Microplastic (MP) particles are pollutants of global concern and are ubiquitously distributed in the ocean by physical and biological processes. It has been shown that zooplankton can ingest MP yet the interaction between ciliates and MP is still poorly understood. The discrimination and preferential uptake of MP rather than algal prey by ciliates was assessed in this study. The ciliate Sterkiella sp. was fed a diet that consisted of only Isochrysis galbana or a mixture of the same algae and similarly sized polyethylene beads in a 1:3 ratio. Significant, preferential MP grazing was observed in the Plastic-Algae treatment, which is the first reported evidence of proto-zooplankton preferentially ingesting MP over algal food. The mixed treatment contained fecal pellets with embedded MP. Preferential uptake of MP suggests that Sterkiella sp. is capable of ingesting and then “repackaging” MP that would otherwise be too small for larger taxa. This process would thus offer a mechanism for the reintroduction of MP into different compartments of the marine food web. As a consequence, it is necessary to account for small-sized MP (<5 μm) particles, that may have additional and yet unknown, impacts on marine food webs.

微塑料（MP）颗粒是全球关注的污染物，通过物理和生物过程无处不在地分布在海洋中。已经显示浮游动物可以摄取MP，但是纤毛虫和MP之间的相互作用仍然知之甚少。本研究评估了纤毛虫对MP而不是藻类猎物的歧视和优先吸收。纤毛Sterkiella sp。喂了一种仅由等鞭金藻组成的饮食或比例为1：3的相同藻类和尺寸相似的聚乙烯珠的混合物。在塑料-藻类处理中观察到大量的优先MP放牧，这是首次报道的原始浮游动物优先摄取MP而不是藻类食物的证据。混合处理包含粪便颗粒和嵌入式MP。优先摄取MP表明Sterkiella sp。能够摄取然后“重新包装” MP，否则MP对于较大的分类单元来说太小了。因此，该过程将提供用于将MP重新引入海洋食物网的不同隔室的机制。因此，有必要考虑小尺寸的MP（<5μm）颗粒，这些颗粒可能会对海洋食物网产生额外的影响，但尚未知。