Ocean acidification in modern oceans is linked to rapid increase in atmospheric CO2, raising concern about marine diversity, food security and ecosystem services. Proxy evidence for acidification during past crises may help predict future change, but three issues limit confidence of comparisons between modern and ancient ocean acidification, illustrated from the end-Permian extinction, 252 million years ago: (1) problems with evidence for ocean acidification preserved in sedimentary rocks, where proposed marine dissolution surfaces may be subaerial. Sedimentary evidence that the extinction was partly due to ocean acidification is therefore inconclusive; (2) Fossils of marine animals potentially affected by ocean acidification are imperfect records of past conditions; selective extinction of hypercalcifying organisms is uncertain evidence for acidification; (3) The current high rates of acidification may not reflect past rates, which cannot be measured directly, and whose temporal resolution decreases in older rocks. Thus large increases in CO2 in the past may have occurred over a long enough time to have allowed assimilation into the oceans, and acidification may not have stressed ocean biota to the present extent. Although we acknowledge the very likely occurrence of past ocean acidification, obtaining support presents a continuing challenge for the Earth science community.
References
[1]
Erwin, D.H. Extinction: How Life on Earth Nearly Ended 250 Million Years Ago; Princeton University Press: Princeton, NJ, USA; Oxford, UK, 2006.
Payne, J.L.; Turchyn, A.V.; Paytan, A.; DePaolo, D.J.; Lehrmann, D.J.; Yu, M.; Wei, J. Calcium isotope constraints on the end-Permian mass extinction. Proc. Nat. Acad. Sci. USA 2010, 107, 8543–8548.
[4]
Berner, R.A.; Kothavala, Z. GEOCARB III: A revised model of atmospheric CO2 over Phanerozoic time. Am. J. Sci. 2001, 301, 182–204, doi:10.2475/ajs.301.2.182.
[5]
Gattuso, J.-P.; Hansson, L. Ocean Acidification; Oxford University Press: Oxford, UK, 2011.
[6]
IPCC Home Page, Available online: http://www.ipcc.ch/ (accessed on 19 September 2012).
[7]
Orr, J.C.; Caldeira, K.C.; Fabry, V.; Gattuso, J-P.; Haughan, P.; Lehodey, P.; Pantoja, S.; P？rtner, H.-O.; Riebesell, U.; Trull, T.; Urban, E.; Hood, M.; Broadgate, W. Research priorities for understanding ocean acidification. Oceanography 2009, 22, 182–189.
Kershaw, S.; Crasquin, S.; Li, Y.; Collin, P-Y.; Forel, M-B.; Mu, X.; Baud, A.; Wang, Y.; Xie, S.; Maurer, F.; Guo, L. Microbialites and global environmental change across the Permian-Triassic boundary: A synthesis. Geobiology 2012, 10, 25–47, doi:10.1111/j.1472-4669.2011.00302.x.
[10]
Payne, J.L.; Lehrmann, D.J.; Follett, D.; Seibel, M.; Kump, L.R.; Riccardi, A.; Altiner, D.; Sano, H.; Wei, J. Erosional truncation of uppermost permian shallow-marine carbonates and implications for Permian-Triassic boundary events. Geol. Soc. Am. Bull. 2007, 119, 771–784, doi:10.1130/B26091.1.
[11]
Kershaw, S.; Li, Y.; Crasquin-Soleau, S.; Feng, Q.; Mu, X.; Collin, P-Y.; Reynolds, A.; Guo, L. Earliest Triassic microbialites in the South China Block and other areas: Controls on their growth and distribution. Facies 2007, 53, 409–425, doi:10.1007/s10347-007-0105-5.
[12]
Kershaw, S.; Crasquin, S.; Forel, M.-B.; Randon, C.; Collin, P.-Y.; Kosun, E.; Richoz, S.; Baud, A. Earliest Triassic microbialites in ？ürük Dag, southern Turkey: Composition, sequences and controls on formation. Sedimentology 2010, 58, 739–755.
[13]
Farabegoli, E.; Perri, M.C. Millenial physical events and the end-Permian mass mortality in the western Palaeotethys: timing and primary causes. In Earth and Life, International Year of Planet Earth; Talent, J.A., Ed.; Springer: Berlin, Germay, 2012; pp. 719–758.
