Abstract:
The concern for plastic pollution in the ocean has evolved from its impact on aesthetics, and economic value to its effects on organisms, and now it's potential to contaminate seafood, posing a human health comcerns. Fish are an essential food source in New Zealand and have significant economic and customary value. There is very little data on microplastic ingestion in New Zealand fish, and no publications addressing microplastic effects on fish physiology and fitness. In response, I assessed the incidence of microplastic ingestion in New Zealand's most valuable wild fish species, hoki, investigating three key locations and properties of microplastics recovered. Baseline data was established, and ingestion was comparable to global rates, with 57 of 60 individuals found with incidence of plastic in the GI tract (95%). Fibres were the dominant contaminant (90.9%), and the average number of plastic per fish ranged from 4.25 (West Coast) to 6.9 (Cook Strait). The study found the highest ingestion in the Cook Strait but identified widespread contamination outside regions of the high human population, suggesting that microplastic contamination is a national issue. A 10-week tank experiment was then performed on snapper to assess the potential translocation of microplastics into the muscular tissue that is commonly consumed by humans. Microplastics were provided in feed at a low and high environmentally relevant concentration. Evidence of translocation of one or more particle was observed in 90% of high and PCP treatment fish, with an average number of 2.5 (high) and 1.9 (PCP) microplastics observed per fish. Excluding suspect particles this was reduced to 60% of fish in high and PCP treatments, with an average 1 microplastic per fish. The result could pose human health concerns as microplastics are a known source of chemical additives and environmental pollutants that can be toxic to humans. Physiological effects of microplastic ingestion on snapper were also investigated. Significant histopathological alterations to the GI tract observed in microplastic treatment fish, including inflammatory, vascular and structural changes. High treatment fish exhibited severe alterations (60%) that could compromise the absorption of nutrients and energy available for growth. Other observations included reduced growth and condition in the first half of the trial, high retention of microplastics in the GI tract, and hyperemia of the liver in microplastic treatment fish. In conclusion, the study provided baseline data on the widespread microplastic contamination in a valuable commercial fish species and identified the harmful effects ingestion could cause on fish including translocation into the flesh that humans eat.