Preferential grazing and repackaging of small polyethylene microplastic particles (≤ 5 μm) by the ciliate Sterkiella sp.

https://doi.org/10.1016/j.marenvres.2021.105260

Summary
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 mostly unknown. 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 only 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.

HEADERS DESCRIPTION
Treatment= Algae or Algae-Plastic
Type= Refers to the type of particle of one pg the above treatments: Algae or Plastic.
Rep= Replicateof each treatment type.
Time= Sampling time in 1 hour intervals, from T0 to T3.
Num= Number of particles per ml (algae or plastic).

https://doi.org/10.1016/j.marenvres.2021.105260

### 研究摘要
微塑料（Microplastic, MP）颗粒是全球备受关注的污染物，经由物理与生物过程在海洋中广泛分布。已有研究证实浮游动物可摄食微塑料，但纤毛虫与微塑料之间的相互作用仍大多未被探明。本研究针对纤毛虫对微塑料相较于藻类饵料的识别与选择性摄食展开了评估。实验选用纤毛虫*Sterkiella* sp.作为研究对象，分别投喂仅由等鞭金藻（*Isochrysis galbana*）组成的单一饵料，以及等鞭金藻与同等粒径聚乙烯微珠按1:3比例混合的复合饵料。在藻-塑料复合处理组中，观测到纤毛虫对微塑料存在显著的选择性摄食，这是首次报道原生浮游动物优先摄食微塑料而非藻类饵料的实证证据。复合处理组的粪便颗粒中可见嵌入的微塑料。对微塑料的选择性摄食表明，*Sterkiella* sp.能够摄食并“重新包装”那些对于更大体型类群而言尺寸过小的微塑料。该过程可为微塑料重新进入海洋食物网的不同圈层提供一种作用机制。因此，有必要关注粒径小于5 μm的小型微塑料颗粒——这类颗粒可能对海洋食物网造成额外且尚未探明的影响。

### 表头说明
- 处理组（Treatment）：分为单一藻类组与藻-塑料混合组
- 颗粒类型（Type）：对应上述处理组中的颗粒类型，分为藻类或塑料微珠
- 重复次数（Rep）：各处理组的重复样本数
- 采样时间（Time）：以1小时为间隔，涵盖T0至T3共4个时间点
- 颗粒浓度（Num）：每毫升水体中的颗粒数（藻类或塑料微珠）