ut exactly how the increasing acidity impacts coral growth was hard to determine. “If you just look at survival rates of these things, effectively they all survive,” said Peta Clode from the University of Western Australia. “So if you look at that data you think nothing is wrong.”
Even studies that used microscopes to examine how corals grow in more acidic water had trouble finding differences, she said.
So Clode and colleagues went a step further and grew corals in a range of different temperatures and acidities, and then used a high-resolution three-dimensional x-ray microscope to examine how they grew.
Published in the journal Science Advances on Friday, the images and videos they produced revealed striking deformities in corals grown under conditions the oceans are expected to see by the end of the century.
The stories you need to read, in one handy email
Read more
Under normal conditions, baby corals grew skeletons that were symmetrical, strong and with thick walls.
But when the acidity was raised to the level expected by 2100 if emissions are not cut drastically, the skeletons had some spines stunted in growth, while others grew longer. Some parts of the skeleton were completely absent.
They grew into an asymmetrical shape and their walls became pitted and porous, and half of them had fractures in their deformed skeletons.
“You think ‘oh my god, look at them.’ It is very dramatic,” said Clode. “You would expect they would not grow very well. But to see such deformity is surprising. We expected they might just grow less.”
The effect of heat alone seemed to have little impact, and when combined with high acidity it had a beneficial effect, mitigating some of the deformities caused by the higher acidity.
Clode said that was not completely surprising, since higher temperatures that did not stress coral – temperatures that were not too high or too suddenly raised – had been seen to improve coral growth before.