(i) Why use the term "more acidic"? That term implies the oceans are already acid, when in fact they are alkaline with a pH of around 8. I think it's pretty obvious what is meant: the pH is less than what it was. The writer could have said less alkaline. A change in pH by even a fraction could be very significant as the pH is a log scale with a change of a factor of ten in the hydrogen ion concentration for every change of one in the pH scale.
