基于声学仪器与粒径分析仪研究东海浮游动物昼夜垂直迁移过程

浮游动物的昼夜迁移活动与其种群变动和摄食节律紧密联系，浮游动物昼夜移动的研究已经成为种群动力学研究的一个重要组成部分。2013年夏季在浙江东部近海，结合声学多普勒流速剖面仪(ADCP)和激光粒径分析仪(LISST-100)等仪器进行了一次定点周日连续观测。通过声学反演方法，得到后向散射强度剖面的时间变化，结合LISST-100得到的水体悬浮物粒径谱，研究了浮游动物垂直迁移及其习性。分析发现了可能是精致真刺水蚤的一次昼夜垂直迁移过程，其在夜间进入跃层附近进食，白天蛰伏于底层低温高盐的台湾暖流水中，垂向迁移速度达到了0.05 m/s。LISST-100观测还发现在夜间跃层边界处大粒径颗粒聚集和100～150 μm大小的颗粒物的减少，水体中不同粒径的悬浮颗粒物有明显的昼夜变化节律，推测水体中不同层次生物群落结构存在昼夜差异。

The diel vertical migration of zooplankton observed by an acoustic Doppler current profiler and particle size analyzer in the East China Sea

The diel migration of zooplankton is closely related to the population fluctuation and feeding rhythm, and the study on the diel migration of zooplankton has become an important part of their community dynamics. In the present study, the diel vertical migration of zooplankton was studied by acoustic Doppler current profiler (ADCP) and laser particle analyzer (LISST-100) over 24 h off the coast of Zhejiang Province in summer 2013. The time series of backscatter coefficient (S_v) calculated by ADCP echo intensity and particle size spectrum from LISST-100 are used to study the vertical migration of zooplankton and its characteristics. Euchaeta concinna showed a remarkable diurnal vertical migration with a mean vertical speed is about 0.05 m/s. It feed in the thermocline at night, and hide in the bottom Taiwan warm water at daytime. It can be found from particle size spectrum that the large particle aggregate, meanwhile particles with size of 100-150 μm decrease in the thermocline at the night. The particle size of suspended particles has obvious diel rhythms in the water column, which indicate that there should be diurnal variation of biological community structure in different water level.