Barrier Reef offer limited thermal refuge during mass coral bleaching. Nature Communications, DOI: 10.1038/s41467-018-05741-0 

For more information, please contact:

Dr Pedro Frade
prfrade@ualg.pt

Prof. Ove Hoegh-Guldberg
oveh@uq.edu.au

Dr Pim Bongaerts
pbongaerts@calacademy.org

The Great Barrier Reef is losing its ability to recover from disturbances, but effective local management could revive its capacity to bounce back.

Scientists at The University of Queensland, ARC Centre of Excellence for Coral Reefs Studies (Coral CoE) and the Australian Institute of Marine Science (AIMS) have found a decline in the ability of Great Barrier Reef Marine Park reefs to recover after bleaching events, outbreaks of crown-of-thorns starfish or cyclones over an 18-year period, from 1992 to 2010, even before the recent back-to-back bleaching in 2016 and 2017.

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.”

Study co-author Dr Nicholas Wolff, from The Nature Conservancy, said that some areas of the reef are faring better than others, but their overall finding was that action needs to be taken.

“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).

Citation:

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

 

Media: Dr Juan Ortiz, j.ortiz@uq.edu.au, +61 (0)412 200 831; Professor Peter Mumby, p.j.mumby@uq.edu.au, +61 (0)449 811 589 (email-preferred); Dr Nicholas Wolff, nicholas.wolff@TNC.ORG; +1 2075226101; Dominic Jarvis, dominic.jarvis@uq.edu.au, +61 413 334 924; Catherine Naum, catherine.naum1@jcu.edu.au, +61 428 785 895.

Note to Editor:

Prof Mumby will be speaking at the Coral Reef Futures Symposium of the Australian Research Council Centre of Excellence for Coral Reef Studies at 1.50pm on 19 July 2018 (AEST). Media are welcome to attend. Follow us on Twitter #CORAL18

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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