东海颗粒有机物中的碳氮比

C/N RATIOS OF PARTICULATE ORGANIC MATTER IN THE EAST CHINA SEA

利用1994年中国JGOFS计划在东海进行的春、秋两航次的资料，分析颗粒有机物中碳氮比的变化。结果表明，春季碳氮比明显低于秋季；春季表层海水中的碳氮比分布特点是，近海小于外海，北部海域小于南部海域；秋季分布特点是，东北部海域碳氮比高，西南部海域较低。这种分布变化是生物活动、水团运动及沉积物再悬浮等因素引起的。研究还表明，仅利用碳氮比判断有机物的来源是不可靠的，必须综合其它现场因素谨慎判断。

In spring (April) and autumn (October-November), 1994, two cruises of the Chinese JGOFS were conducted in the East China Sea (ECS) on board the R/ V 'Science l' and 'Dengfanghong', respectively (Fig-1). During the invesigation period, carbon and nitrogen in POM were measured using the dry combustion method. The main results were as folows. C/N ratios in the ECS ranged from 4.02 to 26.91, with a mean value of 7.63 in spring, and from 4.75 to 34.34, with a mean value of 15.23 in autumn. The maximum C/N ratios in surface waters were observed in the south part of the ECS in spring, while they were found in the northeast part of the ECS in autumn. There were apparent links between C / N ratios and the biological activities, Kuroshio waters and sediment resuspention in the ECS. The low C / N ratio areas in both seasons coincided with those of high ATP and chlorophyll a concentrations. C / N ratios during the two cruises showed little change in the Kurshio waters, but varied greatly in the coastal waters. In the sediment resuspension areas, C / N ratios were usually high. A strong storm-caused resuspension of sediments in autumn occurred in the coastal waters and at the same area the highest C/N ratios were observed. C/ N ratio usually acts as a standard in judging the sources of POM. According to some reports, POM is from land if C/ N ratio is more than 12, and it is from sea if C/ N ratio is less than 8.However, this standard may not be safely used. In this study, the mean C/ N ratio in autumn was l5.23, but POM was not possible from land since it was found that Changjiang River, the main river carrying land materials to the ECS, had little discharge during the investigation period. The sediments resuspended from the bottom of the ECS were the possible source of POM with high C/ N ratios in autumn.