SGER: Improving the Utility of Paleoproxies from Coccolith Chemistry: Calibration and Analytical Advances

本项目申请经费用于开发一种基于球石方解石元素化学（Sr/Ca）的球石藻古生产力新指标。对赫胥利Emiliania huxleyi单一物种的培养研究，以及对上升流区两个样带沉积物岩心顶部的球岩石的分析表明，球岩石Sr/Ca比值随营养刺激下球岩石生长速率的变化而变化。然而，目前尚不清楚这些反应是否在海洋中广泛存在，球粒石中Sr/Ca的变化是由营养物质浓度引发的还是由营养物质对生长速度的影响引发的，是某种特定的营养物质造成了这种影响，还是营养物质限制的总体状态驱动了这种反应，以及这些反应在不同物种中是否相同。校准研究将通过对另外三种物种（Calcidiscus leptoporus、cocolithus pelagicus和Gephyrocapsa oceanica）进行营养限制培养，以及在营养刺激的水华事件发生之前、期间和之后对浮游生物和沉积物捕集器样本进行时间序列分析。浮游生物样本和一些沉积物陷阱中收集的非常少量的物质只能通过开发一种新的离子探针（SIMS）技术来分析，这种技术能够精确测量单个或小组10-20个采摘的球岩石的Sr/Ca。除了改进指示剂的校准外，SIMS离子探针技术还有助于对下岩心沉积物进行Sr/Ca分析，以确定古生产力，因为它可以消除非碳酸盐相的元素贡献，并允许对给定物种或属的纯样品进行Sr/Ca测定。

This SGER request funding to develop a new indicator of paleo-productivity of coccolithophorid algae, based on elemental (Sr/Ca) chemistry of coccolith calcite. Culture studies of a single species, Emiliania huxleyi, and analysis of coccoliths from sediment core tops in two transects across upwelling areas, suggest that coccolith Sr/Ca ratios vary with nutrient-stimulated changes in coccolithophorid growth rates. However, it is unclear whether these responses are widespread in the ocean, whether Sr/Ca variations in coccoliths are triggered by nutrient concentrations or the effect of nutrients on growth rate, whether a particular nutrient is responsible for this effect or if the state of nutrient limitation in general drives the response, and whether these responses are the same for different species. Calibration studies will be conducted through nutrient-limited culture of three additional species (Calcidiscus leptoporus, Coccolithus pelagicus, and Gephyrocapsa oceanica) and by analysis of time series plankton and sediment trap samples before, during, and after nutrient-stimulated bloom events. The very small amount of material collected in plankton samples and some sediment traps can be analyzed only through the development of a new ion probe (SIMS) technique capable of precise Sr/Ca measurements of individual or small groups of 10-20 picked coccoliths. In addition to improving calibration of the indicator, the SIMS ion probe technique will also benefit Sr/Ca analysis of downcore sediments for paleoproductivity determinations because it would eliminate elemental contributions from noncarbonate phases and permit determinations of Sr/Ca on pure samples of a given species or genera.