Occurrence of microplastics within a freshwater aquaculture system in the Pacific Islands, Viti Levu, Fiji

Microplastics (MPs) have become frequent topics of research within Pacific Islands (PIs) in recent years; however, within PI freshwater aquaculture systems, MPs have not yet been quantified. As such this study is aimed at quantifying and characterizing the MP load from across a freshwater aquaculture system within Fiji. Water, sediment, and fish samples were collected from various stages between water source and drainage channels of an aquaculture facility in Navua, Fiji. MPs were extracted using established protocols and analyzed for abundance, form type, size, and polymer composition. Results show no significant difference in MP abundance between sampling sites for, water (average: 3.2 ± 1.14 MP/L), sediment (average: 2.3 ± 0.7 MP/100 g DW), and fish (average: 2.7 ± 1.4 MP/fish). Fibers were the most frequent form type in all three elements (average: 2.9 ± 0.2 MP/L in water, 2.1 ± 0.75 MP/100 g DW, 2.8 ± 0.14 MP/fish); however, the difference across sites was significant within water samples only. In water and sediments, smaller MPs (< 1.4 mm) were the most frequent comprising > 35% in all three elements; however, the difference was not significant between sites. Polymer analysis found that polypropylene, polyurethane, and nylon were the most abundant polymers, which coupled with observed form type and size characteristics suggest a common sources of MPs across sites.