Research On The Status Of Microplastics Pollution In Sediments And Oysters In The Bohai Sea And The Yellow Sea

Microplastics are defined as plastic particles with a longest size of less than 5 mm,which are widely distributed in marine environment and organisms.Due to its small size,it could be easily ingested by marine organisms and transferred through the food chain.At present,the pollution status and ecological risk of microplastics have become the focus of many researchers.In this study,the surface sediments and the indicator oysters were sampled in the Bohai Sea and the Yellow Sea.Additionally,cultured oysters were also sampled from coastal area of South China.The microplastics in sediments and oysters were separated by density separation,tissue digestion,and identified by microscopic Fourier transform infrared spectrometry.The abundance,type,size and spatial distribution of microplastics in the sediments were determined.The ingestion of microplastics in wild and farmed oysters were also investigated to evaluate the pollution status of microplastics,which could provide basic data for ecological risk assessment of microplastics in marine environment of China.1)Microplastic contamination in sediments of the Yellow Sea and Bohai SeaMicroplastic contamination was detected in the surface sediments collected from 72 different sites in the Yellow Sea and the Bohai Sea.The average abundance of sediments in the Bohai Sea,the North Yellow Sea and the South Yellow Sea was 171.80,123.60 and 72.00 per kilogram(dry weight)respectively.The abundances of microplastics in BB(Bohai Bay),CBS1(Bohai Central Sea 1)and CBS2(Bohai Central Sea 2)sections were significantly higher than those in other sea areas.The abovementioned sections are all located near the most developed region Beijing-TianjinHebei in China.Meanwhile,high abundance of microplastics was also detected in the LZ(Laizhou Bay)section,and the microplastics may mostly originate from rivers input such as the Yellow River and the Xiaoqing River.The PL(Penglai)and RC(Rongcheng)sections in the Yellow Sea were also enriched with microplastics.The PL sections are close to the Yantai Economic and Technological Development Zone where large amount of industrial effluent and sweage filled with microplastics may be discharged into the sea.RC section is one of the most important aquaculture areas for bivalves and kelp in China,and high-strength aquaculture activities could bring a lot of plastic pollution.Thus,the microplastic pollution in the Yellow Sea and the Bohai Sea may predominately originate from land-based sources.After analysis of the morphological features of the microplastics,they were classified into four types including pellet,fragement,film and fiber,of which fibers accounting for 93.33%.Most of the microplastics were white,with a proportion of 47.19%.The average size of microplastics was 854.88 ± 698.60 ?m,and the microplastics less than 1000 ?m accounting for 71.06%.Microscopic Fourier transform infrared spectrometer was used to identify the representative microplastics,and the chemical composition of microplastics was mainly rayon and polyethylene,with a proportion of 61.24% and 16.29% respectively.Our results showed that the microplatic pollution level of surface sediments in the Yellow Sea and the Bohai Sea were moderate compared with other studied.2)Microplastic ingestion characteristics in the Pacific oyster collected from the intertidal zone of the Bohai RimThe ingestion of microplastics in the Pacific oysters collected from the intertidal zone of 9 stations in the Bohai Rim was investigated,and 86.38% of the Pacific oyster samples ingested microplastics.The average abundance of microplastics was 2.03/individual or 0.89 ± 0.94/g tissue(wet weight).The shape of microplastics was classified into four types including fibers,fragments,films and pellets,and fiber(60.67%)was the main type of microplastics found in the Pacific oysters.The average particle size of microplastics was 814.65 ± 707.82 ?m with a proportion of microplastics less than 1000 ?m accounting for 67.01%.The chemical composition of microplastics was mainly rayon and polyethylene,with a proportion of 50.00% and 18.57% respectively.Above all,microplastic contaminations in the oysters were widespread in the intertidal zone of the Bohai Rim,and ingestion level was mainly affected by human activities.Our results suggested that the pollution level of microplastics in the Pacific oyster collected from the intertidal zone of the BohaiRimwas generally higher than the average level reported in other studies.3)Microplastic ingestion characteristics in cultured oysters collected from the coastal areas of the Bohai Sea,the Yellow Sea and South ChinaThe ingestion of microplastics in cultured oysters collected from 17 coastal areas of the Bohai Sea,the Yellow Sea and South China was investigated.It was found that microplastic ingestion was widely detected in cultured oysters from these araes with an ingestion proportion of 74.42%.The abundance of microplastics in cultured oysters was ranged from 1.05 to 9.08/individual or 0.11 to 2.35/g tissue with an average abundance of 2.93/individual or 0.62/g tissue.The microplastic contamination level in oysters collected from the Pearl River Delta region was significantly higher than those of other regions.The shape of microplastics was classified into four types including fibers,fragments,films and pellets,and the fiber accounting for 60.67%.The size range of microplastics in cultured oysters was 20.34-4807.22 ?m and the average particle size was 902.82 ± 782.99 ?m,among which the microplastics with sizes less than 500 ?m accounting for 38.57%.Rayon was identified as the main component of microplastics,accounting for 38.58% followed by polyethylene(22.05%).These results indicated that microplastic contamination was prevalent in cultured oysters collected from the coastal regions of the Bohai Sea,the Yellow Sea and South China,and the pollution level was a little higher than those of other stdudies.In conclusion,the microplastic pollution levels in the surface sediments of the Bohai Sea and the Yellow Sea,combined with the microplastic ingestion characteristics in the oysters collected from the intertidal zone of the Bohai Rim and the coastal areas of the Bohai Sea,the Yellow Sea and South China were investigated.The pollution level and spatial distribution pattern of microplastics in sediments and living organisms were also revealed in this study.In addition,this study filled the knowledge gap on the microplastic ingestion profiles in economically important species in China.This study is of great significance in understanding the distribution pattern and pollution level of microplastics in marine environment and the ingestion characteristics of microplastics in marine organisms in coastal area of China,which will provide information for ecological risk assessment of microplastic in marine environment.