Evidence for a multi-species coccolith volume change over the past two centuries: understanding a potential ocean acidification response

Major questions surround the species-specific nature of coccolithophore calcification in response to rising atmospheric CO2 levels. Here we present CaCO3 particle volume distribution data from the coccolith size-fraction of a rapidly accumulating North Atlantic sediment core. Without direct volume measurements on coccoliths produced by individual coccolithophore species, and knowledge of organic, as well as inorganic carbon production, it is not possible to state conclusively the coccolithophore calcification change at this site. However, by analysing the size distribution of CaCO3 particles in the less than 10 μm sediment fraction, we demonstrate a changing particle volume since the late 20th Century consistent with an increase in the mass of coccoliths produced by the larger coccolithophore species, and potentially a decrease in mass of coccoliths produced by the smaller species, present at this location. This finding has significant implications for the realistic representation of an assemblage-wide coccolithophore CO2-calcification response in numerical models.Citation: Halloran, P. R. et al. (2008). 'Evidence for a multi-species coccolith volume change over the past two centuries: understanding a potential ocean acidification response', Biogeosciences, 5(6), 1651-1655. [Available at http://www.biogeosciences.net/5/1651/2008/]. © Authors 2008. This work is distributed under the Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/). This permits the copying, distribution, transmission and adaption of the work, provided the original authors are credited. For any reuse or distribution, you must make clear to others the license terms of this work. These conditions may be waived if you get permission from the copyright holder. N.B. An earlier version of this article, published in Biogeosciences Discussions, is also available in ORA