Size Matters: The Variables Affecting Microplastic Ingestion Rates in Copepods

Abstract

Copepods, the most abundant zooplankton, are known to consume microplastics. My study aims to see what factors, copepods size; bead size; location of captured copepod, played the biggest role in their ingestion rate. On the R/V Thompson, copepods were collected along the southern edge of the East Pacific Gyre and fed different microplastic sizes: 10.6 μm, 10.9 μm, and 15.8 μm. The microplastics fed were fluorescent beads that glowed under a fluorescent light making ingestion visible through a microscope. At the University of Washington, the size of the copepods and the amount of beads ingestion were noted. I found that copepods larger than 300 μm had the highest rate of ingestion for mainly the 10.9 μm and 15.8 μm bead sizes. Smaller copepods the 10.9 μm bead sizes at high raters. My major finding was that the size of the copepods was the main factor in ingestion rates and size selectivity of the beads. Additionally, I found that there was an inverse relationship between ingestion rate and location; copepods consumed less if they were in an area of high plastic concentration. My findings agree with other studies that have proved microplastic ingestion in copepods and explains what can increase the amount of microplastics in a food web.