Mismanaged Plastic Waste: Far Side of the Moon

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.

A meta-analysis of methodologies adopted by microplastic studies in China

China is the world's largest plastic producer and has been a focus of research on microplastic pollution. An increasing number of studies have documented plastics in the sediment, water and biota of China over the past decades. This systematic review compares different methodologies adopted by microplastic studies in China, including sampling equipment and methods; laboratory procedures in microplastic extraction and identification; and the characterisation and quantification of particles. In general, sediment samples were primarily collected with a grab sampler, while water samples were mostly taken from the surface using trawl nets. Different techniques, including density separation, chemical digestion, sieving and filtration, were applied to extract microplastics from the sample matrix. Visual sorting was an obligatory step that identifies microplastics by their morphological characteristics, such as size, shape and colour. Most studies in China reported the prevalence of irregular-shaped particles with sizes smaller than 1 mm. The chemical properties of microplastics were also assessed using infrared and Raman spectroscopy. Quantitative units commonly used for sediment, water and biota samples were "items per kg", "items per m³" and "items per individual", respectively. The inconsistencies in methods have marked the urgent warrant of a standardised methodology. It is believed that the findings of the present review can serve as an important waypoint contributing towards a more efficient and long-acting methodology for microplastic research, that can enable meaningful inter-study comparisons.