Biological productivity in the ocean directly influences the partitioning of carbon between the atmosphere and ocean interior. Through this carbon cycle feedback, changing ocean productivity has long been hypothesized as a key pathway for modulating past atmospheric carbon dioxide levels and hence global climate. Because phytoplankton preferentially assimilate the light isotopes of carbon and the major nutrients nitrate and silicic acid, stable isotopes of carbon (C), nitrogen (N), and silicon (Si) in seawater and marine sediments can inform on ocean carbon and nutrient cycling, and by extension the relationship with biological productivity and global climate. Here, we compile water column C, N, and Si stable isotopes from GEOTRACES-era data in four key ocean regions to review geochemical proxies of oceanic carbon and nutrient cycling based on the C, N, and Si isotopic composition of marine sediments. External sources and sinks as well as internal cycling (including assimilation, particulate matter export, and regeneration) are discussed as likely drivers of observed C, N, and Si isotope distributions in the ocean. The potential for C, N, and Si isotope measurements in sedimentary archives to record aspects of past ocean C and nutrient cycling is evaluated, along with key uncertainties and limitations associated with each proxy. Constraints on ocean C and nutrient cycling during late Quaternary glacial-interglacial cycles and over the Cenozoic are examined. This review highlights opportunities for future research using multielement stable isotope proxy applications and emphasizes the importance of such applications to reconstructing past changes in the oceans and climate system.

中文翻译：

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评估 C、N 和 Si 同位素作为过去海洋养分和碳循环的示踪剂

海洋中的生物生产力直接影响大气和海洋内部之间的碳分配。通过这种碳循环反馈，不断变化的海洋生产力一直被假设为调节过去大气二氧化碳水平以及全球气候的关键途径。由于浮游植物优先吸收碳的轻同位素以及主要营养物质硝酸盐和硅酸，因此海水和海洋沉积物中碳 (C)、氮 (N) 和硅 (Si) 的稳定同位素可以为海洋碳和养分循环提供信息，以及与生物生产力和全球气候的关系。在这里，我们编译水柱C，N，和 Si 稳定同位素来自四个关键海洋区域的 GEOTRACES 时代数据，以根据海洋沉积物的 C、N 和 Si 同位素组成审查海洋碳和养分循环的地球化学代理。外部源和汇以及内部循环（包括同化、颗粒物输出和再生）被讨论为海洋中观察到的 C、N 和 Si 同位素分布的可能驱动因素。评估了沉积档案中 C、N 和 Si 同位素测量记录过去海洋 C 和养分循环方面的潜力，以及与每个代理相关的关键不确定性和局限性。检查了晚第四纪冰期-间冰期循环和新生代期间海洋 C 和养分循环的限制。