Ocean acidification is the name that was given to the ongoing decrease in the pH of Earth’s oceans, a cause of the uptake of anthropogenic carbon dioxide from the atmosphere. About 30 to 40 percent of the carbon dioxide that is released by humans into the atmosphere dissolves into the lakes, oceans, and rivers. To maintain the chemical equilibrium, some of it reacts with the water to create carbonic acid. Some of these extra carbonic acid molecules react with a water molecule to provide a bicarbonate ion and a hydronium ion, therefore, increasing the oceans “acidity”.
This increasing acidity is considered to have a range of direct undesirable consequences such as depressing metabolic rates in jumbo squid and depressing immune responses of blue mussels.
Other chemical reactions are triggered as well which result in an actual net decrease in the amount on carbonate ions available. Within the oceans, this makes it harder for marine calcifying organisms such as plankton and coral to form biogenic calcium carbonate, and such existing structures become vulnerable to dissolution. Therefore, ongoing acidification of the oceans also stands as a threat to the food chains connected with the oceans.
Image Caption: Estimated change in annual mean sea surface pH between the pre-industrial period (1700s) and the present day (1990s). Δ pH here is in standard pH units. Calculated from fields of dissolved inorganic carbon and alkalinity from the Global Ocean Data Analysis Project climatology and temperature and salinity from the World Ocean Atlas (2005) climatology using Richard Zeebe’s csys package. It is plotted here using a Mollweide projection (using MATLAB and the M_Map package). Note that the GLODAP climatology is missing data in certain oceanic provinces including the Arctic Ocean, the Caribbean Sea, the Mediterranean Sea and the Malay Archipelago. Credit: Plumbago/Wikipedia (CC BY-SA 3.0)