The dissolution of carbon dioxide in the oceans produce hydrogen ions as when carbon dioxide is dissolved in the ocean it leads to Ocean Acidification. This Acidification produces the hydronium ions as more acidic nature implies higher concentrations of hydrogen ions.
Carbon dioxide is a gas that readily dissolves in water to give Carbonic Acid , bicarbonate ions and carbonate ions , all of which are acidic in nature. This lowers the pH of the ocean making the waters more acidic. Therefore the acidity of oceans is largely dependent on carbon compounds and the amount of Carbon dioxide.
The reaction of Carbon dioxide with water to give carbonic acid :
