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Once Upon a Time Coccolithophores Thrived in Acidifying Oceans

Paper Reviewed
Meier, K.J.S., Berger, C. and Kinkel, H. 2014a. Increasing coccolith calcification during CO2 rise of the penultimate deglaciation (Termination II). Marine Micropaleontology 112: 1-12.

Writing as background for their intriguing study, Meier et al. (2014a) state that "in natural assemblages, varying seawater carbonate chemistry and environmental factors can influence both coccolithophore calcification and the composition of the coccolithophore assemblages," citing Beaufort et al. (2011) and Meier et al. (2014b), while also noting in this regard that Emiliania huxleyi has been known to develop or evolve "morphotypes with different weights or sizes adapted to diverse environmental conditions," additionally citing Flores et al. (2010).

In light of these facts, the three researchers set out to see how E. huxleyi coccolithophores responded to the rising temperature and atmospheric CO2 concentration of the penultimate glacial termination (T II), as expressed in two sediment cores extracted from the North Atlantic Ocean: one at the temperate Rockall Plateau and one in the tropical Florida Strait.

At both study sites, Meier et al. (2014a) report that mean coccolithophore weight "strongly increases during Termination II." At the Florida Strait, in fact, they found that coccolith weight actually doubled during Termination II (see Figure 1 below), which they say was "partly due to an assemblage shift towards larger and heavier calcifying morphotypes, but mainly an effect of increasing coccolithophore calcification," which they additionally say "is exactly mirroring the rise in atmospheric CO2."

Such findings suggest CO2-induced global warming and ocean acidification may not be nearly as dreadful a two-pronged phenomenon as is often claimed. In fact, it can actually be helpful in certain situations, of which the situation studied by Meier et al. (2014a) is one of the more dramatic ones.

Figure 1. Mean coccolith weight from the Florida Strait across Termination II plotted with atmospheric CO2 concentrations from the Vostok ice core, Antarctica. Adapted from Meier et al. (2014a)

Beaufort, L., Probert, I., de Garidel-Thoron, T., Bendif, E.M., Ruiz-Pino, D., Metzl, N., Goyet, C., Buchet, N., Coupel, P., Grelaud, M., Rost, B., Rickaby, R.E.M. and de Vargas, C. 2011. Sensitivity of coccolithophores to carbonate chemistry and ocean acidification. Nature 476: 80-83.

Flores, J.A., Colmenero-Hidalgo, E., Mejia-Molina, A.E., Baumann, K.-H., Henderiks, J., Larsson, K., Prabhu, C.N., Sierro, F.J. and Rodrigues, T. 2010. Distribution of large Emiliania huxleyi in the Central and Northeast Atlantic as a tracer of surface ocean dynamics during the last 25,000 years. Marine Micropaleontology 76: 53-66.

Meier, K.J.S., Beaufort, L., Heussner, S. and Ziveri, P. 2014b. The role of ocean acidification in Emiliania huxleyi coccolith thinning in the Mediterranean Sea. Biogeosciences 11: 2857-2869.

Posted 10 March 2015