What affects coral growth rates

Here's a very good summary of research into what affects coral growth rates for the reefs around Bermuda.


Study of Bermuda corals finds temperature is most influential factor on coral growth

Ah yes. Temperature.

And right now, temperature is helping the corals around Bermuda compensate for the effects of ocean acidification.

" “At the present time, Bermuda’s coral reefs appear to be faring reasonably well with high rates of coral production and calcification that appears to be temporarily offsetting the impact of ocean acidification,” said Nicholas Bates, the director of the Bermuda Institute for Ocean Sciences and a co-author on the paper.

“We saw that as the temperature got warmer, there wasn’t a point in the data where it got too warm and calcification started to slow down,” Courtney said. “We also didn’t observe significant coral bleaching in the study, so in Bermuda the thermal maximum, or the highest temperature at which coral can grow, likely wasn’t exceeded during the two-year study.”

However, not all is rosy, if the temperature of ocean surface waters keeps increasing.

"The positive effect of modest warming on coral calcification had been observed in many laboratory experiments. But, as [graduate student Travis] Courtney explained, it comes with a caveat: if the warming is too much or too fast, corals quickly reach a tipping point. 

“Then there's a very sharp downturn, which is usually somewhere around the maximum average summer temperature—just a little warmer than what they’re used to—where corals have a very quick downturn in how fast they can grow,” Courtney said. “About another degree past that maximum summer temperature is often when bleaching can happen. The coral is stressed, and it starts growing slower, and then stress mechanisms trigger bleaching and it loses its symbiotic algae. If that bleaching stress is severe enough for long enough, that's when you can have coral mortality.”

And this has been happening when it gets too hot.

Yes, people, there's a warning in that.  And we need to pay attention to it.