The oceans are huge, but we've already managed to decrease pH by 0.1 in the past century.

A pessimistic but plausible scenario has ocean pH decreasing by an additional 0.7-0.8 by 2300.

That's pretty fast. It's hard to predict how and how fast coral might adapt, but those are short time scales to expect evolution to act on.

Pardon the profanity, but fuck! On a logarithmic scale, a decrease of 0.1 on the pH is a 25% increase in H+ concentration...

... and a decrease of 0.7 is a 500% increase in H+ concentration. That sounds apocalyptic, at least for ocean ecosystems.

Warming and acidification are increasing jellyfish blooms, right? Do you know any good recipes for grilled jellyfish?

Complex question, but there are a few aspects that work against them:

- coral typically takes several years before reaching sexual maturity. Adaptability to a changing environment strongly depends on this.

- corals typically occupy ecological niches.

- acidification directly interferes with a key part of their metabolism and habit. It's like asking whether mammals can't evolve to a life without skeletons.

Corals are an extremely diverse group of organisms that interact with other organisms through complex relationships. Take them away (or reduce them to a select few species that fulfill a fitness) and you're going to see lots of damage to other populations.