Be nice if so!

http://blogs.discovermagazine.com/the-extremo-files/2017/05/13/529/#.WRjp-ROGPdQ

"Warmer water isn’t inherently a problem: corals could almost certainly tweak their proteins and cellular structures to deal with the heat and retain their symbionts. But coral genomes change slowly, over centuries or millenia, and the Acropora of American Samoa don’t have that kind of time. "

"After the 17-month transplant, some corals were subjected to a heat stress experiment, as water was heated from 29 to 35 °C over the course of three sweltering hours. Those that had spent the last year and a half in the MV pool – regardless of their initial provenance – suffered more, bleaching beyond repair and losing substantial diversity from their microbiomes."

Wow. Increased by 6 degrees for 3 hours. And they thought they would be acclimatised? That time frame for centuries to millenia appears off.