Ocean cannot become more acidic and warmer at the same time

The oceans´acidity is said to change because of rising CO2 levels in the atmosphere. There are several factors that make this hard to believe, see for example(1). Firstly, a significant and lasting change of the CO2 content in the ocean is related to the content of bicarbonate (HCO3-), which is ca. 55 times the content of CO2, and to the equilibrium of both with vast amounts of solid carbonates in the sea bottom sediments and the oceanic crust. Adding CO2 in a buffered and open system such as the sea-atmosphere will not change the acidity much. Secondly, if the ocean temperature is increasing, the solubility of CO2 will be reduced, thus leading to a reduction of acidity, not an increase. The sea surface act as a barrier to increased CO2 due to low water pressure and faster heating. It is difficult to have temperature and acidity increase at the same time. The debate in the 70-80s about acidification of rivers and lakes focused on sulphur and nitrogen emissions. The problem seems to have been solved by sulpur reduction. Why were these compounds so important for the acidity in the rivers and lakes and CO2 was not, while CO2 now changes the acidity in the oceans and S and N are not?

(1) Thurman, H.V. Introductory oceanography. 5ed. Merrill Publishing Company, Columbus, Ohio, USA, 515 pp.