Dynamics of dissolved organic nitrogen in the ocean obtained by using high-sensitive and high-resolution method

建立了一种高灵敏度、高分辨率的海水溶解有机氮(DON)测定方法，该方法由高温燃烧装置和化学发光检测器组成。国际海水DON测量仪器比对项目证实，该系统具有较高的性能，可获得准确、珍贵的海水DON数据。利用该系统，获得了DON在不同海区的详细分布和孵化实验中DON的生物过程：西北太平洋西部165E经线和Oyashio地区A线的表层海洋，东京湾荒川口的表层海洋，以及西部表层水域DON的微生物分解过程。北太平洋和珊瑚释放DON的过程。设计了DON同时测定溶解有机碳(DOC)的系统，实现了DOC与DOC动力学的直接比较，并讨论了溶解有机物(DOM)的C/N比特性。结果发现，相对富C的DOM在贫营养区和非生产季稳定积累，而富N的DOM在高纬度地区特别是在生产季呈暂时性积累。一些海洋样品中的总溶解氨基酸(TDAA)是典型的含氮有机化合物，也是DON的主要可识别成分。得到了氨基酸碳(TDAA-C)与DOC的比例(0.8-1.8%)和氨基酸氮(TDAA-N)与DON的比例(8-18%)。TDAA-C/DOC和TDAA-N/DON的比值均呈现出高纬度产区高、低纬贫养区低的趋势，说明产区DOM含有更多的生物质和新鲜成分，而变化的成分主要是贫养区的DOM。

A high-sensitive and high-resolution method for measuring dissolved organic nitrogen (DON) in seawater has been established, which consists of a high-temperature combustion unit and a chemiluminescence detector. The international program for instrument comparison for measurement of DON in seawater confirmed that this system has a high performance to obtain accurate and precious data of DON in seawater. By using this system, the detailed distribution of DON in a variety of sea area and biological processes of DON in incubation experiments were obtained as follows: surface oceans in the western North Pacific along 165 E longitude and along A line of Oyashio region, Arakawa estuary in Tokyo Bay, and microbial decomposition process of DON in surface waters in the western. North Pacific and release process of DON by coral. The system is designed for simultaneous measurement of dissolved organic carbon (DOC) with DON, so that it has been made possible that DON dynamics is directly compared with those of DOC, and characteristics of C:N ratio of dissolved organic matter (DOM) is discussed. Consequently it was found that relatively C-rich DOM was stably accumulating in oligotrophic area and unproductive season, whereas N-rich DOM was temporally accumulating in high latitude area especially in productive season. Amino acids in DOM (Total Dissolved Amino acids: TDAA), as typical nitrogenous organic compounds and most major identifiable component of DON, were also determined for some oceanic samples. The proportions of amino acids' carbon (TDAA-C) to DOC (0.8-1.8%) and amino acids' nitrogen (TDAA-N) to DON (8-18%) were obtained. Both proportions of TDAA-C/DOC and TDAA-N/DON showed a tendency to be high in productive area of high latitude and low in oligotrophic area of low latitude, suggesting DOM in productive area contained more biogenic and fresh components, whereas more altered components mainly composed DOM in oligotrophic area.