Sources, distribution and fate of microfibres on the Great Barrier Reef, Australia.

Marine microdebris, in particular microplastics (plastics <5 mm), has become an issue of international concern due to its prevalence, persistence and potential adverse impacts on marine ecosystems. Informing source reduction based on ecological effects requires an understanding of the origin, distribution and characteristics of microdebris and the interactions with marine organisms. Here we show widespread contamination of the central Great Barrier Reef environment with microdebris, with microfibres comprising 86% of all items detected. Microdebris intake by coral reef fish was non-random, with chemical composition, shape and colour differing significantly from that detected in surface waters. Furthermore, the origin of microdebris contamination in surface waters is non-random with riverine discharge a likely source for microdebris detected at inshore, but not at offshore reef locations. Our findings demonstrate the complexities associated with determining marine microdebris exposure and fate, and assist in improving future ecological assessments and prioritizing source reduction.

Classification of marine microdebris: A review and case study on fish from the Great Barrier Reef, Australia.

Marine debris, and in particular plastic pollution, is ubiquitous throughout global marine environments. Here, we present a classification of marine microdebris (i.e. debris between 0.1 µm and <5 mm) tailored to represent synthetic, semi-synthetic and naturally-derived items. The specific aim of this classification is to introduce a level of consistency in the higher-level characterisation of marine microdebris, thereby improving the overall reporting on marine microdebris contamination. We first conducted an extensive literature review on the accumulation of ingested debris in fish to identify discrepancies in marine microdebris reporting as a basis for the new classification. The review reveals the diverse nature of ingested marine microdebris, including items that are non-plastic but often incorrectly reported on as microplastics. We then applied our classification to a case study on wild-caught juvenile coral trout, Plectropomus spp., from the Great Barrier Reef World Heritage Area, Australia. This first report on accumulation of ingested marine debris in commercial fish on the reef demonstrates a high frequency of occurrence and a prevalence of semi-synthetic and naturally-derived fibres. Based on our findings, we offer recommendations on potential improvements for the classification presented, ultimately contributing to a more realistic assessment of the ecological risks of marine microdebris.