Plastic Deposition in Sediments of Moreton Bay, Australia: A Historical Perspective and Potential Future Projections

Since their discovery in the mid-20th century, the production and use of plastics has surged globally, resulting in large amounts of plastic waste. Some of this has landed in landfills, but a significant proportion has ended up in the ocean, contaminating marine ecosystems. However, the extent of marine plastic contamination is poorly understood. In this study, two sediment cores collected from the Central Bay of Moreton Bay, Australia, were analyzed for seven plastic polymers. The total concentration for ∑7 plastics was 8620 μg/g dw at the top of the core and decreased with core depth and sediment age, with no evidence of plastic at core depths aged earlier than 1975. Polyethylene was present at the highest concentrations (5680 μg/g dw) in the surface layer followed by polyvinyl chloride, polypropylene, and polyethylene terephthalate. Compared to factors influencing plastic abundance, the year, plastic production, and population were among the best predictors for plastic concentration in the core sediments. Projections on current findings suggest plastic concentrations in the Central Bay sediments could reach 2–4% of the sediment by 2050. An improved understanding of the types and quantities of plastic trapped in Moreton Bay will inform management to reduce plastic use and disposal to minimize future concentrations in the bay.