They are not that sensitive to temperature change, the article is bad science, the reefs are being bleached and killed by titanium and zinc much of which comes from sun screen. That is why the only reefs that are surviving are in remote areas that do not see the population density to elevate the water to the ppm that its needed to bleach the coral, I live less than 3 miles from Mote marine and run into and talk to many of their researchers not one of them has ever told me that they have data that warming alone is bleaching the reefs but they know for a fact titanium and zinc are, they are one of the foremost research centers on reef science and reef restoration:

https://www.icriforum.org/sites/default/files/ICRI_Sunscreen...

https://time.com/4080985/sunscreen-coral-reefs/

IIRC Hawaii has already banned sunscreens that contain those products and we have banned it in the Florida Keys. It is what is causing bleaching, we know it for a fact. My daughter while not a marine biologist yet, is well on her way, she does a lot of work on reef restoration and focuses her studies on Coral as it is what she wants to do. The entire focus on reef restoration is in the areas of agricultural run off, micro-plastics and suspended micro metals elimination as well as reforesting. Ocean temperatures are not killing the reefs if it was it would be as simple as troughing deep water and using tidal flow to up flow cooler water over the reef. I actually had this conversation with one of the researches once, as I interact with them from time to time due to my daughters interests.

Coastal mainland Florida has lost all of it's reefs, they where alive when I was a kid but where dying. It was also the time when Florida saw a huge tourism and population boom. The reefs in the keys where fine at that time, but by the early 90's the lower keys from the 7 mile bridge to Key west started to see signs of bleaching, meanwhile there was no evidence of it in the upper Keys which sits right in between the dead reefs of mainland Florida and the dying reefs of Key West. The difference was Key West became a larger tourist destination in that time due to the formation of the tourist development council in the years preceding. For the most part Key Largo still does not have the same problem (it is happening though, due to agricultural run off) because it sees less tourism than Key West and the tourism it does see is more SCUBA based tourism who generally do not wear sunscreen.

Another culprit is agricultural run off, while I am not a fan of the article below because it states it's global warming out of the gate, then offers no fact to back up said statement and omits the fact that the study they cite noted in the study that there where no increases in average water temperature in the Keys during the study, or the fact that the Keys has seen a Keys wide drop in average water temps for the past decade. There where several spikes in temperature above the threshold and die off where only observed when massive runoffs where in place. When the temps exceeded the threshold and runoff nitrogen and phosphorus where observed to be in low PPM there where no recorded die-offs. That being said it does do a good job of explaining what said runoff is doing to the reefs. Basically when the water hits a certain N:P ration in the presence of of warmer water, it kills the reef. Without the N:P ration the reefs thrive in the warmer spikes so, water temp is second to the fact that the presence of agricultural run off creates the chemical environment that is toxic to the reef. The heat is only the catalyst when those chemicals are presence.

https://www.hwhfoundation.org/news/nutrient-runoff-starves-c...

https://www.npr.org/2019/07/16/742050975/floridas-corals-are...

In the Keys we have banned fertilizers for lawn maintenance and we have moved the population centers to sewage whereas just a decade ago every house outside of Key West and Marathon has septic systems. But we still have a huge issue with Big sugar dumping water into the everglades which runs out of the gulf and over our reefs.

I am very concerned about our reefs and it is important that people know exactly what is killing them. Fixing global warming is not going to save our reefs. It gives people a false sense of security and needs to be rebuked as bad science.