Actually, the water of all the Earth’s oceans and interconnected arms such as Puget Sound, are not now acidic, but alkaline, with an average pH of around 9. (A pH of 7.0 is neutral with numbers above 7 alkaline and numbers below acid.) Increasing CO2 in our atmosphere will be absorbed by the oceans, and will tend to decrease the present alkalinity (reducing the pH) by forming weak carbonic acid.
Because of increasing CO2 levels, therefore, the oceans will tend to have their present alkalintiy slowly reduced, and at some future date, perhaps thousands of years from now, become acidic (pH below 7). It would appear therefore that the future health of shellfish will depend more upon the oceans obtaining some optimum value of increased alkalinity, which can then be hopefully maintained by stringent and worldwide CO2 reductions.