New research has provided some positive news for our coral reefs — they may be more resistant to future climate change than first thought.

But researchers warn this doesn’t mean we can stop worrying about the health of coral reefs. Rather, we may now be seeing a silver lining to some very dark climate clouds.

Data from the Australian National University has shown that one key part of the coral reef structure may be more resilient to climate change-related ocean acidification. PhD student Merinda Nash, the lead author on the piece that was published in Nature Climate Change yesterday, says it’s good news for our reefs — but that doesn’t mean we can stop worrying about their health.

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Discussing articles such as that in The Australian published yesterday — “Forget the doom; coral reefs will bloom” — Nash says while she’s happy with the coverage of her work, the idea that coral reefs face no threat from impending climate change isn’t correct.

“Our research is not saying that the coral reefs are going to be fine. It’s just this one component that everyone thought was going be catastrophic, is probably now more resilient than we thought,” she said.  “It’s like if you were researching forests and you found that the moss is going to be fine, so therefore say the entire forest is going to be fine. You don’t want a paddock full of moss without any trees.”

Climate change presents various threats to coral reefs. As temperatures increase, the organism called zooxanthellae, which corals rely on for some of their food, have been found to leave their host, causing coral bleaching and death. Second, researchers have also become concerned that reefs are under threat due to the increase in the amount of dissolved carbon dioxide in the water. As CO2 is released into the air, it dissolves into the ocean. This in turn makes the ocean more acidic, dissolving some parts of the reef, and making it so that other parts can’t absorb the minerals they need to maintain their structure.

Nash says the research looks at what can be described as the cement of the coral house. “A coral reef is like a house — the coral are the bricks, but the coralline algae are the cement that holds it all together,” Nash explained. “Researchers are concerned that when atmospheric carbon levels rise and ocean acidity increases, the magnesium calcite which makes up the coralline algae will dissolve first, threatening the very foundations of the reef.”

But Nash found a mineral in coralline algae that makes the organism less susceptible to being dissolved as the ocean became more acidic.

“In a rare piece of good news, we found when we analysed algal samples from Heron Island on the Great Barrier Reef that the cell spaces in the algae were filled with dolomite, the same strong mineral that makes up the Dolomite Alps in Italy. Dolomite is about half magnesium and half calcium and is less susceptible to acidity than the magnesium calcite, meaning the structure of the coral reefs is stronger than previously thought,” she explained.

Nash says there are already reefs that exist of just coralline algae, and they are unrecognisable compared to the reefs we think of on the Australian coast.

“There are coralline algae platforms that exist off South America. They’re not very biodiverse. There are only six or seven types of coral that live there,” she said. “If you have a reef just made up of coralline algae it would be unrecognisable. It will provide coastal protection, but won’t support fishing or be very interesting for diving.”

This sentiment is echoed by researcher James Brown from the Kimberley Marine Research Station, who was also quoted in The Australian’s piece. Research conducted in the Kimberley region where Brown works has shown coral reefs are living in areas with extremely high readings of dissolved CO2. But it comes nowhere near to indicating we can relax about the health of reefs. Brown says more research is needed.

“The CSIRO found this high dissolved carbon dioxide reading in two different stations at King Sound in the Kimberley. That’s not a large enough sample to understand what is going on though,” Brown said. “As a research station we’ve been working to see what happens over a temporal scale. That research hasn’t really happened though … you’re talking about an area in the world where there’s been no research done — almost nothing.”

Bradley Opdyke, who collaborated with Nash on her paper, said: “The clouds of climate change are very dark, but now there is this thin silver lining.”

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Peter Fray
Peter Fray
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