Maybe you should get up to HS level chemistry. The Ocean is a _buffered_ solution. Which makes it require an order of magnitude more of anything to change it's ph past the buffer levels.
Yes, but the buffering is provided by Ca ions, which means that the ph is not the issue, but rather what happens to the CaCO3 equilibrium. There is a nice description with citations here. That summary also points out that bleaching is a bigger problem for coral than acidification, but TFA is about studying the impact of this chemistry on other life forms.
But my original point was that this stuff is not extraordinary science, and your adding Le Châtelier into the mix only moves the needle by about 20 years to the late 1800s...
(Oddly, enough, the same kid is taking HS chemistry this year, so I'll get to brush up a bit, but it is surprising what you can remember from 40 years ago when breakfast this morning is a mystery!)