Collaborative Research: Controls on the Photosynthetic Isotope Effect in the Ocean: The Roles of CO2, Productivity and Species

韦克汉姆/弗里曼9401765/9412739二氧化碳(AQ)与海洋固碳过程中碳同位素分馏之间的关系在保存沉积物中气候驱动的同位素特征方面发挥着重要作用。众所周知，光合作用过程中碳同位素的分馏取决于许多因素，包括二氧化碳(AQ)、营养浓度、温度、初级生产力和物种组成。海洋中部分物质的沉积然后将这种同位素信号的一部分转移到沉积物中，在那里同位素信号可以用作推断过去环境条件的代理。决定光合作用同位素分馏(Ep)的因素将在假设二氧化碳(AQ)和Ep之间没有普遍适用的关系的背景下进行考察。相反，区域环境条件是关键的控制因素，不同的分子生物标志物可能记录各种EP-CO2(AQ)关系。研究中将使用三个明显不同的环境：1)缅因湾和马尾藻海之间的北大西洋；2)北纬12度至西经12度S之间的赤道太平洋；3)秘鲁上升区。选定生物标志物的同位素组成将通过对温度、二氧化碳(AQ)、13C DIC段、营养物和浮游植物种类组成的天气测量来解释。这些信息将使重建海洋沉积物中的古环境记录成为可能，并将为今后利用生物标志物和同位素综合技术评估海洋-气候关系提供基础。

WAKEHAM/FREEMAN 9401765/9412739 The relationship between CO2(aq) and the fractionation of carbon isotopes during carbon fixation in the ocean plays a major role in preserving climatically-drive isotopic signatures in sediments. It is known that the fractionation of carbon isotopes during photosynthesis is dependent on a number of factors, including CO2(aq) , nutrient concentrations, temperature, rate of primary production, and species composition. Sedimentation of partculate matter in the ocean then transfers part of this isotopic signal to the sediments, where the isotopic signal may be used as a proxy for inferring past environmental conditions. Factors which determine the photosynthetic isotope fractionation (ep) will be examined in the context of the hypothesis that there is no generally applicable relationship between CO2(aq) and ep. Rather, regional environmental conditions are critical control and different molecular biomarkers may record a variety of ep - CO2(aq) relationships. Three markedly different environments will be used in the study 1) the North Atlantic between the Gulf of Maine and the Sargasso Sea; 2) the equatorial Pacific between 12 degree N and 12 degress S at 140 degree W; and 3) the Peru upwelling area. Isotopic compositions of selected biomarkers will be interpreted using synoptic measurements of temperature, CO2(aq) , segma13C DIC, nutrients and photoplankton species composition. The information will make it possible to reconstruct the paleoenvironmental record in marine sediments and will provide a basis for future assessments of ocean-climate relationships using combined biomarker and isotope techniques.