天文大潮对南海北部浮游动物生物量的影响

基于2020年8月至11月在南海北部获取的声学多普勒流速剖面仪观测数据，利用后向散射强度数据估算得到相对体积散射强度并用其表征浮游动物生物量的相对大小，对相对体积散射强度的半月变化与具有半月周期的潮流动能进行相关性分析，进而分析天文大潮对声学估算的浮游动物生物量的影响。结果表明：半月周期的相对体积散射强度与潮流动能之间呈负相关关系，即天文大潮时，潮流动能较强，水体相对体积散射强度较低，浮游动物生物量则较小，天文小潮时则情况相反。初步推测其原因为：天文大潮时，强潮流一方面导致浮游动物生存环境恶化，使其生物量下降，另一方面也改变了浮游动物垂直迁移特性，浮游动物迁移到近海底处使其难以被观测。

Effect of Astronomical Tide on the Zooplankton Biomass in the Northern South China Sea

Based on the Acoustic Doppler Current Profiler observations in the northern South China Sea from August to November 2020, the relative volume scattering intensity was estimated using the backscattering intensity data and was used to characterize the variation of zooplankton biomass. The correlation analysis suggested that the semi-monthly variation of the relative volume scattering intensity was negatively correlated with the tidal current kinetic energy. That is, when the spring tide occurred, the tidal current kinetic energy was strong, the relative volume scattering intensity of water was low, and the zooplankton biomass was low, whereas the situation was opposite during the neap tide. Two possible mechanisms were believed to be responsible for the variation of the zooplankton biomass. On one hand, the strong tidal current during the spring tide caused the deterioration of the living environment of zooplankton and thus reduced its biomass. On the other hand, the strong tidal current during the spring tide changed the vertical migration characteristics of zooplankton, which migrated to the sea bottom, making it difficult to be observed.