KeywordsCarbonic Acid Ocean Acidification Coralline Alga Seawater Chemistry Preindustrial Level
Ocean acidification refers to the process of increasing seawater acidity by dissolving additional carbon dioxide (CO2) from the atmosphere.
The increase in atmospheric CO2 concentration since preindustrial times from 280 ppm (parts per million) to ca. 400 ppm has caused a decline in surface ocean pH by 0.12 units. This corresponds to an increase in seawater acidity (hydrogen ion concentration) of 30 %. If atmospheric CO2 concentrations continue to increase at present rates, surface ocean pH values will decline by an additional 0.35 units by the year 2100 (Wolf-Gladrow et al., 1999). This corresponds to more than a doubling in seawater acidity and a decline in carbonate ion concentrations by 45 % relative to preindustrial levels. These changes in seawater chemistry are expected to widely affect marine organisms and ecosystems (Raven et al., 2005). Most prominently, calcifying organisms such as corals, bivalves, sea urchins, coralline algae, and a variety of calcareous plankton species have shown to be sensitive to ocean acidification (Gattuso and Hansson, 2011). Equally important as the magnitude of ocean acidification is its rate of change, as this determines to what extent species have the ability to adapt. The current speed of CO2 increase in the atmosphere and the corresponding rate of ocean acidification are unprecedented in Earth’s history for at least 300 million years (Hönisch et al., 2012).
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