Ocean acidification is the continuous reduction of the Earth’s ocean’s pH levels. This is caused by the oceans uptake of carbon dioxide derived from human activities from the atmosphere. In the last 243 years the ocean surface pH has been reduced from about 8.179 to 8.104.
The carbon cycle is the constant change of carbon dioxide between the terrestrial biosphere, atmosphere, lithosphere and the oceans. Human activities such as combustion of fossil fuels, land-use changes and cement production have let to this constant change of CO2 into the Earth’s atmosphere. Some CO2 has been taken by terrestrial plants, the oceans have absorbed some CO2, and some has remained in the atmosphere. There are two forms of the carbon cycle: inorganic carbon cycle and organic carbon cycle.
How Acidification Takes Place
The decrease in ocean pH most often stems from dissolving CO2 in the oceans saltwater. By dissolving this it increases the hydrogen ion concentration leading to a reduction in pH. Ocean acidification will continue to decrease as more carbon dioxide derived from human activities is absorbed by the oceans. How much acidification takes place in the future ultimately depends on the emissions pathways and mitigation that society chooses to take.
A continuous reduction in the ocean’s pH will have negative consequences. These consequences will primarily affect oceanic calcifying organisms. These organisms rely on the calcite of calcium carbonate or aragonite polymorphs to construct their skeletons or cell coverings. Calcifying organisms include organisms such as mollusks, coccolithophores, crustaceans, corals, echinoderms and foraminifera.
When pH levels are within a normal range, aragonite and calcite are stable in the ocean surface because carbonate ion experiences supersaturating conditions. This ions concentration falls as the ocean pH falls resulting in structures made of calcium becoming undersaturated. When undersaturated they are vulnerable to dissolution.
As ocean acidification continues to occur, scientists fear that the possible damage could grow. Minerals in the water and sea life are currently at the biggest risk concerning the potential consequences of this process.
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