Silicic-Acid Dependence of Oxygen-Isotope Fractionation in Diatom Opal and its Bearing on Isotopic Paleoclimatology

新的分析方法使硅藻二氧化硅的高质量、可重复性的18O/16O分析成为可能。这些技术可以应用于海洋和湖泊环境中的硅藻质沉积物，以获得有关古气候和气候变化的详细信息。然而，一些证据表明，生物成因蛋白石和水之间氧同位素的分馏可能受到动力学控制。如果是这样，硅藻18O可能部分取决于硅藻从中提取二氧化硅的水的硅酸含量。由于古代湖泊和海洋的二氧化硅浓度很少为人所知，如果存在对硅酸的依赖，可能会降低原本很有希望的古温度表的精度。在本次调查中，将培养海洋和湖泊硅藻，以了解它们的18O是否取决于环境水中的硅酸含量。如果发现了依赖关系，将建立动力学分馏模型。硅藻是古水文研究中有价值的信息来源。

New analytical approaches have made possible the high quality, reproducible 18O/16O analysis of diatom silica. These techniques could be applied to diatomaceous sediments from oceanic and lacustrine environments to obtain detailed information on paleoclimate and climate change. However, some evidence suggest that the fractionation of oxygen isotopes between biogenic opal and water may be kinetically controlled. If so, diatom 18O may depend partly on the silicic acid content of the water from which diatoms extract their silica. Because the silica concentration of ancient lakes and seas would seldom be known, a silicic-acid dependence--if on exists--could diminish the precision of an otherwise promising paleothermometer. In this investigation, marine and lacustrine diatoms will be cultured to learn whether their 18O depends on the silicic acid content of the environmental water. A kinetic fractionation model will be developed if a dependence is found. Diatom silica is valuable source of information having application to paleohydrologic studies.