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Friday Earth Sciences Talk

Speaker and topic: Prof. Gert-Jan Reichart (NIOZ/AW) - "Element uptake in foraminiferal shell calcite and paleoenvironmental reconstruction"

Knowledge of past climates and environments is largely based on the isotopic and element composition of fossil foraminiferal shells. Sea water parameters such as temperature, salinity and pH have been shown to control the incorporation of elements and isotopic fractionation and hence can be used as proxies for these parameters. Incorporation of elements and isotopes from sea water by foraminifera, however, markedly differs from inorganically precipitated CaCO₃, which reflects the tight biological control on calcification.

Much research has been targeted towards foraminiferal biomineralization in order to better understand trace metal incorporation in foraminiferal shell carbonate and thereby improve proxy calibrations. The cellular processes involved in calcification are still only partly identified in foraminifera and include the involvement of organic templates, trans-membrane ion transporters and proton removal.

In contrast to the chemical simplicity of calcification (i.e. Ca²⁺ + CO₃^2- -> CaCO₃), the structural, morphological, crystallographic and geochemical diversity in foraminiferal shells and skeletons is enormous. Comparing geochemical data of recent foraminifera across all known calcifying orders shows different pathways in the evolution of foraminiferal calcification. Foraminiferal orders have their own distinct geochemical fingerprint, while the evolutionary relationship between orders is absent in shell chemistry. This indicates the absence of a common, calcifying ancestor and hence suggest multiple independent inventions of calcification by foraminifera.

With the Friday Earth Sciences Talks (FEST) we intend to bring the departments of Earth Sciences and Physical Geography together. The aim is to present (mostly) Utrecht-based Earth Sciences in an accessible way in order i) to stay familiar with each other’s work across disciplines and ii) to help (in particular MSc.) students in their orientation on possible graduation specialisations and future careers. Alumni are also invited.