Large Accumulation of Micro-sized Synthetic Polymer Particles in the Sea Surface Microlayer

TLDR

Accurately assessing microplastic abundance on the sea surface is challenged by sampling methods, and the sea surface microlayer—known to accumulate light plastic particles—has not yet been sampled, underscoring the need for suitable sampling approaches. Microplastic abundance in the SML was measured off southern Korea and compared across SML sampling, bulk water filtering, a 50 μm hand net, and a 330 μm Manta trawl net. Mean abundances ranked SML water > hand net > bulk water > Manta trawl net; FTIR revealed alkyds and poly(acrylate/styrene) comprised 81 % and 11 % of SML polymers, originating from ship paints and FRP matrices, indicating ship coatings as a microplastic source.

Abstract

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.