We investigated the effects of three sizes of polystyrene (PS) microbeads (0.05, 0.5, and 6-μm diameter) on the survival, development, and fecundity of the copepod Tigriopus japonicus using acute and chronic toxicity tests. T. japonicus ingested and egested all three sizes of PS beads used and exhibited no selective feeding when phytoplankton were added. The copepods (nauplius and adult females) survived all sizes of PS beads and the various concentrations tested in the acute toxicity test for 96 h. In the two-generation chronic toxicity test, 0.05-μm PS beads at a concentration greater than 12.5 μg/mL caused the mortality of nauplii and copepodites in the F0 generation and even triggered mortality at a concentration of 1.25 μg/mL in the next generation. In the 0.5-μm PS bead treatment, despite there being no significant effect on the F0 generation, the highest concentration (25 μg/mL) induced a significant decrease in survival compared with the control population in the F1 generation. The 6-μm PS beads did not affect the survival of T. japonicus over two generations. The 0.5- and 6-μm PS beads caused a significant decrease in fecundity at all concentrations. These results suggest that microplastics such as micro- or nanosized PS beads may have negative impacts on marine copepods.

Determining the exact abundance of microplastics on the sea surface can be susceptible to the sampling method used. The sea surface microlayer (SML) can accumulate light plastic particles, but this has not yet been sampled. The abundance of microplastics in the SML was evaluated off the southern coast of Korea. The SML sampling method was then compared to bulk surface water filtering, a hand net (50 μm mesh), and a Manta trawl net (330 μm mesh). The mean abundances were in the order of SML water > hand net > bulk water > Manta trawl net. Fourier transform infrared spectroscopy (FTIR) identified that alkyds and poly(acrylate/styrene) accounted for 81 and 11%, respectively, of the total polymer content of the SML samples. These polymers originated from paints and the fiber-reinforced plastic (FRP) matrix used on ships. Synthetic polymers from ship coatings should be considered to be a source of microplastics. Selecting a suitable sampling method is crucial for evaluating microplastic pollution.

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