Mircoplastic ingestion in North Sea prey fish

Plastic pollution abounds in our oceans, resulting in a number of deleterious consequences for marine organisms. The transfer of microplastics (plastic particles measuring < 5 mm) between trophic levels through predator-prey interactions has become an important aspect of marine pollution research. This study aims to investigate microplastic ingestion in prey fish species, in order to provide further understanding of the potential for microplastic transfer between trophic levels. Sprat (Sprattus sprattus) and sandeel (Ammodytidae), together with a small number of other prey species, were analysed for ingested microplastics. The fish were collected from a number of locations in the North Sea. 291 sprat and 297 sandeels were analysed using both dissection and KOH dissolution to extract potential plastic. 12 and 5 microplastic particles were retrieved from the sprat and sandeels respectively. According to FT-IR analysis these were composed of a range of polymers including polyethylene (PE), polymethyl methacrylate (PMMA) and polypropylene (PP). Furthermore, sprat from both the winter and summer seasons were compared. Results show that summer sprat contained more plastic than the winter sprat, suggesting seasonal variation in microplastic ingestion by sprat in the North Sea. Microplastic characterisation by colleagues revealed that FT-IR is essential for determining whether a sample is ultimately plastic or not. One problem that occurs from analysing microplastic ingestion in a laboratory environment is the potential for atmospheric fallout of microfibres. The variation in the methods used by researchers to minimise or avoid air-borne contamination makes it difficult to compare microplastic results. This emphasises the need for studies to report fibrous and non-fibrous microplastics separately so as to allow proper comparison between studies. Although fibres were recovered from the samples during analysis, they were not taken into account in the ingestion results as their origin remains unclear. However, to determine the potential impact of air-borne fibres, the average number of fibres per fish, fibre colour and fibre contamination in the laboratory were all considered.