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

海洋固碳过程中CO2（aq）与碳同位素分馏之间的关系对保存沉积物中气候驱动的同位素特征起着重要作用。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CO2（aq）、养分浓度、温度、初级生产速率和物种组成。然后，海洋中微粒物质的沉积将部分同位素信号转移到沉积物中，在沉积物中，同位素信号可以用作推断过去环境条件的代理。决定光合同位素分馏（ep）的因素将在CO2（aq）和ep之间没有普遍适用关系的假设背景下进行研究。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以记录各种ep - CO2（aq）关系。本研究将使用三个明显不同的环境：1)在缅因湾和马尾藻海之间的北大西洋；2)北纬12度至南纬12度、西经140度之间的赤道太平洋；3)秘鲁上升流区。选定的生物标志物的同位素组成将通过天气测量温度、CO2（aq）、节段13c DIC、营养物质和浮游生物物种组成来解释。这些信息将使重建海洋沉积物中的古环境记录成为可能，并将为未来使用生物标志物和同位素联合技术评估海洋-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.