Microplastic Abundance,Distribution And Composition In The Marine Environments And Organisms Of Xiangshan Bay

Microplastics generally refer to plastic particles with particle size less than 5 mm.As an emerging pollutant,it is widely present in marine environment,and can be ingested into living organisms,affecting the physiological activities of marine organisms.Understanding the pollution status of microplastics in the marine environment and organisms is fundmental for assessment of its ecological risks on orgamisms and threat to marine ecosystems.Xiangshan Bay is located on the coast of Zhejiang Province in southeastern China.It is a spawning ground,a nursery ground for many fisheries and an important marine aquaculture area.Affected by long-term fishery production and other human activities,the problem of microplastic pollution in Xiangshan Bay was serious.In the present study,the pollution status of microplastics in the surface water,sediments and organisms collected in Xiangshan Bay during the surveys of fishery resources in spring2019 was investigated and evaluated.Moreover,the transfer and biomagnification of microplastics in the food web were analyzed using trophodynamics methods.The research results were as follows:1.Microplastic pollution in the surface seawater of Xiangshan Bay.The average abundance of microplastics in the surface seawater was 0.17±0.18 items/m³,varying from 0.03-0.70 items/m³.A total of six shape types were identified,including foam(64.4%),fragment(11.7%),granule(8.0%),column(6.9%),film(5.0%)and fibers(4.0%)were detected,and five chemical component including polystyrene(PS,66.9%),polyethylene(PE,22.8%),polypropylene(PP,8.2%),rayon(RY,1.7%)and polyvinyl chloride(PVC,0.4%).The particle size of the microplastics ranged from 206 to 4940?m and averaged 1554±1103?m.The results showed that the microplastics abundance in the basin(southwest part)of the bay is apparently higher than in other part of the water.The plastics coming from concentrated aquaculture facilities and abundant river influx around the west part of the bay might make large contributions to the high microplastics abundance in the water of the basin of the bay.2.Microplastic pollution in the surface sediments of Xiangshan Bay.The average abundance of microplastics in the surface sediments was 139±87 items/kg(dry weight),ranging from 40±16 items/kg to 240±86 items/kg.The microplastics in the surface sediments were spatially evenly distributed in the bay.A total of six shape types of mrcroplastcs were identified,including fibers(65.4%),fragment(13.8%),granule(10.0%),film(5.9%),column(3.0%)and foam(1.9%).In terms of chemical composition,seven microplastics were detected:RY(63.1%),PP(23.6%),PE(5.5%),polyethylene terephthalate(PET,3.3%),polyamide(PA,2.2%),PS(1.9%)and polyvinyl alcohol(PVA,0.4%).The particle size of the microplastics ranged from 165to 4789?m,with an average of 1157±883?m.The microplastics in the surface sediments of the bay might mainly originate from coastal domestic sewage discharge around the bay.Compared to the microplastics in the surface seawater,the microplastics in the surface sediments of bay was more spatially evenly distributed.3.Microplastic pollution in common marine organisms and the transfer and bioaccumulation of microplastics in the marine food webs of Xiangshan Bay.The average abundance of microplastics in 23 marine organisms was 1.0±1.3items/individual,with the higest level in Konosirus punctatus(2.8±1.5 items/individual)and the lowest level in Gerres lucidus(0.2±0.4 items/individual).Three shape types of microplastics were observed:fibers(88.7%),fragment(10.1%)and granule(1.2%).In terms of chemical composition,twelve microplastics were detected.Of them,the most common microplastics were RY(67.6%)and PET(15.8%),followed by PP(7.5%),PVA(2.5%)and PE(2.1%).The particle size of the microplastics was between 105-4759?m,with an average particle of 1276±1019?m.The presence of microplastics in the marine organisms of bay is universal,which is to some extent correlated with the microplastics pollution in the environment.But plastics from aquaculture facilities might make less contributions to the microplastics in the organisms.The trophic relations of the 23 organisms were constructed using nitrogen stable isotope ratio(?¹⁵N),with the secondary consumer shrimp(Trachypenaeus curvirostris)as the baseline species(trophic level,TL=2.0;?¹⁵N=8.8±0.3‰).The?¹⁵N ratios of these organisms ranged from 7.7‰to 14.5‰and the TL ranged from 1.7 to 3.7.However,the abundance of the microplastics in the organisms tended to decrease with increasing TL with a low trophic magnification(TMF=0.17).This finding suggested that microplastics could be diluted in the marine food web of Xiangshan Bay.