Marine Microplastics: Abundance, Distribution, and Composition

This chapter summarises the spatial distribution and characteristics of microplastics in abiotic matrices reported worldwide in marine environments. The microplastic abundance in water was relatively high in the North Pacific Ocean, including Asian seas, except for the enclosed Mediterranean Sea. Among continents, Asian beaches showed the highest microplastic abundance. These global distributions derived from in situ measurements matched well with the results from modeled global predictions. The subtropical gyres accumulated more microplastics than other open ocean areas, and nearshore waters contained higher abundances than offshore waters. The abundance and mean particle size depended on the lower bound of the microplastic size sampled and analyzed, due to the increase in microplastic abundance according to decreasing size. Fibers, fragments, and foamed microplastics, considered as secondary microplastics, were the dominant forms of microplastics. Common polymer types included lightweight polymers and those produced in large amounts, such as polyethylene, polypropylene, and polystyrene.