Ocean acidification refers to an ongoing change in the chemistry of the ocean caused an increase in the uptake of carbon dioxide from the atmosphere.
The ocean absorbs about one third of human-created carbon dioxide emissions. Carbon dioxide is a ‘Greenhouse Gas’ produced by the burning of fossil fuels. When carbon dioxide dissolves in seawater, carbonic acid is produced. This is slowly increasing the acidity of the oceans which can have a range of harmful consequences, such as depressing metabolic rates and immune responses in some organisms, causing coral bleaching and affecting the ability of some organisms to build the calcium carbonate shells that protect them. These changes pose new risks for a vast range of ocean life, from clams and coral reefs to crabs, shrimp, lobster, krill, sea urchin, sea snails, and some kinds of plankton, to name a few.
For an animated crash course on Ocean Acidification by the PEW Charitable Trust see: https://www.youtube.com/watch?v=ogZkV-Yj7Hc
You can help reduce ocean acidification today by finding ways to reduce your carbon footprint. Many of these options will also save you money!