东海低氧区浮游植物群落的昼夜垂直变化

摘要

根据2011年5月航次(春季)、8月航次(夏季)和11月航次(秋季)在东海低氧区共6个站位进行的昼夜连续观测所获浮游植物水样，用 Utermöhl 方法分析了浮游植物群落的昼夜垂直变化．春季共检出浮游植物99种，优势种为具齿原甲藻(Prorocentrum dentatum)、具槽帕拉藻(Paralia sulcata)和骨条藻(Skeletonema sp.)；夏季检出93种，优势种为劳氏角毛藻(Chaetoceros lauderi)、铁氏束毛藻(Trichodesmium thiebautii)、具槽帕拉藻；秋季检出78种，优势种为具槽帕拉藻、骨条藻和圆筛藻(Coscinodiscus sp.)．春季细胞丰度明显高于夏、秋季；春、夏季细胞丰度随水深增加逐渐降低，秋季细胞丰度分布较均匀；春、夏季上层水体浮游植物丰度昼夜变化较剧烈，下层水体相对平缓；秋季 D3站位表层和 J1站位底层细胞丰度昼夜变化较剧烈，其余水层细胞丰度昼夜波动不明显．春季 D2站位20,m 水层及夏季O11站位各水层优势种组成存在明显的昼夜变化，其余各水层浮游植物群集相对稳定．调查站位各水层间浮游植物群集结构差异明显．%Twenty-four hours observations on the diurnal vertical fluctuation of phytoplankton in the hypoxia area of the East China Sea were conducted from May to November in 2011. Water samples were analyzed by means of Utermöhl method. 99,species were identified and the phytoplankton dominant species were Prorocentrum dentatum,Paralia sulcata and Skeletonema sp. in spring. 93,species were identified and the phytoplankton dominant species were Chaetoceros lauderi, Trichodesmium thiebautii and Paralia sulcata in summer. 78 species were identified and the phytoplankton dominant species were Paralia sulcata,Skeletonema sp. and Coscinodiscus sp. in autumn. The phytoplankton cell abundance in spring was significantly higher than in summer and autumn. Vertically,cell abundance decreased slightly with depth from surface to bottom in spring and summer,which wasn’t obvious in autumn. In spring and summer,the diurnal fluctuation of cell abun-dance changed significantly in the upper water but gently in the lower water. At stations D3 and J1 in autumn,the diurnal fluctuation of cell abundance in various water levels changed gently except in the surface water of station D3 and the bottom water of station J1. The dominant species composition of phytoplankton showed significant diurnal variation only on the 20,m layer of station D2 in spring and all the water layers of station O11 in summer. During the investigation,differences of phytoplankton assemblges were discernible on different water layers.