Microplastic ingestion by group and size of zooplankton in the Equatorial Pacific

Abstract

Since the discovery of microplastics in the Sargasso Sea in 1972, more plastics have entered our oceans. These gradually degrade into what we know as microplastics. If they get small enough, they can fall into the size range that zooplankton feed on. If consumed by zooplankton it can affect the health of the zooplankton themselves, but also lead to possible health complications in humans. The study looks at what factors such as groups of zooplankton, bead size, and zooplankton size have an impact on ingestion of microplastics. The samples were collected on the R/V Thompson G. Thompson along a transect from American Samoa north to 5°N, 167°W from December 28th to January 9th. Samples were collected with a 1-meter 209 μm zooplankton net and a 333 μm Manta Net. The zooplankton used in the study mainly consisted of ostracods and amphipods, with a mixture of copepods. The zooplankton samples were injected with fluorescent polystyrene bead sizes of 7.3 μm, 10.6 μm, 15.8 μm, and 20.6 μm and put in either a solution of filtered or unfiltered seawater. They were then viewed under a fluorescent microscope to view possible ingestion of the beads. The findings were that zooplankton consume plastics even in the presence of plankton, which indicates possibility for consumption in a non-lab setting. Another finding was that size is a major contributor to zooplankton bead ingestion. Larger zooplankton consumed a wider range of bead sizes compared to smaller zooplankton.