Ocean acidification and mass extinction events in the geologic past




Three of the big five mass extinction events in the geologic past were associated with a rapid increase in atmospheric carbon dioxide, probably due to volcanism and/or thermal dissociation of marine gas hydrates. Early research focused on the climatic effects of the elevated CO2 levels on biodiversity, but in 2004, decreased CaCO3 saturation due to seawater uptake of volcanogenic CO2 was suggested as a possible kill mechanism during the marine mass extinction at the end of the Triassic. The end-Triassic biotic crisis is still the most well-established example of a marine mass extinction due to ocean acidification, because (a) volcanic activity, changes in carbon isotopes, decrease of carbonate sedimentation, and marine extinction coincided precisely in the stratigraphic record, and (b) there was pronounced selectivity of the extinction against organisms with thick aragonitic skeletons, which is predicted from experimental studies. Ocean acidification has also been suggested as a cause of the end-Permian mass extinction and the end-Cretaceous crisis.

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Ocean acidification and mass extinction events in the geologic past

Three of the big five mass extinction events in the geologic past were associated with a rapid increase in atmospheric carbon dioxide, probably due to volcanism and/or thermal dissociation of marine gas hydrates. Early research focused on the climatic effects of the elevated CO 2 levels on biodiversity, but in 2004, decreased CaCO 3 saturation due to seawater uptake of volcanogenic CO 2 was suggested as a possible kill mechanism during the marine mass extinction at the end of the Triassic. The end-Triassic biotic crisis is still the most well-established example of a marine mass extinction due to ocean acidification, because (a) volcanic activity, changes in carbon isotopes, decrease of carbonate sedimentation, and marine extinction coincided precisely in the stratigraphic record, and (b) there was pronounced selectivity of the extinction against organisms with thick aragonitic skeletons, which is predicted from experimental studies. Ocean acidification has also been suggested as a ...
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Calcification

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Overview edit Changes in ocean chemistry can have extensive direct and indirect effects on organisms and their habitats. One of the most important repercussions of increasing ocean acidity relates to the production of shells and plates out of calcium carbonate ( CaCO 3 ). This process is called calcification and is important to the biology and survival of a wide range of marine organisms. Calcification involves the precipitation of dissolved ions into solid CaCO 3 structures, such as coccoliths. After they are formed, such structures are vulnerable to dissolution unless the surrounding seawater contains saturating concentrations of carbonate ions (CO 3 2−). Mechanism edit Of the extra carbon dioxide added into the oceans, some remains as dissolved carbon dioxide, while the rest contributes towards making additional bicarbonate (and additional carbonic acid). This also increases the concentration of hydrogen ions, and the percentage increase in hydrogen is larger than the percentage in...
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References

Clarke, L.; Edmonds, J.; Jacoby, H.; Pitcher, H.; Reilly, J.; Richels, R. (July 2007). "Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations. Sub-report 2.1A" (PDF) . In U.S. Climate Change Science Program and the Subcommittee on Global Change Research (ed.). Synthesis and Assessment Product 2.1 . Washington, DC., USA: Department of Energy, Office of Biological & Environmental Research. Archived from the original (PDF) on 16 June 2013. Good, P.; Gosling, S. N.; Bernie, D.; Caesar1, J.; Warren, R.; Arnell, N. W.; Lowe, J. A. (2010). An updated review of developments in climate science research since IPCC Fourth Assessment Report (PDF) (Report). London, UK: AVOID Consortium. Report website. UK Royal Society (September 2009). Geoengineering the climate: science, governance and uncertainty (PDF) . London: UK Royal Society. ISBN  978-0-85403-773-5 , RS Policy document 10/09. Report website. UNEP (November 2010). The Emissions Gap Report: Are the Copenh...
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