Ocean acidification is a phenomenon that occurs when seawater becomes more acidic due to an increase in the amount of carbon dioxide (CO2) in the atmosphere. When the atmosphere is heated up by greenhouse gas emissions, such as CO2, a portion of this CO2 is absorbed by the oceans. Seawater reacts with the absorbed CO2 to form carbonic acid (H2CO3), which in turn decomposes into hydrogen ions (H+) and bicarbonate ions (HCO3-). These ions increase the pH of seawater, making it more acidic.

Ocean acidification has serious consequences for marine life and marine ecosystems. For example, marine organisms that use calcium carbonate to build their shells or skeletons, such as oysters, mussels and corals, may have difficulty surviving in more acidic water. Additionally, ocean acidification can affect the marine food chain, as organisms that constitute the base of the food chain, such as microalgae, may be affected by acidification.

Ocean acidification could have an impact on the economy, as many industries, such as aquaculture and tourism, depend on the health of marine ecosystems.

To reduce ocean acidification, it is necessary to reduce greenhouse gas emissions and increase the CO2 absorption capacity of marine ecosystems, for example through conservation and restoration of coastal and marine ecosystems.