Using aquatic insects as indicators of microplastic pollution in rice field ecosystems

Aquatic insects may be at risk due to microplastics, which are new pollutants in the water that are known to sink and accumulate in sediments. In this study, the concentration, type, size, and color of MPs in surface water, sediments, and aquatic insects were investigated in rice fields. The MP concentrations in surface water were 85.8 items/L. The MP concentrations in sediment were 0.43 items/g. In predatory aquatic insects, the microplastics discovered were 0.59±0.50–17.00±17.00 items/individual, in scrapers 2.45±2.66–9.00±9.00 items/individual, and in collector-gathering 2.45±2.66–25.00±25.99 items/individual. Fibers were the predominant type of MPs in surface water, sediment, and aquatic insects. The most common MP sizes were <100 µm in aquatic insects, >500 µm in sediment, and 200-250 µm in surface water. The dominant colors of detected MPs were blue in surface water and white/transparent in aquatic insects and in sediment. Polyethylene terephthalate (PET), polyvinyl acetate (PVAc), polypropylene glycol (PPG), polyethylene glycol (PEG), poly (acrylamide-co-acrylic acid) (poly (AM-co-AA), poly (vinyl methyl ether) (PVME), and bis(2-ethylhexyl) phthalate (DEHP) were the major polymer types of the selected particles. The results of this study showed the MP concentration in rice fields is relatively high in surface water and aquatic insect samples, although it is lower in sediment samples. This data may assist in extending our knowledge regarding MP pollution in freshwater systems and provides a baseline for future monitoring and assessment of MPs in rice fields.