Being able to correlate changes in seawater chemistry and climate allows us to read the record of climate changes and rates of change back through time. This research focuses on the development of a new geochemical proxy that will link the Li/Ca ratio on the calcareous tests of planktonic foaminifera with the concentration of carbonate ion in seawater. If the primary hypotheses that are to be tested hold, the tool and techniques developed will extend significantly our ability to track changes in the carbonate ion in seawater, hence atmospheric CO2 concentrations, back through time. It will also allow us to monitor changes in the flux and source of Li in the oceans over time, providing a means for measuring how sources of oceanic lithium (hydrothermal circulation through the ocean crust versus continental weathering) have changed with time. This research will use laboratory culturing experiments on a common unicellular marine organism, Orbulina universa, that precipitates a hard calcareous carapace (i.e., test) to determine if uptake of Li into the test is controlled strictly by the carbonate ion concentration of seawater. To test this hypotheses, controlled culturing experiments on Orbulina universa will be carried out to examine the effect of carbonate ion concentration, lithium concentration, salinity, and temperature on the Li/Ca ratio of the foram test. From the previous work of one of the PIs (Hall), it is already known that lithium does not significantly participate in the biological cycle, and so its concentration in the test will not be affected by changes in nutrients or biological productivity. Lithium also has a relatively long residence time in the ocean, compared to the bioactive element, zinc, which is presently used as a carbonate ion proxy. Culturing work will be carried out at the Hebrew University of Jerusalem field station in Eilat, Israel in collaboration with Dr. Jonathon Erez who is an expert in such culturing experiments and who is set up to begin culturing as early as the first week of January, 2005. Cultured specimens grown in these experiments will be subsequently cleaned at Yale University and analyzed there by inductively coupled plasma mass spectrometry.
