北黄海獐子岛海域浮游植物沉降通量的周年变化

Annual Variations in the Phytoplankton Settling Flux in the Northern Yellow Sea off Zhangzi Island

于2011年9月至2012年11月,在北黄海獐子岛邻近海域,利用德国MST24型沉积物捕集器,开展了5 d期采样频率的浮游植物组成及其沉降通量的周年变化研究。71份沉降样品共记录浮游植物51属93种,其中硅藻38属66种,是主要的沉降类群。沉降优势种主要有具槽帕拉藻(Paralia sulcata)、离心列海链藻(Thalassiosira excentrica)、布氏双尾藻(Ditylum brightwellii)、辐射圆筛藻(Coscinodiscus radiatus)、八幅辐环藻(Actinocyclus octonarius)等硅藻物种,以及小等刺硅鞭藻(Dictyocha fibula)、八幅硅鞭藻(Octactis octonaria)等硅鞭藻物种。浮游植物沉降通量变化在(6.1~169)×10~6 cells/m^2d,平均39.4×10~6 cells/m^2d,在春、秋季各出现1个高通量时段,春季峰值主要为硅藻贡献,而秋季峰值则由硅藻和硅鞭藻共同形成。沉降浮游植物作为獐子岛底播虾夷扇贝的重要饵料,其种类组成及沉降通量的周年变化,与獐子岛海域虾夷扇贝的底播、生长时节相关,以具槽帕拉藻、海链藻、圆筛藻等硅藻属种为主的食物来源和结构是扇贝重要的饵料基础。旨在通过浮游植物沉降的时间序列研究,查明獐子岛底播虾夷扇贝的饵料组成及其通量水平的周年变化特征,为该水域可持续的底播养殖提供基础资料和参考依据。

A German-made sediment trap, MST24, was deployed at 5-day intervals in the Northern Yellow Sea off Zhangzi Island from September 2011 to November 2012 for the purpose of revealing the settling phytoplankton composition and estimating the annual variations of fluxes. A total of 51 genera and 93 taxa were recorded, with diatoms（38 genera, 66 taxa） as the dominant sedimentation group. The predominant settling species were diatoms such as Paralia sulcata, Thalassiosira excentric, Ditylum brightwellii, Coscinodiscus radiatus, and Actinocyclus octonarius, as well as silicoflagellates such as Dictyocha fibula and Octactis octonaria. Total phytoplankton fluxes varied between 6.1×10^6 cells/m^2 d and 169×10^6 cells/m^2 d, averaging 39.4×10^6 cells/m^2 d. The periods of high fluxes occurred during the spring and autumn seasons, with diatoms contributing more in spring and diatoms and silicoflagellates both contributing the most in autumn. The seeding and growing periods of Patinopecten yessoensis in the adjoining waters off Zhangzi Island were synchronized with the annual dynamics of the phytoplankton that comprise its diet and phytoplankton settling fluxes. Diatom taxa such as Paralia sulcata, Thalassiosira spp., and Coscinodiscus spp. are all important food sources and grazing structure for scallops. By studying phytoplankton sedimentation with a high sampling frequency and clarifying the scallop diet taxa with settling fluxes, this research will provide a baseline database and references for sustainable aquaculture in the adjoining waters off Zhangzi Island, China.