Relationships among the abundances of plastic debris in different size classes on beaches in South Korea

- Correlations among micro-(1-5 mm), meso-(5-25 mm), and macro-(>25 mm) plastic debris on beaches were tested.
- The abundance of microplastics was strongly correlated with the abundance of mesoplastics, but not macroplastics.
- Most of the microplastics were fragments of Styrofoam buoys from adjacent oyster culture facilities.
- Mesoplastic surveys could be used to identify microplastic hot spots.

Plastic debris on six beaches near the Nakdong River Estuary, South Korea, was sampled in May and September 2012 and classified into three size classes, large microplastics (1-5 mm), mesoplastics (5-25 mm), and macroplastics (>25 mm). The relationships among the abundances of the size classes were then examined. The abundances of each size category in May (before rainy season) and in September (after rainy season) were 8205 and 27,606 particles/m2 for large microplastics, 238 and 237 particles/m2 for mesoplastics, and 0.97 and 1.03 particles/m2 for macroplastics, respectively. Styrofoam was the most abundant item both in microplastic and mesoplastic debris, while intact plastics were most common in macroplastic debris. The abundances of meso- and micro-plastics were the most strongly correlated. There was a higher correlation between the abundances of macro- and meso-plastics than between macro- and micro-plastics.