Large amounts of plastics are leaked to oceans. In particular, microplastic (< 500 μm) is a pressing concern, because small organisms, such as zooplankton, may ingest small particles (< 50 μm) and hydrophobic toxins absorbed by particles. However, previous lab feeding experiments have applied unrealistic high concentration of microplastics. Moreover, little is known about microplastics ingested by zooplankton in natural systems. A reliable protocol to examine realistic concentrations of microplastics inside zooplankton is needed.
To achieve this, polystyrene beads with size of 9-25 um were fed to Pseudodiaptomus annandalei, with concentration ranging from 1ug/mL to 5 × 10⁻⁶ug/mL. For isolating microplastics, we used proteinase-K and sodium hypochlorite. Ingestion of beads was counted using fluorescent microscopy, and recovery rate was investigated using micro-RAMAN. As such, we aim to evaluate the extraction protocol and determine the detecting limitation. We then examined filter-feeding Paracalanidae and Calanidae copepodids (>300 um) in the southern East China Sea.