Climate Change and Earth-Ocean-Atmosphere Systems
Calcification of coccolithophores and foraminifera.
The ratios of minor elements (e.g. magnesium and strontium) to calcium in foraminiferal and coccolithophore calcite are widely used as proxies, i.e. stand-in variables, for environmental and cellular parameters such as temperature and growth rate. The calibration of these proxies relies on empirical relationships to convert proxy values to target values. In practice it is often difficult to apply a given proxy because the latter is, more often than not, subject to secondary influences, i.e. environmental parameters other than the target variable. A reliable interpretation of proxy signals, therefore, requires an understanding of the physiological and inorganic processes leading to incorporation of trace elements into biogenic calcite.
My research centres on the calcification of coccolithophores and foraminifera; in particular the fractionation of stable isotopes (calcium, oxygen) and trace elements (strontium, barium & magnesium) during the calcification process. I'm also studying the dependence of isotope and trace element fractionation on environmental parameters in laboratory experiments. This work will allow me to constrain the processes involved in calcification. A better understanding of the calcification process will improve our capacity to interpret the fractionation of isotopes and trace elements. In order to gain a better understanding of the ion-transport processes involved in calcification of foraminifera as well as the morphogenesis of coccoliths I have recently added cell biological experiments to my work.
I'm also working on the effects of altered carbonate chemistry of seawater on the calcification of coccolithophores and foraminifera.
1) Light micrograph of the benthic foraminifer Ammonia tepida.
2) Scanning electron micrograph of the coccolithophore Calcidiscus leptoporus.