[Supermancho]

> Corals have persisted through the geological past when atmospheric CO2 was many times today's level.

We're heading toward something similar to the Miocene, both in CO2, temperature, and ph. You might want to look into the "Middle Miocene disruption", which refers to a wave of extinctions of terrestrial and aquatic life forms that occurred following the Miocene Climatic Optimum. There's a big oceanic fossil gap in the Miocene, because of this peak-temperature which seemed to tilt ecosystems too far. We do know the hard-coral scleractinians (same as modern corals^1) didn't appear because of this change, but likely because they were one of the few types that can survive it. Unfortunately, if the trend continues, the hardiest of the ancient species all die^2. 7.2 doesn't sound like 7.95? The ocean isn't uniformly affected^3 and will likely kick off another "disruption" of the existing ecosystems causing a collapse. ie You don't need to set fire to all the trees for the forest to burn down.

^1 https://bmcecolevol.biomedcentral.com/articles/10.1186/1471-... ^2 https://www.pnas.org/doi/10.1073/pnas.1419621112 ^3 https://en.wikipedia.org/wiki/Ocean_acidification