Chlorophyll dN-15: An Isotopic Benchmark for Understanding N Cycling and Paleochemistry in the Mediterranean Sea

摘要近年来关于海洋沉积物中氮分布的研究为追踪海洋氮循环的变化提供了令人兴奋的前景，包括古生产力和古硝化作用的变化。这些发展显示出极大的希望，可以增加我们对海洋生产的大规模控制、沉积物中的碳保存以及气候和地球化学循环之间相互作用的理解。在本项目中，首席研究员将重点关注沉积氮同位素在古海洋学研究中使用的主要障碍：即沉积N15记录上早期成岩作用的巨大且不可量化的印记。具体来说，他将继续研究沉积叶绿素-a的N15组成，作为影响地表水营养动态过程的示踪剂。这种方法应该比使用N15来研究大块沉积有机质更可靠，因为N15的地表条件特征与沉积后沉积物表面氮化学的变化有关。

Repet702 ABSTRACT Recent reports of nitrogen distribution in marine sediments offer the exciting prospect of tracking changes in the marine nitrogen cycle through time, including changes in paleoproductivity and paleonitrification. These developments show great promise in adding to our understanding of large-scale controls on marine production, carbon preservation in sediments, and the interplay between climate and geochemical cycling. In this project, the principal investigator will focus attention on the main impediment to using sedimentary nitrogen isotopes in paleo- oceanographic studies: namely, the large and non-quantifiable imprint of early diagenesis on the sedimentary N15 record. Specifically he will continue his studies of the N15 composition of sedimentary chlorophyll-a as a tracer for processes affecting surface water nutrient dynamics. This approach should be more reliable that using N15 for bulk sedimentary organic matter in which the N15 signature of surface conditions is convoluted with post-depositional changes in nitrogen chemistry since deposition at the sediment surface.