Benthic Carbon Oxidation, Denitrification, and Nitrogen Isotope Fractionation in Continental Margin Sediments

将研究太平洋西北海岸和墨西哥西部海岸的大陆坡和更深的大陆边缘沉积物中的底栖碳氧化、反硝化和底栖通量。 华盛顿州附近的先前工作表明，预计碳雨沉积物中的大量碳被从陆架上扫走，并且没有在上坡上积累或氧化。 其他人提出，大陆坡底部附近沉积物中的碳氧化异常高，这些沉积物占整个洋盆沉积物代谢的主要部分。 由于高沉积碳氧化经常伴随着反硝化，因此斜坡和较深沉积物中的反硝化在海洋综合氮预算中可能很重要。 需要解决的具体问题是：1）斜坡和较深的大陆边缘沉积物中的碳氧化速率和相关的底栖通量是多少，速率是否异常高，通量与深度、离岸距离和溶解氧等变量之间是否存在关系？ 2）这些沉积物中反硝化的程度是多少？ 3）反硝化过程中同位素分馏的大小是多少？它是否取决于反硝化是发生在沉积物中还是在水体中？

Benthic carbon oxidation, denitrification, and benthic fluxes will be studied in continental slope and deeper continental margin sediments off the Pacific Northwest coast and the coast of western Mexico. Previous work off Washington State indicates that a significant amount of the expected carbon rain to shelf sediments is swept off the shelf and is not accumulating or being oxidized on the upper slope. Others have suggested carbon oxidation in sediments near the base off the continental slope is anomalously high and that these sediments account for a major portion of the total ocean basin sediment metabolism. As high sedimentary carbon oxidation is frequently accompanied by denitrification, denitrification in slope and deeper sediments could be important in the marine combined nitrogen budget. Specific questions to be addressed are: 1) What are the carbon oxidation rates and associated benthic fluxes in slope and deeper continental margin sediments, are rates anomalously high, and are there relationships between flux and variables such as depth, distance from shore, and dissolved oxygen? 2) What is the magnitude of denitrification in these sediments? and 3) What is the magnitude of the isotopic fractionation during denitrification and does it depend on whether the denitrification takes place in the sediments or in the water column?