Method Development: Isolating Microplastics from Copepods in the Ala Wai Canal

Abstract

Microplastics are less than 5 mm in size (Zarfl & Matthies, 2010) and originate from the breakdown of larger plastics, cosmetic scrubbers, synthetic fibers, and air-blasting (Cole et al., 2011). Past studies have indicated a concern for bioaccumulation of microplastics in the food chain (Cole et al., 2011; Desforges et al., 2015; Zarfl & Matthies, 2010), but no published data testing this hypothesis has appeared in the literature. Therefore, the focus of this project was on developing methodologies to identify whether or not microplastics exist in the Ala Wai Canal and if they are consequently available and consumed by the canal’s copepods. This study analyzed the efficiency of methods to determine copepod ingestion of microplastics less than 1 mm in size. Results indicated that plankton tows were the most efficient method of collecting copepods and microplastics, that digestions were not very effective, and that a baseline understanding for the features and properties of microplastics less than 1 mm in size still requires testing in order to isolate microplastics from copepods in their natural environments. In conclusion, further baseline studies and knowledge needs to be acquired before it can be determined whether or not microplastics are biologically available to zooplankton, and if bioaccumulation occurs up the food chain.