海洋尖尾藻选择性摄食研究

异养甲藻是海洋浮游植物的主要摄食者，在海洋碳循环和营养再生过程中具有关键作用。本研究选择异养甲藻的代表物种—海洋尖尾藻为研究对象，通过喂食单种食物和混合食物，分析食物粒径和种类对异养甲藻摄食率、生长速率和细胞体积的影响。结果表明，海洋尖尾藻摄食的食物种类多样性高，隶属于穗鞭藻、定鞭藻、绿藻、硅藻和褐藻等门类的7种藻种均可被其摄食。海洋尖尾藻的摄食明显依赖于食物颗粒的体积，粒径显著影响了海洋尖尾藻的摄食率、生长率和细胞体积。能够被海洋尖尾藻摄食的浮游植物粒径范围在为2～128 μm，但是海洋尖尾藻对粒径为7.4～13 μm的土生杜氏藻、赤潮异弯藻和威氏海链藻的摄食率最高，并且摄食后生长速率和细胞体积最大。粒径为2～4.5 μm的抑食金球藻、赫氏颗石藻、球形棕囊藻单细胞和粒径为128 μm的布氏双尾藻显著降低了海洋尖尾藻的摄食率。当存在其他食物可供选择摄食时，海洋尖尾藻不再摄食布氏双尾藻。由于摄食行为的粒径选择性，异养甲藻可能对浮游植物的粒径结构和种群动态起到重要的调控作用。

Investigations on selective grazing in Oxyrrhis marina

As the main consumers of phytoplankton, heterotrophic dinoflagellates play key roles in carbon cycling and nutrient regeneration in marine ecosystem. Oxyrrhis marina was a model predator in laboratory-based feeding studies. To assess the effects of food type and particles size on grazing rate, growth rate and cell volume of heterotrophic dinoflagellate, O. marina were provided with either individual or combined prey. The results indicated that the O. marina has ability to consume 7 taxa, belonging to Chromalveolata, Haptophyta, Chlorophyta, Bacillariophyta and Ochrophyta, respectively. The feeding activity of O. marina strongly depends on the prey size, which influenced significantly the grazing rates, growth rates as well as cell volume. O. marina was ability to fed prey with size ranged from 2 μm to 128 μm. Prey with diameters ranged from 7.4 to 13 μm, e. g. Dunaliella tertiolecta, Heterosigma akashiwo and Thalassiosira weissflogii, resulted in the highest ingestion rates, growth rates and cell volume in O. marina. The Ingestion rate of O. marina on Aureococcus anophagefferens, Emiliania huxleyi, unicellular Phaeocystis globosa which diameters ranged from 2 to 4.5 μm, and D. brightwellii with diameters up to 128 μm was decreased significantly. Furthermore, D. brightwellii was not ingested by O. marina once alternative prey was available. Heterotrophic dinoflagellates could play a significant role in regulation of size spectrum and population dynamics of phytoplankton in marine ecosystem due to their size-selective feeding.