How does rising atmospheric CO2 affect marine organisms?

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Ocean Acidification and Marine Coccolithophores
Halloran, P.R., Hall, I.R., Colmenero-Hidalgo, E. and Rickaby, R.E.M. 2008. Evidence for a multi-species coccolith volume change over the past two centuries: understanding a potential ocean acidification response. Biogeosciences 5: 1651-1655.

Several months ago, Iglesias-Rodriguez et al. (2008) determined there had been a 40% increase in oceanic coccolith mass over the past 220 years based on data obtained from a sediment core extracted from the subpolar North Atlantic Ocean, over which period of time the atmosphere's CO2 concentration had risen by approximately 90 ppm, which finding was further found by them to be consistent with the results of several batch incubations of the far-ranging coccolithophore species Emiliania hyxleyi that they conducted while bubbling air of a number of different atmospheric CO2 concentrations through the culture medium they employed for that purpose.

What was done
Working with materials derived from the same sediment core, Halloran et al. analyzed the size distribution of CaCO3 particles in the less-than-10-Ám sediment fraction over the past quarter-century.

What was learned
This work revealed, in the researchers' words, "a changing particle volume since the late 20th century consistent with an increase in the mass of coccoliths produced by the larger coccolithophore species," which included Oolithotus fragilis, Calcidicus leptoporus, Coccolithus pelagicus var. pelagicus, and Helicosphaera carteri.

What it means
Halloran et al. say their data suggest that "in the real ocean the larger coccolithophore species increase their calcification in response to anthropogenic CO2 release," contrary to what typically occurs in the lifeless "virtual ocean" of certain theoreticians, who see bad consequences in nearly everything that could possibly be related to the historical rise in the air's CO2 concentration. They also state that "such a calcification response could be attributed to an alleviation of CO2 limitation in species that partly rely on the diffusive supply of dissolved carbon dioxide for photosynthesis, as demonstrated by a rise in photosynthetic efficiency with increasing carbon dioxide in cultures of E. huxleyi (Rost et al., 2003)."

Iglesias-Rodriguez, M.D., Halloran, P.R., Rickaby, R.E.M., Hall, I.R., Colmenero-Hidalgo, E., Gittins, J.R., Green, D.R.H., Tyrrell, T., Gibbs, S.J., von Dassow, P., Rehm, E., Armbrust, E.V. and Boessenkool, K.P. 2008. Phytoplankton calcification in a high-CO2 world. Science 320: 336-340.

Rost, B., Riebesell, U., Burkhart, S. and Sultemeyer, D. 2003. Carbon acquisition of bloom-forming marine phytoplankton. Limnology and Oceanography 48: 55-67.

Reviewed 1 April 2009