FORAMINIFERA IN 3D

Assessment of biodiversity is important for evaluation of the impacts of present and past climate change on ecosystems, but there is insufficient taxonomic expertise for a thorough evaluation of the validity and temporal range of taxa in many phyla, thus for a study of biodiversity during episodes of rapid environmental change.This lack is especially critical for the Foraminifera, which are not only studied as organisms, but whose calcium carbonate tests are widely used in the ongoing development of proxies that quantify environmental parameters such as temperature, ocean stratification, productivity, salinity, pH and oxygenation, and provide the basis for earth-system modeling in deep time. The proxies are based on the isotope or trace element composition of the foraminiferal test, which are strongly species-dependent, so that taxonomic knowledge is of prime importance for the selection of specimens for destructive analysis. We show that the non-destructive techniques of X-ray Computed Tomography scanning (CT-scan) and Synchrotron Radiation Tomography Microscopy (SRXTM) produce 3D images of high quality, which can be manipulated (rotated) by the viewer. These images show specimen morphology in such detail that the taxonomist does not have to observe the actual specimen in order to fully analyze its morphology. The analysis of the 3D images provides detailed information on the size and shape of the protoconch, ontogenetic development of the test, details of the test structure such as size and shape of additional apertures or apertural flaps in earlier chambers, damage by boring organisms, and details of calcification processes of the wall. In addition, these methods provide detailed information on preservation of the wall, of major importance for evaluation of validity of trace element or isotope proxies. Online availability of 3D images of type material in museum collections would be important for the paleontological community, enable it to make a major step forward in solving taxonomic problems, help in educating a new generation of taxonomists and assist geochemists in the selection of the correct specimens for analysis. References: Speijer et al., 2008, Geosphere 4: 760-763; Johnstone et al., 2010, Mar. Micropal. 77:58-70.