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Ocean Acidification

The oceans play a key role in the global carbon cycle, especially in helping to regulate the amount of carbon dioxide in the atmosphere. They currently absorb about a quarter of the carbon dioxide released into the atmosphere, forcing the pH of the surface ocean lower in a process called ocean acidification. Excess carbon dioxide released from fossil fuels are absorbed into the oceans and reacting to form carbonic acid, driving their progressive acidification and causing a dramatic change to ocean chemistry and biodiversity. This reaction reduces the amount of carbonate ions in the ocean, which are used by calcifying organisms to build protective shells and skeletons. Ocean acidification therefore may adversely affect the growth and survival of these marine organisms. Ramifications of these impacts may harm economically valuable species, with potential influences on the global provision of marine ecosystem goods and services.

Ocean sediments record past biological responses to transient ocean acidification and show marked reductions and extinctions in some benthic organisms, as exemplified during the Palaeocene-Eocene thermal maximum (PETM). Current modelling suggests that seawater is acidifying at a rate that exceeds anything seen on Earth over the past 65 million years. It is thought that the pH of the ocean has gone from 8.25 to 8.14 since the industrial revolution and if ocean acidification continues at the current rate it is estimated that it will drop further by 0.3-0.4 units by 2100. This could have a potentially catastrophic effect on all marine organisms in both benthic and pelagic realms.


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