2008年夏季白令海粒度分级叶绿素a和初级生产力

The size-fractionated chlorophyll a concentration and primary productivity in the Bering Sea in the summer of 2008

2008年7月我国第三次北极科学考察中在白令海不同区域设立BR断面、NB断面和BS断面,对200 m以浅海水进行叶绿素a浓度和初级生产力的现场观测,对部分观测站进行微型、微微型光合浮游生物的粒级结构分析,结果表明,在白令海叶绿素a和初级生产力区域性特征明显,深海海盆中BR断面表层叶绿素a浓度为0.190～0.976μg/dm3,平均值为0.442μg/dm3;在陆架区表层叶绿素a浓度为0.142～22.405μg/dm3,平均值为2.077μg/dm3;在BR断面叶绿素浓度大大低于陆架区的NB断面和BS断面;50 m以浅真光层上部浅水层的叶绿素浓度高于真光层下部深层水,观测站叶绿素a浓度最大值大多出现在30～40 m水层;水柱平均叶绿素a浓度呈现白令海峡大于白令陆架区大于白令海盆区大于北太平洋西部海域大于白令陆坡区的区域性分布特征;在8个观察站真光层内潜在初级生产力(C)为0.173～0.918 mg/(m3.h),平均初级生产力为0.50 mg/(m3.h));陆架海区的初级生产力高于深海区;光合作用同化指数为0.29～1.03 mg/(mg.h),平均生产力指数为0.74 mg/(mg.h);观测区浮游生物细胞以粒径小于20μm的微型加微微型浮游生物居重要位置,两者对总叶绿素a浓度和总初级生产力的贡献率分别为45.08%和69.48%,细胞粒径大于20μm的微小型浮游生物对总叶绿素a浓度和初级生产力的贡献率分别为54.92%和30.52%,其中陆架区微小型对总叶绿素a浓度的贡献率高于60%。

Investigations of standing stock of phytoplankton（chlorophyll a） and primary productivity were carried out in Sections BR,NB and BS in the Bering Sea between 53°16.8′～66°00′N and 170°00′E～167°30′W during the 3nd Chinese arctic research expedition in July 2008.The size-fractionated chlorophyll a concentration and primary productivity were determined at some surveyed stations.The results show that the chlorophyll a concentration and the primary productivity appear obviously to be areal characteristics.The surface chlorophyll a concentration is 0.190～0.976 μg/dm3,and the average value is 0.442 μg/dm3 in the transect of BR.And the surface chlorophyll a concentration is 0.142～22.405 μg/dm3（the average value is 2.077 μg/dm3） in the continental shelf zone.The chlorophyll a concentration in the transect BR is lower than that in the transects NB and BS.The chlorophyll a concentration above the depth 50 m is higher than that below the depth 50 m,The maximum concentrations appear in the depth 30～40 m.The potential primary productivities（C） vary from 0.173 to 0.918 mg/（m3·h） in the surveyed area,with the average rate of 0.50 mg/（m3·h）.The primary productivity in the continental shelf zone is much higher than that of the deep water zone.The assimilation index of photosynthesis is 0.29～1.03 mg/（mg·h） in the surveyed area,with the average rate of 0.74 mg/（mg·h）.The results of the size-fractionated chlorophyll a and the primary productivity show that the nanoplankton and picoplankton account for 45.08% of the majority of the total chlorophyll a and 69.48% of total primary productivity in the surveyed area.The contributions of the microplankton to the total chlorophyll a and primary productivity are 54.92% and 30.52%,respectively.The nanoplankton and picoplankton play an important role in the ecosystem of the surveyed area.