The significance of radiolarian isotopic signals for paleoceanographic reconstructions

该研究旨在进一步发展基于放射虫和硅藻蛋白石中硅同位素（δ 30 Si）重建过去营养盐利用和生产力的新方法。这种重建对于了解南大洋等生物蛋白石沉积强烈的地区过去的养分和碳循环及其对全球生物地球化学循环和气候发展的影响至关重要。目前，我们已经开始了为期一年的资助研究（2006年11月），这将集中于建立同位素记录的沉积物岩心PS2498-1和PS1778-5，分别位于亚南极洲和南极洋的极锋区。这将提供第一个信息的冰川间冰期变化在不同的南大洋区和异养和自养硅质微型浮游生物。根据审查员的建议，将在第二年（本报告要求）对南大洋大西洋、印度洋和太平洋部分不同物理和生物环境的表层沉积物进行系统研究，以加强这项开创性研究。这将包括对来自特定大小级别放射虫和硅藻的δ 30 Si信号的调查以及放射虫普查。拟议的项目将提供有关硅质微生物同位素信号纬度变化的第一个信息，并与南大洋不同的水文和生物状况进行比较。这些结果将为硅质浮游生物同位素记录的古海洋学解释提供基础参考。这项研究是2007/08国际极地年BIPOMAC（“两极气候机制”）网络的一部分，旨在记录和破译调节气候发展和变化的极地过程。

The proposed study aims to further develop the novel approach to reconstruct past nutrient utilization and productivity based on silicon isotopes (δ30Si) from radiolarian and diatom opal. Such reconstruction is crucial for the understanding of past nutrient and carbon cycling in areas characterized by strong deposition of biogenic opal, such as the Southern Ocean, and its effect on global biogeochemical cycles and climate development. Currently we have started the funded one-year study (November 2006), which will concentrate on the establishment of isotope records from sediment cores PS2498-1 and PS1778-5, located in the Subantarctic and the Polarfront Zone of the Atlantic Southern Ocean, respectively. This will provide first information on glacial-interglacial variability in different Southern Ocean zones and from heterotrophous and autotrophous siliceous microplankton. Following the reviewer’s suggestions, this pioneering study will be augmented during a second year (requested herein) by the systematic study of surface sediments from different physical and biological settings in the Atlantic, the Indian and the Pacific sectors of the Southern Ocean. This will include the investigation of the δ30Si signal from specific size class radiolarians and diatoms as well as a radiolarian census. The proposed project will provide the first information about latitudinal changes of isotopic signals in siliceous microorganisms in comparison to the different hydrographic and biological regimes of the Southern Ocean. Such results will provide the basic reference for further paleoceanographic interpretation of siliceous microplankton isotope records. This study is part of the International Polar Year 2007/08 BIPOMAC (“Bipolar Climate Machinery”) network aimed to document and decipher polar processes regulating climate development and variability.