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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 has delivered a stark warning about the impacts of urban growth on the world’s coral reefs.

As coastal developments expand at pace around the world, a year-long study of coral on a reef close to a rapidly growing urban centre in the Middle East has found they have become severely disturbed at the molecular level – with implications for all such corals worldwide.

Professor David Miller is a geneticist at James Cook University’s Centre of Excellence for Coral Reef Studies (Coral CoE). He said coral reefs are in global decline due to climate change and anthropogenic influences.

“Near coastal cities or other densely populated areas, coral reefs face a range of challenges in addition to that of climate change. To investigate the impacts of urban proximity on corals, we conducted a year-long study in the Gulf of Aqaba in the Red Sea, comparing corals close to an urban area to corals from a near-by non-urban area,” said Professor Miller.

He said the Gulf of Aqaba is an ideal study site because its corals have a remarkable level of thermal tolerance. This means scientists can isolate the effects of urban environments such as unpredictable and fluctuating levels of nutrients, hormone mimics and other organic contaminants, local pollution and chronic exposure to noise and light pollution, against a background of relatively limited potential impacts of ocean warming caused by climate change.

“Essentially, we found that in the area close to urban development, every natural biological rhythm is messed up in the coral host, that the algal symbionts are seriously under-performing and that the microbiome is also out of kilter. These corals are comprehensively disturbed, despite appearances,” said Professor Miller.

He said for instance, bacteria on the coral peaked at different moon-phases between the urban and non-urban coral, while reproductive processes, which are all aligned with the moon phase, were wiped out in the urban corals.

“This study is significant because while a lot of work had previously been done on the impacts of individual stressors on corals, no one had previously looked at how corals in the wild react to real-world complex combinations of stressors,” said Dr. Inga Steindal, also of the Coral CoE.

She said the findings were alarming, given the recent and planned extensions of urban centres near tropical coastlines.

There has been continuous growth of cities such as Jakarta, Singapore and Hong Kong, but also major new developments have occurred or are planned that are likely to directly impact coral reefs in the near future. The population of the Chinese coastal city of Shenzhen alone has grown from less than a million in 1990 to more than 12.5 million in 2021.

“With that kind of expansion and with more to come, things don’t look too good for the future of corals in those regions,” said Professor Miller.

PAPER

Rosenberg Y., Blecher N.S., Lalzar M., Yam R., Shemesh A., Alon S., Perna G., Cardenas A., Voolstra C.R., Miller D.J., Levy O.  2022. ‘Urbanisation comprehensively impairs rhythms in coral holobionts’. Global Change Biology. DOI: 10.1111/gcb.16144

CONTACT

Professor David Miller (Townsville, AEST)

M: +61 (0)419 671 768
E: david.miller@jcu.edu.au

Dr. Inga Steindal (Townsville, AEST)
M: +61 (0)481 300 921
E: inga.steindal@jcu.edu.au

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.”

 

Paper

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.

http://onlinelibrary.wiley.com/doi/10.1111/mec.13021/abstract

Images

Corals – image credit: Aurelie Moya

Contacts

Dr Aurelie Moya – +61 (0) 7 4781 3654

aurelie.moya@jcu.edu.au

Professor David Miller – +61 (0) 419 671 768

david.miller@jcu.edu.au

Eleanor Gregory, Coral CoE Communications Manager – 0428 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