Rising emissions of carbon dioxide create twin threats for coral in oceans around the world: warmer temperatures, which can cause mass bleachings, and ocean acidification, which can hinder the animals’ ability to build reefs.

But a new study published on Friday in the journal Science Advances suggests that ocean acidification may be the bigger worry in some waters.

Studying a chain of remote Australian islands in the Indian Ocean, researchers found that more acidic waters (those that have absorbed more atmospheric carbon dioxide) cause serious skeletal deformities in juvenile coral in subtropical waters.