为了研究小型浮游动物对近岸浮游植物藻华的摄食调控作用,于2005年7月,应用“稀释法”并结合高效液相色谱(HPLC)光合色素分析技术,研究了台湾海峡船基围隔实验条件下浮游植物生长率及小型浮游动物摄食率的日变动。结果表明:由于营养盐添加的影响,迅速形成了以尖刺伪菱形藻(Pseudo-nitzschia pungens)为优势种的藻华,生物量(叶绿素a)从实验初始7月6日的1.45μg/dm3迅速增加到7月8日的29.80μg/dm^3,随后消退。镜检和光合色素分析的结果显示,实验期间一直以此硅藻占绝对优势。浮游植物的生长率在藻华峰值(7月8日)前保持了较高的生长速率(〉1.0/d)且大于小型浮游动物的摄食率;小型浮游动物的摄食率也逐渐增加,7月7日时达到0.86/d,显示有57%以上的浮游植物现存量被摄食。7月8日后,水华迅速消退,摄食率除13日外,均大于浮游植物的生长率。小型浮游动物主要由急游虫(Strombidiumspp.)、侠盗虫(Strobilidiumspp.)等无壳纤毛虫、异养甲藻-螺旋环沟藻(Gyrodinium spirale)及砂壳纤毛虫等组成,其对浮游植物的生长迅速作出了反应,各类群的丰度在水华峰值后的7月9日均几达最大值,水华后期(11日)大型的无壳纤毛虫达最大值。小型浮游动物的这种组成及变动特点是其保持较高摄食率及一定程度上控制和促进藻华消退的原因之一。
In order to study the role of microzooplnakton grazing on phytoplankton bloom, daily changes of the microzooplankton grazing rates and the growth rates of phytoplankton were investigated by using the dilution technique and HPLC pigment analysis in an mesocosm experiment conducted in Taiwan Strait, in July, 2005. The bloom of Pseudo-nitzschia pungens were fast excitated in the mesocosm due to nutrient addition, ChlorophyⅡ a concentration increased from 1.45 ug/dm^3 on July 6 to 29. 80 ug/dm^3 on July 8 and then declined. During the experiment, the bloom almost consisted of the diatoms according to light microscopy and HPLC pigment ananlysis. Before the peak of the bloom(on July 8 ), the growth rates of phytoplankton were consistently high(〉 1.0/d^-1) and more than the grazing rates of microzooplankton, the grazing rates of microzooplankton also increased gradually, up to 0.86/don July 7, indicating that greater than 57% of the standing stock of phytoplankton was removed per day. After July 8, chlorophyⅡ a concentration began to decline remarkably and meanwhile microzooplankton grazing rates were more than phytoplankton growth rates except July 13. Microzooplankton were consisted of aloricate ciliates(Strombidium spp. and Strobilidium spp. ), heterotrophic dinoflagellates(Gyrodinium spirale)and loricate ciliates, they showed a rapid response to the phytoplankton abundance after the nutrient enrichments and most of them almost increased to maximum on July 9 and two large-sized ciliates increased to maximum at post bloom (on July 11). This species composition of microzooplankton was one of the reasons of microzooplankton having high grazing rates and controlling and promoting diatom bloom decline.