Microplastic pollution and its relationship with the bacterial community in coastal sediments near Guangdong Province, South China

The ecological stress caused by microplastic (MP) pollution in marine environments has attracted global attention. However, few studies have investigated the relationship between MP pollution and the microbial community in natural sediments. This study was the first to systematically characterize MP pollution (i.e., its abundance, shape, size and color) and investigate its relationship with the bacterial community in coastal sediments from Guangdong, South China, by microscopic observation and Illumina sequencing. The results of this study indicated that the abundance of microplastics (MPs), which was 344 ± 24 items/kg in 33 coastal sediments from 11 sites from South China, represented a relatively high level of MP pollution. MPs with sizes of <0.5 m, 0.5-1.0 mm and 1-2 mm accounted for the highest proportion (75%) in the sediments. Fiber/film (82%) and white/blue (91%) were the dominant shapes and colors, respectively, in all MP samples. Furthermore, the abundances, three shapes (fiber, film and fragment), three sizes (<0.5 mm, 0.5-1.0 mm and 1-2 mm), and two colors (blue and white) of MPs displayed positive correlations with some potential pathogens, including Vibrio, Pseudomonas, Bacillus and Streptococcus, but exhibited negative correlations with an environmentally friendly bacterial genus, Sphingomonas (which degrades various hazardous organic compounds), indicating that MPs might increase the potential ecological risks of coastal sediments. Our results may help to elucidate the relationship between MP pollution and the microbial community in coastal sediments.