How does an increase in carbon dioxide affect ocean acidity?

An increase in carbon dioxide contributes to ocean acidity primarily through the process of carbon dioxide dissolving in seawater. When CO2 enters the ocean, it reacts with water to form carbonic acid. This reaction is a key chemical interaction that alters the balance of ions in the water.

As more carbon dioxide is absorbed, more carbonic acid is produced, which dissociates into bicarbonate and hydrogen ions. The increase in hydrogen ions leads to a decrease in the pH of the water, thus increasing its acidity. This increase in ocean acidity can have significant ecological impacts, particularly on marine life, such as coral reefs and shellfish, which are sensitive to changes in pH.

The other options do not accurately represent the relationship between carbon dioxide and ocean acidity. For example, simply decreasing acidity or claiming there is no effect overlooks the fundamental chemical processes at play. Additionally, the assertion about increasing oxygen levels does not relate to the direct chemical consequences of increased carbon dioxide, as it is focused on different aspects of ocean chemistry.