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Microplastics in the ocean are threatening marine ecosystems. Although plastic contaminants are ubiquitous from rivers to polar oceans, their distribution is thought to be heterogeneous, implying that both spatial and temporal variability exist. Here, we elucidate the significant spatial and temporal (seasonal) variations in the quanti-qualitative characteristics of microplastics off the west coast of Kyushu, Japan in the East China Sea. Six surveys across nine stations (n = 54) were conducted over a 14-month period, and a total of 6131 plastic items were identified. The average microplastic abundance (items·m-3) and size (mm) ± S.D. were 0.49 ± 0.92 (n = 54), and 1.71 ± 0.93 (n = 6131), respectively. Differences between the highest and lowest abundances were 50-fold among monthly means (1.97 ± 1.49, n = 9; 0.04 ± 0.03, n = 9), and 550-fold across all net tows (5.50; 0.01). With respect to colour, polymer type, and shape, white and transparent (68.5%), polyethylene (80%) fragments (76.0%) were the dominant composition. There were statistically significant differences for each of the analytical microplastic parameters among survey months (p < 0.02). Our results provide baseline data, and lead to a more comprehensive understanding of the spatiotemporal characteristics of microplastic pollution.

Numerous recent studies have documented ingestion of microplastics (MPs) by many aquatic animals, yet an explanation for misfeeding by fish remains unexplained. Here we tested the hypothesis that biofilm (biofouling) on MP surfaces due to exposure in the aquatic environment facilitates misfeeding in fish. Spherical polystyrene (PS) was cultured for 0 to 22 weeks in a freshwater environment to grow biofilm on the MP. Goldfish were employed in a simple feeding experiment with and without provision of genuine food at ecologically relevant MP concentrations. The absorbance (ABS), which is a proxy for biofilm formation increased exponentially within three weeks of initiation and reached a plateau after approximately five weeks. Although fish did not swallow the MPs, 'capture' occurred when food pellets were in the vicinity and significantly increased in probability with exposure time. Duration of capture also increased significantly with increasing exposure. These results suggest that the drift of MPs in aquatic environments may facilitate fish misidentification of MPs as edible prey.

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