A global perspective on microplastic bioaccumulation in marine organisms

Microplastic (MP) contamination of marine ecosystems has been confirmed as an environmental issue of global concern. A growing number of monitoring surveys has extensively documented the occurrence and distribution of a wide array of MPs of different sizes, shapes, colours, and polymeric compositions in seawater, sediments, and marine organisms worldwide. The presence of MPs in marine organisms has been explored in many species belonging to different taxonomic groups collected in diverse geographical locations. These studies have revealed the ingestion and the bioaccumulation of MPs in organisms at each trophic level, confirming the ubiquity of MP contamination in marine ecosystems. This systematic review aimed at summarizing the results of the vast literature concerning the bioaccumulation of MPs in marine organisms to 1) shed light on potential differences in MP body burden among different taxonomic groups and 2) investigate the spatial and temporal variation of MP bioaccumulation at the global level. Our analyses showed that, independently of the geographic origin of the sample, the MP body burden significantly differed among trophic levels and/or taxonomic groups. Zooplankton showed the lowest MP levels, while the highest levels were observed in vertebrates other than fish (i.e. mammals, birds and reptiles). In contrast, no temporal or geographical differences in MP bioaccumulation were noted, independently of the taxonomic groups. These results confirmed that all marine organisms can ingest and accumulate MPs, but the large variability in body burden within and among the taxonomic groups precludes the opportunity to identify global patterns of contamination.