Coasts drown as coral reefs collapse under warming and acidification

December 03, 2020

A new study shows the coastal protection coral reefs currently provide will start eroding by the end of the century, as the world continues to warm and the oceans acidify.

A team of researchers led by Associate Professor Sophie Dove from the ARC Centre of Excellence for Coral Reef Studies at The University of Queensland (Coral CoE at UQ) investigated the ability of coral reef ecosystems to retain deposits of calcium carbonate under current projections of warming and ocean acidification.

Calcium carbonate is what skeletons are made of--and it dissolves under hot, acidic conditions. Marine animals that need calcium carbonate for their skeletons or shells are called 'calcifiers'. Hard corals have skeletons, which is what gives reefs much of their three-dimensional (3D) structure. It's this structure that helps protect coasts--and those living on the coasts--from the brunt of waves, floods and storms. Without coral reefs the coasts 'drown'.

A/Prof Dove says the amount of calcium carbonate within a coral reef ecosystem depends on the biomass of hard corals. But it also depends on the combined impact of warming and acidification on previously deposited calcium carbonate frameworks. She says the results of the study indicate the rate of erosion will overtake the rate of accretion on the majority of present-day reefs.

"Today's Great Barrier Reef has a 30% calcifier cover," A/Prof Dove said.

"If CO2 emissions aren't curbed, by the end-of-century a 50% calcifier cover is required to counter the physical erosion they face from storms and wave impacts," she said.

"In addition, more than 110% calcifier cover is needed to keep up with the minimal levels of sea-level rise."

However, A/Prof Dove says both of these scenarios are unlikely because high amounts of hard corals perish with intense underwater heatwaves. Previous studies show marine heatwaves will become chronic in the warmer months of an average year under unmitigated CO2 emissions.

The study was published in today's Communications Earth & Environment, just after the IUCN World Heritage Outlook 3 rated the Great Barrier Reef as 'critical'.

A/Prof Dove and her team built experimental reefs closely resembling those of shallow reef slopes at Heron Island on the southern Great Barrier Reef. For 18 months, they studied the effects of future climate scenarios on the ecosystem.

"What we saw was the insidious and accelerated loss of coastal protection under unmitigated CO2 emissions," said co-author Professor Ove Hoegh-Guldberg, also from Coral CoE at UQ.

"Under current projections, reefs will not simply adapt. Chronic exposure to the combined impacts of ocean warming and acidification will weaken reefs. They won't be able to re-build after disturbances such as cyclones, nor will they keep up with sea-level rise--possibly for thousands of years," said co-author Dr Kristen Brown, also from Coral CoE at UQ.

This means many coastal areas currently protected by calcareous coral reefs will no longer be so, impacting coastal infrastructure and communities.

"The combined impact of warming with the acidification of our oceans will see more than the collapse of ecosystems," A/Prof Dove said.

Dove S, Brown K, Van Den Heuvel A, Chai A, Hoegh-Guldberg O. (2020). 'Ocean warming and acidification uncouple calcification from calcifier biomass which accelerates coral reef decline'. Communications Earth & Environment. DOI: 10.1038/s43247-020-00054-x


Please note these images are for single use with this story only, not for any other story. No archival permissions are granted. Please ensure all resources carry correct attribution as listed in the file name.


A/Prof Sophie Dove (Brisbane, AEST)

Prof Ove Hoegh-Guldberg (Brisbane, AEST)

Dr Kristen Brown (Brisbane, AEST)
P: +61 (0)475 073 741


Melissa Lyne/ Coral CoE (Sydney, AEDT)
P: +61 (0)415 514 328

ARC Centre of Excellence for Coral Reef Studies

Related Coral Reefs Articles from Brightsurf:

The cement for coral reefs
Coral reefs are hotspots of biodiversity. As they can withstand heavy storms, they offer many species a safe home.

Palau's coral reefs: a jewel of the ocean
The latest report from the Living Oceans Foundation finds Palau's reefs had the highest coral cover observed on the Global Reef Expedition--the largest coral reef survey and mapping expedition in history.

Shedding light on coral reefs
New research published in the journal Coral Reefs generates the largest characterization of coral reef spectral data to date.

Uncovering the hidden life of 'dead' coral reefs
'Dead' coral rubble can support more animals than live coral, according to University of Queensland researchers trialling a high-tech sampling method.

Collaboration is key to rebuilding coral reefs
The most successful and cost-effective ways to restore coral reefs have been identified by an international group of scientists, after analyzing restoration projects in Latin America.

Coral reefs show resilience to rising temperatures
Rising ocean temperatures have devastated coral reefs all over the world, but a recent study in Global Change Biology has found that reefs in the Eastern Tropical Pacific region may prove to be an exception.

Genetics could help protect coral reefs from global warming
The research provides more evidence that genetic-sequencing can reveal evolutionary differences in reef-building corals that one day could help scientists identify which strains could adapt to warmer seas.

Tackling coral reefs' thorny problem
Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have revealed the evolutionary history of the crown-of-thorns starfish -- a predator of coral that can devastate coral reefs.

The state of coral reefs in the Solomon Islands
The ''Global Reef Expedition: Solomon Islands Final Report'' summarizes the foundation's findings from a monumental research mission to study corals and reef fish in the Solomon Islands and provides recommendations on how to preserve these precious ecosystems into the future.

Mysterious glowing coral reefs are fighting to recover
A new study by the University of Southampton has revealed why some corals exhibit a dazzling colorful display, instead of turning white, when they suffer 'coral bleaching' -- a condition which can devastate reefs and is caused by ocean warming.

Read More: Coral Reefs News and Coral Reefs Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to