Ocean acidification.
Ocean acidification has become an increasingly pressing issue in global oceans; especially with the rise in carbon dioxide levels in the atmosphere. Carbon dioxide is a naturally occurring element of the biological cycle but because of human actives and the rise of carbon dioxide emissions the concentration of carbon dioxide has increased. Diagram 1 explains the relationship between atmospheric carbon dioxide and the impact on the ocean’s carbonate ions which are varying in concentration due to the ocean’s pH. When the level of carbon dioxide increases in the air, the ocean tries to reach an equilibrium by taking in more carbon dioxide. As shown by the diagram, as carbon dioxide is taken up by the ocean about 90% reacts with water and the major products that form are carbonate and bicarbonate. However, as this process occurs the concentration of hydrogen ions, which lower the ocean’s pH, increase. The effects of this process are shown in the diagram as the ocean’s pH level, which represented by the red line at about 8.1, lowers so does the carbonate concertation.
The concentration of carbonate which is responsible for the production of vital calcifying organisms such as pteropods (which is a type of phytoplankton), lowers as the ocean becomes more acidic. This has already been causing major issues in high carbon dioxide absorption areas such as the Southern Ocean where phytoplankton are struggling to precipitate out calcium carbonate to create more biomass which will have harsh impact on the food chain. McNeil and Matear predicted by 2038 the earth’s atmosphere would have reached a concertation of 450-ppm of that will consequently cause an under-saturation of aragonite (which is a more soluble type of calcium carbonate structure) in the Southern Ocean. Coral reefs which are made of calcite are a less soluble form of calcium carbonate are at less of a risk of under-saturation but when effected will lead to the degradation of a critical ocean ecosystems.
By: Kirstin Robyn Petzer
Acknowledgments:
McNeil B.I & Matear R.J. 2008. Southern Ocean acidification: A tipping point at 450-ppm atmospheric . PNAS, 105(48):18860–18864.
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