Under this award the PIs will culture foraminifera that reproduce and calcify and can be maintained under tightly constrained carbonate chemistry and trace element concentrations to determine environmental and physiological ("vital") influences on the shell chemistry of benthic foraminifera. Two culturing studies, will take about one year each. These are designed to address key aspects of the controls on benthic foraminiferal shell chemistry. In each year both B. aculeata from a 220-m site and also epibenthic species (e.g., Cibicidoides) from deeper-water sites will be cultured. Year 1 experiments will pursue results from work to date, and from previous culturing studies of planktic foraminifera, by investigating the influence of carbonate ion concentration on shell composition (d13C, d18O, Cd, Ba, Mg, Sr, U, V). Year 2 experiments will document the response of benthic foraminiferal trace element composition to variations in dissolved trace metal concentrations, and the response of benthic foraminiferal carbon isotopic composition to the d13C of their algal food. Substantial culturing effort (~25% of the facility and time) will be devoted in both years to exploratory studies on temperature influence on foraminiferal shell chemistry (in particular, Mg/Ca), designed to help define problems and approaches most suitable for future culture work. In addition to these culturing studies, related field-based studies of in situ foraminiferal life positions and shell composition will also be conducted. The project will benefit society at large because results will enable better paleoceanographic interpretations of past climate changes. Accurate assessments of past climate variability are necessary for confident predictions about future climate change. Such predictions, in turn, provide an essential foundation for sound policy decisions regarding anthropogenic release of CO2 and other greenhouse gases.
