How coral reefs could be saving themselves

Coral at Ningaloo Reef.

Marine scientists from the University of Western Australia have uncovered a glimpse of hope and optimism in local coral species amid the global stressors that continue to threaten our coastline.

During recent research at Rottnest Island, the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) found some species of corals have the ability to resist the effects of acidification.

Ocean acidification is the decline in the pH of sea water and occurs when CO2 human emissions are absorbed from the atmosphere into the ocean, making the ocean more acidic.

Lead UWA author Dr Thomas DeCarlo said he was interested to see how corals will respond to the changes in ocean chemistry, especially when they are thought to be some of the most sensitive organisms in the ocean.

“That’s because corals build their skeletons that they need to survive out of calcium carbonate and to do that they need to take irons or components of sea water to build that skeleton.

“And, the more acidified the sea water is, the more difficult it is for the corals to make their skeletons. So, they have to work harder or they will make smaller skeletons,” Dr DeCarlo said.

By using a new technique based on lasers, the UWA scientists were able to quantify the level of calcium internal to the coral, where the coral is building the skeleton on a micro-scale.

The world-first research found one species of coral was insensitive to and could resist ocean acidification by controlling its internal calcium, meaning the coral can build normal skeletons even in more acidified conditions.

Dr DeCarlo said other studies have only looked at the pH or the acidity within the coral and the acidity of the microscale fluid where the coral is building its skeleton.

“That hasn’t produced a clear result because the acidity of the microscale fluid where the skeleton building is happening seems disconnected from the external environment,” he said.

Dr DeCarlo said coral reefs around the world are under threat from a variety of stressors, mainly being ocean acidification and rising sea water temperatures.

“So, big problems for coral reefs on a global scale and we are already starting to see the effects of it now and there are many other effects that tend to be local, such as nutrient discharge from rivers and fertiliser use or over fishing. And, there is direct habitat alteration from dredging or destructive fishing practices.

But on a global scale, really coral reefs all around the world are struggling right now,” he said.

Dr DeCarlo said he hopes the new research raises the question about where the costs lie associated with surviving and living in a high CO2 world.

“I guess to summarise I see some hope out of this research and optimism but I want to hold caution that there is a lot more complexity and a lot more other stressors for coral reef,” he said.

For future research, Dr DeCarlo would like to apply these new techniques to more species and their ability to control their calcium from the Ningaloo Reef, the north of Western Australia, the Great Barrier Reef and globally.

“We know that there are some corals that live on Rottnest that are able to control their calcium to resist ocean acidification and that’s encouraging.

“But, we do need to consider the negatives of it, the species that do seem sensitive to acidification, as well as the potential trade-offs and causes of resisting acidification,” he said.