Look at it from the coral's point of view. Stress on corals. Here are corals that have gone with the flow for 200 million years, and now they're facing the precipitate exodus of their business partners, the zoox- anthellae. But this was a deal struck with algae back in the Tethys Ocean. Sanctuary from predation and the safety of a home.
Home is no longer home sweet home.
The partnering of coral and zooxanthellae was once a powerful evolutionary achievement between them they built the reef. And now, between them, they may just let it go, dust to dust, coral reefs to their constituent parts. The Gogo reef was a different kind of reef, no symbiosis between polyp and algae, more a community of sponges and sea mosses that formed hard skeletons. Oceans come and oceans go. Once they cut a deal with the corals, but they didn't mean forever.