Biomineralization in perforate foraminifera

In this paper, we review the current understanding of biomineralization in perforate foraminifera. Ideas on the mechanisms responsible for the flux of Ca2 + and inorganic carbon from seawater into the test were originally based on light and electron microscopic observations of calcifying foraminifera. From the 1980s onward, tracer experiments, fluorescent microscopy and high-resolution test geochemical analysis have added to existing calcification models. Despite recent insights, no general consensus on the physiological basis of foraminiferal biomineralization exists. Current models include seawater vacuolization, transmembrane ion transport, involvement of organic matrices and/or pH regulation, although the magnitude of these controls remain to be quantified. Disagreement between currently available models may be caused by the use of different foraminiferal species as subject for biomineralization experiments and/or lack of a more systematic approach to study (dis)similarities between taxa. In order to understand foraminiferal controls on element incorporation and isotope fractionation, and thereby improve the value of foraminifera as paleoceanographic proxies, it is necessary to identify key processes in foraminiferal biomineralization and formulate hypotheses regarding the involved physiological pathways to provide directions for future research

Carbon and nitrogen isotopic composition of different strains of <i>Artemia</i> sp.

Stable carbon and nitrogen isotope ratios have been determined on 41 strains of Artemia sp. from different geographic regions around the world. The delta 13C and delta 15N values ranged between -13.7 to -25.0 per mil and -0.7 to 21.2 per mil respectively. Artemia delta 13C values from coastal environments are consistent with a marine origin for the food source. Artemia from inland salt lakes have a range of carbon isotope values suggesting C3, C4 and CAM based organic matter could form the base of the Artemia food chain. These data indicate that Artemia having a wide range of carbon and nitrogen isotope values are available for trophodynamic research studies that quantify the effect of respired CO2 on tissue and CaCO3 shell 13C/12C ratios. Such stable isotope variation also suggests that stable isotope fingerprinting remains a viable technique for identifying specific Artemia collection sites