The_{CO2 is} dissolved in the seawater and reacts with the water molecules. This produces free H+ ^ions , among other things, so that we can speak of ocean acidification. This very probably has a variety of effects on marine organisms.

Source:

IPCC. (2021): Climate Change 2021 The Physical Science Basis WGI. In Bulletin of the Chinese Academy of Sciences (vol. 34, number 2) chapter 5; from page 714