Ocean Acidification
Global warming is caused by increasing emissions of CO2 in the atmosphere, due to human's activities. Indeed, the main source of CO2 in the atmosphere, the main greenhouse gas, is the burning of fossil fuels. Fortunately for us, oceans act like a sink for CO2, and one third of the CO2 emitted by humans is absorbed by oceans, which regulates the air temperature.
However, this phenomenon is not neutral for the oceans. Indeed, the CO2 reacts with the water molecules, which leads to the H+ ions formation. By increasing the CO2 dissolution in the sea water, the pH value of the oceans decreases, they become more acidic. Moreover, a switch between the carbonates and bicarbonates ions is observed in the sea water chemistry. All these processes are called ocean acidification.
These changes in water chemistry have an impact on marine organisms, which are used to live with a more neutral pH. Biological processes such as ions transport, enzyme activity, photosynthesis and calcification process can be modified.
Impact on calcification:
The H+ ions created after the CO2 dissolution in water react with carbonate ions, which are no more available to react with calcium ions in the calcifying process. This imbalance in sea water chemistry can conduct to the calcium carbonate (calcite) dissolution, a component used by a lot of marine organisms. For example oysters, mussels, plakton, urchins, crabs and corals have a structure made of calcite.
The consequences for the marine life are tough. Discover why in this video:
Reactions after CO2 dissolution: CO2 + H2O <-> H2CO3 <-> HCO3− + H+ <-> CO32− + 2 H+
The expansion of ocean acidification and its mainly negative consequences on marine ecosystems are now largely admitted among the scientific community. However, there are still some grey zones. Will all the organisms react the same way, especially those with a shell? Will some be able to adapt, despite the speed of the phenomenon? Are all the oceans under threat? If yes, to what extend? Research continues...
More information
Scientific blog on Ocean Acidification
Other excellent video on ocean acidification by the Alliance of Climate Education