Ocean acidification causes deformities in young coral skeletons

Ocean acidification could lead to smaller, more porous and malformed skeletons in coral recruits by 2100 say a team of scientists from the ARC Centre of Excellence for Coral Reef Studies and the University of Western Australia.

“New coral recruits are only about 1 mm in diameter and so they are more vulnerable to stressors like predation, overgrowth and damage from storms” explains Taryn Foster, lead author of the paper, which was published this week in the journal Science Advances, an online journal of Science. “They need to be able to build robust skeletons and do this quickly, in order for them to move out of these small and vulnerable size classes. Unfortunately, ocean acidification is making this task more difficult.”

“We mimicked the oceanic conditions predicted to occur under a ‘business-as-usual’ emissions scenario, elevating both the water temperature and CO2 levels. We then used 3D X-ray microscopy and scanning electron microscopy to both visualize and quantify changes in the skeletal formation and found that coral recruits were unable to build normal skeletons under acidified conditions.”

“Not only did we record reduced overall skeletal deposition, but we also observed a number of deformities in the skeletons grown under high CO2. These ranged from gaps, fractures and disrupted symmetry to large sections of missing skeleton. We also saw deep pitting and a corroded-looking skeletal surface in the high CO2 corals.”

“One encouraging and surprising finding was that elevated temperature didn’t seem to exacerbate the effects of high CO2. Instead we saw the opposite effect, with elevated temperature having a mitigative effect under acidified conditions. But we think this response will only be seen in sub-tropical and temperate corals such as those used in this study, which were from the sub-tropical Houtman Abrolhos Islands.”

“This study exposes for the first time, changes to the structure of the coral recruit skeleton under predicted ocean acidification. Using 3D X-ray microscopy has made it possible to measure internal structures, volume and look at each individual X-ray slice; things that are impossible to do using conventional 2D imaging methods. It also makes it much easier to communicate the changes that ocean acidification could cause in these tiny animals, which are essential for replenishing the reef and recovery after disturbances.”

The co-authors for the paper are Assistant Professor James Falter and Professor Malcolm McCulloch from theARC Centre of Excellence for Coral Reef Studies and UWA’s School of Earth and Environment, and  Associate Professor Peta Clode from UWA’s Centre for Microscopy, Characterisation and Analysis. The project was funded by the ARC Centre of Excellence for Coral Reef Studies.

The paper “Ocean acidification causes structural deformities in juvenile coral skeletons” by Taryn Foster, James Falter, Malcolm McCulloch and Peta Clode is published in the journal Science Advances.

Contacts:
Professor Malcolm McCulloch
T: +61 0 457 939 937
E: malcolm.mcculloch@uwa.edu.au

Associate Professor Peta Clode
T: +61 8 6488 8098
E: peta.clode@uwa.edu.au

More Information:
Taryn Foster
E: taryn.foster@research.uwa.edu

Paper:
Taryn Foster, James L. Falter, Malcolm T. McCulloch, Peta L. Clode (2016). Ocean acidification causes structural deformities in juvenile coral skeletons. Science Advances.