[14]
Flügel, E. Microfacies of Carbonate Rocks: Analysis Interpretation and Application; Springer: Berlin, Germany, 2004.
[15]
Collin, P-Y.; Kershaw, S.; Crasquin, S.; Feng, Q. Facies changes and diagenetic processes across the Permian-Triassic boundary event horizon, Great Bank of Guizhou, South China: A controversy of erosion and dissolution. Sedimentology 2009, 56, 677–693, doi:10.1111/j.1365-3091.2008.00992.x.
[16]
Wignall, P.; Kershaw, S.; Collin, P.-Y.; Crasquin, S. Erosional truncation of uppermost Permian shallow-marine carbonates and implications for Permian-Triassic boundary events: Comment. Geol. Soc. Am. Bull. 2009, 121, 954–956, doi:10.1130/B26424.1.
[17]
Heydari, E.; Hassanzadeh, J. Deev Jahi Model of the Permian–Triassic boundary mass extinction: A case for gas hydrates as the main cause ofbiological crisis on Earth. Sediment. Geol. 2003, 163, 147–163, doi:10.1016/j.sedgeo.2003.08.002.
[18]
Richoz, S.; Krystyn, L.; Baud, A.; Brandner, R.; Horacek, M.; Mohtat-Aghai, P. Permian–Triassic boundary interval in the Middle East (Iran and N. Oman): Progressive environmental change from detailed carbonate carbon isotope marine curve and sedimentary evolution. J. Asian Earth Sci. 2010, 39, 236–253, doi:10.1016/j.jseaes.2009.12.014.
[19]
Knoll, A.H.; Fischer, W.W. Skeletons and ocean chemistry: The long view. In Ocean Acidification; Gattuso, J.-P., Hansson, L., Eds.; Oxford University Press: Oxford, UK, 2011; pp. 67–82.
[20]
Hinojosa, J.L.; Brown, S.T.; Chen, J.; de Paolo, D.J.; Paytan, A.; Shen, S.-Z.; Payne, J.L. Evidence for end-Permian ocean acidification from calcium isotopes in biogenic apatite. Geology 2012.
[21]
Kershaw, S. Personal observations of samples from the Permian-Triassic boundary from the Meishan GSSP, Zhejiang, China, provided by Cao ChangQun, September 2010.
[22]
Zachos, J.C.; Rohl, U.; Schellenberg, S.A.; Sluijs, A.; Hodell, D.A.; Kelly, D.C.; Thomas, E.; Nicolo, M.; Raffi, I.; Lourens, L.J.; et al. Rapid acidification of the ocean during the Paleocene–Eocene thermal maximum. Science 2005, 308, 1611–1615.
[23]
Knoll, A.H.; Bambach, R.K.; Payne, J.L.; Pruss, S.; Fischer, W.W. Palaeophysiology and end-Permian mass extinction. Earth Planet. Sci. Lett. 2007, 256, 295–313, doi:10.1016/j.epsl.2007.02.018.
[24]
Svensen, H.; Schmidbauer, N.; Roscher, M.; Stordal, F.; Planke, S. Contact metamorphism, halocarbons, and environmental crises of the past. Environ. Chem. 2009, 6, 466–471, doi:10.1071/EN09118.
[25]
Svensen, H.; Planke, S.; Polozov, A.G.; Schmidbauer, N; Corfu, F.; Podladchikov, Y.Y.; Jamtveit, B. Siberian gas venting and the end-Permian environmental crisis. Earth Plan. Sci. Lett. 2009, 277, 490–500, doi:10.1016/j.epsl.2008.11.015.
[26]
Summerhayes, H. Dragon’s den: CO2, volcanic or anthropogenic. Geoscientist 2011, 2011, 18–21.
[27]
Egleston, E.S.; Sabine, C.L.; Morel, F.M.M. Revelle revisited: Buffer factors that quantify the response of ocean chemistry to changes in DIC and alkalinity. Glob. Biogeochem. Cycles 2010, 24, GB1002:1–GB1002:9.
[28]
Feely, R.A.; Sabine, C.L.; Lee, K.; Berelson, W.; Kleypas, J.; Fabry, V.J.; Millero, F.J. Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science 2004, 305, 362–366.
