Remember how ocean acidification is really bad for coral? Surprisingly, that may not always be the case. A new study of tropical corals has shown that their rate of reef-building actually increases with moderate hikes in acidification. It is only intense acidification that can harm coral.

That's at least according to a study recently published in the journal Pro­ceed­ings of the Royal Society B, which details how exactly coral structure can benefit from this usually harmful global change.

It should be pointed out that the researchers behind this work are in no way denying what is occurring to tropical corals across the globe. Extensive records have shown that increased ocean acidification is gradually diminishing one of the most iconic coral reefs in the world: the Great Barrier Reef. Worse still, experts have found that the continued damage that intense ocean acidification inflict on our reefs is actually costing the world trillions of dollars in declining ecosystems and coastal infrastructure.

However, as the saying goes, 'there is a silver lining to every storm cloud.' That's where researchers from North­eastern University's Marine Sci­ence Center and the Uni­ver­sity of North Car­olina at Chapel Hill have aimed their work.

"The study showed that this species of coral (Sideras­trea siderea) exhib­ited a peaked or par­a­bolic response to both warming and acid­i­fi­ca­tion, that is, mod­erate acid­i­fi­ca­tion and warming actu­ally enhanced coral cal­ci­fi­ca­tion, with only extreme warming and acid­i­fi­ca­tion neg­a­tively impacting the corals," co-author Justin Ries explained in a statement. "This was sur­prising given that most studies have shown that corals exhibit a more neg­a­tive response to even mod­erate acidification."

The researcher and his colleagues found that while intense ocean acidification is negatively affecting some coral communities, not all are being hit so hard, thanks to the natural flow of the ocean.

Ocean acidification is caused by the ongoing uptake of heightened carbon dioxide from the Earth's atmosphere. Some coral communities, exposed to only a minor acidic hike, are growing faster than ever before, as heightened carbon levels are helping coral's algal symbionts to accelerate the calcification process that makes a reef.

This may explain why some species of coral appear to be 'winning' in the race to survive climate change.

However, Ries notes that the rate at which the Earth's waters continue to acidify is alarming, compared to the geo­logic his­tory of ocean acidification.

"The amount of change that would typ­i­cally occur in about 10 mil­lion years is being con­densed into a 300-​​year period," Ries said. "It's not the just the mag­ni­tude of the change that mat­ters to the organ­isms, but how quickly it is occurring."

And such an escalated rate may tip the scales for the worse, despite the brief benefit coral's algal helpers are receiving.