What is the primary cause of ocean acidification?

The primary cause of ocean acidification is the absorption of excess atmospheric carbon dioxide (CO2) by the oceans. When CO2 from the atmosphere dissolves in seawater, it undergoes a series of chemical reactions that lead to the formation of carbonic acid. This process results in a decrease in pH levels, making the water more acidic. As CO2 levels in the atmosphere rise, particularly due to human activities such as burning fossil fuels, deforestation, and industrial processes, more CO2 is absorbed by the oceans, exacerbating the problem of ocean acidification. This chemical change can have significant impacts on marine life, particularly organisms that rely on calcium carbonate for their shells and skeletons, such as corals and certain shellfish.

Other factors mentioned, such as pollution from plastics, overfishing, and increased nitrogen levels, while important environmental issues, do not directly cause ocean acidification. Plastics mainly contribute to physical and chemical pollution, overfishing affects fish populations and ecosystems, and excess nitrogen can lead to eutrophication, which affects coral reefs and ocean life, but none of these processes directly decrease the pH of ocean water in the way that excess CO2 absorption does.