白令海颗粒有机碳输出通量的初步研究

PRELIMINARY STUDY ON PARTICULATE ORGANIC CARBON EXPORT FLUXES IN THE BERING SEA

测定了中国第2次北极科学考察期间(2003年7—9月)得到的白令海海域2个站位海水样品中溶解态及颗粒态234Th,238U和颗粒有机碳的含量。溶解态、颗粒态及总234Th的放射性在真光层中显著低于母体238U的放射性,总的234Th与238U在水深大于100m时趋于放射性平衡。BR03站位200m层位出现234Th的过量现象,可能是由于颗粒物再矿化造成的。利用234Th/238U在上层水体中的不平衡,估算了白令海上层水体真光层中234Th的平均停留时间和输出通量,并结合一维不可逆稳态模型估算出颗粒有机碳从真光层中的输出通量分别为11.66和11.69mmolC·m-2.d-1,大约分别占初级生产力的50%和59%,可能由于较大个体的浮游植物特别是硅藻的存在而造成。结果为进一步弄清白令海在全球碳循环中的作用提供了参考依据。

During the Second Chinese National Arctic Expedition from July to September of 2003, depth profiles of dissolved and particulate ~Th in upper water columns were collected at two stations in the Bering Sea. Thorium-234 was sampled by using a traditional Fe（ OH）3 co-pre- cipitation technique, which is a reliable approach to ~Th measurement. We observed Z^4Th ex- cess at station BR03 below the euphotic zone, which is possibly due to the intensive reminera- lization of particulate matter. mensional irreversible steady Particulate organic carbon （POC） was estimated from a one-di- state model of Z34Th fluxes together with measurements of the POC/~4Th ratio on the suspended particles. The POC export fluxes from the euphotic zone are 11.66 and 11.69 mmol C ~ m-2 ~ d-1. The ratios of POC fluxes to primary production in the Bering Sea are about 0.5 and 0.59, probably due to the presence of large phytoplankton （ in particular diatoms）. The results will be helpful in understanding the role of the Bering Sea in the global carbon cycle.