Ocean acidification is the ongoing decrease in the pH of Earth’s oceans, caused primarily by the absorption of excess carbon dioxide (CO2) from the atmosphere, a consequence of human activities such as fossil fuel burning and deforestation. When CO2 dissolves in seawater, it forms carbonic acid, which increases the concentration of hydrogen ions and lowers the ocean’s pH, making the water more acidic. This chemical change reduces the availability of carbonate ions, which are essential for marine organisms like corals, shellfish, and plankton to build and maintain their calcium carbonate shells and skeletons. Since the Industrial Revolution, ocean acidity has increased by about 30 percent, a rate roughly 10 times faster than any change in the last 55 million years. Ocean acidification poses serious threats to marine ecosystems, disrupting biodiversity, food chains, and economic activities dependent on fisheries and aquaculture. The process occurs globally, including in coastal estuaries and deep ocean waters, and its effects may last for thousands of years even if carbon emissions are drastically reduced.
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