SGER: Controls on Li/Ca Uptake in Planktic Foraminifera Determined by Live Culturing

浮游有孔虫对Li/Ca吸收的控制由活体养殖确定能够将海水化学和气候的变化联系起来，使我们能够读取气候变化的记录和随时间推移的变化速度。这项研究致力于开发一种新的地球化学指标，将浮游泡沫动物钙质测试中的Li/Ca比值与海水中碳酸盐离子的浓度联系起来。如果要测试的主要假设成立，开发的工具和技术将极大地扩展我们追踪海水中碳酸盐离子变化的能力，从而使大气中的二氧化碳浓度回溯到过去。它还将使我们能够监测海洋中锂的流量和来源随时间的变化，为测量海洋锂的来源(通过洋壳的热液循环与大陆风化)随时间变化提供了一种手段。这项研究将使用实验室培养实验，对一种常见的单细胞海洋生物--普通单细胞海洋生物--奥布利纳大学，它会沉淀出一个坚硬的钙质甲壳(即测试)，以确定进入测试的锂的吸收是否严格受海水中碳酸盐离子浓度的控制。为了验证这一假说，我们将对大斑虾进行控制培养实验，以考察碳酸盐离子浓度、锂离子浓度、盐度和温度对孔洞试验中锂钙比的影响。从其中一位PI(霍尔)之前的工作中已经知道，锂并不显著地参与生物循环，因此它在测试中的浓度不会受到营养物质或生物生产力变化的影响。与生物活性元素锌相比，锂在海洋中的停留时间也相对较长，锌目前被用作碳酸盐离子代理。培养工作将在以色列埃拉特的耶路撒冷希伯来大学现场站与Jonathon Erez博士合作进行，他是此类培养实验方面的专家，最早将于2005年1月的第一周开始培养。在这些实验中培养的样本随后将在耶鲁大学进行净化，并在那里进行电感耦合等离子体质谱分析。

Controls on Li/Ca uptake in planktic foraminifera determined by live culturingBeing 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.