Microplastic bioconcentration, bioaccumulation and biomagnification in a simple coral reef food web

Microplastics are considered a marine contaminant of emerging concern and to accurately assess the ecological risk of microplastics, it is critical to understand the levels of contamination and relationship between organisms and their surrounding envrionment. The aim of this study was to understand the ecological risk of microplastics on coral reef organisms by assessing taxa representing three trophic levels in the central Great Barrier Reef (GBR). This included zooplankton, benthic crustaceans and reef fish, as well as environmental matrices they inhabit (i.e., mid-column seawater and benthic sediment) from two mid-shelf reef locations (i.e., Davies and Backnumbers) in the central GBR. Contamination was assessed following rigorous protocols and analysed to determine levels of microplastics in each matrix. Microplastics were found in all matrices investigated, with similar polymers, sizes, colours and shapes across all trophic levels and environmental matrices. In contrast, contamination varied up the trophic level, and although microplastics were concentrating in organisms, there was no evidence for microplastics magnifying up the food web. However, given the heterogeneity of microplastics abundant within the marine environment, it is impossible to ignore trophic transfer as a prominant pathway of exposure from lower to higher trophic levels.